Georgios A. Sotiriou, ETH Zurich
Einar Kruis, University of Duisburg-Essen
Radenka Maric, Univ of Connecticut
Karsten Wegner, Wegner Consulting
NM6.1: Nanoparticle Formation and Structure
Monday PM, November 28, 2016
Hynes, Level 2, Room 209
9:30 AM - *NM6.1.01
Observation of Incipient Particle Formation by Tandem Differential Mobility Analysis-Mass Spectrometry (DMA-MS) in a Flame Aerosol Reactor (FLAR)
Pratim Biswas 1 , Yang Wang 1
1 Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering Washington University in St. Louis St. Louis United StatesShow Abstract
Flame aerosol reactor (FLAR) synthesis of nanoparticles is widely used to produce a range of nanomaterials. However, the incipient cluster formation by nucleation and vapor condensation is not well understood. This gap in knowledge of incipient particle formation is due to limitations of instruments in the measurement of sub 3 nm particles because of losses by diffusional deposition. Our group has overcome this limitation by use of a high resolution Differential Mobility Analyzer (DMA) and an Atmospheric Pressure Interface-Mass Spectrometer (APi-TOF) to observe incipient cluster formation during flame synthesis. By using these instruments in tandem, differential mobility analysis-mass spectrometry (DMA-MS) allowed the measurement of the size and mass of the incipient particles simultaneously, and the effective density of the sub 3 nm particles was estimated. It was found that the sub 3 nm clusters generated during the synthesis of SiO2 and TiO2 have effective densities of 1.42 g/cm3 and 1.75 g/cm3, respectively. These incipient clusters were less dense than the SiO2 and TiO2 bulk materials. The APi-TOF further provided the chemical composition of the detected clusters based on highly accurate mass and isotope distributions. Measurements in a blank flame detected a large number of sub 3 nm particles generated from chemical ionization reactions, and the negative ions were dominantly nitrate ions. The blank flame-generated ions played an important role during particle synthesis. The APi-TOF observed the appearance of nitrate ions in clusters containing silicon or titanium (such as Si2H6NO10- and TiN2O10-) species. As precursor feed rate increased, particles with larger mass and sizes were formed due to enhanced coagulation and vapor condensation. Results of latest advances in measurement of particle formation and growth in flame aerosol reactors will be presented.
10:00 AM - NM6.1.02
Atmospheric-Pressure Particle Mass Spectrometry for Inline Detection of Nanoparticles Synthesized in Spray-Flame Reactors
Samer Suleiman 1 , Sebastian Kluge 1 , Christof Schulz 1 2 , Hartmut Wiggers 1 2
1 Institute for Combustion and Gas Dynamics–Reactive Fluids University of Duisburg-Essen Duisburg Germany, 2 University of Duisburg-Essen Center for Nanointegration Duisburg-Essen Duisburg GermanyShow Abstract
Inline characterization of nanoparticle formation with particle mass spectrometry (PMS) is well established to investigate the evolution of particle size and particle size distribution during nanoparticle synthesis. It is commonly used in the gas-phase synthesis of nanoparticles to determine the influence of process conditions (temperature, precursor concentration, pressure) on the particle growth. The method is based on a molecular beam formed by a vacuum expansion through a nozzle/skimmer system. The vacuum conditions immediately suppress further reactions and particle growth. The system is equipped with a deflection unit with a Faraday cup detector to measure energy-filtered currents of charged particles and a quartz-crystal microbalance to detect the total particle loading of the molecular beam. Due to limitations in pressure drop in the conventional two-stage vacuum system and clogging of the sampling nozzle with particles, conventional PMS systems with an one skimmer/nozzle setup are limited to sampling from low-pressure (< 100 mbar) reactors. There are only few reports on molecular-beam mass spectrometry (MBMS) of particles from atmospheric-pressure systems, mostly used for the investigation of sooting flames .
In this study we present a newly developed PMS that can be operated at atmospheric pressure. It consists of a two nozzle/skimmer system integrating an additional pre-expansion chamber downstream the first nozzle operated at about 50 mbar. This allows sampling, dilution of particle concentration and freezing of the particles' properties by adding inert gases. After a very short residence time within this first chamber of about a few µs, the sample is transferred into a particle-laden molecular beam by expansion of the aerosol via the commonly used two-stage nozzle/skimmer system. The additional pre-expansion chamber enables operation of the PMS within a wide pressure range between 5 mbar and atmospheric pressure and the nanoparticle sampling rate can be tuned by adjusting the pressure in the pre-expansion chamber by adding dilution gases or reducing pumping power thus preventing clogging of the second nozzle. As the setup is mounted on a two-way positioning unit, it allows for spatially-resolved investigations of particle formation in gas-phase reactors. Results concerning the investigation of nanoparticles from sooting flames as well as from a spray-flame nanoparticle reactor, both operated at ambient pressure, will be discussed.
H.-H. Grotheer, K. Wolf, K. Hoffmann; Appl. Phys. B 104 ( 011) 367–383
10:15 AM - NM6.1.03
Coagulation of Agglomerates Consisting of Polydisperse Primary Particles
Maximilian Eggersdorfer 1 2 , Eirini Goudeli 2 , Sotiris Pratsinis 2
1 Novartis Pharma AG Basel Switzerland, 2 Department of Mechanical and Process Engineering Institute of Process Engineering Zurich SwitzerlandShow Abstract
Nanoparticles typically form irregular or fractal-like agglomerates of primary particles (PPs) by ballistic coagulation in volcanic plumes, and manufacture of carbon black or fumed silica as well as an array of nanoparticle compositions at low pressure (e.g. inert gas condensation). Even though the dynamics of coagulating spherical particles, such as self-preserving size distribution (SPSD) and coagulation rate are reasonably well-understood, there is significant uncertainty for fractal-like agglomerates. For the latter, coagulation rates have been proposed , their mobility  and SPSDs have been determined  and even the time needed to reach their asymptotic structure has been estimated . All these have been confined to agglomerates with monodisperse PPs. Realistic agglomerates, however, consist of polydisperse PPs. So little is known for the effect of constituent PP polydispersity on agglomerate structure and, most importantly, coagulation dynamics, which affect the environmental impact of agglomerates (climate forcing or visibility impairment by soot) or performance of gas sensors, catalysts and even biomaterials and nutritional products.
Here coagulation of nanoparticles of varying PP polydispersity (sg,PP = 1 – 3) in the absence of coalescence, sintering or surface growth is investigated by a discrete element method in the free molecular regime. This is an early stage of particle formation especially at high temperatures followed typically by rapid quenching to facilitate collection of particles and retention of their ramified structure as in manufacture of fumed SiO2, Ni or TiO2. As a result, particle dynamics at this stage frequently dominate the end product characteristics. The effect of PP polydispersity on agglomerate size, morphology (fractal dimension, Df, mass mobility exponent, Dfm, and their prefactors) as well as on the attainment of the well-known asymptotic fractal-like structure (Df = 1.91 and Dfm = 2.15) and SPSD is investigated. Increasing the polydispersity of the constituent PPs does not affect but only delays the attainment of the asymptotic Df, Dfm and SPSD of the resulting agglomerates. The crossover agglomerate size and critical number of PPs per agglomerate that mark the transition between Df = 3 and 1.91 scaling are obtained by various ways and increase with PP polydispersity. Only clusters larger than the crossover size should be considered for drawing conclusions on the formation mechanism as well as their structure. Furthermore, a simple modification in the collision kernel of monodisperse agglomerates is proposed that captures the evolution on the asymptotic collision frequency in the free molecular regime.
 Thajudeen T, Gopalakrishnan R, Hogan CJ Jr. (2012) Aerosol Sci. Technol. 46: 1174-1186.
 Sorensen CM (2011) Aerosol Sci. Technol. 45: 765-779.
 Vemury S, Pratsinis SE (1995) J. Aerosol Sci. 26: 175-185.
 Goudeli E, Eggersdorfer ML, Pratsinis SE (2015) Langmuir 31: 1320-1327.
10:30 AM - NM6.1.04
Scaling Laws for Packing Density of Fractal Aggregates
Pai Liu 1 , William Heinson 1 , Rajan Chakrabarty 1
1 Department of Energy, Environmental and Chemical Engineering Washington University in St. Louis St. Louis United StatesShow Abstract
Fractal aggregates in nature grow with a scaling dimensionality less than the spatial dimension. This results in their packing density (θf)–defined as actual volume occupied by solid subunits constituting an aggregate relative to total aggregate volume–decreasing with increasing size Rg/a (aggregate radius of gyration normalized by average radius of monomers (repeating subunits)). Fundamental questions remain regarding the scaling laws and physical mechanisms controlling the evolution of θf, especially after the onset of gelation. This is in part because of experimental challenges owing to the effects of gravity and thermal fluctuations on the formation and structural stability of aggregates in the large Rg/a limit. Here, we experimentally map the scaling of θf for aggregates–made of non-repulsive monomers–across five orders of magnitude of Rg/a. Our experiments reveal three successive growth regimes, namely diffusion-limited cluster aggregation (DLCA) of monomers, percolation of aggregates, and DLCA of percolates, with distinct cross-over points occurring at Rg/a ≈ 4 and 1×103. Corresponding to these regimes, we show θf to decrease in distinct power-law exponents of -1.3, -0.5, and -1.3, respectively. Our work, besides demonstrating the experimental realization of stable aggregation in very large Rg/a limit, redefines the currently held scaling law for θf of rigid aggregates, and has implications for synthesis of materials with superlative properties and accurate estimation of climate forcing by carbonaceous aerosols.
10:45 AM - NM6.1.05
Effective Density, Mobility and Primary Particle Size of Soot during Agglomeration and Surface Growth
Georgios Kelesidis 1 , Eirini Goudeli 1 , Sotiris Pratsinis 1
1 ETH Zürich Zürich SwitzerlandShow Abstract
Soot impact on health and environment strongly depends on its primary particle size and effective density. Scaling laws based on the projected agglomerate area exponent, Da, and prefactor, ka, have been used recently in tandem with mass-mobility measurements to obtain the size of the constituent primary particles of agglomerates and aggregates, as an alternative to off-line microscopy. The Da and ka of soot aggregates, however, depend on combustion sources and conditions.
Here, soot dynamics after inception are investigated by a Discrete Element Model (DEM) of agglomeration and surface growth during pyrolysis of acetylene. The initial acetylene molar fraction is varied to attain different final soot volume fractions. For high soot volume fractions, surface growth is dominant over coagulation at the early stages of soot formation and acetylene molecules react on the surface of soot primary particles increasing rapidly their mass and size. At these conditions, the soot mobility size distribution narrows down and its self-preserving geometric standard deviation, σg,m, decreases from 2.03 for point-contact agglomerates to 1.8. When acetylene molecules are consumed, soot aggregates continue to grow by coagulation in the absence of surface growth and σg,m passes through a minimum of 1.45 ± 0.05 in the transition regime, regardless of the employed soot volume fractions consistent with agglomerate dynamics.
The evolutions of Da and ka are quantified in terms of their normalized mobility size and relationships bridging the asymptotic Da and ka between small nascent and large mature soot aggregates are presented. The correlation among the number of primary particles, the mobility and the primary particle diameters based on the Da and ka derived here is in better agreement with mass-mobility measurements of soot aggregates than prior models for agglomeration of monodisperse and polydisperse primary particles. A relationship for the evolution of soot effective density as function of the normalized mobility size is derived and compared to measurements at different combustion conditions. The asymptotic Da and ka for mature soot aggregates are combined with a power law relationship to calculate the primary particle size of diesel and flame soot, achieving relative errors down to 0.2 and 1 %, respectively.
NM6.2: Nanoparticle Synthesis—Diagnostics and Structure
Monday PM, November 28, 2016
Hynes, Level 2, Room 209
11:30 AM - *NM6.2.01
Investigating Flame Synthesis of Nanomaterials with Laser-Based Diagnostics
Stephen Tse 1 , Gang Xiong 1
1 Rutgers University Piscataway United StatesShow Abstract
Laser-based diagnostics enable non-intrusive in situ characterization of the gas-phase synthesis flow field, as well as the as-formed nanomaterials themselves during flame synthesis, permitting fundamental understanding of the physical processes and growth mechanisms involved. Well-known techniques, such as laser-induced fluorescence (LIF) and Raman spectroscopy, can be utilized to characterize the gas-phase flow field (e.g. temperature, species concentrations). Moreover, novel developments of existing techniques have been recently used for in situ nanomaterials characterization during synthesis. Specifically, low-intensity phase-selective laser induced breakdown spectroscopy (PS-LIBS), for detection of the formation of nanoparticle phase, and in-situ Raman, for identification of nanoparticle crystallinity, are discussed.
Different from conventional LIBS, in PS-LIBS, the laser power used is much lower, with microplasmas created from breakdown of the nanoparticles but no gas breakdown. Thus, high selectivity is established between emissions from atoms emanating from nanoparticles versus atoms from gas-phase molecules (e.g. precursor species). For TiO2 nanoparticles, the emission intensity increases as the nanoparticles grow in the synthesis flow field, plateauing as the particles become larger than 6nm. PS-LIBS provides important tracking information of nanoparticle formation from gas-phase precursors to nanoparticles. Furthermore, when the wavelength of the laser is tuned to match the transition line of the excited atoms in the plasma, the signal intensity is greatly enhanced (over 100 times) by secondary resonant excitation from the same laser pulse, remarkably improving the detection threshold for measurements. The enhancement of the resonant excitation is highly sensitive to the excitation laser wavelength, with a narrow excitation spectral window, 14 to 22 pm (FWHM, full width at half maximum) for neutral atomic lines and 45 to 60 pm (FWHM) for the ionic lines. With further evolution of the nanomaterials after formation, in situ Raman spectroscopy is applied to characterize the crystallinity of the nanomaterials in the aerosol. For example, the crystalline transformation of titania from amorphous to anatase to rutile phases has been observed in situ in a flame. This technique serves as a sensitive and reliable way to characterize particle composition and crystallinity and to delineate the phase conversion of nanoparticles, allowing for better understanding of the governing growth and kinetic mechanisms.
12:00 PM - NM6.2.02
On-Line Monitoring of Nanoparticle Synthesis by Laser-Induced Breakdown Spectroscopy in Vacuum
Olivier Sublemontier 2 , Jessica Picard 2 , Jean-Baptiste Sirven 1
2 Commissariat à l'énergie Atomique et aux énergies Alternatives Gif Sur Yvette France, 1 Commissariat à l'énergie Atomique et aux énergies Alternatives Gif sur Yvette FranceShow Abstract
We propose a method for on-line monitoring of gas phase synthesis of nanoparticles. It is based on Laser-Induced Breakdown Spectroscopy (LIBS). LIBS is a method of chemical analysis that offers many advantages. It allows remote specific detection of most of the chemical elements in a sample and at very low concentrations. This technique was already used to probe the chemical composition stability of SiC nanoparticles during their production by laser pyrolysis. However, sampling stability control difficulties and interface problems between optical elements and particle flow are a drag to its use as an efficient method in continuous-wave mode on high-throughput production plants. Here we propose a new experimental setup for eliminating these difficulties by performing the laser-particle interaction in vacuum. A small part of the aerosol stream is sampled and driven to an aerodynamic lens system. The latter produces a dense and collimated beam of nanoparticles under vacuum from the atmospheric pressure aerosol flow. The laser-particle interaction takes place at 10-3 mbars. The photon signal from the plasma is collected by an UV-compatible optical fiber connected to a spectrograph. As the interaction takes place at low pressure, the photons are emitted only from particles. Unlike previous experiments, the background from interaction with the gaseous component is totally eliminated. Moreover, as the nanoparticle beam is highly collimated, the optical interfaces are not obstructed by particle deposition and the system can be kept running for hours. This method can also be adapted to wet chemical synthesis techniques or any particle samples in a stable suspension. In this case, the particle suspension is atomized to bring the sample in the aerosol form. The proof of concept is performed with a collimated beam of silicon nanoparticles. With a 20 kHz fiber-laser focused in order to have at least 10 GW/cm2 intensity on the particle beam, exploitable spectra are recorded at a repetition rate of less than one minute, allowing for continuous-wave or at constant time intervals in-process monitoring of particle chemical composition.
12:15 PM - NM6.2.03
Numerical Investigation of Silicon-Carbon Nanoparticle Synthesis in a Plasma Reactor
Johannes Sellmann 3 , Adrian Munzer 2 , Christof Schulz 2 1 , Hartmut Wiggers 2 1 , Irenaeus Wlokas 3 1 , Andreas Kempf 3 1
3 Institute for Combustion and Gas Dynamics-Fluid Dynamics University of Duisburg-Essen Duisburg Germany, 2 Institute for Combustion and Gas Dynamics-Reactive Fluids University of Duisburg-Essen Duisburg Germany, 1 Center for Nanointegration Duisburg-Essen University of Duisburg-Essen Duisburg GermanyShow Abstract
A microwave-plasma reactor for nanoparticle synthesis is designed, optimized and investigated by numerical modelling and simulation, which are validated against measured data.
Nanoparticle synthesis from the gas phase is a stable and scalable process for high purity particles with a narrow size distribution. In the case investigated, Si-C particles (for battery applications) are synthesized and coated in a microwave-plasma reactor. In contrast to other high-temperature processes (e.g. hot-wall or flame reactors), the particles from the plasma reactor are small, oxygen-free and non-agglomerated. Silane (SiH4) is injected with Argon and hydrogen as carrier gases at a low Reynolds number. In a first step, the gaseous precursor SiH4 is decomposed in the micro-wave plasma and Si nanoparticles are formed. In a second step, downstream of the plasma, the carbon shell is produced from Ethylen (C2H4), which is supplied through a set of coating nozzles, decomposed and homogeneously mixed with the dispersed Si nanoparticles, on which the carbon will be formed. In the complete process, predominantly spherical particles with a Si core and a C shell are formed.
To achieve effective mixing between Si nanoparticles and C2H4, numerical studies of the reactor have been performed and the mixing of two tracer streams with different temperatures (without plasma) was investigated in order to optimize the design of the coating nozzle. The resulting geometry was produced and used in experiment.
In the succeeding investigation of the synthesis process, the flow, the SiH4 decomposition and the particle dynamics were modelled to obtain insights into the gas-phase velocities, temperatures, and the resulting particle properties (volume, surface area and particle number concentration). The plasma was modeled as a distributed heat source, and as the reactor is not well accessible for direct measurements of the (wall) temperature, a conjugate heat-transfer model was employed. The evolution of the particles, described by the population balance equation, was solved by a monodisperse moment-model1 based on particle number-, area-, and volume concentration. The model was implemented in an Euler-Euler formulation for the gas- and particle phase, respectively. Nucleation was described by one-step chemistry from SiH4 to Si, assuming fast pyrolysis inside the plasma. Particle sizes are compared to experiments and show a plausible agreement.
The authors gratefully acknowledge the support by the German research foundation (DFG) in scope of the research group 2284 “Model-based scalable gas-phase synthesis of complex nanoparticles”.
1. F.E. Kruis, K.A. Kusters, S.E. Pratsinis, B. Scarlett, (1993). A simple model for the evolution of the characteristics of aggregate particles undergoing coagulation and sintering, Aerosol science and technology, 19 (1993) 514-526.
12:30 PM - NM6.2.04
From Atoms to Primary Particles to Agglomerates—Hierarchical Modeling of the Fractal Dimensions of Nanoparticles
Emmanuel Skountzos 1 2 , Vlasis Mavrantzas 3 1 2 , Sotiris Pratsinis 3
1 Chemical Engineering University of Patras Patras Greece, 2 ICEHT / FORTH Patras Greece, 3 Mechanical and Process Engineering ETH Zurich Zurich SwitzerlandShow Abstract
An outstanding issue in the field of nanoparticle science and technology is the prediction of the morphological properties of nanoparticle agglomerates in different media directly from the chemical constitution of the primary particles and their inter-atomic interactions with the medium atoms. Such a problem is not easy to address through a brute-force application of the atomistic molecular dynamics (MD) method because the longest times that can be simulated today even with the most powerful supercomputers and the use of thousands of graphics processing units (GPUs) with such a method are still on the order of a few hundreds of nanoseconds (up to a few microseconds in some cases).
However, if one is not interested in the dynamic properties of the system but only in its final morphological properties, one can resort to a non-dynamic method which is inherently free of any such long time restrictions. Such a method is the Metropolis Monte Carlo (MC) method of importance sampling, based on the generation of a Markov chain of states, i.e., a sequence of states in which the outcome of a trial state depends only on the state that immediately precedes it . The method has been used with exceptional success in simulating the thermodynamic and morphological properties (conformation and self-assembly) of many Soft Matter Physics systems.
We extend it here to the case of nanoparticle (NP) agglomeration using as test primary particles amorphous silica (SiO2) and fullerenes (C60). Our Monte Carlo algorithm is based on the design and efficient application of a set of powerful synthetic moves that help the systems ample configurational space and be driven quickly to the state of thermodynamic equilibrium. Four different such moves are applied here: a) NP displacement, b) NP rotation, c) agglomerate displacement, and d) agglomerate rotation. The simulations have been executed with two different force fields, a fully atomistic one [2, 3] and a coarse-grained one based on the potential of mean force between a pair of NPs.
Results will be presented from both types of simulations (which are typically completed within a few hours of CPU time) and will be compared with each other. They will also be compared with other simulation methods in the literature . We will see that the new method can provide accurate predictions of the fractal dimensions of the agglomerated nanoparticles in the gas phase starting solely from their chemical structure.
 Allen, M.P.; Tildesley, D.J. Computer Simulation of Liquids, Oxford Univ. Press (1987).
 Demiralp, E.; Cagin, T.; Goddard, W.A. Phys. Rev. Lett. 82, 1708−1711 (1999).
 Girifalco, L.A; Hodak, M.; Lee, R.S. Phys. Rev. B. 62, 13104−13110 (2000).
 Goudeli, E.; Eggersdorfer, M.L.; Pratsinis, S.E. Langmuir. 31, 1320−1327 (2015).
12:45 PM - NM6.2.05
Impact of Turbulence on the Size Distribution of Flame-Made Nanoparticles
Andreas Rittler 2 , Irenaeus Wlokas 2 , Andreas Kempf 2 1
2 Institute for Combustion and Gas Dynamics-Fluid Dynamics University of Duisburg-Essen Duisburg Germany, 1 Center for Nanointegration University Duisburg-Essen Duisburg GermanyShow Abstract
The influence of turbulence on the particle size distribution (PSD) of nanoparticles synthesized in spray flames is investigated by numerical experiments. Simulation results are presented, focusing on the size distribution (SD) for different turbulence levels and two different particle models.
Metal oxide nanoparticles are commonly produced in flame spray pyrolysis (FSP) processes, which enable an effective supply of the precursor into a hot environment, i.e. the reaction zone of the spray flame. The investigated FSP reactor, originally designed by Mädler et al., consists of a spray nozzle and three concentric inlets for the dispersion gas, a premixed pilot flame and a sheath gas. A combination of ethanol/hexamethyldisiloxane, methane/oxygen and pure oxygen are used as solvent/precursor, for the pilot flame and as sheath gas, respectively.
In the simulations, the spray droplets are modelled as Lagrangian particles and the gas-phase and the nanoparticles are described by Eulerian-specifications. The large eddy simulation technique and the flamelet generated manifold approach combined with artificial flame thickening are used as turbulence and combustion models, implemented in the in-house code PsiPhi. Accounting for nucleation and coagulation, the general dynamics equation of the particles is solved by a) a monodisperse moment model and b) a polydisperse sectional model. The moment model solves the transport equations for the particle number-, surface area and volume concentration, from which the particle properties are calculated. The sectional model solves transport equations for the particle number concentrations for several classes, representing different particle diameters. The unresolved turbulent fluxes are modelled by an eddy diffusivity approach.
The influence of turbulence on the PSD is discussed based on instantaneous and sample averaged results which are obtained from the monodisperse and polydisperse model. In contrast to the polydisperse sectional model, the SD predicted by the monodisperse moment model is only a result of turbulence. Furthermore, the studies highlight the differences of the particle properties and the particle size distributions predicted by the models and show the validity of the simple monodisperse model, for the investigated test case.
The authors gratefully acknowledge the financial support by the AiF (grant No. 18298N/3) and of the state NRW, as well as the Center for Computational Sciences and Simulation of the University Duisburg-Essen for the computational resources.
 L. Mädler, H. K. Kammler, R. Mueller, S. E. Pratsinis, J. Aerosol Sci. 33 369-389 (2002).
 A. Rittler, F. Proch, A. M. Kempf, Comb. Flame 162 1575-1598 (2015).
 F. E. Kruis, K. A. Kusters, S. E. Pratsinis, B. Scarlett, Aerosol Sci. Technol. 19 514-526 (1993).
 A. Prakash, A. P. Bapat, M. R. Zachariah, Aerosol Sci. Technol. 37 892-898 (2003).
 J. Loeffler, S. Das, S. C. Garrick, Aerosol Sci. Technol. 45 616-628 (2011).
Monday PM, November 28, 2016
Hynes, Level 2, Room 209
2:30 PM - NM6.3.01
Modeling of Particle Formation in Arc Discharges by Monte-Carlo Based Population Balance Modeling
Einar Kruis 1 , Gregor Kotalczyk 1 , Ivan Skenderovic 1
1 University Duisburg-Essen Duisburg GermanyShow Abstract
The scale-up of the production of metallic nanoparticles can be done efficiently by means of arc discharge in an inert carrier gas. The use of many single production units in parallel, which can be thoroughly optimized and tested on a lab scale for a given material, ensures that a highly effective scale-up of the synthesis process in terms of cost and energy consumption is possible. We demonstrated the integration of this technology in the aerotaxy production line for solar cells, direct deposition of nanoparticles on textiles, nanocomposites, deposition of nanoparticles within periodic arrays for photonics, higher heat transfer with nanoparticle dispersions and direct deposition of catalytic nanoparticles on membrane structures.
This work addresses the problems which appear when modeling the particle formation from an atomic vapour, formed by plasma evaporation from a melt as in the case of arc discharge. Here more than only the particle volume is relevant, such as agglomerate structure and particle charge. The modeling of distributed multiple particle properties can be efficiently done by means of population-balance modeling (PBM) in the framework of a Monte-Carlo simulation. It will be shown how the problems with large simulation times can be overcome when the simulations are being done with help of GPUs which allow parallelization of the algorithms, shown e.g. for coagulation (Wei and Kruis, Chem. Eng. Sci. 104, 451–459, 2013). The modeling of particle formation initiated by a physically induced nucleation controlled by the local temperature, is especially challenging due a strong variation of the Kelvin diameter which makes it almost impossible to apply conventional discrete-sectional PBM.
Inclusion of nucleation in a Monte-Carlo approach is challenging as the number of simulation particles which can be used is limited. The application of weighted simulation particles offers here a practical solution. Keeping the number of simulation particles constant requires strategies to discard other simulation particles while keeping the loss of information to a minimum, the newly developed low-weight merging technique shows here the best performance. An extensive validation of Monte-Carlo PBM to the coupled nucleation-coagulation problem will be shown, based on a comparison with a discrete-sectional model. Another challenge is the modeling of condensational growth, here the continuous variation of the Kelvin diameter, induced by e.g. temperature variation or monomer depletion, has to be taken into account. Care has to be taken that particles smaller than the Kelvin diameter effectively evaporate while large ones grow.
This work has been financially supported by the European Unions Seventh Framework Program (EU FP7) under Grant Agreement No. 280765 (BUONAPART-E) and the Deutsche Forschungsgemeinschaft in the frame of the priority program SPP 1679.
2:45 PM - NM6.3.02
Detailed Simulations of Transport and Nanoparticle Formation in a Hot-Wall Reactor
Patrick Wollny 1 , Johannes Sellmann 1 , Hans Orthner 2 , Hartmut Wiggers 2 3 , Irenaeus Wlokas 1 , Andreas Kempf 1 3
1 Institute for Combustion and Gas Dynamics–Fluid Dynamics University of Duisburg-Essen Duisburg Germany, 2 Institute for Combustion and Gas Dynamics–Reactive Fluids University of Duisburg, Essen Duisburg Germany, 3 Center for Nanointegration Duisburg-Essen University of Duisburg-Essen Duisburg GermanyShow Abstract
Detailed simulations of the transport phenomena and the of particle dynamics have been conducted for a hot wall reactor. Simulations are essential for the scaling of laboratory experiments to pilot and industrial plants, as the similarity parameters can rarely be preserved.
Two modeling frameworks for the representation of the dispersed particle phase (Euler-Lagrange and Euler-Euler) are presented. Both models are compared and validated against data measured in a laboratory scale hot-wall reactor producing iron nanoparticles by pyrolysis of iron pentacarbonyl in a nitrogen atmosphere.
A Monodisperse model1 for the population balance equation of the nanoparticles has been implemented into the open-source library OpenFOAM for both (Eulerian and Lagrangian) representations of the dispersed phase. Thermophoretic transport of the particle phase is described following Li and Wang2; particle diffusion is modeled as a diffusive flux or through a random walk. Concentrations of the gas phase are solved by transport equations, with a finite rate model describing chemical reactions. The Lagrangian and Eulerian implementations were individually tested against generic setups and later applied in simulations of a laboratory scale hot-wall reactor. The laminar flow field, simple reaction kinetics and the known wall temperature profile made the hot-wall reactor an ideal target for validation of the different models describing the physical effects and their impact on the major nanoparticle characteristics. The experimental setup allowed TEM probing and was additionally attached to a scanning mobility particle sizer system in parallel.
The comparison of the experimental data with both simulation approaches shows a good agreement in the mean particle size. Buoyancy effects show a crucial impact on the alignment and recirculation strength of the three dimensional flow field. Thermophoresis influences notably the particle size and distribution in the reactor. Applying diffusive random walk, the Lagrangian approach is capable to model a particle size distribution. Furthermore, rare big particles released from the recirculation zone of the reactor can be captured leading to a more realistic particle distribution. Therefore, it is pointed out that the Euler-Lagrange approach is more suitable for modelling nanoparticle formation in this context. Nevertheless, the Lagrangian model requires a higher computational effort, which makes the Euler-Euler approach attractive for parameter studies.
The work is supported by the European commission in the Horizon 2020 framework, project Nanodome (reference: 646121).
1 Kruis, F. Einar, et al. A simple model for the evolution of the characteristics of aggregate particles undergoing coagulation and sintering. Aerosol science and technology, 1993, 19. Jg., Nr. 4, S. 514-526.
2 LI, Zhigang; WANG, Hai. Thermophoretic force and velocity of nanoparticles in the free molecule regime. Physical Review E, 2004, 70. Jg., Nr. 2, S. 021205.
3:00 PM - NM6.3.03
The Crystal Structure and Surface Composition of Coalescing Ag-Au Nano-Alloys by Molecular Dynamics
Eirini Goudeli 1 , Sotiris Pratsinis 1
1 Mechanical and Process Engineering ETH Zürich Zürich SwitzerlandShow Abstract
Bimetallic nanoparticles have gained significant commercial interest because of their superior electronic, chemical and plasmonic properties compared to the monometallic counterparts making them excellent candidates for many biomedical, sensory or catalytic applications. For example, gold nanoparticles that are used extensively in catalysis exhibit reduced electron transfer on Au(111) surface, hindering the adsorption of O2. However, formation of gold-based bimetallic nanoparticles (e.g. with Ag) can enhance the affinity with O2 compared to pure gold nanocatalysts. Furthermore, Ag nanoparticles exhibit remarkable antibacterial properties but are highly cytotoxic rendering their use as therapeutic agents challenging. Alloyed Ag-Au is an interesting example in biomedicine with potential in theranostic applications since addition of Au in Ag nanoparticles improves biocompatibility without destroying the antibacterial activity of nano-silver (Sotiriou et al., 2014).
Here, the evolution of surface composition of free-standing but coalescing Ag-Au nanoparticles is investigated for different particle sizes and temperatures by atomistic molecular dynamics (MD) simulations. The MD method is validated by the attainment of the melting point of Ag-Au core-shell nanoparticles that increases with increasing particle size and follows closely the trend of the size-dependent melting temperature of pure Au (Goudeli et al., 2016) and Ag nanoparticles (Buesser et al., 2015). Silver atoms exhibit increased mobility upon coalescence and occupy gradually the surface of the segregated particle, consistent with experiments. When Ag nanoparticles are sufficiently smaller than Au ones, a patchy Ag layer forms at the Au particle surface. Sintering of equally-sized Ag and Au nanoparticles results in the formation of segregated nanoparticles with Ag-enriched surface, consistent with the literature. The initial particle morphology affects the particle crystallinity: the X-ray diffraction patterns of Ag-Au nanoparticles calculated during sintering, reveal that even though core-shell configurations and segregated structures exhibit the characteristic peaks of pure Ag and Au, the alloyed nanoparticles exhibit only the (111) and (200) peaks.
Buesser, B., and Pratsinis, S.E. (2015). Morphology and Crystallinity of Coalescing Nanosilver by Molecular Dynamics. J. Phys. Chem. C, 119, 10116-10122.
Goudeli, E., and Pratsinis, S.E. (2016). Crystallinity Dynamics of Gold Nanoparticles During Sintering or Coalescence. AIChE J, 62, 589-598.
Sotiriou G A, Etterlin G D, Spyrogianni A, Krumeich F, Leroux J-C, and Pratsinis S E. (2014). Plasmonic biocompatible silver–gold alloyed nanoparticles. Chem. Commun. 50: 13559-13562.
3:15 PM - NM6.3.04
Homogeneous Nucleation of Metal Nanoparticles—A Kinetic Monte Carlo Model to Study the Vapor Phase Synthesis of Al Nanoparticles
Seyyed Ali Davari 1 , Dibyendu Mukherjee 1
1 University of Tennessee Knoxville United StatesShow Abstract
A Gibbs free energy driven kinetic Monte Carlo model is developed for simulating vapor-phase homogeneous nucleation of metal nanoparticles (NPs). The model effectively accounts for monomer-cluster condensation, cluster-cluster collision, and cluster evaporation processes. The goal here is to develop a robust stochastic model that can capture the ensemble picture behind the rare event of metal NPs nucleating out of random collision events of clusters/monomers during typical high temperature gas-phase synthesis processes. The ability to capture the rarity of the event is made possible through an efficient pseudo sampling technique specifically developed to simulate the process without any stochastic bias. Specifically, we present results from the nucleation study of Aluminum nanoparticles evolving out of different initial temperatures, and cooling rates for the synthesis route. We validate the model by comparing our current KMC results with those from previously established phenomenological models developed within the framework of Gibbs’ free energy for cluster formation derived from Classical Nucleation Theory (CNT). The simulation results indicate the well-known entropic gain for clusters approaching the nucleation barrier, which culminates in the typical drastic entropic loss during first-order phase transitions due to NP formation. Furthermore, it is observed that the steady-state assumptions for nucleation rates of clusters are only valid for cluster sizes ≥10, below which the assumption fails to hold true as the clusters approach the onset of nucleation. The development of such elegant and high-fidelity KMC model with allow for easy incorporation of size-dependent surface tension (non-capillarity approximation), and non-isothermal nucleation into the model in future, thereby allowing the study of nucleation without any apriori assumptions.
NM6.4: Composite Materials and Functional Devices
Monday PM, November 28, 2016
Hynes, Level 2, Room 209
4:00 PM - *NM6.4.01
Mixed-Metal Oxide Nanopowder Used to Process Dense Single and Multi-Layer Flexible Thin (10-40 µm) Films Including Li+ Superionic Electrolytes
Richard Laine 1 , Eongyu Yi 1 , Catherine Haslam 1 , Clare Hyde 1
1 Materials Science and Engineering University of Michigan Ann Arbor United StatesShow Abstract
INTRODUCTION: Current fabrication methods used to produce thin ceramic films include traditional tape casting, spin casting of precursor solutions or vapor deposition methods. For the most part, tape casting relies on doctor blading slips made from ceramic powders with particle sizes > 0.5 µm. Consequently, sintering to full densities generally leads to final grain sizes of 2-5 µm. This in turn limits the final film thicknesses typically of 40-50 µm simply to avoid having films just a few grains thick, which would make them quite susceptible to brittle failure and impede handling for further processing. In contrast spin-coating sol-gel and ceramic precursors can often provide uniform and sometimes epitaxial films (depending on substrate) but typically at thicknesses of just 1-5 µm and often only by repeated coating because of the very significant volume changes that occur as precursors transform to a dense ceramics. Vapor deposition is often used to process very high quality thin films, especially in the electronics industry but is equipment intensive and again thicknesses beyond about 5 µm are sometimes quite tedious to process. Thus, there is considerable need for rapid, facile and low cost routes to 5-40 µm thick dense (or porous) ceramic films that offer superior mechanical properties but also versatility in the types of ceramic materials that can be made.
We present here, a simple method of making such films using wire-wound roller coating methods to cast thin polymer/ceramic nanopowder composites that can be made as single layers or laminated to make multiply ceramic laminates that on sintering provide dense single oxide thin films, ceramic composite thin films and ceramic/metal composite thin films. Several examples will be discussed including superionic lithium ion conducting electrolytes and cathode materials as well as some novel oxide materials.
MATERIALS AND METHODS: All nanopowders used in these studies were produced using liquid feed flame spray pyrolysis as discussed in detail elsewhere1-3. Thin films of superionic Li1.7Al0.3Ti1.7Si0.4P2.6O12 with 5 % excess lithium (LATSP+5) were produced. Thin Film Preparation: Suspensions were cast using a wire wound rod coater on mylar. Dried green films were peeled off the Mylar substrate, and cut to 2.5 2.5 cm. Sintering: First binder burnout was done at 400°C/air. LATSP was crystallized at 660 °C/5 °C/min. Sintering was done at 1200°, 1180°, or 1140 °C/1 h/60 ml/min air flow.
RESULTS AND DISCUSSION: Multiple film types were prepared using this processing approach. Numerous formats exist for making both single thin films and laminates as will be discussed in the presentation. In particular, it is possible to start with mixtures of nanopowders and sinter thin films where the final composite and chemical composition evolve during densification.
CONCLUSIONS: The use of nanopowders to process thin films and the use of wire wound roller coating methods provide access to a wide variety of novel thin films including those that offer particular utility for producing all solid state batteries.
1. E. Yi, J. Furgal, J. Azurdia, R. M. Laine,” Roll Your Own – Nano-Nanocomposite Capacitors,” J. Chem. Mater. A. 2014, 2 3766-3775.
2. N. J. Taylor, A. J. Pottebaum, V. Uz, R. M. Laine, “The bottom up approach is not always the best processing method. Dense α-Al2O3/NiAl2O4 composites,” Adv. Functional Mater. 2014, 24, 3392–3398.
3. E. Yi, W. Wang, S. Mohanty, J. Kieffer, R. Tamaki, R. M. Laine, “Materials that can replace liquid electrolytes in Li batteries: Superionic conductivities in Li1.7Al0.3Ti1.7Si0.4P2.6O12. Processing combustion synthesized nanopowders to free standing thin films,“ J. Power Sources 2014, 269 577-588.
4:30 PM - NM6.4.02
Synthesis and Characterization of La2Zr2O7 Nanocrystalline Coating by Reactive Spray Deposition Technology
Yang Wang 1 , Rishi Kumar 1 , Radenka Maric 1
1 University of Connecticut Storrs United StatesShow Abstract
In recent years, rare earth zirconates have been rigorously investigated due to their superior thermophysical properties, including low thermal conductivity, high thermal stability, and high melting point  and . These materials can effectively protect metal parts from extreme high temperature environment in gas turbines and diesel engines. Among numerous rare earth zirconates, pyrochlore-type La2Zr2O7 is considered as one of the most preferred candidate materials for thermal barrier coatings (TBCs) application. It has a high melting point of 2300 °C, a low thermal conductivity of 1.56 W m-1 K-1, and high phase stability  and . La2Zr2O7 has been synthesized via a number of methods, such as sol-gel, co-precipitation, solid state reaction, hydrothermal reaction, and solution plasma spray , , ,  and . In this study, pyrochlore-type La2Zr2O7 nanocrystalline coating is successfully synthesized and deposited via a novel flame based method, namely reactive spray deposition technology (RSDT). This alternative synthesis route of La2Zr2O7 is a single-step continuous process, providing the advantage of low cost, simplicity and scalability. A precursor solution of lanthanum acetylacetonate and zirconium acetylacetonate in organic solvents is feed through an atomization nozzle and the resulting vapor spray is ignited to generate a turbulent flame. The precursors rapidly decompose in the high temperature flame, followed by phase transition to vapor and homogeneous reactions to form oxides. X-ray diffraction (XRD) indicates that a single phase La2Zr2O7 with pyrochlore structure is obtained. The microstructure of as-prepared coating is investigated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanocrystalline La2Zr2O7 coating deposited by RSDT demonstrates a low thermal conductivity.
 R. Vassen, X. Cao, F. Tietz, D. Basu, and D. Stöver, 83 (2000), pp.2023-2028.
 Z.G. Liu, J.H. Ouyang, Y. Zhou, and X.L. Xia, Electrochim. Acta, 54 (2009), pp.3968-3971.
 S. Yugeswaran, A. Kobayashi, P.V. Ananthapadmanabhan, and L. Lusvarghi, Curr. Appl. Phys., 11 (2011), pp. 1394-1400.
D.R. Chen, and R.R. Xu, Mater. Res. Bull., 33 (1998), pp. 409-417.
 H.F. Chen, Y.F. Gao, Y. Liu, and H.J. Luo, J. Alloys Compd., 480 (2009), pp. 843-848.
 Y.P. Tong, J.W. Zhu, and L.D. Lu, J. Alloys Compd., 465 (2008), pp. 280-284.
 J. Wang, S.X. Bai, H. Zhang, and C.R. Zhang, J. Alloys Compd., 476(2008), pp. 89-91.
 X.Q. Ma, F. Wu, J. Roth, M. Gell, and H.E. Jordan, Surf. Coat. Technol., 201 (2006), pp. 4447-4452.
4:45 PM - NM6.4.03
Aerosol Synthesis of Ultra-Porous Nanoparticle Networks—A Functional Morphology for Wearable Optoelectronic Devices
Antonio Tricoli 1
1 Nanotechnology Research Laboratory, Research School of Engineering Australian National University Acton AustraliaShow Abstract
Nanostructured materials have the potential to significantly enhance the performance of several devices as recently demonstrated for solar cells, sensors and energy storage technologies. This has resulted in a rush toward novel applications ranging from flexible electronics to wearable nanogenerators. However, integration of nanomaterials in devices is challenging and their assembly in suboptimal morphologies may drastically limit the final performance. Here, we will present the fabrication of highly performing optoelectronic devices by integrated ultraporous nanoparticle networks. We will showcase the use of scalable and low cost flame-synthesis approaches for the wafer-level nanofabrication of tailored and well-reproducible 3D morphologies. The fundamental mechanisms controlling the gas-phase self-assembly of these nanostructures will be discussed with respect to current limitations and future opportunities. In particular, the rapid high-temperature gas-phase fabrication of highly performing photodetectors for quantitative monitoring of UV radiation will be presented . We will demonstrate a rapid approach for the synthesis of tunable band-selective UV photodetectors capable of detecting very low light intensities with record-high signal to noise ratios and very low power-consumptions. These results provide a robust set of guiding principles for the design of wearable electronic devices for personalized medicine and environmental monitoring.
 N. Nasiri, R. Bo, F. Wang, L. Fu, A. Tricoli, Ultraporous Electron-Depleted ZnO Nanoparticle Networks for Highly Sensitive Portable Visible-Blind UV Photodetectors, Adv. Mater., 27, 336-4343 (2015)
5:00 PM - NM6.4.04
Piezoelectric Nanogenerators with Flame-Made BaTiO
Gian Nutal Schaedli 1 , Robert Buechel 1 , Sotiris Pratsinis 1
1 Particle Technology Laboratory, Department of Mechanical and Process Engineering ETH Zurich Zurich SwitzerlandShow Abstract
Lead-free nanogenerators made with BaTiO3 are attractive for piezoelectric energy harvesting solutions in medical devices. Polycrystalline BaTiO3 nanoparticles of various sizes with average diameter from 20 to 50 nm were made by hydrogen-driven Flame Spray Pyrolysis (FSP) and embedded into thin poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films. In these nanoparticles the tetragonal phase and a high c/a lattice ratio were maintained, despite having small crystal sizes of only 10 nm. Piezoelectric nanogenerators were assembled using these nanocomposite films as well as films containing commercial, rather mono-crystalline particles of 64 and 278 nm in diameter. The time-averaged output voltage of nanogenerators containing as-prepared flame-made nanoparticles was 1.4 V, almost twice as that of commercial ones. That output was maintained stable for over 45’000 cycles with each cycle corresponding to a heartbeat of 60 bpm. Most likely, the high performance of these nanogenerators was facilitated by a higher degree of domain orientation upon poling these polycrystalline flame-made nanoparticles.
5:15 PM - NM6.4.05
Preparation of Nanoparticle-Based Composite Coatings
Olivier Sublemontier 1 , Youri Rousseau 1 , Yann Leconte 1
1 Laboratoire Edifice Nanometriques Commissariat à l'énergie Atomique et aux énergies Alternatives Gif sur Yvette FranceShow Abstract
We propose a method for the elaboration, in a single step and in a confined chamber, of composite coatings made of nanoparticles embedded in a matrix. The process combines a beam of nanoparticles with Physical Vapor Deposition. The association of the two techniques is made possible by routing nanoparticles by aerodynamic means to the substrate, either immediately after their synthesis in the gas phase, or from atomized colloidal suspensions. The simultaneous deposition of the particles and the matrix is performed on the same substrate. The process allows a virtually unlimited selection in the respective chemical compositions of nanoparticles and the matrix, and a moderate temperature of the substrate. Different source types of nanoparticles are possible. A laser-driven pyrolysis reactor can be used for the in-situ synthesis. Laser pyrolysis is an efficient method to synthesize various high purity nanopowders, oxides and non-oxides, in a gas phase bottom-up approach. An atomizer that produces an aerosol from colloidal suspensions of previously synthesized nanoparticles can alternatively be used. The particle stream is formed by means of an aerodynamic lens system. This system is currently used to produce a collimated beam of particles under vacuum for further gas phase characterization or for precision 3D micro printing. It allows for long-term stable and high transmission of particles in a wide range of size and density. We show that it is possible to get an angle-controlled divergent beam of nanoaerosols by optimizing the geometry of a classical lens. In this way, homogenous deposition of nanoparticles is performed on large areas. We demonstrate the adaptation if the technique with pressure environment required for running a classical magnetron sputtering device. The later is used for depositing the material constituting the matrix of the composite film. The deposition of a large variety of materials is conceivable by this means. The possibility to elaborate large and homogenous nanostructured films were investigated with different types of nanoaerosols with different sizes and densities. Numerous application domains are already considered for this kind of nanostructured coatings, including photovoltaic, photocatalysis, aesthetic coatings, hard covering, biomedical and self-healing films. The development of the process is carried out in the frame of the HYMALAYAN project funded by the French Research National Agency (ANR) under Grant No ANR-14-CE07-0036. It is open to new potential applications.
Georgios A. Sotiriou, ETH Zurich
Einar Kruis, University of Duisburg-Essen
Radenka Maric, Univ of Connecticut
Karsten Wegner, Wegner Consulting
NM6.5: Multiscale Structures and Sensors
Gianluigi De Falco
Tuesday AM, November 29, 2016
Hynes, Level 2, Room 209
9:30 AM - *NM6.5.01
Multidimensional Multiscale Assembly of Aerosols and Its Applications
Mansoo Choi 1 , Hoseop Choi 1 , Wooik Jung 1 , Yoon-ho Jung 1
1 Department of Mechanical and Aerospace Engineering Seoul National University Seoul Korea (the Republic of)Show Abstract
Well ordered multidimensional multiscale nano/microstructures could provide a platform for various novel nanodevices including sensors, electronic/magnetic devices and solar/fuel cells. In this presentation, we introduce an aerosol assembly technique for fabricating multidimensional multiscale nano/microstructures and their applications to 3D (three dimensional) gas sensors, 3D SERS(surface enhanced Raman spectroscopy) substrate, 3D nanostuctured solar cells, etc. Ion Assisted Aerosol Lithography (IAAL)1 or Electric-field Assisted Aerosol Lithography(EAAL) that we developed has been further developed to enable multi-furcation assembly of nanoparticles and even dynamic 3D printing of nanoparticles for manufacturing exotic 3D nanoparticle structures that could not be made by other existing methods. In addition, new ways of increasing the rate of charged nanoparticle generation will be also discussed for scaling-up aerosol assembly process.
 Kim, H., Kim. J., Yang, H., Suh, J., Kim, T., Han, B., Kim, S. and Choi, M. (2006) Nat. Nanotech. 1(2), 117-121.
10:00 AM - NM6.5.02
Lung Cancer Detection from Breath—Portable E-Nose for Selective Low-ppb Formaldehyde Sensing
Andreas Guentner 1 , Vitaly Koren 1 , Kiran Chikkadi 1 , Marco Righettoni 1 , Sotiris Pratsinis 1
1 ETH Zurich Zurich SwitzerlandShow Abstract
Lung cancer is one of the major health problems of modern society with predicted 1.8 million newly diagnosed cases per year (2012).1 The early detection of lung cancer could significantly improve medical therapy and thus reduce morbidity and mortality rates. Formaldehyde (FA) is a potential breath marker for lung cancer.2 It typically occurs below 100 parts-per-billion (ppb) together with other gases at higher levels (e.g. acetone, NH3, etc.) posing a sensitivity and selectivity challenge to current sensors. This can be overcome by combining broadly sensitive but differently selective sensors in an electronic noses (E-nose), a bio-inspired approach mimicking the human olfactory system3 with its array of receptors.4
Here, we present a highly sensitive, selective and compact E-nose for real-time quantification of FA at realistic conditions.5 This E-nose consists of four nanostructured and highly porous Pt-, Si-, Pd- and Ti-doped SnO2 sensing films directly deposited onto silicon wafer-based microsubstrates by flame spray pyrolysis (FSP). The constituent sensors offer stable responses and detection of FA down to 5 ppb (signal-to-noise ratio > 30) at breath-realistic 90% relative humidity. Each dopant induces different analyte selectivity enabling selective detection of FA in 2- and 4-analyte mixtures by multivariate linear regression. In simulated breath (FA with higher acetone, NH3 and ethanol concentrations), FA is detected with an average error ≤ 9 ppb using the present E-nose and overcoming selectivity issues of single sensors. That way, exhaled FA levels of lung cancer patients (~80 ppb) can be distinguished from healthy ones (~50 ppb).2 This E-nose can be readily incorporated into a portable breath analyzer6 that could facilitate easy and inexpensive screening of lung cancer patients.
1. J. Ferlay, I. Soerjomataram, R. Dikshit, S. Eser, C. Mathers, M. Rebelo, D. M. Parkin, D. Forman and F. Bray, Int. J. Cancer, 2015, 136, E359-E386.
2. P. Fuchs, C. Loeseken, J. K. Schubert and W. Miekisch, Int. J. Cancer, 2010, 126, 2663-2670.
3. K. Persaud and G. Dodd, Nature, 1982, 299, 352-355.
4. S. Firestein, Nature, 2001, 413, 211-218.
5. A. T. Güntner, V. Koren, K. Chikkadi, M. Righettoni and S. E. Pratsinis, ACS Sens., 2016, 1, 528-535.
6. M. Righettoni, A. Ragnoni, A. T. Güntner, C. Loccioni, S. E. Pratsinis and T. H. Risby, J. Breath Res., 2015, 9, 047101.
10:15 AM - NM6.5.03
Gas Phase Design and Synthesis of Mono-Metallic, Bi-Metallic and Tri-Metallic Nanoparticles for Smart Gas Sensing Applications
Mukhles Sowwan 1
1 Okinawa Institute of Science and Technology Onna-Son, Okinawa JapanShow Abstract
Heterogeneous gas-phase condensation is a promising method of producing hybrid multifunctional nanoparticles and alloys with tailored composition and microstructure but also intrinsically introduces greater complexity to the nucleation process and growth kinetics. Herein, I will talk about the synthesis and growth modeling of multi-metallic nanoparticles using gas-aggregated co-sputtering from different but neighboring elemental source targets. I will demonstrate that we are able to control the size, chemical composition, microstructure and shape of these nanoparticles. The nanoparticles are integrated directly into a smart gas sensing platform for mobile device.
1-Engineering high-performance Pd core-MgO porous shell nanocatalysts via heterogenous gas-phase synthesis .V. Singh, C. Cassidy, F. A.-Pedersen, J. -H. Kim, K. Aranishi, S. Kumar, C. Lal, C. Gspan, W. Grogger, and M. Sowwan Nanoscale 7 (2015) 13387-13392.
2-Heterogeneous Gas-phase Synthesis and Molecular Dynamics Modeling of Janus and Core-satellite Si-Ag Nanoparticles V. Singh, C. Cassidy, P. Grammatikopoulos, F. Djurabekova, K. Nordlund, and M. Sowwan J Phys Chem C 118 (2014) 13869-13875.
3-Steinhauer, S., V. Singh, C. Cassidy, C. Gspan, W. Grogger, M. Sowwan and A. Köck (2015). "Single CuO nanowires decorated with size-selected Pd nanoparticles for CO sensing in humid atmosphere." Nanotechnology 26(17): 175502.
10:30 AM - NM6.5.04
Monitored Deposition of Thin Flame-Made Gas Sensing Films
Christoph Blattmann 1 , Andreas Guentner 1 , Sotiris Pratsinis 1
1 ETH Zurich Zurich SwitzerlandShow Abstract
Chemoresistive gas sensors based on metal oxide nanoparticles are capable of analyte detection down to the ppb-level.1 Such sensors prepared in particular by direct deposition of flame-made nanoparticles exhibit outstanding performance because of, for example, the wide selection of high purity nanomaterials and their assembly into porous, crack-free films.2 Nevertheless, the existing fabrication technology is based on a three-step process in which nanoparticle deposition is frequently followed by in situ annealing and calcination. These later two steps compact and stabilize the nanoparticle film2 and ensure the measurability of a low-noise resistance-based response. The current method, furthermore, in adequately investigates the influence of deposited material amount on the sensor performance.
This work extends the employed technology by introducing a single-step flame deposition technique of nanoparticle-based gas sensors in which the film thickness is precisely tuned during synthesis. The as deposited SnO2 nanoparticle films attain a more compact morphology than conventionally obtained3 with this technology. Tuning the film morphology enables a direct correlation with the sensor performance. Furthermore, the in situ resistance,4 measured during deposition, gives direct insight into the stage of film formation: Upon forming an interconnected, percolating particle film the resistance drops and then oscillates around a constant value during prolonged deposition. As a consequence the least amount of deposited material, and therefore thinnest percolating nanoparticle film, is easily distinguished. Such thin and minimalistic gas sensors are compared to such prepared with superfluous amounts of deposited material in respect to their performance.
1. Righettoni M, Tricoli A, Gass S, Schmid A, Amann A, Pratsinis SE. Breath acetone monitoring by portable Si:WO3 gas sensors. Anal. Chim. Acta. 738(0), 69-75 (2012).
2. Tricoli A, Graf M, Mayer F, Kuhne S, Hierlemann A, Pratsinis SE. Micropatterning layers by flame aerosol deposition-annealing. Adv. Mater. 20(16), 3005-3010 (2008).
3. Mädler L, Roessler A, Pratsinis SE, Sahm T, Gurlo A, Barsan N, Weimar U. Direct formation of highly porous gas-sensing films by in-situ thermophoretic deposition of flame-made Pt/SnO2 nanoparticles. Sensor Actuat. B-Chem. 114(1), 283-295 (2006).
4. Blattmann CO, Pratsinis SE. In situ measurement of conductivity during nanocomposite film deposition. Appl. Surf. Sci. 371, 329-336 (2016).
10:45 AM - NM6.5.05
Flower-Like SiO 2@SnO 2 Nanostructures Assembled in Rapid Flame Process
Yanjie Hu 2 1
2 East China University of Science and Technology Shanghai China, 1 Washington University in St. Louis St.Louis United StatesShow Abstract
Flame aerosol reactors (FLAR), which are an industrially successful route to synthesize nanoparticles, provide an alternate choice for designing and fabricating nanostructures in a one-step and scalable process. However, due to the complex interactions among different process parameters, such as the precursor concentration, time-dependent flame temperature profile, chemical reaction rate, particle growth rate, coagulation rate, and sintering rate, it is truly hard to relate process conditions to the nanoparticles’ structures (except particle size) obtained from one-step FLARs. A depth understanding of flame process will be beneficial for the design of multifunctional nanostructures.
Our groups focus on nanostructures synthesized and scale-up via flame process for decades. By adjusting the temperature, concentration, and residence time distribution in the flame, various novel nanomaterials such as TiO2@SnO2, SnO2@TiO2, Ag@SiO2 core-shell nanostructures, Fe2O3||SiO2 Janus-like structures has been achieved via a flame process.
In this work, flower-like SiO2/SnO2 architectures composed of SiO2 core and SnO2 nanorods shell were successfully fabricated by a simple flame synthesis method. The presence of water in precursor and the completely immiscible nature of SiO2 and SiO2 in solid phase played a major role in the formation of the 3D architectures. After the SiO2 was removed by HF, the flower-like SnO2 with hollow core exhibited high sensitivity and rapid response and recovery toward ethanol gas. We demonstrated a scalable flame approach for the fabrication of 3D SiO2/SnO2 architecture which shows potential applications in many fields beside gas sensors and lithium batteries. Through the growth mechanism investigation, many other 3D heterostructures can be synthesized in flame by a similar route, which is now under our studying.
NM6.6: Controlled Synthesis of Nanoparticles and Applications
Tuesday PM, November 29, 2016
Hynes, Level 2, Room 209
11:30 AM - *NM6.6.01
Aerosol Synthesis of Nanomaterials for Hydrogen Generation and Purification Applications
Mark Swihart 1 , Parham Rohani 1 , Shailesh Konda 1
1 University at Buffalo Buffalo United StatesShow Abstract
This talk will introduce two projects involving high-temperature aerosol synthesis of nanoparticles for use in on-demand hydrogen generation and in hydrogen purification, respectively. In the area of hydrogen generation, we have recently shown that boron nanoparticles, in the presence of catalytic quantities of an alkali metal or metal hydride, can react with water at room temperature to generate hydrogen. This provides a very high energy density source of hydrogen for use in portable fuel cell applications. In our laboratory, we have used laser pyrolysis of diborane gas in hydrogen to produce these loosely agglomerated amorphous boron nanoparticles of 10 to 15 nm diameter. For commercial application, lower-cost production from less expensive precursors will be necessary. We are therefore currently exploring alternative production methods employing boron powder as a precursor. We will discuss both our current fundamental understanding of the particle production and hydrogen generation processes as well as the commercial potential of these materials for on-demand hydrogen generation. This talk will also introduce our work on production of palladium-silver-copper alloy nanoparticles by the flame-based high-temperature reducing jet process. These palladium alloy nanoparticles are being incorporated into polymer thin-film membranes for hydrogen-carbon dioxide separation. The nanoparticles provide high specificity of hydrogen transport through the nanocomposite (mixed-matrix) membranes. The nanoparticles are produced from aqueous precursors injected into the hot post-combustion gases of a fuel-rich hydrogen flame, within a converging-diverging nozzle. High-temperature aerosol production of these particles allows control of composition in ternary alloys that cannot be achieved by solution-phase methods. It also provides high purity materials without any organic ligands attached to their surface. However, further surface functionalization of the particles is required for incorporation into nanocomposite membranes and for controlling aggregation during membrane fabrication. In both of these projects, high-temperature aerosol synthesis is an enabling technology for producing nanomaterials that are inaccessible by other approaches.
12:00 PM - NM6.6.02
Routes to Nanoparticles by Chemical Vapor Synthesis with Optimized Particle Characteristics
Markus Winterer 1
1 University of Duisburg-Essen Duisburg GermanyShow Abstract
In contrast to materials properties particle characteristics such as size, specific surface area, degree of agglomeration or crystallinity can be directly controlled by the synthesis process and also determined experimentally without further processing. Although they only indirectly influence the (extrinsic) materials properties such as processibility or charge carrier mobility and life time, they are key parameters to optimize device performance in applications.
Titania is a model material for the Chemical Vapor Synthesis (CVS) process as synthesis is possible over a wide range of process parameters and particle characteristics are readily available by experimental and theoretical methods. Process parameters, especially the time-temperature-profile, control the nanoparticle characteristics and can be adjusted in CVS using a multizone induction furnace [1, 2].
We discuss a new method to find paths to optimized nanoparticle characteristics in CVS. As examples, we predict physically realistic, optimal time-temperature profiles for a
- minimized degree of agglomeration at a desired primary particle size and
- maximized degree of crystallinity at a desired specific surface area
integrating a simple model  describing particle formation and growth into a Monte Carlo optimization algorithm for the case of TiO2.
 R. Djenadic and M. Winterer, chapter 2, Chemical Vapor Synthesis of Nanocrystalline Oxides, in A. Lorke, M. Winterer, R. Schmechel, and C. Schulz, Nanoparticles from the Gas Phase, Springer 2012
 R. Djenadic and M. Winterer, Control of nanoparticle agglomeration through variation of the time-temperature-profile in chemical vapor synthesis, submitted 2016
 M. Winterer, Nanocrystalline Ceramics - Synthesis and Structure. Springer, Berlin 2002
12:15 PM - NM6.6.03
Atomically Dispersed Pd on TiO
2 for Solar-Photocatalytic NO
Kakeru Fujiwara 1 , Ulrich Mueller 2 , Sotiris Pratsinis 1
1 ETH Zurich Zurich Switzerland, 2 Swiss Federal Laboratories for Materials Science and Technology Duebendorf SwitzerlandShow Abstract
Palladium subnano-clusters (< 1 nm) on TiO2 nanoparticles are prepared in one step by flame aerosol technology.1 Under solar light irradiation, these materials remove NOx 4 or 9 times faster than commercial TiO2 (P25, Evonik) with or without photodeposited Pd on it.2 X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared fourier transform spectroscopy (DRFTS) reveal that such photodeposited Pd consists of metallic Pd along with several Pd oxidation states. In contrast, flame-made Pd subnano-clusters on TiO2 dominantly consist of an intermediate Pd oxidation state between metallic Pd and PdO. In that intermediate state, the Pd subnano-clusters are stable up to, at least, 600 oC for 2 hours in air. However, a fraction of them is reduced into relatively large (> 1 nm) metallic Pd nanoparticles by annealing in N2 at 400 oC for 2 hours, as elucidated by XPS and scanning transmission electron microscopy. The Pd subnano-clusters interact with oxygen defects on the TiO2 surface as shown by Raman spectroscopy, analogous to strong metal support interactions (SMSI) of nano-sized noble metals on TiO2.
1. Fujiwara, K.; Müller, U.; Pratsinis, S. E., Pd subnano-clusters on TiO2 for solar-light removal of NO. ACS Catal. 2016, 6 (3), 1887-1893.
2. Fujiwara, K.; Pratsinis, S. E., Atomically dispersed Pd on nanostructured TiO2 for NO removal by solar light. AIChE J (Special issue for ISCRE24) 2016, In review.
12:30 PM - NM6.6.04
Flame Synthesis of Titanium Dioxide Aerosol Gels with Tunable Primary Particle Size and Crystal Phase
Pai Liu 1 , Pratim Biswas 1 , Rajan Chakrabarty 1
1 Department of Energy, Environmental and Chemical Engineering Washington University in St. Louis St. Louis United StatesShow Abstract
Aerosol gels are a novel class of materials with potential to serve various energy and environmental applications. Synthesis of aerosol gel materials in gas-phase could be a cost-effective alternative to the conventional wet sol-gel process. Past studies have shown nanoparticle gelation occurring in a down-fired, buoyancy-opposed methane flame aerosol reactor (mFAR) as a viable technique for scalable production of gel materials. However, this gas-phase technique has yet to be proved capable of synthesizing gels with tunable material properties. In this talk, we present the results of our experiments specifically aimed at controlling the primary particle properties of gels using a mFAR. We were able to optimize the operating temperature conditions of the mFAR between 1250 and 590 °C by adjusting the oxidizer dilution ratio. At these two extreme temperature conditions, we delivered Titanium tetraisopropoxide (precursor) to the FAR for producing carbon-free titanium dioxide (TiO2) gel particles. Our results show approximately tenfold increase in the primary particle size of the TiO2 aerosol gel with the increase in the flame temperature. Pure rutlile and anatase phase TiO2 were formed at the high and low temperature conditions, respectively. Our work demonstrates that non-carbonaceous gel materials can be synthesized through a rapid single-step gas-phase process with high purity and tunable material properties.
12:45 PM - NM6.6.05
A Close Look at Flame Spray Synthesis of Titania
Keroles Riad 1 , Paula Wood-Adams 1 , Karsten Wegner 2
1 Laboratory for the Physics of Advanced Materials, Concordia University Montreal Canada, 2 Particle Technology Laboratory Swiss Federal Institute of Technology Zurich SwitzerlandShow Abstract
Titania is one of the bulk materials produced industrially by flame synthesis for pigment or photocatalytic applications. Therefore, TiCl4 is evaporated and introduced into premixed or diffusion flame reactors [1, 2]. An alternative production process is flame spray pyrolysis (FSP) that circumvents pre-evaporation of the precursor. Steep temperature gradients and very short particle growth times in the flame make it attractive for synthesis of nanoparticles e.g. for catalytic applications .
Here, this process is given a closer look. Detailed X-ray diffraction, transmission electron microscopy and Raman spectroscopy analyses of FSP product powders not only revealed an amorphous fraction but also monoclinic titania TiO2(B) in addition to the expected anatase and rutile phases. Monoclinic titania was first identified by Marchand et al.  in 1980 as a polymorph and has since then received much attention for photocatalysis  and lithium ion batteries  due to enhanced activity and high Li ion mobility, respectively.
The effect of reactor operating conditions as well as process scale-up on the titania phase composition and especially the monoclinic fraction is investigated here. Photocuring of epoxy is used as a test reaction to demonstrate enhanced performance of powders with monoclinic content. Such nanoparticles are compared to commercial titania P25 (Evonik) under UVA radiation. FSP-made titania with approximately 300 m2/g specific surface area exhibits the highest photocatalytic activity, almost 6 times higher than P25.
 Buxbaum G, Pfaff G (2005), Industrial inorganic pigments, 3rd ed., WileyVCH, Weinheim.
 Pratsinis S.E. (1998), Flame aerosol synthesis of ceramic powders, Prog. Energy Combust. Sci. 24, 197-219.
 Strobel R, Baiker A, Pratsinis SE (2006), Aerosol flame synthesis of catalysts. Adv. Powder Technol. 17 457-480.
 Marchand R, Brohan L, Tournoux M (1980), TiO2(B) a new form of titanium dioxide and the potassium octatitanate K2Ti8O17. Mater. Res. Bull. 15: 1129-1133.
 Yang D, Liu H, Zheng Z, Yuan Y, Zhao J, Waclawik E R, Ke X, Zhu H (2009), An efficient photocatalyst structure: TiO2(B) nanofibers with a shell of anatase nanocrystals. J. Am. Chem. Soc. 131: 17885-17893.
 Fehse M, Ventosa E (2015), Is TiO2(B) the future of titanium-based battery materials?, Chem. Plus Chem. 80, 785-795.
NM6.7: Energy and Catalysis
Tuesday PM, November 29, 2016
Hynes, Level 2, Room 209
2:30 PM - *NM6.7.01
Aerosol Based Nanotechnology for Sustainable
Mobility and Clean Energy Applications
A.G. Konstandopoulos 1 , S. Lorentzou 1 , K. Sakellariou 1 2 , E. Papaioannou 1 2 , G. Kastrinaki 1
1 Aerosol and Particle Technology Laboratory Thermi Greece, 2 Department of Chemical Engineering Aristotle University Thessaloniki GreeceShow Abstract
We review our progress in the area of Sustainable Mobility and Energy Production, that has been enabled exploiting advances in Aerosol Based Nanotechnology (ABN). Highly compact, multifunctional reactors are developed for applications in Automotive Emission Control and the technology is further extended and cross-fertilized in the area of Solar Thermochemical Reactors for the production of Carbon-Neutral Fuels using exclusively renewable/recyclable raw materials. Aerosol Based Synthesis and Deposition occurs in an integrated fashion in a dedicated pilot plant that combines aerosol spray generation, thermal treatment with a variety of sources (electric, burner and plasma) and deposition on structured substrates.
Catalytically coated ceramic monolithic reactors such as wall-flow Diesel Particulate Filters are the most complex component of today’s emission control systems as they need to incorporate different and often conflicting functionalities such as high soot nanoparticle filtration efficiency, low pressure drop behavior, direct catalytic soot oxidation activity, high oxidation activity for Carbon Monoxide, Hydrocarbons and Nitrogen Oxide, as well as ability to reduce Nitrogen Oxides. We show how ABN can address these challenges and demonstrate a multifunctional reactor for Diesel Emission Control that exhibits significantly better performance with respect to state of the art. An important spin-off activity from this research is the concept of a functionalized solar thermochemical reactor for the production of Carbon-Neutral Fuels. These solar fuels, can be synthesized from Hydrogen and Carbon Monoxide produced by solar thermochemical Water and Carbon Dioxide (CO2) splitting respectively, opening the door to the treatment of CO2 as a raw material, rather than as a waste to be disposed. The advent of Carbon-Neutral Solar Fuels along with efficient Multifunctional Reactors for emission control is a promising route for the transition to a sustainable and clean future with only minimal changes in the existing fuel infrastructure and automotive technology.
3:00 PM - NM6.7.02
Quantitative Analysis of the Deposited Nanoparticle Dose on Cell Cultures
Georgios Sotiriou 1
1 Karolinska Institutet Solna SwedenShow Abstract
The delivered nanoparticle dose to cells in vitro may depend on nanoparticle sedimentation rate. Here, the conditions under which optical absorption spectroscopy can be used to quantify the deposited nanoparticle dose in vitro are investigated. Nanoparticle cytotoxicity in both upright and inverted cell culture orientations is studied in presence and absence of serum. Dissolvable nanoparticles, such as ZnO, exhibit no difference in upright and inverted cultures due to dissolved Zn2+ ions that dominate cytotoxicity. Insoluble nanoparticles, however, exhibit different sedimentation rates and deposited doses that are linked to the observed cytotoxicity. The combined use of upright-inverted cell orientations and optical absorption spectroscopy can provide a simple experimental approach to interpret in vitro nano-biointeractions.
3:15 PM - NM6.7.03
Influence of Support Type on the Activity of Cobalt during Oxidative Dehydrogenation of Ethane
Rajesh Koirala 1 , Robert Buechel 1 , Sotiris Pratsinis 1 , Alfons Baiker 1
1 ETH Zurich Zurich SwitzerlandShow Abstract
Ethene is an important feedstock in chemical industry used for the synthesis of polyethylene, ethylene dichloride, ethylene oxide and monoethylene glycol. It is typically produced by steam cracking of naphtha and ethane which requires high temperatures leading to severe coke deposition on the reactor walls, thus requiring periodic cleaning . Catalytic oxidative dehydrogenation of ethane (ODHE) can serve as an alternative to this process offering lower reaction temperature (< 800 °C) and higher ethene selectivity (> 70%). Although the reaction can be performed at much lower temperatures (< 500 °C) using O2 as an oxidant, ethene selectivity is reduced due to the strong oxidizing nature of this oxidant . Therefore, the use of a milder oxidant (e.g. CO2) is preferred even though it requires higher reaction temperatures (> 600 °C). In this study, a wide range of single and mixed oxides supported cobalt catalysts were produced using a single step flame method and tested for the ODHE reaction . The performance of the catalysts was strongly affected by the support type which could be attributed to the different structural and chemical properties of the catalysts characterized by various methods. Among all the supported catalysts, SiO2-, ZrO2- and TiO2-ZrO2-supported cobalt catalysts showed similar ethene yield (~24%). However, in-depth analysis of these catalysts revealed that the performance of SiO2-supported catalysts is superior (ethene yield ~ 34%, under non-optimized conditions) compared to others. Through material characterization, it was revealed that cobalt is present in different oxidation states depending on the support type indicating occurrence of different reaction pathways. More specifically, a non-redox reaction pathway is expected in SiO2-supported catalyst where Co2+ is embedded in the SiO2 matrix, while a redox mechanism (over CoOx species) is proposed to be the dominant pathway over ZrO2- and TiO2-ZrO2-supported catalysts.
1. Ren, T., Patel, M., Blok, K. Energy, 31, 425 (2006).
2. Koirala, R., Buechel, B., Krumeich, F., Pratsinis, S.E., Baiker, A. ACS Catal.,5, 690 (2015).
3. Koirala, R., Buechel, B., Pratsinis, S.E., Baiker, A. In preparation (2016).
3:30 PM - NM6.7.04
Flame Spray Pyrolysis of Tin Oxide Based Pt Catalysts for PEM Fuel Cell Applications—Effect of Support Doping Elements and Pt Synthesis Procedure
Paul Dahl 1 , Luis Colmenares 1 , Alejandro Barnett 1 , Per Vullum 1 , Tommy Mokkelbost 1
1 SINTEF Trondheim NorwayShow Abstract
Nanostructured materials are gaining widespread use, which requires new approaches to powder synthesis, in particular with respect to increased production while maintaining proper safety procedures. Flame spray pyrolysis (FSP) is an excellent tool for pioneering development of complex nanomaterials for various applications and at the same time being a scalable process already being investigated by commercial powder producers . Such nanomaterials are of interest for electrodes in various energy applications e.g. PEM fuel cells where high conductivity, high surface area, well defined and sustainable pore structure/size distribution, stability and corrosion resistance are required material properties [2, 3].
In the present work flame spray pyrolysis (FSP) is applied to produce and investigate properties of tin-based oxide materials for use as cathode catalyst support in PEM fuel cells, offering high stability and corrosion resistance for this application as compared to carbon [4-6]. SnO2-based materials are already reported synthesized by FSP in the literature for the use in gas sensor applications [7-9]. In this work it is elaborated on using antimony and niobium as dopants (Sn1-xMxO2, x=0.00-0.15, M=Sb/Nb). Sb is introduced to enhance the electronic conductivity, required for the support material, while Nb is added with the intention of supressing the segregation of Sb to the surface, as observed when in contact with Pt-catalyst particles .
Pt-catalyst is applied to the SnO2-based support material through:
i) Well-established polyol-based Pt deposition route
ii) Single-step FSP synthesis
In addition to thorough physical characterization (XRD, BET, TEM) the materials are investigated with respect to electrical conductivity as well as oxygen reduction reaction (ORR). A general comparison of the two methods for preparing tin oxide supported Pt catalysts is given, in addition to the evaluation of observed effects of Sb and Nb-doping and the interaction of these elements with the Pt-catalyst particles.
The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement #325327 (SMARTCat project).
1. Teoh, W.Y., Nanoscale, 2010. 2(8): p. 1324-1347.
2. Sharma, S., J. Power Sources, 2012. 208: p. 96-119.
3. Rabis, A., Acs Catalysis, 2012. 2(5): p. 864-890.
4. Takasaki, F., J. Electrochem. Soc., 2011. 158(10): p. B1270-B1275.
5. Tsukatsune, T., Polymer Electrolyte Fuel Cells 10, Pts 1 and 2, 2013. 58(1): p. 1251-1257.
6. Kanda, K., ECS Electrochemistry Letters, 2014. 3(4): p. F15-F18.
7. Grossmann, K., Sensors and Actuators B-Chemical, 2011. 158(1): p. 388-392.
8. Madler, L., Sensors and Actuators B-Chemical, 2006. 114(1): p. 283-295.
9. Madler, L., J. Nanoparticle Research, 2006. 8(6): p. 783-796.
10. Fu, Q., Acs Applied Materials & Interfaces, 2015. 7(50): p. 27782-27795
3:45 PM - NM6.7.05
Scalable Production of Facet-Controlled Platinum Group Metal Nanoparticles at Gas-Solid Interface and the Application for Catalysis
Zhenmeng Peng 1 , Changlin Zhang 1 , Sang Youp Hwang 1 , Shirin Oliaee 1
1 University of Akron Akron United StatesShow Abstract
Catalytic property of platinum group metal (PGM) nanoparticles can be altered significantly by the nature of facets exposed. For example, Pt (100) plane excels in activity/selectivity compared to other planes in many reactions, including ring-opening hydrogenation of pyrroles, benzene hydrogenation, methanol oxidation (MOR), and electro-oxidation of ammonia (AOR). Pt-Ni (111) surface can exhibit exceptionally high activity towards oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells (PEMFCs). The findings have stimulated the exploration of new methods for preparing PGM catalysts with tailored particle morphology, because the usage of PGMs and thus the cost can be largely decreased. However, to date, there have been no feasible methods for cost-effective and mass production of the shaped PGM nanoparticle catalysts.
We realize scalable production of PGM nanoparticle catalysts with tailored particle morphology by developing a green and low manufacturing cost impregnation approach. A variety of shaped PGM nanoparticles, for instance cubic Pt/SiO2, cubic Pt/C, tetrahedral Pd/C, octahedral Pt-Ni/C, and cubic Pt-Cu/C, have been demonstrated for preparation. The experiments suggest that the formation of shaped PGM nanoparticles is resultant of employing both CO and H2 gases, wherein H2 aids transportation and reduction of the metal precursors on support and CO is responsible for the particle morphology formation. Several catalytic reactions, including preferential CO oxidation, hydrazine decomposition, ORR, and AOR, have been studied using the prepared catalysts. The octahedral Pt1.5Ni/C catalyst exhibits high ORR activities of 3.99 mA/cm2 Pt and 1.96 A/mg Pt at 0.90 V vs. RHE, which are about 20 and 10 times the values for commercial Pt/C specifically. The cubic Pt/C catalyst shows 1.44 mA/cm2 at 0.6 V vs. RHE in AOR, which is five times that of 0.30 mA/cm2 using commercial Pt/C.
NM6.8: Nanostructured Materials and Smart Coatings
Tuesday PM, November 29, 2016
Hynes, Level 2, Room 209
4:30 PM - *NM6.8.01
Improving the Characteristics of Liquid Flame Spray for Nanoparticle Synthesis and Functional Nanocoatings
Juha Harra 1 , Sonja Kujanpaeae 1 , Janne Haapanen 1 , Paxton Juuti 1 , Leo Hyvaerinen 1 , Mari Honkanen 1 , Jyrki Maekelae 1
1 Tampere University of Technology Tampere FinlandShow Abstract
Liquid Flame Spray (LFS) method utilizes hydrogen-oxygen flame to synthesize nanoparticles . Liquid precursor is sprayed into a turbulent flame, where the droplets evaporate, vapor decomposes and the reaction product re-condenses into product species. This process generates well-defined nanoparticles which can be collected as a nanopowder or sprayed on surface to fabricate large area functional coatings. In the process, the particle formation ideally follows the gas-to-particle aerosol route. However, due to residues of the sprayed droplets, a fraction of the original material may be lost to form larger particles via droplet-to-particle route. Thus, homogeneity of the product suffers. The residual particles are an issue, especially, with some inexpensive metal nitrate precursors. However, according to the recent literature, the amount of the residual particles can be substantially reduced by adding 2-ethylhexanoic acid (EHA) to the nitrate precursor solvents. Here, we utilize modern aerosol diagnostics to follow on-line the effect of adding EHA to the nitrate based precursor, to find minimum threshold concentration for EHA by which residuals can still be avoided. With e.g. aluminum nitrate, the residual mode dominated the mass size distribution of the particles produced without EHA. However, an EHA volume concentration of 5 % was enough to shift the mass practically entirely to the nanoparticle mode. In the presentation, the overall characteristics of the Liquid Flame Spray method for generating nanopowders and coatings will be presented. The consequences of successfully avoiding the residual particles for the benefit of various applications of the method, are further discussed.
5:00 PM - NM6.8.02
Flame Processing of Silicones to Produce Hierarchically Nanostructured Superhydrophobic Surfaces
Xinchun Tian 1 , Santosh Shaw 1 , Kara Lind 1 , Ludovico Cademartiri 1
1 Iowa State University Ames United StatesShow Abstract
We show that engineered silicone coatings become superhydrophobic after sufficient exposure to heat. The partial thermal degradation of the silicone by high temperatures (>500C, provided by a torch) creates porosity at the surface and beneath, and deposits hydrophobic nanostructured silicone “soot” on the surface. The coatings can be generated and regenerated (a 1.6-mm-thick silicone coating can be regenerated more than 20 times) in situ at a rate of >1m2 min-1 with a propane torch (much faster than self-healing methods), and strongly adhere to flexible, curved, and rough surfaces of diverse compositions. Straightforward and scalable process modifications yield superhydrophobic/superhydrophilic patterns and oleophobicity. The deep surface structuring caused by thermal processing creates a surface that remains porous after moderate wear. Subsequent regeneration of the surface yields a hierarchical texture that displays drastically increased wear resistance and tolerates foot traffic (>1,000 steps by a 75Kg person). By comparison, a state-of-the-art commercial solution (Neverwet®) is shown to be ineffective after 100 steps.
We will further show preliminary work that describes in more detail the process of silicone nanosoot formation that is at the heart of this processing strategy. The work will also establish the limits of the technique in terms of speed of processing and temperature.
This comprehensive strategy to address simultaneously the many challenges towards the implementation of superhydrophobic surfaces in large area outdoor applications, including easy in situ regeneration, resilience to weathering and wear, favorable environmental compatibility, and the possibility to turn the surfaces into SLIPS which avoid irreversible transitions to a Wenzel state and yields oleophobicity. The tunability of the chemical and physical properties of silicones by chemical modification or introduction of fillers, should provide avenues towards self-healing schemes which would make active surfaces such as these even more suitable for large scale outdoor applications.
References: Thermal Processing of Silicone Coatings for Green, Scalable, and Healable Superhydrophobic Surfaces
X. Tian, S. Shaw, K. R. Lind, Ludovico Cademartiri*
Advanced Materials, 2016, 19, 3677-3682
5:15 PM - NM6.8.03
Vapor-Phase Transport Deposited VO2 Nanobeams as Alternative RF Switch Components for Frequency Reconfigurable Patch Antenna Structures
Necmi Biyikli 1 , Kagan Topalli 1 , Serkan Kasirga 1 , Talha Masood Khan 1 , Bedri Cetiner 2 , Towfiq Asaduzzaman 2
1 Bilkent University Ankara Turkey, 2 Utah State University Logan United StatesShow Abstract
In this work we report an interdisciplinary effort which integrates high-temperature vapor-phase transport deposition of VO2 nanobeam materials with RF/wireless antenna structures towards the development of a prototype frequency-reconfigurable patch-antenna operating at wireless LAN frequencies. Individual VO2 nanobeams which exhibit metal-insulator transition (MIT) properties are used as active electrical switch components to tune the operation frequency of the microstrip aperture-coupled fed antenna.
VO2 nanobeams are grown by vapor phase transport deposition method using low pressure argon carrier gas and V2O5 powder placed in the center of a tube furnace in an alumina crucible at 800 °C. The nanobeams are grown on a c-cut sapphire substrate, elongated along the rutile c-axis. Low adhesion of nanobeams to sapphire substrate allows easy transfer between the metallic pixels of the patch antenna using a micromanipulator. After the placement of crystals, whole antenna structure is heated above the melting point of indium. Pre-drawn fine indium pins are used as a soldering agent to fix and ensure decent electrical contact between the VO2 nanobeams and metallic antenna pixels.
The MIT behavior of individual VO2 beams have been characterized by measuring the resistance between two adjacent metallic pixels. Resistance change due to metal insulator transition is very sharp as indium is soft enough for crystal to change its length upon the MIT while still keeping the electrical contact with the contact pads. Phase transition occurs at a slightly elevated temperature of around 76 °C which is most likely due to the relatively poor and un-optimized thermal contact between the heating stage and the antenna structure. Nevertheless, a resistance change over 3 orders of magnitude has been obtained from individual VO2 nanobeam integrated antenna pixel pair.
Electromagnetic simulations of the fabricated reconfigurable antenna structure has been carried out using full-wave analysis method. By using the experimentally verified resistance values for metallic and insulator states of VO2 nanobeams, the simulations show a promising frequency-tuning ability between 2.35 and 5.4 GHz.
This study shows that high-temperature gas-phase deposited VO2 nanobeams can be used as critical enabling components for smart RF-antenna architectures which might provide a viable technology for next-generation smart wireless communication systems.
5:30 PM - NM6.8.04
Electrical Switching in Semiconductor-Metal Self-Assembled VO2 Disordered Metamaterial Coatings
Channam Venkat Sunil Kumar 1 2 , Francis Maury 2 , Naoufal Bahlawane 1
1 Luxembourg Institute of Science and Technology Belvaux Luxembourg, 2 CIRIMAT University Toulouse Toulouse FranceShow Abstract
Vanadium oxide (VO2) films grown by gas phase process such as MOCVD offer considerable advantages in terms of ease in scalability, simplicity, rate of growth and cost effectiveness when compared to other synthesis techniques like PVD, Sputtering or MBE. However precise control over the phase of vanadium oxide films is challenging as Vanadium forms many stable oxides like VO2, V2O5, V2O3, and V6O13.
Wafer scale synthesis of high quality VO2 coatings was attained taking advantage of a one-pot, three step process comprising (a) chemical vapour deposition, (b) an oxidative sintering, and then (c) a vacuum reduction of the films. This is achieved by utilizing a thermodynamically favourable pathway. During the post deposition oxidation, nano crystalline VO2 is first oxidised to V2O5. Pure high quality VO2 with large grain size is later obtained by reducing V2O5 to VO2 (M).
Structural and optical phase transitions were studied by temperature dependent X-Ray diffraction and IR reflectivity spectroscopy. The semiconductor-metal transition occurs at 67°C from the pure monoclinic, M1, phase to yield a pure rutile (R) phase with an abrupt electrical resistivity change of more than three orders of magnitude. The cyclic transition reveals a narrow hysteresis with a width of 3K. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compressing monoclinic (M1 and M2) and rutile (R) domains, that occur at the transition temperature region.
An electric switch based on VO2 operating in this transition region is demonstrated. Short heating or cooling pulses induce the coalescence/confinement of the metallic domains within the otherwise stable metamaterial. The degree of coalescence was thermally triggered with high precision to provide a reliable electrical switching with adjustable amplitude and profile.
Georgios A. Sotiriou, ETH Zurich
Einar Kruis, University of Duisburg-Essen
Radenka Maric, Univ of Connecticut
Karsten Wegner, Wegner Consulting
NM6.9: Carbon-Related Nanomaterials
Wednesday AM, November 30, 2016
Hynes, Level 2, Room 209
9:30 AM - *NM6.9.01
Tailored Synthesis of Fullerenes, Single-Walled Carbon Nanotubes, Their Derivatives and Dispersions for Energy and Electronic Applications
Henning Richter 1 , Katherine Barton 1 , Hossein Ghiassi 1 , Edward Jackson 1 , Thomas Lada 1 , Ramesh Sivarajan 1 , Colleen Treacy 1 , Viktor Vejins 1
1 Nano-C Inc Westwood United StatesShow Abstract
Fullerenes, particularly C60 and C70, single-walled carbon nanotubes (SWCNT), their chemical derivatives and dispersions are important building blocks for many nanoscale devices such as organic photovoltaics and photodetectors, non-volatile memory and optical, chemical or biological sensors.
As the availability at industrial scale of high quality fullerenes and SWCNT with consistent characteristics is essential for the emergence of commercial applications, suitable manufacturing technology needed to be developed. Being exothermic, scalable and allowing for the selective formation of either fullerenes or SWCNT, premixed hydrocarbon combustion is a particularly appealing approach and has been developed at Nano-C to a mature industrial process. While fuel-rich combustion of aromatic hydrocarbons at reduced pressure enables the targeted synthesis of fullerenes, low-pressure combustion below the sooting threshold of aliphatic and other hydrocarbons in presence of a continuously supplied catalyst precursor results in the efficient formation of SWCNT. Correlations between reactor design, operating parameters such as pressure, fuel-to-oxygen ratio or residence time and characteristics of the generated fullerenes or SWCNT determined by means of a range of analytical techniques will be discussed. Scale-up strategies allowing to meet the quickly increasing demand will be presented.
An important aspect of the manufacturing of materials for which applications are still under development, such as fullerenes and SWCNT, consists in their processing after synthesis and collection in order to allow for optimized performance in targeted devices. In most cases, the identification of the desired characteristics is addressed in the context of close interaction between materials manufacturers and device developers. The extraction and purification of fullerenes will be shown and the use of chemical functionalization for the achievement of solubility in specific solvents presented. The development of fullerene derivatives with electronic structures suitable for their optimized use as electron acceptor phase in the active layer of organic photovoltaic applications and photodetectors in combination with selected electron donor materials will be discussed.
SWCNT applications require in nearly all cases control of their length, diameter distribution and amorphous carbon content during manufacturing. Advances made in this regard along with purification procedures allowing for the efficient removal of residual catalyst metals and amorphous carbon while keeping nearly defect-free SWCNT will be presented. Enabling applications further necessitates the dispersion of purified SWCNT in acceptable solvent systems that are free of surfactants. Application of combustion-synthesized SWCNT in a wide range of areas such as non-volatile memory, transparent conductors, fuel cells, printed electronics and sensors will be highlighted.
10:00 AM - NM6.9.02
A Novel Spray Process Integrates the Features of Spray Pyrolysis and Drying for Battery Material Generation
Yujia Liang 1 , Huajun Tian 1 3 , Joseph Repac 1 , Sz-Chian Liou 2 , Weiqiang Han 3 , Chunsheng Wang 1 , Sheryl Ehrman 1
1 Chemical and Biomolecular Engineering University of Maryland College Park United States, 3 Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo China, 2 Maryland Nanocenter University of Maryland College Park United StatesShow Abstract
Current application of graphite as the anode of Li-ion battery is limited by its low theoretical capacity (372 mAh).1 To mitigate this, various anodes have been proposed. Among them, anodes based on Sn seem promising for the high theoretical capacity (993 mAh/g, close to three times as that of graphite).1 However, the large volume change during the lithiation/delithiation processes of Sn based anodes, which induces the pulverization or aggregation of the Sn particles, is believed to be the main cause for the decrease of battery capacity. To promote the further applications of Sn-based anodes, Sn/C composites have attracted much attention due to their excellent electric contact and mechanical integrity. Various methods have been researched to generate well-designed structures of Sn/C composite anodes, such as repeated reduction by strong reducing agents, freeze-drying, and spray pyrolysis.1-3
Spray pyrolysis is a promising method to produce anode materials because of its scalable high-rate of production, facile equipment requirement, and simple post-treatment procedures. Spray pyrolysis requires a stable or monophasic precursor, without aggregation and precipitation in the precursor, for a uniform droplet-to-droplet composition.4 However, reported Sn-anode fabrication methods via spray pyrolysis all use Sn salts as the Sn source. Sn salts hydrolyze and form Sn oxide colloids with uncontrollable sizes in polarized solvents even at room temperature. The formation of uncontrollable Sn oxide aggregates in the precursor could result in a composition bias among the final particles because of the random Sn amount in the generated droplets.
We will present a new spray process to generate Sn/C anodes. Our method has successfully reduced the SnO2 colloids in the precursor to metallic Sn in the final powders without introducing H2 in the carrier gas. Our method integrates the features of spray drying (multiphase precursor) and spray pyrolysis (chemical reactions). It is termed as spray dryolysis. By applying spray dryolysis, various structures of Sn/C anodes have been fabricated. C provides the elastic matrix and acts as a conductive agent, which increases the anti-pulverization ability. Our well designed Sn/C anodes exhibited high initial coulombic efficiency (~ 80 %) and high capability retention (1000 cycles). This work demonstrates a promising method to fabricate Li-ion battery anodes with high power density and reliability at industrial adaptable scale.
(1) Xu, Y.; Liu, Q.; Zhu, Y.; Liu, Y.; Langrock, A.; Zachariah, M. R.; Wang, C. Nano Letters 2013, 13, 470.
(2) Qin, J.; He, C.; Zhao, N.; Wang, Z.; Shi, C.; Liu, E.-Z.; Li, J. ACS Nano 2014, 8, 1728.
(3) Eom, K.; Jung, J.; Lee, J. T.; Lair, V.; Joshi, T.; Lee, S. W.; Lin, Z.; Fuller, T. F. Nano Energy 2015, 12, 314.
(4) Liang, Y.; Felix, R.; Glicksman, H.; Ehrman, S. H. To be submitted.
10:15 AM - NM6.9.03
Laser Pyrolysis—A Method of Interest for the Synthesis of Amorphous or Crystalline Si-Core C-Shell Nanoparticles - Application as Anode Material in Li-Ion Batteries
John Alper 1 , Julien Sourice 1 2 , Florent Boismain 1 , Adrien Boulineau 2 , Cecile Reynaud 1 , Cedric Haon 2 , Nathalie Herlin-Boime 1
1 CEA Saclay Gif Sur Yvette France, 2 CEA Grenoble Grenoble FranceShow Abstract
Although the Li-ion battery (LIB) currently offers the most suitable balance between power and autonomy for consumer electronics and electric vehicle applications, there continues to be a demand for increased energy capacity. One strategy to increase LiB’s energy density is to replace graphite (372 mAh.g-1) as the anode active material by higher specific capacity materials. Silicon appears as an attractive alternative material thanks to its high theoretical specific capacity (3579 mAh.g-1 for the Li3,75Si phase) and its low discharge potential. Despite being the focus of scientific activity for over 10 years, the use of silicon based anodes have not yet been realized because the performance of these materials degrades rapidly during cycling. Silicon nanostructuration together with association of carbon to Si greatly enhance the performances in terms of both cyclability and capacity. In particular, core-shell silicon-carbon Si@C nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation processes.
The innovative solution proposed here is to use at the anode nanoparticles of Si@C synthesized in a single step by a scalable continuous gas phase method particularly interesting for industrial production, i.e. the laser pyrolysis method. Moreover, thanks to the control of experimental parameters, this method allows producing an amorphous core of silicon (a-Si) as well as a crystalline one (c-Si); Indeed using a-Si as core material, instead of c-Si, is an considered option not often considered but it appears promising to enhance cyclability because a-Si is not subject to the drastic crystalline state alteration upon its first lithiation. In order to cumulate all the benefits cited above, active material should be a composite of an a-Si core covered with a carbon shell
We report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness which prevents detrimental oxidation of the a-Si cores. The advantages of the a-Si@C material will be emphasized by comparison with c-Si@C material used as active materials. In particular, cyclic voltammetry demonstrates that the amorphous core-shell composite reaches its maximal lithiation during the first sweep, which is attributed to the amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95 %. Moreover, post-mortem observations show an electrode expansion of less than 20% in volume where the nanostructuration is preserved.
10:30 AM - NM6.9.04
Gas-Phase Synthesis of Graphene—Advances and Applications
Albert Dato 1 , Pichaya Lertvilai 1 , Nicole Subler 1 , Jacob Knego 1
1 Department of Engineering