Symposium OrganizersBirgit Schwenzer, Pacific Northwest National Laboratory
Di Zhang, Shanghai Jiaotong University
Yun Jung Lee, Hanyang University
Bao-Lian Su, Wuhan University of Technology
Elaine D. Haberer, University of California, Riverside
Symposium Support Office of Naval Research
T3: Virus and Peptide Mediated Materials Synthesis
Tuesday PM, April 10, 2012
Marriott, Golden Gate, Salon C1
2:30 AM - T3.1
Enzyme-carbon Nanotube Ensemble Films for Biofuel Cells
Matsuhiko Nishizawa 1 3 Syuhei Yoshino 1 Takeo Miyake 1 3 Takeo Yamada 2 3 Kenji Hata 2 3
1Tohoku University Sendai Japan2Nanotube Institute, AIST Tsukiba Japan3JST-CREST Tokyo JapanShow Abstract
Enzyme-modified electrodes are core components of bioelectronic devices such as biofuel cells, which have attracted attention as safe power sources, generating electricity from natural fuels like sugars and alcohols. Nanostructured carbons have been widely used for fabricating enzyme-modified electrodes due to their large specific surface area. However, all attempts to incorporate nanoengineered carbon electrodes have focused on pre-structuring electrodes before enzyme modification. This is because the process for engineering carbon is bio-incompatible due to the use of organic solvents or heating. If the nanostructure of the electrode can be regulated in response to the enzyme to be immobilized, the resultant enzymatic ensemble would avoid the difficulty in post-modification of enzymes. We present here a method to achieve ideal enzyme electrodes having suitable intra-nanospace automatically regulated to the size of enzymes. We utilize a carbon nanotube forest (CNTF) consisting of extremely long (~1 mm) single-walled CNTs, which can be handled with tweezers, as a 100% binder-free carbon film. When liquids are introduced into the as-grown CNTF (CNTs with a pitch of 16 nm) and dried, the CNTF shrinks to a near-hexagonal close-packed structure (CNTs with a pitch of 3.7 nm) because of the surface tension of the liquids. By using an enzyme solution as the liquid, the CNTF is expected to dynamically entrap the enzymes during the shrinkage. This â?oin-situ regulationâ? approach has led to reproducible activity of enzyme electrodes, to the first free-standing flexible character, and to high-power density biofuel cells. The Fructose dehydrogenase (FDH) and Laccase (LAC) were used as the anodic and cathodic electrode catalysts, respectively. By connecting the FDH-CNTF anode and the LAC-CNYF cathode showed the power density reached 1.8 mW cm-2 (at 0.45 V) in stirred 200 mM fructose, 84% of which could be maintained after continuous operation for 24 h. The â?ofree-standing and flexibleâ? character of the present enzyme electrode is its most attractive advantage from a practical viewpoint. For example, the Enzyme-CNTF ensemble films can operate a light-emitting-diode (LED) device by wound on the electric leads. Recent relating publications:  â?oSelf-Regulating Enzyme-Nanotube Ensemble Films and Their Application as Flexible Electrodes for Biofuel Cellsâ? J. Am. Chem. Soc., 2011, 133, 5129.  â?oEnzymatic Biofuel Cells Designed for Direct Power Generation from Biofluids in Living Organismsâ? Energy & Environmental Science, in press.
2:45 AM - T3.2
Energy Generation Using Virus-based Piezoelectric Materials
Byung Yang Lee 1 4 Jinxing Zhang 2 5 Chris Zueger 3 4 Woo-Jae Chung 1 4 So Young Yoo 1 4 Eddie Wang 1 4 Joel Meyer 1 4 Ramamoorthy Ramesh 2 5 Seung-Wuk Lee 1 4
1University of California Berkeley USA2University of California Berkeley USA3University of California Berkeley USA4Lawrence Berkeley National Laboratory Berkeley USA5Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
We report the development of a novel genetically-tunable piezoelectric material based on biological nanoparticle M13 bacteriophage (phage) and its application in electronic and energy generating devices. M13 phage is a long-rod shaped bacterial virus covered by ~2700 copies of Î±-helical pVIII coat protein. These coat proteins have dipole moments arranged with 5-fold helical symmetry and no inversion center, resulting in significant piezoelectric response in both axial and radial direction of the phage, as confirmed by piezoresponse force microscopy (PFM) techniques. Interestingly, the piezoelectric response of individual phages can be genetically tuned by controlling the amount of charge in the coat proteins. We were able to fabricate large-area multilayer smectic phage films with high degree of ordered packing and alignment via controlled self-assembly of the M13 phages. These films exhibit similar mechanical properties to collagen but much higher piezoelectric coefficient (7.78 pm/V). Furthermore, we fabricated energy-generating devices using our multilayer phage films. The resulting phage-based nanogenerators typically generated up to ~6 nA and 400 mV of short circuit current and open circuit voltage, respectively, enough to drive microelectronic components such as liquid crystal displays. Our devices can be easily scaled up to produce increased current and voltage levels by integrating the energy generators in serial or parallel configuration. Finally, we also demonstrate the actuating capability of our phage-based piezoelectric material by generating acoustic vibration when an external electric field is applied to the material. We expect our results will accelerate further development of other biopiezoelectric materials for biomedical, electronic and energy generating purposes.
3:00 AM - *T3.3
Building Integrated Photocatalytic Materials Using Chemically Viral Capsids
Matthew Francis 1
1UC Berkeley Berkeley USAShow Abstract
Biological systems can achieve complex function through the integration of multiple catalysts, electron transfer sites, and chromophores. To create synthetic materials that can mimic these functional arrangements, we have converted the protein shells of two viruses into scaffolds that can position multiple objects with precise distance relationships. This strategy has been used to synthesize nanoscale arrays containing thousands of fluorescent molecules, providing efficient mimics of the light harvesting system present in photosynthetic organisms. Using a second set of modification sites, metal complexes have been incorporated into these assemblies to endow electron transfer capabilities. The cornerstone of these efforts has been a series of new synthetic reactions that can modify biomolecules with high site-selectivity and yield. This presentation will focus on the development of these methods and the performance of the new materials that have been built through their use.
3:30 AM - T3.4
DNA-Based Hybrids for Energy Storage Applications
Donna Joyce 1 Narayanan Venkat 1 2 Fahima Ouchen 1 2 Kristi M Singh 1 3 Steven R Smith 1 2 James G Grote 1
1Air Force Research Laboratory Wright-Patterson AFB USA2University of Dayton Research Institute Dayton USA3UES Inc. Dayton USAShow Abstract
Polymer insulation materials are widely used in power generation and energy storage applications. Deoxyribonucleic acid (DNA) based hybrids have been found to demonstrate chemical structure and electrical characteristics, such as dielectric constant and dielectric breakdown behavior, that are interesting as an insulation material for a capacitor. This project includes processing, test structure design and electrical characterization of DNA-hybrids for energy storage applications.
T4: Artificial Photosynthesis
Tuesday PM, April 10, 2012
Marriott, Golden Gate, Salon C1
4:30 AM - *T4.1
Carbon Leaves - Artificial Photosynthesis Based on Low Dimensional Carbons
Dirk M Guldi 1
1University of Erlangen Erlangen GermanyShow Abstract
Combining the rapidly evolving fields of nanostructured materials and supramolecular chemistry is an attractive strategy for constructing large and complex, yet highly ordered, molecular and supramolecular entities, with specific functions. We develop novel super- and supramolecular donor-acceptor architectures through careful design, and probe them in condensed media and organized thin films at semiconductor surfaces as viable tools for efficient conversion of solar energy. Carbon nanostructures (i.e., fullerenes and carbon nanotubes) and porphyrins / phthalocyanines are molecular architectures ideally suited for devising integrated, multicomponent model systems to transmit and process solar energy. Implementation of C60 as a 3-dimensional electron acceptor holds great promise on account of its small reorganization energy in electron transfer reactions and has exerted noteworthy impact on the improvement of light-induced charge-separation. I will discuss recent developments in exploring molecular donor-acceptor arrays based on empty fullerenes as well as on endohedral metallofullerenes, in which key features, such as donor-acceptor composition, donor-acceptor distance, electronic coupling, etc., are systematically altered to achieve charge separation quantum yields and lifetimes that closely resemble those seen in the natural photosynthetic reaction center.
5:00 AM - T4.2
Light Harvesting Single Wall Carbon Nanotube Hybrids
Jong Hyun Choi 1 2 3 Hanyu Zhang 1 2 3 Tae-Gon Cha 1 2 3
1Purdue University West Lafayette USA2Purdue University West Lafayette USA3Purdue University West Lafayette USAShow Abstract
With extraordinary optical and electronic properties, single wall carbon nanotubes (SWNT) are explored as molecular wires in light harvesting systems. Here, SWNT are employed in self-assembling, light-harvesting nanohybrids. A novel structure is developed that employs the oligonucleotides as a multifunctional â?oglue,â? simultaneously suspending SWNT while exploiting DNA target recognition capabilities to recognize porphyrin chromophores. The nanohybrid structures are characterized using a combination of optical, photo-electrochemical techniques. Transductions in absorption spectra and fluorescence quenching show evidence of molecular interactions between porphyrin molecules and the nanotubes. Photoelectrochemical measurements provide further evidence of charge transfer interactions between photo-excited porphyrin and SWNT. This hybrid offers a facile manufacturing method for light harvesting nanomaterials, providing a novel pathway for generating photocurrent.
5:15 AM - T4.3
Electrochemical Investigation into the Photoactivated Electronic Ativities of Photosystem I (PS I) Immobilized on Self-assembled Monolayer/Gold Substrates
Dibyendu Mukherjee 1 3 Ilia Ivanov 2 Bamin Khomami 3
1University of Tennessee Knoxville USA2Oak Ridge National Laborator (ORNL) Oak Ridge USA3University of Tennessee Knoxville USAShow Abstract
During photosynthesis plants and algae use Photosystem I (PS I), a supra-molecular protein complex, to harnesses solar energy with 100% quantum efficiency. In doing so, the trimeric protein complex activates a light-induced (Î»=680 nm) directional electron transfer chain that, mediated by a series of redox reactions, initiates at the lumenal (mid-point potential, Em (P700/ P700+) â?^ +0.4 V) and terminates at the stromal side (mid-point potential, Em (FA; FB; FX) â?^ -0.7 V) of PS I. Such highly efficient photo-electrochemical activity of PS I has inspired our recent extensive studies[1-3] on the synthesis of uniform PS I monolayer on alkanethiolate self-assembled (SAM)/gold (Au) surfaces as the first step towards the incorporation of PS I into highly efficient hybrid photovoltaic devices. In an effort to understand the photo-activated properties of surface immobilized PS I monolayer, recent direct electrochemical measurements of PS I trimers assembled on C9-alkanethiolate SAM/Au substrates demonstrate, for the first time, a light-induced energetic electron transfer from the Au donor facilitated by photoexcitation of the reaction center P700 housed in the PS I complexes. Furthermore, results from electrochemical impedance spectroscopy (EIS) measurements, when fitted with equivalent electrical circuit models, reveal a light-induced reduction in the charge transfer resistance at the PSI/SAM-electrolyte interface. Such observations, in conjunction with measurements for the transient electronic behavior, reveal the underlying mechanistic picture for the photo-excited electronic activities in PS I monolayer assembly on SAM/Au substrates. References:  D. Mukherjee, M. Vaughn, B. Khomami, B. D. Bruce, Colloids and Surfaces B: Biointerfaces 2011, 88, 181  D. Mukherjee, M. May, B. Khomami, J. Colloid Interface Sci. 2011, 358, 477.  D. Mukherjee, M. May, M. Vaughn, B. D. Bruce, B. Khomami, Langmuir 2010, 26, 16048.  D. Mukherjee, H. Niroomand, B. Khomami, Energy & Environmental Science 2011, Submitted.
5:30 AM - *T4.4
Bio-inspired Organic Materials for Energy and Medical Applications
Hiroshi Imahori 1 2
1Kyoto University Kyoto Japan2Kyoto University Kyoto JapanShow Abstract
Organic materials have drawn much attention due to their potential applications in organic thin-film optoelectronics such as organic light-emitting diodes, organic transistors, and organic solar cells. Over the last 20 years, tremendous progress has been achieved in the design and fabrication of the compounds. In this regard, charge-transporting properties of organic thin films have found to be crucial in organic transistors, whereas excellent charge separation and charge-transporting properties of organic thin films are essential for organic solar cells. In this talk I will present some of our recent examples of bio-inspired organic materials for energy and medical applications. In particular, porphyrins are an important class of potential sensitizers for highly efficient dye-sensitized solar cell (DSSC) owing to their photostability and high light-harvesting capabilities as seen in natural photosynthesis. Porphyrins possess an intense Soret band at 400 nm and moderate Q bands at 600 nm. Nevertheless, the poor light-harvesting properties relative to the ruthenium complexes have limited the cell performance of porphyrin-sensitized TiO2 cells. Elongation of the pi-conjugation and loss of symmetry in porphyrins cause broadening and redshift of the absorption bands together with an increasing intensity of the Q bands relative to that of the Soret band. On the basis of the strategy, the cell performance of porphyrin-sensitized solar cells has been improved intensively by the enhanced light absorption. Actually, some push-pull type porphyrins have disclosed a remarkably high efficiency (6-7%) that was close to that of the ruthenium complexes. 1) J. Am. Chem. Soc. 2009, 131, 3198. 2) J. Phys. Chem. C (Feature Article) 2009, 113, 9029. 3) J. Phys. Chem. Lett. (Perspective) 2010, 1, 1020. 4) J. Am. Chem. Soc. 2011, 133, 7684. 5) J. Am. Chem. Soc. 2011, 133, 7684. 6) Angew. Chem. Int. Ed. 2011, 50, 4615. 7) Energy Environ. Sci. (Perspective) 2008, 1, 120. 8) Adv. Mater. 2010, 22, 1767. 9) Angew. Chem. Int. Ed. 2011, 50, 8016. 10) Energy Environ. Sci. 2011, 4, 741. 11) Acc. Chem. Res. 2009, 42, 1809. 12) J. Phys. Chem. A 2011, 115, 3679. 13) ChemSusChem 2011, 4, 797. 14) J. Phys. Chem. C 2011, 115, 14415.
T5: Poster Session: Bio-inspired Materials for Energy Applications
Tuesday PM, April 10, 2012
Moscone West, Level 1, Exhibit Hall
6:00 AM - T5.1
Sputter Deposition of Copper Oxide on Virus-structured Current Collectors for the Photoelectrolysis of Water
Jillian Michele Epstein 1 Chia-Ying Chiang 2 Adam Brown 3 James Culver 3 Sheryl Ehrman 2
1University of Maryland College Park USA2University of Maryland College Park USA3University of Maryland College Park USAShow Abstract
The inability of current chemical processes to produce pure hydrogen efficiently and sustainably through water electrolysis inhibits the pragmatic, industrial application of photoelectrochemical cells. Copper oxide (CuO) is an attractive candidate to perform photoelectrolysis because of its bandgap (1.4 â?" 1.7 eV) which favors photon absorption within the visible region. Furthermore, CuO is an easily scalable material which is highly affordable, abundant, and nontoxic. Thus, we investigated the photoelectrochemical properties of p-type CuO nanoparticles. For the initial phase of this study, we focused primarily on optimizing the purity and photocurrent density difference under darkness and illumination of reactively sputtered CuO on indium tin oxide (ITO)/glass substrates. RF sputtering was selected for the deposition of CuO because of its ability to produce evenly dispersed, low resistance thin films. CuO also possesses a short carrier diffusion length and is thus prone to undergoing electron/hole recombination. To reconcile this, we vertically patterned 3D current collectors comprised of self assembled, genetically modified nickel-coated Tobacco Mosaic Virus (TMV1cys) on the ITO/glass substrate. The TMV1cysâ?Ts high aspect ratio (with an average length of 300 nm and diameter of 18 nm) reduced the distance for charge carrier transport to the surface of the semiconductor and expanded the available surface area for photon absorption to increase water electrolysis reactions. The nickel coating on the TMV1cys functioned as a current collector to facilitate current flow to the external circuit. At this point in our investigation, the virus current collectors in the CuO photoelectrochemical cell increased the photocurrent density by up to 2.6 times that of a CuO photoelectrochemical cell without the virus template.
6:00 AM - T5.2
Biologically Inspired Synthesis of Nanostructured Zinc Oxide for Solar-Based Applications
Wenting Hou 1 Ana Bowlus 1 Taysir Awad 1 Dongsheng Li 1 David Kisailus 1
1University of California, Riverside Riverside USAShow Abstract
Biological mineralizing processes demonstrate how nature can produce elegant structures at room temperature through controlled organic-mineral interactions. These organics exist as either soluble forms or as insoluble scaffolds that are often used to control shape, size and orientation of mineral. Based on inspiration from Nature, we are using organic agents to mimic the organic-mineral interactions process, to synthesize ZnO nanostructured materials under mild solution conditions. These organics offer the potential to modify ZnO crystal nucleation and growth behavior. Various preparative parameters, such as initial reactant concentration, precursor salts, solvents, pH, Temperature, and organic ligands have been systematically examined. By understanding the mechanism of ZnO nucleation and growth, through a tuning of the synthetic parameters, we can exert control over nanostructural size and morphologies to affect performance in optoelectronic devices. These ZnO nanostructures will be incorporated into devices like dye-sensitized solar cells to derive structure-function relationships.
6:00 AM - T5.3
Transport and Photo-voltaic Properties of Bacteriorhodopsin Thin Films for Next-generation Protein Electronics
Rakesh Guduru 1 John M Bryant 1 Jeongmin Hong 1 Ping Liang 2 Dmitri Litvinov 3 Sakhrat Khizroev 1
1Florida International University Miami USA2University of California, Riverside Riverside USA3University of Houston Houston USAShow Abstract
The purpose of our research is two-fold; to stabilize the deposition process and measure transport and photo-voltaic properties of bacteriorhodopsin (BR) protein films suitable for next-generation electronics applications. The key advantages of using BR for next-generation electronics include its eco-friendliness, abundant availability in nature, thermal (up to 140 degree celsius) and photo-chemical stability, unprecedented high quantum efficiency (~0.65), a wide operational bandwidth (400-620 nm) and high sensitivity (1-80 mJ/cm2). A study of various deposition methods, such as electrophoretic sedimentation, electrostatic self-assembly and spin coating, for immobilizing BR onto different substrates will be presented. The results of atomic force microscopy (AFM) and scanning tunneling microscopy (STM) measurements will be analyzed. Transport measurements conducted locally (via nanoprobe techniques) and globally (via regular IV measurements) and photo-voltaic measurements will be presented. Several device concepts based on BR films will be presented.
6:00 AM - T5.4
Nano-Biohybrid Light-Harvesting Systems for Solar Energy Applications
Woo Jin An 1 Jessica Co-Reyes 1 Vivek B Shah 1 Wei-Ning Wang 1 Robert E Blankenship 2 3 Pratim Biswas 1
1Washington University in St. Louis St. Louis USA2Washington University in St. Louis St. Louis USA3Washington University in St. Louis St. Louis USAShow Abstract
Sensitized solar cells offer a useful design to overcome limitation in performance. A dye-sensitized solar cell (DSSC) was a breakthrough in solar energy utilization in 1991.1 However, single species of dye molecules limit absorption of photon energy in the visible light range. Co-sensitized methods with multiple sensitizers may cause kinetic complexity in the device. To resolve the limitation of light absorption, various natural light-harvesting systems have been researched. Chlorosomes, natural photosynthetic assemblies, have evolved to capture and utilize photons, which exist widely from UV (ultraviolet) to NIR (near infrared), with a higher quantum and energy conversion efficiency than any other artificial systems. Chlorosomes lose their reaction center, which functions as a charge separation center, when they are extracted from organisms. Therefore, despite their superior properties for harvesting wide-light spectrum, chlorosomes cannot be directly utilized as sensitizers for photovoltaic devices. By employing the black dye molecules, which function as an artificial reaction center satisfying the FRET (FÃ¶rster resonance energy transfer) model with chlorosomes, a bio-hybrid light-harvesting complex was employed in a photovoltaic cell device.2 For this study, PbS quantum dots are used for artificial reaction centers instead of black dye molecules. Successive ionic layer adsorption and reaction (SILAR) allows for an easy deposition of different sizes of PbS quantum dots with different cycles. Natural light-harvesting antenna complexes, chlorosomes were sequentially deposited onto the PbS quantum dots surface by electrospray. Energy transfer of these biohybrid systems, with different sizes of PbS quantum dots, will be explored. Furthermore, the improved bio-hybrid solar cells will be presented. REFERENCES 1. Oâ?TRegan, B. and GrÃ¤tzel, M. A low-cost and high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737-740 (1991). 2. Modesto-Lopez, L. B., Thimsen, E. J. Collins, A. M., Blankenship, R. E. and Biswas, P. Electrospray-assisted characterization and deposition of chlorosomes to fabricate a biomimetic light-harvesting device. Energy & Environ. Sci. 3, 216-222 (2010).
6:00 AM - T5.5
Enzyme-mediated Synthesis of a Semiconducting Metal Oxide
John Michael Johnson 1 Dongsheng Li 3 Yobed Woldeabzghi 1 Chhay Sun 1 Yongfeng Zhao 2 Jiayu Liao 2 David Kisailus 1
1University of California - Riverside Riverside USA2University of California - Riverside Riverside USA3Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
Enzymes are an important class of biological molecules, their specific functionality being exploited to perform tasks beyond the reach of conventional chemistry. Because they are operational under environmentally friendly, ambient conditions, the adaptation of these biomacromolecules can be used to replace current energy intensive and environmentally harsh synthesis methods for materials applications. In our research, the enzyme urease has been used to modify the solution environment of a water soluble and stable TiO2 precursor under benign conditions (i.e., room temperature, near neutral pH) to yield monodisperse TiO2 nanostructures. Furthermore, immobilization of urease onto self-assembled monolayers is being studied in order to provide a reusable catalytic system for TiO2 synthesis. The prepared TiO2 nanostructures can be utilized for numerous engineering applications such as low cost photovoltaics and photocatalysis.
6:00 AM - T5.6
M13 Bacteriophage-Assisted Biomineralization of Cu2S Nanowire Structures for Solar Cell Applications
Mohammed Shahriar Zaman 1 Elaine D Haberer 1 2
1University of California-Riverside Riverside USA2University of California-Riverside Riverside USAShow Abstract
In recent years, the availability of low cost, renewable energy sources capable of meeting a significant portion of global energy demands has become a concern. In this report, we investigate the biomineralization of Cu2S using a viral template. Unlike many second generation solar cell materials which contain scarce and possibly toxic elements (i.e. In, Ga, Te, and Se), Cu2S is an abundant, non-toxic semiconductor material. Furthermore, its 1.2 eV bulk bandgap is near the theoretical optimum for maximum efficiency of a single junction solar cell. Historically, Cu2S-based cells have been problematic due to rapid Cu diffusion caused by elevated fabrication temperatures; however our biomineralization approach occurs at room temperature thereby minimizing diffusion. In these biomineralization studies, an 8-mer M13 pVIII combinatorial phage display library was used to select Cu2S-binding peptides. The biopanning procedure was modified to minimize the release of Cu ions from Cu2S; an abundance of Cu ions within biopanning solutions was found to be deleterious to phage viability. Clones were sequenced and analyzed from biopanning round five. Six unique amino acid sequences were identified from selected clones. Compared to the library, these peptides were rich in basic, hydrophobic, and polar residues; however the peptides were net negatively charged under experimental conditions as indicated by their calculated isoelectric points (pH 4-4.37). Over half of the clones sequenced (16 of 24) displayed the same peptide: DTRAPEIV. Notably, this peptide is lacking histidine, a key amino acid in binding copper or copper sulfide compounds. A pVIII-modified M13 phage with this peptide fusion was used for subsequent biomineralization experiments. CuCl2 and Na2S were used as chemical precursors to nucleate and grow nanocrystalline copper sulfide along the major coat protein under various pH conditions. We believe that the copper ions from the CuCl2 form complexes with the peptides which produce copper sulfide nanocrystals upon addition of the Na2S. Control experiments completed with wild-type phage without a foreign peptide insert and without phage did not produce nanowire structures. Transmission electron microscopy was used to characterize the size, shape, morphology, and hierarchical structure of the biomineralized nanomaterials. Using electron diffraction, the bio-templated material was found to be a mixture of Cu-deficient crystalline phases. Energy dispersive spectroscopy confirmed the elemental composition and material stoichiometry. Furthermore, the optical absorption was measured and the effective band edge determined using the Tauc equation for an indirect semiconductor. This bio-directed room temperature synthesis of Cu2S is a first step toward sulfide-based low cost, solar cells not limited by material supply.
T1: Bio-inspired Inorganic Synthesis
Tuesday AM, April 10, 2012
Marriott, Golden Gate, Salon C1
9:30 AM - *T1.1
High Power Nanostructured Anodes and Cathodes and Thermal Protectant for Li-ion Batteries: Fabrication by Novel Bio-inspired, Kinetically Controlled, Low-temperature Catalysis
Daniel E. Morse 1 Hong-Li Zhang 1 Jon F von Bulow 1 Teyeb Ould-Ely 1 Krisztian Niesz 1
1University of California Santa Barbara USAShow Abstract
We report a new low cost, low temperature method for kinetically controlled catalytic synthesis of nanostructured components for high-performance Li ion and Li batteries. Anodes made by this method consist of tin or silicon nanoparticles grown in situ, uniformly dispersed within the pores and interstices of highly compliant and conductive microparticulate graphite or commercial carbon nanotubes. These composites exhibit exceptionally high power, electrochemical capacity, stability and cyclability significantly greater than present commercial materials. Our Sn-in-graphite nanocomposite exhibits 30% greater specific electrochemical capacity (50% greater volumetric capacity) than present commercial graphite anodes, with exceptionally stable cyclability, under conditions in which a composite with comparable content of Sn fabricated by conventional procedures exhibits rapid deterioration and loss of capacity. This anode retains 90% of its initial electrochemical capacity at a discharge rate of 10C (nearly twice the rate-capacity of present commercial anode materials) and retains ca. 50% of its original capacity after discharge at the extremely high rate of 50C, with complete recovery to 100% of original capacity â?" performance virtually unprecedented by present standards. Our nanocrystalline silicon in carbon nanotube composites exhibit exceptionally high energy density, stable cyclability and low hysteresis. Nanostructured cathodes made by this method also exhibit exceptionally high power and superior cyclability, with specific capacities 70% greater than present commercial levels. BaTiO3 and BaSrTiO3 nanocrystals (6 nm) are made by this method in very high yield and purity. When doped and sintered, the resulting fine-grained nanocrystalline ceramic exhibits a strong positive thermal coefficient of resistivity with a sharp increase of resistance of 10,000-fold when heated above the Curie temperature (tunable by doping), uniquely suitable for use as an internal protectant against thermal runaway in Li ion batteries. Scalability to pre-pilot scale has been demonstrated. We recently formed a spin-off company, LifeCel Technology, to commercialize these technologies.
10:00 AM - *T1.2
A General Strategy for Functional Materials Synthesis
David C Green 1 Stefan Glatzel 2 Andrew M Collins 1 Avinash J Patil 1 Simon Robert Hall 1
1University of Bristol Bristol United Kingdom2Max Planck Institute of Colloids and Interfaces Potsdam GermanyShow Abstract
This work describes, for the first time, a unified approach to the synthesis of a plethora of functional materials, including semiconductors, superconductors, multiferroic, piezoelectric, ferromagnetic and phosphorescent materials. This strategy is based on a general phase-transfer method which produces pure functional materials via a unique dehydrated ionic liquid precursor. We believe that our new protocol provides a simple and superlative route to materials with applications in energy generation, transmission and storage; transistors, diodes, actuators, magnetic field sensors and new types of electronic memory devices. Ionic liquids have been described as "super-dissociating" solvents due to their ability to completely solvate inorganic salts, creating highly screened species. Perhaps surprisingly, this feature of ionic liquid behaviour has yet to be explored in detail, research instead concentrating on the dissolution of molecular species. We exploit the super-dissociating behaviour in this paper, with the first demonstration of ionic liquid-based precursors in the synthesis of functional materials. All these materials, even those traditionally considered to be difficult to synthesize, are produced with absolutely no impurity phases and on timescales that are much shorter than other synthetic techniques.
10:30 AM - T1.3
Biomimetic Chalcogels: Porous Chalcogenide Framework Materials as Solar Fuel Catalysts
Benjamin Daniel Yuhas 1 Mercouri G Kanatzidis 1
1Northwestern University Evanston USAShow Abstract
Biological systems capable of transforming sunlight into energy contain a great deal of chemical diversity, incorporating light harvesting components, electron transfer pathways, and redox-active centers all into one superstructure. The design of catalysts modeled after the active sites in proteins, also known as biomimetic catalysis, is attracting increased research interest, particularly in the areas of solar fuels and artificial photosynthesis. In nature, transition metal clusters are typically the active centers in biomolecules that are capable of producing hydrogen and oxygen from water, such as hydrogenase enzymes or photosystem II. There are many examples of synthetic transition metal clusters that have been successfully shown to catalyze the production of hydrogen or oxygen from water. However, nearly all of the studies done on these species are performed on single, isolated clusters in solution, as opposed to part of a larger network as is found in nature. If biomimetic catalysis is to evolve, equal consideration must be given not only to the design of suitable catalyst molecules, but also their integration into larger architectures. We have recently developed a new class of porous semiconducting chalcogenide materials, dubbed chalcogels. These materials are formed by the metathesis of main group cluster anions with the formulae MQ4, M2Q6, or M4Q10 (M = Sn, Ge; Q = S, Se, Te) and divalent transition metal cations, such as Pt2+, yielding highly porous framework solids with surface areas comparable to silica-based aerogels, but capable of strong visible light absorption. Additionally, we are able to synthesize chalcogels containing transition metal clusters similar to those found in nature, such as [Fe4S4] or [Mo2Fe6S8]. The transition metal clusters are covalently bound into the chalcogenide scaffold, yielding a porous material with excellent aqueous stability, as well as preserved redox activity and electrocatalytic ability for a variety of substrates. Furthermore, we can also incorporate light-harvesting dye molecules into the chalcogels in variable proximity to the clusters, allowing for the possibility of photocatalysis of solar fuels in a stable, biomimetic system. The chalcogel synthesis can also be adapted to a variety of biomimetic clusters, as well as main group linking clusters, all from a one-pot, bottom-up process. Our chalcogels thus show great promise as complex, multi-functional, solid-state materials with high porosity that can be engineered and functionalized to have all of the necessary components required for light-driven chemical processes, which will greatly enhance the prospects for solar fuel production.
10:45 AM - T1.4
Bio-inspired Materials for Energy Conversion and Storage
Xiaodong Chen 1
1Nanyang Technological University Singapore SingaporeShow Abstract
Bio-inspired materials, inspired by the diverse and sophisticated materials and hierarchical material systems found in nature, are becoming of increasing interest. Currently, it more focuses on developing a fundamental understanding of the synthesis and hierarchical organization of natural occurring materials, and uses this understanding to engineer new eco-friendly "bio-inspired" materials for diverse applications. This talk will describe our recent efforts on developing bio-inspired materials for energy conversion and storage. First, I will discuss how the bio-inspired materials can be developed and used for light harvesting with enhanced photo-activity. Then, I will show several; examples on how we developed universal approaches for creating bio-inspired hierarchical structures for energy storage. When the bio-inspired hierarchical structures were used as electrode materials, they behaved enhanced energy storage performance.
T2: Molecular Approaches to Energy Applications
Tuesday AM, April 10, 2012
Marriott, Golden Gate, Salon C1
11:30 AM - *T2.1
Peptides in the Outer-coordination Sphere Modulate Ni(P2N2)2 Hydrogen Production Activity
Wendy Shaw 1 Avijita Jain 1 Matthew Reback 1
1Pacific Northwest National Labs Richland USAShow Abstract
The superior rates and specificity of enzymes as compared to many homogeneous catalysts demonstrate that the outer coordination sphere (OCS) is as essential as the active site for efficient function. We are trying to design desirable enzymatic traits in homogeneous catalysts allowing us to explore and develop a mechanistic understanding of the role of the OCS, with the potential of enhancing the rates, selectivity and specificity of the catalyst. We are developing redox active catalysts which oxidize and produce H2, mimicking the hydrogenase enzyme. Like other enzymes, hydrogenase enzymes use many OCS features to very efficiently convert H+ to H2 and back again. Our initial work in this area has focused on incorporating small peptides around the active site of the Ni(P2RN2Râ?T)2 hydrogen production/oxidation catalysts to explore how the local environment can influence catalytic rates. We have found that the addition of small peptides retains the activity of the parent catalyst, while demonstrating that regions remote from the active site do modulate this activity. The modulation of activity due to the remote dipeptide outer-coordination sphere will be discussed, along with results on catalysts with lager peptides attached.
12:00 PM - T2.2
Bioinspired Hybrid Photoelectrode for Solar Water Splitting
Debajeet Kumar Bora 1 2 Elena Rozhkova 3 Krisztina Gajda-Schrantz 1 4 Pradeep Wyss 1 5 Artur Braun 1 Edwin C Constable 2 Thomas Graule 1 6
1Empa. Swiss Federal Laboratory for Material Sciecne and Technology Dubendorf Switzerland2University of Basel Basel Switzerland3Argonne National Laboratory Chicago USA4University of Szeged Szeged Hungary5FHNW - University of Applied Sciences Northwestern Switzerland Muttenz Switzerland6Technische Universitauml;t Bergakademie Freiberg GermanyShow Abstract
A bioinspired hybrid photoelectrode have been fabricated by the integration of light harvesting molecule C- phycocyanin with nanostructured thin film of hematite. Phycocyanins have light-harvesting properties and belong to the phycobilisome protein family. They are present in cyanobacteria, which capture light energy and funnel it to reaction centers during photosynthesis. Here, a way of increasing the photocurrent of hematite by covalent cross-coupling with phycocyanin is reported. For this, a hematiteâ?" phycocyanin integrated system is assembled by consecutive adsorption and cross-coupling of protein molecules, separated by an agarose layer and a linker molecule, on the top of a mesoporous hematite film. The hematiteâ?" phycocyanin assembly shows a two-fold increased photocurrent in comparison with pristine hematite film. The increase in the photocurrent is attributed to the enhanced light absorption of the hematite film after integration with the protein, as is evident from the UVâ?"vis spectra and from the photocurrent-action spectrum. The assembly shows long-term stability and thus constitutes a promising hybrid photoanode for photo-electrochemical applications.
12:15 PM - T2.3
A Dendronized Polymer Designed to Mimic the Efficient Energy Transfer in Photosynthesis
Pamela Lundin 1 Graham B Griffin 2 Gregory S Engel 2 Zhenan Bao 1
1Stanford University Stanford USA2University of Chicago Chicago USAShow Abstract
The energy transfer mechanism in photosynthesis proceeds with remarkable efficiency. Through quantum-beating experiments, it has been shown that in some photosynthetic complexes this efficiency is due to a wave-like transfer mechanism.1 Here, we will discuss our efforts to replicate this coherent energy transfer in an artificial systemâ?"in our case, a dendronized polymer consisting of a conjugated polymer backbone with attached conjugated dendrimers. The design and synthesis of the dendronized polymer will be presented, along with the results of our experiments probing whether this system displays coherent energy transfer. 1 Panitchayangkoon,G.; Hayes, D.; Fransted, K. A.; Caram, J. R.; Harel, E.; Wen, J.; Blankenship, R. E.; G.S. Engel G. S. PNAS, 2010, 107, 12766-12770.
Symposium OrganizersBirgit Schwenzer, Pacific Northwest National Laboratory
Di Zhang, Shanghai Jiaotong University
Yun Jung Lee, Hanyang University
Bao-Lian Su, Wuhan University of Technology
Elaine D. Haberer, University of California, Riverside
Symposium Support Office of Naval Research
T7: Bio-inspired Electrical Transport
Wednesday PM, April 11, 2012
Marriott, Golden Gate, Salon C1
2:30 AM - *T7.1
Bio-Inspired Smart Nanochannels
Lei Jiang 1
1Institute of Chemistry, Chinese Academy of Sciences Beijing ChinaShow Abstract
Bio-inspired materials and devices are attracting increasing interest because of their unique properties, which have paved the way to many significant applications. Ion channels that exist in living organisms play important roles in maintaining normal physiological conditions and serve as â?osmartâ? gates to ensure selective ion transport. Thus, designing a system that simulates these complex processes in living systems is a challenging task for nanoscience. The gating property nanochannel is realized by modifying the surface with functional molecules that can respond to external stimuli. Recently, we have developed various responsive nanochannel systems which were controlled by our designed biomolecules or smart polymers responding to the single external stimulus, provided an artificial counterpart of switchable protein-made nanochannels. Most recently, we developed dual-responsive single nanochannel systems, and compared with the single external stimulus systems, the present work is more complicated and moves one step farther for the development of â?osmartâ? nanochannel systems for real-world applications. These intelligent nanochannels could be used in energy-conversion system, such as photoelectric conversion system inspired by rhodopsin from retina or bR, and concentration-gradient-driven nanofluidic power source that mimic the function of the electric eels. Learning from nature is a constant principle for there are numerous mysterious properties in nature, which have developed over millions of years of evolution and will give us inspiration to develop novel functional interfacial materials.
3:00 AM - *T7.2
Electrostatic Assemblies of Biomolecules: Toward Hybrid Electrochemical Devices
Ki Tae Nam 1 Uk Sim 1 Hui Yun Jeong 1 Byungjin Koo 1
1Seoul National University Seoul Republic of KoreaShow Abstract
Bio-systems have inherently developed very specific molecular recognition patterns that can be manipulated through genetic control. It also can be used to exert molecular scale control over nucleation, growth, and stabilization of inorganic materials, analogous to the process of biomineralization. Furthermore, due to the remarkable capability of biological molecules to self-assemble at multiple length scales, the opportunity exists for designing novel nanomaterials via genetic modification and then constructing hierarchically assembled structures. The combination of biological self-assembly and biosynthesis of nanomaterials can enable us to create entirely new concepts applications and devices. In my presentation, I will describe how the biological approach not only contribute to improving the properties of current energy devices but also provide a new paradigm for designing highly efficient, small scale electrochemical devices. As an example, genetically engineered M13 virus can be used to make a nanostructured electrode for Lithium ion battery. I will also talk how this understanding can be extended to other proteins and non-natural biomimetic systems such as peptoids. Peptoids are a novel class of non-natural polymer based on oligo-N-substituted glycine, designed to mimic peptides and proteins. Their side chains are appended to the amide nitrogen rather than the alpha carbon as in a peptide. Additionally, week complexation between oppositely charged polymers can drive the spontaneous assembly of biomolecules by providing high mobility. In the later part of my talk, I will discuss about the design of hybrid system as a catalyst for water splitting.
3:30 AM - T7.3
Carbonized Chicken Eggshell Membranes with 3D Architectures as High-Performance Electrode Materials for Supercapacitors
Zhi Li 1
1National Institute for Nanotechnology Edmonton CanadaShow Abstract
We synthesized supercapacitor electrode materials by carbonizing a common livestock biowaste in the form of chicken eggshell membranes. The carbonized eggshell membrane (CESM) is a three-dimensional macroporous carbon film, composed of interwoven connected carbon fibers containing around 10 wt% oxygen and 8 wt% nitrogen. Despite a relatively low surface area of 221 m2 g-1, exceptional specific capacitances of 297 F g-1 and 284 F g-1 are achieved in basic and acidic electrolytes in 3 electrode systme, respectively. Furthermore the electrodes demonstrate excellent cycling stability: only 3% capacitance fading is observed after 10,000 cycles at a current density of 4 A g-1. These very attractive electrochemical properties are discussed in the context of the unique structure and chemistry of the material.
T6: Next Generation Principles and Designs
Wednesday AM, April 11, 2012
Marriott, Golden Gate, Salon C1
9:45 AM - *T6.1
Imagine* Photosynthesis Where Human Ingenuity Supersedes Evolution (*John Lennon)
Thomas Moore 1 Ana Moore 1 Devens Gust 1
1Arizona State University Tempe USAShow Abstract
Operating at ~ 133 TW, photosynthesis powers the biosphere and is fully booked providing biosphere service and support. Anthropogenic activity takes a cut of the 133 TW with crop photosynthesis today being driven by unsustainable agricultural practices to produce food and limited bioenergy for human use. In fact, there are no reserves of photosynthetic capacity to provide food for the ever-increasing human population and to meet the added burden of biofuel for growing our GDP. Indeed, when such demands are made the capacity comes at the peril of biosphere service and support, pushing the planet further from a sustainable trajectory. Fortunately, photosynthesis can be dramatically improved to meet human needs. The theoretical limit to solar energy conversion efficiency is set by fundamental thermodynamic principles that apply to the isothermal conversion of light into chemical and/or electrical potential. Photovoltaic technology uses these principles combined with advances in materials to achieve record efficiencies of solar to electrical power conversion. Photosynthesis, having been optimized by Darwinian selection to move genes forward, is not optimal for providing solar-derived fuel to support human activities. Measured against the conversion efficiency of PV-driven electrolysis, the less-than-optimal efficiency of photosynthesis is obvious and starts with a poor match of the absorption of light by photosynthetic organisms to the solar spectrum. In selected photosynthetic systems, rational design, based on the principles demonstrated in artificial systems and the techniques of molecular and synthetic biology, can be used to optimize solar-to-biofuel conversion efficiencies to meet particular needs. Key biological systems necessary to initiate this research are found in extant photosynthetic organisms. My lecture will draw attention to opportunities for far-reaching research and will cover our progress using fundamental design principles and technology to inspire the design of high efficiency artificial and natural photosynthesis. This work includes the design of low and high potential artificial reaction centers with appropriate antenna systems arranged in a tandem, two-junction configuration to oxidize water and reduce protons to hydrogen. Several water oxidation catalysts are being used at the high potential junction and work describing the use of hydrogenase enzymes at the low potential junction will be described. Related work will be presented on the role of model systems in unraveling the mechanism whereby carotenoid pigments control 133 TW of photosynthetic power flow. Understanding control systems is key to re-engineering photosynthesis. The combination of technology with rationally designed biology can be a step towards achieving sustainable energy production based on efficient solar-driven water oxidation and proton and/or carbon reduction.
10:15 AM - T6.2
Deposition of Thin Biocomposite Coatings for Photobiological Fuel Cells by Continuous Convective Assembly
Jessica S. Jenkins 1 Michael C Flickinger 1 2 Orlin D Velev 1
1North Carolina State University Raleigh USA2Golden LEAF Biomanufacturing Training and Education Center Raleigh USAShow Abstract
Photobiological hydrogen production by the purple nonsulfur bacterium Rhodopseudomonas palustris, combined with oxygen evolution by the green algae Chlamydomonas reinhardtii, could be used in new photoreactive fuel cells if the bacteria or algae are immobilized in thin functional films. We are developing a rapid and reproducible method for fabricating biocomposite coatings containing hydrogen-producing or oxygen-evolving cells by continuous convective assembly. The method allows controlled deposition of coatings with tailored composition, particle packing, and monolayer thicknesses. We showed how convective assembly can be used to make thin nanoporous films of photoreactive cells surrounded by high Tg, latex polymer particles that offer several advantages, including enhanced cell stability and coating adhesion, increased reactivity, minimized diffusion resistance to nutrients, and reduced light scattering. We demonstrated that such coatings can be fabricated on a continuous basis on glass or flexible polymer sheet substrates and identified the key process parameters controlling the thickness and structure of the biocomposite layers. Preliminary results show stable photohydrogen production from acetate by biocomposite latex coatings containing Rsp. palustris CGA009 deposited using continuous convective assembly and incubated under anoxygenic conditions (argon atmosphere). The immobilized cells maintained their photosynthetic reactivity over the entire incubation period, producing hydrogen (without nutrient addition) both prior to and after transfer to fresh anaerobic tubes. We model coating surface coverage as a function of such critical deposition parameters as particle size, net particle charge, particle sedimentation rate, and coating knife speed, as a means of optimizing light absorption and hydrogen production efficiency in multi-layer flexible biocomposite stacks.
10:30 AM - T6.3
Mussel Inspired Polymer Coated Polyethylene Separators for High Performance Li Ion Batteries
Myung-Hyun Ryou 2 Jang Wook Choi 1
1Korea Advanced Institute of Science and Technology Daejeon Republic of Korea2Korea Advanced Institute of Science and Technology Daejeon Republic of KoreaShow Abstract
While the development of advanced electrode materials and structures is leading Li ion battery technology these days, the development of outstanding separators also improves the cell performance remarkably. Inspired by musselsâ?T exceptional wet-resistant holdfast onto versatile substrates, in this study, we coated polyethylene (PE) separators with mussel inspired polydopamine layers. After the polydopamine coating, PE separators become hydrophilic and thus bring various advantages in the cell operations: 1) the enhancement of power performance, 2) the adaptability with a wider range of electrolyte, particularly polar solvent for low temperature operations, 3) homogeneous Li ion flux that makes the cell operation more stable, especially for larger-scale cells and Li metal anodes. 4) the improved resistance against thermal shrinkage. While bringing a number of advantages, the coating process does not sacrifice original advantages of PE separators at all. This study suggests that mussel-inspired materials can contribute significantly to the improvement of emerging energy storage technology.
10:45 AM - T6.4
Creating Homeostasis in Synthetic Materials via Self-regulating Chemo-mechano-chemical Systems with Built-in Feedback Loops
Ximin He 1 2 Michael Aizenberg 2 Olga Kuksenok 3 Lauren Zarzar 4 Ankita Shastri 4 Anna Balazs 3 Joanna Aizenberg 1 2 4
1Harvard University Cambridge USA2Harvard University Cambridge USA3University of Pittsburgh Pittsburgh USA4Harvard University Cambridge USAShow Abstract
Living organisms maintain tight control over their internal environment through homeostatic systems operating from the molecular and nanoscale up. Such functions are fundamentally enabled by intricate, reversible chemical-mechanical energy conversion processes that are organized to generate hierarchical self-regulated feedback loops. In contrast, most artificial systems cannot self-regulate at all or rely on energy-intensive motors, computers, and accessories. Applying the concept of homeostasis to the design of autonomous materials would have transformative impact in areas ranging from medical implants that help stabilize bodily functions, to energy-efficient buildings that self-regulate thermal flow. Here we present a completely new and highly versatile strategy for creating self-regulating, self-powered, homeostatic materials capable of precisely tailored chemo-mechano-chemical feedback loops at the nano/microscale. We design a broad-based system with hydrogel-supported microstructures separated from a reactant-containing â?onutrientâ? layer. Reconfiguration of the gel in response to a stimulus induces the reversible actuation of the microstructures serveing as a highly precise on-off switch for chemical reactions. We apply this design to demonstrate chemo-mechano-chemical coupling, which triggers a variety of exemplary reactionsâ?"ranging from inorganic or organic to even complex biochemical processesâ?"that undergo reversible, repeatable cycles synchronized with the motion of the microstructures and the driving chemical stimulus. Ultimately, we create a self-sustained homeostatic system that maintains a user-defined temperature by exploiting a continuous feedback loop. The experimental results were validated using computational modeling that qualitatively captured the essential features of the self-regulating behavior. This design is not only novel but is also extremely customizable due to the broad choice of chemistries, tunable mechanics, and physical simplicity, thus promising exciting applications in self-regulating systems with chemo-mechano-chemical transduction at their core.
11:30 AM - *T6.5
Bioinspired System for Thermal Energy Conversion and Conduction
Tao Deng 1 Shakti Chauhan 1 Peter deBock 1 Pramod Chamarty 1
1GE Global Research Niskayuna USAShow Abstract
As the consumption and demand for fossil fuels drive the fuel cost high, systems and applications that use much less fuels than conventional ones attract significant investment in research and development. One of the major trends in reducing the fuel consumption is the electrification of conventional systems. Automobile industry and aircraft industry, for example, are replacing mechanical components in their systems with electrical components to reduce the fuel usage. As the electrification of these systems intensifies, more and more powers are compacted in confined spaces, thermal energy management becomes a critical issue in maximizing performance of these electrified systems. Thermal energy control is also a serious challenge for high performance computing system, advanced energy storage devices, and photovoltaic systems. This presentation will discuss the issues related to the thermal energy control, and provide examples of solving these issues. Specifically, efficient thermal energy conversion and conduction system based on bioinspired design will be discussed in this presentation. Examples of super thermally-conductive thermal ground plane utilizing bioinspired evaporator and condenser will be presented. Such device is capable of converting and transporting thermal energy at >12g operating conditions. The industrial application and benefits of using such devices and the learnings in developing these applications will also be discussed in the presentation.
12:00 PM - T6.6
Bio-Inspired Slippery Anti-Frost Coating on Aluminum for Energy Efficient Refrigerator Heat Exchangers
Philseok Kim 1 2 Wilmer E Adorno-Martinez 4 Jack Alvarenga 1 Joanna Aizenberg 1 2 3
1Harvard University Cambridge USA2Harvard University Cambridge USA3Harvard University Cambridge USA4University of Puerto Rico San Juan Puerto RicoShow Abstract
Frost and ice formation and accretion are serious economic and safety issues for many essential infrastructures, such as aircrafts, power lines, turbines, ships, and telecommunications equipment, as well as in many household appliances such as refrigerators and freezers. Modern â?~frost-freeâ?T refrigerators use a built in electrical heater to remove frost 4-6 times a day with 20-30 minutes of active heating during each defrost cycle, which imposes a significant amount of capital and energy cost. To address this problem, we have developed a coating method on industrially relevant metals, such as aluminum, with nanostructured materials that can change the wetting properties of the surface, delay frost formation, and facilitate removal of accumulated frost. Conductive polymers offer ample opportunities to fine tune nanoscale morphology through variations in the synthesis conditions. Preliminary results show that electrodeposited nanostructured polypyrrole coating on an aluminum surface can significantly delay frost formation compared to uncoated aluminum. We have combined this coating method with a newly developed bio-inspired slippery surface technique, SLIPS (Slippery Liquid Infused Porous Substrates), where a thin liquid layer is locked in a porous substrate to keep the surface slippery to almost any material. We are characterizing these coatings to understand basic physical properties such as contact angles, surface morphologies, thermal properties, and adhesion properties along with their anti-frosting and de-icing behavior under various simulated cooling and heating conditions that refrigerator heat exchangers regularly encounter. These studies will provide basic understanding for the mechanisms associated with the ice nucleation and anti-icing behavior on such surface coatings. We envision that further studies and development of this low-cost and scalable approach will lead to robust icephobic coatings that can significantly reduce the energy and capital cost currently needed in refrigeration industry. An estimated estimated savings of ca.10-100 trillion BTU/yr (equivalent to $10 billion/yr, if $0.1/kWh) if the length and the number of defrost cycles can be reduced to 20% of what is currently implemented in most frost-free refrigerators.
12:15 PM - T6.7
Self-cleaning Superhydrophobic Glass for High Performance Solar Cells
HyoJin Gwon 1 Seok-Jin Yoon 1 Ho Won Jang 1
1Korea Institute of Science and Technology Seoul Republic of KoreaShow Abstract
Nonwettable surfaces with high water contact angles and facile sliding of water drops, called superhydrophobic, have received tremendous attention in recent years. Superhydrophobic surfaces of materials are defined as nonsmooth surfaces on which water drops have contact angles higher than 150 Â°C with only a few degrees of contact angle hysteresis. A key challenge in making superhydrophobic surfaces is to tailor the morphology of the surface in nanoscale, which typically involves synthesis and fabrication of materials at nanometer dimensions. A self-cleaning effect developed through the use of a superhydrophobic surface could be used for solar cell. Incident light onto solar panel is lost both through reflection at the first air/glass interface of the cover glass and through scattering or absorption by accumulated dust on solar panels. While simple antireflective coatings on the glass can help alleviate reflection, the problem of dust accumulation on module surfaces over time remains. That loss may range as high as 25~30% in some areas. Regularly, the surface is cleaned to prevent the reduction of the generating efficiency of solar cells. But the cleaning of a solar panel costs more than the profit that can be obtained by cleaning. For this reason, developing self-cleaning glass surface is very urgent for solar cells industry. In this study, facile methods to achieve nanostructured glass surface which reduces light reflection at the air/glass interface and causes a self-cleaning effect are presented. The surface roughness could be manipulated and superhydrophobic surfaces with different morphology could be generated. The resulting superhydrophobic glass exhibits a high water contact angle ( >150Â°). Superhydrophobic glass has around 90 percent of transmittance and has a low reflection ( >4Â°) in the visible light. We will discuss the formation of surface nanostructures on glass using the methods in detail and explain its influence on superhydrophobic and antireflective properties of the surface. In addition, we will show videos that our superhydrophobic glass removes dust on the surface very effectively.
12:30 PM - T6.8
Design of Conductive CNT-doped Silica Matrices as Hosts for Cell Encapsulation
Benjamin Le Ouay 1 Emmanuel Flahaut 2 Thibaud Coradin 1 Christel Laberty-Robert 1
1Universiteacute; Pierre et Marie Curie (Paris 6) Paris France2Universiteacute; Paul Sabatier Toulouse 3 Toulouse FranceShow Abstract
Immobilization of living cells into solid matrices is a very promising methodology for the realization of bioreactors, providing them a better stability and an improvement of their productivity. Encapsulation in silica gels obtained through the sol-gel process is a simple, versatile and efficient method to immobilize cells in a transparent, porous, non-toxic and resistant matrix. However, the lack of electronic conductivity of silica is a strong limitation when electrochemical devices are targeted. In this work we demonstrate that it is possible to design conductive cytocompatible gels based on the silicification of carbon-based networks. Two different approaches were explored: (i) induction of silica gel formation within the porosity of graphite felt electrodes and (ii) formation Carbon NanoTubes (CNT)-doped silica matrix. Based on our previous work, the silica gel was formed using aqueous silica precursors. In the first situation, the silicification process did not perturb the conduction properties of the felt. Following the second approach, the CNTs network provided an electronic conductivity over a percolation threshold of 0.17 wt.%. The conductivity reached a maximum of 5.10-2 S/m at a doping rate of 0.80 wt.%. Impedance spectroscopy was used to differentiate the electronic phenomena occurring through the CNT network from the phenomena related to the migration of NaCl in isoosmolar concentration within the mesoporous silica network. A model was established to provide quantitative values of the different physical parameters, and the evolution of the gel was studied. In a step further, Escherichia coli bacteria were used as a model organism for the encapsulation experiments. Once the cells have been immobilized, the gel can be placed in contact with a nutritive medium, so that the nutrients can diffuse through the mesoporosity and be metabolized. The encapsulation of cells within a solid hinders their capability to divide. Survival of E. coli was studied by monitoring of the consumption of glucose in the supernatant. The excretion of electroactive metabolites was monitored using cyclovoltametry. These data constitute a solid basis for the future development of a novel type of biofuel cells.
12:45 PM - T6.9
A Microfluidic Enzymatic Biofuel Cell Based on Carbon Micropillar Electrode Arrays
Yin Song 1 Varun Penmatsa 1 Chunlei Wang 1
1FIU Miami USAShow Abstract
Miniaturized enzymatic biofuel fuel cells utilizing biochemical energy sources in living organisms by enzyme-modified electrodes has the potential for use in applications such as implantable medical devices and portable electronics which need small-scale power source. Recently, microfluidic technologies and biological materials have been paired to develop on-chip, green energy biofuel cell systems. Microfluidic fuel cells, also called membraneless fuel cells, provide an alternative avenue towards miniaturizing power supplies. The advantages of microfluidic fuel cells are the relatively low rates of diffusive mixing and colaminar microfluidic flow to maintain the separation of anolyte and catholyte streams flowing side-by-side, thereby eliminating the need of a physical barrier. In this study we present a microfluidic enzymatic biofuel cell design employing 3D carbon micropillar electrode arrays with high-surface area, high aspect ratio. Glucose oxidase and laccase will be immobilized on the anode and cathode, respectively. The 3D electrode setup will be integrated in a microfluidic channel with colaminar flow of glucose and oxygen as fuel. In our computational modeling, the performance of the microfluidic biofuel cell based on finite element analysis aimed at optimizing the length and spacing of electrodes within a microchannel and the thickness of the diffusion layer are studied. For experimental work, we perform the surface functionalization on pyrolyzed photoresist electrode surface and immobilize glucose oxidase and laccase covalently on anode and cathode, respectively. The effort on obtaining the optimum microfluidic biofuel cell configuration, developing reliable covalent bonding for immobilization as well as microfluidic enzymatic biofuel cell performance will be presented in this talk.