1. Sustainable Molecular Organogels: Thixotropic Gelator Systems for Next-Generation Fuels
Julian Silverman*, George John
A multifunctional small molecule capable of gelling a variety of liquids has been synthesized from natural renewable resources. The gelator is derived biodiesel, a waste product and fuel and successfully gelates mixtures of diesel and biodiesel which are sold as sustainable fuels. The gels of these mixtures prove to be strong gels up even with exceedingly low (<1%) concentrations of the gelator in solution. These mixture may serve as potential alternatives to liquid fuels which are known to spill and cause ecological devastation in environmental disasters. We show that the development of alternatives to conventional fuels does not have to sacrifice functionality for sustainability by following the principles of green chemistry in their design. Furthermore these gel systems are shown to be thixotropic in nature which allow them to transition between the gel and liquid state thus offering the versatility and variety of properties as functional smart materials. The development of fuels incapable of spilling may lead to the prevention of oil and fuel spills in a simple and effective manner. These materials may be used for a variety of applications due to their functionality in cosmetic and personal care applications to food based on their bioderivation and sustainable nature.
2. Characterization of Iron Nano Particles using Synchrotron X-rays
Sunil Dehipawala*, Rahel Steffen, Pubudu Samarasekara, Rasika Dahanayaka
Queensborough Community College
Nanometer scale iron particles have a variety of technological applications. They are vastly utilized in optical and microwave devices. Thin films with varying compositions of iron (III) nitrate and ethylene glycol were deposited on glass substrate using the spin coating technique. The thicknesses of the films were controlled by the spin rate. Precursor films on the substrate were then annealed to different temperatures ranging from 200oC to 600oC for 1-3 hours in air. The microstructures of iron particles in films prepared under different conditions were investigated using Extended X-ray Absorption spectroscopy(EXAFS) and X-ray Absorption Near Edge Structure(XANES). The main absorption edge peak position and pre-edge energy position were identical in samples with different numbers of layers, but prepared under similar conditions. This indicates that there was no change in the charge state of the iron regardless of the number of layers. However the intensity of the pre-edge feature decreases as the number of layers increases, which shows a decrease of Fe-O compounds as the number of layers increases.
3. Two-dimensional X-ray Diffraction Characterization of (Zn,Cd,Mg)Se Wurtzite Layers Grown on Bi2Se3
L.C. Hernandez-Mainet*, Z.Chen, T. A. Garcia, A. B. Bykov, L. Krusin-Elbaum and M.C. Tamargo
The wurtzite structure of ZnSe, Zn0.49Cd0.51Se and Zn0.23Cd0.25Mg0.52Se layers grown on Bi2Se3/sapphire (0001) by Molecular Beam Epitaxy (MBE) is reported. Structure characterization is studied by two-dimensional X-ray diffraction. Pole figures are calculated for cubic and hexagonal planes of the (Zn,Cd,Mg)Se family and compared to their expected values. The targeted wurtzite plane was (11-22), while the cubic ones were the (220) and (311). The results show that, under our MBE growth conditions, ZnSe, Zn0.49Cd0.51Se and Zn0.23Cd0.25Mg0.52Se layers prefer to form the hexagonal (wurtzite) phase rather than the cubic one when grown on Bi2Se3/sapphire in (0001) direction. These results have implications for the next generation devices combining semiconductors and topological insulator materials.
4. Strain compensated CdSe/ZnSe/ZnCdMgSe quantum wells as building blocks for near to mid-IR intersubband devices
Joel De Jesus*, Guopeng Chen, Luis C. Hernandez-Mainet, Aidong Shen and Maria C. Tamargo
In order to increase the conduction band offset of the ZnCdMgSe-based material system we studied the incorporation of strained CdSe layers to obtain deeper quantum wells for shorter wavelength intersubband transitions than those obtained in structures lattice-matched to InP substrates. Five CdSe/ZnSe/ZnCdMgSe multiquantum wells (QW) samples grown by molecular beam epitaxy are studied in detail by transmission electron microscopy (TEM), X-ray diffraction (XRD), cw-photoluminescence (PL), and Fourier Transform Infrared (FTIR) absorption experiments. TEM and XRD results confirmed good structural quality of the samples. All the multi-QW PL energies were below the ZnCdSe lattice-matched to InP alloy bandgap (2.1 eV), which serves as ?rst evidence of having achieved deeper quantum wells. FTIR absorptions of wavelengths from 3.83 to 2.56 microns were measured, shorter than those achieved by the lattice matched system. Simulations based on these results predict that absorption of wavelengths as low as 2.18 microns can be obtained with these materials.
5. Growth and Characterization of type-II ZnCdTe/ZnCdSe Submonolayer Quantum Dots for Efficient Intermediate Band Solar Cells
Siddharth Dhomkar*, Uttam Manna, Joel De Jesus, Thor A. Garcia, Vasilios Deligiannakis, Haojie Ji, I. C. Noyan, Maria C. Tamargo, Igor L. Kuskovsky
The Graduate Center and Queens College
Intermediate band (IB) solar cells (SCs), having an IB of states within the bandgap of the host semiconductor that enhances the light absorption without reducing the open circuit voltage, are substantially more efficient than single-gap devices. The IB can be fabricated using quantum dots (QDs) embedded in the host semiconductor, however, there are many growth and material issues related to fabrication of practical devices. We tackle some of the key problems by growing type-II ZnCdTe/ZnCdSe submonolayer QD system via migration enhanced epitaxy. We present results of high resolution x-ray diffraction based reciprocal space map studies, complemented by photoluminescence, showing that this material system is an excellent candidate for IBSCs. Specifically, we show that samples with larger Te fractions have larger QDs with increased vertical correlation. The vertical correlation is particularly important to have sufficient overlap of the hole wavefunctions, to facilitate the IB formation in this material system. Moreover, we are currently working on improvement of the growth parameters to obtain appropriate carrier transport properties that are crucial for an actual device. Detailed investigations are underway to attempt growth and fabrication of a p-i-n solar cell as a proof of the concept.
6. Enhanced linear and nonlinear optical properties of monodispersed silver nanoparticles
Pemba T. Lama*, Anatoliy Suslov, Ardie D. Walser and Roger Dorsinville
City College of New York
Optical properties of monodispersed silver (Ag) nanoparticles (NPs) fabricated using heterogeneous condensation technique were studied and compared with polydispersed Ag NPs. A strong plasmon resonance was observed for the monodispersed Ag NPs due to the coherent oscillations of the conduction band electrons, owing to the uniform size of the Ag NPs. Narrow extinction widths were observed for the Ag NPs compared to the width of the polydispersed Ag sample. Plasmon assisted fluorescence of Rhodamine B dye was also investigated. Higher fluorescence quantum yield was obtained from Rhodamine B when using monodispersed Ag NPs compared to polydispersed Ag NPs. Finally, nonlinear optical characterizations were performed on monodispersed Ag NPs of various sizes using a picosecond Z-scan technique with excitation wavelengths at 532 nm. The nonlinear refraction values were higher for the monodispersed Ag NPs whose surface plasmon resonance (SPR) peak is closer to the excitation wavelength. The higher nonlinear optical response is explained in terms of an electric field enhancement near the SPR.
7. Pointsource Delivery of a Photosensitizer and Singlet Oxygen for Eradication of Glioma and Ovarian Cells In Vitro
Ashwini A. Ghogare*, Imran Rizvi, Tayyaba Hasan, and Alexander Greer
We describe a micro-optic device for pointsource delivery of photosensitizer and singlet oxygen aimed at eradication of brain U87 and ovarian OV5 cancer cells. The device has a mesoporous fluorinated silica tip which photoreleases pheophorbide sensitizer for production of singlet oxygen in the nigh vicinity. The results show escalated photokilling rate and enhanced formation of singlet oxygen about midway through the reaction, which can be attributed to a rapid sensitizer release process via an autocatalytic mechanism. The mass of sensitizer released in the extracellular matrix provides positive feedback to assist in the release of additional sensitizer and singlet oxygen. The photokilling of the glioma and ovarian cells was analysed by global toxicity and live/dead assays, where a killing radius around the tip with ~0.3 mm precision was achieved. The pointsource device inference of these results are discussed for a new PDT tool of hard-to-resect tumors, e.g. in the brain.
8. Dynamics of Quantal Heating in Electron Systems with Discrete Spectra
W. Mayer*, S. Dietrich, S. Vitkalov, A. Bykov
The temporal evolution of quantal Joule heating of 2D electrons in GaAs quantum well placed in quantizing magnetic fields is studied using a difference frequency method. The method is based on measurements of the electron conductivity oscillating at the beat frequency f = f1 - f2 between two microwaves applied to 2D system at frequencies f1 and f2. The method provides direct access to the dynamical characteristics of the heating and yields the inelastic scattering time τin of 2D electrons. The obtained τin is strongly temperature dependent, varying from 0.13 ns at 5.5 K to 1 ns at 2.4 K in magnetic field B = 0.333 T. When temperature T exceeds the Landau level separation the relaxation rate 1/τin in is proportional to T2, indicating the electron-electron interaction as the dominant mechanism limiting the quantal heating. At lower temperatures the rate tends to be proportional to T3, indicating considerable contribution from electron-phonon scattering.
9. Computing the Ideal Strength of Atomically-thin Materials from First Principles
Eric B. Isaacs* and Chris A. Marianetti
Recent ab initio calculations suggest that the ideal strength of graphene is limited by a finite-wavevector phonon instability. In order to understand the origin and generality of phonon instabilities in two-dimensional crystals, we investigate the ideal strength of other monolayer materials including boron nitride (BN), molybdenum disulfide (MoS2), graphane, and silicene with density functional theory calculations. We find a soft phonon mode at the K-point of the Brillouin zone for BN, MoS2, and graphane under equibiaxial tensile strain, leading to mechanical failure for BN and MoS2. While BN and graphane distort similarly to graphene upon mechanical failure, MoS2 undergoes a more complex phase transition with both in- and out-of-plane atomic displacements. We find that the structural transformations for BN, MoS2, and graphane do not result in the opening of a band gap, which indicates that Fermi surface nesting cannot be a universal explanation for phonon instabilities in monolayer materials.
10. Frequency Dispersion of Nonlinear Response of Thin Superconducting Films in the Berezinskii-Kosterlitz-Thouless State
Scott Dietrich*, William Mayer, Sean Byrnes, Jesse Kanter, Sergey Vitkalov, A. Sergeev, Anthony T. Bollinger and Ivan Bozovic
The effect of microwave radiation on the transport properties of atomically thin superconducting LSCO films grown by Molecular Beam Epitaxy were studied. Resistance changes induced by the applied microwaves with variable frequencies (0.01-20 GHz) and powers were measured at different temperatures in the BKT regime (6-15 K). Nonlinear response considerable drop of several orders of magnitude is found above a few GHz. Numerical simulations considering an AC response which follows the DC I-V characteristics of the films replicate the low frequency behavior, but fail at high frequencies. These results indicate that 2D superconductivity is quite resilient to the high frequency radiation because of a strong reduction of the vortex-antivortex dissociation in oscillating 2D superconducting systems.
11. Broadband Coupling of Microwave Signals to Thin Conductors in Cryogenic Systems
Jesse Kanter*, Scott Dietrich, William Mayer, and Sergey Vitkalov
Three techniques are used to determine the microwave (MW) coupling through semi-rigid coaxial lines to samples installed on stages at the bottom of long probes placed in a liquid Helium cryostat. Samples are mounted between the MW delivery line and ground and are placed in parallel with an impedance-matching terminal resistor. One method to determine the delivery of MW signal uses bolometric measurements of the MW power dissipated at the terminal resistor. Another method employs reflection measurements to obtain the reflection coefficient of the sample stage, which is sensitive to variations in sample resistance. A third method initially uses the sample itself as a detector of a small, amplitude-modulated MW signal; the resulting variations of sample resistance are then applied as a calibration factor. Each method appears to reliably measure the actual MW signal delivered to the sample. The presented studies focus on two different electronic systems: GaAs quantum wells and superconducting films.
12. g-Factors of Electrons, Holes and Excitons in Type-II ZnTe/ZnSe Submonolayer Quantum Dots
H. Ji,* S. Dhomkar, J. Ludwig, D. Smirnov, M. C. Tamargo, and I. L. Kuskovsky
Queens College of CUNY
In recent years there has been intense interest in manipulating exciton spin states in semiconductor quantum dots (QDs) for application in spin electronics and quantum information processing. In these applications, the ability to enhance and control Zeeman spin splitting, which can be characterized by g-factors, plays a key role. Here we report our study of the g-factors of electrons, holes and excitons in type-II ZnTe/ZnSe submonolayer QD superlattices. Via analysis of left and right circularly polarized photoluminescence spectra, we determine the g-factor of type-II excitons. We obtain the g-factor of electrons by fitting the temperature dependence of degree of circular polarization. Thus, we find out the g-factor of holes confined in ZnTe QDs. This g-factor of confined holes is larger than those reported for bulk ZnTe. We propose that the enhancement of g-factor of holes is due to quantum confinement which leads to the admixture of the subband states.
13. Quantifying Bulk and Surface Contributions in Nanostructured Water-Splitting Photocatalysts by In Situ Ultrafast Spectroscopy
Kannatassen Appavoo*, Mingzhao Liu, Charles T. Black, Matthew Y. Sfeir
Brookhaven National Laboratory
A quantitative description of recombination processes in nanostructured semiconductor photocatalysts, one that distinguishes between bulk and surface losses, is important to advance solar-to-fuel technologies. Here we discuss a novel methodology, based on in situ ultrafast spectroscopy, that evaluates the bias-dependent quantum yield for ultrafast carrier transport to the reactive interface. This is achieved by simultaneously measuring the electrical characteristics and the subpicosecond charge dynamics of a photoanode in an operating photoelectrochemical cell. Together with direct measurements of the overall incident-photon-to-current efficiency (IPCE), we reveal how subtle structural modifications, not perceivable by conventional X-ray diffraction, can drastically affect the overall photocatalytic activity. We reveal how charge carrier recombination losses occurring on ultrafast timescales (as high as 37% in our model system) limit the overall efficiency, even in nanostructures with dimensions smaller than the minority carrier diffusion length. Our method demonstrates the efficacy of multifunctional designs where high overall efficiency is achieved by maximizing surface transport yield to near unity and utilizing surface layers with enhanced activity.
14. Structure of Nanocrystalline Ti3C2 MXene Using Atomic Pair Distribution Function
Chenyang Shi*, Majid Beidaghi, Michael Naguib, Olha Mashtalir, Yury Gogotsi and Simon Billinge
MXenes are emerging 2-D materials that are extremely promising for applications in electronic and energy storage devices.[1,2] However, due to their nanomaterial nature, it has proven impossible to solve their structures by means of traditional x-ray crystallography. Atomic pair distribution function technique (PDF), on the other hand, is a tool of choice probing the local structure of nanomaterials. Here, we experimentally determined the structure of first produced and mostly studied Ti3C2 MXene, investigated the charge transfer upon intercalation of Na+ and K+ ions based on synchrotron x-ray total scattering data. We believe that current result would be foundational for understanding the physical properties of these materials and possibly facilitating future device applications.
 Science 341, 1502, 2013
 Nat. Commun. 4, 1716, 2013.
15. Measurement of the influence of substrate stretch on endothelial cell by stretchable impedance spectroscopy sensor
Xudong Zhang*, Fang Li, Ioana Voiculescu
An impedance spectroscopy biosensor fabricated on a stretchable substrate has been investigated in this study. The impedance spectroscopy biosensor is based on electric cell-substrate impedance spectroscopy (ECIS) technique, which has been successfully used to monitor the impedance of the membrane of bovine aortic endothelial cells (BAEC). This paper presents the fabrication and testing of electric cell-substrate impedance spectroscopy (ECIS) electrodes on a stretchable membrane. The stretchable membrane integrated with the ECIS sensor can simulate and replicate the dynamic environment of organism and enable the analysis of the cells activity in vitro. Bovine aortic endothelial cells (BAEC) were used in this research because they logically undergo cyclic physiologic elongation produced by the blood circulation in the arteries. This is the first time when ECIS electrodes were fabricated on a stretchable substrate and ECIS measurements on endothelial cells exposed to cyclic strain of 15% were successfully demonstrated.
16. Capillary Attraction Between Two Floating Spheres At A Viscous Oil-Water Interface
Archit Dani*, Charles Maldarelli
City College of CUNY Levich Institute /Steinmann Hall #1
The aggregation rate of floating particles, due to capillary forces, at a fluid/fluid interface has drawn significant interest. This 2D phenomenon plays a critical role in self-assembly processes relevant to pollination in biological contexts, the formation of dense particle laden interfaces in pickering emulsions, froth flotation process in the mining industry and in the bottom up assembly of materials in nanotechnologies. We present first the experiments on the aggregation of two Teflon particles at an interface between a mineral oil and an aqueous phase for different particle sizes, interfacial tensions and oil viscosities. The separation distance, as a function of time, and pair aggregation time are both measured by optically following the movement of each particle. The contact angle at the three phase point of contact is obtained by directly imaging a particle straddling the oil-water interface .The obtained value of the contact angle is compared with a value obtained by means of sessile drop measurement of a water drop on a flat Teflon surface immersed in oil. The observed values of contact angle for the Teflon sphere and that for the flat Teflon plate are not in agreement with each other. This indicates the existence of Contact Angle Hysteresis (CAH). Our theoretical formulation accounts for the observed CAH and obtains a resistance coefficient, which depends on the viscosity ratio of the adjoining fluid phases and the depth of immersion of the particle. The experimental results are in excellent agreement with our theoretical formulation.
17. Coarse-grained Modelling of RNA for Nanotechnology
Petr Sulc*, Flavio Romano, Thomas Ouldridge, Jonathan Doye, Ard Louis
We present a new, nucleotide-level coarse-grained model for RNA, oxRNA, based on the parametrization methodology recently developed for the oxDNA model of DNA. The model is designed to reproduce structural, mechanical and thermodynamic properties of RNA, and is designed to retain the relevant physics for RNA hybridization and the structure of single- and double-stranded RNA. In order to explore its strengths and weaknesses, we test the model in a range of nanotechnological and biological settings. Applications explored include the folding thermodynamics of a pseudoknot, the formation of a kissing loop complex, the unzipping of a hairpin motif, and the thermodynamics and kinetics of RNA strand-displacement reaction. We argue that the model can be used for efficient simulations of the structure of systems with thousands of base pairs, and for the assembly of systems of up to hundreds of base pairs. The source code implementing the DNA and RNA models is released for public use at dna.physics.ox.ac.uk.
18. Melting Gels, and their Anticorrosive Properties
Andrei Jitianu1*, G. Rodriguez1*, A. Degnah2, K. Al-Marzoki2, Jadra Mosa3, M. Aparicio3, L.C. Klein2
1 Lehman College, City University of New York
2 Department of Materials Science and Engineering, Rutgers University
3 Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
Surface treatments with Cr(VI) are a common industrial practice for passivating metals. However, Cr(VI) is a known carcinogen. Replacement of Cr (VI)-containing coatings with new chromate-free anticorrosive coatings is a public health priority. Our studies are focused on alternative passivating materials. Specifically, new silica-based hybrid 'organic-inorganic-melting gels', are being evaluated as anticorrosive materials. The melting gels are non-porous materials obtained by a simple sol-gel process that requires low temperature of thermal treatment, which are easily processed in a variety of compositions. Two important properties of the melting gels that make effective as anticorrosive coatings are first their high hydrophobicity and second their lack of porosity. The hybrid melting gels were synthesized by the sol-gel method using mono-substituted silanes such as methyltriethoxysilane (MTES) and di-substituted silanes such as dimethyldimethoxysilane (DMDES). These melting gels have glass transition temperatures between -0.3 oC and -56.7 oC. Their structure was investigated using FT-IR, 29Si NMR and Raman spectroscopy, while their morphology was investigated using SEM. The anticorrosive properties were investigated on Stainless Steel 304 (ASTM A 240) coated with melting gels using Anodic Polarization and Electrochemical Impedance Spectroscopy.
19. Molecular Modeling of Self-Assembly of Anticancer Drug Amphiphiles
Myungshim Kang*, Honggang Cui, Sharon Loverde
College of Staten Island, CUNY
Recently, drug amphiphiles (DAs) have been shown to form discrete and stable supramolecular nanostructures with high and quantitative drug loading. A drug amphiphile consists of a hydrogen-bonding peptide sequence attached to a hydrophobic drug. Similar to peptide amphiphiles, DAs also self-assemble into discrete and well-defined supramolecular structures. Using molecular dynamics simulations we investigate inter- and intra-molecular interactions driving the self-assembly and formation of the morphology of supramolecular DAs. More specifically, we investigate the self-assembly of camptothecin-based DAs, which have been shown to form cylindrical supramolecular assemblies with a well-defined structure. We examine the self-assembly process from random using long-time all-atomistic molecular dynamics simulations (> 200 ns). We also examine the structure of pre-assembled cylindrical supramolecular assembly, analyzing radial distribution of each component of DAs and Cl- ions in the cylinder. We also characterize π-π stacking using the distribution of distances and angles between the planar CPTs in DA, as well as hydrogen bond formation in the peptide over time. Our findings can help add further insight into the rational design of supramolecular assemblies.
20. Magnetic Behavior of Zinc Nanorods Capped with a Ferromagnetic Metal
Paulina Librizzi*, Roger Chang, Ilona Kretzschmar
This project examines the behavior of zinc nanorods capped at one end with a ferromagnetic metal. These nanorods are fabricated using polycarbonate template-assisted electrodeposition, with the ferromagnetic material grown first. They are larger than the typical nanorod. These rods are 1 micron in diameter and 6 microns in length so that they can be visible under an optical microscope. When magnetized along their long axis, the rods form different networks and arrays in a solution. The goal of this project is to characterize the magnetic behavior of capped nanorods so that the behavior of smaller and thinner capped nanorods can be understood.
21. Modulation of Photoluminescence Lifetime and Blinking in Single CdSe/ZnS Quantum Dot by External Electric Field
Huidong Zang*, Mircea Cotlet
Brookhaven National Laboratory
The charge trapping and de-trapping processes in single CdSe/ZnS nanocrystals under external electric field were systematically studied. The results clearly demonstrated that the external electric field can reversibly modulate the exciton dynamics and photoluminescence blinking. A model which assumes energetically deep charge traps is proposed to explain on/off blinking in isolated CdSe/ZnS nanocrystals with the presence of a permanent dipole moment.
22. Patterning of Conjugated Polymer Thin Films by Water-based Self-assembly
Prahlad K. Routh*, T.A. Venkatesh, Mircea Cotlet
Stony Brook University
Conjugated polymer thin films are widely used in sensors/ photovoltaic applications due to their semiconducting properties. Polymer-based photovoltaic solar cells (OPVs) promise a cost-effective replacement for the more expensive, but currently more efficient opaque silicon-based technology. Despite the low efficiency of OPVs there is a considerable market demand for transparent solar cells in low energy applications. Ordered microporous structures could provide a new route to create cost effective semitransparent films which can be utilized in low energy applications and Building Integrated PVs. Breath Figure Technique (BFT) is a simple method of producing such ordered microporous structures. In this study BFT was applied to a series of commercial conjugated polymer: polythiophene derivatives with varying side chain length. An in-depth study of processing parameters has been carried with the aim of controlling the morphology of the honeycomb film over large, PV relevant areas. Optical and Opto-electronic properties of such patterned films and their effect of morpholgy are studied using SEM, X-ray scattering, AFM, Fluorescence Lifetime Imaging (FLIM) and Spectroscopy Methods
23. Discovery of tri-peptide emulsifiers using combined computational screening and experimental validation
Gary Scott*, Tell Tuttle, Rein Ulijn
University of Strathclyde
Peptide nanomaterials are an important class of material for the food, cosmetic and biomedical industries. Short self-assembling peptides are extremely attractive due to the simplicity and diverse range of interactions that can be seen. Unfortunately, the self-assembling nature is often hard to predict. The use of very short (e.g. di- and tri-) peptides has advantages of cost, scalability and rational tenability however have been largely restricted to hydrophobic dipeptides, such as FF. To date, most self-assembled peptide nanostructures are found serendipitously or by copying/modifying sequences known from biological systems. We are developing computational approaches to enable discovery of new assembling peptides, by predicting their aggregation propensity for tripeptide molecules. We previously reported the use of coarse-grained molecule dynamics (CG MD) as a tool to predict self-assembly behaviour, which led to the discovery of a new class unprotected tripeptide gelators: KYF, KYY, KYW and KFF. The focus of the current work is to further develop this tool coarse-grained molecular dynamics to show that the introduction of organic solvents will allow the creation of emulsified systems. Using CG MD, we show how the introduction of octane into an aqueous system can change the behaviour of the self-assembled peptides. Results show that these tripeptide molecules can act as surfactants, where they assemble at the interface between the octane and water. Experimental methods, such as confocal microscopy, can allow the tracking of these systems, where labelling of the organic solvent with a fluorescent dye allows visualisation of the emulsion system. In addition, spectroscopic analysis (FTIR, fluorescence) is used to assess the peptide arrangements in the emulsions. 3D images can be obtained of the emulsified particles allowing for a size distribution and overall dispersal of the emulsified particles to be obtained. We have therefore shown that CG MD can also be used for the identification of new emulsifiers comprised wholly of short unprotected peptides.
 Gazit, E. et al (2003), Science, 300, 625-627
 Frederix, P. W. J. M. et al (2014), Nat. Chem., 7, 30-37
 Marrink, S. et al (2007), J. Phys. Chem., 111, 7812-7824
24. BioWires: A Pathway for Ag+-mediated, DNA- and RNA-Nanowire Synthesis in Escherichia coli
Simon Vecchioni*, Emily Toomey, Mark C Capece, Shalom Wind, Lynn Rothschild
DNA is an attractive candidate for a biological nanowire due to its linear geometry, definable base sequence and self-assembling properties. Convincing evidence of high electrical conductivity in native DNA has been elusive. We hypothesize that the silver ion incorporation will increase charge mobility, and to that end built core-functionalized DNA nanowires through non-canonical, Ag+-mediated base pairing in oligonucleotide sequences containing cytosine-cytosine mismatches. We demonstrate that Ag+ ions are required for highly-mismatched DNA duplex formation using thermal melting, gel electrophoresis and NMR spectroscopy, and further show that embedded ions are shielded from aqueous reagents. Two functional genetic parts for the synthesis of DNA- and RNA-based, cytosine-Ag+-cytosine (C:Ag+:C) duplexes have been constructed in Escherichia coli, and we demonstrate that dC:Ag+:dC DNA duplexes are capable of polymerization through enzymatic end-ligation. With enhanced stability, ligase-compatibility, and biologically abundant components, we suggest that this synthetic biological approach will allow for cell-based fabrication of nanoelectronic components.
25. Synthesis, Characterization and Biological Studies of High and Low Molecular Weight Hyaluronic Acid-photosensitizer Conjugates as Photo Dynamic Therapy (PDT) Agents
N. V. S. Dinesh K. Bhupathiraju*, C. M. Drain.
Hyaluronic acids are naturally occurring polysaccharides composed of a repeating disaccharide unit of D-glucuronic acid and N-acetyl-D-glucosamine linked via an β-1,3-glycosidic bond. The carboxylate functional groups on every other sugar afford a means to append drugs. High and low molecular weight hyaluronic acids are nano-carriers used as drug delivery agents, wherein the drug can be covalently or non-covalently bound. Hyaluronic acids can direct drugs to cancer, suppression of drug-resistant tumors, cross the blood-brain barrier, treatment of retinal degenerative diseases such as age-related macular degeneration (AMD) and diabetic retinopathy. Although hyaluronic acid porphyrin conjugates were studied, extensive research is still underway and phthalocyanine and chlorin conjugates of hyaluronic acid are not yet reported. This study compares high and low loading of porphyrin, phthalocyanine, and chlorin photosensitizers conjugated to high and low molecular weight hyaluronic acids. The efficient synthesis, chemical characterization, photophysical properties, stability, and assays for photodynamic therapy activity will be presented. The theranostic activity of the porphyrins, phthalocyanines, and chlorins depends on a balance between fluorescence and sensitization of the formation of singlet oxygen. We find that the proximity of the photosensitizers to each other significantly affects the photophysical properties by energy transfer in the excited state, thereby reducing the quantum yield of singlet and triplet states. These are compared to the same sensitizers appended with glucose.
26. DNA-gold Nano-conjugates-based Profiling of Cancerous Cell Lines with Single-particle Mode Mass Spectroscopy
Daniel Liu*, Guojun Han, Sichun Zhang, Xinrong Zhang
We integrated the single-particle mode micro-nebulizer ICMPS with in-house microfluidic fluorescence cytometer for detecting simulated circulated tumor cells in a pool of cultured cells based on the specific affinity of the aptamer to target cell lines. The gold nanoparticle (GNP) conjugated-aptamer bound to particular cancerous cells and generated pulse signal when ICMPS working in the single-particle mode, which statistically correlated well with the microfluidic fluorescence on-line measurement. This novel aptamer-based single-cell mode ICPMS paved the way for future studies in biomedical areas.
27. Near Infrared Single Particle Microscopy of Charge Transfer in PbS/CdS Nanocrystals
Huidong Zang, Prahlad Routh, Mircea Cotlet*
Brookhaven National Laboratory
Near-infrared Single Particle Spectroscopy of Lead Sulfide/Cadmium Sulfide Nanocrystals Mircea Cotlet, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973. The detection and identification of single molecules/single nanocrystals by optical methods has been demonstrated over two decades ago by Moerner, Keller, Orrit, Bawendi and others. The impact of single particle methods on both life science and materials science research and related discoveries have been acknowledged this past year by Nobel Prize in Chemistry to W.E. Moerner of Stanford University for his pioneering work in low temperature single particle detection. Colloidal nanocrystals or quantum dots (QDs) have appealing properties for photovoltaics (PVs) like high extinction coefficients, size-tunable bandgap and photoluminescence (PL), the ability to undergo multiple exciton generation. Combined with acceptor materials like carbon nanotubes, conductive polymers and/or transition metal oxides, QDs are explored as cost-effective, high performance active materials for PVs. Visible absorbing/emitting QDs like CdSe have been intensively studied with single particle optical methods, and they sum up the bulk (99.99%) of single nanocrystal optical studies. Challenges remain when it comes to the detection of optical signals from isolated QDs absorbing/emitting in near infrared (NIR). Low bandgap, NIR-emitting QDs like PbS have been so far the subject of just two single nanocrystal optical studies from Bawendi (MIT) and Krauss (Rochester) groups. Our group has recently developed time-resolved NIR single particle spectroscopy methods that can detect and identify isolated PbS/CdS QDs by their photoluminescence and probe the dynamics of photoinduced charge transfer (CT) from hybrids composed on PbS/CdS QDs and metal oxides like TiO2 and conductive polymers like PEDOT:PSS. In particular, we will show how NIR single particle methods can unravel heterogeneity in (radiative) recombination of electron and hole in the PbS core following optical excitation, and how this heterogeneity is dramatically suppressed in the presence of charge transfer, either electron or hole.
28. Directing Peptide Self-assembly Using Sound Waves.
Charalampos Pappas* and Rein V. Ulijn
University of Strathclyde/CUNY ASRC
Molecular self-assembly plays a key role in biological processes and provides a versatile approach for materials fabrication. In chemists hands molecular self-assembly appear to act as ideal protagonists for molecular recognition, detection and adaption to the environment. Molecular self-assembly can be controlled using a variety of stimuli including chemical, physical and mechanical triggers. Recent reports have shown that ultrasound (>1MHz) may be used to control self-assembly and gelation process. These studies involve high energy pressure waves with high frequencies (>1MHz) and control gelation causing different effects on the structure and properties. Recently Aida and his co-workers published a vertical alignment of nanofibres in solution upon audible sound irradiation, the frequency of which is much lower (20-20,000 Hz). It is the objective of this study to systematically investigate the effects of (ultra) sound on molecular self-assembly. We have demonstrated that upon audible sound irradiation (100-1000 Hz) the spherical aggregates of the aromatic dipeptide Fmoc-Tyr-Asp-OH undergo under supramolecular reorganization as evidenced by fluorescence, DLS and AFM microscopy. The results provide a first step towards rational use of sound to control and direct molecular self-assembly.
29. Grafting of Poly(oligoethylene glycol)(meth)acrylate Brushes from Nanopore Surface via Atom Transfer Radical Polymerization with Activators Regenerated by Electron Transfer
Amanpreet S. Manchanda* and Michal Kruk
The Graduate Center, City University of New York and College of Staten Island, City University of New York
Atom transfer radical polymerization with activators regenerated by electron transfer is a facile approach to graft poly(oligoethylene glycol) (meth)acrylate brushes on the surface of cylindrical mesopores of ordered silicas. Poly (2-(2-methoxyethoxy)ethyl methacrylate) (PMEO2MA), poly (oligo(ethylene glycol) methacrylate) (POEGMA) and poly (MEO2MA-co-OEGMA) brushes were grafted on the surface of ultra-large-pore SBA-15 silica using surface-initiated activators regenerated by electron transfer (ARGET) atom transfer radical polymerization. Loading of polymers can be controlled over a wide range by changing the polymerization time. High loadings of polymers (up to ~34 wt. %) were achieved without the pore blocking. The resulting nanoporous materials were characterized by thermogravimetry, nitrogen gas adsorption, Fourier transform infra-red spectroscopy (IR), small angle X-ray scattering (SAXS).
30. Probing Cellular Response to Heterogeneous Rigidity at the Nanoscale
Jinyu Liao*, Manus J. P. Biggs, Shalom J. Wind
Physical factors in the environment of a cell regulate cell function and behavior and are involved in the formation and maintenance of tissue. There is evidence that substrate rigidity plays a key role in determining cell response in culture. Previous studies have demonstrated the importance of rigidity in numerous cellular processes, including migration and adhesion and stem cell differentiation. Atypical response to rigidity is also a characteristic of transformed (cancerous) cells. A cell encounters features of different size and stiffness in its environment. Thus, it is important to understand how cells sense rigidity, particularly in the context of tactile cell sensing of discrete localized areas of increased or decreased rigidity. We have developed a new technique for the creation of biomimetic surfaces comprising regions of heterogeneous rigidity on the micro- and nanoscale. The surfaces are formed by exposing an elastomeric film of polydimethylsiloxane (PDMS) to a focused electron beam to form patterned regions of micro- and nanoscale spots. Finite element analysis of nanoindentation measurements performed on irradiated PDMS films show that in a thin layer near the film surface, where approximately 90% of the electron energy is absorbed, the Young's modulus of the elastomer undergoes a significant increase as a function of electron beam dose. Human skeletal stem cells plated upon PDMS electron beam-exposed in a pattern of spots with diameters ranging from 2 µm to 100 nm displayed differential focal adhesion co-localization to the exposed features, with the degree of co-localization depending on both rigidity and feature size. This behavior persisted as the area of the exposed regions was reduced to ~1 µm. On spots with diameters of ~ 250 nm and below, focal adhesion co-localization was lost, and cells appeared unable to identify the rigid spots. This implies that there exists a length scale for cellular rigidity sensing, with the critical length in the range of a few hundred nanometers.
31. Time Resolved Kerr Rotation Studies of Te-isoelectronic Centers in ZnSe Spacer Layers of ZnSe/ZnTe Type II Quantum Dot Structures
V. Deligiannakis*, S. Dhomkar, D. Paglieroa, H. Ji, B. Roy, M. C. Tamargo, C. A. Meriles, I. L. Kuskovsky
The City College of New York
Three-dimensionally confined structures such as quantum dots (QDs) have been of considerable interest due to their ability to closely imitate isolated atoms on mesoscopic length scales. Recently, single impurity states in bulk semi-conductors have also attracted attention due to their ability to optically address quantum states. Here we show results pertaining to the optical and spin properties of type-II sub-monolayer ZnTe QDs embedded in a ZnSe matrix. Samples were grown by a combination of molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE) in which dot formation was created by exposure of the sample surface to alternating Zn and Te fluxes. Samples were grown on (001) GaAs substrates with a 70 nm buffer of ZnSe. Photoluminescence studies show two prominent bands centered around 2.5 eV (green band) and 2.7 eV (blue band) at low temperatures. The green band has been correlated with the contribution from QDs, while the high energy blue band is attributed to contributions from the ZnSe spacer including Te isoelectronic centers present in them. Time resolved Kerr rotation (TRKR) measurements were performed using pump-and-probe pulses from a tunable mode-locked Ti:sapphire laser, with a pulse width of 130 fs and a repetition rate of 76 MHz. The light was frequency doubled using a BBO crystal and the pump and probe pulses were degenerate in energy. Attempts to probe the dots directly via the green band did not show any results most likely due to the weak oscillator strength of this transition resulting from their type-II nature. Centering the pump and probe pulses around the band edge of ZnSe (blue band) we were able to address the spin dynamics of Te-isoelectronic centers present in the spacer layer. Results show that the T*2 lifetimes exhibit a bi-exponential decay and persist up to 13 ns. Further measurements will be done on samples with varying Te concentration, as well as a function of the applied magnetic-field to understand the spin properties of this defect.
32. MMP-9 Responsive Peptides for Tumor Associated Formation of Doxorubicin-releasing Nanofibres
Daniela Kalafatovic*, Max Nobis, Kurt I. Anderson and Rein V. Ulijn
CUNY Advanced Science Research Centre (ASRC)
Expression levels of enzymes dictate the difference between health and disease in many cases, including cancer. This leads to explore strategies to incorporate enzyme sensitivity in materials where the goal is to achieve dynamic and targeted changes in material properties. Peptide amphiphiles were designed, that upon cleavage by a disease-associated enzyme reconfigure from micellar aggregates to fibres. Upon this morphological change, a doxorubicin payload could be retained in the fibres formed, which makes them valuable carriers for localised formation of fibre depots for slow release of hydrophobic anticancer drugs. The designed PhAc-FFAGLDD and GFFLGLDD and its expected product of enzyme cleavage PhAc-FFAG and GFFLG were synthesized and characterized by AFM, FTIR, DLS, rheology and fluorescence. After the designed peptides were shown to be successful for controlling the morphology of the supramolecular aggregates based on the peptide length i.e. hydrophobicity, the enzyme triggered micelle to fibre transition was explored. Following this it was investigated whether the micelles were capable to perform as mobile vehicles for encapsulation and release of hydrophobic drugs. It was observed that the assembled fibres provide a new scaffold for prolonged drug delivery due to the partial entrapment of the drug and the intrinsic biodegradable nature of peptide carriers themselves. Being purely peptidic these systems have the advantage of being not toxic to cells (MTT assay) and can be used as carriers for doxorubicin in vivo. When tested on animal models, the cancer growth in slowed down by administration of doxorubicin loaded peptides compared to doxorubicin only. This approach opens up the possibility of developing new (enzyme responsive) drug delivery vehicles designed to release drug payload only in the presence of the desired enzyme with potential application in cancer therapy.
33. Nucleation, Growth, and Kinetic Studies of Cadmium and Tellurium
D. Chaykina*1, V. N. Matubia1, M. Osial2, J. Widera1 and K. Jackowska2
1 Adelphi University, Garden City, NY, USA
2 University of Warsaw, Warsaw, Poland
The nucleation and growth of cadmium and tellurium was studied on glassy carbon substrate at 22 oC. Cadmium telluride (CdTe) is an important material for solar cell technology. A novel method for the deposition of CdTe was developed by our group to produce thin films that have the potential to be used in solar technology. In order to be able to better control the synthesis of these thin films, to design and control their properties at the molecular level, the kinetic parameters as well nucleation and growth mechanism of cadmium and tellurium deposition must be studied. Cyclic voltammetry was used to determine the diffusion coefficients of the two species. For cadmium the diffusion coefficient was 2.30*10-6 cm2/s and for tellurium it was 2.66*10-6 cm2/s. Based on i/t chronoamperammetric curves the mechanism of nucleation of both cadmium and tellurium was determined as being progressive. This conclusion was supported by AFM and SEM imaging. Keywords: cadmium; tellurium; nucleation and growth; cadmium telluride thin films; solar cells.
 Osial M., et al. Solid State Electrochem. 2013, 17, 2477-2486
34. Toward Suantum Spintronics in Diamond
Jacob Henshaw*, Remus Albu, Marcus Doherty, Carlos A. Meriles
CUNY-City College of New York
Key to future spintronics and quantum information processing (QIP) is the preparation, transport and measurement of spin in a solid state platform. Diamond is an ideal spintronics material: its variety of paramagnetic defects are sources and detectors of spin; its large bandgap, inversion symmetry, and small spin-orbit and spin-lattice interactions promise long spin relaxation times and transport distances. Furthermore, diamond has proven quantum applications, including the realisation of spin qubit registers. The connection of these registers by a quantum channel is a major unresolved problem in solid state QIP. Yet, virtually no spin transport measurements in diamond have been reported. Here we describe initial work on the use of optical excitation and microwave manipulation to initialize and inject spin-polarized electrons into the diamond conduction band. Alternate forms of optical and electrical detection of the electron diffusion length and spin relaxation time are discussed along some initial experimental results.
35. Protein Adsorption on Silica Nanoparticles and Oxidized Silicon: Effect of Surface Chemistry
Bikash Mondal*, QianFeng Xu, Mark Barahman, Alan M. Lyons
Graduate Center, City University of New York
Design of a protein repellent, biocompatible nanoparticles as well as flat surfaces have been explored for various application in pharmaceutical, agriculture and food processing. Surface chemistry and wettability of the surfaces play an important role in biocomaptibility, especially the adsorption of proteins. Silica nanoparticles, with individual particles size of 10-20 nm, and oxidized single crystalline silicon surfaces were modified to render them either hydrophilic or hydrophobic. Hydrophilic surfaces with different surface chemistries were prepared by attaching: a) polyethylene glycol silane (PEG) (Mw: 590-650) or b) a zwitterionic siloxane (sulfobetainesiloxane or SBS) to the surface. Hydrophobic surfaces were prepared by coating the nanoparticles/oxidized silicon with dimethyl dichlorosilane (DMDCS) via a chemical vapor deposition method. Modified surfaces were characterized by Raman spectroscopy, thermogravimetric analysis (TGA) and contact angle goniometry. Protein adsorption on the different nanoparticles was studied by UV-Vis spectroscopy using bovine albumin serum (BSA) and fibrinogen as model protein. On oxidized silicon surface XPS, confocal microscopy and contact angle measurements were used to characterize protein adsorption as a function of time. Maximum protein adsorption was observed on hydrophilic silica surfaces whereas almost no protein adsorption was observed on PEG and SBS coated hydrophilic silica surfaces. Due to the non-wetting nature of the hydrophobic nanoparticles, almost no protein adsorption was detected as the particles do not disperse in aqueous solutions. To overcome this limitation, flat silica surfaces were prepared with the same chemistry and wettability showed intermediate amounts of protein adsorption. Coating of hydrophilic silica nanoparticles and oxidized silicon with PEG or SBS was shown to be an effective approach to design biocompatible protein repellent surfaces without affecting the initial wettability.
36. Synthesizing and Self-Assembling a Periodically Sequenced Polypeptide
Matthew B. Kubilius*, and Raymond Tu
City College of New York
Synthesizing a periodically-sequenced, useful, amphipathic peptide is challenging due to the polydispersity index increases of large molecular weight polypeptide systems. To overcome this, we designed synthetic amino acid dimers that are both amphipathic and water-soluble. When polymerized, these dimers give rise to a peptide with alternating hydrophilic/hydrophobic side groups: the typical periodicity for beta-sheet forming polypeptides. Using this approach, we can influence polydispersity in the growing polypeptide chains, controlling the kinetics of growth through transport-limited chain elongation. Our experiments show that in the absence of a micellular interface, standard bulk-phase condensation polymerization occurs. The amphipathic character of the peptide chain increases with increasing molecular weight, resulting in a polypeptide that partitions into surfactant micelles as a function of the degree of polymerization. This type of kinetically-limited growth serves to narrow the polydispersity of our periodically-sequenced polypeptide. We quantify the dynamics of chain elongation and interfacial assembly using multi-angle light scattering and mass spectrometry and define the evolving sheet-like secondary structure using circular dichroism for various peptides of differing amino acid pairs. Our results show that the peptides grown in the presence of micelles show significantly enhanced self-assembly and a narrowed polydispersity index. From this, we conclude that the transport-limited chain elongation polymerization method shows great promise in the manufacture of low-cost, interfacially assembling polypeptides.
37. Activated Carbon-hydroxyapatite Composite Which can be Used as 'Band Aid' in Bone Trauma Surgery
Ebenezer Ewul*1, Emmanuel Calderon2, Mihalela Jitianu2, Andrei Jitianu1*
1 Lehman College, CUNY
2 William Paterson University, New Jersey
Hydroxyapatite (Ca10(PO4)6(OH)2) is a common component of the human bones and teeth. Hydroxyapatite promotes the osteogenesis. Another interesting material is activated carbon cloth which has high mechanical strength, high porosity, flexibility and biocompatibility. Moreover, the carbon is partially 'digested' by the human body through phagocytosis and partial oxidation. In this study we succeed to bring together the hydroxyapatite obtained by sol-gel method and the activated carbon cloth. We succeeded to obtain new composite materials which can be used as a 'band-aid' for bone regeneration in bone trauma surgery. This carbon based 'band-aid' can replace metallic prosthetic bone replacements which are traditionally used in the bone surgery. Using these new materials we hypothesize we can avoid the second surgery which involves the recovery of the metal prosthetic parts. The synthesis of the hydroxyapatite was carried out using the sol-gel method. For this, calcium nitrate hexahydrate (Ca(NO3)2 6H2O) along with phosphorous pentaoxide (P2O5) in 200 proof ethanol were employed. The main advantages of the sol-gel method are that it led to homogeneous hydroxyapatite precursors solutions. Using these solutions we were able to obtain uniform coatings on activated carbon cloth by dip coating. The formation of the hydroxyapatite was identified by X-Ray diffraction. The composite materials obtained were characterized using thermogravimetric coupled with differential thermal analysis (TG-DTA), BET surface area. The uniformity of the coatings was visualized using SEM. The resistance to stress of the carbon cloth before and after coating with hydroxyapatite has been investigated by means of oscillatory rotational rheometry, by performing measurements in a wide stress range, along with time recovery investigations.
38. Use of Proteins in Metal-Binding
Michael Yang*, Jasmin Hume, Raymond Chen, Rudy Jacquet, and Jin Kim Montclare
New York University
Metal templation by proteins is made possible by functionalization of the protein to include specific binding sites capable of crystalizing inorganics. Our lab makes use of two engineered variants of the cartilage oligomeric matrix protein (COMP), dubbed C and Q, as scaffolds for metal templation. In order to functionalize these proteins, we incorporate the unnatural amino acid azidohomoalanine. Azidohomoalanine has the ability to participate in a click chemistry reaction, where the azide group of azidohomoalanine forms a five-membered ring with an alkyne in the presence of a reducing agent. In our experiments, the alkyne is part of a peptide, termed CMms6, which is known to template magnetite (iron oxide) nanoparticles. In this way, we hypothesize that C and Q can assemble magnetic particles, providing the potential for utilization in nanoscale biosensors and electronic devices.
39. Electrodeposition of Cadmium Telluride Thin Films
V. N. Matubia1, D. Chaykina*1, M. Osial2, J. Widera1 and K. Jackowska2
1Adelphi University, NY, USA
2University of Warsaw, Warsaw, Poland
Thin film properties are determined by the used semiconducting material and the applied deposition conditions since they are only nanometers thick. Therefore, the microscopic properties of the materials ought to be considered to optimize their fabrication. Cadmium telluride is one of the leading materials in manufacturing thin film solar cells, owing to its optimal energy band gap range and cheap fabrication costs. However, the cost and ease of fabrication of CdTe cells could greatly be reduced by seeking alternative deposition methods that are more flexible to allow for cheaper manufacture and increase the lifetime of the cells. In previous work, the parameters for optimal one step electrodeposition of CdTe in aqueous medium were determined as: -0.65 V in pH 2, 0.1 M lithium perchlorate solution and 5:1 ratio of Cd to Te ion sources.
Further studies carried out by our group elucidate the nucleation and growth mechanisms involved that validate the optimal results obtained at 22 oC and describe the nucleation, distribution and growth patterns of CdTe deposited under these conditions. The studies were conducted via: cyclic voltammetry, chronoamperometry, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The samples were deposited at: -0.45 V, -0.65 V and -0.80 V for varying times and the nucleation mechanism was determined to be progressive.
 Osial M., Widera J., Jackowska K., J. Solid State Electrochem. (2013) 17:2477-2486
40. Energy Conversion in Biological Objects at the Nanoscale
A. Smirnov, F. Nori, D. Kaur, and L. Murokh*
Queens College of CUNY
Proton gradient across a lipid membrane is a common intermediate form of the energy storage in biological systems, which is subsequently converted into a proton current, mechanical energy of rotational bionanomotor, and, finally, into the most stable energy of chemical compounds. Even in a single physical system, inner mitochondrion membrane, there is a variety of mechanisms pumping protons across the membrane, therefore converting the energy of high-energetic electrons into the proton gradient. In this presentation, I discuss our models of the proton-pumping Complexes cytochrome c oxidase, NADH dehydrogenase, and cytochrome c reductase. I also adress the principles of operations of the proton-driven bionanomotor. In all cases, we use methods of condensed matter and statistical physics to derive quantum equations of motion to describe the processes in these biological systems.
41. Imaging Thermal Conductivity with Nanoscale Resolution via a Scanning Spin Probe
Abdelghani Laraoui*, Halley Aycock-Rizzo, Xi Lu, Elisa Riedo, and Carlos A. Meriles
City College of New York
The understanding of heat transport processes at the nanoscale is a subject of fundamental and technological importance that largely relies on our ability to measure temperature with high-spatial and temporal discrimination. Here we use a diamond-nanocrystal-hosted nitrogen-vacancy (NV) center attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip to a predefined operating temperature and rely on the NV to monitor the small thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. With the aid of a combined AFM/confocal setup, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. Given the small mass of the NV-hosting diamond nanoparticle, our technique shows a fast time response (of order 100 µs), limited by the heat-up and cool-down times of the tip. The ability to peer into the nanoscale heat flow of a target material promises multiple applications ranging from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions and chemical reactions in various solid-state systems.
42. Plasmonic Nanohole Arrays for Photovoltaic Applications
Andreas C. Liapis*, Matthew Y. Sfeir, and Charles T. Black
Brookhaven National Laboratory
Surface plasmon polaritons are collective charge oscillations coupled to photons at the interface between a metal and a dielectric. When structured appropriately, thin metal films exhibit surface plasmon resonances that drastically alter their optical properties. Such resonances can be exploited to develop more efficient photovoltaic devices, for example by replacing the conducting oxide layer used in traditional solar cells by a metallic contact that exhibits enhanced optical transmission.
Here, we present a systematic exploration of the design space of thin silver films perforated with arrays of sub-wavelength holes. These structures are fabricated using high-resolution electron-beam lithography and characterized optically using a high-brightness Fourier-transform spectrometer. Experimental results are compared to finite-difference time-domain simulations in order to understand the various surface plasmon modes supported by these structures.