Nanoscience and Nanotechnology Commons^™

Comparative Study Of Nanoporous Pt, Ptru And Ptruir Catalysts Using Electrochemical Ftir Spectroscopy, M. Amussen Robert, Holt-Hindle Peter, Nigro Samantha, Aicheng Chen

Journal of Electrochemistry

In recent years much effort has been put towards developing efficient Pt-based electrocatalysts for applications in fuel cells. With the rising cost of precious metals such as Pt,the need to enhance the activity and to decrease the load of catalysts is prominent. Herein we report on the synthesis and comparative study of nanoporous Pt,PtRu and PtRuIr electrocatalysts. The nanoporous electrodes were fabricated using a hydrothermal method and characterized by scanning electron microscopy (SEM) ,energy dispersive spectroscopy (EDS) ,X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) . The electrocatalytic activity of the fabricated nanopo- rous materials was evaluated using both CO …

Electrochemical Surface-Enhanced Raman Spectroscopy—Current Status And Perspective, Bin Ren, Jian-Feng Li, Yi-Fan Huang, Zhi-Cong Zeng, Zhong-Qun Tian

Journal of Electrochemistry

Electrochemical interface is a very important interface closely related to various energy and life processes. Surface-enhanced Raman scattering was widely used in electrochemistry soon after its discovery to understand the surface bonding,configuration,and orientation of the surface species. In recent 10 years,the fast development of nanoscience and nanotechnology has offered SERS with abundant substrates and characterization methods,which has allowed impressive development of electrochemical SERS. This articles will follow the time line to make systematically overview of SERS on Au and Ag,thin-layer transition-metal SERS,pure transition metal SERS,core-shell SERS and those methods for studying single crystal surfaces,including gap-mode SERS, TERS and SHINERS. Emphasis …

Electrochemical Sers Studies On The Adsorption Of Benzoimidazole And Derivative In Nonaqueous Solution, Ya-Xian Yuan, Feng-Zhu Yang, Wei Liu, Ping-Jie Wei, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

The surface adsorption of benzoimidazole (BIMH) and 2-mercaptobenzimidazole(MBI) was investigated by electrochemical in-situ surface enhanced Raman spectroscopy (SERS) and direct electrochemical synthesis on Cu electrode. The influence of the neutral ligand of triphenylphosphine (pph₃) on the adsorption and surface coordination of BIMH and MBI were investigated respectively. BIMH interacted with metal surface by the neutral molecule to form chemical adlayer in the extremely negative potential,while it adsorbed onto metal surface through the N atoms to form a polymer film which may suppress the corrosion of the metal. The introduction of pph₃ destroyed the film formation of BIMH …

The Sers Effect Of AuCore@PtShelL Nanoparticles With Different Pt Shell Thicknesses, Yan Zhong, Liang-Liang Yan, Gui-Shi Rao, Xiao-Cong Deng, Fei-Peng Wen, Jin-Long Xu, Qi-Ling Zhong

Journal of Electrochemistry

By using Au nanoparticles with a diameter of 55 nm as the core and ascorbic acid as the reductant, Au_core@ Pt_shell nanoparticles of controllable Pt shell thickness (0.3 ～ 6 nm) were synthesized by controlling the concentration of [PtCl₆]^2- ions. The ultraviolet-visible absorption spectrometry,scanning electron microscope (SEM), transmission electron microscope (TEM) ,high resolution transmission electron microscope (HRTEM) , and electrochemical cyclic voltammetry were employed to determine surface morphology and structure of  Au_core@Pt_shell. With SCN^- ion as a probe,the effect of the thickness of the Pt shell on the SERS …

In Situ Surface-Enhanced Raman Scattering Spectroscopic Study Of Sulfur Adsorption On Polycrystalline Platinum Electrode Surface, Bolian Xu, In-Su Park, Ying Li, De-Jun Chen, Yuye J. Tong

Journal of Electrochemistry

The paper reports the first in situ surface enhanced Raman scattering (SERS) spectroelectrochemistry study of sulfur adsorption and electro-oxidation on highly roughened polycrystalline Pt surface in both acidic and basic supporting electrolytes. The SERS spectra were taken at a constant electrode potential after accumulative electro-oxidation CVs of the Pt electrode with pre-adsorbed sulfur species and at different electrode potentials that were varied stepwise of the Pt electrode immersed in sulfur-containing electrolytes without pre-adsorbed sulfur species. In both cases,a dominant vibrational band at 299 cm^-1 in acidic electrolyte but at 310 cm^-1 in basic electrolyte was observed,which was assigned …

Preliminary Investigation Of Iron Protoporphyrin Sams On Platinum Electrodes By Surface Enhanced Vibrational Spectroscopies, Min Ma, Yao-Yue Yang, Han-Xuan Zhang, Wen-Bin Cai

Journal of Electrochemistry

In situ SERS and ATR-SEIRAS were applied to investigate the electrochemical and structural properties of iron protoporphyrin IX (FePP) self-assembled monolayers (SAMs) on Pt electrodes in 0. 1 mol· L -1 HClO₄. The potential dependent SERS spectra of the FePP SAM on a roughened Pt electrode with the enhancement factor of ca. 40 were acquired with the excitation line of 514 nm. Analyses of SERS data over the potential region from 0. 5 to -0. 3 V enabled to obtain potential dependent adsorption isotherms,from which the formal redox potential could be estimated to be ca. -0. 2 V. …

Density Functional Theory Studies Of Surface-Enhanced Raman Spectroscopy In Electrochemical Interfaces, Liu-Bin Zhao, De-Yin Wu, Bin Ren, Zhong-Qun Tian

Journal of Electrochemistry

Quantum chemical density functional theory and Raman scattering theory were used to study the bonding mechanism and surface-enhanced Raman spectroscopy of pyridine adsorbed on transition metals (Ⅷ group) and coinage metals (IB group) . SERS studies of pyridine-metal systems have been reviewed. Chemical bonding mechanism as well as photo-driven charge transfer mechanism was considered to investigate the vibrational frequency shift and the enhancement of SERS intensity in electrochemical interfaces. Our theoretical results can be used to interpret the SERS phenomena dependent on metals,excitation wavelengths,and applied potentials.

Studies Of Oxidation Processes Of Adsorbed And Solution Co On Pt(110) Electrode By Cyclic Voltammetry And In Situ Ftirs, Li Tian, Jun-Tao Li, Jin-Yu Ye, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca. 168 mV,and the peak current density has been increased by 6. 70 times. Linear adsorbed CO (COL) is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface. In a CO-free solution,the onset potential of COL is measured by in-situ FTIRS ca. 0. …

Comprehensive Reduced-Order Models Of Electrostatically Actuated Mems Switches And Their Dynamics Including Impact And Bounce, Michael G. Snow, Anil K. Bajaj

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

As MEMS technology develops it is becoming better understood that MEMS designers must account for the large uncertainties characteristic of the relevant manufacturing processes. Uncertainty quantification tasks the designer with evaluating many different possible outcomes from the manufacturing process which creates a demand for models that are accurate and comprehensive, yet fast to evaluate. This work presents a comprehensive reduced-order model of electrostatically actuated switches incorporating a range of effects that are typically included only in FE modeling codes. Specifically, the model accounts for variable electrode geometry, stretching of centerline or large displacement effects, fringing field, squeeze film and rarefied …

Simulation Of Sub-Micron Thermal Transport In A Mosfet Using A, James Loy, Druv Singh, Jayathi Y. Murthy

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

Self-heating has emerged as a critical bottleneck to scaling in modern transistors. In simulating heat conduction in these devices, it is important to account for the granularity of phonon transport since electron-phonon scattering occurs preferentially to select phonon groups. However, a complete accounting for phonon dispersion, polarization and scattering is very expensive if the Boltzmann transport equation (BTE) is used. Moreover, difficulties with convergence are encountered when the phonon Knudsen number becomes small. In this paper we simulate a two-dimensional bulk MOSFET hotspot problem using a partially-implicit hybrid BTE-Fourier solver which is significantly less expensive than a full BTE solution, …

Eight-Channel Reconfigurable Microring Filters With Tunable Frequency, Extinction Ratio And Bandwidth, Hao Shen, Maroof H. Khan, Li Fan, Lin Zhao, Yi Xuan, Jing Ouyang, Leo T. Varghese, Minghao Qi

Birck and NCN Publications

We demonstrate an eight-channel reconfigurable optical filter on a silicon chip. It consists of cascaded microring resonators and integrated compact heaters. With an embedded Mach-Zehnder (MZ) arm coupling to a microring resonator, the important parameters of a filter such as center frequency, extinction ratio and bandwidth can be controlled simultaneously for purposes of filtering, routing and spectral shaping. Thus our device could potentially be useful in dense wavelength division multiplexing (DWDM) and radio frequency arbitrary waveform generation (RFAWG). Multichannel filter response was successfully tuned to match the International Telecommunication Unit (ITU) grid with 50, 100 and 200GHz in channel spacing. …

Acoustic Phonon Scattering In Bi2te3/Sb2te3 Superlattices, Yaguo Wang, Carl Liebig, Xianfan Xu, Rama Venkatasubramanian

Birck and NCN Publications

Ultrafast time-resolved measurements were conducted to investigate long-wavelength acoustic phonon scattering and velocity reduction in Bi2Te3/Sb2Te3 superlattices. We show that both these phenomena suppress heat transfer process, with the phonon scattering contributing more in differentiating the lattice thermal conductivities among films with different periods. Measurements of reduction in the acoustic phonon amplitudes support the decrease in the thermal conductivity for certain superlattice periods, which is not predicted by acoustic mismatch theory. This study is a direct measurement of coherent acoustic phonons in superlattices which is of significant interest to thermoelectrics.

Iii-Nitride Nanopyramid Light Emitting Diodes Grown By Organometallic Vapor Phase Epitaxy, Isaac Wildeson, Robert Colby, David Ewoldt, Zhiwen Liang, Dmitri Zakharov, Nestor J. Zaluzec, R. Edwin García, E A. Stach, Timothy D. Sands

Birck and NCN Publications

Nanopyramid light emitting diodes (LEDs) have been synthesized by selective area organometallic vapor phase epitaxy. Self-organized porous anodic alumina is used to pattern the dielectric growth e templates via reactive ion etching, eliminating the need for lithographic processes. (In,Ga)N quantum well growth occurs primarily on the six {1 (1) over bar 01} semipolar facets of each of the nanopyramids, while coherent (In,Ga)N quantum dots with heights of up to similar to 20 nm are incorporated at the apex by controlling growth conditions. Transmission electron microscopy (TEM) indicates that the (In,Ga)N active regions of the nanopyramid heterostructures are completely dislocation-free. Temperature-dependent …

Metric Signature Transitions In Optical Metamaterials, Igor Smolyaninov, Evgenii Narimanov

Birck and NCN Publications

We demonstrate that the extraordinary waves in indefinite metamaterials experience an (- - + +) effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories.

Time Dependence Of Self-Assembly Process For The Formation Of Inorganic–Organic Hybrid Nanolayers, Alexandre Dhôtel

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

There is increasing interest in self-assembled materials for energy storage, flexible electronics and hydrophobic barriers. Inorganic/organic hybrid thin films and especially organosilane-based coatings already have demonstrated their ability to achieve those goals. However, some fundamental points of their formation process by molecular self-assembly remain unexplained. Although the literature widely reports the effect of temperature on the final nanostructure, until now, no one has taken into account the importance of time during their synthesis.

The main objective of this study was to improve and complete the understanding of mechanisms responsible for the self-organization of organic/inorganic molecules into a highly ordered, layered …

Microcantilever Dynamics In Liquid Environment Dynamic Atomic Force Microscopy When Using Higher-Order Cantilever Eigenmodes, Daniel Kiracofe, Arvind Raman

Birck and NCN Publications

Dynamic atomic force microscopy is currently evolving from a single to a multifrequency instrument for nanoscale imaging often employing higher-order microcantilever eigenmodes for improved resolution and force spectroscopy. In this work the authors study the fundamentals of cantilever dynamics and energy dissipation when soft cantilevers are driven at their second flexural eigenmode and interact with samples in liquid environments. Contrary to the conventional first eigenmode operation, second eigenmode operation in liquids is often dominated by a subharmonic response (e.g., one tap every four drive cycles) and there is an energy transfer to the first eigenmode creating a new channel of …

Fabrication, Characterization And Simulation Of Non-Lithographic Nanostructures And Their Potential Applications, Neelanjan Bhattacharya

UNLV Theses, Dissertations, Professional Papers, and Capstones

The dissertation describes the formation of porous silicon through the pores of porous alumina on a silicon substrate. Porous silicon, by itself, is inherently a non-uniform material that has non-uniform optical and electronic properties. In addition, it is also mechanically fragile material requiring careful material handling. The porous silicon fabricated through the nanosized pores of porous alumina are expected to mitigate these problems, thereby enhancing commercial viability of the device. The porous silicon as well the porous alumina have been synthesized through anodisation for various parameters and also various types of anodizing electrolytes. The porous silicon, so obtained have been …

Macrophages Loaded With Gold Nanoshells For Photothermal Ablation Of Glioma: An In Vitro Model, Amani Riad Makkouk

UNLV Theses, Dissertations, Professional Papers, and Capstones

The current median survival of patients with glioblastoma multiforme (GBM), the most common type of glioma, remains at 14.6 months despite multimodal treatments (surgery, radiotherapy and chemotherapy). This research aims to study the feasibility of photothermal ablation of glioma using gold nanoshells that are heated upon laser irradiation at their resonance wavelength. The novelty of our approach lies in improving nanoshell tumor delivery by loading them in macrophages, which are known to be recruited to gliomas via tumor-released chemoattractive agents. Ferumoxides, superparamagnetic iron oxide (SPIO) nanoparticles, are needed as an additional macrophage load in order to visualize macrophage accumulation in …

Current Density And Continuity In Discretized Models, Timothy B. Boykin, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

Discrete approaches have long been used in numerical modelling of physical systems in both research and teaching. Discrete versions of the Schr ¨ odinger equation employing either one or several basis functions per mesh point are often used by senior undergraduates and beginning graduate students in computational physics projects. In studying discrete models, students can encounter conceptual difficulties with the representation of the current and its divergence because different finite-difference expressions, all of which reduce to the current density in the continuous limit, measure different physical quantities. Understanding these different discrete currents is essential and requires a careful analysis of …

Knudsen Force Modeling In Application To Microsystems, Jeremy S. Nabeth, Sruti Chigullapalli, Alina A. Alexeenko

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

At the microscale, even moderate temperature differences can result in significant Knudsen forces generated by the energy exchange between gas molecules and solids immersed in a gas. Creating, controlling and measuring Knudsen forces in microsystems can be an arduous task since only limited theory exists at present. This present study investigates the mechanism of Knudsen forces in detail based on numerical solution of the Boltzmann kinetic equation. The Knudsen force is shown, in general, to be a result of thermal nonequilibrium between gas and solid. The simulations are validated by comparison with experimental measurements that have been reported by Passian …