Nanoscience and Nanotechnology Commons^™

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mathematics Faculty Publications

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

Formation Of Organized Nanostructures From Unstable Bilayers Of Thin Metallic Liquids, Mikhail Khenner, Sagar Yadavali, Ramki Kalyanaraman

Mikhail Khenner

Dewetting of pulsed-laser irradiated, thin (< 20 nm), optically reflective metallic bilayers on an optically transparent substrate with a reflective support layer is studied within the lubrication equations model. A steady-state bilayer film thickness (h) dependent temperature profile is derived based on the mean substrate temperature estimated from the elaborate thermal model of transient heating and melting/freezing. Large thermocapillary forces are observed along the plane of the liquid-liquid and liquid-gas interfaces due to this h-dependent temperature, which, in turn, is strongly influenced by the h-dependent laser light reflection and absorption. Consequently the dewetting is a result of the competition between thermocapillary and intermolecular forces. A linear analysis of the dewetting length scales established that the non-isothermal calculations better predict the experimental results as compared to the isothermal case within the bounding Hamaker coefficients. Subsequently, a computational non-linear dynamics study of the dewetting pathway was performed for Ag/Co and Co/Ag bilayer systems to predict the morphology evolution. We found that the systems evolve towards formation of different morphologies, including core-shell, embedded, or stacked nanostructure morphologies.

Effect Of Extracellular Matrix (Ecm) Protein Micropatterns On The Behavior Of Human Neuroblastoma Cells, Ishwari Poudel

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

Recent advances in patterning techniques and emerging surface microtechnologies have allowed cell micropatterning to control spatial location of the cells on a surface as well as cell shape, attachment area, and number of contacting neighbor cells. These parameters play important roles in cell cellular behaviors. Cell micropatterning has thus become one of the most important strategies for biomedical applications, such as, tissue engineering, diagnostic immunoassays, lab-on-chip devices, bio-sensing, etc., and cell biology studies as well. For neuronal cells, there have been attempts to distribute neuronal cells on specific patterns to control cell-to-cell interaction. However, there have been very limited understanding …

Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead

Graduate Theses and Dissertations

Nano-engineered-textures on a material surface can dramatically improve the wetting and non-wetting properties of a surface, and they also show promise to address friction issues that affect surfaces in contact. In this work, aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) was used to produce nano-textures on copper (Cu) substrates. A study was performed to examine the effects of changing the annealing conditions and a-Si thickness on nano-texture formation. The creation of various nano-topographies and chemically modifying them using octafluorocyclobutane (C4F8) was performed to control hydrophilicity, hydrophobicity, and oil affinity of nano-textured surfaces. A video-based contact angle measurement system was used …

Preparation And Application Of Nano-Nio As Anode In Lithium-Ion Batteries, Cheng-Dong Bai, Jia-Jia Chen, Qi Zhang, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

In this work, the nano-NiO material was prepared by hydrothermal method. The surface morphologies and electrochemical properties of nano-NiO material were investigated. The special nano-NiO material with porous surface assembling honeycombs(100-200nm) was obtained by using surface active agents. The discharge capacity of nano-NiO electrode up to 2385.7 mAh/g was achieved at current density of 0.1A/g in the first circle,while 1100mAh/g could be maintained after 100 circles. At current density of 2.0A/g, the discharge capacity of 600 mAh/g was obtained. And when the current density was reduced to 0.1A/g, the discharge capacity was restored to 1050 mAh/g. The nano-NiO electrode exhibited …

Electrocatalytic Determination Of 15 Kinds Of Phenolic Compounds By Novel Gold Nanoparticles-Modified Glassy Carbon Electrode, Yan-Ping Cui, Wei-Xing Wang, Chang-Zhu Yang, Wen-Hong Pu

Journal of Electrochemistry

A gold nanoparticles modified glassy carbon electrode (Au/GCE) was used to detect 15 kinds of phenolic compounds. In the cyclic voltammetry measurements, the peak currents of phenolic compounds at Au/GCE were all increased as compared with GCE and planar gold electrodes, and the oxidation potentials were determined by the activity of analytes. Besides, electrocatalysis of salicylic acid was studied at Au/GCE. The results showed that, there was a good linear relationship between the oxidation current and the concentration of salicylic acid, and the current sensitivity was 1.8 fold higher than that obtained on GCE. Trace phenolic compounds determination could be …

Introducing Porous Silicon As A Sacrificial Material To Obtain Cavities In Substrate Of Soi Wafers And A Getter Material For Mems Devices, Wajihuddin Mohammad

Doctoral Dissertations

Microelectromechanical system (MEMS) resonators have been a subject of research for more than four decades. The reason is the huge potential they possess for frequency applications. The use of a MEMS resonator as the timing element has an experimental history and huge progress has been made in this direction. Vacuum encapsulated MEMS resonators are required for high precision frequency control. Hence, a device with a high quality factor and durability is needed. In this effort, a new process for producing a cavity in the substrate of Silicon on insulator (SOI) MEMS devices and augmenting it with a getter using porous …

Electronic And Magnetic Excitations In Graphene And Magnetic Nano-Ribbons, Maher Zakaria Ahmed Selim

Electronic Thesis and Dissertation Repository

The discovery of graphene - a 2D material with superior physical properties - in 2004 was important for the intensive global research to find alternatives to three-dimensional (3D) semiconductor materials in industry. At the same time there have been exciting advances for 2D magnetic materials on the nanometer scale. The superior properties of graphene are mainly attributed to its crystal structure and its relatively short-range interactions. These properties show that natural and artificial 2D materials are promising for new applications.

In this thesis we have carried out a comprehensive investigation of the effects of the 2D lattice structures, the roles …

Surface Diffusion Of Adsorptive Species On Gold Nanoelectrodes, Bao-Fa Su, Wei Wang, Dong-Ping Zhan, Bin Ren, Zhong-Qun Tian

Journal of Electrochemistry

Gold nanoelectrodes were prepared successfully by a programmed laser puller. The Faraday adsorptions of oxygen and iodine, and the underpotential deposition of lead on the gold nanoelectrodes were investigated. The results showed that the active areas of nanoelectrodes were dramatically higher than their appearant geometry areas, which is caused by the surface diffusion of adsorptive species from the nanoscale gold/electrolyte interface to the adjacent gold surface.

Study On The Fluorescent Carbon Nanodots With Electrochemical Methods, Bao-Ping Qi, Yan-Min Long, Lei Bao, Cui Liu, Zhi-Ling Zhang, Dai-Wen Pang

Journal of Electrochemistry

Carbon nanodots are a new class of fluorescent nanoparticles with a carbon-based core, which possess wavelength-tunable luminescence, high photostability, resistance to photobleaching, water-solubility, and ease of bioconjugation. Owing to their attractive merits, carbon nanodots like other carbon nanomaterials such as fullerene, carbon nanotubes and graphene, have attracted much attention. In addition, carbon nanodots can be inexpensively produced by electrochemical methods with simple post-processing under mild conditions. Electrochemical approaches have unique advantages in the analysis of surface structures and luminescence mechanism of materials. In this review, recent advances in electrochemical methods used for the synthesis and luminescence mechanism of fluorescent carbon …

Study On The Electrochemical Behaviors Of Gc Electrode Modified With Carbon Nanotube-Polyelectrolytes And Its Application For Rutin Detection, Liang Hua, Xia-Qin Wu, Rong Wang

Journal of Electrochemistry

The electrochemical behaviors of rutin and ascorbic acid at single-wall carbon nanotube and polyelectrolytes (dimethyl-diallylammonium chloride, PDDA) film modified glassy carbon electrode was investigated. The cyclic voltammetric results showed that electron transfer of rutin at PDDA/SWCNTs/GC modified electrode is an adsorption-controlled process. The separation of oxidation peak potentials of rutin and ascorbic acid was more than 200 mV. The rutin concentration in the presence of AA were detected by differential pulse voltammetry (DPV). The experimental results indicated that the PDDA/SWCNTs/GC modified electrode can be used for the detection of rutin in the presence of high concentration of AA. The DPV …

On Developing Novel Energy-Relates Nanostructured Materials By Atomic Layer Deposition, Xiangbo Meng

Electronic Thesis and Dissertation Repository

ABSTRACT

This thesis presents the fabrication of a series of novel nanostructured materials using atomic layer deposition (ALD). In contrast to traditional methods including chemical vapor deposition (CVD), physical vapor deposition (PVD), and solution-based processes, ALD benefits the synthesis processes of nanostructures with many unrivalled advantages such as atomic-scale control, low temperature, excellent uniformity and conformality. Depending on the employed precursors, substrates, and temperatures, the ALD processes exhibited different characteristics. In particular, ALD has capabilities in fine-tuning compositions and structural phases. In return, the synthesis and the resultant nanostructured materials show many novelties.

This thesis covers ALD processes of four …

Domain Size And Structure In Exchange Coupled [Co/Pt]/Nio/[Co/Pt] Multilayers, Andrew G. Baruth, Shireen Adenwalla

Shireen Adenwalla Papers

We investigate the competing effects of interlayer exchange coupling and magnetostatic coupling in the magnetic heterostructure ([Co/Pt]/NiO/[Co/Pt]) with perpendicular magnetic anisotropy (PMA). This particular heterostructure is unique among coupled materials with PMA in directly exhibiting both ferromagnetic and antiferromagnetic coupling, oscillating between the two as a function of spacer layer thickness. By systematically tuning the coupling interactions via a wedge-shaped NiO spacer layer, we explore the energetics that dictate magnetic domain formation using high resolution magnetic force microscopy coupled with the magneto-optical Kerr effect. This technique probes the microscopic and macroscopic magnetic behavior as a continuous function of thickness and …

Synthesis And Characterization Of Cdse-Zns Core-Shell Quantum Dots For Increased Quantum Yield, Joshua James Angell

Master's Theses

Quantum dots are semiconductor nanocrystals that have tunable emission through changes in their size. Producing bright, efficient quantum dots with stable fluorescence is important for using them in applications in lighting, photovoltaics, and biological imaging. This study aimed to optimize the process for coating CdSe quantum dots (which are colloidally suspended in octadecene) with a ZnS shell through the pyrolysis of organometallic precursors to increase their fluorescence and stability. This process was optimized by determining the ZnS shell thickness between 0.53 and 5.47 monolayers and the Zn:S ratio in the precursor solution between 0.23:1 and 1.6:1 that maximized the relative …

Ultrafast Electron Diffraction Study Of The Dynamics Of Antimony Thin Films And Nanoparticles, Mahmoud Abdel-Fattah

Electrical & Computer Engineering Theses & Dissertations

The ultrafast fast phenomena that take place following the application of a 120 fs laser pulse on 20 nm antimony thin films and 40 nm nanoparticles were studied using time-resolved electron diffraction. Samples are prepared by thermal evaporation, at small thickness (< 10 nm) antimony nanoparticles form while at larger thicknesses we get continuous thin films.

The samples are annealed and studied by static heating to determine their Debye temperatures, which were considerably less than the standard value. The thermal expansion under static heating also yielded the expansion coefficient of the sample material. Nanoparticle samples gave a very accurate thermal expansion coefficient (11 × 10^-6 K^-1).

Ultrafast time resolved electron diffraction …

Purely Electronic Switching With High Uniformity, Resistance Tunability, And Good Retention In Pt-Dispersed Sio2 Thin Films For Reram, Albert Chen

Albert B Chen

Resistance switching memory operating by a purely electronic switching mechanism, which was first realized in Pt-dispersed SiO2 thin films, satisfies criteria including high uniformity, fast switching speed, and long retention for non-volatile memory application. This resistive element obeys Ohm's law for the area dependence, but its resistance exponentially increases with the film thickness, which provides new freedom to tailor the device characteristics.

The Design And Manufacture Of A Microfluidic Reactor For Synthesis Of Cadmium Selenide Quantum Dots Using Silicon And Glass Substrates, Peter Gonsalves

Materials Engineering

A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of silicon and Pyrex glass. Microfabrication techniques were used to etch the channels into the silicon wafer. Holes were wet-drilled into Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was aligned to the etched silicon wafer and both were anodically bonded to complete the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350^oC under 5.46N of force. Bulk CdSe solution was mixed at room temperature and treated as a single injection. The syringe containing …

The Flip-Flop Behavior Of Acetonitrile At Au Electrode Surface Investigated By Sum Frequency Generation Vibrational Spectroscopy, Zhi Huang, Xin Tang, Gang-Hua Deng, En-Cai Zhou, Hong-Fei Wang, Yuan Guo

Journal of Electrochemistry

The electrochemical interface between liquid acetonitrile and polycrystal gold electrode is investigated by in situ infrared visible sum frequency generation spectroscopy (SFG-VS). The structure of acetonitrile adsorbed at polycrystal gold electrode surface is studied as a function of electrode potential. The SFG spectra of CH3 group indicate acetonitrile orients in response to the electrode potential. The SFG signal of CH3 group turns lower as the electrode potential changes from -700mV to 300mV, and vanishes around the 300mV(pzc), then becomes a negative signal above 500mV, which indicates that the orientation is predominately with the CH3 group toward the metal between -700 …

Influence Of Tert-Butylpyridine On The Band Energetics Of Nanostructured Tio2 Electrodes And The Photoelectrochemical Properties Of Dye-Seneitized Electrodes, Shu-Ming Yang, Ji-Chao Wang, Hui-Zhi Kou, Hong-Bin Xue, Hong-Jun Wang, Yu-Ling Guo

Journal of Electrochemistry

The flat band edges (Efb) of nanostructured TiO2 electrodes in electrolyte solutions with tert-butylpyridine (TBP) of different concentrations have been determined with spectroelectrochemical technique. TBP played a role in band energetics of nanostructured TiO2 electrodes. The Efb values of -2.25, -2.46 and -2.62 V were determined in three 0.2 mol•L-1 tetrabutylammonium perchlorate (TBAP) acetonitrile electrolytes which contain 0, 0.2 and 0.4 mol•L-1 TBP respectively. The addition of Li+ ions shifted Efb positively. The Efb values of -1.12, -1.22 and -1.30 V were determined in three 0.2 mol•L-1 LiClO4 acetonitrile electrolytes which contain 0, 0.2 and 0.4 mol•L-1 TBP respectively. The …

Synthesis And Catalytic Property Of Flaked Spindle-Like Cuo Nanocrystals, Jian-Feng Fan, Li-Qing Li, Yu-Feng Huang, Lou-Zhen Fan

Journal of Electrochemistry

A simple and efficient electrochemical route was developed for the synthesis of flaked spindle-like CuO nanocrystals using aqueous electrolyte and Cu sacrificial anode (graphite as the cathode) in an undivided cell at a constant potential mode under room temperature. The morphologies, structure and component of CuO nanocrystals obtained were characterized by SEM, XRD, respectively. Flaked spindle-like CuO nanocrystals were successfully used to modify a GC electrode to detect H2O2 with cyclic voltammetry (CV) and amperometric (AC).The results showed that products were pure monoclinic CuO nanocrystals. The linear range for the determination of hydrogen peroxide is from 1.0 μmol?L-1 to 1.0 …

Dft Study Of Co2 Reduction To Hydrocarbons On Cu Surfaces, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

CO2 reduction on Cu(111) single crystal surfaces was studied using DFT calculations on the reaction energies and the minimum energy paths. The results indicated that the possible reaction paths for CO2 reduction on Cu(111) surface are CO2(g) + H* → COOH* → (CO +OH)*, (CO + H)* → CHO*, CHO + H → CH2O* → (CH2 + O)*, CH2* + 2H* → CH4 or 2CH2* → C2H4. On Cu(111) surface, the reaction rate is controlled by steps of CH2O* → (CH2 + O)*, CO2(g) + H* → COOH → (CO +OH)* and (CO + H)* → CHO*. In addition, the …

Atomistic Modeling Of Hydrogen Storage In Nanostructured Carbons, Lujian Peng

Doctoral Dissertations

Nanoporous carbons are among the widely studied and promising materials on hydrogen storage for on-board vehicles. However, the nature of nanoporous carbon structures, as well as the relationship between local structure and hydrogen adsorption are still unclear, and hinder the design of carbon materials for optimum hydrogen storage. This dissertation presents a systematic modeling effort of hydrogen storage in nanoporous carbon materials. Tight binding molecular dynamics simulations are utilized to simulate the amorphous carbons over a wide range of density. The resulting structures are in good agreement with experimental data of ultra-microporous carbon (UMC), a wood-based activated carbon, as indicated …

Effect Of Thermal Stabilizers Composed Of Zinc Barbiturate And Calcium Stearate For Rigid Poly(Vinyl Chloride).Pdf, Shumin Li

Shumin Li

Electrocatalytic Oxidation Of Hydrazine At Rutin Carbon Nanotubes Modified Electrode, Hong-Fang Zhang, Qing-Lin Sheng, Jian-Bin Zheng

Journal of Electrochemistry

The electrochemical behavior and electrocatalytic oxidation of hydrazine on rutin multiwall carbon nanotubes modified glassy carbon electrode were studied by cyclic voltammetry.The experimental results indicated that the electrode exhibits good electrocatalytic activity to hydrazine at a reduced oxidation potential of 262 mV.The amperometric response of the modified electrode showed linear increase after successive addition of hydrazine in the concentration range of 2.5×10-6~1.0×10-4 mol·L-1 with a detection limit of 5×10-7 mol·L-1.

Applications Of Raman Spectroscopy Technique In Lithium Ion Batteries, Liang Zhao, Yong-Sheng Hu, Hong Li, Zhao-Xiang Wang, Hong-Xing Xu, Xue-Jie Huang, Li-Quan Chen

Journal of Electrochemistry

The Raman spectroscopy has been widely used in the study of lithium ion batteries.In this short review,we gave some examples of the applications of Raman spectroscopy in the study of electrode materials including carbonaceous materials,spinel LiMxMn2-x O4,LiFePO4,as well as polymer electrolytes,room temperaturemolten salt electrolytes and the solid-electrolyte interphase layers.The advantages and disadvantages of the ex-situ and in-situ Raman spectrum techniques are discussed.Using new Raman techniques to investigate Li-ion batteries are suggested.

A Titanium-Supported Nanoporous Pd Electrocatalyst For Methanol Oxidation, Feng-Juan Niu, Qing-Feng Yi

Journal of Electrochemistry

Titanium-supported nanoporous palladium electrode(nanoPd /Ti) was prepared by a hydrothermal process in the presence of the ligand EDTA and using formaldehyde as reducing agent.SEM images showed that the size of Pd particles was about 60 nm and the Pd particles were connected with each other to form a three-dimensional network structure.Cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) were applied to evaluate the electrocatalytic activity of the nanoPd/Ti electrode towards methanol oxidation in alkaline solution.CV results showed that the nanoPd /Ti electrode presented high anodic peak densities and a low onset potential for methanol oxidation.Also nanoPd /Ti electrode showed excellent CO tolerance …

Synthesis Of One-Dimensional And Two-Dimensional Carbon Based Nanomaterials, Mihnea Ioan Ionescu

Electronic Thesis and Dissertation Repository

Particular physical and chemical properties of carbon based nanomaterials (CBNs) have promised and exhibited great applications in manufacturing various nanodevices such as electron field emitters, sensors, one-dimensional conductors, supercapacitors, reinforcing fibres, hydrogen storage devices, and catalyst support for fuel cells electrodes. Despite these amazing technical progresses, many challenges still remain in the development of synthesis methods suitable for commercial applications and fabricating novel functional nanostructures with complex architecture.

In this Ph.D. thesis, one-dimensional (1D), two-dimensional (2D) carbon nanostructures, and 1D/2D hybrid of carbon nanostructures have been synthesized using various chemical vapour deposition (CVD) methods. The objective of this work is …

Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu T. Tekalign, Margo S. Levine

Mathematics Faculty Publications

The linear dispersion relation for longwave surface perturbations, as derived by Levine et al. Phys. Rev. B 75, 205312 (2007) is extended to include a smooth surface energy anisotropy function with a variable anisotropy strength (from weak to strong, such that sharp corners and slightly curved facets occur on the corresponding Wulff shape). Through detailed parametric studies it is shown that a combination of a wetting interaction and strong anisotropy, and even a wetting interaction alone results in complicated linear stability characteristics of strained and unstrained films.

Stability Of A Strongly Anisotropic Thin Epitaxial Film In A Wetting Interaction With Elastic Substrate, Mikhail Khenner, Wondimu Tekalign, Margo Levine

Mathematics Faculty Publications

The linear dispersion relation for longwave surface perturbations, as derived by Levine et al. Phys. Rev. B 75, 205312 (2007) is extended to include a smooth surface energy anisotropy function with a variable anisotropy strength (from weak to strong, such that sharp corners and slightly curved facets occur on the corresponding Wulff shape). Through detailed parametric studies it is shown that a combination of a wetting interaction and strong anisotropy, and even a wetting interaction alone results in complicated linear stability characteristics of strained and unstrained films.

Modeling Diverse Physics Of Nanoparticle Self-Assembly In Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

Presents physics behind dewetting of thin liquid films and mathematical/computational modeling tools (Educational/Research presentation for senior physics majors).