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Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin 2018 Ames Laboratory

Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin

Surya K. Mallapragada

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that ...


Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar 2018 The Ames Laboratory

Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar

Richard Alan Lesar

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. These potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into two distinct regimes ...


Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar 2018 The Ames Laboratory

Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar

Alexander H. King

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. These potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into two distinct regimes ...


Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler 2018 Iowa State University

Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler

Xiaoli Tan

A three-phase theoretical model is proposed that is suitable for describing the effective permittivity of polymer-matrix composites containing spherical nanoparticles. The model accounts for the presence of an interphase region, which surrounds each nanosphere, whose permittivity is allowed to be different from that of the matrix polymer. The nanoparticles themselves are approximated as hard (non-overlapping) spheres, whereas the interphase regions of neighboring nanoparticles are permitted to overlap. The volume fraction of the interphase region is computed by assuming that the nanoparticles are arranged on the nodes of a simple-cubic lattice. The effective permittivity of the composite is subsequently computed via ...


Preparation And Characterization Of Whey Protein Isolate Films Reinforced With Porous Silica Coated Titania Nanoparticles, Dattatreya M. Kadam, Mahendra Thunga, Sheng Wang, Michael R. Kessler, David A. Grewell, Buddhi P. Lamsal, Chenxu Yu 2018 Central Institute of Post-Harvest Engineering and Technology

Preparation And Characterization Of Whey Protein Isolate Films Reinforced With Porous Silica Coated Titania Nanoparticles, Dattatreya M. Kadam, Mahendra Thunga, Sheng Wang, Michael R. Kessler, David A. Grewell, Buddhi P. Lamsal, Chenxu Yu

Chenxu Yu

Whey protein isolate (WPI) films embedded with TiO2@@SiO2 (porous silica (SiO2) coated titania (TiO2)) nanoparticles for improved mechanical properties were prepared by solution casting. A WPI solution of 1.5 wt% TiO2@@SiO2 nanoparticles was subjected to sonication at amplitudes of 0, 16, 80 and 160 μm prior to casting in order to improve the film forming properties of protein and to obtain a uniform distribution of nanoparticles in the WPI films. The physical and mechanical properties of the films were determined by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile testing. Water vapor permeability (WVP) measurements revealed ...


Annealing Influence On The Magnetostructural Transition In Gd5si1.3ge2.7 Thin Films, A. L. Pires, J. H. Belo, I. T. Gomes, R. L. Hadimani, David C. Jiles, L .Fernandes, P. B. Tavares, J. P. Araújo, A. M. L. Lopes, A. M. Pereira 2018 Universidade de Lisboa

Annealing Influence On The Magnetostructural Transition In Gd5si1.3ge2.7 Thin Films, A. L. Pires, J. H. Belo, I. T. Gomes, R. L. Hadimani, David C. Jiles, L .Fernandes, P. B. Tavares, J. P. Araújo, A. M. L. Lopes, A. M. Pereira

Ravi L Hadimani

Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 773 K, the samples showed a typical paramagnetic behavior. On the other hand, annealing below 773 K promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition ...


Preparation And Characterization Of Whey Protein Isolate Films Reinforced With Porous Silica Coated Titania Nanoparticles, Dattatreya M. Kadam, Mahendra Thunga, Sheng Wang, Michael R. Kessler, David A. Grewell, Buddhi P. Lamsal, Chenxu Yu 2018 Central Institute of Post-Harvest Engineering and Technology

Preparation And Characterization Of Whey Protein Isolate Films Reinforced With Porous Silica Coated Titania Nanoparticles, Dattatreya M. Kadam, Mahendra Thunga, Sheng Wang, Michael R. Kessler, David A. Grewell, Buddhi P. Lamsal, Chenxu Yu

David A. Grewell

Whey protein isolate (WPI) films embedded with TiO2@@SiO2 (porous silica (SiO2) coated titania (TiO2)) nanoparticles for improved mechanical properties were prepared by solution casting. A WPI solution of 1.5 wt% TiO2@@SiO2 nanoparticles was subjected to sonication at amplitudes of 0, 16, 80 and 160 μm prior to casting in order to improve the film forming properties of protein and to obtain a uniform distribution of nanoparticles in the WPI films. The physical and mechanical properties of the films were determined by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile testing. Water vapor permeability (WVP) measurements revealed ...


Assembling Bare Au Nanoparticles At Positively Charged Templates, Wenjie Wang, Honghu Zhang, Ivan Kuzmenko, Surya K. Mallapragada, David Vaknin 2018 Ames Laboratory

Assembling Bare Au Nanoparticles At Positively Charged Templates, Wenjie Wang, Honghu Zhang, Ivan Kuzmenko, Surya K. Mallapragada, David Vaknin

Surya K. Mallapragada

In-situ X-ray reflectivity (XRR) and grazing incidence X-ray small-angle scattering (GISAXS) reveal that unfunctionalized (bare) gold nanoparticles (AuNP) spontaneously adsorb to a cationic lipid template formed by a Langmuir monolayer of DPTAP (1,2-dihexadecanoyl-3-trimethylammonium-propane) at vapor/aqueous interfaces. Analysis of the XRR yields the electron density profile across the charged-interfaces along the surface normal showing the AuNPs assemble with vertical thickness comparable to the particle size. The GISAXS analysis indicates that the adsorbed mono-particle layer exhibits short-range in-plane correlations. By contrast, single-stranded DNA-functionalized AuNPs, while attracted to the positively charged surface (more efficiently with the addition of salt to the ...


Protein Patterns Template Arrays Of Magnetic Nanoparticles, Srikanth Nayak, Honghu Zhang, Xunpei Liu, Shuren Feng, Pierre Palo, Marit Nilsen-Hamilton, Mufit Akinc, Surya K. Mallapragada 2018 Iowa State University and Ames Laboratory

Protein Patterns Template Arrays Of Magnetic Nanoparticles, Srikanth Nayak, Honghu Zhang, Xunpei Liu, Shuren Feng, Pierre Palo, Marit Nilsen-Hamilton, Mufit Akinc, Surya K. Mallapragada

Surya K. Mallapragada

Controlling the morphology of magnetic nanoparticles and their spatial arrangement is crucial for manipulating their functional properties. The commonly available inorganic processes for the synthesis of uniform magnetic nanoparticles typically require extreme reaction conditions such as high temperatures or harsh reagents, rendering them unsuitable for making functionalized magnetic nanoparticles with tunable properties controlled by biomolecules. Biomimetic procedures, inspired by the production of uniform magnetite and greigite crystals in magnetotactic bacteria, provide an alternative method, which can allow synthesis and spatial arrangement under ambient conditions. Mms6, an amphiphilic protein found in magnetosome membranes in Magnetospirillum magneticum strain AMB-1, can control the ...


Comparative Study Of Magnetic Properties Of Nanoparticles By High-Frequency Heat Dissipation And Conventional Magnetometry, V. Malik, J. Goodwill, Surya K. Mallapragada, Tanya Prozorov, Ruslan Prozorov 2017 Ames Laboratory

Comparative Study Of Magnetic Properties Of Nanoparticles By High-Frequency Heat Dissipation And Conventional Magnetometry, V. Malik, J. Goodwill, Surya K. Mallapragada, Tanya Prozorov, Ruslan Prozorov

Surya K. Mallapragada

The rate of heating of 15 nm uniformly-sized magnetic aqueous nanoparticles suspension by high-amplitude and high-frequency ac magnetic field induced by the resonating LC circuit was measured. The results are analyzed in terms of specific energy absorption rate (SAR). Fitting field amplitude and frequency dependences of SAR to the linear response theory, magnetic moment per particles was extracted. The value of magnetic moment was independently evaluated from dc magnetization measurements of a frozen colloid by fitting field-dependent magnetization to a Langevin function. The two methods produced similar results, which are compared to the theoretical expectation for this particle size. Additionally ...


Self-Assembly Of Dna Functionalized Gold Nanoparticles At The Liquid-Vapor Interface, Honghu Zhang, Wenjie Wang, Noah Hagen, Ivan Kuzmenko, Mufit Akinc, Alex Travesset, Surya K. Mallapragada, David Vaknin 2017 Iowa State University and Ames Laboratory

Self-Assembly Of Dna Functionalized Gold Nanoparticles At The Liquid-Vapor Interface, Honghu Zhang, Wenjie Wang, Noah Hagen, Ivan Kuzmenko, Mufit Akinc, Alex Travesset, Surya K. Mallapragada, David Vaknin

Surya K. Mallapragada

Surface sensitive synchrotron X-ray scattering and spectroscopy are used to monitor and characterize the spontaneous formation of 2D Gibbs monolayers of thiolated single-stranded DNA-functionalized gold nanoparticles (ssDNA-AuNPs) at the vapor–solution interface by manipulating salt concentrations. Grazing incidence small-angle X-ray scattering and X-ray reflectivity show that the noncomplementary ssDNA-AuNPs dispersed in aqueous solution spontaneously accumulate at the vapor–liquid interface in the form of a single layer by increasing MgCl2 or CaCl2 concentrations. Furthermore, the monoparticle layer undergoes a transformation from short- to long-range (hexagonal) order above a threshold salt-concentration. Using various salts at similar ionic strength to those of ...


Femtosecond Laser Micromachining Of Low-Temperature Co-Fired Ceramic And Glass Fiber Reinforced Polymer Printed Circuit Boards Materials, Raif Farkouh 2017 University of Nebraska - Lincoln

Femtosecond Laser Micromachining Of Low-Temperature Co-Fired Ceramic And Glass Fiber Reinforced Polymer Printed Circuit Boards Materials, Raif Farkouh

Theses, Dissertations, and Student Research from Electrical & Computer Engineering

Low-temperature co-fired ceramic (LTCC), and glass fiber reinforced polymer (GFRP) printed circuit boards (PCBs) are two materials used for the packaging of electronics. The excellent mechanical and electrical properties of LTCC, combined with the ability to embed passive components offer superior radio frequency (RF) performance and device miniaturization for high-frequency applications. Due to its unique properties, LTCC provides superior performance in applications as diverse as military radar, imaging systems, advanced automotive sensing, telecommunications, and satellites. The use of LTCC in these applications has created a demand for the micromachining of holes, channels, and cavities with specific geometries and structures. Likewise ...


Nanoneuromedicines For Degenerative, Inflammatory, And Infectious Nervous System Diseases, Howard E. Gendelman, Vellareddy Anatharam, Tatiana Bronich, Shivani Ghaisas, Huajun Jin, Anumantha G. Kanthasamy, Xinming Liu, JoEllyn McMillan, R. Lee Mosley, Balagi Narasimhan, Surya K. Mallapragada 2017 University of Nebraska Medical Center

Nanoneuromedicines For Degenerative, Inflammatory, And Infectious Nervous System Diseases, Howard E. Gendelman, Vellareddy Anatharam, Tatiana Bronich, Shivani Ghaisas, Huajun Jin, Anumantha G. Kanthasamy, Xinming Liu, Joellyn Mcmillan, R. Lee Mosley, Balagi Narasimhan, Surya K. Mallapragada

Surya K. Mallapragada

Interest in nanoneuromedicine has grown rapidly due to the immediate need for improved biomarkers and therapies for psychiatric, developmental, traumatic, inflammatory, infectious and degenerative nervous system disorders. These, in whole or in part, are a significant societal burden due to growth in numbers of affected people and in disease severity. Lost productivity of the patient and his or her caregiver, and the emotional and financial burden cannot be overstated. The need for improved health care, treatment and diagnostics is immediate. A means to such an end is nanotechnology. Indeed, recent developments of health-care enabling nanotechnologies and nanomedicines range from biomarker ...


Identifying Low-Coverage Surface Species On Supported Noble Metal Nanoparticle Catalysts By Dnp-Nmr, Robert L. Johnson, Frederic A. Perras, Takeshi Kobayashi, Thomas J. Schwartz, James A. Dumesic, Brent H. Shanks, Marek Pruski 2017 Iowa State University

Identifying Low-Coverage Surface Species On Supported Noble Metal Nanoparticle Catalysts By Dnp-Nmr, Robert L. Johnson, Frederic A. Perras, Takeshi Kobayashi, Thomas J. Schwartz, James A. Dumesic, Brent H. Shanks, Marek Pruski

Brent H Shanks

DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticle catalysts. By offering >2500-fold time savings, the technique enabled the observation of 13C–13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.


Diffusion Of Two-Dimensional Epitaxial Clusters On Metal (100) Surfaces: Facile Versus Nucleation-Mediated Behavior And Their Merging For Larger Sizes, King C. Lai, Da-Jiang Liu, James W. Evans 2017 Iowa State University and Ames Laboratory

Diffusion Of Two-Dimensional Epitaxial Clusters On Metal (100) Surfaces: Facile Versus Nucleation-Mediated Behavior And Their Merging For Larger Sizes, King C. Lai, Da-Jiang Liu, James W. Evans

Ames Laboratory Accepted Manuscripts

For diffusion of two-dimensional homoepitaxial clusters of N atoms on metal (100) surfaces mediated by edge atom hopping, macroscale continuum theory suggests that the diffusion coefficient scales like DN∼N−β with β=3/2. However, we find quite different and diverse behavior in multiple size regimes. These include: (i) facile diffusion for small sizes N<9; (ii) slow nucleation-mediated diffusion with small β<1 for “perfect” sizes N=Np=L2 or L(L+1), for L=3,4, ... having unique ground-state shapes, for moderate sizes 9≤N≤O(102); the same also applies for N=Np+3, Np+4, ...(iii) facile diffusion but with large β>2 for N=Np+1 and Np+2 also for moderate sizes 9≤N≤O(102); (iv) merging of the above distinct branches and subsequent anomalous scaling with 1≲β<3/2, reflecting the quasifacetted structure of clusters, for larger N=O(102) to N=O(103); (v) classic scaling with β=3/2 for very large N=O(103) and above. The specified size ranges apply for typical model parameters. We focus on the moderate size regime where we show that diffusivity cycles quasiperiodically from the slowest branch for Np+3 (not Np) to the fastest branch for Np+1. Behavior is quantified by kinetic Monte Carlo simulation of an appropriate stochastic lattice-gas model. However, precise analysis must account for a strong enhancement of diffusivity for short time increments due to back correlation in the cluster motion. Further understanding of this enhancement, of anomalous size scaling behavior, and of the merging of various branches, is facilitated by combinatorial analysis of the number of the ground-state and low-lying excited state cluster configurations, and also of kink populations.


Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin 2017 Ames Laboratory

Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin

Ames Laboratory Accepted Manuscripts

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that ...


Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri 2017 Iowa State University

Calcination Does Not Remove All Carbon From Colloidal Nanocrystal Assemblies, Pratyasha Mohapatra, Santosh Shaw, Deyny Mendivelso-Perez, Jonathan M. Bobbitt, Tiago F. Silva, Fabian Naab, Bin Yuan, Xinchun Tian, Emily A. Smith, Ludovico Cademartiri

Ames Laboratory Accepted Manuscripts

Removing organics from hybrid nanostructures is a crucial step in many bottom-up materials fabrication approaches. It is usually assumed that calcination is an effective solution to this problem, especially for thin films. This assumption has led to its application in thousands of papers. We here show that this general assumption is incorrect by using a relevant and highly controlled model system consisting of thin films of ligand-capped ZrO2 nanocrystals. After calcination at 800 °C for 12 h, while Raman spectroscopy fails to detect the ligands after calcination, elastic backscattering spectrometry characterization demonstrates that ~18% of the original carbon atoms are ...


Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock 2017 University of Nebraska-Lincoln

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

Theses, Dissertations, and Student Research from Electrical & Computer Engineering

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with ...


Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin 2017 University of Arkansas, Fayetteville

Structural And Elastic Properties Of Degenerate Sno Monolayers At Finite Temperature, Afsana Sharmin

Theses and Dissertations

Chalcogen-based layered superconductors with a litharge structure such as FeS and FeSe mono-layers undergo structural and superconducting phase transitions that are tunable by doping. Representing another material platform with a litharge structure but without valence d-electrons, SnO monolayers also display a structural ground state with a degenerate rectangular unit cell at zero temperature and a charge-tunable energy barrier that leads to a thermally-controllable structural phase change. Doped SnO monolayers with rectangular degenerate unit cells give rise to two-dimensional multiferroicity. Their two-dimensional elastic energy landscape adopts a basic analytic expression that is employed to discuss this structural transition. The results contained ...


Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan 2017 University of Nebraska-Lincoln

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method ...


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