Physical Chemistry Commons^™

Effect Of 18-Crown-6 Additive On Chromium Electrodeposition In Ionic Liquid, Yi-Jie Wang, Dong-Fang Niu, Xin-Sheng Zhang

Journal of Electrochemistry

Trivalent chromium ion (Cr³⁺) is used for electrodeposition due to its low toxicity. Electrodeposition in ionic liquids can greatly solve for hydrogen evolution problem. However,as a widely used Cr(III) precursor, chromium chloride hydrate (CrCl₃·6H₂O), still contains water. In the presence of water, Cr³⁺ will form a complex coordination structure with water molecules ([Cr(H₂O)₆]³⁺), which is a stable octahedral structure and is difficult to be directly reduced to chromium metal. Therefore, coordination agents should be added into the bath. In this work, the effect of 18-Crown-6 additive on …

Electrochemical Determination Of Dopamine Based On Metal-Substituted Polyoxometalates Composites, Yi-Fei Xing, Na Li, Xiao-Fang Wen, Hong-Yan Han, Min Cui, Cong Zhang, Ju-Jie Ren, Xue-Ping Ji

Journal of Electrochemistry

In this report, a dopamine electrochemical sensor based on metal-substituted polyoxometalates and reduced graphene oxide (RGO) composite was successfully constructed. The K₂H₂SiW₁₁NiO₃₉·xH₂O (SiW₁₁Ni) was synthesized by hydrothermal method, while the RGO was prepared by Hummers' method and chemical reduction method. The above-mentioned materials were characterized by SEM, FTIR and XRD. The as-synthesized SiW₁₁Ni and RGO composites were modified on the surface of glassy carbon electrode (GCE) by drop coating method, and the sensing interface (SiW₁₁Ni-RGO/GCE) was successfully constructed. The electrochemical properties of …

Pitting Behaviors Of Passivated And Trans-Passivated 304 Stainless Steel, Jing Shen, Zi-Ming Wang, Da-Jiang Zheng, Guang-Ling Song

Journal of Electrochemistry

In order to further understand the passivation and trans-passivation behaviors of 304 stainless steels, the samples were pretreated under different polarization potentials and their corrosion behaviors were investigated. It was found that the pitting potential of the untreated sample was the same as that of the sample treated with 1.1 V trans-passivation potential, while the pitting potential of the sample treated with 0.5 V passivation treatment was the highest. This observation was further verified by the SKP results. According to SEM observations, the surface of the untreated sample preserved a polishing morphology, while the surface of the 0.5 V passivation …

Applied Molecular Dynamics: From Targeting Viral Helicases, To Understanding The Interactions Of Cucurbituril Complexes In Ionic Solutions, Bryan Raubenolt

LSU New Orleans Theses and Dissertations

Molecular Dynamics simulations are a highly useful tool in helping understand the fundamental interactions present in a variety of chemical systems. The work discussed here illustrates it’s use in determining the conformational dynamics of the Zika and SARS-Cov-2 helicase in a physiological environment, largely in an effort to discover inhibitors capable of rendering the protein inert. Additionally, we show how it can be used to understand paradoxical trends in the anion-induced precipitation of Cucurbituril cavitands.

Viral helicases are motor proteins tasked with unwinding the viral dsRNA, a crucial step in preparing the strand to be translatable by host cells. By …

Understanding The Role Of Atom Trapping In The Evolution Of Hydrocarbon Transformation Catalyst Morphology, Griffin Alexander Canning

Chemistry and Chemical Biology ETDs

Converting alkanes to other, more chemically and economically valuable molecules requires catalysts that can survive elevated temperatures and highly reducing environments. These environments can cause many metal-nanoparticle based catalysts to sinter rapidly, causing a loss of activity. They must also tolerate the coke formation, as well, since coke can restrict access to active sites by gas phase molecules, thus lowering catalytic activity. While there are routes to improve both the sinter and coke resistance of catalysts, an alternative strategy is to develop a protocol for regenerating the activity of the catalyst in question when coke formation or sintering becomes problematic. …

Predicting The Hydration Free Energy Of Small Alkanes And Alcohols From Custom, Electronic Structure-Based Force Fields, T. Ryan Rogers

Graduate Theses and Dissertations

Mathematical theories reveal the fundamental physics involved in experimentalphenomena. Computer models of such theories are routinely used to corroborate or explain experiments and predict properties of chemical systems. Therefore, an important effort in computational chemistry is the development of more accurate and efficient chemical models. Current-generation models are only beginning to approach experimental-quality predictions of hydration free energies (HFEs).Using computations of quantum mechanical (QM) forces and classical simulations based on these forces, I investigate models to predict several properties of solutes and solutions. This dissertation is a collection of projects exemplifying methods used to gain insight into chemical systems.

Simulations …

Developments Of Machine Learning Potentials For Atomistic Simulations, Howard Yanxon

UNLV Theses, Dissertations, Professional Papers, and Capstones

Atomistic modeling methods such as molecular dynamics play important roles in investigating time-dependent physical and chemical processes at the microscopic level. In the simulations, energy and forces, sometimes including stress tensor, need to be recalculated iteratively as the atomic configuration evolves. Consequently, atomistic simulations crucially depend on the accuracy of the underlying potential energy surface. Modern quantum mechanical modeling based on density functional theory can consistently generate an accurate description of the potential energy surface. In most cases, molecular dynamics simulations based on density functional theory suffer from highly demanding computational costs. On the other hand, atomistic simulations based on …

Unspecified Verticality Of Franck-Condon Transitions, Absorption And Emission Spectra Of Cyanine Dyes, And A Classically Inspired Approximation, Joseph D. Alia, Joseph A. Flack

Chemistry Publications

The computed vertical energy, Ev,a/f, from the equilibrium geometry of the initial electronic state is frequently considered as representative of the experimental excitation/emission energy, Eabs/fl = hc/λmax. Application of the quantum mechanical version of the Franck–Condon principle does not involve precise specification of nuclear positions before, after, or during an electronic transition. Moreover, the duration of an electronic transition is not experimentally accessible in spectra with resolved vibrational structure. It is shown that computed vibronic spectra based on TDDFT methods and application of quantum mechanical FC analysis predict Eabs = hc/λmax …

Structure And Dynamics Of Phospholipid Vesicles And The Dependence On Nanoscale Interactions With Molecules Of Varying Complexity, Lakshapathy Widanelage Judith Upeka De Mel

LSU Doctoral Dissertations

In this dissertation, molecular interactions and changes imposed by nano-scale structures on phospholipid vesicles were investigated. 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) large unilamellar vesicles (LUVs) were used as the model system. Understanding changes of the bilayer structure, interfacial properties, lipid dynamics, and self-assembly, allows bridging relationships between biological cell membrane structure and dynamics to cellular functionalities. For example, membrane curvature changes are linked to membrane protein functions, although the exact mechanisms of control are not yet understood. Moreover, the knowledge gained from vesicle models allows exploring novel strategies for drug delivery applications. To achieve this, DOPC LUVs were synthesized and characterized by a …

Computational Investigations Of Battery Electrolytes, Ke Li

LSU Doctoral Dissertations

In this dissertation, the structure and dynamics of battery electrolytes were investigated using atomistic molecular dynamics (MD) simulations. Battery electrolytes play a key role in transporting ions between the cathode and anode. The chemical stability and ionic conductivity of electrolytes influence battery performance. In order to design better electrolytes, one needs an understanding of the relationship between electrolyte structure, dynamics, and bulk properties. To bridge the gap between the macroscopic phenomenon and the hidden molecular physics, in the first project we focused on probing an ether-based electrolyte, chosen for its relevance in sodium-based batteries. Through studying the impact of concentration …

Radial Basis Densities And The Density Functional-Based Atom-In-Molecule: Designing Charge-Transfer Potentials, Godwin Amo-Kwao

Nanoscience and Microsystems ETDs

Classical potentials that are capable of describing charge transfer and charge polarization in complex systems are of central importance for classical atomistic simulation of biomolecules and materials. Current potentials—regardless of the system—do not generalize well, and, with the exception of highly-specialized empirical potentials tuned for specific systems, cannot describe chemical bond formation and breaking. The charge-transfer embedded atom method (CT-EAM), a formal, DFT-based extension to the original EAM for metals, has been developed to address these issues by modeling charge distortion and charge transfer in interacting systems using pseudoatom building blocks instead of the electron densities of isolated atoms. CT-EAM …

New Metal Based Saturable Absorber For Ultrashort Pulse Generation, Muhammad Taufiq Ahmad

Student Works (2020-2029)

Cost-efficient, robust and flexible laser systems are vital for a wide-range of applications ranging from high-precision material processing to biomedicine. This thesis aims to explore pure silver and gold based saturable absorbers (SAs) as Q-switcher and mode-locker in various fibre laser cavities. The generations of Q-switched pulses in 1-,1.55-, and 2-micron regions have been successfully demonstrated using a pure gold, which was deposited using electron beam deposition onto a PVA thin-film as SA. For instance, a stable Q-switched thulium-doped fibre laser (TDFL) operating at 1949 nm was successfully demonstrated with the gold SA. The proposed laser generates Q switched pulses …

Adsorption And Reconfiguration Of Amphiphiles At Silica-Water Interfaces: Role Of Electrostatic Interactions, Van Der Waals Forces And Hydrogen Bonds, Yao Wu

LSU Doctoral Dissertations

The ability to explore and predict metastable structures of hybrid self-assemblies is of central importance for the next generation of advanced materials with novel properties. As compared to their thermodynamically stable forms, the kinetically stabilized materials show improved functionality potentially over their stable counterparts. The self-assembly processes usually originate from weak intermolecular interactions, involving a dynamic competition between attractive and repulsive interactions. These weak forces, including van der Waals (vdW), electrostatic interaction and the hydrogen bonding (H-bonding), can be tuned by external stimuli, e.g., confinement, temperature and ionization, and consequently driving hybrid materials into different configurations. It is challenging to …

High Level Ab Initio Study Of The Energetic And Spectroscopic Properties Of [Al,S,O]X (X=0,+1) And Its Potential For Detection In Space, Vincent J. Esposito, Tarek Trabelsi, Joseph S. Francisco

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Highly reliable molecular properties have been computed for the [Al, S, O]^x (x = 0, +1) molecular system. Spectroscopic parameters are predicted from analysis of each isomer’s 3D potential energy surface calculated using the explicitly correlated multireference configuration interaction method, including the Davidson correction (MRCI-F12+Q). These parameters provide an accurate prediction of spectroscopic data that can be used in laboratory and observational studies of these molecules. Linear-SAlO is expected to have a large permanent dipole moment suitable for detection in the circumstellar envelopes of large, evolved, oxygen-rich stars such as VY Canis Majoris, IK Tauri, and R Doradus. …

Facile Synthesis Of Nitrogen-Doped Graphene-Like Active Carbon Materials For High Performance Lithium-Sulfur Battery, Quan-Hua Meng, Wen-Wen Deng, Chang-Ming Li

Journal of Electrochemistry

Lithium-sulphur (Li-S) battery is regarded as a promising energy storage device because of its high theoretical capacity. However, the low S utilization and short cycling life limit the commercial applications. In this work, nitrogen-doped graphene-like carbon (NGC) materials were synthesized by simply pyrolyzing and carbonizing the mixture of melamine (C₃H₆N₆) and L-cysteine (C₃H₇NO₂S). The graphene-like structure in NGC effectively buffered the volume change of S during the discharge/charge process and improved the cycling stability. Meanwhile, nitrogen-containing functional groups in NGC facilitated the transportation of ions and suppressed the …

Electrochemical Engineering Of Carbon Nanodots, Lei Bao, Dai-Wen Pang

Journal of Electrochemistry

Aqueous batteries have been considered to be a competitive candidate for large-scale energy storage. However, most of aqueous batteries adopt inorganic electrode materials with metallic elements, which are based on the reversible insertion of metal ions, making their application being highly hindered by limited cycle life, environmental issue, high cost and low reserves. On the other hand, organic electrode materials offer the advantages of abundant reserves, tunable structures, renewability and environmental benignity. Furthermore, the wide internal space enables these organics to flexibly store various charge carriers. Organics have been investigated as the alternative to inorganic electrode materials. Herein, we review …

Porous-Electrode Theory Of Lithium Ion Battery: Old Paradigm And New Challenge, Xiao-Xiao Wang, Zi-Rui Zhou, Qiang Shan, Zeng-Ming Zhang, Jun Huang, Yu-Wen Liu, Sheng-Li Chen

Journal of Electrochemistry

A critical review on the porous electrode theory developed by Newman and his colleagues is presented. We propose several ideas for further development of this theory by analyzing its limitations. The classical Newman theory does not consider ion steric effect in describing ion transport in electrolyte solutions, which can be amended by a newly developed ion-vacancy coupled charge transfer model for ion transport in concentrated solutions. Ion transport in solid particles of active materials is essentially an ion-electron coupled transport process, and its rationality is verified by comparing the calculated and experimental diffusion coefficients of Li ⁺ ion in intercalation …

Progress And Prospects On Multifunctional Coating Separators For Lithium-Sulfur Battery, Zhuang-Zhuang Wei, Nan-Xiang Zhang, Feng Wu, Ren-Jie Chen

Journal of Electrochemistry

The development of advanced energy storage systems is crucial to meet the growing demand for electric vehicles, portable devices and renewable energy storage. Lithium-sulfur (Li-S) batteries, with their advantages of high specific energy, low cost of raw materials and environmental friendliness, are hotspots in the research field of new high performance batteries. However, there are still many problems which hinder the practical applications of lithium-sulfur batteries, such as the shuttle effect of soluble polysulfide intermediates, the growth of lithium dendrites, and the thermal stability and safety of lithium-sulfur batteries during use. The design of multifunctional coating separator is one of …

Licoo2 As Sulfur Host To Enhance Cathode Volumetric Capacity For Lithium-Sulfur Battery, Lu Wang, Xue-Ping Gao

Journal of Electrochemistry

Lithium-sulfur battery is one of the most promising secondary battery systems due to its super high theoretical gravimetric and volumetric energy densities (2600 Wh·kg^-1 and 2800 Wh·L^-1, respectively). However, the practical volumetric capacity of sulfur cathode is still unsatisfied due to the overuse of low-density host materials, such as carbon nanomaterials. Herein, commercial LiCoO₂ with the high tap density of 2.94 g·cm^-3 was used as the host material to build high density sulfur-based composite and compact electrode for increasing the volumetric capacity. Obviously, the tap density of the as-prepared S/LiCoO₂ composite was 1.90 g·cm …

Research Progress Of Key Components In Lithium-Sulfur Batteries, Jia-Jia Chen, Quan-Feng Dong

Journal of Electrochemistry

Due to the much higher theoretical specific capacity and energy density than the ones of traditional lithium ion battery, Li-S batteries have long been at the pinnacle in the realms of high-energy Li-metal batteries. However, the complicated electrochemical reactions on the sulfur cathode and Li anode, induced by the thermodynamic and kinetic behaviors of lithium polysulfides, are the intrinsic bottleneck to realize the full potential of Li-S batteries for practical application. In this review, we firstly discuss the roles, and thermodynamic and kinetic behaviors of polysulfides in the charging and discharging processes of Li-S batteries. Then, the functional design and …