Physical Chemistry Commons^™

Reaction Mechanism Between Small-Sized Ce Clusters And Water Molecules: An Ab Initio Investigation On CeN+H2O, Rulong Zhou, Yang Yang, Seema Pande, Bingyan Qu, Dongdong Li, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Reactions of small-sized cerium clusters Ce_n (n = 1–3) with a single water molecule are systematically investigated theoretically. The ground state structures of the Ce_n/H₂O complex and the reaction pathways between Ce_n + H₂O are predicted. Our results show the size-dependent reactivity of small-sized Ce clusters. The calculated reaction energies and reaction barriers indicate that the reactivity between Ce_n and water becomes higher with increasing cluster size. The predicted reaction pathways show that the single Ce atom and the Ce₂ and Ce₃ clusters can all easily react with H …

Au60–: The Smallest Gold Cluster With The High-Symmetry Icosahedral Core Au13, Seema Pande, Xingao Gong, Lai-Sheng Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Among coinage metal nanoclusters with 55 atoms, only Ag₅₅^– and Cu₅₅^– are the geometric magic-number clusters, as both exhibit icosahedral symmetry. Au₅₅^–, however, exhibits much lower symmetry due largely to the strong relativistic bonding effect. In this study, we collect a much larger population (>10,000 isomers) of low-energy isomers of Au₅₅^– to Au₆₀^– by using the combined density-functional theory and basin-hopping global optimization method. We also include the spin−orbit effect in the density-functional theory computation to achieve simulated photoelectron spectra in quantitative fashion. Remarkably, we uncover that the …

Roaming Transition States And Highly Accurate Thermochemistry: A Pepico Study Of Two Small Combustion Systems, Kyle John Covert

University of the Pacific Theses and Dissertations

Two small combustion systems, methyl hydroperoxide (CH₃OOH) and 2-propanol ((CH₃)₂CHOH), were studied using imaging photoelectron photoion coincidence spectroscopy (iPEPICO), which combines photoelectron spectroscopy and photoionization mass spectrometry to detect coincident photoelectron-photoion pairs. In the photon energy range of 11.4–14.0 eV, energy selected CH₃OOH⁺ ions dissociate into CH₂OOH⁺, HCO⁺, CH₃⁺, and H₃O⁺ ions. The lowest-energy dissociation channel is the formation of the cation of the smallest “QOOH” radical, CH₂OOH⁺. A statistical rate model fitted to the …

Diisopropylammonium Bromide Based Two-Dimensional Ferroelectric Monolayer Molecular Crystal With Large In-Plane Spontaneous Polarization, Liang Ma, Yinglu Jia, Stephen Ducharme, Jinlan Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In light of their easy processing, light weight and mechanical flexibility, ferroelectric molecular crystal with large spontaneous polarization (P_s) is highly desired for many advanced applications. Herein, we report the first theoretical study of two-dimensional (2D) ferroelectric molecular crystals via ab initio calculations. Specifically, we show that diisopropylammonium bromide (DIPAB) based 2D ferroelectric monolayer molecular crystal with large in-plane P_s of ∼1.5 × 10⁻⁶ μC cm⁻¹ can be achieved by slicing the bulk DIPAB along a specific plane while keeping the space group unchanged. The important roles of hydrogen bonds are …

The Pilot Application Of Electrochemical Impedance Spectroscopy On Dynamic Proton Exchange Membrane Fuel Cell, Jian-Wei Guo, Jian-Long Wang

Journal of Electrochemistry

By analyzing Electrochemical Impedance Spectroscopy (EIS) in applications of dynamic proton exchange membrane fuel cell (PEMFC), bottlenecks which restrict EIS tool development have been pointed out in this paper. Though the high-frequency resistance in EIS is largely accepted as cell inner-resistance, this can only be applied for cell with low current. The low-frequency resistance is difficult to be realized due to its relation with mass transfer. Furthermore, the improved Randles equivalent circuits are built up preliminarily, thus, penetrating into studies for mass transfer reaction, cell operation/degeneration, and high temperature fuel cell. Inspiringly, EIS is becoming an analyzing tool for stack …

The Investigation Of The Chlorine Initiated Oxidation Of 2-Phenylethanol And Stability Of Superalkali Lithium Substituted Silyls., Adam Otten

Master's Theses

This thesis investigates the combustion potential of 2-phenylethanol and the superalkali properties of small lithium substituted silicon compounds. All combustion experiments were performed at the Advanced Light Source of Lawrence Berkeley National Laboratory at the Chemical Dynamics Beamline 9.0.2. The chlorine initiated oxidation of 2PE was investigated at 298 and 550 K using a multiplex photoionization mass spectrometer, coupled with the tunable vacuum ultraviolet radiation. Reaction products were identified using kinetic time traces and photoionization spectra.

Additionally, the stability of small superalkali silicon-lithium compounds has also been investigated. All structures and energetics were calculated using the CBS-QB3 composite method.

The …

Synthesis Of Keggin Polyoxometalates Modified Carbon Paste Electrode As A Sensor For Dopamine Detection, Peng-Fei Dong, Na Li, Hai-Yan Zhao, Min Cui, Cong Zhang, Ju-Jie Ren, Xue-Ping Ji

Journal of Electrochemistry

Polyoxometalates, a class of anionic clusters with structure diversity and size variability, make them very attractive in many fields such as electrochemistry, catalysis and medicine. The Co(C₁₅N₆H₁₂)₂[PW₁₂O₃₈]·5H₂O(Co[PW₁₂O₃₈]) modified carbon paste electrode was prepared in this work, and its electrochemical performances as the sensor for dopamine detection were characterized with electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The preparation conditions and test conditions were optimized respectively. Under the optimized conditions, the POMs modified carbon paste electrode exhibited good selectivity and sensitivity …

Photocatalytic Activity: Experimental Features To Report In Heterogeneous Photocatalysis, Md. Ariful Hoque, Marcelo I. Guzman

Chemistry Faculty Publications

Heterogeneous photocatalysis is a prominent area of research with major applications in solar energy conversion, air pollution mitigation, and removal of contaminants from water. A large number of scientific papers related to the photocatalysis field and its environmental applications are published in different journals specializing in materials and nanomaterials. However, many problems exist in the conception of papers by authors unfamiliar with standard characterization methods of photocatalysts as well as with the procedures needed to determine photocatalytic activities based on the determination of “apparent quantum efficiencies” within a wavelength interval or “apparent quantum yields” in the case of using monochromatic …

Nanoparticles And Their Use In Cancer Imaging, Prevention And Treatment, George Gray

Chemistry & Biochemistry Student Projects

No abstract provided.

Tomatine And Furocoumarins: Toxins In Commonly Consumed Plants, Julia Noonan

Chemistry & Biochemistry Student Projects

No abstract provided.

An Overview Of Dynamic Heterogeneous Oxidations In The Troposphere, Elizabeth A. Pillar-Little, Marcelo I. Guzman

Chemistry Faculty Publications

Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. …

Acetylcholinesterase Biosensor Platform Based On Bp2000 For The Detection Of Carbaryl, Ming-Han Zhang, Jun-Qiao Jiang, Jun-Jie Ge, Wei Xing

Journal of Electrochemistry

With the purpose of providing a new method for carbaryl (a pesticide) detection, on the basis of the principle that acetylcholinesterase (AChE) activity can be restrained by carbaryl, an AChE biosensor platform based on BP2000 (as a fixation) was constructed by dropping method. As a result, it revealed that AChE immobilized on BP2000 maintained its catalytic activity for acetylcholine (ATCl), and due to the introduction of the BP2000 material, the effective electrochemical surface area of the modified electrode was enlarged. In addition, the electrochemical oxidation at the modified electrode occurred at low potential (0.630 V) accompanied by proton transmission. The …

Enhanced Acidity Of Acetic And Pyruvic Acids On The Surface Of Water, Alexis J. Eugene, Elizabeth A. Pillar, Agustín J. Colussi, Marcelo I. Guzman

Chemistry Faculty Publications

Understanding the acid–base behavior of carboxylic acids on aqueous interfaces is a fundamental issue in nature. Surface processes involving carboxylic acids such as acetic and pyruvic acids play roles in (1) the transport of nutrients through cell membranes, (2) the cycling of metabolites relevant to the origin of life, and (3) the photooxidative processing of biogenic and anthropogenic emissions in aerosols and atmospheric waters. Here, we report that 50% of gaseous acetic acid and pyruvic acid molecules transfer a proton to the surface of water at pH 2.8 and 1.8 units lower than their respective acidity constants pK_{a …}

Novel Relative Spontaneous Ignition Temperature Determination Using Carbon Dioxide Onset With Sta/Ir, Antonio David Trevino

Electronic Theses and Dissertations

Simultaneous thermal analysis, coupled with infrared spectroscopy (STA/IR), was utilized to monitor the evolution of gaseous products during the thermal degradation of samples from Triadica sebifera (Chinese tallow), Ligustrum sinense (Chinese privet), and Ilex vomitoria (yaupon) plants. Identification of carbon dioxide was successful with a spectral match of 90.2 percent and further used in the determination of relative spontaneous ignition temperature, or RSIT. The RSIT value during the growing season for Chinese tallow, Chinese tallow stem, Chinese privet, and Yaupon were 208.4°C, 250.3°C, 210.1°C, and 232.3°C respectively. During the dormant seasons, the values for Chinese tallow stem, Chinese privet, and …

Investigation Of Vaporization Enthalpies And Vapor Pressures Of Organic Compounds By Correlation Gas Chromatography, Carissa Nelson

Dissertations

Thermodynamic properties of organic compounds are useful to scientists and manufacturers in many areas of research and technology. This work focuses on measuring and reporting these properties on materials of commercial, environmental and scientific interest. Vaporization enthalpies and vapor pressures of several organic compounds have been studied using correlation gas chromatography (CGC) and are reported here as well as in recent publications. The CGC method allows for the indirect measurement of these properties in instances where these materials are available only in mixtures or in very small amounts.

The qualities of these measurements for any chosen target are directly related …

Cross Photoreaction Of Glyoxylic And Pyruvic Acids In Model Aqueous Aerosol, Sha-Sha Xia, Alexis J. Eugene, Marcelo I. Guzman

Chemistry Faculty Publications

Aerosols of variable composition, size, and shape are associated with public health concerns as well as with light-particle interactions that play a role in the energy balance of the atmosphere. Photochemical reactions of 2-oxocarboxylic acids in the aqueous phase are now known to contribute to the total secondary organic aerosol (SOA) budget. This work explores the cross reaction of glyoxylic acid (GA) and pyruvic acid (PA) in water, the two most abundant 2-oxocarboxylic acids in the atmosphere, under solar irradiation and dark thermal aging steps. During irradiation, PA and GA are excited and initiate proton-coupled electron transfer or hydrogen abstraction …

Development Of Chemistry Activities For Local Outreach In Stem, Emily Knight

Chemistry & Biochemistry Student Projects

Introduction: This research project was started because of an increase in outreach opportunities for the Department of Chemistry and Biochemistry. For similar opportunities, we now have bins of content that are simple to use, encouraging more students to participate in volunteer research.

Purpose: to find, modify, and/or create grade-level appropriate labs and demonstration activities for 5th-8th graders, with a specific focus on activities hat involve easily available components. These activities are intended to be used for outreach to local schools by chemistry student volunteers and released online to act as a resource for teachers.

Educational Resources: Polymers, Emily Knight

Chemistry & Biochemistry Student Projects

The document is meant to act as a resource for elementary through middle school teachers, featuring a science activity connected to Indiana state standards with grade-appropriate science connections aimed toward 5th, 6th, 7th, and 8th grade.

This document contains 3 polymer-based activities demonstrating different properties of polymers - the physical characteristics, possible absorbency, and elasticity. These activities can be abbreviated and used in rotating stations, planned over multiple days, or you can pick on that fits best with the classroom environment.

Educational Resources: Ionic Matching, Emily Knight

Chemistry & Biochemistry Student Projects

The document is meant to act as a resource for elementary through middle school teachers, featuring a science activity connected to Indiana state standards with grade-appropriate science connections aimed toward 5th, 6th, 7th, and 8th grade.

The entire point of this piece is simply to introduce balancing charges in ionic compounds. This is a simpler method to get students thinking about the idea, which also makes it suitable for pre-high school students. It gives a visual representation of how charges balance and cow cations pair with anions. At this level, it is very similar to least common denominator calculations.

Educational Resources: Homemade Fluorometer, Emily Knight

Chemistry & Biochemistry Student Projects

The document is meant to act as a resource for elementary through middle school teachers, featuring a science activity connected to Indiana state standards with grade-appropriate science connections aimed toward 5th, 6th, 7th, and 8th grade.

Educational Resources: Exchange Rates And Unit Conversion, Emily Knight

Chemistry & Biochemistry Student Projects

The document is meant to act as a resource for elementary through middle school teachers, featuring a science activity connected to Indiana state standards with grade-appropriate science connections aimed toward 5th, 6th, 7th, and 8th grade.

Students might have experience in 3rd-6th grade with converting basic ideas such as volume and measurements. This is intended to expand that idea and introduce the mole. It's also a general interactive conversion/exchange activity. All items in here are just based on what we had available and convenient, so feel free to swap out items such as rubber stoppers with something more easily available …

Educational Resources: Curie Point Engine, Emily Knight

Chemistry & Biochemistry Student Projects

The document is meant to act as a resource for elementary through middle school teachers, featuring a science activity connected to Indiana state standards with grade-appropriate science connections aimed toward 5th, 6th, 7th, and 8th grade.

The Curie point of a metal is the temperature at which it loses its magnetic characteristics. Heat can cause magnets to stop being magnetic, which is why heating up magnets is not advised. The engine works because the Curie point of nickel is 354 degrees Celsius, a temperature that can be reached with a simple candle flame. Included are instructions about how to build …

Educational Resources: Magnets, Emily Knight

Chemistry & Biochemistry Student Projects

No abstract provided.

Carbon Composite Fe3O4 Nanoparticles Based Electrochemical Sensor For Hydrogen Peroxide Detection, Si-Yu Zhang, Hui-Juan Wang, Shu-Fang Li, Jian-Ying Qu

Journal of Electrochemistry

In this work, a novel hydrogen peroxide electrochemical sensor was constructed with ferroferric oxide (Fe₃O₄) magnetic nanoparticles, which demonstrated good electrocatalytic activity for hydrogen peroxide. There existed a good linear relationship between the concentration of hydrogen peroxide and the oxidation peak current in the range of 1.00 × 10^-6 ~ 1.00 × 10^-3 mol·L^-1 (R = 0.9980) with the detection limit of 6.60 × 10-7 mol·L^-1. The sensor exhibited good anti-interference ability, high reproducibility and stability.

Steric Effects Of Alkyl Ammonium Salts On The Combustion Of Exchanged Smectite Clays, Celeste A. Keith

Electronic Theses and Dissertations

Bomb calorimetry was explored as a new method for determining the cation exchange capacity (CEC) of clays. Smectite clays were modified with several alkyl ammonium salts varying in number of carbons and the spatial orientation of the carbons about the central nitrogen atom. The clays used, standards purchased from the Source Clay Repository, have CECs of 44, 80, 88, and 120 meq/100 g. Theoretically, the combustion energy of the organo-clays should be approximately the same for each salt. Any differences in energy would be due to the different structures of the salts and how they are oriented in the interlamellar …

Photoelectrochemical Studies On Non-Noble Metal Based Catalysts Towards Tandem Solar Water Splitting, Arun Siddarth Sridhar

Dissertations

Photoelectrochemical (PEC) water splitting makes direct use of solar energy incident on semiconductor photoelectrodes, and it is a convenient, economic option to produce high purity hydrogen at low temperatures. The use of multiple light absorbers can increase overall solar energy utilization and provide a solution to the trade-off between overall band gap and band edge positioning of photoelectrodes specific to solar water oxidation and water reduction. The study of non-noble metal based catalysts for hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) are essential for economic practical commercialization of photo-electrolyzers. This dissertation focuses on the use of a variety …

A Label-Free Immunosensor Based On K3[Fe(Cn)6] And Aldehyde-Functionalized Pyridinium, Xia Hu, You-Ming Shen, Guang-Yu Shen

Journal of Electrochemistry

A novel aldehyde-functionalized pyridinium was successfully synthesized. Using K₃[Fe(CN)₆] as a redox species modified on the surface of the electrode through Poly(diallyldimethylammonium chloride), we developed a label-free immunosensor based on aldehyde-functionalized pyridinium that was applied to simplify antibody immobilization on the electrode surface, in which no additional chemical cross-linking was required. In addition, the introduction of K₃[Fe(CN)₆] on the surface of electrode avoided the use of other redox species in the electrolyte solution. Under the optimal experimental conditions, differential pulse voltammetry (DPV) signals corresponding to different α-Fetoprotein (AFP) concentrations were measured. After …

Simulation Analysis In Dynamic Performance Of Proton Exchange Membrane Fuel Cell Under Starting Condition, Yan Xiao, Ying-Jie Chang, Wei Zhang, Qiu-Hong Jia

Journal of Electrochemistry

Based on the equivalent circuit model, by considering both the dynamic gas pressure model and the dynamic heat transfer model, a lumped parameter model is developed. The start process of the fuel cell is simulated by using SIMULINK software. The undershoot of the voltage is observed from the simulation results, and the response time of the voltage is basically the same as that of the fuel cell temperature, which indicates that the temperature has great influence on the dynamic performance of the fuel cell. From the perspective of the temperature, the dynamic responses of the thermodynamic potential, the activation overvoltage, …

Evaluation Of Vaporization Enthalpies And Vapor Pressures Of Various Aroma And Pharmacologically Active Compounds By Correlation Gas Chromatography, Daniel Simmons

Theses

Scientists in the pharmaceutical, food, and aroma industries can benefit from reliable thermochemical data. Vaporization enthalpy and vapor pressure data are not available for all compounds. Furthermore, some literature data is conflicting. The goal of this work was to use a method called correlation gas chromatography (CGC) to generate reliable vaporization enthalpy data in instances where other experimental methods are not applicable. Vapor pressures of the targets were also calculated in cases where the required literature data on the standards used in this technique were available.

CGC involves making a standard cocktail that includes a mixture of standards and one …

Structural Evolution Of Gold-Doped Bismuth Clusters AubiN– (N = 4−8), Seema Pande, Tian Jian, Navneet S. Khetrapal, Lai-Sheng Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The structures of gold-doped bismuth clusters, AuBi_n⁻ (n = 4−8), are investigated through a joint photoelectron spectroscopy and density functional theory (DFT) study. Well-resolved photoelectron spectra are obtained at several photon energies. Global minimum searches coupled with DFT calculations yield low-lying structures, whose relative energies are further evaluated by single-point energy calculations at the CCSD(T) level of theory. Vertical detachment energies are calculated with the inclusion of spin−orbit effects to compare with the experimental data. Three-dimensional structures are found to be dominant in this size range, while a planar low-lying isomer is observed only for AuBi_{4 …}