Physical Chemistry Commons^™

Unraveling The Mechanism Of Selective Ion Transport In Hydrophobic Subnanometer Channels, Hui Li, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Recently reported synthetic organic nanopore (SONP) can mimic a key feature of natural ion channels, i.e., selective ion transport. However, the physical mechanism underlying the K⁺/Na⁺ selectivity for the SONPs is dramatically different from that of natural ion channels. To achieve a better understanding of the selective ion transport in hydrophobic subnanometer channels in general and SONPs in particular, we perform a series of ab initio molecular dynamics simulations to investigate the diffusivity of aqua Na⁺ and K⁺ ions in two prototype hydrophobic nanochannels: (i) an SONP with radius of 3.2 Å, and (ii) single-walled …

Medium-Sized Au40(Sr)24 And Au52(Sr)32 Nanoclusters With Distinct Gold-Kernel Structures And Spectroscopic Features, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We have analyzed the structures of two medium-sized thiolateprotected gold nanoparticles (RS-AuNPs) Au₄₀(SR)₂₄ and Au₅₂(SR)₃₂ and identified the distinct structural features in their Au kernels [Sci. Adv., 2015, 1, e1500425]. We find that both Au kernels of the Au₄₀(SR)₂₄ and Au₅₂(SR)₃₂ nanoclusters can be classified as interpenetrating cuboctahedra. Simulated X-ray diffraction patterns of the RS-AuNPs with the cuboctahedral kernel are collected and then compared with the X-ray diffraction patterns of the RS-AuNPs of two other prevailing Au-kernels identified from previous experiments, namely the Ino-decahedral kernel and icosahedral kernel. …

Extremely Strong Tubular Stacking Of Aromatic Oligoamide Macrocycles, Mark A. Kline, Xiaoxi Wei, Ian J. Horner, Rui Liu, Shuang Chen, Si Chen, Ka Yi Yung, Kazuhiro Yamato, Zhonghou Cai, Frank V. Bright, Xiao Cheng Zeng, Bing Gong

Xiao Cheng Zeng Publications

As the third-generation rigid macrocycles evolved from progenitor 1, cyclic aromatic oligoamides 3, with a backbone of reduced constraint, exhibit extremely strong stacking with an astoundingly high affinity (estimated lower limit of K_dimer > 10¹³ M^–1 in CHCl₃), which leads to dispersed tubular stacks that undergo further assembly in solution. Computational study reveals a very large binding energy (–49.77 kcal mol^–1) and indicates highly cooperative local dipole interactions that account for the observed strength and directionality for the stacking of 3. In the solid-state, X-ray diffraction (XRD) confirms that the aggregation of 3 results …

A Molecular-Level View Of The Physical Stability Of Amorphous Solid Dispersions, Xiaoda Yuan

Theses and Dissertations--Pharmacy

Many pharmaceutical compounds being developed in recent years are poorly soluble in water. This has led to insufficient oral bioavailability of many compounds in vitro. The amorphous formulation is one of the promising techniques to increase the oral bioavailability of these poorly water-soluble compounds. However, an amorphous drug substance is inherently unstable because it is a high energy form. In order to increase the physical stability, the amorphous drug is often formulated with a suitable polymer to form an amorphous solid dispersion. Previous research has suggested that the formation of an intimately mixed drug-polymer mixture contributes to the stabilization …

Electronic Structures And Electronic Spectra Of All-Boron Fullerene B40, Rongxing He, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

This study is motivated by the recent discovery of the first all-boron fullerene analogue, a B₄₀ cluster with D_2d point-group symmetry, dubbed borospherene (Nat. Chem., 2014, 6, 727). Insight into the electronic structures and spectral properties of B₄₀ is timely and important to understand the borospherene and the transition from open-ended plate or ribbon-like structures to a hollow-cage structure at B₄₀. Optimized geometries of borospherene B₄₀ for both the ground state and the first excited state allow us to compute spectral properties including UV-vis absorption, infrared (IR) and Raman spectra. Highly resolved absorption and …

One-Step Synthesis Of Pani/Nihcf Hybrid Film Using Unipolar Pulse Electrodeposition And Its Electrocatalytic Reduction Performance For H2O2 Detection, Sen-Liang Liao, Xiu-Min Li, Xiao-Gang Hao, Yan-Hong Wang, Chun-Feng Xue, Yong-Hong Wang

Journal of Electrochemistry

Organic–inorganic hybrid films composed of polyaniline/nickel hexacyanoferrate (PANI/NiHCF) were fabricated on platinum substrates using unipolar pulse one-step electrodeposition. The deposition mechanism of hybrid film was proposed: Due to high potential of unipolar pulse electrodeposition, which avoided the reduction of Fe(CN)₆^3-, the films with high electrocatalytic property and “insoluble” form of NiHCF were achieved. The morphology and composition of PANI/NiHCF hybrid film were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). The effect of pulse potential on the electrochemical performance of hybrid film was investigated in detail. Results showed that …

Electrochemiluminescence Imaging Focusing: Array Analysis And Visualization Of Latent Fingerprints, Zhen-Yu Zhou, Lin-Ru Xu, Bin Su

Journal of Electrochemistry

Electrochemiluminescence (ECL) imaging, as a novel and powerful analytical method, possesses many distinct advantages, including simplicity, high controllability, high-throughput and visualization. In recent years, it has been used in developing portable and miniaturized ECL sensor, and made remarkable achievements. In this review, the progress of ECL imaging, focusing on array analysis and visualization of latent fingerprints, has been introduced briefly based on our recent investigations and an attempt has been made to propose the future research trend.

Direct Electrochemistry And Glucose Biosensing Of Glucose Oxidase-Gold Nanoparticles Composite Synthesized By Enzyme Method, Fang He, Xiao-Li Qin, Ying-Chun Fu, Chao Chen, Qing-Ji Xie, Shou-Zhuo Yao

Journal of Electrochemistry

Glucose oxidase (GOx)-gold nanoparticles (AuNPs) composite was synthesized by the one-pot enzyme reaction in the mixture solution of NaAuCl₄, GOx and glucose, and a Nafion/GOx-AuNPs/glassy carbon electrode was fabricated by the cast-coating method to examine the direct electrochemistry of GOx and the biosensing performance on this electrode. Such a GOx-AuNPs composite showed good direct-electrochemistry activity and bioactivity of GOx, probably because the enzyme-mediated AuNPs are close to the redox active centers of GOx. This enzyme electrode exhibited a linear amperometric response to glucose concentration (0.54 mmol·L^-1) at -0.4 V (vs. SCE), and a detection limit of …

Preparation Of Surface Molecularly Imprinted Magnetic Nanoparticles For Hemoglobin Sensing, Chun-Fang Huang, Gui-Hong Yao, Jian-Ding Qiu

Journal of Electrochemistry

Surface molecularly imprinted magnetic nanoparticles (NPs) were prepared by employing dopamine (DA) as a functional monomer, hemoglobin (Hb) as a template, H₂PtCl₆ as an oxidant triggered DA polymerization on the surface of the Fe₃O₄ NPs. The Hb and the formed platinum nanoparticles (PtNPs) were embedded into the polydopamine (PDA). After removal of the Hb, the surface molecularly imprinted magnetic nanoparticles (imprinted Fe₃O₄/PDA-PtNPs) were formed, and then simply immobilized on the magnetic glassy carbon electrode (imprinted Fe₃O₄/PDA-PtNPs/MGCE) for Hb sensing. The imprinted Fe₃O₄/PDA-PtNPs …

Enzyme-Based Dna Electrochemical Biosensors: Recent Trends, Chun-Shui Lin, Yi-Ru Wang, Xi Chen

Journal of Electrochemistry

DNA electrochemical sensors have greatly promoted the development of biosensors for their high sensitivity, good selectivity, short analysis time and low cost. To further improve the detection sensitivity and selectivity, protein enzymes, functional nucleic acid enzymes etc. are often used due to the advantages of high catalytic efficiency and specificity. This review demonstrates the research progress of electrochemical sensors based on enzymatic amplification and analyses some existing problems of electrochemical sensors.

Resolve Mono-Electronic Process In The Voltammetric Behaviors Of Multi-Redox Bis-Coenzyme Q0, Hao Zhou, Yi-Tao Long

Journal of Electrochemistry

A widely held concept in electrochemistry is that truly elementary electron-transfer reactions always involve the exchange of one electron, therefore, an overall process involving a change of n electrons must involve n distinct electron-transfer steps. It is highly desirable to resolve multiple-step electron transfer reactions into each electron transfer step. The electrochemical behaviors of coenzyme Q₀ and methylene-bridged Bis-coenzyme Q₀ were investigated by cyclic voltammetry and square wave voltammetry in nonaqueous dichloromethane containing 0.15 mol·L^-1 Bu₄NClO₄ as the supporting electrolyte. The redox reaction of coenzyme Q₀ is well described as two chemically reversible …

Catechol Oxidation By Ozone And Hydroxyl Radicals At The Air-Water Interface, Elizabeth A. Pillar, Robert C. Camm, Marcelo I. Guzman

Chemistry Faculty Publications

Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air–water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon …

Electrochemical And Spectroscopic Studies Of Ethanol Oxidation On Nano-Cubic Pt Modified By Tin Adatoms, Lu Rao, Bin-Wei Zhang, Yan-Yan Li, Yan-Xia Jiang, Shi-Gang Sun

Journal of Electrochemistry

The nano-cubic Pt modified by tin (Sn) was synthesized and used to investigate the role of this adatom played in the ethanol oxidation. The onset potential of ethanol oxidation was significantly shifted negatively which can be forward about 300 mV when the coverage of Sn (θSn)was 0.9. The electrtochemical in situ FTIR result demonstrated that the amount of CO₂ increased first, and then decreased with θSn increased, and reached the maximun when θSn was 0.38. Furthermore, the formation of acetic acid could be observed at very low potential (-0.05 V) after modifying Sn adatom, and the amount of acetic …

Resonant Two-Photon Ionization Studies Of Non Covalent Interactions In Halo Aromatic Clusters And Spin-Orbit Coupling Modeling In Mono-Halocarbenes, Silver Nyambo

Dissertations (1934 -)

Non-covalent interactions in halobenzenes (PhX) (X=F, Cl, Br) and phenylamine (C₆ H₅ NH₂ ) have been studied here using resonance two-photon ionization (R2PI) spectroscopy combined with a linear TOF-mass spectrometer. Their interaction with polar molecules in form of ammonia (NH ₃ ) and trifluorohalomethanes (CF₃ X) has also been studied. DFT and TD-DFT calculations using M06-2X functionals were carried out on different cluster conformations to compliment experimental results. A general trend of broadness in homogenous dimers (PhX)₂ , has been attributed to mainly the presence of multiple cluster isomers and Frank-Condon activity in the low …

Electrochemical And Surface Enhanced Raman Spectroscopic Studies Of Benzimidazole On Nickel Electrode, Ping-Jie Wei, Ya-Xian Yuan, Min-Min Xu, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

By measuring cyclic voltammograms and polarization curves, the inhibition effects of benzimidazole (BMIH) concentration in acetonitrile system on a nickel electrode were investigated. It was found that the oxidation and the corrosion potentials shifted positively, and the oxidation current decreased with the increase in the concentration of BIMH. Potential dependent adsorption and film formation behavior of BMIH on the nickel electrode were investigated by in situ SERS spectroscopy. With the potential moving from negative direction to positive direction, the complexes made of BIMH and nickel were formed, preventing the nickel electrode from corrosion. In addition, the 0.001 mol·L^-1 of …

In-Situ Afm Force Curve Investigations On Layered Structures Of Au(111)-Ionic Liquid Interfaces And Temperature Dependence, Xiao Zhang, Yun-Xin Zhong, Jia-Wei Yan, Bing-Wei Mao

Journal of Electrochemistry

By utilizing in-situ AFM force curve measurements systematic investigations have been carried out on Au(111)-ionic liquid interface in BMIPF₆ and OMIPF₆ of imidazolium-based ionic liquids with different lengths of alkyl side chains. The temperature dependence of the number, thickness and stability of the layered structures of each system are studied by performing AFM force curve measurements at potentials far negative of the PZC. The layered structures at Au (111)/BMIPF₆ interface are composed of two charged interior layers and two neutral exterior layers at -1.0 V, while those at Au (111)/OMIPF₆ interface only one charged interior layer …

Investigation Of The Dynamics Of Photocarriers During Photoelectrochemical Water Splitting By Combination Of Photoelectrochemistry And Transient Absorption Spectroscopy, Wen-Hua Leng

Journal of Electrochemistry

Semiconductor photoelectrochemical hydrogen production is an important and promising technology for utilizing solar energy. The efficiency of hydrogen production depends on the efficiencies of separation and transport of photo-generated carriers. A deep understanding of the behavior of these processes has guiding significance for designing efficient solar hydrogen device. photoelectrochemical and transient absorption spectroscopy methods are powerful tool for studying the microscopic dynamics and mechanism of photocatalytic reaction. This review describes the part of the latest results of the author regarding the semiconductor photoelectrochemical hydrogen production obtained by these methods,and the problems and future research priorities in this field are proposed.

High Sensitive Detection Of Cd(Ii) And Pb(Ii) Based On Antimony-Film Covered Pencil Core Electrodes, Shan Chen, Zhao-Yan Zheng, Yi-Min Fang, Li-Qing Zheng, Jian-Jun Sun

Journal of Electrochemistry

In this paper, a pencil core was used as the substrate for an antimony-film electrode for simultaneous detection of Cd(II) and Pb(II) by square-wave anodic stripping voltammetry (SWASV). With the deposition time of 180 s, the low limit of detection (LOD) for the electrode was determined to be 0.075·g?L-1 for Cd(II), while 0.13·g·L-1 for Pb(II) with good reproducibility in low pH solutions (pH = 2). The results show a much lower LOD than that of bismuth-film pencil core electrode. Finally, this antimony-film electrode was successfully applied to determine Cd(II) and Pb(II) in tap water.

A Sensitive And Label-Free Electrochemical Aptasensor Based On Signal Amplification Of Carbon Nanotubes, Chun-Yan Deng, Hui-Min Fan, Juan Xiang, Yuan-Jian Li

Journal of Electrochemistry

A label-free electrochemical sensing electrode for highly sensitive detection of adenosine was constructed based on the signal amplification of carbon nanotubes (CNTs). The change in the interfacial feature of the modified electrode was characterized by electrochemical impedance spectroscopy. Using [Ru(NH₃)₆]³⁺ as the signaling moiety, adenosine with concentrations as low as 0.027 nmol·L^-1 can be selectively detected. Additionally, the fabrication of this present aptasensor was simple, time-saving and cost-effective. Compared with other reported aptasensors, the proposed aptasensor had advantages of excellent sensitivity, selectivity and simplicity, which plays a potential role in development of aptasensor.

Does A Plastron Improve Heat Transfer?, Madani A. Khan, Jeffrey Alston, Andrew Guenthner

STAR Program Research Presentations

Superamphiphobic surfaces strongly repel both water and oils. In this work, aluminum coupons are processed by sanding with various grit of sand paper to impart microscale roughness. Subsequent submersion of the aluminum substrate in boiling water grows nanoscale grass-like structures. The oxide layer of Al is slightly soluble in water. During a fast diffusion/equilibrium, Al₂O₃ nanograss grows on the surface. A low energy coating is then deposited on the surface. The micro and nanoscale features create re-entrant structures that trap air enabling contact liquid to be in a Cassie-Baxter state. Superamphiphobicity of the samples were confirmed by …

Heat Release Of Polyurethanes Containing Potential Flame Retardants Based On Boron And Phosphorus Chemistries, Vladimir Benin, Bastien Gardelle, Alexander Morgan

Chemistry Faculty Publications

Using a polyurethane of methylene diphenyl isocyanate and 1,3-propane diol, several new non-halogenated aromatic boron and phosphorus flame retardants were evaluated for heat release reduction potential using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods, and were then analyzed via spectroscopic methods to determine if the flame retardant was still present in the final product. PCFC testing on the resulting products showed that the flame retardant molecule can have different effects on heat release depending upon how it is mixed into the polyurethane. Some …

Determination Of Corrosion Inhibitor Lubricity Improver In Jet Fuel By Liquid Chromatography-Electrospray Ionization Mass Spectrometry, David W. Johnson, Milissa Flake, Ryan Adams

Chemistry Faculty Publications

Military jet fuel (JP-8) is very similar to commercial jet fuel (Jet A) except for the presence of three additives, fuel system icing inhibitor, corrosion inhibitor–lubricity improver (CI-LI), and antistatic additive, which are added to improve characteristics of JP-8. Of particular interest is the CI-LI additive; the most common active ingredient is a dimer of linoleic acid. This article focuses on quantification of the active ingredient in the CI-LI additive by liquid chromatography–mass spectrometry (LC–MS). This method will allow the determination of CI-LI content in military jet fuel samples.

Gas-Phase Ion/Ion Reactions Of Biomolecules: An Examination Of Carboxylate Reactivity And Arginine Based Non-Covalent Complexes, Nathan Zachary Barefoot

Open Access Theses

The advent of Electrospray Ionization with the ability to generate multiply charges ions has contributed significantly to the study of gas-phase ion/ion reactions. With the tools available in mass spectrometry it has been shown that these reactions are effective at transforming one type of gaseous ion into another through a series of reactions. This work examines some of these reactions and their application to field of proteomics specifically focusing on the amino acids of arginine and lysine. NHS reagents have been shown to react to both of these molecules with in the gas-phase under different conditions but have relies on …

Surface Enhanced Raman Spectroscopic Studies Of Pyridine Adsorbed On Ti/Au@Sio2 Film Electrode, Min-Min Xu, Ke Liu, Qing-Hua Guo, Jian-Lin Yao

Journal of Electrochemistry

This study was performed based on shell-isolated nanoparticles-enhanced Raman spectroscopy (SHINERS) technology. The Au@SiO₂ nanoparticles were prepared and characterized by TEM and cyclic voltammetry. It was shown that the shell of SiO₂ was compact. The high quality signal measured by surface enhanced Raman spectroscopy (SERS) was obtained from the adsorbed pyridine on Ti/Au@SiO₂ electrode. The origin of the SERS signals was further confirmed by testing Pt and Ni electrodes. In addition, potential dependent adsorption behavior was investigated. It was found that pyridine was adsorbed parallel on the surface from -0.1 V to -0.6 V, and converted to …

Horseradish Peroxidase-Attapulgite Clay Nanocomposites: Fabrication And Application To Sensing The Extracellular H2O2 Released From Cells, Ping Wu, Chen-Xin Cai

Journal of Electrochemistry

The nanostructured attapulgite clay was employed as a support matrix for immobilizing horseradish peroxidase (HRP). FTIR and electrochemical methods demonstrated that HRP had been effectively assembled on attapulgite surface with the formation of HRP-attapulgite nanocomposites. The HRP-attapulgite hybrid was deposited on the glassy carbon (GC) electrode forming the HRP-attapulgite/GC electrode. Cyclic voltammetric results showed a pair of well-defined redox peaks, which were ascribed to direct electron transfer (DET) of HRP, with the formal potential E₀′ = -335 mV (vs. SCE) in the phosphate buffer solution (PBS, pH 7.0). The dependence of E₀′ on solution pH indicated …

23Na Mas Nmr Spectroscopic Study Of Na2Mnpo4F As Cathode Material For Sodium-Ion Battery, Xu Hou, Gui-Ming Zhong, Xiao-Chen Lin, Zi-Geng Liu, Xiao-Biao Wu, Yong Yang

Journal of Electrochemistry

The Na₂MnPO₄F is one of the promising cathode materials for the sodium ion batteries. In the paper, we employed the ex situ X-ray diffraction and solid state NMR techniques to study the charge and discharge processes of this material, including the crystal structure and sodium sites changes. The ex situ x-ray diffraction patterns showed that two new diffraction peaks could be observed at 31^o and 36^o indicating an intermediate phase formed with the extraction of Na⁺. From the ²³Na MAS NMR spectrum of the material, three peaks were seen at -209 …

Nitroxide Radicals For Low Frequency Electron Paramagnetic Resonance Imaging (Epri), Joshua R. Biller

Electronic Theses and Dissertations

Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties such as spin lattice relaxation times, spin packet linewidths, and nuclear hyperfine splitting. Initial measurements of relaxation times for six low molecular weight nitroxides at X-band stimulated further measurement at frequencies between 250 MHz and 34 GHz. The impact of tumbling was studied with perdeuterated 2,2,6,6-tetramethyl-4-piperidinyl-1-oxyl (PDT) in five solvents with viscosities resulting in tumbling correlation times, τ_R, between 4 and 50 ps. A set of three ¹⁴N/¹⁵N pairs of nitroxides in water was selected such that τ_R varied between …

Electrically Controlled Formation And Release Of Admicelles For Solid Phase Extraction, Sukyeon Lee

Masters Theses & Specialist Projects

Solid phase extraction is one of the most widely used methods to concentrate diluted compounds in a solution. Substances can be extracted into admicelles and hemimicelles, which are surface adsorbed micelles and surfactant monolayers, respectively. Investigations of the electrical control of surfactants on surfaces for the purpose of analyte preconcentration prior to chromatographic analysis are presented. The surfactant layer serves as the “stationary phase” in a solid phase extraction sorbent scenario. Analytes are adsorbed on this layer, and then released from the solid phase via surfactant removal. The attachment and removal of the surfactant are controlled by means of an …

The Analysis Of The Decomposition Of Hydrogen Peroxide Using A Schiff Base Copper Complex By Cyclic Voltammetry, Gavin James Rustin Mr.

Undergraduate Honors Theses

Copper(II) complexes of Schiff bases can be used in the catalysis of hydrogen peroxide to create water and oxygen. The mechanism and the kinetics of this disproportionation reaction by a dimeric copper(II) complex [CuSALAD]₂ are studied in this experiment, where SALAD refers to a Schiff Base ligand formed from salicyaldehyde and 1S,2S-D(+)-1-phenyl-2-amino-1,3-propanediol. By using cyclic voltammetry, the oxidation-reduction processes of a reaction may be monitored. The [CuSALAD]­₂ is initially reacted with a base such as imidazole to form the catalytic species, and the ratio of the copper(II) complex to the imidazole was found to be 1:4, consistent with …

Investigation Of Energy Alignment Models At Polymer Interfaces, Wenfeng Wang

USF Tampa Graduate Theses and Dissertations

The presented study investigated the Induced Density of Interface States (IDIS) model at different polymer interfaces by using photoemission spectroscopy in combination with electrospray deposition.

In recent years, organic electronics have attracted considerable attention due to their advantages of low-cost and easy-fabrication. The performance of such devices crucially depends on the energy barrier that controls the interface charge transfer. A significant effort has been made to explore the mechanisms that determine the direction and magnitude of charge transfer barriers in these devices. As a result of this effort, the IDIS model was developed to predict the energy alignment at metal/organic …