Materials Chemistry Commons^™

Surprising Impact Of Remote Groups On The Folding–Unfolding And Dimer-Chain Equilibria Of Bifunctional H-Bonding Unimers, Rui Liu, Shuang Cheng, Erin S. Baker, Richard D. Smith, Xiao Cheng Zeng, Bing Gong

Xiao Cheng Zeng Publications

Oligoamide 1, consisting of two H-bonding units linked by a trimethylene linker, was previously found to form a very stable, folded dimer. In this work, replacing the side chains and end groups of 1 led to derivatives that show the surprising impact of end groups on the folding and dimer-chain equilibria of the resultant molecules.

Unraveling The Hidden Function Of A Stabilizer In A Precursor In Improving Hybrid Perovskite Film Morphology For High Efficiency Solar Cells, Zhengguo Xiao, Dong Wang, Qingfeng Dong, Qi Wang, Wei Wei, Jun Dai, Xiwei Zheng, Jinsong Huang

Xiao Cheng Zeng Publications

The morphology of the organometal trihalide perovskite (OTP) plays a critical role in the performance of solar cell devices. Nevertheless it has been frequently reported that the morphology of OTP films tends to be different in different laboratories even with the same film preparation procedure, which makes it very difficult to compare and understand the material and device physics. Here, we unravel a critical role of the H₃PO₂ stabilizer in HI, which has been largely ignored, in controlling the morphology of the perovskite films. The H₃PO₂ stabilizer in HI solution introduces MAH₂PO …

Two-Dimensional Interlocked Pentagonal Bilayer Ice: How Do Water Molecules Form A Hydrogen Bonding Network?, Weiduo Zhu, Wen- Hui Zhao, Lu Wang, Di Yin, Min Jia, Jinlong Yang, Xiao Cheng Zeng, Lan-Feng Yuan

Xiao Cheng Zeng Publications

The plethora of ice structures observed both in bulk and under nanoscale confinement reflects the extraordinary ability of water molecules to form diverse forms of hydrogen bonding networks. An ideal hydrogen bonding network of water should satisfy three requirements: (1) four hydrogen bonds connected with every water molecule, (2) nearly linear hydrogen bonds, and (3) tetrahedral configuration for the four hydrogen bonds around an O atom. However, under nanoscale confinement, some of the three requirements have to be unmet, and the selection of the specific requirement(s) leads to different types of hydrogen bonding structures. According to molecular dynamics (MD) simulations …

Near-Barrierless Ammonium Bisulfate Formation Via A Loop-Structure Promoted Proton-Transfer Mechanism On The Surface Of Water, Lei Li, Manoj Kumar, Chongqin Zhu, Jie Zhong, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

In the atmosphere, a well-known and conventional pathway toward the formation of ammonium sulfate is through the neutralization of sulfuric acid with ammonia (NH₃) in water droplets. Here, we present direct ab initio molecular dynamics simulation evidence of the formation of ammonium bisulfate (NH₄HSO₄) from the hydrated NH₃ and SO₃ molecules in a water trimer as well as on the surface of a water droplet. This reaction suggests a new mechanism for the formation of ammonium sulfate in the atmosphere, especially when the concentration of NH₃ is high (e.g., ∼10 μg …

Resolving The Hono Formation Mechanism In The Ionosphere Via Ab Initio Molecular Dynamic Simulations, Rongxing He, Lei Li, Jie Zhong, Chongqin Zhu, Joseph S. Francisco, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Solar emission produces copious nitrosonium ions (NO⁺) in the D layer of the ionosphere, 60 to 90 km above the Earth’s surface. NO⁺ is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200–220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates—tetrahydrate NO⁺(H₂O)₄ and pentahydrate NO⁺(H₂O)_{5 …}

Probing The Structures Of Gold–Aluminum Alloy Clusters AuXAlY−: A Joint Experimental And Theoretical Study, Navneet S. Khetrapal, Tian Jian, Rhitankar Pal, Gary V. Lopez, Seema Pande, Lai-Sheng Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Besides the size and structure, compositions can also dramatically affect the properties of alloy nanoclusters. Due to the added degrees of freedom, determination of the global minimum structures for multi-component nanoclusters poses even greater challenges, both experimentally and theoretically. Here we report a systematic and joint experimental/theoretical study of a series of gold–aluminum alloy clusters, Au_xAl_y⁻(x + y = 7,8), with various compositions (x = 1–3; y = 4–7). Well-resolved photoelectron spectra have been obtained for these clusters at different photon energies. Basin-hopping global searches, coupled with density functional theory calculations, are used …

Improved High Temperature Stability Of Anatase Tio2 Photocatalysts By N, F, P Co-Doping, Rachel Fagan, Declan Mccormack, Steven Hinder, Suresh Pillai

Articles

Among the three commonly occurring phases (anatase, rutile, and brookite) of TiO2, the anatase form is reported to be the best photocatalyst due to the improved charge-carrier mobility and the greater number of surface hydroxyl groups. The anatase to rutile transition in titania photocatalysts usually occurs at a temperature between 500 °C to 700 °C. Development of a high temperature stable (above 1000 °C) anatase phase is important for various environmental applications (e.g. self-cleaning ceramic tiles, anti-microbial sanitary wares, etc.). In this study, the use of ammonium hexafluorophosphate as a single source dopant (method A) and urea, trifluoroacetic acid and …

Continuous Stationary Phase Gradients For Planar And Column Chromatography, Veeren Dewoolkar

Theses and Dissertations

Surfaces that exhibit a gradual change in their chemical and/or physical properties are termed as surface gradients. Based on the changes in properties they are classified either as physical or chemical gradients. Chemical gradients show variations in properties like polarity, charge, functionality concentration and have found potential applications in fields of biology, physics, biosensing, catalysis and separation science. In this dissertation, surface gradients have been prepared using controlled rate infusion (CRI).

CRI is a simple method in which a surface gradient is formed by carrying out the infusion of organoalkoxysilane in a time-dependent fashion using a set infusion rate. Depending …

The Optimization Of The Synthesis And Characterization Of Vapor-Liquid-Solid Grown Zno Nanowires, Silas R. Fiefhaus

Theses and Dissertations--Chemistry

ZnO nanowires are a promising material with great semiconductor properties. ZnO nanowires were prepared by carbothermal reduction and vapor-liquid-solid growth mechanism. Altering a variety of parameters ranging from mole to mole ratio of ZnO to C all the way to gas flow rate was examined. The nanowires were then characterized and their morphology examined under a SEM to observe what effect the parameter had on the morphology of the nanowires. From the experiments and the parameters tested it was observed that in order to produce the highest quality straight nanowires one should use a mole to mole ratio of ZnO …

Fabrication Of Multifunctional Nanostructured Porous Materials, Ahmed A. Farghaly

Theses and Dissertations

Nanostructured porous materials generally, and nanoporous noble metals specifically, have received considerable attention due to their superior chemical and physical properties over nanoparticles and bulk counterparts. This dissertation work aims to develop well-established strategies for the preparation of multifunctional nanostructured porous materials based on the combination of inorganic-chemistry, organic-chemistry and electrochemistry. The preparation strategies involved one or more of the following processes: sol-gel synthesis, co-electrodeposition, metal ions reduction, electropolymerization and dealloying or chemical etching. The study did not stop at the preparation limits but extended to investigate the reaction mechanism behind the formation of these multifunctional nanoporous structures in order …

Intercalation Of Clo4- Into Hopg Investigated By Ec-Stm, Xiao-Yan Hu, Alice Aliwowe, Jia-Wei Yan, Bing-Wei Mao

Journal of Electrochemistry

The electrochemical intercalation and surface morphology of highly oriented pyrolytic graphite (HOPG) electrode in 2 mol⋅L^-1 HClO₄ were studied by in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV). Based on the step-height changes observed before and after the intercalation, the effects of different step sites on intercalation are compared. The feasibility, reversibility and speed of intercalation are discussed. The intercalation ofClO₄^- into HOPG can be divided into three types depending on the number of graphite layers at the step site: When the layers of graphite are more than three, the intercalation becomes feasible; when …

The Unique Electrochemical Reactivity Of Small Metal Nanoparticles., Rafael A. Masitas

Electronic Theses and Dissertations

This dissertation describes the factors controlling metal nanoparticle (NP) oxidation, using Au oxidation in Br- and Ag oxidation in acid as model systems. We found that the oxidation potential depends on size, surface charge, and electrode material. Size has a dramatic effect, shifting about 200 mV from > 200 nm diameter down to 4 nm diameter. The shift is more dramatic below 4 nm. 2.3 nm average diameter Au NPs oxidized in the 300-500 mV range and 1.5 nm average diameter Au NPs displayed several sharp peaks from 200 mV to as low as -200 mV. These smallest Au NPs show …

Application Of Pd/Graphene Modified Electrode In The Detection Of 4-Chlorophenol, Peng Shi, Bo-Xuan Wang, Quan-Lin Song, Hui Wang, Xin Liu, Zhao-Yong Bian

Journal of Electrochemistry

The Pd/graphene composites were synthesized by a modified Hummers method and NaBH4 reduction process, and then were characterized using XRD, SEM, XPS, and TEM. The Pd/graphene modified glassy carbon electrode (Pd/graphene/GCE) was prepared based on this method. Cyclic voltammetry was used to study the optimum operation conditions for the 4-chlorophenol detection. It was shown that the surface of the graphene was smooth and Pd nanoparticles were uniformly dispersed on graphene. The average particle size was calculated to be 6.5 ± 0.05 nm. These nanoparticles exhibited high catalytic activity and sensitivity toward chlorophenols. PBS with a concentration of 0.1 mol·L^{-1 …}

Effect Of Adsorption Potential On Co Oxidation At Au@Pt Nanoparticles Electrodes, A Surface Enhanced Raman Spectroscopic Study, Pu Zhang, Yi Wei, Yong-Li Zheng, Yan-Xia Chen, Zhong-Qun Tian

Journal of Electrochemistry

The adsorption/oxidation of CO on the 55 nm [email protected] nm Pt nanoparticles electrode in both potentiodynamic and potentiostatic modes were investigated by surface enhanced Raman spectroscopy in a thin layer electrochemical flow cell under controlled mass transport, with the aim of clarifying the origin CO oxidation at lower electrode potentials (in current pre-wave region of corresponding cyclic voltammograms). Our results demonstrated that the CO oxidation kinetics differed significantly from the three kinds of different CO adsorption history, with almost no CO oxidation current in the pre-peak potential region after 0.35 V_RHE CO adsorption with or without subsequent holding the …

Broadband Sum-Frequency Generation Spectroscopic Invstigations Of Thiocyanate On Polycrystalline Au Electrode In Alkaline Solutions, Mei Xu, Jing-Jing Wang, Zhi-Chao Huangfu, Ng Ying Wa, Yu-Han He, Zhao-Hui Wang

Journal of Electrochemistry

Broadband sum frequency generation (BB-SFG) spectroscopy has been used to investigating the potential-dependent adsorption behaviors of thiocyanate ions on polycrystalline Au electrode in alkaline solutions. During the positive scan, a change in the Stark slope (dω_C-N/dE) for C—N stretching mode can be observed in the range of -1.1 V ~ 0.2 V (vs. SCE), which implies that the orientation of adsorbed thiocyanate ions at Au electrode surface changes from N-bound (dω_C-N/dE=45 cm^-1·V^-1) form to S-bound (dω_C-N/dE = 16.2 cm^-1·V^{-1 …}

Fluorinated Metallo Phthalocyanines For Chemical And Biological Catalysis, Hemantbhai H. Patel

Seton Hall University Dissertations and Theses (ETDs)

The rational design of robust oxidation catalysts based on organic molecules is hindered by the presence of labile C-H bonds. We have shown recently that replacing all C-H bonds by a combination of fluoro- and perfluoro-groups in a bioinspired Cytochrome P450 model based on a phthalocyanine, Pc, scaffold results in a stable yet reactive oxidation catalyst. The Pc cobalt complex catalyzes, for example, the aerobic oxidation of thiols to disulfides, a reaction of both biological significance and industrial importance.

The presence of robust C-F bonds, however, renders the catalyst unsuitable for attachment to solid-state supports, except via van der Waals …

Effect Of Surface Omniphobicity On Drying By Forced Convection, Madani A. Khan, Jeffrey Alston, Andrew Guenthner

STAR Program Research Presentations

Low energy surfaces can strongly repel both oil and water. Recently these surfaces have been fabricated on various substrates including fabric, aluminum, stainless steel and many other materials. In this experiment we explore the use of low energy surface deposition on aluminum alloy, stainless steel and silicon substrates, to enhance the drying rate of liquids removed from the surface by forced convection. We control surface roughness by substrate abrasion and by the growth of Al₂O₃ nanograss to enhance liquid repellence by use of a hierarchical texture. Liquid repellence of the substrates is measured by contact angles of …

Synthesis And Flammability Testing Of Epoxy Functionalized Phosphorous-Based Flame Retardants, Vladimir Benin, Xuemei Cui, Alexander Morgan, Karl Seiwert

Chemistry Faculty Publications

Several potential new phosphorus-containing flame retardant molecules were evaluated for heat release reduction potential by incorporation of the molecules into a polyurethane, generated from methylene diphenyl diisocyanate and 1,3-propane diol. The heat release reduction potential of these substances was evaluated 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 to qualitatively evaluate their potential reactivity into the polyurethane prior to heat release testing. The functionality of the flame retardants was epoxide based that would potentially react with the diol during polyurethane synthesis. Flammability testing …

Green Chemistry As A Tool For Understanding The Toxic Substances Control Act: A Lecture Module For Undergraduate Students, Molly R. Blessing

Honors Scholar Theses

The Toxic Substances Control Act (TSCA) is the central form of chemical regulation existent in the United States today, yet scientists are often unaware or uncertain of its provisions. Violations of TSCA by unknowing chemists set industry and government unnecessarily at odds. A lecture on TSCA was developed for undergraduate students that uses the concept of green chemistry to promote interest and incentivize learning. Green chemistry methods are cleaner and less wasteful than traditional chemical ones, and many companies using them are at the forefront of technological innovation. The lecture explains both green chemistry and TSCA, includes company case studies, …

Unraveling Structures Of Protection Ligands On Gold Nanoparticle Au68(Sh)32, Wen Wu Xu, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

New low-energy atomic structures of the thiolate-protected gold nanoparticle Au₆₈(SH)₃₂ are uncovered, where the atomic positions of the Au atoms are taken from the recent single-particle transmission electron microscopy measurement by Kornberg and co-workers, whereas the pattern of thiolate ligands on the gold core is attained on the basis of the generic formulation (or rule) of the “divide and protect” concept. Four distinct low-energy isomers, Iso1 to Iso4, whose structures all satisfy the generic formulation, are predicted. Density-functional theory optimization indicates that the four isomers are all lower in energy by 3 to 4 eV than the …

Novel Dna Electrochemical Biosensor For K-Ras Point Mutation Detection Based On Dna Polymerase I, Li-Qing Lin, Cheng-Fei Zhao, Zhou-Qian Jiang, Shao-Huang Weng, Xiao-Lan Xie, Xin-Hua Lin

Journal of Electrochemistry

In this article, we developed a novel DNA electrochemical sensor for obtaining a current-time curve based on DNA polymerase I. The capture probes were fixed on the Au electrode by Au interacting with -SH, and then hybridized with the K-ras mutant target DNA as far as one base before the mutation site. After hybridizing the K-ras mutant or wild target DNA, the resulting assembly reacted with the dUTP-biotin in the presence of DNA polymerase I. Then avidin-HRP combined the dUTP-biotin on the electrode. The proposed electrode was applied for detection in TMB solution by electrochemical technology. The experimental results showed …

A Novel Nitrite Sensing Electrode Based On Au/Fe3O4/Chitosan Nanocomposite, Ying Dong, Yong Wang, Huan-Huan Xing, Jian-Ying Qu

Journal of Electrochemistry

A novel nitrite sensing electrode based on gold nanoparticles and iron oxides (Fe₃O₄) magnetic nanoparticles was fabricated with chitosan as the protective film on glassy carbon matrix. Experiment results showed that the sensing electrode exhibited good electrocatalytic activity toward oxidation of nitrite, and the oxidation peak current increased linearly with the concentration of nitrite varying from 5.0×10^-6 to 2.0×10^-3 mol·L^-1 (R=0.9996) with a detection limit of 7.1×10^-7 mol·L^-1 (S/N=3). The sensing electrode exhibited good sensitivity, selectivity and repeatability.

Electrochemiluminescence Assay Based On Bipolar Electrode For Bioanalysis, Mei-Sheng Wu, Jing-Juan Xu, Hong-Yuan Chen

Journal of Electrochemistry

Bipolar electrodes (BPEs) are electronic conductors which are usually embedded into microchannels. The potential difference at the BPE/solution interface is obtained by applying a voltage at the two ends of the microchannel. When it reaches a critical value, the redox reaction takes place at both poles of the BPE simultaneously. Compared with other detection methods, the electrochemiluminescence (ECL) platform based on BPE possesses the advantages of concentration enrichment, high sensitivity, low cost, portable sensor system, no need for a light source, which is quite suitable for bioanalysis. This paper reviews the ECL-BPE strategy for bioanalysis and proposes the future research …

Electrochemiluminescence Biosensors Based On The Signal Amplification Of Co-Reactants, Hai-Jun Wang, Li-Juan Xiao, Ying He, Xin-Ya Jiang, Ya-Li Yuan, Ying Zhuo, Ya-Qin Chai, Ruo Yuan

Journal of Electrochemistry

Using co-reactants to enhance the luminous efficiency of luminophores is a common, convenient and effective method in the construction of the electrochemiluminescence (ECL) biosensors. However, the different methods of introducing co-reactants in the construction of the ECL biosensors will bring different amplification effects. In this review, several signal amplification methods through co-reactants are summarized: 1) Adding the co-reactants directly into the detection solution; 2) Immobilizing the co-reactants onto the electrode surface; 3) Using enzymatic reaction to generate co-reactants in situ around the electrode surface. And then, the outlook of the ECL signal amplification strategy is proposed on those bases.

Sensitive Detection Of Hydroxyl Radical Based On Silver-Enhanced Gold Nanoparticle Label, Yan Yang, Peng Yu, Xiao-Hua Zhang, Jin-Hua Chen

Journal of Electrochemistry

A novel DNA-based electrochemical sensor has been successfully constructed for sensitive detection of hydroxyl radical (·OH) based on the silver-enhanced gold nanoparticle label. Thiolated DNA1 was firstly immobilized on the gold electrode through Au—S bonds. The ·OH generated from Fenton reaction could induce serious oxidative damage of the DNA1 layer on the electrode surface. Then DNA2-functionalized gold nanoparticles (DNA2-AuNPs) were linked on the electrode through the hybridization between DNA2 and undamaged DNA1. Based on the catalytic reduction of silver ion by AuNPs, a silver layer was formed on the surface of AuNPs. The quantitative assay of ·OH was carried out …

A Multi-Channel Electrochemical Immunosensing System With Polyhrp-Based Signal Amplification For The Detection Of Tumor Markers, Wang-Ping Deng, Yan-Zhi Dou, Jing Su, Lin Hao, Shi-Ping Song, Chun-Hai Fan

Journal of Electrochemistry

We have developed a multi-channel electrochemical immunosensing system for the detection of α-fetoprotein (AFP). The sensing system consisted of carbon screen-printed electrode (SPCE) arrays and polyHRP-based signal amplification probes. AFP antigens could bind to both capture antibodies immobilized on electrode arrays ant detection antibodies (anti-AFP IgG developed in rabbit). The anti-rabbit IgG conjugated to poly-horseradish peroxidase were used as a signaling probe to bind to the immuno-complex. The current signals were harvested by a home-made multi-channels electrochemical detector. AFP could be detected in the concentration ranges of 64 pg·mL^-1 ~ 250 ng·mL^-1. The detection limit was as …

Fabrication And Application Of Cytochrome P450 Electrochemcial Biosensor In Drug Metabolism, Xuan Xu, Ju-Sheng Lu, Song-Qin Liu

Journal of Electrochemistry

The process of drug metabolism plays an important role in drug efficacy and toxicity in vivo. Thus, the development of cheap, continent, rapid and high-throughput method for drug metabolism studies has great guiding significance for the design of new drugs, the determination of drug dosage and the detection of clinical drugs. Since the key role played by Cytochrome P450 (CYP450) in phase-I drug reaction, the constructed CYP450 enzyme biosensor can be used for the initial screening of drugs. It is found that the replacement of coenzyme NADPH with an electrode is to provide two electrons demanded in the catalytic reaction. …

Electrochemical Detection Of L-Cysteine Based On Iron Phthalocyanine/Nitrogen-Doped Graphene Modified Electrodes, Jing-Jing Xiao, Hui-Ying Xu, Li Xu, Bao-Hong Liu

Journal of Electrochemistry

In this study, we report a facile method to develop FePc/N-G hybrid modified electrode for the detection of L-cysteine. The electrochemical sensor was characterized by cyclic voltammetry and amperometric response. The sensor exhibited a wider linear range with rapid response which has outperformed pure FePc/GCE, highlighting the important role of nitrogen doped graphene as substrate for improving the electrochemical response property.

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. …