Materials Chemistry Commons^™

Syntheses And Characterization Of [4]Ferrocenophane, Ahmed Sabah Al-Doori

Theses, Dissertations and Capstones

Metallocenophanes are metallocenes in which the cyclopentadienyl ligands are connected by a molecular bridge. Recently, metallocenophanes have received increasing attention because of their structure, chemical reactivity, and potential use as building blocks for new materials. Even though metallocenophanes have been synthesized by different methods, the majority of these methods involved the use of iron with rare examples of other metals. Therefore, a new method was employed that in addition to making ferrocenophane, will allow us to synthesize metallocenophanes with V, Cr, Mn, Co, and Ni as central metals. This thesis reports the synthesis of [4]ferrocenophane via a “flytrap” route. The …

Electrochemical Oxidation To Construct A Nickel Sulfide/Oxide Heterostructure With Improvement Of Capacitance, Xuan Liu, Bo You, Xin-Yao Yu, Jeffrey Chipman, Yujie Sun

Chemistry and Biochemistry Faculty Publications

Supercapacitors have been widely recognized as a promising device for the storage of renewable energy. Herein, a facile electrochemical oxidation strategy is described to construct a nickel sulfide/oxide heterostructure which enhances the specific areal capacitance of Ni₃S₂ electrode (2035 mF cm^-2 vs. 31 mF cm^-2 at a current density of 8 mA cm^-2), while still maintaining great stability, showing no performance degradation after 5000 charge-discharge cycles. Its exceptional capacitance, advanced rate capability, and superior cycling stability are attributed to the transformed composition and unique nanostructure achieved during electrochemical oxidation, which can provide a …

Unraveling A Generic Growth Pattern In Structure Evolution Of Thiolate-Protected Gold Nanoclusters, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Precise control of the growth of thiolate-protected gold nanoclusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolateprotected nanoclusters with a unique growth pattern, i.e., Au₂₀(SR)₁₆, Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈, and Au₅₂(SR)₃₂. These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au₈(SR)₄]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au4 …

Tuning The Electronic Properties Of Monolayer And Bilayer Ptse2 Via Strain Engineering, Pengfei Li, Lei Li, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The recently synthesized monolayer PtSe₂ belongs to the class of two-dimensional transition metal dichalcogenide (TMDC) materials (Nano Lett., 2015, 15, 4013). Based on first-principles calculations, we show that the band gaps of monolayer and bilayer PtSe₂ can be tuned over a wide range via strain engineering. Both isotropic and uniaxial strains are investigated. For bilayer PtSe₂, the vertical out-of-plane strain is also considered. In most cases, the strain can reduce the band gap except for the bilayer PtSe₂ under the isotropic strain (Ɛ≤ 4%) for which the band gap can be slightly enlarged. Importantly, the …

Unraveling A Generic Growth Pattern In Structure Evolution Of Thiolate-Protected Gold Nanoclusters, Wen Wu Xu, Yadong Li, Yi Gao, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Precise control of the growth of thiolate-protected gold nanoclusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolateprotected nanoclusters with a unique growth pattern, i.e., Au₂₀(SR)₁₆, Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈, and Au₅₂(SR)₃₂. These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au₈(SR)₄]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au …

Mechanistic Study Of Pressure And Temperature Dependent Structural Changes In Reactive Formation Of Silicon Carbonate, Bingyan Qu, Dongdong Li, Lei Wang, Jili Wu, Rulong Zhou, Bo Zhang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

The discovery of the silicon carbonate through chemical reaction between porous SiO₂ and gaseous CO₂ addressed a long-standing question regarding whether the reaction between CO₂ and SiO₂ is possible. However, the detailed atomic structure of silicon carbonate and associated reaction mechanism are still largely unknown. We explore structure changes of silicon carbonate with pressure and temperature based on systematic ab initio molecular dynamics simulations. Our simulations suggest that the reaction proceeds at the surface of the porous SiO₂. Increasing number of CO₂ molecules can take part in the reaction by increasing either the …

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, Rui Liu

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.

The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves

Theses and Dissertations

Ge_1-xSn_x alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge_1-xSn_x thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in …

Mechanistic Studies Of The Structure-Photostability Relationship Of Organic Conjugated Polymers, Logan Paul Sanow

Electronic Theses and Dissertations

Organic Conjugated polymers (CPs) are a subject of intense research for their application in organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), solid-state dye lasing, biological imaging and sensing, chemical sensing and remote sensing. CPs are key materials in the quest for more sustainable forms of renewable energy, making electronics more versatile and light weight, and increasing the functionality of everyday materials. For these applications and others that use CPs as the photoactive material, one of their main drawbacks is their susceptibility to photodegradation. Photodegradation occurs when the material is exposed to light leading to irreversible changes in the materials, …

Physical And Electrochemical Area Determination Of Electrodeposited Ni, Co, And Nico Thin Films, Matthew Gira, Kevin Tkacz, Jennifer R. Hampton

Faculty Publications

The surface area of electrodeposited thin films of Ni, Co, and NiCo was evaluated using electrochemical double-layer capacitance, electrochemical area measurements using the [Ru(NH₃)₆]³⁺/[Ru(NH₃)₆]²⁺ redox couple, and topographic atomic force microscopy (AFM) imaging. These three methods were compared to each other for each composition separately and for the entire set of samples regardless of composition. Double-layer capacitance measurements were found to be positively correlated to the roughness factors determined by AFM topography. Electrochemical area measurements were found to be less correlated with measured roughness factors as well as applicable …

Hydrogen Bonding And Orientation Effects On The Accommodation Of Methylamine At The Air-Water Interface, Ross D. Hoehn, Marcelo A. Carignano, Sabre Kais, Chongjing Zhu, Xiao Cheng Zeng, Joseph S. Francisco, Ivan Gladich

Xiao Cheng Zeng Publications

Methylamine is an abundant amine compound detected in the atmosphere which can affect the nature of atmospheric aerosol surfaces, changing their chemical and optical properties. Molecular dynamics simulation results show that methylamine accommodation on water is close to unity with the hydrophilic head group solvated in the interfacial environment and the methyl group pointing into the air phase. A detailed analysis of the hydrogen bond network indicates stronger hydrogen bonds between water and the primary amine group at the interface, suggesting that atmospheric trace gases will likely react with the methyl group instead of the solvated amine site. These findings …

Effect Of Synthesis On Quality, Electronic Properties And Environmental Stability Of Individual Monolayer Ti3C2 Mxene Flakes, Alexey Lipatov, Mohamed H. Alhabeb, Maria R. Lukatskaya, Alex J. Boson, Yury Gogotsi, Alexander Sinitskii

Department of Chemistry: Faculty Publications

2D transition metal carbide Ti₃C₂T_x (T stands for surface termination), the most widely studied MXene, has shown outstanding electrochemical properties and promise for a number of bulk applications. However, electronic properties of individual MXene flakes, which are important for understanding the potential of these materials, remain largely unexplored. Herein, a modified synthetic method is reported for producing high-quality monolayer Ti₃C₂T_x flakes. Field-effect transistors (FETs) based on monolayer Ti₃C₂T_x flakes are fabricated and their electronic properties are measured. Individual Ti₃C₂T_x flakes …

Enabling Method To Design Versatile Biomaterial Systems From Colloidal Building Blocks, Shalini Saxena, L. Andrew Lyon

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Development of materials with fine spatial control over topographical, mechanical, or chemical features has been investigated for a variety of applications. Here we present a method to fabricate an array of polyelectrolyte constructs including two-dimensionally and three-dimensionally patterned assemblies using both compressible and incompressible colloidal building blocks. This method eliminates prior constraints associated with specific chemistries, and can be used to develop modular, multi-component, patterned assemblies. In particular, development of constructs were investigated using microgels, which are colloidally stable hydrogel microparticles, polystyrene (PS) beads, and PS-microgel core-shell building blocks in conjunction with the polycation poly(ethyleneimine) (PEI). The topography, mechanical properties, …

Analysis Of An Adhesion Promoter For Rubber To Metal Bonding, Killian Barton

Doctoral

The intermolecular and intramolecular changes induced by thermal stress in an industrial rubber to metal coupling agent (the ‘green molecule’ or GM) are the subject of this thesis. The GM was analysed in-situ in a model application environment using vibrational spectroscopy. NMR spectroscopy was used in order to analyse the solution chemistry of the compound and how this changed as a result of thermal stress. The interaction of the GM and the substrate was analysed using a range of surface analysis techniques including XPS, AFMIR and EDX. An example of a complex substrate, the zinc phosphate conversion coating, was analysed …

Characterization Of Biochars Produced From Peanut Hulls And Pine Wood With Different Pyrolysis Conditions, James W. Lee, Bob Hawkins, Michelle K. Kidder, Barbara R. Evans, A. C. Buchanan, Danny Day

Chemistry & Biochemistry Faculty Publications

Background

Application of modern biomass pyrolysis methods for production of biofuels and biochar is potentially a significant approach to enable global carbon capture and sequestration. To realize this potential, it is essential to develop methods that produce biochar with the characteristics needed for effective soil amendment.

Methods

Biochar materials were produced from peanut hulls and pine wood with different pyrolysis conditions, then characterized by cation exchange (CEC) capacity assays, nitrogen adsorption–desorption isotherm measurements, micro/nanostructural imaging, infrared spectra and elemental analyses.

Results

Under a standard assay condition of pH 8.5, the CEC values of the peanut hull-derived biochar materials, ranging from …

Non-Conventional Approaches To Syntheses Of Ferromagnetic Nanomaterials, Dustin M. Clifford

Theses and Dissertations

The work of this dissertation is centered on two non-conventional synthetic approaches to ferromagnetic nanomaterials: high-throughput experimentation (HTE) (polyol process) and continuous flow (CF) synthesis (aqueous reduction and the polyol process). HTE was performed to investigate phase control between Fe_xCo_1-x and Co_3-xFe_xO_y. Exploration of synthesis limitations based on magnetic properties was achieved by reproducing M_s=210 emu/g. Morphological control of Fe_xCo_1-x alloy was achieved by formation of linear chains using an H_ext. The final study of the Fe_xCo_1-x chains used DoE to …

Sol-Gel Assembly Of Metal Nanostructures Into Metallic Gel Frameworks And Their Applications, Xiaonan Gao

Theses and Dissertations

The advent of nanoscience and nanotechnology has sparked many research forefronts in the creation of materials with control over size, shape, composition, and surface properties.^1,2 However, for most of the applications, nanoscale materials need to be assembled into functional nanostructures that exhibit useful and controllable physical properties. Therefore, numerous efforts on the assembly of nanoparticles (NPs) using organic ligands, polymers and polyelectrolytes have been reported.^3,4 However, the interactions between NPs are mediated by intervening ligands, which are detrimental to charge transport and limit the thermal stability. Hence, developing a new method to produce solid …

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. …

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

Xiao Cheng Zeng Publications

The authors regret that in the original article the spelling of one author’s surname is incorrect. The correct name of the author is ‘Shuang Chen’.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

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 …

Optimisation Of Anodic Oxidation Of Aluminium For Enhanced Adhesion And Corrosion Properties Of Sol-Gel Coatings., Michael Whelan, Tobin Edmond, John Cassidy, John Colreavy, Brendan Duffy

Articles

The anodising process for clad and bare AA2024-T3 has been optimised as a surface preparation technique prior to sol-gel coating deposition. The combination of anodised aluminium surfaces and organically functionalised sol-gel chemistry have been investigated to impart elevated corrosion resistance and increased mechanical properties to the aluminium metal. A duplex anodising process has been developed to utilise the natural corrosion resistance properties of sulphuric acid anodising with the adhesion and hosting properties of phosphoric acid anodising. The novel anodising process and sol-gel sealed surfaces have been characterised using field emission scanning electron microscopy, energy dispersive x-ray spectroscopy. Performance of the …

Fabricating Superhydrophobic And Superoleophobic Surfaces With Multiscale Roughness Using Airbrush And Electrospray, Karam N. Almilaji

Theses and Dissertations

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag …

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 …