Chlorophenols are among the priority listed water contaminants due to their estrogenic, mutagenic or carcinogenic health effects. The Ag/ZnO nanocomposites (NCs) were synthesized, characterized and tested for photacatalytic degradation of chlorophenols in water. The synthesis was done using zinc nitrate hexahydrate (ZnNO3. 6H2O) precursor and sodium hydroxide (NaOH). Silver nitrate (AgNO3) was added to ZnO and reduced with sodium brohydride to produce the silver nanoparticles (NPs) within the ZnO structure. The silver content was varied from 1, 3 and 5wt% for optimisation. The nanocomposites were characterised using ultraviolet - visible spectroscopy (UV-Vis), photolumniscence (PL), x-ray diffraction (XRD), and scanning transmission electron microscopy (STEM). The nanocomposites were tested for their photocatalytic properties on 2- chlorophenol (CP), 2- chlorophenol (CP) and 2,4- dichlorophenol (DCP) in water. The UV-Vis results showed that, as the amount of silver was increased a gradual slight red shift was observed. The XRD patterns for Ag/ZnO exhibited peaks that were characteristic of the hexagonal wurzite structure and peaks characteristic for Ag appeared at 38.24o, 44.37o, 64.67o and 77.58o corresponding to (111), (200), (220) and (311) reflection planes. STEM results showed the presence of Ag in ZnO with ZnO appearing as rods shapes. The EDX elemental analysis confirmed the presence of Ag in the Ag/ZnO nanocomposites with no contaminants peaks. On testing the nanocomposites for phohotocatalytic degradation of chlorophenols, addition of Ag to ZnO improved degradation of the chlorophenols compared to the pristine ZnO.

Despite being one of the oldest phenomena known to mankind and its vast use, there still are open questions about the frictional process between two surfaces, especially at the nanometer scale, such as the energy dissipation mechanism, the influence of the crystallographic orientation and the correlation between macroscopic and microscopic scales. In this work, we analyze the interaction between a sharp tip and graphene by friction force microscopy. The graphene surface roughness and adhesion forces with the microscope tip were measured. Neither roughness nor adhesion were observed to influence the friction forces. The scanning velocity dependence of friction was also measured for a different number of layers. The friction forces were observed to increase with the scanning velocity until a critical velocity is achieved by which we have estimated the effective interaction potential between the tip and the graphene surface.

We report on highly sensitive and flexible L-lactate enzymatic sensors. The sensing materials of this biosensor, two-dimensional (2D) zinc oxide nanoflakes (ZnO NFs), are synthesized on flexible gold(Au)-coated polyethylene terephthalate (PET) substrate using one step sonochemical approach for non-invasive lactate monitoring in human perspiration. ZnO NFs show high isoelectric points (IEP) and biocompatibility. Taking advantage of these unique properties, we immobilized Lactate oxidase (LOx) on the synthesized ZnO NFs. PET/Au/ZnO NFs sensors demonstrated detection of lactate in the range of 10 pM-10 µM for the electrode area of 0.5×0.5 cm2. The sensitivity of this linker free lactate sensor was found 2.23μA/M /cm2 and shows 4 times better response than conventional Au electrode with linker.

Chemomechanical coupling is a hallmark of the functional oxides that are used widely for energy conversion and storage applications including solid oxide fuel cells (SOFCs). These oxides rely on the presence of oxygen vacancies to enable important properties including ionic conductivity and gas exchange reactivity. However, such defects can also facilitate chemical expansion, or coupling between material volume and defect content. Such chemomechanical coupling is particularly relevant with the recent interest in thin film SOFCs which have the potential to decrease operating temperatures and enable portable applications. Thin films present a particular challenge for modelling, as experimental results indicate that film defect chemistry can differ significantly from bulk counterparts under the same experimental conditions. In this study, we explore the influence of point defects, including oxygen vacancies and cation dopants, on the elastic properties of a model material, PrxCe1-xO2-δ (PCO), using density functional theory (DFT + U) simulations. Previously, we showed that PCO films exhibit a decrease in Young’s elastic modulus E due to chemical expansion, but that this decrease can be larger than predicted based on bulk defect models. Here, we apply DFT + U to show that the biaxial elastic modulus of PCO decreases with increased oxygen vacancy content in both bulk and membrane forms. We consider the relative influences of oxygen vacancies and cation dopants on this trend, and highlight local structural changes in the presence of such defects. By relating our computational and experimental results, we evaluate the relative importance of increased oxygen vacancy content and finite thickness on the mechanical properties of oxides that are subject to chemical expansion under operando conditions. This work informs the design of μ-SOFCs, emphasizing the need to characterize thin films separately from bulk counterparts and demonstrating how functional defect content can influence development of stress and strain in devices by changing both material volume and elastic properties.

The oxygen ions in the high temperature superionic state of uranium dioxide (UO2) are known to be in an arrested or jammed state, exhibiting characteristic features of jammed kinetics such as low dimensional string-like ion hopping and dynamical heterogeneity (DH). This thermally-jammed state entails a configurational entropic cost. Using atomistic simulations and the 2PT method, we compute the solid-like (vibrational) and hard sphere-like (configurational) contributions to the total entropy across a temperature range of 1500 K to 2800 K that envelop both the onset of superionic conduction (2000 K) and the second order λ-transition (2610 K). To properly account for the thermally jammed state of the ions, we use an equation of state that is appropriate for the metastable fluid branch. Our simulation results are in excellent agreement with the entropy data extracted from specific heat experiments with a mean error of less than 2%.

Organic compounds such as azo dyes have been detected in wastewater due to their use in industries without regulation. Conventional wastewater treatments are not always effective in the removal of these pollutants. Among the innovative materials that deal with this problem, are the polymer-zeolitic composites used as adsorbents. Modified natural zeolites have been proven to be efficient for the removal of yellow 6; on the other hand, biopolymers such as alginate offer their potential use as a polymer matrix for the synthesis of biocomposites. In this study, the adsorbent properties of a ferric zeolite and an alginate-ferric zeolite composite were determined for the removal of yellow 6 dye from aqueous solutions. The X-ray diffraction (XRD) results of both natural and modified zeolites indicated the presence of clinoptilolite. The characteristic bands of these materials were identified through the Fourier Transform Infrared Spectroscopy (FTIR) technique. Moreover, the presence of iron in the ferrous zeolite was verified by elemental analysis (EDS). Adsorption tests showed that the composite has a lower removal capacity than the zeolitic material; however, in the case of water treatment systems, the composite would be easier to handle than the zeolite without supporting it in a polymer matrix.

In 2015 the West Houston Center for Science & Engineering (WHC), Houston Community College, was awarded funding by the National Science Foundation (DMR) to develop a pilot materials science program, Research Experiences and Exploration in Materials Science (REEMS), focused on introducing materials science to aspiring science & engineering community college students. This multifaceted program provides an opportunity for students from a broad array of interests, backgrounds and ages to gain an appreciation for materials science with respect to their academic and career pursuits. Over the approximately four-year duration of the program, REEMS introduces materials science over the academic year through a voluntary seminar series, and, for a select group of students, participation in summer research experiences at collaborating universities. Academic year activities include conferences with the WHC-REEMS transfer advisor, seminars discussing an overview of materials science, the investigation of the roles of materials science in addressing pressing societal issues, and networking with graduate students, university upper division students, materials research faculty and professionals. This paper will provide an overview of the WHC – REEMS program synergies, impacts and partnership dynamics with participating universities: Rice University, the University of Houston, and the McGovern Medical School at the University of Texas Health Science Center-Houston.

Semiconductor-based heterojunctions have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from a high rate of electron−hole recombination and narrow photo-response range. In this paper, we report on the study of heterojunctions made from visible light active, graphitic carbon nitride, g-C3N4), and UV light active, strontium pyroniobate, Sr2Nb2O7. Heterojunctions made from a combination of g-C3N4 and nitrogen-doped Sr2Nb2O7 obtained at different temperatures were also studied to determine the effect of N doping. The photocatalytic performance was evaluated by using photocatalytic hydrogen evolution reaction (HER)from water g under visible light irradiation. It was found that the photocatalytic activities of as prepared heterojunctions are significantly higher than that of individual components under similar conditions. Heterojunction formed from g-C3N4 and N-doped Sr2Nb2O7 at 700°C (CN/SNON-700) showed better performance than heterojunction made from g-C3N4 and Sr2Nb2O7 (CN/SNO). A plausible mechanism for the heterojunction enhanced photocatalytic activity is proposed based on, relative band positions, and photoluminescence data.

Tissue Engineering has been studied to develop tissues as an alternative approach to the organ regeneration. Successful artificial tissue growth in regenerative medicine depends on the precise scaffold fabrication as well as the cell-cell and cell-scaffold interaction. Scaffolds are extracellular matrices that guide cells to grow in 3D to regenerate the tissues. Cell-seeded scaffolds must be implanted to the damaged tissues to do the tissue regeneration. Scaffolds’ mechanical properties and porosities are the two main scaffold fabrication parameters as the scaffolds must be able to hold the pressure due to the surrounding tissues after the implantation process. In this research, scaffolds were fabricated by photolithography and Poly(ethylene glycol) Diacrylate (PEGDA) which is a biocompatible and biodegradable material was used as a fabrication material. In order to compare the compressive properties of PEGDA only with the compressive properties of drug delivered PEGDA, firstly, PEGDA only solutions were prepared. Then, PEGDA was mixed with Meloxicam 15 mg, Hydrochlorothiazide 12.5 mg, Cyclobenzaprine 10 mg and Spironolactone-hctz 25-25 mg respectively and they were placed under the UV light for about 15 minutes to solidify the cylindrical shaped hydrogels. 5 samples from each group were fabricated under the same conditions. Laboratory temperature, photoinitiator concentration and UV light intensity was kept constant during the fabrication process. After the fabrication was completed, Instron 3369 universal mechanical testing machine with the 5 mm/min compression rate was used to do the compression tests to compare the drug effects on PEGDA hydrogels. Our results indicate that average ultimate strength of PEGDA only samples was 3.820 MPa. Also, due to the fact that Meloxicam 15 mg and PEGDA mixture did not solidify under the UV light at all, compression test could not be performed for PEGDA- Meloxicam 15 mg mixture. However, Hydrochlorothiazide 12.5 mg, Cyclobenzaprine 10 mg and Spironolactone-hctz 25-25 mg dissolved within the PEGDA completely and our compression results show that average ultimate strengths were 3.372 MPa, 1.602 MPa, 1.999 MPa respectively. This preliminary research showcases that compressive properties of the PEGDA-based photopolymerized scaffolds can be altered with the control of the drug type and drug concentration.

Photoluminescence (PL) spectroscopy has been used to study the defect levels in thin film copper indium diselenide (CuInSe2, CIS) which we are developing as the absorber layer for the bottom cell of a monolithically grown perovskite/CuInSe2 tandem solar cell. Temperature and laser power dependent PL measurements of thin film CIS for two different Cu/In ratios (0.66 and 0.80) have been performed. The CIS film with Cu/In = 0.80 shows a prominent donor-to-acceptor peak (DAP) involving a shallow acceptor of binding energy ∼22 meV, with phonon replica at ∼32 meV spacing. In contrast, PL measurement of CIS film for Cu/In = 0.66 taken at 20 K exhibited an asymmetric and broad PL spectrum with peaks at 0.845 eV and 0.787 eV. Laser intensity dependent PL revealed that the observed peaks 0.845 eV and 0.787 eV shift towards higher energy (aka j-shift) at ∼11.7 meV/decade and ∼ 8 meV/decade with increase in laser intensity respectively. The asymmetric and broad spectrum together with large j-shift suggests that the observed peaks at 0.845 eV and 0.787 eV were related to band-to-tail (BT) and band-to-impurity (BI) transition, respectively. Such a band-tail-related transition originates from the potential fluctuation of defect states at low temperature. The appearance of band related transition in CIS film with Cu/In = 0.66 is the indicator of the presence of large number of charged defect states.

Graphene quantum dots (GQDs) - zero-dimensional materials - are sheets of a few nanometers in lateral dimension and exhibit quantum confinement and edge site effects where sp2-bonded carbon nanocore surrounded with edged plane functional moieties is promising as advanced electroactive sensing platforms. In this work, GQDs are synthesized by solvothermal and hydrothermal techniques, with optimal size of 5 nm. Their potential in fundamental (direct electron transfer) and applied (enzymatic glucose biosensor) electrochemistry are demonstrated. Glucose oxidase (GOx) immobilized on glassy carbon (GC) electrodes modified with GQDs are investigated by means of cyclic voltammetry, differential pulse voltammetry, and amperometry. Well-defined quasi-reversible redox peaks observed under various electrochemical parameters helped to determine diffusion coefficient (D) and first-order electron transfer rate (kET). The cyclic voltammetry curves showed homogeneous ion transport for GQD with D ranging between 8.45 × 10−9 m2 s−1 and 3 × 10−8 m2 s−1 following GO < rGO < GQD < GQD (with FcMeOH as redox probe) < GOx/rGO < GOx/GO < HRP/GQDs < GOx/GQDs. The developed GOx-GQDs biosensor responds efficiently and linearly to the presence of glucose over concentrations ranging 10 μM and 3 mM with limit of detection 1.35 μM and sensitivity 0.00769 μA μM−1·cm−2 as compared with rGO (0.025 μA μM−1 cm−2, 4.16 μM) and GO (0.064 μA μM−1 cm−2, 4.82 μM) nanosheets. The high performance and stability of GQDs is attributed to sufficiently large surface-to-volume ratio, excellent biocompatibility, abundant hydrophilic edge site density, and partially hydrophobic planar sites that favors GOx adsorption on the electrode surface and versatile architectures to ensure rapid charge transfer and electron/ion conduction (<10 ms). We also carried out similar studies with other enzymatic protein biomolecules on electrode surfaces prepared from GQD precursors for electrochemical comparison, thus opening up potential sensing applications in medicine as well as bio-nanotechnology.

We propose a 3D-printable soft, stretchable, and transparent hydrogel-elastomer device that is able to detect simulated ‘nerve’ signals. The signal is passed to a conductive hydrogel electrode through a non-contact method of capacitive coupling through polydimethylsiloxane (PDMS). We demonstrate that the device is able to detect sinusoidal waveforms passed through a simulated ‘nerve’ made from conductive hydrogel over a range of frequencies (1 kHz – 1 MHz). Analysis of signal detection showed a correlation to the electrode contact area and a Vin/Vout of larger than 10%. This provides the framework for the future development of a soft, 3D-printable, capacitive coupling device that can be used as a cuff electrode for detecting peripheral nerve signals.

Anti-organic fouling performance of titanium dioxide (TiO2) can be enhanced by extending its light absorption and photocatalytic capability from ultra-violet to the visible range through hydrogenation. In this work, we aim at studying the impact of hydrogenation on the performance of both electron beam-deposited TiO2 thin films and hydrothermally grown TiO2 nanostructures on titanium substrates. Hydrogenation of these TiO2-deposited titanium substrates (TiO2/Ti) are achieved in relatively low-temperature low-pressure chemical vapor deposition chamber without any noble diatomic hydrogen dissociation catalyst, such as platinum. Our study shows that these hydrogenated TiO2/Ti have better light absorption ability and the titanium substrate itself serves as the active catalyst for hydrogen dissociation and diffusion. By applying hydrogenation to the TiO2 nanostructures, we can enhance photocatalytic performance by 50% through methylene blue degradation experiments. We have also evaluated the effect of hydrogenation on carrier density and mobility in TiO2/Ti. We recommend the hydrogenation of hydrothermally grown TiO2 nanostructure on titanium substrates for scalable photocatalytic applications.

This article aims to prepare high quality of TiO2 powder and study the effect of annealing temperature. TiO2 particles were synthesized by sol-gel method using titanium tetra chloride (TiCl4) as a precursor. The dried gel was annealed at temperatures of 500oC, 600oC, 700°C and 800 °C each for 4 hours. The as-prepared samples were further characterized using X-Ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray Fluorescence spectrometer (EDX), XRD showed anatase structure after annealing and its diffraction scattering intensity indicated the improvement in the crystal structure quality of TiO2 as the temperature increases. SEM micrographs showed a randomly distributed and non-uniform cluster of TiO2 that has a size increase with annealing temperatures. EDX indicated stoichiometric chemical composition between Ti and O enhanced by annealing.

Plasticity in as-grown gold nanowires deformed in three-point bending configuration was studied by Laue microdiffraction. One-dimensional orientation maps of the Au crystal along the nanowire were generated from which the deformation profile was inferred. The crystal lattice was found to rotate continuously around the Au $[\bar{2}11]$ direction, which is transverse to the wire axis evidencing the storage of geometrically necessary dislocations (GNDs). The analysis of the diffraction peak shape points to the activation of multiple slip systems in contrast to the formation of wedge shaped twins predicted by MD simulations.

Surface texturing of transparent conductive oxides is crucial to improve the fraction of incident light trapped in the absorber layer of thin film silicon based solar cells to improve the device performance. In this work, we fabricate and compare periodic, overlapping, and random surface textures and patterns on aluminium doped zinc oxide (AZO) using direct laser processing. The effects of the used laser wavelength, laser operating frequency, and pulse periodicity on the structural, morphological, and optical response of the AZO films were investigated. By optimizing the laser parameters and the associated process conditions, a drastic increase up to 60% in the transmittance haze over the entire solar was achieved.

Extracellular Matrix (ECM), a natural biomaterials, have recently garnered attention in tissue engineering for their high degree of cell proliferative capacity, biocompatibility, biodegradability, and tenability in the body. Decellularization process offers a unique approach for fabricating ECM-based natural scaffold for tissue engineering application by removing intracellular contents in a tissue that could cause any adverse host responses. The effects of Supercritical carbon dioxide (Sc-CO2) treatment on the histological and biochemical properties of the decellularized extracellular matrix (de-ECM) were evaluated and compared with de-ECM from conventional decellularization process to see if it offers significantly reduced treatment times, complete decellularization, and well preserved extracellular matrix structure. The study has shown that a novel method of using supercritical fluid extraction system indeed removed all unnecessary residues and only leaving ECM. The potential of Sc-CO2 de-ECM progressed as a promising approach in tissue repair and regeneration.

Amorphous LiCoO2-based positive electrode materials are synthesized by a mechanical milling technique. As a lithium oxy-acid, Li2SO4, Li3PO4, Li3BO3, Li2CO3, and LiNO3 are selected and milled with LiCoO2. XRD patterns indicate that reaction between LiCoO2 and these lithium oxy-acids proceeds. Amorphization mainly occurs, and several broad peaks attributable to cubic LiCoO2 are observed in all the samples. These amorphous active materials show mixed conductivities of electron and lithium ion. All-solid-state cells using the prepared amorphous active materials and the Li2.9B0.9S0.1O3.1 glass-ceramic electrolyte are fabricated and their charge-discharge properties are examined. The cells with only the 80LiCoO2·20Li2SO4 (mol%) and the 80LiCoO2·20Li3PO4 active materials function as secondary batteries. This is because higher lithium ionic conductivities are obtained in the 80LiCoO2·20Li2SO4 and 80LiCoO2·20Li3PO4 active materials than in the others. The largest capacity is obtained in the cell with the 80LiCoO2·20Li2SO4 active material because of its good formability and high lithium ionic conductivity. In addition, the cell with the 80LiCoO2·20Li2SO4 positive electrode active material shows the better cycle and rate performance than that with the crystalline LiCoO2. It is noted that the amorphization with lithium oxy-acids is a promising technique for achieving a novel active material with better electrochemical performance.