Direct formation of gold nanoparticles on substrates using a novel ZnO sacrificial templated-growth hydrothermal approach and their properties in organic memory device

This study describes a novel fabrication technique to grow gold nanoparticles (AuNPs) directly on seeded ZnO sacrificial template/polymethylsilsesquioxanes (PMSSQ)/Si using low-temperature hydrothermal reaction at 80°C for 4 h. The effect of non-annealing and various annealing temperatures, 200°C, 300°C, and 400°C, of the ZnO-seeded template on AuNP size and distribution was systematically studied. Another PMMSQ layer was spin-coated on AuNPs to study the memory properties of organic insulator-embedded AuNPs. Well-distributed and controllable AuNP sizes were successfully grown directly on the substrate, as observed using a field emission scanning electron microscope followed by an elemental analysis study. A phase analysis study confirmed that the ZnO sacrificial template was eliminated during the hydrothermal reaction. The AuNP formation mechanism using this hydrothermal reaction approach was proposed. In this study, the AuNPs were charge-trapped sites and showed excellent memory effects when embedded in PMSSQ. Optimum memory properties of PMMSQ-embedded AuNPs were obtained for AuNPs synthesized on a seeded ZnO template annealed at 300°C, with 54 electrons trapped per AuNP and excellent current–voltage response between an erased and programmed device.     

Iron oxide nanoparticles improved biocompatibility and removal of middle molecule uremic toxin of polysulfone hollow fiber membranes

Middle molecule uremic toxins constitute to a quarter of uremic toxins present in human blood. In a condition where these uremic toxins accumulate in bloodstream due to renal failure, blood purification process using a high performance membrane is required. Here, we develop biocompatible mixed matrix membranes (MMMs) made up of polysulfone (PSf) and iron oxide nanoparticles (Fe₂O₃ NPs) with the focus to remove middle molecule uremic toxin effectively. The MMMs were evaluated in terms of their biocompatibility and separation performance. At higher Fe₂O₃ NPs loading, the MMM displayed a huge reduction of protein adsorption and platelet adhesion while maintaining normal blood coagulation time and acceptable complement activation. The optimized MMM exhibited high permeability (110.47 L m⁻² h⁻¹ bar⁻¹), protein retention (99.9%) and demonstrated excellent clearance of urea (82%) and lysozyme (46.7%). The PSf/Fe₂O₃ MMM is proven to have promising attributes for hemodialysis application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48234.     

Ion-exchange equilibria of Ni, Co, Mn and Mg with iminodiacetic acid chelating resin Amberlite IRC 748

A chelating ion-exchange resin, Amberlite IRC 748 which carries an iminodiacetate acid functional group has been investigated for its adsorption properties towards Ni, Co, Mn and Mg from aqueous solution. Experiments were conducted through batch adsorption by varying the resin volume at three different pH values. It was observed that the amount of metals adsorbed by the resin increased with increasing pH. The applicability of both the Langmuir and Freundlich isotherms were analyzed on the equilibrium data obtained. In all cases, the Langmuir isotherm shows an excellent fit to the experimental data while the Freundlich isotherm failed to predict the data at higher loadings. The resin exhibited high selectivity towards nickel (K = 58,000) and cobalt (K = 16,800), which can be easily separated from magnesium and manganese at pH 4 and 5. The obtained values of the equilibrium constant K (l/mol) matched the expected order of selectivity of this resin which is Ni > Co > Mn > Mg. The results also showed that the adsorption mechanisms of these metals onto the resin follow a combination of monolayer and multilayer adsorption.     

Effect of γ-irradiation on the physical and mechanical properties of chitosan powder

In this study, locally produced chitosan powder was irradiated with pre-determined doses of γ-ray (Co-60) of 10 kGy, 25 kGy, 50 kGy and 100 kGy respectively. The properties of both chitosan powder and the chitosan film were examined and compared with unradiated chitosan. Physical characteristic of the irradiated powder and film was studied using stereo microscope. It was observed that the γ-ray induces a noticeable colour tone intensity change to the chitosan. Further investigation using Fourier Transformed Infrared Spectroscopy (FT-IR) analysis has confirmed that the chain scission reaction was occurred as a result of γ-ray exposure through the depolymerization mechanisms. Interestingly, the degree of deacetylation (DD) of chitosan measured using FT-IR showed a negligible effect due to the exposure of γ-ray radiation. Further investigation on the viscosity average molecular weight (M_v) showed a reduction of M_v from 577 kD of pure chitosan to 458 kD, 242 kD, 159 kD and 106 kD for 10 kGy, 25 kGy, 50 kGy and 100 kGy of γ-radiated chitosan respectively. In addition, the tensile strength and elongation at break showed a similar decreasing trend with increasing dosage of γ-ray.     

Enhanced hydrophilic polysulfone hollow fiber membranes with addition of iron oxide nanoparticles

Membranes are at the heart of hemodialysis treatment functions to remove excess metabolic waste such as urea. However, membranes made up of pure polymers and hydrophilic polymers such as polyvinylpyrrolidone suffer problems of low flux and bio‐incompatibility. Hence, this study aimed to improve polysulfone (PSf ) membrane surface properties by the addition of iron oxide nanoparticles (IONPs ). The membrane surface properties and separation performance of neat PSf membrane and membrane filled with IONPs at a loading of 0.2 wt% were investigated and compared. The membranes were characterized in terms of morphology, pure water permeability (PWP ) and protein rejection using bovine serum albumin (BSA ). A decrease in contact angle value from 66.62° to 46.23° for the PSf /IONPs membrane indicated an increase in surface hydrophilicity that caused positive effects on the PWP and BSA rejection of the membrane. The PWP increased by 40.74% to 57.04 L m^?2 h^?1 bar^?1 when IONPs were incorporated due to the improved interaction with water molecules. Furthermore, the PSf /IONPs membrane rejected 96.43% of BSA as compared to only 91.14% by the neat PSf membrane. Hence, the incorporation of IONPs enhanced the PSf hollow fiber membrane hydrophilicity and consequently improved the separation performance of the membrane for hemodialysis application. © 2017 Society of Chemical Industry     

Anaerobic Digestion Process of Food Waste for Biogas Production: A Simulation Approach

Anaerobic digestion (AD) involves a series of biological processes in which organic material is broken down and transformed into biogas. A simulation model of the AD process in treating food waste to produce biogas was developed using Aspen Plus software. The components list, thermodynamic property package, reaction list, reactor model, and process condition were specified in Aspen Plus. Sensitivity analysis was performed to study the effect of hydraulic retention time and changes in food waste composition on the biogas production. The methane composition in biogas decreased when the hydraulic retention time was increased which is due to the reduction of substrate consumption during the AD process. The process model is able to represent the AD process and provides a good approximation on the production of biogas under various process operating conditions.