Dayong Gui

Activity and thermal stability improvements of glucose oxidase upon adsorption on core-shell PMMA-BSA nanoparticles.

The interaction and adsorption of enzyme, glucose oxidase (GOx), on poly(methyl methacrylate)-bovine serum albumin (PMMA-BSA) particles were studied by using a quartz crystal microbalance with dissipation (QCM-D) and laser light scattering (LLS). The enzyme was irreversibly immobilized on the PMMA-BSA particle surface. The amount of enzyme immobilized on PMMA-BSA particles and the enzymatic activity were determined by UV/vis measurements. The influences of pH and ionic strength on the adsorption indicate that the electrostatic interaction plays a major role on the immobilization. The adsorbed GOx can retain at least 80% of the free enzyme activity. Thermal stability studies reveal that the adsorbed GOx only losses 28% of its activity in comparison with a 64% activity loss of free GOx when it is incubated at 50 degrees C for 35 h.

Liquid crystal functionalization of graphene nanoplatelets for improved thermal and mechanical properties of silicone resin composites

A liquid crystalline molecule, polyurethane-imide (PUI), was used to functionalize graphene nanoplatelets (GNS) via covalent bond and π–π interactions. The PUI functionalized graphene nanoplatelets (PUI–GNS) were characterized by fluorescence spectroscopy, thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy, and then mixed with silicone resin as fillers to fabricate silicon resin nanocomposites. The drastic quenching of the PUI fluorescence elucidated that the biphenyl anchoring unit of liquid crystalline PUI was strongly interacted with the surface of graphene sheets via π–π interactions. FTIR and Raman spectroscopy proved the existence of a covalent interaction between the PUI and GNS. The mechanical properties testing indicated that the tensile strength of silicon resin nanocomposites increased by 521% over that of a neat silicon resin when the mass fraction of PUI–GNS was 1.0%, and the elastic modulus of the silicon resin nanocomposite increased by 902% over that of the neat silicon resin if it came up to 2.0%. The thermal conductivity of the resin filled with the PUI–GNS was improved to be 1.3822 W (m K)−1 at a mass fraction of 10.0%, which was enhanced more than 16.5 times over that of the neat silicon resin. The resulting thermally conductive and mechanically applicable silicon resin nanocomposites could be significant in a wide variety of electronic packaging applications.

First principle simulation on oxidation mechanism of diethyl ether by nitrogen dioxide

The oxidation mechanism of diethyl ethers by NO2 was carried out using density functional theory (DFT) at the B3LYP/6-31+G (d, p) level. The oxidation process of ether follows four steps. First, the diethyl ether reacts with NO2 to produce HNO2 and diethyl ether radical with an energy barrier of 20.62 kcal ⋅ mol-1. Then, the diethyl ether radical formed in the first step directly combines with NO2 to form CH3CH(ONO)OCH2CH3. In the third step, the CH3CH(ONO)OCH2CH3 was further decomposed into the CH3CH2ONO and CH3CHO with a moderately high energy barrier of 32.87 kcal ⋅ mol-1. Finally, the CH3CH2ONO continues to react with NO2 to yield CH3CHO, HNO2 and NO with an energy barrier of 28.13 kcal ⋅ mol-1. The calculated oxidation mechanism agrees well with Nishiguchi and Okamotos experiment and proposal.

Study on the surface modification of silica particle and its filled epoxy resin

Silica particle-filled epoxy resin is widely used in electronic packaging. In this research, the isocyanate-terminated polydimethylsiloxane (ITPDMS) was synthesized by terminal-hydroxyl polydimethylsiloxane (HTPDMS) and 2, 4-toluene diisocyanate (TDI) firstly. Then the ITPDMS was used for the surface graft modification of micro-level silica. The ITPDMS modified silica (P-SiO2) was filled into epoxy resin for enhancing the interfacial bonding between silica and ER matrix. For comparison, the modification of silica particle with other compounds such as silane coupling agent (KH-560) and 2, 4-toluene diisocyanate and their performances of particle-filled epoxy resins were also investigated. The various modified and unmodified SiO2 were characterized by FTIR and TG. The mechanical properties of silica filled ER were measured by universal testing machine and Dynamic mechanical analysis (DMA). The morphology of silica particle filled epoxy resin was also evaluated by scanning electron microscopy (SEM) investigation of fracture surface. The results show that SiO2 can be grafted with ITPDMS, TDI, and KH-560 effectively and the tensile strength and bending strength of the series modified SiO2 filled ER systems are improved obviously. Especially, the tensile strength and bending strength of P-SiO2 filled ER systems increase by 11.68% and 11.55% than those of the original SiO2 filled ER respectively. The glass transition temperature of P-SiO2-filled ER system was also increased, compared with those of the original SiO2-filled ER.

Preparation and thermo-mechanical properties of functionalized graphene/silicone rubber nanocomposites

Silicone rubber is widely used in electronic packaging materials. Electronic appliances have become miniaturized which need more outstanding packaging materials. Functionalized grapheme/scilicon rubber composites is one of the development to improve the performance of the silicone rubber. Graphite oxide (GO) was modified by KH-550, and then the modified graphite oxide was reduced by hydrazine hydrate to get functionalized graphene (FG). In order to get functionalized graphene /silicon rubber nanocomposites, FG was dispersed into 107 gum. The structure and morphology of both the nanocomposites and FG were characterized by FTIR, SEM, XRD and TG. The results show that KH-550 was bonded with GO, the layer of FG was expanded to 0.4nm. Compared with the pure silicon rubber, the initial decomposition temperature of all the functionalized graphene/silicon rubber nanocomposites were improved. Mechanical property tests show that the tensile strength of the nanocomposites with 0.7wt% FG are 2.46 MPa which increases by 198.39% compared with neat silicone rubber, and the elongation at break of composite increases by 171.89%, which is about triple of the pure silicone rubber. Thermal conductivity test shows that the thermal conductivity of the composites with 1.0wt% FG reaches 0.18 W /(m·K).

Preparation of graphene aerogel and its electrochemical properties as the electrode materials for supercapacitors

Graphene oxide was prepared through an improved method, and then three-dimensional graphene aerogel was (GA) synthesized by an organic sol-gel process. The morphological characteristics and textural properties of the GA were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR), respectively. For capacitive properties tests, cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) were carried out in a two-electrode system with a working potential window from 0 to 1V. Moreover, a specific capacitance of 176 F/g was determined at a constant current density of 1 A/g in 1 mol L-1 Na2SO4 electrolyte. The advantageous properties such as high specific surface areas, high specific capacitance, high conductivity and well-connected 3D mesoporous structure of the GA, permit excellent performance as electrode materials for supercapacitors.

Fast single mode microwave-assisted synthesis of porous carbon aerogel for supercapacitors

Carbon materials are, in general, very good absorbents of microwaves. The microwave-assisted synthesis illustrated in this work allows carbon aerogels (CA) to be synthesized in a much shorter time than by conventional methods. Resorcinol-formaldehyde xerogels were synthesized using single mode microwave synthesis system at 85°C for less than an hour. Then, carbonization was performed to obtain carbon xerogels. The effect of the microwave radiation time involved in the process on the textural and electrochemical performance of the final materials was evaluated. It can be concluded that it is possible to control their textural characteristics of carbon xerogels by modifying radiation time. The electrochemical performance of synthesized carbon xerogels as electrode materials in electric double-layer capacitors was studied by cyclic voltammetry and charge/discharge experiments in an alkali medium (6MKOH). It can be seen that single mode microwave-assisted synthesis helps the carbon xerogels display good cycle durability and the specific capacitance of the CA which was radiation for 40minutes is 96.22F/g even without any activation and doping treatments.

Preparation of graphene/nano-MnO 2 composite and its electrochemical performance as supercapacitor electrodes

The graphene/nano-MnO2 composite was synthesized by a chemical co-precipitation method. The crystal structure and the surface topography of all materials were characterized by means of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectrum and scanning electron microscopy(SEM). The results of XRD pattern and FTIR spectrum reveal that a high quality graphene has been synthetized successfully. The SEM images show that nano-MnO2 has a honeycomb structure formed by nanoplatelets and nano-MnO2 spheres are dispersed on the surface of graphene layer in graphene/nano-MnO2 composite. The electrochemical properties of the composite were evaluated by cyclic voltammetry and galvanostatic charge/ discharge respectively. The graphene/nano-MnO2 hybrid material was used for investigation of electrochemical capacitive behaviors. The results of cyclic voltammetry test show that the composite have good eletrochemical performance and the average capacitance is as high as 159F/g in the 6 M KOH aqueous electrolyte.

Carbon aerogel /polyaniline composite as supercapacitors packaging applications

Carbon aerogel (CA) /polyaniline (PANI) composite electrode materials was prepared by chemical oxidation polymerization through doped carbon aerogel with polyaniline. Themorphology and surface area of the composite have been investigated by scanning electron microscope and Brunaner-Emmett-Teller measurement, respectively. Electrochemical properties of the CA/PANI composite have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L-1KOH electrolyte. The results show that the CA/PANI composite is more uniformly distributed than CA and, moreover, CA/PANI composite has better electrochemical performance and high charge/discharge properties than CA. The results based on discharge current show that the composite material has a high specfiic capacitance of 126.15 F g-1, while the capacitance of CA electrode is 103.75 F g-1. The specific capacitance of CA/PANI was higher than CA after 100 cycles at a current of 10mA.

Isocyanate-terminated polydimethylsiloxane-modified epoxy resin: Preparation and curing, characterization and mechanical properties

Isocyanate-terminated polydimethylsiloxane (ITPDMS) was synthesized by the reaction of Hydroxyl-terminated polydimethylsiloxane (HTPDMS) with Toluene diisocyanate (TDI) and was used to modify epoxy resin (Diglycidyl ether of bisphenol A epoxy resin (DGEBA)). The chemical structure of ITPDMS and ITPDMS/ER was characterized by FTIR. The morphology of fracture surfaces of the ITPDMS/ER cured samples were studied by SEM and the thermal analysis was carried out via TGA. The modified epoxy resin shows biphasic toughness fracture morphology and 5∼6 °C improvement in thermal stability over unmodified epoxy resin with brittle fracture morphology. The mechanical properties were investigated by universal testing machine and DMA. The results show that the modified epoxy resin has better mechanical properties with tensile strength, bending strength and elongation increased by 6.76%, 5.05% and 11.84% respectively than unmodified epoxy resin.