Hanming Ding

Preparation and visible light photocatalytic activity of Ag/TiO₂/graphene nanocomposite.

Great efforts have been made to develop efficient visible light-activated photocatalysts in recent years. In this work, a new nanocomposite consisting of anatase TiO(2), Ag, and graphene was prepared for use as a visible light-activated photocatalyst, which exhibited significantly increased visible light absorption and improved photocatalytic activity, compared with Ag/TiO(2) and TiO(2)/graphene nanocomposites. The increased absorption in visible light region is originated from the strong interaction between TiO(2) nanoparticles and graphene, as well as the surface plasmon resonance effect of Ag nanoparticles that are mainly adsorbed on the surface of TiO(2) nanoparticles. The highly efficient photocatalytic activity is associated with the strong adsorption ability of graphene for aromatic dye molecules, fast photogenerated charge separation due to the formation of Schottky junction between TiO(2) and Ag nanoparticles and the high electron mobility of graphene sheets, as well as the broad absorption in the visible light region. This work suggests that the combination of the excellent electrical properties of graphene and the surface plasmon resonance effect of noble metallic nanoparticles provides a versatile strategy for the synthesis of novel and efficient visible light-activated photocatalysts.

Cholesterol biosensors prepared by layer-by-layer technique.

The analysis of formation, deposition and characterization of cholesterol oxidase (COX) layer-by-layer films were performed. Initially, a layer of polyanion, poly(styrene sulfonate) (PSS) was adsorbed followed by a layer of polycation, poly(ethylene imine) (PEI) on each solid substrate from aqueous solutions. The alternating layers were formed by consecutive adsorption of polycations (PEI) and negatively charged proteins (COX) and cholesterol esterase (CE). A strong interaction between protein and polyelectrolyte improves the stability of the alternating multilayer; however, it can change a native protein conformation and impair the protein activity. The PSS/PEI/COX, PSS/PEI/COX/PEI/CE, PSS/PEI/COX-CE/PEI etc. layered structures were prepared on the surface of a platinum electrode, ITO coated glass plate, quartz crystal microbalance, quartz plates, mica and silicon substrates. Optical and gravimetric measurements based on an ultraviolet-visible absorption spectroscopy and a quartz crystal microbalance revealed that the enzyme multilayers thus prepared consist of molecular layered of the proteins. The surface morphology of such bilayer films was investigated by using atomic force microscopy. The electrochemical redox processes of the enzyme-layered films deposited either on platinum or ITO coated glass plate were investigated. The response current of cholesterol oxidase electrode with concentration of cholesterol was investigated at length.

A physical insight into the gas-sensing properties of copper (II) tetra-(tert-butyl)-5,10,15,20-tetraazaporphyrin Langmuir–Blodgett films

Abstract The Langmuir isotherm of copper (II) tetra-( tert -butyl)-5,10,15,20-tetraazaporphyrin [CuPaz( t -Bu) 4 ] has been investigated at the air–water interface. The Langmuir monolayer displays two phase regions, which have a phase transition at 7 mN/m. Langmuir–Blodgett (LB) films have been fabricated onto glass slides, interdigitated electrodes and quartz crystal microbalance electrodes, and characterized by UV-VIS spectroscopy, electrical and nanogravimetric measurements, respectively. The CuPaz( t -Bu) 4 LB films were used to quantity some of the volatile gases, i.e. vapors of hexane, benzene and toluene. UV-VIS spectroscopic measurements reveal that there is an interaction between CuPaz( t -Bu) 4 molecules and the above organic solvent molecules, which is manifested by a red shift and broadening of Soret and Q bands. The response and recovery behaviors, sensitivity and selectivity of the LB films to different organic vapors have been investigated by means of nanogravimetric measurements. Such results offer a potential application of such a porphyrin derivative for the detection of aromatic compounds, even at room temperature.

Construction of organic-inorganic hybrid ultrathin films self-assembled from poly(thiophene-3-acetic acid) and TiO2

Ultrathin films of poly(thiophene-3-acetic acid) (PTAA)/TiO2 nanocomposite were fabricated layer by layer at various solid surfaces by consecutively adsorbing PTAA and TiCl4 (in toluene–ethanol). The fabrication process was carried out by performing the controlled hydrolysis and condensation processes in separate steps. The build-up of such multilayer films was monitored by UV–VIS spectroscopy and quartz crystal microbalance measurements. The ordered multilayers were subsequently characterized by IR spectroscopy, atomic force microscopy, electrochemical, photo-electrochemical and electrical conductivity measurements. The potential application of such nanocomposite films in photovoltaic applications is discussed.

Detection of hydrogen sulfide : the role of fatty acid salt Langmuir-Blodgett films

Abstract Different fatty acid salt (cadmium arachidate, lead arachidate, zinc arachidate etc.) Langmuir–Blodgett (LB) films were deposited onto piezoelectric quartz crystal microbalance (QCM) electrode surfaces. The reaction kinetics of the LB films with hydrogen sulfide (H 2 S) molecules was monitored using nanogravimetric technique. The exposure of H 2 S gas into the LB films showed a fast response that was manifested by a dramatic change in the frequency of QCM at the initial stage. The influences of film deposition method, film thickness, type of metal ion, concentration and pressure of H 2 S gas upon gas sensing properties were investigated. The fast and irreversible reaction of LB films with H 2 S gas suggests that fatty acid salt LB films can be a potential candidate for gas sensing applications.

Fabrication and characterization of composite Langmuir-Schaefer films of poly(ortho-anisidine) conducting polymer and tri-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine

Abstract Langmuir–Schaefer (LS) films of composite poly( ortho -anisidine) (POAS) and tri-(2,4-di- t -amylphenoxy)-(8-quinolinolyl) copper phthalocyanine (CuPc) were fabricated, and characterized by UV–VIS absorption spectroscopy, quartz crystal microbalance (QCM), electrochemical, in situ spectro-electrochemical techniques, respectively. Surface pressure–area isotherm of composite system showed stable Langmuir films at air–water interface. The uniform deposition of composite monolayers were verified by optical absorption, QCM and cyclic voltammetric measurements. The effects of doping on composite LS films were discussed. Cyclic voltammograms of POAS, CuPc and POAS/CuPc composite systems were also compared. The redox switching response time and diffusion coefficient of such composite LS films were estimated by electrochemical surveying. The photoelectrochemical current transient response of composite LS films was measured at length.

An innovative method for oxidative degradation of chitosan with molecular oxygen catalyzed by metal phthalocyanine in neutral ionic liquid.

A novel aqueous solution-ionic liquid biphasic catalytic system was established for the oxidative degradation of chitosan under mild conditions. In this process, the environmentally acceptable and inexpensive molecular oxygen was first used as oxidant, the metal phthalocyanine was immobilized in ionic liquid as catalyst, and the aqueous solution as medium carried the reactants and the products. Under vigorous stirring and heating, the reactants fully contacted the catalysts in the emulsion and chitosan efficiently degraded into water-soluble materials. At the end of the reaction, the catalytic system could be easily separated by simple decantation and could also be reused in subsequent runs without apparent change in activity. These characters are in favor of the elimination of pollution and the reduction of the economic cost in the large-scale production of the water-soluble chitosan derivatives in chemical industry.

Fabrication and photovoltaic properties of fullerene and copper phthalocyanine derivative mixed Langmuir-Schaefer films

Surface pressure-area isotherms of mixed floating film of fullerene (C60) and tri-(2,4-di-t-amylphenoxy)-(8-quinolinolyl) copper phthalocyanine (CuPc) were investigated at different molar compositions at air-water interface. The shapes of these isotherms and estimated areas per molecule are shown dependent on the molar compositions. C60/CuPc mixed multilayers were fabricated onto various solid substrates by using Langmuir-Schaefer (LS) technique, and characterized by UV-VIS spectroscopy, electrochemical and photoelectrochemical measurements respectively. Uniform LS films were formed when the molar composition was less than 1 : 1 (C60: CuPc). UV-VIS spectroscopic measurements showed that there was no distinct interaction between phthalocyanine and C60molecules at ground state either in solution or in solid films. However, electron transfer appears to have occurred between two kinds of molecules under light illumination. Photoelectrochemical study revealed that phthalocyanine and C60mixed system could be a potential candidate for photovoltaic applications.

A novel inorganic–organic hybrid material: hydrothermal synthesis and properties of [V6O12(CH3O)4(phen)4·4H2O] (phen = 1,10-phenanthroline)

An oxo-vanadium cluster [V6O12(CH3O)4(phen)4·4H2O] (phen = 1,10-phenanthroline) was synthesized hydrothermally and characterized by IR, XPS, TG-DTA and single crystal X-ray diffraction analysis. It crystallizes in the triclinic space group P , with cell parameters a = 9.709(1), b = 11.701(1), c = 13.365(2) Å, α = 74.430(2)°, β = 77.073(2)°, γ = 87.982(2)°, V = 1425.0(3) Å3, Z = 2. The crystal is built up as an organic–inorganic hybrid compound with an unusual oxo-vanadium skeleton and water molecules. Water molecules make up a tetramer linking neighboring oxo-vanadium clusters to form one-dimensional chains, and then further build up three-dimensional supramolecular arrays through the π–π stacking interactions of phen.

Graphitic-C3N4 quantum dots decorated {001}-faceted TiO2 nanosheets as a 0D/2D composite with enhanced solar photocatalytic activity

Zero-dimensional (0D)/two-dimensional (2D) heterojunctions have attracted great attention in photocatalysis due to their superior interfacial effects. In this work, 0D g-C3N4 quantum dots (CNQDs) were firstly used to modify {001}-faceted 2D TiO2 nanosheets by a simple solvothermal method. During the controlled growth of TiO2 nanosheets with exposed reactive {001} facets, the CNQDs can be simultaneously assembled on the surface of TiO2 nanosheets in a highly dispersive way. The 0D/2D composite containing only 0.5% of CNQDs shows the optimized solar photocatalytic activity for the degradation of rhodamine B and 4-chlorophenol. More importantly, the 0D/2D composite exhibits a better solar photocatalytic activity than the bulk g-C3N4/TiO2 nanosheets composite. This improvement can be ascribed to the close interfacial contact and strong interaction between the highly dispersed CNQDs and the TiO2 nanosheets, which could lead to efficient separation of the photogenerated electron–hole pairs, provide more catalytic active sites, and enhance the absorption of solar light. The 0D/2D composite also shows good stability for its practical applications.