Effect on the property of the photoinduced carrier transport of CdS as sensitizer for TiO2 nanoparticulate thin films

The TiO2 nanoparticle thin films have been sensitized in situ with CdS nanoparticles. The SPS measurement showed that large surface state density was present on the TiO2 nanoparticles and the surface state can be efficiently decreased by sensitization as well as selecting suitable heat treatment, Both the photocurrent response and the charge recombination kinetics in TiO2 thin films were strongly influenced by trapping/detrapping of surface states. The slow photocurrent response of TiO2 nanoparticulate thin films upon the illumination was attributed to the trap saturation effects, The semiconductor sensitization made the slow photoresponse disappeared and the steady-state photocurrent value increased drastically, which suggested that the sensitization of TiO2 thin films with CdS could get a better charge separation and provide a simple alternative to minimize the effect of surface state on the photocurrent response.

Simultaneous determination of both the calibration constant in an electrochemical quartz crystal microbalance and the active surface area of a polycrystalline gold electrode

A novel method is employed for the simultaneous determination of both the calibration constant of an electrochemical quartz crystal microbalance (EQCM) and the active surface area of a polycrystalline gold electrode. A gold electrode: is immersed into a 1 mM KI/1 M H2SO4 solution and on which forms a neutral monolayer. The adsorbed iodine can then be completely oxidized into IO3-. The active surface area of a gold electrode can be obtained from the net electrolytic charge of the oxidation process, and the calibration constant in the EQCM can be calculated from the corresponding frequency shift. The result shows that this method is simple, convenient and valid. (C) 2000 Elsevier Science S.A. All rights reserved.

A novel method for preparing ordered SnO2/TiO2 alternate nanoparticulate films

A novel method using LB films as precursors to prepare pure inorganic ordered film with periodic structure was developed. Surfactant-stabilized SnO2 nanoparticulate organosols and TiO2 nanoparticulate organosols were prepared and used as spreading solutions. Using LB technique, the good film-forming ability of the surfactant-stabilized SnO2 nanoparticles and TiO2 nanoparticles was confirmed by the determination of the pi -A isotherms. The surfactant-stabilized SnO2 and TiO2 nanoparticulate monolayers were fabricated on the water surface and then were transferred to solid substrates (CaF2, quartz, silicon, and so on) alternately, layer-by-layer. Then the as-deposited alternate LB film was treated at different temperatures. The as-deposited alternate LB film and the treated film were characterized by Fourier transform infrared spectroscopy, UV visible spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that our method was successful. The as-deposited alternate LB film formed a periodic structure with a long spacing of 6.5 nm that was composed of SnO2 nanoparticles, TiO2 nanoparticles, and arachidic acid. The treated film composed of SnO2 nanoparticles and TiO2 nanoparticles formed a pure inorganic periodic structure with an ordered distance of 5.4 nm. (C) 2001 Academic Press.

Preparation and spectra study of TiO2 gel doped with fluorescein

TiO2 gel doped with fluorescein was prepared by a sol-gel method, and the fluorescence of fluorescein and its effect on formation of the: gel were investigated with absorption, fluorescence, IR spectroscopies and TG-DTA analysis. The results indicated that FL incorporated into TiO2 gel had exhibited big changes compared to that in ethanol solution both in the absorption and the emission spectra, and the formation of TiO2 gel was influenced greatly by FL.

Effect of surface state properties of TiO2 nanoparticle film on its photocatalytic activity

TiO2 nanoparticle film catalysts with different thicknesses were prepared by plasma-enhanced chemical vapor deposition(PECVD) method and the surfaces were subsequently treated by TiCl4 or O-2 plasma. Two kinds of TiO2 films with different surface properties were obtained. Their surface microstructures and energy levels of surface states were tested by AFM, XRD, SPS, The photocatalytic activities of the catalysts were determined via photodegradation experiments of phenol. The results demonstrated that photocatalytic activities of samples whose surface was treated by O-2 plasma were greater than those treated by TiCl4 plasma. Moreover, photodegradation ratio of phenol during the first hour catalyzed by 0. 17 mu m thickness TiO2 nanoparticle film was greater than other samples. Especially, the difference of photocatalytic activities of TiO2 nanoparticle films treated by TiCl4 or O-2 plasma was respectively explained by energy band theory.

Structural changes of TiO2 gel using Eu3+ ion as the fluorescence probe

Because of the extremely sensitivity to the local environment of the D-5(0) --> F-7(2) transition of Eu3+ ion, the fluorescence of Eu3+ ions was Studied by introducing Eu3+ ions to TiO2 gel by the sol-gel method, from which the structural changes of TiO2 gel were characterized. The results showed that the intensity of D-5(0) --> F-7(2) transition increased with the increasement of heat treatment temperature, which indicated the evaporation of molecular water and the completeness of the condensation reaction. Because of the quenching of the fluorescence induced by the cluster of Eu3+ ions, the addition of Al3+ ions greatly enhanced the emission intensity of Eu3+ ion.

Fabrication and fluorescence study of sensitizing dye TiO2 films

Fluorescence spectra of the sensitizing dye/TiO2 bilayer films were studied. Charge-transfer complexes were formed in the above bilayer.

Preparation of TiO2 Film through Hydrolysis of Titanium Butoxide and Interaction between Sensitizing Dyes and the Film

A method of preparation of stable, homogeneous and controlled thickness TiO2 film through hydrolysis of Ti(OC4H(9))(4) is introduced in detail. The structure and property of the film have been investigated by means of SEM and FT-IR techniques. The strong quenching effect between sensitizing dyes and TiO2 film is observed in their fluorescence spectra.

STUDIES ON INTERFACIAL PHENOMENA OF POLYCRYSTALLINE HG1-XCDXTE THIN-FILM ELECTRODE POLYSULFIDE REDOX SOLUTION

Electrode capacitance and photocurrent spectra of electrodeposited polycrystalline Hg1-xCdxTe thin films of varying (1-x) were measured in polysulfide redox solution, hence the flatband potentional PHI(fb) and the bandgap E(g) of Hg1-xCdxTe thin films obtained. It was of interest to find out that only the location of conduction band E(c) shifts negatively with increasing (1-x) while the valence band E(v), is almost constant. The experimental open circuit photovoltage V0 is smaller than theoretical value V(max) calculated through flatband potential PHI(fb), therefore there is a possibility of promoting the experimental open circuit photovoltage.

PHOTOELECTROCHEMISTRY OF ELECTRODEPOSITED POLYCRYSTALLINE CUINSE2 THIN-FILMS .1. ELECTRODEPOSITION OF CUINSE2 FILMS

Electrodeposition of CuInSe2 was investigated in acidic solutions containing Cu2+, In3+ and HSeO2+ ions. The electrodeposition condition was optimized with the aim of obtaining uniform thin films on titanium substrate. The mechanism of the electrodeposition process is discussed. Structure analysis of the deposited film shows a typical polycrystalline chalcopyrite structure, good crystallinity and homogeneous dispersion. The photoelectrochemical cells made of these kinds of deposited films in polysulfide redox solution give distinct photoresponse.

ELECTRODEPOSITION OF POLYCRYSTALLINE CD-RICH HG1-XCDXTE AND PHOTOELECTRO-CHEMICAL BEHAVIOR OF HG0.09CD0.91TE THIN-FILM

Electrodeposition process of polycrystalline Cd-rich Hg_(1-z)Cd_xTe (x>0.5) in acidic bath of CdSO_4+HTeO_2~+HgCl_2 was investigated. The simultaneous electrodeposition technique of three kinds of ions at the same potential has been achieved. The XRD, SEM and EDAX analysis of the thin film electrodeposited on titanium substrate showed a typical cubic zinc blende polycrystalline structure and homogeneous dispersion. The photoelectrochemical behavior of (1-x)=0.09 polycrystalline thin film in a polysulfide re...

Adsorption and interaction of H2S/SO2 on TiO2

Adsorption and interaction of H2S/SO2 on titania as well as on alumina for comparison has been studied by temperature programmed desorption (TPD), infrared (IR) spectroscopy and temperature programmed electronic conductivity (TPEC) techniques. It was found that the adsorption of both H2S acid SO2 on TiO2 is much greater than on Al2O3. The electronic conductivity of TiO2 measured by TPEC varies significantly as adsorption and desorption takes place on TiO2, showing a strong interaction between TiO2 and adsorbates. At temperature above 200 degrees C, H2S or SO2 adsorbed on TiO2 can be converted into S, H2O and SO2 or SO3. While on the hydrogen treated TiO2, H2S is decomposed into S and H-2, SO2 into S. The active sites on TiO2 surface cannot be so strongly adsorbed by SO2 that it is much more resistant to the sulfation reaction. Unlike TiO2, Al2O3 only provides surface adsorption sites, which can be readily sulfated. The data obtained support one's understanding why TiO2 exhibits a better catalytic performance than that of Al2O3 as a Claus reaction catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.