Chunwei Yuan

A simple method to prepare N-doped titania hollow spheres with high photocatalytic activity under visible light

N-doped titania hollow spheres were prepared using hydrothermally prepared carbon spheres as template. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The photocatalytic activity of as-prepared hollow titania spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to commercial P25 titania. It was revealed that the photocatalytic activity of the titania hollow spheres enhanced a lot. The apparent rate constant of the titania hollow spheres was almost 17 times as that of P25 titania.

Effects of templates on the structure, stability and photocatalytic activity of mesostructured TiO2

Using long-chain alkylphosphate and alkylamine surfactants as templates, two kinds of purely mesoporous TiO2 molecular sieves (Ti-TMS) were prepared by hydrolysis of titanium isopropoxide under completely different conditions. The templates can be successfully removed by refluxing the samples in an EtOH/H2O/HNO3 solution. Properties of the samples were characterized by means of SEM, FT-IR, DR-UV, TEM, XRD and TG–DTA techniques. XRD patterns and TEM images confirm that the uniformity and stability of Ti-TMS1 synthesized with dodecylphosphate, hexadecylphosphate, or octadecylphosphate as templates is superior to that of Ti-TMS2 prepared with dodecylamine. Furthermore, after the removal of the templates, the stability and the structure of the mesoporous Ti-TMS1 are better than that of Ti-TMS2. Effects of other factors on the structure and stability of Ti-TMS are discussed. The photocatalytic activities of Ti-TMS were also investigated by using polychlorophenol (TCP) and reactive red dye (X-3B) solutions as model pollutants. It was found that the amount of the templates greatly affects the photoactivity of these kind of mesoporous materials.

Construction of a Glucose Biosensor Immobilized With Glucose Oxidase in the Film of Polypyrrole Nanotubules

By electrochemical adsorption of glucose oxidase (GO) on a polypyrrole (PPy) nanotubular layer, a glucose biosensor has been fabricated. PPy microtubules can be synthesized by oxidative polymerization of the pyrrole monomer within the pores of a polycarbonate template. The activities of immobilized GO are investigated and the electrochemical properties are characterized by comparison of the GO electrode constructed by electropolymerization and doping.

Magnetically separable composite photocatalyst with enhanced photocatalytic activity.

A novel magnetically separable composite photocatalyst, anatase titania-coated magnetic activated carbon (TMAC), was prepared in this article. In the synthesis, magnetic activated carbon (MAC) was firstly obtained by adsorbing magnetic Fe3O4 nanoparticles onto the activated carbon (AC), and then the obtained MAC was directly coated by anatase titania nanoparticles prepared at low temperature (i.e. 75 degrees C). The prepared samples were characterized by XRD, SEM and vibrating sample magnetometer (VSM). The composite photocatalyst can be easily separated from solution by a magnet, its photocatalytic activity in degradation of phenol in aqueous solution also has dramatic enhancement compared to that of the neat titania.

Photochemical disinfection of Escherichia coli with a TiO2 colloid solution and a self-assembled TiO2 thin film

Abstract Effect of long-wavelength irradiated TiO2 colloid solutions on E. coli disinfection and the kinetics mechanism have been investigated. In addition, uniform thin films of TiO2 are deposited on an ordinary glass by self-assembled techniques. The modified glass also shows the photokilling effect on bacteria in the air.

Study on photocatalytic performance and degradation kinetics of X-3B with lanthanide-modified titanium dioxide under solar and UV illumination

The present work was focused on photocatalytic oxidation of the model molecule reactive brilliant X-3B by lanthanide-modified TiO(2) samples under artificial solar and UV irradiation. Experimental results showed that the TiO(2) samples doping with lanthanide (Ce and Gd) could greatly enhance the activity of pure TiO(2), and could extend the absorption range to visible region. The optimum doping amount was 0.2 and 0.5at.% for Ce- and Gd-doped TiO(2) particles, respectively. The degradation kinetics of X-3B on Ce-doped TiO(2), Gd-doped TiO(2), and pure TiO(2) were studied as well. The results exhibited that the degradation of X-3B on all the samples were in accordance with the first-order model. The trend of apparent reaction rate constants k(app) was as follows, Gd-doped TiO(2)>Ce-doped TiO(2)>pure TiO(2), under solar illumination. Scatchard plot analysis was used to evaluate the adsorption phenomena of as-prepared samples, and it indicated that lanthanide doping can improve the efficiency of interfacial adsorption of TiO(2) samples. The trend was the same as that of photocatalytic activity.

Preparation and characterization of mesostructured titanium dioxide and its application as a photocatalyst for the wastewater treatment

Abstract Mesostructured Titanium Dioxide (Ti-TMS1, Ti-TMS2) was firstly synthesized with different length chain alkylphosphate and alkylamine surfactants as templates. The templates can be successfully removed by reflux in the EtOH/H2O/KOH solution instead of calcination. The powder X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images confirm that these materials are the hexagonal array of Ti-TMS with different pore sized from about 27 to 44 A. The length of the hydrocarbon tail of alkylphosphate can be used to vary the pore size of Ti-TMS. Moreover, increasing the length of the hydrocarbon tail of alkylphosphate will lead to improve the structure and uniformity of TMS. The uniformity and stability of Ti-TMS2 synthesized with dodecylamine as template is obviously inferior to that of Ti-TMS1 prepared using dodecylphosphate and hexadecylphosphate as templates. After removal of the templates, the mesostructure of the sample (Ti-TMS1) templated by alkylphosphate surfactant was preserved to a greater degree than that of the sample (Ti-TMS2) templated by alkylamine surfactant. Several other factors on the form of the structure and removal of the template were discussed. The photocatalytic activity of Ti-TMS was also investigated by using 2,4,6-trichlorophenol (TCP) solution as a model wastewater. It was found that the photocatalytic degradation of TCP over Ti-TMS occurred at a much faster rate than that over TiO2 nanoparticles.

Investigating the state of Fe and La in MCM-41 mesoporous molecular sieve materials

Abstract Fe-containing, La-containing, siliceous and aluminum silicate MCM-41 mesoporous materials were synthesized using water glass as silica source. The states of Fe(III) and La(III) species were investigated by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), framework infrared (FTIR), electron spin resonance (ESR) and Mossbauer spectroscopic techniques. It was shown that Fe(III) or La(III) species was incorporated into framework. Because the Fe–O or La–O bond is longer than Si–O bond, Fe(III) or La(III) species was limited to insert into framework and transformed from tetrahedrally coordinated state to octahedrally coordinated state upon calcination to remove template.

Enhancement of organic electroluminescent intensity by charge transfer from guest to host

Abstract It was discussed that the electroluminescent (EL) intensity of the shorter alkyl side chain poly(3-alkylthiophene) (P3AT) could be enhanced by blending a small amount of poly(N-vinylcarbazole) (PVK) into P3AT in the emitting layer. Organic EL diodes with one layer of only poly (3-octylthiophene) (P3OT) and a blend of P3OT and PVK (P3OT/PVK) as EL-emitting layer, sandwiched between indium tin-oxide (ITO) and aluminum electrodes respectively, have been fabricated by spin coating onto ITO. The charge transfer from PVK (guest) to P3OT (host) takes place in the P3OT/PVK EL diode and the EL intensity of the P3OT/PVK diode is much higher than that of only the P3OT diode, indicating that the PVK has power over the P3OT electroluminescence.

The very strong photoluminescent (PL) effect of mesoporous molecular sieve materials

Abstract MCM-41 mesoporous molecular sieve materials with nanometer-sized pores show the very strong photoluminescent (PL) effect and the Al-depleted defect sites are responsible for this strong PL effect of the investigated MCM-41 samples. The porous channel structures of molecular sieves are another factor influencing the investigated PL effect.