Xiutao Li

Effective low-temperature hydrolysis of cellulose catalyzed by concentrated H3PW12O40 under microwave irradiation

Concentrated H3PW12O40 (HPW) was first employed to decompose cellulose under microwave irradiation at low temperatures. 75.6% yield of glucose was obtained at 90 °C under microwave irradiation for 3 h, which was considerably high under such mild conditions using phosphotungstic acid as a catalyst. With the same effective acid concentration, HPW gave the highest cellulose conversion and glucose yield among the Bronsted acid catalysts, indicating that the strong Bronsted acid played an important role during cellulose hydrolysis. In the hydrolysis of cellulose with HPW as catalysts, microwave irradiation led to higher glucose yields than the conventional heating method. The recovery and reusability of HPW were investigated by extraction with diethyl ether from the reaction solution. At the same time, the performance of the concentrated HPW for real lignocellulosic biomass (corncob, corn stover and bagasse) hydrolysis was also investigated.

Sulfonated copolymers with SO3H and COOH groups for the hydrolysis of polysaccharides

The well-defined sulfonated block copolymer poly(acrylic acid)-block-poly(styrene sulfonic acid) (PAA-b-PSSH) and the random copolymer poly(acrylic acid)-random-poly(styrene sulfonic acid) (PAA-r-PSSH) were prepared by direct thermolysis of the precursor copolymers poly(tert-butyl acrylate)-block-poly(neopentyl styrenesulfonate) (PtBA-b-PNSS) and poly(tert-butyl acrylate)-random-poly(neopentyl styrenesulfonate) (PtBA-r-PNSS), which were synthesized by living radical polymerization (MWD < 1.10) catalyzed with CuBr. GPC, EA, 1H NMR and FT-IR spectra were employed to characterize the structure of the synthesized acid polymers. The catalytic performance of the acid polymers was evaluated for the hydrolysis of starch and cellulose in aqueous solution under microwave irradiation. With the same effective acid concentration, the random copolymer PAA-r-PSSH gave the highest glucose yield among the prepared catalysts. It is believed that the good results were caused by the synergic effect of the SO3H and COOH groups in the polymer chain. In addition, microwave irradiation led to better glucose yields in the hydrolysis of polysaccharides than the conventional heating method with acid polymers as catalysts.

Enzyme-mimetic catalyst-modified nanoporous SiO2-cellulose hybrid composites with high specific surface area for rapid H2O2 detection.

Mesoporous silica-cellulose hybrid composites were prepared by surface sol-gel coating process on nature cellulose substance. The template CTAB (hexadecyl trimethyl ammonium Bromide) in the silica film can be removed by extraction to obtain high specific surface area (80.7 m(2) g(-1)), which is 2 orders of magnitude higher than that of raw cellulose. In the following, the enzyme-mimetic catalyst and chromogenic agent were introduced onto the hybrid system. Just as the peroxidase, the resultant hybrid material exhibits extraordinary sensitivity for the H2O2 and shows an immediate and obvious color change. The detection limit is about 1 μmol L(-1) by the naked eye.

Effective TiO2 hybrid heterostructure fabricated on nano mesoporous phenolic resol for visible-light photocatalysis

Highly homogeneous TiO2@phenolic resol hybrid nanocomposites are fabricated by a solvothermal method. In such nanostructures, the TiO2 particles are tightly grafted on the surface of nano mesoporous phenolic resols to form uniform heterostructures. Significantly, a charge transfer complex was formed at the interface of the TiO2 and the nano mesoporous phenolic resols, which led to visible-light absorption over the full range. The nano hybrid material exhibited excellent performance for the photocatalytic degradation of dyes and produced photocurrent signals under visible-light. The investigation of the mechanism indicated that the O2˙− was the main active species during the photochemical process. The hybrid nanocomposites also showed considerably high stability in the photocatalysis. It is expected that this approach can provide a new strategy for the design of some bio-inspired catalysts for sustainable technology.

Photoresponse simulation of visible blind GaN/AlGaN p-i-n photodiode

The spectral photoresponse characteristics for visible blind GaN/AlGaN p-i-n photodiode have been numerically studied. Effects of the absorption layer thickness and the n-layer thickness on the photoresponse spectra have been investigated. Our work shows that the absorption layer thickness and n-layer thickness have important impact on the peak value of photoresponse spectra and rejection ratio of short-wavelength side, respectively.

Electro-optical characteristics for AlGaN solar-blind p-i-n photodiode: Experiment and simulation

The fabrication and modeling for solar-blind AlGaN-based p-i-n photodiode have been presented. The simulated dark current characteristics are in good agreement with the experiments. It is found that the peak responsivity of 0.005A/W can be achieved at 265nm corresponding to the cutoff wavelength of the Al0.45Ga0.55N absorption layer. The transmission spectra drop to nearly zero due to the intense light absorption of n-type Al0.65Ga0.35N layer.

Electro-optical characteristics of separate absorption and multiplication GaN avalanche photodiode

The fabrication and electro-optical characteristics for separate absorption and multiplication GaN avalanche photodiode have been presented. The multiplication gain as a function of reverse bias at room temperature is also obtained. It is found that multiplication gain monotonically increases with increasing reverse bias, high multiplication gain of 3×105 at 110V is achieved