Chak-Tong Au

Photocatalytic degradation of norfloxacin on different TiO2−X polymorphs under visible light in water

Reduced TiO2 (TiO2−X) materials with different crystallographic structures were prepared and characterized. Cat.I-A, Cat.II-R, Cat.III-B are TiO2−X with anatase, rutile and brookite structures, respectively, while the Cat.IV-A&R series are materials with anatase and rutile phases mixed in different ratios. All samples exhibit efficient photocatalytic activity for the degradation of norfloxacin (Nor) under visible light, and Cat.IV-A&R-4 is the best among the samples studied. Our results show that the photocatalytic activity is governed by different factors such as the specific surface area of the catalysts as well as the concentrations of Ti3+ and the density of oxygen vacancies in the photocatalytic materials. Mechanistic study of the materials demonstrates that photohole (h+) transfer contributes more to Nor degradation than reaction with ˙OH radicals and the other reactive oxygen species (ROSs). Intermediate species were characterized by HPLC-TOF-HRMS and HPLC-MS/MS to construct a general transformation mechanism of Nor on the family of TiO2−X under visible light. The study shows that Nor adsorption onto TiO2−X occurs by its heteroatoms followed by cleavage of its piperazine ring and hydroxylation of its quinolone ring under the attack of h+ and ˙OH radicals. The study could assist the further search for efficient photocatalytic materials for the degradation of organic pollutants.

Zirconocene-catalyzed direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1 : 1 ratio under solvent-free conditions

A highly efficient way for the direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1 : 1 ratio using a zirconocene complex (1, 1 mol%), a strong Lewis acid of good water tolerance, as a catalyst under solvent-free conditions has been developed. A wide range of acid and alcohol (esters) substrates undergo (trans)esterification to produce carboxylic ester motifs in moderate to good or excellent yields with good functional tolerance, such as that towards C–Br as well as CC and CC bonds. And complex 1 can be recycled six times without showing a significant decline in catalytic efficiency. It was demonstrated that cyclandelate, which is used to treat high blood pressure as well as heart and blood-vessel diseases, can be directly synthesized on a gram scale with 81% yield (6.70 g) using complex 1.

Palladium-Catalyzed Regio- and Stereoselective Coupling–Addition of Propiolates with Arylsulfonyl Hydrazides: A Pattern for Difunctionalization of Alkynes

A new pattern for difunctionalization of alkynes via a palladium-catalyzed regio- and stereoselective coupling-addition of propiolates with arylsulfonyl hydrazides is disclosed. The approach enables the synthesis of various highly functionalized ( E)-vinylsulfones in satisfactory yields. Arylsulfonyl hydrazides act as both aryl and sulfonyl sources via selective cleavage of Ar(C)-S and S-N bonds, which are simultaneously incorporated onto the terminal carbon atom of an alkyne molecule.

Crystal structure of bis{5H-dibenzo[c,f][1,5]oxabismocin-12(7H)-yl} carbonate, C29H24O5Bi2

Abstract C29H24O5Bi2, orthorhombic, Pbca (no. 61), a = 14.8835(6) Å, b = 14.5551(6) Å, c = 23.6000(9) Å, V = 5112.5(4) Å3, Z = 8, Rgt(F) = 0.0293, wR(F2) = 0.0579, T = 296(2) K.

Crystal structure of 12-chloro-5,6,7,12-tetrahydrodibenzo[c,f][1,5]oxastibocine, C14H12ClOSb

Abstract C14H12ClOSb, triclinic, P1̄ (no. 2), a = 9.3453(14) Å, b = 10.9826(16) Å, c = 13.303(2) Å, α = 90.823(3)°, β = 90.394(3)°, γ = 108.307(2)°, V = 1296.0(3) Å3, Z = 4, Rgt(F) = 0.0587, wR(F2) = 0.1767, T = 293(2) K.

Construction and Application of a Non-Enzyme Hydrogen Peroxide Electrochemical Sensor Based on Eucalyptus Porous Carbon

Natural eucalyptus biomorphic porous carbon (EPC) materials with unidirectional ordered pores have been successfully prepared by carbonization in an inert atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) were employed to characterize the phase identification, microstructure and morphology analysis. The carbon materials were used to fabricate electrochemical sensors to detect hydrogen peroxide (H2O2) without any assistance of enzymes because of their satisfying electrocatalytic properties. It was immobilized on a glassy carbon electrode (GCE) with chitosan (CHIT) to fabricate a new kind of electrochemical sensor, EPC/CHIT/GCE, which showed excellent electrocatalytic activity in the reduction of H2O2. Meanwhile, EPC could also promote electron transfer with the help of hydroquinone. The simple and low-cost electrochemical sensor exhibited high sensitivity, and good operational and long-term stability.