Gallium oxide nanorods: novel, template-free synthesis and high catalytic activity in epoxidation reactions.

Gallium oxide nanorods with unprecedented small dimensions (20-80 nm length and 3-5 nm width) were prepared using a novel, template-free synthesis method. This nanomaterial is an excellent heterogeneous catalyst for the sustainable epoxidation of alkenes with H2 O2 , rivaling the industrial benchmark microporous titanosilicate TS-1 with linear alkenes and being much superior with bulkier substrates. A thorough characterization study elucidated the correlation between the physicochemical properties of the gallium oxide nanorods and their catalytic performance, and underlined the importance of the nanorod morphology for generating a material with high specific surface area and a high number of accessible acid sites.

Transition-metal-free catalysts for the sustainable epoxidation of alkenes: from discovery to optimisation by means of high throughput experimentation.

Transition-metal-free oxides were studied as heterogeneous catalysts for the sustainable epoxidation of alkenes with aqueous H2O2 by means of high throughput experimentation (HTE) techniques. A full-factorial HTE approach was applied in the various stages of the development of the catalysts: the synthesis of the materials, their screening as heterogeneous catalysts in liquid-phase epoxidation and the optimisation of the reaction conditions. Initially, the chemical composition of transition-metal-free oxides was screened, leading to the discovery of gallium oxide as a novel, active and selective epoxidation catalyst. On the basis of these results, the research line was continued with the study of structured porous aluminosilicates, gallosilicates and silica-gallia composites. In general, the gallium-based materials showed the best catalytic performances. This family of materials represents a promising class of heterogeneous catalysts for the sustainable epoxidation of alkenes and offers a valid alternative to the transition-metal heterogeneous catalysts commonly used in epoxidation. High throughput experimentation played an important role in promoting the development of these catalytic systems.

Facile synthesis of silica monolith doped with meso-tetra(p-carboxyphenyl)porphyrin as a novel metal ion sensor.

A novel metal ion sensor was prepared using silica monolith doped with meso-tetra(p-carboxyphenyl)porphyrin. The doped material was prepared using TEOS:EtOH:H(2)O:HCl:porphyrin molar ratios of 1:5:7:3.1 x 10(-2):2.3 x 10(-5), respectively. The mixture was kept 16 days for the gelation process and then the wet gel was dried at 55-60 degrees C for 3 days. The porphyrin-doped monolith obtained was kept in 1 M metal salt solution for 2 days. The visible spectrum of the metal-coordinated porphyrin-doped monolith was compared with the uncoordinated porphyrin-doped monolith. The spectra show the characteristic maxima for Cu(2+) at 543 nm, for Zn(2+) at 522, 559, and 596 nm, for Pb(2+) at 531 and 559 nm, and for Ni(2+) at 522 and 551 nm. The metal coordinated to the silica monolith could be removed by washing with 1 M HNO(3). However the Cu(2+) could not be eluted by acidic solution due to its strong bonding to the porphyrin. The results show that this porphyrin-doped monolithic biomaterial is a promising sensor for metal ions in wastewater and other harsh environments.