Loading effects of silver oxides upon generation of reactive oxygen species in semiconductor photocatalysis

Superoxide anion radical (O(2)(-*)) and OH radical generations in suspensions of Ag metal-, Ag(2)O-, or AgO-loaded TiO(2) and BiVO(4) photocatalysts in alkaline conditions (pH 12.0) were examined by means of a luminol chemiluminescence (CL) technique and a spin-trapping fluorescence one in which terephthalic acid reacts with an OH radical to afford the highly fluorescent 2-hydroxyterephthalic acid (TAOH), respectively. The observed luminol CL intensity was remarkably enhanced by the AgO loading on TiO(2) as well as BiVO(4). This can be explained by enhancement of O(2)(-*) production on the AgO-loaded photocatalysts caused by the synergetic effects on the thermocatalytic activity upon the AgO surface and the efficient electron-hole separation at the photocatalyst/AgO interface. On the other hand, loading effects of AgO on the TAOH formation were not so significant compared to those on the CL observation, though the TAOH formation rates for the TiO(2) samples were much larger than those for the BiVO(4) ones by about three orders of magnitude. The properties of O(2)(-*) and OH radical generations on these photocatalysts are discussed on the basis of the luminol CL kinetics and approximate band edge positions of TiO(2), BiVO(4), and silver oxides.     

Isolation and structures of biselyngbyasides B,C, and D from the marine cyanobacterium Lyngbya sp., and the biological activities of biselyngbyasides

Bioassay-guided fractionation of the marine cyanobacterium Lyngbya sp. led to the isolation of biselyngbyasides B (3), C (4), and D (5), novel analogs of biselyngbyaside (1) and biselyngbyolide A (2). The gross structures of 3–5 were determined by NMR spectral analyses, and their stereochemistries were established based on NOESY spectra and CD data. Biselyngbyasides (1–3) showed growth-inhibitory activity and apoptosis-inducing activity against both HeLa S₃ cells and HL60 cells. The fura-2 method revealed that biselyngbyasides (1–3) increased the cytosolic Ca²⁺ concentration in HeLa S₃ cells.     

Synergistic hybrid catalyst for cyclic carbonate synthesis: remarkable acceleration caused by immobilization of homogeneous catalyst on silica

The catalytic activity of phosphonium salts towards cyclic carbonate synthesis from propylene oxide and CO2 has been enormously enhanced by their immobilization onto silica that itself has no catalytic activity.