Green synthesis of PbCrO4 nanostructures using gum of ferula assa-foetida for enhancement of visible-light photocatalytic activity

Visible-Light-Driven Oxidative Cleavage of Alkenes Using Water-Soluble CdSe Quantum Dots

The oxidative cleavage of C=C bonds is an important chemical reaction, which is a popular reaction in the photocatalytic field. However, high catalyst-loading and low turnover number (TON) are general shortcomings in reported visible-light-driven reactions. Herein, the direct oxidative cleavage of C=C bonds through water-soluble CdSe quantum dots (QDs) is described under visible-light irradiation at room temperature with high TON (up to 3.7×10⁴ ). Under the same conditions, water-soluble CdSe QDs could also oxidize sulfides to sulfoxides with 51-84 % yields and TONs up to 3.4×10⁴ . The key features of this photocatalytic protocol include high TONs, wide substrates scope, low catalyst loadings, simple and mild reaction conditions, and molecular O₂ as the oxidant.

Putting the Squeeze on Lead Chromate Nanorods

We have studied by means of X-ray diffraction and Raman spectroscopy the high-pressure behavior of PbCrO₄ nanorods. We have found that these nanorods follow a distinctive structural sequence that differs from that of bulk PbCrO₄. In particular, a phase transition from a monoclinic monazite-type PbCrO₄ to a novel monoclinic AgMnO₄-type polymorph has been discovered at 8.5 GPa. The crystal structure, Raman-active phonons, and compressibility of this novel high-pressure phase are reported for the first time. The experimental findings are supported by ab initio calculations that provide information not only on structural and vibrational properties of AgMnO₄-type PbCrO₄ but also on the electronic properties. The discovered phase transition triggers a band gap collapse and a subsequent metallization at 44.2 GPa, which has not been observed in bulk PbCrO₄. This suggests that nanoengineering can be a useful strategy to drive metallization under compression.