Direct Z-scheme GaN/WSe2 heterostructure for enhanced photocatalytic water splitting under visible spectrum.

van der Waals heterostructures are widely used in the field of photocatalysis due to the fact that their properties can be regulated via an external electric field, strain engineering, interface rotation, alloying, doping, etc. to promote the capacity of discrete photogenerated carriers. Herein, we fabricated an innovative heterostructure by piling monolayer GaN on isolated WSe2. Subsequently, a first principles calculation based on density functional theory was performed to verify the two-dimensional GaN/WSe2 heterostructure and explore its interface stability, electronic property, carrier mobility and photocatalytic performance. The results demonstrated that the GaN/WSe2 heterostructure has a direct Z-type band arrangement and possesses a bandgap of 1.66 eV. The built-in electric field is caused by the transfer of positive charge between the WSe2 layers to the GaN layer, directly leading to the segregation of photogenerated electron-hole pairs. The GaN/WSe2 heterostructure has high carrier mobility, which is conducive to the transmission of photogenerated carriers. Furthermore, the Gibbs free energy changes to a negative value and declines continuously during the water splitting reaction into oxygen without supplementary overpotential in a neural environment, satisfying the thermodynamic demands of water splitting. These findings verify the enhanced photocatalytic water splitting under visible light and can be used as the theoretical basis for the practical application of GaN/WSe2 heterostructures.

Quantitative detection of fecal contamination with domestic poultry feces in environments in China.

Poultry are an important source of fecal contamination in environments. However, tools for detecting and tracking this fecal contamination are in the early stages of development. In practice, we have found that source tracking methods targeting the 16S rRNA genes of poultry-specific microbiota are not sufficiently sensitive. We therefore developed two quantitative PCR assays for detection of poultry fecal contamination, by targeting chicken and duck mitochondrial genes: NADH dehydrogenase subunit 5 (ND5) and cytochrome b (cytb). The sensitivity of both assays was 100% when tested on 50 chicken and duck fecal samples from 10 provinces of China. These assays were also tested in field samples, including soil and water collected adjacent to duck farms, and soils fertilized with chicken manure. Poultry mitochondrial DNA was detected in most of these samples, indicating that the assays are a robust method for monitoring environmental contamination with poultry feces. Complemented with existing indicators of fecal contamination, these markers should improve the efficiency and accuracy of microbial source tracking.

Highly efficient synthesis of quinoxaline derivatives from 1,2-benzenediamine and α-aminoxylated 1,3-dicarbonyl compounds.

Simple and efficient synthetic procedures for the preparation of quinoxaline, pyrazine, pyridopyrazine, and benzoxazin-2-one derivatives were developed. The one-pot cascade process involves the acidic elimination of α-aminoxylated dicarbonyl compounds to generate 1,2,3-tricarbonyl compounds and subsequent condensation with 1,4-N,N or -N,O dinucleophiles to afford quinoxaline, pyrazine, pyridopyrazine, and benzoxazin-2-one scaffolds. All the proposed processes do not need extra catalysts, dry solvents, or harsh reaction conditions.

Synthesis and antitumor activity evaluation of lamiridosin A derivatives.

A series of lamiridosin A derivatives were synthesized through simple procedures. Their antitumor activities were evaluated against EC9706, MGC803, and B16 cell lines in vitro. Several compounds showed potent antitumor activity, especially compound 10, with IC50 value of 2.36 µmol/L against MGC803 cell lines, is more potent than marketed positive drug 5-fluorouridine (5-FU).

[Chemical Constituents from Melissa officinalis Leaves].

OBJECTIVE: To investigate the chemical constituents of Melissa officinalis leaves. METHODS: The chemical constituents were separated by silica gel column chromatography and their structures were determined by spectroscopic experiments. RESULTS: 13 compounds were isolated and identified as protocatechuyl aldehyde(1), serratagenic acid(2), vanillin(3), 2α,3ß-dihydroxy-urs-12-en-28-oic acid(4), ursolic acid(5), oleanolic acid(6), daucosterol(7),2α,3ß,23,29-tetrahydroxyolean-12-en-28-oic acid-29-O-ß-D-gluco- pyranoside(8), luteolin(9) rosmarinic acid(10), luteolin-7-O-ß-D-glucoside (11), ß-stitosterol(12) and palmitic acid(13). CONCLUSION: Compounds 1 ~ 8 are separated from this plant for the first time and compounds 1-4 and 8 are isolated from this genus for the first time.