Energy-level dependent H_2_O_2 production on metal-free,carbon-content tunable carbon nitride photocatalysts

Light-driven production of H2O2 from water and molecular oxygen could be a promising way for obtaining both solar fuels and fundamental chemicals. During that process, the H2O2 yield is strongly dependent on the reaction pathway associated with two-electron reduction of dioxygen by the photo-generated electrons. Herein, we synthesized a series of metal-free, carbon-content tunable carbon nitride photocatalysts（named C3N4-Carbon） by a facile hydrothermal reaction and subsequent thermal treatment at appropriate temperatures. The energy levels of the C3N4-Carbon catalysts vary with the carbon doping level, which is conveniently tuned by changing the initial glucose concentration during the hydrothermal reaction. The surface carbon species evolve with the carbon content and the nitrogen atoms in the structure of carbon nitride are partially substituted by foreign carbon atoms based on XPS measurements. The optimal catalyst leads to the highest H2O2 yield of 1271 μmol L-1 in an acidic aqueous solution（pH 3） after a reaction period of 4 h, twice higher than the pristine C3N4. In addition, the largest formation rate constant and the smallest decomposition rate constant of H2O2 are obtained on the optimal one according to the kinetics analyses. The decomposition tests of H2O2 indicate that the formation rate could be a dominant factor impacting the H2O2 yield. The conduction band position of the optimal catalyst is positively shifted to 0.06 V versus RHE, which is more favorable to the reduction of dioxygen to H2O2（O2/H2O2 at 0.69 V versus RHE）. The positive shift of valence band also improves hole collection and leads to enhanced formation of H2O2.

Synthesis and ultraviolet/aggregation-induced emission investigation of novel tetraphenylvinyl hydrazone derivatives: efficient multimodal chemosensors for fluoride ion

Herein,three novel tetraphenylethylene hydrazone chemosensors TC12,SC16,and TC16 are prepared for the selective detection of F−.Two NH and one C=N units are incorporated into the sensors for better colorimetric responses,whereas the tetraphenyl unit is in charge of the aggregation-induced emission effect.Among them,compounds SC16 and TC16 form stable gels with some organic solvents.All the tetrahydrofuran/H2O solutions of the three compounds exhibit aggregation-induced emission effect,whereby the fluorescence emission increases by varying degrees with the volume of poor solvent water.Moreover,good aggregation-induced emission effects are observed in the self-assembly of SC16 and TC16.As a sample chemosensor,TC12 in tetrahydrofuran responds to F−selectively with high sensitivity,with the colorimetric and fluorometric detection limits of 8.25×10^(−7) mol·L^(-1) and 2.69×10^(−7) mol·L^(-1),respectively.The reversible gel-sol-gel phase transition and color changes indicate that both SC16-dimethyl sulfoxide and TC16-ethyl acetate gels specifically respond to F-with good sensitivity.The detection results are well supported by ultraviolet-visible spectroscopy,fluorescent spectroscopy,and 1H nuclear magnetic resonance.More importantly,the driving forces of gelation are visually clarified through the single crystal X-ray analysis of compound TOMe.

The involvement of wheat U-box E3 ubiquitin ligase TaPUB1 in salt stress tolerance

U-box E3 ubiquitin ligases play important roles in the ubiquitin/26 S proteasome machinery and in abiotic stress responses. Ta PUB1-overexpressing wheat(Triticum aestivum L.) were generated to evaluate its function in salt tolerance. These plants had more salt stress tolerance during seedling and flowering stages, whereas the Ta PUB1-RNA interference(RNAi)-mediated knock-down transgenic wheat showed more salt stress sensitivity than the wild type(WT). Ta PUB1 overexpression upregulated the expression of genes related to ion channels and increased the net root Na+efflux, but decreased the net K+efflux and H+influx, thereby maintaining a low cytosolic Na+/K+ratio, compared with the WT. However,RNAi-mediated knock-down plants showed the opposite response to salt stress. Ta PUB1 could induce the expression of some genes that improved the antioxidant capacity of plants under salt stress. Ta PUB1 also interacted with Ta MP(Triticum aestivum α-mannosidase protein), a regulator playing an important role in salt response in yeast and in plants. Thus, low cytosolic Na+/K+ratios and better antioxidant enzyme activities could be maintained in wheat with overexpression of Ta PUB1 under salt stress. Therefore, we conclude that the U-box E3 ubiquitin ligase Ta PUB1 positively regulates salt stress tolerance in wheat.