SignificanceBlack phosphorus (BP) nanosheet is a “hot” class of 2D material having wide applications in optoelectronics, catalysis, biomedicine, etc. However, facile synthesis of BP nanosheets is not achieved by far. Currently, BP nanosheets are mainly prepared via solution-based exfoliation of bulk crystals, a process that is complicated, time-consuming, and costly. Moreover, the as-prepared BP nanosheets are not stable. Here, we developed a facile bottom-up protocol for preparing BP nanosheets in solution at low temperature. Our synthetic procedure is conceptually simple and can be performed in common chemical laboratories. The estimated synthesis cost is less than 1 US dollar per gram. Our work, therefore, offers the community an unlimited access to such 2D material.

Solar-driven water splitting using powdered catalysts is considered as the most economical means for hydrogen generation. However, four-electron-driven oxidation half-reaction showing slow kinetics, accompanying with insufficient light absorption and rapid carrier combination in photocatalysts leads to low solar-to-hydrogen energy conversion efficiency. Here, we report amorphous cobalt phosphide (Co-P)-supported black phosphorus nanosheets employed as photocatalysts can simultaneously address these issues. The nanosheets exhibit robust hydrogen evolution from pure water (pH = 6.8) without bias and hole scavengers, achieving an apparent quantum efficiency of 42.55% at 430 nm and energy conversion efficiency of over 5.4% at 353 K. This photocatalytic activity is attributed to extremely efficient utilization of solar energy (~75% of solar energy) by black phosphorus nanosheets and high-carrier separation efficiency by amorphous Co-P. The hybrid material design realizes efficient solar-to-chemical energy conversion in suspension, demonstrating the potential of black phosphorus-based materials as catalysts for solar hydrogen production.

Novel Y2(MoO4)3:Eu3+ red phosphors were synthesized through a simple coprecipitation process and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and fluorescent spectrophotometry. The results of XRD and FE-SEM show that resultant samples are single phase and have flowerlike shape. In the excitation spectra of Y2(MoO4)3:Eu3+ phosphors, by monitoring 616 nm, the charge transfer bands (CTB) of Eu3+→O2- and Mo6+→O2- centering at around 264 and 310 nm can be observed, respectively. Moreover, the intensity ratio of charge transfer band between Eu3+→O2- and Mo6+→O2- increases with increasing Eu3+ ions doping concentration. The characteristic red emission at around 616 nm of Eu3+ ions is also observed, ascribed to the 5D0→7F2 transition of Eu3+ ions, and the optimal doping concentration is 12 mol %. Finally, the Ωλ (λ = 2 and 4) intensity parameters and Huang−Rhys factor were also calculated according to Judd−Ofelt theory and multiphonon relaxation theory, respectively.

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La2(MoO4)3 phosphors with various Eu3+ concentrations were prepared via a facile co-precipitation process. The crystal structure and morphology of the phosphors were characterized by means of XRD and field emission scanning electron microscope. The crystal unit cell parameters a, b, and c for the monoclinic phase La2(MoO4)3 were calculated to be 16.989, 11.927, and 16.086 Å, respectively. The average size of the phosphor particles was estimated to be around 88.5 nm. The Huang–Rhys factor was derived from the phonon sideband spectra to be 0.073. The self-generated quenching process of Eu3+ was explained based on Auzel’s model, and the intrinsic radiative transition lifetime for 5D0 level was confirmed to be 0.99 ms. A new approach for calculating the Judd–Ofelt parameters was developed, meanwhile the Judd–Ofelt parameters Ωλ (λ = 2, 4, 6) of Eu3+ in La2(MoO4)3 phosphors were confirmed to be 10.70 × 10−20, 1.07 × 10−20, and 0.56 × 10−20 cm2, respectively. Finally, the optimal doping concentration for achieving maximum emission intensity was confirmed to be 17 mol. % by analyzing the concentration quenching.