Facile synthesis of efficient pentaethylenehexamine-phosphotungstic acid heterogeneous catalysts for oxidative desulfurization

The ultra-deep desulfurization of oil needs to be solved urgently due to various problems,including environmental pollution and environmental protection requirements.Oxidative desulfurization(ODS)was considered to be the most promising technology.The facile synthesis of highly efficient and stable HPW-based heterogeneous catalysts for oxidative desulfurization is still a challenging task.In this paper,pentamethylene hexamine(PEHA)and phosphotungstic acid(HPW)were combined by a simple one-step method to prepare a heterogeneous catalyst of PEHA-HPW for the production of ultra-deep desulfurization fuel oil.The composite material exhibited excellent catalytic activity and high recyclability,which could reach a 100% dibenzothiophene(DBT)removal rate in 30 min and be recycled at least 5 times.Experiments and DFT simulations were used to better examine the ODS mechanism of PEHA-HPW.It was proved that the rich amino groups on the surface of PEHA-HPW play a crucial role.This work provides a simple and feasible way for the manufacture of efficient HPW-based catalysts.

Highly stable lead-free Cs3Bi2I9 perovskite nanoplates for photodetection applications

Lead halide perovskites have received tremendous attentions recently for their excellent properties such as high light absorption coefficient and long charge carrier diffusion length. However, the stability issues and the existence of toxic lead cations have largely limited their applications in optoelectronic area. Herein, we report the synthesis and investigation of highly stable and lead-free Cs3Bi2I9 perovskite nanoplates for visible light photodetection applications. The Cs3Bi2I9 nanoplates were synthesized through a facile solution-processed method, which is also applicable to various substrates. The achieved nanoplates present very good crystal quality and exhibit excellent long-term stability even exposed in moist air for several months. Photodetectors were constructed based on these high-quality perovskite nanoplates for the first time, and display a maximum photoresponsivity of 33.1 mA/W under the illumination of 450 nm laser, which is six times higher than the solution-synthesized CH3NH3PbI3 nanowire photodetectors. The specific detectivity of these devices can reach up to 10^10 Jones. Additionally, the devices exhibit fast rise and decay time of 10.2 and 37.2 ms, respectively, and highly stable photoswitching behavior with their photoresponse well retaining under alternating light and darkness. This work opens up a new opportunity for stable and low-toxic perovskite-based optoelectronic applications.

High-performance optoelectronic devices based on van der Waals vertical MoS2/MoSe2 heterostructures

Monolayer MoS2 is a direct band gap semiconductor with large exciton binding energy,which is a promising candidate for the application of ultrathin optoelectronic devices.However,the optoelectronic performance of monolayer M0S2 is seriously limited to its growth quality and carrier mobility.In this work,we report the direct vapor growth and the optoelectronic device of verticallystacked MoS2/MoSe2 heterostructure,and further discuss the mechanism of improved device performance.The optical and high-resolution atomic characterizations demonstrate that the heterostructure interface is of high-quality without atomic alloying.Electrical transport measurements indicate that the heterostructure transistor exhibits a high mobility of 28.5 cm^2/(V·s)and a high on/off ratio of 10^7.The optoelectronic characterizations prove that the heterostructure device presents an enhanced photoresponsivity of 36 A/W and a remarkable detectivity of 4.8×10^11 Jones,which benefited from the interface induced built-in electric field and carrier dependent Coulomb screening effect.This work demonstrates that the construction of two-dimensional(2D)semiconductor heterostructures plays a significant role in modifying the optoelectronic device properties of 2D materials.