Intensive field measurements of formaldehyde (HCHO) and acetaldehyde (CH 3 CHO) were concurrently conducted at a mountain site (TMS) and an urban site (TW) at the foot of the same mountain in Hong Kong from September to November 2010. The spatiotemporal variations of HCHO and CH 3 CHO, the correlation between HCHO and CH 3 CHO and the ratios of HCHO/CH 3 CHO indicated different impacts of primary emissions and secondary formation at the two sites. The source apportionments of HCHO and CH 3 CHO at both sites were investigated using the Positive Matrix Factorization (PMF) model, while the in-situ formation of HCHO and CH 3 CHO was estimated using a Photochemical Box Model coupled with Master Chemical Mechanism (PBM-MCM). At TMS, the in-situ formation was the most significant contributor to ambient HCHO and CH 3 CHO, accounting for 51 ± 5 and 32 ± 2%, respectively, followed by the transport of photochemicallyformed aldehydes, vehicular emissions, biogenic emissions, biomass burning and solvent usage. On the other hand, at TW, the in-situ formation and vehicular emissions explained 55 ± 7% and 18 ± 1% of ambient HCHO, respectively, while vehicular emissions and in-situ formation made comparable contributions to CH 3 CHO (~35%). The findings are helpful for the formulation and implementation of appropriate control strategies for aldehydes and their precursors in Hong Kong.
Molybdenum selenide (MoSe 2 ) has been extensively studied in recent years due to its strong absorption for sunlight and unique band structure. Herein, a self-assembly three-dimensional (3D) MoSe 2 nano owers were prepared by a two-step process. Signi cantly, the photodetection device based on MoSe 2 nano owers exhibited a maximum responsivity about 12.39mA/W and a rapid photo-response time about 0.15s at 0V bias under simulated sunlight exposure bene ting from its large speci c surface area and unique morphologic structure. Meanwhile, we demonstrated the outstanding stability after two weeks of the photodetection device. In this way, the MoSe 2 nano ower-based photodetectors enriched the basic research of molybdenum selenide and provided some reference for the following researches based on molybdenum selenide.
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