We report the first-order and high-order Raman scattering from core-shell CdSe/CdS nanocrystals and investigate the evolution of the longitudinal mode of CdSe (LO1) and CdS (LO2), and the surface mode of CdSe (SO1) and CdS (SO2) with increasing shell thickness (0-5.5 ML (monolayer)). We find that the shift of the LO2 peak from 268 to 291 cm(-1) agrees well with the theoretical values based on the phonon confinement model. The variation of the dielectric environment of the CdSe core with increasing CdS shell thickness is modified according to the shift of SO1 from 198 to 185 cm(-1). The SO2 modes at 267 and 275 cm(-1), corresponding to the shell thickness 3.5 and 5.5 ML in CdSe/CdS nanocrystals, respectively, are also obtained for the first time in our experiment. Moreover, they agree well with the theoretical values of the dielectric corresponding function model. Besides, a new Raman peak at 482 cm(-1) is observed, and it remains at that value with shell growth, the new peak is supposed to be caused by the alloying at the core-shell interface. Therefore, Raman spectroscopy can be used to determine the shell thickness and other surface and interface parameters of CdSe/CdS core-shell nanocrystals.

A large number of reagents have been developed for the synthesis of trifluoromethylated compounds. However, an ongoing challenge in trifluoromethylation reaction is the use of less expensive and practical trifluoromethyl sources. We report herein the unprecedented direct trifluoromethylation of (hetero)arenes using trifluoromethanesulfonic anhydride as a radical trifluoromethylation reagent by merging photoredox catalysis and pyridine activation. Furthermore, introduction of both the CF and OTf groups of the trifluoromethanesulfonic anhydride into internal alkynes to access tetrasubstituted trifluoromethylated alkenes was achieved. Since trifluoromethanesulfonic anhydride is a low-cost and abundant chemical, this method provides a cost-efficient and practical route to trifluoromethylated compounds.

Bromodifluoromethylphosphonium bromide was solely used as the precursor of difluorocarbene. Herein, an unprecedented visible-light-induced hydrodifluoromethylation of alkenes with bromodifluoromethylphosphonium bromide using H2O and THF as hydrogen sources for the synthesis of difluoromethylated alkanes is described. This difluoromethylation is characterized by mild reaction conditions, ready availability of reagents, and excellent functional-group tolerance.

The primary objective of this study is to estimate publics' willingness to pay (WTP) for environment conservation and analyze factors influencing WTP. A questionnaire survey based on the contingent valuation method (CVM) was carried out at Kanas Nature Reserve, Xinjiang, China. Seventy-three percent of the 412 respondents were willing to pay at different levels, and the mean WTP value was RMB 54.60 ($8.03). The results of this survey struck an optimistic note that publics were willing to contribute to improve environmental quality. Logistic regression analysis was employed to compare the characteristics of those who were and were not willing to pay. Chi-square tests were administered to identify the relationships between various explanatory factors and WTP. Conclusions and implications of the empirical study can be provided to policy makers and site managers. In a wider sense, the findings of this study should make a good contribution to the literature related to WTP for environment conservation of natural attractions.

A process for tunable and chemo-, regio-, and stereoselective photocatalytic trifluoromethylation of styrenes was developed. Thermodynamically stable E-trifluoromethylated alkenes were prepared using Togni's reagent in the presence of Ru(bpy)3Cl2·6H2O under visible light irradiation, whereas less thermodynamically stable Z-trifluoromethylated alkenes were obtained by employing Umemoto's reagent and photocatalyst Ir(ppy)3.