Catalytic synthesis of diethyl carbonate with supported Pd-Cu bimetallic nanoparticle catalysts:Cu(Ⅰ) as the active species

Cupric oxide （CuO） and copper-cuprous oxide （Cu-Cu2O） nanoparticles were prepared by a simple hydrothermal method for the synthesis of diethyi carbonate （DEC） from ethanol. During these syntheses, varying NaOH and glucose concentrations were applied to explore and pinpoint the active species. It was found that PdCl2/CuO and PdCI2/Cu-Cu2O both catalysts exhibited good thermal stability and morphology. The results of catalytic tests showed that the catalysts prepared with 5 mol/L NaOH show superior catalytic performances because of their lower extent of agglomeration. It is noteworthy that the PdC12/Cu-Cu2O catalysts were the most active, especially the PdCl2/Cu-Cu2O catalyst prepared with 10 mmol glucose and having a higher Cu2O concentration. In Pd（ll）-Cu（II） （PdCl2/CuO） catalysts, there is an induction period, during which Pd（II） is reduced to Pd（0）, that must occur prior to electron transfer between Pd and Cu, and this can slow the catalytic reaction. To further pinpoint the active species, PdCl2/Cu-Cu2O catalysts with different Cu2O contents were prepared by controlling the dosages of glucose. The maximum DEC yield obtained with these catalysts was 151.9 mg.g-1.h-1, corresponding to an ethanol conversion of 7.2% and 97.9% DEC selectivity on an ethanol basis. Therefore, it was concluded that Cu＋ was the active species in this catalytic system, possibly because a higher proportion of Cu＋ reduces the Pd2＋ concentration and limits the CO oxidation side reaction, thus increasing DEC selectivity. In addition, Cu＋ promotes electron transfer between Pd and Cu without an induction period, which could also promote the catalytic activity.

Sodium fluoride induces apoptosis through reactive oxygen species-mediated endoplasmic reticulum stress pathway in Sertoli cells

Excessive fluoride exposure is known to contribute to reproductive system dysfunction,ultimately leading to pathological damage and apoptosis in cells. Although both oxidative and endoplasmic reticulum（ER） stresses have been implicated in fluorosis, the signaling pathways and their roles in sodium fluoride（Na F）-induced apoptosis of Sertoli cells have been sparsely described. In this study, oxidative damage, ER stress, and apoptosis were analyzed after Sertoli cells were treated with varying doses of Na F for 24 hr. Moreover, the antioxidant N-acetylcysteine（NAC） and pro-apoptotic transcription factor CHOP knockdown were used to clarify the precise interplay between reactive oxygen species（ROS）, ER stress and their roles in NaF-induced apoptosis in Sertoli cells. The present study indicated that NaF significantly decreased cell viability and induced apoptosis in Sertoli cells. In addition, NaF exposure facilitated the accumulation of ROS and increased nuclear translocation of nuclear factor erythroid 2-related factor 2（Nrf2） in Sertoli cells. Treatment with NAC caused remarkable recovery from these NaF-induced responses. Meanwhile, excessive NaF triggered ER stress as evidenced by up-regulated glucose-regulated protein 78 k Da（GRP78）, PKR-like ER kinase（PERK）, phosphorylation of eukaryotic translation initiation factor 2α（p-eI F2α） and CCAAT/enhancer-binding protein-homologous protein（CHOP）, without affecting total eukaryotic translation initiation factor 2α（e IF2α）. NAC effectively blocked the activation of ER stress, suggesting that Na F-induced ROS is an early event that triggers ER stress. Taken together, the results demonstrate that the ROS-mediated ER stress pathway is the crucial mechanistic event involved in NaF-induced apoptosis of Sertoli cells.