RESUMO
Low activity and poor product selectivity of CO2 reduction have seriously hampered its further practical application. Introducing p-block atoms to the catalyst is regarded as a promising strategy due to the versatility of p orbitals and diversity of p-block elements. Here, we systematically studied the influence of p-block atom X (X = C, N, O, S, and Se) on CO2 catalytic properties on a Sn(200) surface by first-principles calculation. Our work shows that all the p-block atoms are relative stable with Ef in the range of -5.11 to -3.59 eV. Further calculation demonstrates that the diversity of the p-block atoms results in unique CO2 electrocatalytic activity and product selectivity. Interestingly, the p-block C atom shows bi-functional activity to form two-electron products HCOOH and CO, with the corresponding energy barriers remarkably low at about 0.19 eV and 0.28 eV. In particular, the p-block S(Se) atom appears to have striking HCOOH selectivity, with the energy barrier to form HCOOH only a quarter of that to form the CO product. This unusual behavior is mainly attributed to the adsorption strength and frontier orbital interaction between the p-block atom and intermediates. These findings can effectively provide a valuable insight into the design of highly efficient CO2 electrocatalyst.
RESUMO
Designing photocatalysts with suitable band alignment and considerable carrier mobility is extremely important. Here, by means of first-principles calculation, we systematically investigated the structural, photoelectronic, and carrier mobility behavior of the two-dimensional Janus MoSSe/WSSe superlattice. The results show that both armchair-type (AN-SL) and zigzag-type (ZN-SL) superlattices are relatively stable with negative Ef values in the range of -2.35 to -1.16 eV. Band gap and band edge position calculations demonstrate that these superlattices are completely suitable for water splitting by visible light. Particularly, the interface contact of the superlattice can be spontaneously changed from type-I to type-II when N > 4, facilitating separation of photogenerated carriers. Furthermore, the hole carrier mobility (µh) in AN-SL can be effectively regulated from 1200 to 2200 cm2 V-1 s-1, much larger than that of the isolated components. Interestingly, the disparity of hole/electron carrier mobility is remarkably large with an approximately 20-fold difference, showing the potential in prohibiting the recombination of photogenerated carriers. This unique behavior is further illustrated by the relaxation times of carriers, where the lifetime of hole carriers is about 7 times larger than that of electron carriers. These findings suggest that forming a Janus superlattice is a promising approach for regulating the photoelectronic properties of semiconductors, providing a promising way to design high efficiency photocatalysts.
RESUMO
The role of progesterone in the Toll-like receptor 4 (TLR4)-MyD88-dependent signaling pathway in pre-eclampsia was studied. Peripheral blood mononuclear cells (PBMCs) from pre-eclampsia (PE) patients were subjected to primary culture, and stimulated with different concentrations of progesterone (0, 10(-8), 10(-6), and 10(-4) mol/L). The mRNA expression of TLR4, MyD88 and nuclear factor-kappaB (NF-κB) was detected by using real-time PCR. The Ikappa-B protein expression was detected by using Western blotting. The expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the supernatant was determined by using ELISA. With the concentrations of progesterone increasing, the mRNA expression levels of TLR4, MyD88 and NF-κB in 2(-ΔΔCT) value were significantly decreased, and the IkappaB protein expression levels were significantly increased. The TNF-α and IL-6 expression showed a downward trend when the progesterone concentration increased, and there were significant differences among all of the groups (P<0.05). It was suggested that progesterone can inhibit the TLR4-MyD88-dependent signaling pathway in PE significantly and benefit for the pregnancy.
RESUMO
The role of progesterone in the Toll-like receptor 4 (TLR4)-MyD88-dependent signaling pathway in pre-eclampsia was studied. Peripheral blood mononuclear cells (PBMCs) from pre-eclampsia (PE) patients were subjected to primary culture, and stimulated with different concentrations of progesterone (0, 10(-8), 10(-6), and 10(-4) mol/L). The mRNA expression of TLR4, MyD88 and nuclear factor-kappaB (NF-κB) was detected by using real-time PCR. The Ikappa-B protein expression was detected by using Western blotting. The expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the supernatant was determined by using ELISA. With the concentrations of progesterone increasing, the mRNA expression levels of TLR4, MyD88 and NF-κB in 2(-ΔΔCT) value were significantly decreased, and the IkappaB protein expression levels were significantly increased. The TNF-α and IL-6 expression showed a downward trend when the progesterone concentration increased, and there were significant differences among all of the groups (P<0.05). It was suggested that progesterone can inhibit the TLR4-MyD88-dependent signaling pathway in PE significantly and benefit for the pregnancy.
