Inhibition of ion diffusion/migration in perovskite p-n homojunction by polyetheramine insert layer to enhance stability of perovskite solar cells with p-n homojunction structure.

Perovskite p-n homojunctions (PHJ) have been confirmed to play a crucial role in facilitating carrier separation/extraction in the perovskite absorption layer and provide an additional built-in potential, which benefits the inhibition of carrier recombination in perovskite solar cells (PSCs) and ultimately improves device performance. However, the diffusion and migration of ions between n-type and p-type perovskite films, particularly under operational and heating conditions, lead to the degradation of PHJ structures and limit the long-term stability of PSCs with PHJ structure (denoted as PHJ-PSCs). In this study, we propose an insert layer strategy by directly introducing an ultra-thin polyetheramine (PEA) layer between the n-type and p-type perovskite films to address those challenges arising from ion movements. Femtosecond transient absorption (fs-TAS) and photoluminescence (PL) measurements demonstrate that the PHJ (without and with the insert layer) enhances carrier separation/extraction compared to the single n-type perovskite film. Monitoring the evolution of bromine element distribution reveals that the insert layer can efficiently suppress ion diffusion between perovskite films, even under long-term illumination and heating conditions. Consequently, an efficiency of 23.53% with excellent long-term operational stability is achieved in the optimized PHJ-PSC with the insert layer.

All-fiber high-power supercontinuum laser source over 3.5 µm based on a germania-core fiber.

In this Letter, a high-power all-fiber mid-infrared (MIR) supercontinuum (SC) laser source based on 9 cm long germania-core fiber (GCF) pumped by a high-power thulium-doped fiber amplifier is presented. As the pump power was set as 60 W, we obtained a 21.34 W broadband SC source extending from 1742 to 3512 nm with a slope efficiency of 32.5%. The 10 dB spectral bandwidth was over 1000 nm, spanning 1.97 to 3.04 µm. Furthermore, the numerical simulation of SC generation in GCF was in good agreement with the experimental results. As far as we know, this is the highest average output power over 3.5 µm in GCF based on a MIR SC laser source.

Circadian variations in behaviors, BDNF and cell proliferation in depressive mice.

Neurotrophic factors are well-known to be involved in the pathophysiology of depression and treatment of antidepressants. Brain-derived neurotrophic factor (BDNF), one of the most widely distributed and the most highly studied neurotrophic factors, has been demonstrated to play an important role in the pathophysiology of depression and the mechanism of antidepressants. According to the previous studies, we found that animal tissues were dissected for BDNF measurement mainly in daytime. Considering the circadian rhythm of BDNF expression, our present study evaluated the circadian variations in behaviors, serum corticosterone concentrations, hippocampal BDNF expression and neuronal cell proliferation in mice exposed to chronic mild stress (CMS), one of the most widely used depression-like animal models. Our results provided the first evidence that the difference of BDNF expression and neuronal cell proliferation between CMS and control mice underwent an oscillation related to the circadian variations (maximum at 20:00 h, minimum at 12:00 h or 16:00 h), while the difference of sucrose preference and first feeding latency was not affected by circadian rhythm. This oscillation difference was attributed to the relative constant BDNF expression and cell proliferation in CMS mice and the fluctuating BDNF expression and cell proliferation in control mice. CMS exposure might destroy the circadian rhythm of BDNF expression and cell proliferation in hippocampus of normal individual. Our present study suggests that animal decapitation at 20:00 h is the best time for BDNF-related measurement in CMS experiment, since the difference reaches the maximum.

Preparation of poly(L-lactic acid) nanofiber scaffolds with a rough surface by phase inversion using supercritical carbon dioxide.

Phase inversion using supercritical carbon dioxide (SC-CO2) has been widely used in the development of tissue engineering scaffolds, and particular attention has been given to obtaining desired morphology without additional post-treatments. However, the main challenge of this technique is the difficulty in generating a three-dimensional (3D) nanofiber structure with a rough surface in one step. Here, a poly(L-lactic acid) (PLLA) 3D nanofiber scaffold with a rough surface is obtained via phase inversion using SC-CO2 by carefully choosing fabrication conditions and porogens. It is found that this method can effectively modulate the structure morphology, promote the crystallization process of semicrystalline polymer, and induce the formation of rough structures on the surface of nanofibers. Meanwhile, the porogen of ammonium bicarbonate (AB) can produce a 3D structure with large pores, and porogen of menthol can improve the interconnectivity between the micropores of nanofibers. A significant increase in the fiber diameter is observed as the menthol content increases. Furthermore, the menthol may affect the mutual transition between the α' and α crystals of PLLA during the phase separation process. In addition, the results of protein adsorption, cell adhesion, and proliferation assays indicate that cells tend to have higher viability on the nanofiber scaffold. This process combines the characteristic properties of SC-CO2 and the solubility of menthol to tailor the morphology of polymeric scaffolds, which may have potential applications in tissue engineering.

Hippocampal BDNF signaling restored with chronic asiaticoside treatment in depression-like mice.

Brain-derived neurotrophic factor (BDNF) plays a key role in the regulation of depression in the brain. Recently, increasing studies have focused on the antidepressant-like mechanism of BDNF and its downstream signaling pathway. A previous study has shown that asiaticoside produced an antidepressant-like action in the mouse tail suspension test and forced swimming test. However, the neurotrophic mechanism that is affected by asiaticoside is unclear. Our present study aimed to verify whether asiaticoside produces an antidepressant-like effect through the activation of BDNF signaling in chronic unpredictable mild stress (CUMS). The results showed that mice treated with asiaticoside for four weeks reversed the decreased sucrose preference and increased immobility time that was observed in CUMS mice. In addition, we found that asiaticoside up-regulated BDNF, PSD-95 and synapsin I expression only in the hippocampus but not in the frontal cortex in both non-stressed and CUMS mice. However, K252a, an inhibitor of BDNF receptor tropomyosin-related kinase receptor B (TrkB), completely abolished the antidepressant-like effect of asiaticoside. Moreover, the expression of hippocampal BDNF, PSD-95 and synapsin I that had increased with asiaticoside also declined with K252a pretreatment. In conclusion, our study implies that it is possible that asiaticoside exerts its antidepressant-like action by activating BDNF signaling in the hippocampus.