POE enhanced stabilities of CsPbX_(3)(X=Br,Ⅰ)perovskite and their white LED application

Perovskite has received extensive attention due to its excellent properties, just like photoelectric, while the instability has always troubled us to the wide application of perovskite materials. Herein, we proposed to use SiO_(2)and POE to encapsulate perovskite nanocrystals(PNCs). In this work, we have successfully prepared a series of perovskite composite materials and films with different concentration ratios.Due to the protection of POE, the luminous intensity of CsPbBr_(3)@POE composite film remained above 90% after stayed in the water for 42 days. The lead concentration of CsPbBr_(3)@POE composite film was 0.8 μg/m L after 48 h of immersing in deionized water. Namely, packaging PNCs in POE could effectively prevent Pb from overflowing reduce Pb pollution. Besides, the composite films showed a wide colour gamut with 117% of NTSC colour gamut, which shows that this composite material has a development prospect in the WLED field.

A statistical learning approach for stock selection in the Chinese stock market

Forecasting stock returns is extremely challenging in general,and this task becomes even more difficult given the turbulent nature of the Chinese stock market.We address the stock selection process as a statistical learning problem and build crosssectional forecast models to select individual stocks in the Shanghai Composite Index.Decile portfolios are formed according to rankings of the forecasted future cumulative returns.The equity market’s neutral portfolio-formed by buying the top decile portfolio and selling short the bottom decile portfolio-exhibits superior performance to,and a low correlation with,the Shanghai Composite Index.To make our strategy more useful to practitioners,we evaluate the proposed stock selection strategy’s performance by allowing only long positions,and by investing only in Ashare stocks to incorporate the restrictions in the Chinese stock market.The longonly strategies still generate robust and superior performance compared to the Shanghai Composite Index.A close examination of the coefficients of the features provides more insights into the changes in market dynamics from period to period.

Environmentally persistent free radicals in PM_(2.5)from a typical Chinese industrial city during COVID-19 lockdown:The unexpected contamination level variation

The outbreak of COVID-19 has caused concerns globally.To reduce the rapid transmission of the virus,strict city lockdown measures were conducted in different regions.China is the country that takes the earliest home-based quarantine for people.Although normal industrial and social activities were suspended,the spread of virus was efficiently controlled.Simultaneously,another merit of the city lockdown measure was noticed,which is the improvement of the air quality.Contamination levels of multiple atmospheric pollutants were decreased.However,in this work,24 and 14 air fine particulate matter(PM_(2.5))samples were continuously collected before and during COVID-19 city lockdown in Linfen(a typical heavy industrial city in China),and intriguingly,the unreduced concentration was found for environmentally persistent free radicals(EPFRs)in PM_(2.5)after normal life suspension.The primary non-stopped coal combustion source and secondary Cu-related atmospheric reaction may have impacts on this phenomenon.The cigarette-based assessment model also indicated possible exposure risks of PM_(2.5)-bound EPFRs during lockdown of Linfen.This study revealed not all the contaminants in the atmosphere had an apparent concentration decrease during city lockdown,suggesting the pollutants with complicated sources and formation mechanisms,like EPFRs in PM_(2.5),still should not be ignored.

光催化产过氧化氢材料

过氧化氢(H2O2)是一种很有潜力的能量载体,且作为一种环保型氧化剂广泛运用于有机合成、饮用水处理、废水处理等工业和医疗卫生领域。随着对环境保护要求的提升,预计H2O2的需求量将大幅增加。传统的蒽醌法(AQ)制备H2O2的工艺流程繁琐和存在有机物污染环境的现象。以O2和H2O为原料、太阳能为能源、半导体为光催化剂的光催化生产H2O2是一个绿色化学过程,具有反应条件温和、操作简单可控和无二次污染等优点。近年来,光催化产H2O2引起了人们的广泛关注。本综述介绍了光催化产H2O2的机理和效率低的原因,重点论述了光催化生成H2O2的体系以及提高光催化产H2O2的策略,最后对光催化产H2O2未来的发展方向进行了展望。

Robust YAG:Ce single crystal for ultra-high efficiency laser lighting

At present,solid-state laser-driven lighting fabricated with blue laser diode(LD)and phosphor has been greatly developed in high-power lighting applications.The major obstacle is the luminescence saturation threshold of the fluorescence conversion material(YAG:Ce).In this work,we successfully prepared a series of high-quality and robust YAG:Ce single crystals.With high quantum efficiency(QE=92%),regular crystal structure and high thermal conductivity,the single-crystal has excellent ability to deal with high radiation flux and thermal accumulation generated by high power.Matching the single-crystal with the laser,the luminous efficiency up to 274 lm/W and saturation threshold of 12 W/mm^(2) were obtained.In addition,the influence of Ce doping concentration and sample processing conditions on the indicators in laser-driven white lighting was systematically studied.The results are of great significance and are believed to promote the development of solid-state laser-driven lighting.

Ultrastable Gd^(3+)doped CsPbCl_(1.5)Br_(1.5) nanocrystals blue glass for regulated and low thresholds amplified spontaneous emission

Here,Gd-doped CsPbCl_(1.5)Br_(1.5) nanocrystals(NCs)in borosilicate glass matrix(B_(2)O_(3)−SiO_(2)−ZnO)were prepared by melting quenching and in-situ crystallization.The optical performance of CsPbCl_(1.5)Br_(1.5) NCs glasses under different heat-treatment temperatures and the content of Gd^(3+) were analyzed in detail.After CsPbCl_(1.5)Br_(1.5) NCs glass is doped with Gd^(3+)ions,the photoluminescence intensity increases and the synthesized Gd-doped CsPbCl_(1.5)Br_(1.5) NCs glasses have excellent water stability and thermal cycling performance.In addition,the influence of Gd-doped concentrations and heat-treatment temperatures on the amplified spontaneous emission(ASE)thresholds of CsPbCl_(1.5)Br_(1.5) NCs glasses was studied,and the Gd-doped CsPbCl_(1.5)Br_(1.5) NCs glasses achieve controllable ASE thresholds at room temperature.The ASE threshold can be as low as 0.39 mJ∕cm^(2).This work offers a neoteric reference for the research in the application of metal ion-doped perovskite NCs and a new idea for the realization of controllable and low ASE thresholds on perovskite NCs.