Enhancing photoluminescence quantum efficiency of metal halide perovskites by examining luminescence-limiting factors

Metal halide perovskites (MHPs) show superior optoelectronic properties, which give them the great potential for use in next generation light-emitting diodes (LEDs). In particular, their narrow emission linewidths can achieve ultrahigh color purity. However, the reported luminescence efficiency (LE) values are not high enough to be commercialized in displays and solid-state lightings. Moreover, the operational stability of LEDs associated with the overshooting of luminance and the high relative standard deviation of reported external quantum efficiencies are still problematic. In this perspective, we review photophysical factors that limit the photoluminescence quantum efficiency of perovskite-based LEDs. These factors are categorized into (i) weak exciton binding, (ii) nonradiative recombinations, (iii) slow cooling of long-lived hot carriers, (iv) deep-level defects, and (v) interband transition rates. We then present various physicochemical methods to effectively overcome these luminescence-limiting factors. We finally suggest some useful research directions to further improve the LE of MHP emitters as core components in displays and solid-state lightings.

Electron−hole separation in ferroelectric oxides for efficient photovoltaic responses

Despite their potential to exceed the theoretical Shockley−Queisser limit, ferroelectric photovoltaics (FPVs) have performed inefficiently due to their extremely low photocurrents. Incorporating Bi₂FeCrO₆(BFCO) as the light absorber in FPVs has recently led to impressively high and record photocurrents [Nechache R, et al. (2015) Nat Photonics 9:61–67], which has revived the FPV field. However, our understanding of this remarkable phenomenon is far from satisfactory. Here, we use first-principles calculations to determine that such excellent performance mainly lies in the efficient separation of electron− hole (e-h) pairs. We show that photoexcited electrons and holes in BFCO are spatially separated on the Fe and Cr sites, respectively. This separation is much more pronounced in disordered BFCO phases, which adequately explains the observed exceptional PV responses. We further establish a design strategy to discover next-generation FPV materials. By exploring 44 additional Bi-based double-perovskite oxides, we suggest five active-layer materials that offer a combination of strong e-h separations and visible-light absorptions for FPV applications. Our work indicates that charge separation is the most important issue to be addressed for FPVs to compete with conventional devices. Keywords: ferroelectrics; double perovskites; photovoltaics; e-h separation; density functional theor

Thrap3 promotes R-loop resolution via interaction with methylated DDX5

Transcription-replication conflicts lead to DNA damage and genomic instability, which are closely related to human diseases. A major source of these conflicts is the formation of R-loops, which consist of an RNA-DNA hybrid and a displaced single-stranded DNA. Although these structures have been studied, many aspects of R-loop biology and R-loop-mediated genome instability remain unclear. Here, we demonstrate that thyroid hormone receptor-associated protein 3 (Thrap3) plays a critical role in regulating R-loop resolution. In cancer cells, Thrap3 interacts with DEAD-box helicase 5 (DDX5) and localizes to R-loops. Arginine-mediated methylation of DDX5 is required for its interaction with Thrap3, and the Thrap3-DDX5 axis induces the recruitment of 5'-3' exoribonuclease 2 (XRN2) into R-loops. Loss of Thrap3 increases R-loop accumulation and DNA damage. These findings suggest that Thrap3 mediates resistance to cell death by preventing R-loop accumulation in cancer cells. Cancer: DNA damage associated with nucleic acid loops A nuclear protein appears to inhibit cancer cell death by preventing the accumulation of nucleic acid structures called R-loops. R-loops are by-products of transcription, comprising two misaligned DNA strands and one RNA strand. They are involved in gene expression, but also threaten genome integrity and have been linked to the onset of neurodegeneration and cancers. A team led by Jang Hyun Choi and Hyug Moo Kwon, Ulsan National Institute of Science and Technology, South Korea, explored the role of Thrap3, a nuclear protein involved in RNA splicing, in R-loop-associated DNA damage. They found that Thrap3 binds to an enzyme essential for resolving R-loops. When the team suppressed Thrap3 expression, they saw an increase in R-loops in both normal and cancer cells. This R-loop accumulation significantly inhibited the growth of breast cancer cells

Anti-proliferative effects of Bifidobacterium adolescentis SPM0212 extract on human colon cancer cell lines

<p>Abstract</p> <p>Background</p> <p>Lactic acid bacteria (LAB) are beneficial probiotic organisms that contribute to improved nutrition, microbial balance, and immuno-enhancement of the intestinal tract, as well as anti-tumor activity. The aim of the present work was to study the growth inhibition of tumor cells by butanol extract of <it>Bifidobacterium adolescentis </it>isolated from healthy young Koreans.</p> <p>Methods</p> <p>The anti-proliferative activity of <it>B. adolescentis </it>isolates was assessed by XTT assays on three human colon cancer cell lines (Caco-2, HT-29, and SW480). The effects of <it>B. adolescentis </it>SPM0212 butanol extract on tumor necrosis factor-α (TNF-α) and nitric oxide (NO) production were tested using the murine macrophage RAW 264.7 cell line.</p> <p>Results</p> <p>The butanol extract of <it>B. adolescentis </it>SPM0212 dose-dependently inhibited the growth of Caco-2, HT-29, and SW480 cells by 70%, 30%, and 40%, respectively, at 200 μg/mL. Additionally, the butanol extract of <it>B. adolescentis </it>SPM0212 induced macrophage activation and significantly increased the production of TNF-α and NO, which regulate immune modulation and are cytotoxic to tumor cells.</p> <p>Conclusion</p> <p>The butanol extract of <it>B. adolescentis </it>SPM0212 increased activity of the host immune system and may improve human health by helping to prevent colon cancer as a biological response modifier.</p

Cell-free synthesis of functional phospholipase A1 from Serratia sp.

Additional file 1: Figure S1 Gas chromatography analysis of sesame oil incubated with cell-free synthesized PLA1