Highly stable lanthanide-doped CsPbI3 perovskite nanocrystals with near-unity quantum yield for efficient red light-emitting diodes.

CsPbI3 perovskite nanocrystals (NCs) are gaining popularity as promising photoactive materials for optoelectronic devices. However, their poor phase stability has caused substantial limitations in their practical application. Herein, the small-sized rare earth La cation is strategically introduced to fundamentally improve the NC phase stability against the environment, heat, and UV radiation by the partial substitution of Pb ions to suppress structural distortion and increase the formation energy. The strong interaction between La and I of the octahedra has been demonstrated to enable the effective suppression of the trap states, which promotes strengthened radiative recombination for a near-unity photoluminescence quantum yield (PLQY) of 99.3%. High energy bands have also been found for the La-doped NCs to narrow down the energy barrier for efficient hole injection. The superior optoelectronic properties of La-doped NCs promote great improvements in the perovskite light-emitting diode (PeLED) performances with a 5-fold improvement in external quantum efficiency (EQE) from 1.19 to 6.01% and 2-fold longer lifetime from 1451 to 2956 s. This work provides an effective method for small-sized metal ion-doped CsPbI3 NCs to realize high emission efficiency and phase stabilization for efficient PeLEDs.

Highly Stable SnO2-Based Quantum-Dot Light-Emitting Diodes with the Conventional Device Structure.

ZnO-based electron-transporting layers (ETLs) have been universally used in quantum-dot light-emitting diodes (QLEDs) for high performance. The active surface chemistry of ZnO nanoparticles (NPs), however, leads to QLEDs with positive aging and unacceptably poor shelf stability. SnO2 is a promising candidate for ETLs with less reactivity, but NP agglomeration in nonionic solvents makes the conventional device structure abandoned, resulting in QLEDs with extremely low operational lifetimes. The large barrier for electron injection also limits the electroluminescence efficiency. Here, we report one solution to all the above-mentioned problems. Owing to the strong HO-SnO2 coordination and the steric effect provided by the hydrocarbon groups, tetramethylammonium hydroxide can stabilize SnO2 NPs in alcohol, while its intrinsic dipole induces a favorable electronic-level shift for charge injection. The SnO2-based devices, with the conventional structure, exhibit not only the most efficient electroluminescence among ZnO-free QLEDs but also an operational lifetime (T95) over 3200 h at 1000 cd m-2, which is comparable with that of state-of-the-art ZnO-based devices. More importantly, the superior shelf stability means that the TMAH-SnO2 NPs are promising to enable QLEDs with real stability.

Highly Emissive Quasi-2D Perovskites Enabled by a Multifunctional Molecule for Bright Light-Emitting Diodes.

Quasi-two-dimensional (quasi-2D) perovskite has exhibited great potential to be an ideal luminescent material for perovskite light-emitting diodes (PeLEDs). However, the low-order phases (especially n = 1 phase) and the inevitable defects result in massive nonradiative recombination and poor emission efficiency. Herein, a multifunctional molecule of tetrabutylammonium dihydrogen phosphate (TDP) is introduced to simultaneously suppress the low-n phase, passivate the defects, and increase the exciton binding energy of the quasi-2D perovskite for massive radiative recombination and thus high emission efficiency. The multifunctional roles of TDP are realized by the synergistic effects of tetrabutylammonium cation and dihydrogen phosphate anion, both of which show strong interaction with the lead bromide octahedron of the perovskite. As a result, the TDP-incorporated perovskite films show a great enhancement of the emission efficiency with a remarkable increase in photoluminescence quantum yield (PLQY) from 34.6 to 96.9% at the wavelength of 522 nm. The strengthened radiative recombination promotes efficient emission efficiency with over 2.5-fold improvement in external quantum efficiency (EQE) and current efficiency (CE) from 3.27% and 10.83 cd A-1 to 9.25% and 28.35 cd A-1, respectively, as well as high brightness with over 37% enhancement from 12713 to 17536 cd m-2. Consequently, this work contributes to an efficient approach to employ a multifunctional molecule for highly emissive quasi-2D perovskites and enhanced quasi-2D PeLED performances.

Ultra-Thermostability of Spatially Confined and Fully Protected Perovskite Nanocrystals by In Situ Crystallization.

Although all-inorganic perovskite materials present multiple fascinating optical properties, their poor stability undermines their potential application in the field of multi-color display. Herein, spatially confined CsPbBr3 nanocrystals are in situ crystallized within uniform mesoporous SiO2 nanospheres (MSNs) to regulate their size distribution, passivate their surface defects, shield them from water/oxygen, and more importantly, enhance their thermotolerance. As a result, the remnant PL intensity of the prepared spatially confined perovskite (CsPbBr3 ) nanocrystals by in situ crystallization within uniform mesoporous SiO2 nanospheres (SCP@MSNs) powders can be maintained over 98% of its initial value even after being immersed in harsh conditions (0.1 m HCl or 0.1 m NaOH) for 60 days. Furthermore, the prepared SCP@MSNs-PDMS film demonstrates astonishing thermostability by maintaining almost consistent room temperature PL intensities after continuous heating-cooling cycles between 200 and 25 °C, which would greatly improve its processability during potential industrial manufacturing. The fabricated LCD backlit based on SCP@MSNs covers 124% of NTSC standard and 95.6% of Rec. 2020 standard, indicating its great potential in practical display field.

Effect of honokiol on exotoxin proteins listeriolysin O and p60 secreted by Listeria monocytogenes.

Listeria monocytogenes is considered one of the most important foodborne pathogens. The virulence-related proteins listeriolysin O (LLO) and p60 are critical factors involved in Listeria pathogenesis. In the present study, we investigated the effect of honokiol on LLO and p60 secreted from L. monocytogenes. A listeriolysin assay was used to investigate the haemolytic activities of L. monocytogenes exposed to honokiol, and the secretion of LLO and p60 was detected by immunoblot analysis. Additionally, the influence of honokiol on the transcription of LLO and p60 genes (hly and iap, respectively) was analysed by real-time reverse transcription PCR. TNF-α release assays were performed to elucidate the biological relevance of changes in LLO and p60 secretion induced by honokiol. According to the data, honokiol showed good anti-L. monocytogenes activity, with MICs of 8-16 µg ml(-1), and the secretion of LLO and p60 was decreased by honokiol. In addition, the transcription of hly and iap was inhibited by honokiol. Our results indicate that TNF-α production by RAW264.7 cells stimulated with L. monocytogenes supernatants was inhibited by honokiol. Based on these data, we propose that honokiol could be used as a promising natural compound against L. monocytogenes and its virulence factors.

[Prevalence of nutritional risk among in-patients with liver diseases in Beijing, China].

OBJECTIVE: To investigate the prevalence of nutritional risk and malnutrition among in-patients with liver diseases in Beijing, China, and to evaluate the relationship between nutritional risk and prognosis. METHODS: A total of 331 in-patients with liver diseases under care at the Artificial Liver Center of Beijing Youan Hospital were consecutively enrolled for study between April 2012 and December 2012. Nutritional status was determined by calculating each patient's ratio of real weight to clinically ideal weight, the triceps skin fold (TSF), and the mid-upper arm muscle circumference (MAMC). Nutritional risk was estimated using the Nutritional Risk Screening questionnaire 2002 (NRS-2002). In addition, each patient's Child-Pugh stage, body mass index (BMI), power of gripping, serum albumin and pre-albumin levels, lymphocyte count, hospital length of stay, complications, alcoholism history, and outcome after discharge were recorded for analysis. RESULTS: One-hundred-and-thirteen of the patients (34.1%) were defined as at nutritional risk upon hospital admission. The ratio of nutritional risk was lowest in patients with chronic hepatitis (17.0%) and highest in patients with acute on chronic liver failure (56.5%). The ratios of malnutrition evaluated by TSF and MAMC were 36.9% and 38.7%, respectively. Among the patients with liver cirrhosis or hepatocellular carcinoma, the ratio of Child-Pugh stage C was higher for individuals defined as at nutritional risk than for those without. When TSF-based ratio of malnutrition was higher for individuals with a history of alcoholism than for those without. BMI, power of gripping, serum albumin level, serum pre-albumin level, and lymphocyte count were all lower for individuals defined as at nutritional risk than for those without. Hospital stay, ratio of complication onset, and ratio of death were all higher for individuals defined as at nutritional risk than for those without. CONCLUSION: TSF and MAMC can be used to evaluate the nutritional status of in-patients with liver diseases. Patients with nutritional risk (as determined by the NRS-2002) have poorer prognosis and may benefit from nutritional intervention.