Very Stable and Efficient Tandem Quantum-Dot Light-Emitting Diodes Enabled by IZO-Based Interconnecting Layers.

Theoretically, tandem quantum-dot light-emitting diodes (QLEDs) hold great promise for achieving both high efficiency and high stability in display applications. However, in practice, their operational stability remains considerably inferior to that of state-of-the-art devices. In this study, we developed a new tandem structure with optimal electrical and optical performance to simultaneously improve the efficiency and stability of tandem QLEDs. Electrically, upon development of a barrier-free interconnecting layer enabled by an indium-zinc oxide bridging layer and a conductive ZnMgO layer, the driving voltage of the tandem QLEDs is remarkably reduced. Optically, upon development of a top-emitting structure and optimization of the cavity length guided by a theoretical simulation, a maximum light extraction efficiency is achieved. As a result, the red tandem QLEDs exhibit a maximum external quantum efficiency of 49.01% and a T95 lifetime at 1000 cd/m2 of >50 000 h, making them one of the most efficient and stable QLEDs ever reported.

Enhancing the Performance of Perovskite Light-Emitting Diodes via Synergistic Effect of Defect Passivation and Dielectric Screening.

Metal halide perovskites, particularly the quasi-two-dimensional perovskite subclass, have exhibited considerable potential for next-generation electroluminescent materials for lighting and display. Nevertheless, the presence of defects within these perovskites has a substantial influence on the emission efficiency and durability of the devices. In this study, we revealed a synergistic passivation mechanism on perovskite films by using a dual-functional compound of potassium bromide. The dual functional potassium bromide on the one hand can passivate the defects of halide vacancies with bromine anions and, on the other hand, can screen the charged defects at the grain boundaries with potassium cations. This approach effectively reduces the probability of carriers quenching resulting from charged defects capture and consequently enhances the radiative recombination efficiency of perovskite thin films, leading to a significant enhancement of photoluminescence quantum yield to near-unity values (95%). Meanwhile, the potassium bromide treatment promoted the growth of homogeneous and smooth film, facilitating the charge carrier injection in the devices. Consequently, the perovskite light-emitting diodes based on this strategy achieve a maximum external quantum efficiency of ~ 21% and maximum luminance of ~ 60,000 cd m-2. This work provides a deeper insight into the passivation mechanism of ionic compound additives in perovskite with the solution method.

Two-dimensional lateral anatase-rutile TiO2 phase junctions with oxygen vacancies for robust photoelectrochemical water splitting.

Exploiting the photoelectrode materials with broad solar light response, high-efficient separation of photogenerated charges and abundant active sites is extremely vital yet enormously challenging. Herein, an innovative two-dimensional (2D) lateral anatase-rutile TiO2 phase junctions with controllable oxygen vacancies perpendicularly aligned on Ti mesh is presented. Our experimental observations and theoretical calculations corroborate explicitly that the 2D lateral phase junctions together with three-dimensional arrays not only exhibit the high-efficient photogenerated charges separation guaranteed by the build-in electric field at the side-to-side interface, but also furnish enriching active sites. Moreover, the interfacial oxygen vacancies generate new defect energy levels and serve as electron donors, hence extending visible light response and further accelerating the separation and transfer of photogenerated charges. Profiting from these merits, the optimized photoelectrode yield a pronounced photocurrent density of 1.2 mA/cm2 at 1.23 V vs. RHE with Faradic efficiency of 100%, which is approximately 2.4 times larger than that of pristine 2D TiO2 nanosheets. Furthermore, the incident photon to current conversion efficiency (IPCE) of the optimized photoelectrode is also boosted within both ultraviolet and visible light regions. This research is envisioned deliver the new insight in developing the novel 2D lateral phase junctions for PEC applications.

Engineering Plasmon-Enhanced Fluorescent Gold Nanoclusters Using Bovine Serum Albumin as a Novel Separation Layer for Improved Selectivity.

The combination of gold nanoclusters (AuNCs) with surface plasmonic metal nanomaterials is an effective and direct method to improve the photoluminescence efficiency of AuNCs. However, the plasmon-enhanced AuNC luminescence strategies usually utilize silica as the separation layer, which requires further functionalization because the silica layer has no functional groups for in situ bonding of AuNCs. Therefore, it appears as a crucial need to develop an appropriate separation layer for the preparation of plasmon-enhanced AuNC luminescent nanomaterials. In this work, employing bovine serum albumin (BSA) as a novel separation layer, we prepared gold nanoparticles (AuNPs)@BSA@Au35NCs by a controllable and in situ synthesis method. BSA can form a BSA layer on the surface of AuNPs through Au-S bonds. Meanwhile, BSA can reduce AuCl4- ions to generate Au35NCs. In comparison with pure BSA-AuNCs, the quantum yield of the AuNPs@BSA@Au35NCs was increased by nearly 7 times as a result of plasmonic coupling, and the time of in situ synthesis of Au35NCs was shortened by 8 h. More importantly, the preparation of the BSA layer was simple and time-saving without functionalization, in contrast to the previously reported silica layer. Moreover, the simulation calculation of different dimensions determined the optimal binding sites between Au35NCs and BSA, confirming that BSA can be an effective spatial spacer. Finally, it was found that the BSA layer between AuNPs and AuNCs can improve the specificity of AuNCs toward H2S, which is extremely difficult for pure BSA@AuNCs.

Influence of Light-Matter Interaction on Efficiency of Quantum-Dot Light-Emitting Diodes.

Light-matter interaction can affect the radiative decay rate of excitons and thus the emission quantum yield (QY) of quantum dots (QDs). In this work, light-matter interaction and outcoupling efficiency of QD light-emitting diodes with different structures are investigated experimentally and theoretically. We show that the external quantum efficiency (EQE) of top-emitting devices is higher than that of the bottom-emitting devices, which is mainly due to the stronger light-matter interaction and higher light outcoupling efficiency of the top-emitting structures. In addition, we show that the QY enhancement induced by light-matter interaction is more significant for low-QY QDs. Our results suggest that top-emitting structures are more powerful for improving the EQE of devices built with low-QY QDs.

Preparation, characterization and cell labelling of strong pH-controlled bicolor fluorescence carbonized polymer dots.

As a class of important carbon nanomaterial, carbonized polymer dots (CPDs), also called carbon dots (CDs), have aroused wide interest owing to their unique water solubility, fluorescence properties, and rich surface functional groups. However, the directional tuning of the fluorescence properties of CPDs remains incomplete because of the influence of many factors like diameter, solvent and surface groups. Particularly, most carbonized polymer dots are synthesized in a neutral pH environment. Herein, by modulating the pH (strongly acidic or alkaline) of dextrin water solution, bicolor fluorescence emission (blue and yellow) CPDs were prepared by a hydrothermal reaction. Through systematic characterization, it was found that the different fluorescence properties are regulated by the diameters and surface groups of the carbon cores. Simultaneously, the pH value affected the nucleation process. Based on the excellent fluorescence properties, cell fluorescence imaging and cytotoxicity were tested. The bicolor fluorescence CPDs obtained by tuning the pH provide an important theoretical basis for the design of broadband CPDs.

Ultrafast synthesized monometallic nanohybrids as an efficient quencher and recognition antenna of upconversion nanoparticles for the detection of xanthine with enhanced sensitivity and selectivity.

Upconversion nanoparticles (UCNPs) have shown great promise in bioanalytical applications owing to their excellent optical properties. Generally, most analytical applications are based on the fluorescence resonance energy transfer (FRET) principle to quench the fluorescence of UCNPs. However, each UCNP contains thousands of emission center ions, and most of them exceed the FRET critical distance, which hinders FRET efficiency and leads to a low signal-to-background ratio (SBR). Herein, a novel nanoprobe for the detection of Xanthine (XA) based on inner filter effects (IFE) and cascade signal amplification strategy was constructed by decorating UCNP with trypsin-chymotrypsin-stabilized gold nanoparticles-gold nanoclusters (Try-chy-AuNPs-AuNCs) monometallic nanohybrids. The Try-chy-AuNPs-AuNCs prepared by ultrafast (3 min) and green synthesis method have efficient upconversion fluorescence quenching ability (the quenching efficiency up to 90.9%), which can effectively improve the SBR of the probe, so as to improve the sensitivity. In addition, the Try-chy-AuNPs-AuNCs have a unique spatial structure, which can effectively prevent the interaction between large-size biothiol (glutathione) and the probe, thus improving its selectivity. Besides, combined with the excellent optical performance of UCNPs and cascaded signal amplification strategy, the sensitivity of the probe can be further improved. Under the optimized conditions, the linear response range of the probe was obtained from 0.05 to 50 µM, 0.06-80 µM and with the low detection limit of 22.6 nM and 26.3 nM for H2O2 and XA, respectively. Meanwhile, the developed method has been further applied to the detection of XA in human serum with satisfactory results.

A novel ratiometric fluorescent probe from a hemicyanine derivative for detecting NAD(P)H in a cell microenvironment.

In this paper, a fluorescent compound derived from coumarin and hemicyanine was synthesized and characterized. Herein, we present the fluorescence properties of the probe. Fluorescence selectivity experiments revealed that it exhibited higher ratiometric fluorescence response activity toward NAD(P)H than other commonly coexisting compounds in the cell microenvironment, in accord with the fluorescence shift from red to blue. In addition, the fluorescence identification mechanism was deduced to be a redox reaction between the sensor and NAD(P)H according to the fluorescence behavior. The ratiometric fluorescent probe provided an important theoretical basis for sensing NAD(P)H in vitro and in vivo. We also used this phenomenon to build a sensitive detection platform of NAD(P)H-dependent enzyme activity based on the fluorescence method.

The study of hydrothermal liquefaction of corn straw with Nano ferrite + inorganic base catalyst system at low temperature.

Hydrothermal liquefaction of corn straw with different catalytic systems and temperatures were investigated in this study. Results showed dual catalytic system can effectively promote the degradation of corn straw at low temperature. With increase of temperature, aqueous phase increased and straw residue decreased for all catalytic systems. The heavy bio-oil yield increased with the increasing of temperature for single catalytic system, while the trend was opposite for dual catalytic system. In single catalytic system, ZnFe2O4 was more suitable for preparation of heavy bio-oil, and the maximum yield reached 34.02 wt% at 180 °C. The proportion of monophenyl compounds in heavy bio-oil for dual catalytic system reached the maximum of 84% at 220 °C with ZnFe2O4. At 180 °C, the contents of Benzofuran,2,3-dihydro and 2-Methoxy-4-vinylphenol reached the maximum of 31.42% and 17.64% in CoFe2O4 catalyst system, and the maximum yield of Vanillin was 10.82% with ZnFe2O4.

Synergistic hydrothermal liquefaction of wheat stalk with homogeneous and heterogeneous catalyst at low temperature.

The effect of Na2CO3, Fe and Na2CO3 + Fe during hydrothermal liquefaction (HTL) of wheat stalk with different temperature and reaction time was investigated in this study. The results indicated that Na2CO3 + Fe can promote the cracking of wheat stalk compared with Na2CO3 or Fe. Meanwhile, higher temperature favored the decomposition of wheat stalk and formation of heavy bio-oil. The highest heavy bio-oil yield was 24.25 wt% and the maximum liquefaction conversion rate was 89.45 wt% in system of Na2CO3 + Fe at 270 °C. The analysis results indicated that longer reaction time could promote liquefaction conversion especially for heavy bio-oil with Na2CO3 + Fe during the process of HTL. GC-MS, UPLC-MS and FT-IR analysis indicated that the major organic compounds in heavy bio-oil were aromatic compounds, alcohols, ketones, alkanes, and aldehydes, among of them aromatic compounds were the most prevalent.

Trichoderma harzianum mitigates salt stress in cucumber via multiple responses.

Trichoderma harzianum T-soybean plays an important role in controlling soybean root rot disease. However, the mechanism by which it improves plant tolerance to salt stress is not clear. In this study, we investigated the possible mechanism of T-soybean in mitigating the damage caused by salt stress in Cucumis sativus L plants. Our results suggest that T-soybean improved salt tolerance of cucumber seedlings by affecting the antioxidant enzymes including peroxidase (POD) (EC 1.11.1.6), polyphenol oxidase (PPO) (EC 1.14.18.1), phenylalanine ammonia-lyase (PAL) (EC 4.3.1.5), catalase (CAT) (EC 1.11.1.6), superoxide dismutase (SOD) (EC 1.15.1.1), ascorbate peroxidase (APX) (EC 1.11.1.11), and glutathione reductase (GR) (EC 1.6.4.2), by increasing the levels of proline, soluble sugars, soluble protein, ascorbic acid (AsA) and chlorophyll as well as improving root activity. Treatment with T-soybean improved the ratio of glutathione (GSH)/oxidized glutathione (GSSG) and AsA/dehydroascorbate (DHA), and up-regulated the expression of CsAPX and CsGR genes involved in the AsA-GSH cycle. In addition, treatment with T-soybean increased the K+ content and K+/Na+ ratio while decreased the Na+ concentration and ethylene level. In summary, the improved salt tolerance of cucumber plants may be due to multiple mechanisms of T-soybean, such as the increase in reactive oxygen species (ROS) scavenging, as well as maintaining osmotic balance and metabolic homeostasis under salt stress.

A Lateral Flow Immunochromato-graphic Strip Test for Rapid Detection of Oseltamivir Phosphate in Egg and Chicken Meat.

A lateral flow immunochromatographic strip test (LFIST) based on a competitive format was developed for rapid and sensitive on-site detection of oseltamivir phosphate (OP) residues in poultry product. The sensitivity (half inhibitory concentration, IC50) of the LFIST in the detection of egg and chicken meat samples was confirmed to be 2.56 and 2.63 µg/kg, and the limit detection (LOD) value were 0.43 and 0.42 µg/kg, respectively. For intra-assay and inter-assay reproducibility, recoveries of OP spiked samples ranged between 82.8% and 91.2% with coefficients of variations (CV) less than 5.67% (intra-assay) and 6.52% (inter-assay). The performance of LFIST was comparable to high-performance liquid chromatography (HPLC) in a parallel testing of egg samples and chicken samples. LFIST takes less than 5 minutes, eliminates the dependency on professional personnel, and thus can be used as a surveillance tool for on-site detection of OP residues.

A lateral flow immunochromatographic strip test for rapid detection of hexoestrol in fish samples.

A lateral flow immunochromatographic strip test was developed for rapid and sensitive on-site detection of hexoestrol (HES) residues in fish samples with colloidal gold labelling of the anti-HES monoclonal antibody. The strip is composed of a sample pad, a conjugate reagent pad, an absorbent pad and a test membrane containing a control line and a test line. The sensitivity (half inhibitory concentration, IC50) of the strip in the detection of fish extract samples was confirmed to be 1.86 µg kg-1, and the limit of detection value was 0.62 µg kg-1. For intra-assay and inter-assay reproducibility, recoveries of HES-spiked samples ranged from 86.3% to 92.3% and 85.8% to 93.4%, coefficients of variation were 2.91-4.64% and 4.24-5.17%, respectively. High-performance liquid chromatography was employed to confirm the performance of the strip. The strip test takes less than 10 min, and thus provides a repaid method for on-site detection of HES residues.

Helical Nanofibrils of Block Copolymer for High-Performance Ammonia Sensors.

Conjugated polymers with a helical structure have been in rapid development in recent years because of their potential applications in chemical and biological sensors. We demonstrate the fabrication and characterization of helical nanofibrils of block copolymer poly(4-iso-cyano-benzoic acid 5-(2-dimethylamino-ethoxy)-2-nitro-benzylester)- b-poly(3-hexylthiophene) (PPI(-DMAENBA)- b-P3HT) via a transfer-etching method. The density and lateral length of nanofibrils can be facilely controlled by regulating the process conditions, which, in turn, directly determine the electronic property. Organic field effect transistors based on helical nanofibrils were successfully fabricated with the highest mobility of 9.1 × 10-3 cm2/(V s)-1, an on/off ratio of 3.4 × 105, and high bias stability. The helical nanofibrils were proved to be beneficial for obtaining a highly sensitive and selective chemical sensor. And, the transistor based on helical nanofibrils exhibits a relative response of 28.6% to 100 ppb ammonia, which is even much higher than the responses to 1 ppm ammonia for homo poly(3-hexylthiophene) nanofibrils (7%) and block copolymer nanofibrils without helical structure (0.9%). The combination of helical structure with nanofibrils may provide a new strategy to fabricate high-performance chemical sensors suitable for use in environmental monitoring, industrial and agricultural production, health care, and foodsafety.

Draft genome sequence of Paenibacillus strain LK1, a phytohormone producing bacterium.

A high-quality draft genome sequence of a multi-antibiotic resistant strain, Paenibacillus strain LK1 isolated from the rhizosphere of Auricularia auricular is described. Strain LK1 produced several types of phytohormones, which included Indole-3-acetic acid (IAA) and Zeatin. Phylogenetic analysis of the 16S rRNA gene of strain LK1 showed a close relationship to P. taichungensis and P. pabuli (99% gene sequence similarity). The genome size of strain LK1 was estimated to be 7.16 Mb that consisted of 82 contigs contained in 49 scaffolds. The G + C content of the genome was 45.63% and it encoded 6499 genes, 115 pseudo genes, 8 rRNAs, 33 tRNAs, and 4 ncRNAs, based on the Prokaryotic Genome Annotation Pipeline (PGAP). Further analysis of the genome of strain LK1 identified 16 genes encoding monooxygenase and six genes encoding cytochrome P450, which may be potentially involved in zeatin biosynthesis. The draft whole genome sequence and annotation of strain LK1 has been deposited at DDBJ/EMBL/GenBank under the accession number (PEII00000000).

Hydrogenated TiO2 nanotube photonic crystals for enhanced photoelectrochemical water splitting.

We report the design, fabrication and characterization of novel TiO2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO2 nanotube photonic crystals are fabricated by annealing of anodized TiO2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm-2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.

Prokaryotic diversity and biochemical properties in aging artificial pit mud used for the production of Chinese strong flavor liquor.

At present, artificial pit mud (APM) is widely used in Chinese liquor-making industry and plays a particular role in the production of Chinese strong flavor liquor (CSFL). However, APM frequently ages during fermentation, thus becoming unsuitable for sustainable use due to its low-quality. The reasons behind, and results of, APM aging during the production of CSFL are not yet understood. Sequencing the V4 region of the 16S rRNA gene shows that prokaryotic diversity is significantly decreased (Shannon's diversity index, P < 0.01) and community composition is distinctly changed (from 1197 to 865 OTUs) in aging APM. On the phylum level, the increase of Firmicutes and decrease of Proteobacteria are the main consequences of APM aging during the production of CSFL. The counting of cultivatable bacteria confirmed that there was a large increase in Lactobacilli and aerobic spore-forming bacteria in aging low-quality APM (more than twofold). Unexpectedly, the total number of caproic acid-producing bacteria, mainly Clostridia, did not change significantly between the two kinds of APM. Furthermore, biochemical analysis indicates that the pH and the levels of NH4+ and K+ are decreased in aging low-quality APM (P < 0.01). The results obtained in this study support the possibility that environmental factors (pH, nutrients) induce the decrease of prokaryotic diversity, and the changed community composition influences the environmental properties. Therefore, through interfering with the cycle, APM aging can be controlled potentially by adjustment of environmental factors and/or supplementation of diminished or missed microorganisms.

A HClO-specific near-infrared fluorescent probe for determination of Myeloperoxidase activity and imaging mitochondrial HClO in living cells.

Hyperchlorous acid (HClO), produced from MPO, is recognized as a host defense that kills pathogens; a signaling molecule that initiates cell apoptosis; and a harmful agent when overproduced. Thus, measuring of endogenous HClO and MPO will always find its great importance in revealing biological roles under complex biological conditions. In this study, a turn-on near infrared (NIR) fluorescent probe Cy7-NphS has been designed and developed for highly selective and sensitive sensing of HClO and Myeloperoxidase (MPO) with fast response time. The newly developed probe has been successfully applied in real-time monitoring of HClO and MPO activity in PBS solutions and living HL-60 cells. When applied in MPO activity determination, the probe showed very high sensitivity with a detection limit of as low as 3.69×10(-3)U/mL. Furthermore, the living cell imaging study suggested that this probe could detect HClO in mitochondria.

Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin-catalyzed peroxidative reaction.

A new method for the determination of selenium based on its fluorescence quenching on the hemoglobin-catalyzed reaction of H2 O2 and l-tyrosine has been established. The effect of pH, foreign ions and the optimization of variables on the determination of selenium was examined. The calibration curve was found to be linear between the fluorescence quenching (F0 /F) and the concentration of selenium within the range of 0.16-4.00 µg/mL. The detection limit was 1.96 ng/mL and the relative standard deviation was 3.14%. This method can be used for the determination of selenium in Se-enriched garlic bulbs with satisfactory results.

Determination of dobutamine hydrochloride by enzymatic catalytic spectrofluorimetry.

A highly sensitive and simple spectrofluorimetric method for the determination of dobutamine hydrochloride based on its inhibitory effect on the hemoglobin-catalyzed reaction of H2 O2 and l-tyrosine was developed. The relationship between the concentration of dobutamine hydrochloride and the fluorescence quenching (ΔF) of the system is linear under the optimal experimental conditions. The calibration graph is linear in the range 2.00 × 10(-7) to 3.00 × 10(-6) g/mL with a limit of detection of 4.83 × 10(-9) g/mL. This method can be used for the determination of dobutamine hydrochloride in its pharmaceutical formulations and in urine with satisfactory results.