Lead-Free Cesium Thulium Halide Perovskite Microcrystals for Near Ultraviolet Luminescence.

Lead halide perovskites attract tremendous research attention due to excellent optoelectronic properties. However, realizing efficient near ultraviolet (NUV) luminescence with these materials is still a big challenge. Herein, a novel rare-earth perovskite cesium thulium chloride (CsTmCl3 ) with high crystallinity has been synthesized via a simple hot-injection method. The obtained CsTmCl3 microcrystals have a size distribution of around 1-5 µm, and demonstrate a highly efficient NUV emission at 337 nm with a full width at half maximum (FWHM) of 68 nm. The determined band gap of CsTmCl3 microcrystals is ≈3.92 eV, which is supported by theoretical calculations. Moreover, a high photoluminescence quantum yield (PLQY) of up to 12% in NUV region has been achieved in such a lead-free perovskite. The findings suggest that CsTmCl3 perovskite microcrystal is a promising low-toxic material for applications in NUV optoelectronic devices.

Efficient Near-Infrared Luminescence Based on Double Perovskite Cs2SnCl6.

Cs2SnCl6 double perovskite has attracted wide attention as a promising optoelectronic material because of its better stability and lower toxicity than its lead counterparts. However, pure Cs2SnCl6 demonstrates quite poor optical properties, which usually calls for active element doping to realize efficient luminescence. Herein, a facile co-precipitation method was used to synthesize Te4+ and Er3+-co-doped Cs2SnCl6 microcrystals. The prepared microcrystals were polyhedral, with a size distribution around 1-3 µm. Highly efficient NIR emissions at 1540 nm and 1562 nm due to Er3+ were achieved in doped Cs2SnCl6 compounds for the first time. Moreover, the visible luminescence lifetimes of Te4+/Er3+-co-doped Cs2SnCl6 decreased with the increase in the Er3+ concentration due to the increasing energy transfer efficiency. The strong and multi-wavelength NIR luminescence of Te4+/Er3+-co-doped Cs2SnCl6 originates from the 4f→4f transition of Er3+, which was sensitized by the spin-orbital allowed 1S0→3P1 transition of Te4+ through a self-trapped exciton (STE) state. The findings suggest that ns2-metal and lanthanide ion co-doping is a promising method to extend the emission range of Cs2SnCl6 materials to the NIR region.

Controlling Molecular Orientation of Small Molecular Dopant-Free Hole-Transport Materials: Toward Efficient and Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs) have great potential for future application. However, the commercialization of PSCs is limited by the prohibitively expensive and doped hole-transport materials (HTMs). In this regard, small molecular dopant-free HTMs are promising alternatives because of their low cost and high efficiency. However, these HTMs still have a lot of space for making further progress in both efficiency and stability. This review firstly provides outlining analyses about the important roles of molecular orientation when further enhancements in device efficiency and stability are concerned. Then, currently studied strategies to control molecular orientation in small molecular HTMs are presented. Finally, we propose an outlook aiming to obtain optimized molecular orientation in a cost-effective way.

Folding a Single-Molecule Junction.

Stimuli-responsive molecular junctions, where the conductance can be altered by an external perturbation, are an important class of nanoelectronic devices. These have recently attracted interest as large effects can be introduced through exploitation of quantum phenomena. We show here that significant changes in conductance can be attained as a molecule is repeatedly compressed and relaxed, resulting in molecular folding along a flexible fragment and cycling between an anti and a syn conformation. Power spectral density analysis and DFT transport calculations show that through-space tunneling between two phenyl fragments is responsible for the conductance increase as the molecule is mechanically folded to the syn conformation. This phenomenon represents a novel class of mechanoresistive molecular devices, where the functional moiety is embedded in the conductive backbone and exploits intramolecular nonbonding interactions, in contrast to most studies where mechanoresistivity arises from changes in the molecule-electrode interface.

A Chemically Soldered Polyoxometalate Single-Molecule Transistor.

Polyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl-capped Anderson-Evans polyoxometalate and used it to fabricate single-molecule junctions, using the organic termini to chemically "solder" a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three-state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge-transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single-entity electrochemical behaviour.

Association of physical activity with risk of metabolic syndrome: findings from a cross-sectional study conducted in rural area, Nantong, China.

The prevalence of metabolic syndrome increases rapidly worldwide, and its association with physical activity (PA) varies with race and lifestyles. Little is known about the association in rural China. The Nantong Metabolic Syndrome Study recruited 13,505 female and 6997 male participants in 2007 and 2008. Socio-demographic characteristics, and physiological and behavioural data were collected. Logistic regression model was applied to estimate associations of metabolic syndrome and its components with different PAs. The overall metabolic syndrome prevalence was 21.6% in current study. Increasing total PA or moderate-to-vigorous-intensity occupational PA was associated with decreasing 5%-60% risk of having metabolic syndrome and abnormal metabolic syndrome components in both genders. An association between leisure-time PA and blood pressure was found in men, but no associations between leisure-time PA and metabolic syndrome components were found in women. Commuting PA, such as walking and taking bus, by bicycle and walking only, was associated with decrease of 20%-45% risk of several abnormal metabolic syndrome components in women. This study provides information for future investigation into the nature of these associations so that recommendations can be developed to reduce the prevalence of metabolic syndrome and its components among rural population in China.

Cascade signal amplification sensing strategy for highly specific and sensitive detection of homologous microRNAs in different molecular subtypes of breast cancer.

Discriminative identification of homologous miRNAs in miRNA family with high specificity and sensitivity is crucial for accurate classification, diagnosis and prognosis of breast cancer. Herein, we report a reliable, sensitive, and selective assay by coupling fluorescence resonance energy transfer (FRET) with cascade signal amplification. The strategy is developed by designing two programmable DNA probes that can be triggered to shift from "off" to "on" state in a cascade hybridization reaction in the presence of target miRNA let-7a, leading to the generation of an amplified signal. The assay can detect concentrations as low as ∼3.0 pM let-7a and discriminate let-7a from other highly homologous members in the let-7 miRNA family. Moreover, it can also be used to determine let-7a levels at single-cell resolution and evaluate the drug efficacy of let-7a expression among various molecular types of breast cancer cell lines. The advantage of this assay is a combined result of signal generation and amplification triggered by target miRNA, which can satisfy an assay of analogous miRNA in a downregulated manner with high specificity. It has promising potential as a selective assay for homologous miRNAs in precision medicine.

In situ formation of H-bonding imidazole chains in break-junction experiments.

As a small molecule possessing both strong H-bond donor and acceptor functions, 1H-imidazole can participate in extensive homo- or heteromolecular H-bonding networks. These properties are important in Nature, as imidazole moieties are incorporated in many biologically-relevant compounds. Imidazole also finds applications ranging from corrosion inhibition to fire retardants and photography. We have found a peculiar behaviour of imidazole during scanning tunnelling microscopy-break junction (STM-BJ) experiments, in which oligomeric chains connect the two electrodes and allow efficient charge transport. We attributed this behaviour to the formation of hydrogen-bonding networks, as no evidence of such behaviour was found in 1-methylimidazole (incapable of participating in intramolecular hydrogen bonding). The results are supported by DFT calculations, which confirmed our hypothesis. These findings pave the road to the use of hydrogen-bonding networks for the fabrication of dynamic junctions based on supramolecular interactions.

Tuning the electron transport band gap of bovine serum albumin by doping with Vb12.

We report a facile and new method to tune the electron transport (ETp) band gaps of proteins (bovine serum albumin, BSA) via doping with other molecules (cyanocobalamin, Vb12). The results indicated that doping with Vb12 can enhance the ETp ability of BSA and reduce its conduction band (CB) and valence band (VB) energy levels, thereby achieving the goal of tuning protein ETp band gaps.

Fluorescence activation imaging of localization, distribution, and level of miRNA in various organelles inside cells.

This work reports an approach for imaging the localization, distribution, and level of miRNA in different organelles based on an activated fluorescence signal triggered by an alteration of the specific binding-induced conformation of the designed activatable probe. We selected miR-150 as an miRNA example to image its localization, distribution, and level in human cervical cancer cells (HeLa cells). The results indicate that miR-150 is localized and distributed in different subcellular organelles (mainly in mitochondria and lysosomes) and that its levels (actually its concentrations) in lysosomes are higher than those in mitochondria in both HeLa and MCF-7 cells. Moreover, the level of miRNA in cells is displayed in a height-dependent (in z-direction) manner. This approach can also be used to image the localization and distribution of various miRNAs (such as miR-150 and miR-214) in different organelles in cancer cells simultaneously. The probes exhibit high resistance to cellular endo- and exonucleases, with high specificity; the capability of avoiding false signals, with a high signal-to-background ratio; and a good ability to operate in complicated environments. The developed approach may provide a useful tool for studying the localization and distribution and evaluating the level of multiple tumor-related miRNAs in cells.

Electrolyzing synthesis of boron-doped graphene quantum dots for fluorescence determination of Fe3+ ions in water samples.

This work reports a facile electrolyzing method to synthesize boron-doped graphene quantum dots (BGQDs) and uses the BGQDs as a fluorescent probe to determine Fe3+ ion levels in water samples. The BGQDs were produced by oxidizing graphite in an aqueous borax solution at pH 7; then, the borate solution was filtered with BGQDs, and the borate was dialyzed from the filtrate, leaving a solution of BGQDs in water. The amount of the B in the BGQDs can be adjusted by changing the concentration of borax used for the electrolyte. The excitation wavelength- and B amount-dependent fluorescence characteristics of BQGDs were studied. The fluorescence intensity of the BGQDs is measurable in real time, and its quenching is very sensitive to the concentration of Fe3+ ions in the system but not to other possible coexisting metal ions. The fluorescence quenching mechanism of Fe3+ ions to BGQDs is studied and explained based on electrochemical voltammetry and DFT simulations. The analytical signal, which is defined as F0/F, where F0 and F are the fluorescence intensities of the BGQDs before and after interaction with Fe3+ ions, respectively, displays a good linear relationship in the Fe3+ ion concentration range of 0.01-100µm with a correlation coefficient of 0.999 and a limit of detection (LOD) of ~(0.005±0.001) µM. The LOD value is much lower than the water quality standards for Fe3+ ions (0.3ppm, ~5.36µm) in drinking water suggested by the WHO (World Health Organization) and EPA (U.S. Environmental Protection Agency), implying that this method has great potential for applications in real sample assays. For example, the determination of the Fe3+ ion levels in three water samples (tap water, groundwater, and lake water) gives approximately the same results as those determined by the EPA-recommended AAS (atomic adsorption spectroscopy) method.

Association between social support and health-related quality of life among Chinese seafarers: A cross-sectional study.

BACKGROUND: Seafarers have reported impaired health and health-related quality of life (HRQOL). Social support might increase HRQOL, but little is known about this association among Chinese seafarers. The aim of this study was to describe social support and explore its association with HRQOL among Chinese seafarers. METHODS: A cross-sectional survey was conducted in the ports of Nantong and Rugao, China, from April to December 2013. A total of 917 Chinese seafarers were interviewed on social support, mental distress, perceived occupational stress, and HRQOL using the following self-administered questionnaires: The Social Support Rating Scale, Self-rating Depression Scale, Occupational Stress Questionnaire, and the World Health Organization Quality of Life-BREF (WHOQOL-BREF) questionnaire. Hierarchical linear regression modelling was used to analyze the association between seafarers' subjective level of social support and their HRQOL. RESULTS: Of the 917 male Chinese seafarers included in the study, 40.7% perceived high levels of social support, and 39.1% were highly satisfied with their overall quality of life (QOL). Hierarchical regression analysis showed significant associations between level of social support and all health dimensions in the WHOQOL-BREF, even after adjusting for depressive symptoms, occupational stress, occupational activities, sleep duration, and other relevant covariates. Compared with the medium or low level social support group, seafarers with a high level of social support had better QOL scores in the general facet health and QOL (ß = 2.43, p<0.05), and the physical health (ß = 3.23, p<0.001), psychological health (ß = 5.56, p<0.001), social relation (ß = 6.07, p<0.001), and environment domains (ß = 4.27, p<0.001). In addition, depression, occupational stress, occupational activities, and sleep duration were found to be determinants of seafarers' HRQOL. CONCLUSIONS: Chinese seafarers have poorer HRQOL than the general population, but social support has a significant positive effect on their HRQOL. Efforts to improve social support should be undertaken.

Associations of metabolic disorder factors with the risk of uncontrolled hypertension: a follow-up cohort in rural China.

We evaluated how metabolic disorders affected antihypertension therapy. 2,912 rural Chinese patients with hypertension who provided blood samples, demographic and clinical data at baseline and after 1 year of antihypertension therapy were evaluated. At baseline, 1,515 patients (52.0%) were already receiving drug therapy and 11.4% of them had controlled blood pressure (BP). After 1 year, all 2,912 patients were receiving antihypertension therapy that was administered by community physicians, and 59.42% of them had controlled BP. Central obesity and abnormal triglyceride, high-density lipoprotein cholesterol, and glucose were associated with 15-70% higher risks of uncontrolled hypertension. Metabolic syndrome using the JIS criteria was associated with poor BP control (odds ratio: 1.71 and 1.54 for the baseline and follow-up datasets, respectively). The risk of uncontrolled hypertension increased with the number of metabolic disorders (p for trend <0.01). The presence of ≥3 metabolic disorder factors was associated with higher risks of poor BP control. The associations of metabolic factors and uncontrolled hypertension were stronger for the standard and modified ATP III criteria, compared to the IDF and JIS criteria. Metabolic factors were associated with less effective antihypertension therapy, and all definitions of metabolic syndrome helped identify patients with elevated risks of uncontrolled hypertension.

Direct Synthesis of Water-Soluble Aptamer-Ag2 S Quantum Dots at Ambient Temperature for Specific Imaging and Photothermal Therapy of Cancer.

Water-soluble Ag2 S near-infrared (NIR) fluorescent quantum dots (QDs) are directly synthesized at ambient temperature for specific cancer imaging and photothermal therapy (PTT) using a designed aptamer (Apt43) as template, which consists of the following two fragments: an aptamer S2.2 sequence for specifically recognizing the cancer cells and an 18-cytosine (18-C) extending spacer for growing Ag2 S QDs. The synthesized Ag2 S QDs (Apt43-Ag2 S QDs), which exhibit strong absorption and fluorescence emission in the NIR region and high photothermal conversion capabilities, can specifically recognize MCF-7 cells (human breast cancer cells) and are usable as a highly intensified imaging agent for cancer diagnosis. Moreover, they can be applied as photothermal agents for the in vitro killing of MCF-7 cells and the in vivo ablation of tumors, which were constructed on the bodies of nude mice. MCF-7 cells almost quantitatively die after they are incubated with the QDs (at 100 µg mL(-1) ) for 2 h and irradiated under an 808 nm laser at a power density of 1.0 W cm(-2) for 10 min. The tumors on the nude mice can also be effectively ablated without regrowth during the period of observation (at least 20 d) after PTT.

Performance Evaluation of Missing-Value Imputation Clustering Based on a Multivariate Gaussian Mixture Model.

BACKGROUND: It is challenging to deal with mixture models when missing values occur in clustering datasets. METHODS AND RESULTS: We propose a dynamic clustering algorithm based on a multivariate Gaussian mixture model that efficiently imputes missing values to generate a "pseudo-complete" dataset. Parameters from different clusters and missing values are estimated according to the maximum likelihood implemented with an expectation-maximization algorithm, and multivariate individuals are clustered with Bayesian posterior probability. A simulation showed that our proposed method has a fast convergence speed and it accurately estimates missing values. Our proposed algorithm was further validated with Fisher's Iris dataset, the Yeast Cell-cycle Gene-expression dataset, and the CIFAR-10 images dataset. The results indicate that our algorithm offers highly accurate clustering, comparable to that using a complete dataset without missing values. Furthermore, our algorithm resulted in a lower misjudgment rate than both clustering algorithms with missing data deleted and with missing-value imputation by mean replacement. CONCLUSION: We demonstrate that our missing-value imputation clustering algorithm is feasible and superior to both of these other clustering algorithms in certain situations.

Prevalence of metabolic syndrome and its risk factors among rural adults in Nantong, China.

The prevalence of metabolic syndrome (MS) varies worldwide due to genetic and environmental factors. A population-based cross-sectional study, with 37,582 participants recruited in Nantong, China in 2007-2008 (stage I) and 2013 (stage II). Socio-demographic, lifestyle factors, disease history and fasting blood sample were collected. The prevalence of MS was much higher in 2013 (42.6%) than that in 2007-2008 (21.6%), which was significantly higher in older people in both stages. Participants with two or more familial history of diseases were associated with a higher MS prevalence compared to those who didn't have familial history of diseases. Total physical activity (PA) was associated with 24 and 19% decreased risk of MS in men and women. Occupational PA in moderate and vigorous intensity was associated with a 25%-45% decreased risk of MS. Female smokers who smoked more than 10 cigarettes per day or over 25 years were associated with 96 and 74% increased MS risk, respectively. The highest quartile of rice wine consumption was associated with a lower risk of MS with OR of 0.63 in women, compared with female non-drinkers. These findings indicated that PA and rice wine are two protective factors in MS prevention in rural areas of East China.