Intrinsic defects in B-site columnar-ordered halide double perovskites Cs2AgPdBr5.

Cs2AgPdBr5 is a new type of double perovskite with one-dimensional electronic dimensionality, which is expected to be a promising candidate of photovoltaic materials. Considering that defects usually exist in real materials, in this study, we investigate the intrinsic defect properties of Cs2AgPdBr5 from first principles. First, the phase diagram of Cs2AgPdBr5 is calculated. It turns out that its thermodynamic stable region is small, suggesting that the growth conditions should be carefully controlled to obtain high-quality samples. By systematically investigating the Fermi-level pinning behavior, we find that p-type Cs2AgPdBr5 can be obtained at an Ag-poor condition. At the same time, Pd2+i and Pd1+Ag are the only two deep-level recombination centers at 300 K. Therefore, if possible, the amount of palladium should be relatively small in the synthesis process. Our study provides guidance to obtain high-performance Cs2AgPdBr5 materials for photovoltaic applications.

Near-Neighbor Electron Orbital Coupling Effect of Single-Atomic-Layer Au Cluster Intercalated Bilayer 2H-TaS2 for Surface Enhanced Raman Scattering Sensing.

It is difficult to perfectly analyze the enhancement mechanism of two-dimensional (2D) materials and their combination with precious metals as surface enhanced Raman scattering (SERS) substrates using chemical enhancement mechanisms. Here, we propose a new mentality based on the coupling effect of neighboring electron orbitals to elucidate the electromagnetic field enhancement mechanism of single-atom-layer Au clusters embedded in double-layer 2H-TaS2 for SRES sensing. The insertion of Au atoms into the 2H-TaS2 interlayer was verified by XRD, AFM, and HRTEM, and a SERS signal enhancement of 2 orders of magnitude was obtained compared to the pure 2H-TaS2. XPS and micro-UV/vis-NIR spectra indicate that the outer electrons of neighboring Au and 2H-TaS2 overlap and migrate from Au to 2H-TaS2. First-principles calculations suggest strong electronic coupling between Au and 2H-TaS2. This study offers insights into SERS enhancement in nonprecious metal compounds and guides the development of new SERS substrates.

Increasing the Efficiency of Photocatalytic Water Splitting via Introducing Intermediate Bands.

Photocatalytic water splitting is a potential way to utilize solar energy. To be practically useful, it is important to have a high solar-to-hydrogen (STH) efficiency. In this study, we propose a conceptually new photocatalytic water splitting model based on intermediate bands (IBs). In this new model, introducing IBs within the band gap can significantly increase the STH efficiency limit (from 30.7% to 48.1% without an overpotential and from 13.4% to 36.2% with overpotentials) compared to that in conventional single-band gap photocatalytic water splitting. First-principles calculations indicate that N-doped TiO2, Bi-doped TiO2, and P-doped ZnO have suitable IBs that can be used to construct IB photocatalytic water splitting systems. The STH efficiency limits of these three doped systems are 10.0%, 12.0%, and 19.0%, respectively, while those of pristine TiO2 and ZnO without IB are only 0.9% and 1.6%, respectively. The IB photocatalytic water splitting model proposed in this study opens a new avenue for photocatalytic water splitting design.

Dynamic nonlinear connectedness between the green bonds, clean energy, and stock price: the impact of the COVID-19 pandemic.

This paper uses weekly data from July 01, 2011 to July 09, 2021 to examine the dynamic nonlinear connectedness between the green bonds, clean energy, and stock price around the COVID-19 outbreak in the global markets. By building a time-varying parameter vector autoregression model (TVP-VAR), the comparison analyses of pre- and during the COVID-19 sample groups verify the existence of nonlinear and dynamic correlation among the three variables. First, prior to the COVID-19 pandemic, the simultaneous impacts of clean energy on stock price increased over time. Second, the results of impulse responses at different horizons indicate that green bonds lead to a short-term increase of clean energy, and it exerts an increasingly positive impacts after the COVID-19 outbreak. The COVID-19 has weakened the negative impacts of green bonds on stock price in the medium term. Finally, through the analysis of impulse responses at different points, we find that stock prices will rise when clean energy is subjected to a positive shock, and this positive effect is stronger during economic recovery period than in the other two periods.

Evaluation of the Cepheid Xpert C. difficile diagnostic assay: an update meta-analysis.

BACKGROUND: Accurate and rapid diagnosis of Clostridium difficile infection (CDI) is critical for effective patient management and implementation of infection control measures to prevent transmission. OBJECTIVES: We updated our previous meta-analysis to provide a more reliable evidence base for the clinical diagnosis of Xpert C. difficile (Xpert C. difficile) assay. METHODS: We searched PubMed, EMBASE, Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), and the Chinese Biomedical Literature Database (CBM) databases to identify studies according to predetermined criteria. STATA 13.0 software was used to analyze the tests for sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curves (AUC). QUADAS-2 was used to assess the quality of included studies with RevMan 5.2. Heterogeneity in accuracy measures was tested with Spearman correlation coefficient and chi-square. Meta-regressions and subgroup analyses were performed to figure out the potential sources of heterogeneity. Model diagnostics were used to evaluate the veracity of the data. RESULTS: A total of 26 studies were included in the meta-analysis. The pooled sensitivity (95% confidence intervals [CI]) for diagnosis was 0.97(0.95-0.98), and specificity was 0.96(0.95-0.97). The AUC was 0.99 (0.98-1.00). Model diagnostics confirmed the robustness of our meta-analysis's results. Significant heterogeneity was still observed when we pooled most of the accuracy measures of selected studies. Meta-regression and subgroup analyses showed that the sample size and type, ethnicity, and disease prevalence might be the conspicuous sources of heterogeneity. CONCLUSIONS: The up-to-date meta-analysis showed the Xpert CD assay had good accuracy for detecting CDI. However, the diagnosis of CDI must combine clinical presentation with diagnostic testing to better answer the question of whether the patient actually has CDI in the future, and inclusion of preanalytical parameters and clinical outcomes in study design would provide a more objective evidence base.

Rapid method for direct identification of positive blood cultures by MALDI-TOF MS.

Application of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using positive blood cultures (BCs) is a revolution in identification of microorganisms in clinical microbiology laboratories. Although there are several commercial pretreatment protocols they are expensive. Here, we evaluated the performance of a locally produced Bioyong pre-treatment kit for the direct identification of microorganisms in positive BCs by MALDI-TOF MS method. The mocked positive BCs were performed using 200 Thermo aerobic blood culture bottles and 200 aerobic Scenker blood culture bottles. A total of 200 organisms were invovled, including 91 strains of Gram-positive bacteria, 97 strains of Gram-negative bacteria and 12 strains of Candida. The positive BCs were subcultured and identified by classical biochemical Vitek II testing as the gold standard of identification. The Bioyong pre-treatment kit could successfully identify microorganisms in 189 (94.5%) Thermo positive BCs and 189 (94.5%) Scenker positive blood cultures, respectively. In total, 94 (96.9%) Gram-negative bacteria, 86 (94.5%) Gram-positive bacteria and 9 (75.0%) candida isolated from Thermo positive BCs were correctly identified to species level and 95 (97.9%) Gram-negative bacteria, 86 (94.5%) Gram-positive bacteria and 8 (66.7%) candida isolated from Scenker positive BCs were correctly identified to species level. This method provides a rapid, accurate identification of bacteria and Candida within one hour in positive blood cultures. Routine application of this technique will improve the antimicrobial treatment within 24 h among the patients with bacteremia and candidemia.

An enhanced low-frequency vibration ZnO nanorod-based tuning fork piezoelectric nanogenerator.

In this paper, a piezoelectric nanogenerator (PENG) based on a tuning fork-shaped cantilever was designed and fabricated, aiming at harvesting low frequency vibration energy in the environment. In the PENG, a tuning fork-shaped elastic beam combined with ZnO nanorods (NRs), instead of conventional rectangular cantilever beams, was adopted to extract vibration energy. Benefiting from the high flexibility and the controllable shape of the substrate, this PENG was extremely sensitive to vibration and can harvest weak vibration energy at a low frequency. Moreover, a series of simulation models were established to compare the performance of the PENG with that of different shapes. On this basis, the experimental results further verify that this designed energy harvester could operate at a low frequency which was about 13 Hz. The peak output voltage and current could respectively reach about 160 mV and 11 nA, and a maximum instantaneous peak power of 0.92 µW cm-3 across a matched load of 9 MΩ was obtained. Evidently, this newly designed PENG could harvest vibration energy at a lower frequency, which will contribute to broaden the application range of the PENG in energy harvesting and self-powered systems.

Enhanced performance of ZnO microballoon arrays for a triboelectric nanogenerator.

In recent years, triboelectric nanogenerators (TENGs), harvesting energy from the environment as a sustainable power source, have attracted great attention. Currently, many reports focus on the effect of surface modification on the electrical output performance of the TENG. In this work, we have fabricated vertically grown ZnO microballoon (ZnOMB) arrays on top of pyramid-featured PDMS patterned film, contacted with PTFE film to construct the TENG. The electrical output performances of the designed TENG are presented under external forces with different frequencies. The corresponding output open-circuit voltage with ZnOMBs could reach about 57 V the current density about 59 mA m-2 at 100 Hz, which was about 2.3 times higher than without any ZnO. The global maximum of the instantaneous peak power could reach 1.1 W m-2 when the external load resistance was about 2 MΩ. Furthermore, the electrical output of the fabricated device could light 30 commercial LED bulbs without any rectifier circuits or energy-storage elements. This clearly suggests that this kind of surface modification can dramatically enhance the output performance of the TENG. Moreover, the design of TENG demonstrated here can be applied to various energy harvesting applications.