Characterization of a novel high-efficiency cracking Burkholderia gladiolus phage vB_BglM_WTB and its application in black fungus.

Burkholderia gladiolus (B. gladiolus) is foodborne pathogenic bacteria producing bongkrekic acid (BA), which causes food poisoning and has a mortality rate of up to 40 % or more. However, no drugs have been reported in the literature for the prevention and treatment of this infection. In this study, a phage was identified to control B. gladiolus. The novel phage vB_BglM_WTB (WTB), which lyse B. gladiolus with high efficiency, was isolated from sewage of Huaihe Road Throttle Well Sewage Treatment Plant in Hefei. Transmission electron microscopy showed that WTB had an icosahedral head (69 ± 2 nm) and a long retractable tail (108 ± 2 nm). Its optimal temperature and pH ranges to control B. gladiolus were 25 °C -65 °C and 3-11 respectively. The phage WTB was identified as a linear double-stranded DNA phage of 68, 541 bp with 60.04 % G + C content, with a long latent period of 60 min. Phylogenetic analysis and comparative genetic analysis indicated that phage WTB has low identity (<50 %) with other phages, with the highest similarity to Burkholderia phage Maja (25.7 %), which showed that it does not belong to any previous genera recognized by the International Committee on Taxonomy of Viruses (ICTV) and was a candidate for a new genus within the Caudoviricetes. We have submitted a new proposal to ICTV to create a new genus, Bglawtbvirus. No transfer RNA (tRNA), virulence associated and antibiotic resistance genes were detected in phage WTB. Experimental results indicated that WTB at 4 °C and 25 °C had excellent inhibition activity against B. gladiolus in the black fungus, with an inhibition efficiency of over 99 %. The amount of B. gladiolus in the black fungus was reduced to a minimum of 89 CFU/mL when treated by WTB at 25 °C for 2 h. The inhibition rate remained at 99.97 % even after 12 h. The findings showed that the phage WTB could be applied as a food-cleaning agent for enhancing food safety and contributed to our understanding of phage biology and diversity.

Efficient and Stable Methylammonium-Free Tin-Lead Perovskite Solar Cells with Hexaazatrinaphthylene-Based Hole-Transporting Materials.

Incorporating non-aqueous hole-transporting materials (HTMs) to replace the widely used PEDOT:PSS is favorable for improving the stability of tin-lead perovskite solar cells (Sn-Pb PSCs). Herein, hexaazatrinaphthylene (HATNA) is found to be a promising HTM building block for Sn-Pb PSCs. By introducing triphenylamine (TPA) and methoxy-triphenylamine into the HATNA core, molecular energy levels and surface wettability can be well regulated, and a high hole mobility and thermal stability can be maintained. Moreover, a homogeneous Sn-Pb perovskite film with low Sn4+ contents and vertically orientated grains can be prepared on the substrate TPA-HATNA. Compared with PEDOT:PSS, the optimal TPA-HATNA-based methylammonium-free device enables a 70 mV increase in VOC, delivering a remarkable PCE exceeding 18% (certified 16.4%). Impressively, the TPA-HATNA-based devices without encapsulation retain 90% efficiency after aging for 600 min under maximum-power-point tracking. Our work provides alternative HTMs for boosting the performance of Sn-Pb PSCs.

A Coplanar π-Extended Quinoxaline Based Hole-Transporting Material Enabling over 21 % Efficiency for Dopant-Free Perovskite Solar Cells.

Developing dopant-free hole transporting materials (HTMs) is of vital importance for addressing the notorious stability issue of perovskite solar cells (PSCs). However, efficient dopant-free HTMs are scarce. Herein, we improve the performance of dopant-free HTMs featuring with a quinoxaline core via rational π-extension. Upon incorporating rotatable or chemically fixed thienyl substitutes on the pyrazine ring, the resulting molecular HTMs TQ3 and TQ4 show completely different molecular arrangement as well as charge transporting capabilities. Comparing with TQ3, the coplanar π-extended quinoxaline based TQ4 endows enriched intermolecular interactions and stronger π-π stacking, thus achieving a higher hole mobility of 2.08×10-4  cm2 V-1 s-1 . It also shows matched energy levels and high thermal stability for application in PSCs. Planar n-i-p structured PSCs employing dopant-free TQ4 as HTM exhibits power conversion efficiency (PCE) over 21 % with excellent long-term stability.

Fabrication of a dual-emitting dye-encapsulated metal-organic framework as a stable fluorescent sensor for metal ion detection.

Dye-loaded metal organic frameworks (MOFs) are regarded as one of the most fascinating luminescent materials for selective chemical sensing. Herein, a facile two-step synthesis procedure is reported for the successful encapsulation of fluorescein dye into porous zinc-adenine metal-organic framework (bio-MOF-1) crystals, and thus the aggregation-caused quenching of dye molecules can be eliminated in the confined MOF structure to further create dual emission centers. The as-prepared solid state fluorescein@bio-MOF-1 composite exhibits both the characteristic emissions of the fluorescein dye and bio-MOF-1, and host-guest energy transfer also occurs. Particularly, depending on the variety of the luminescence intensities of different metal ions incorporated in fluorescein@bio-MOF-1, such a host-guest system could be used for high-sensitive sensing of metal cations, especially for the drastic luminescence quenching of Fe3+ ions. The quenching effect coefficient (Ksv) for every metal ion detected is calculated, and the largest Ksv value for Fe3+ ions is determined to be 5072 M-1. Such an encapsulation strategy can be widely adopted to design new dye@MOF composites with multiple luminescent centers for metal cation sensing.

Synthesis and Luminescence Properties of CsPbX3@Uio-67 Composites toward Stable Photoluminescence Convertors.

All-inorganic halide perovskite (CsPbX3, X = Cl, Br, or I) nanocrystals (NCs) have been widely studied due to their outstanding optoelectronic properties. However, some inevitable factors like light, heat, and moisture affected the stability of CsPbX3 NCs and further limited their practical application. In this work, the stability of all-inorganic halide perovskite NCs can be improved by integrating them in the stable Zr-based metal-organic frameworks (Uio-67). Compared to pristine perovskite NCs, typical CsPbBr3@Uio-67 composites display a stable photoluminescence property that can be maintained for 30 days under ambient atmospheric conditions. Due to the proposed confinement effects of CsPbX3 NCs coordinated with the pore structures of Uio-67, the related structural model of CsPbX3@Uio-67 composites was elucidated. White LED device was further fabricated by combining CsPbBr3@Uio-67 composites and commercial K2SiF6:Mn4+ red phosphors with a blue-emitting chip, which demonstrated a wide color gamut (138% of National Television Standards Committee color space). The strategy on encapsulation of CsPbX3 NCs into Uio-67 will open up a stable platform for optoelectronic applications.

CH3NH3PbBr3 Perovskite Nanocrystals Encapsulated in Lanthanide Metal-Organic Frameworks as a Photoluminescence Converter for Anti-Counterfeiting.

The increasing demands for optical anti-counterfeiting technology require the development of versatile luminescent materials with multiple models and tunable photoluminescence. Herein, the combination of luminescent perovskite nanocrystals and lanthanide-based metal-organic frameworks (Ln-MOFs) has been developed to offer such a high-tech anti-counterfeiting solution. The hybrid materials have been fabricated via the encapsulation of perovskite CH3NH3PbBr3 nanocrystals in europium-based metal-organic frameworks (Eu-MOFs) and they display multistage anti-counterfeiting behavior. CH3NH3PbBr3@Eu-MOF hybrids were developed in a two-step process, where the PbBr2@Eu-MOF precursor was formed first and, then, the composites can be formed quickly by the addition of CH3NH3Br into the precursors. Accordingly, the hybrid composites exhibited both excitation wavelength and temperature-dependent luminescence properties in the form of powders or films. Furthermore, the photoluminescence of the CH3NH3PbBr3@Eu-MOF composites can be quenched and recovered through water immersion and CH3NH3Br conversion, and the anti-counterfeiting applications have also been discussed. Therefore, this finding will open the opportunity to fabricate the hybrid materials with controlled photoluminescence properties, and it also acts as the emerging anti-counterfeiting materials in versatile fields.

Encapsulation of CH3NH3PbBr3 Perovskite Quantum Dots in MOF-5 Microcrystals as a Stable Platform for Temperature and Aqueous Heavy Metal Ion Detection.

The stability issue of organometallic halide perovskites remains a great challenge for future research as to their applicability in different functional material fields. Herein, a novel and facile two-step synthesis procedure is reported for encapsulation of CH3NH3PbBr3 perovskite quantum dots (QDs) in MOF-5 microcrystals, where PbBr2 and CH3NH3Br precursors are added stepwise to fabricate stable CH3NH3PbBr3@MOF-5 composites. In comparison to CH3NH3PbBr3 QDs, CH3NH3PbBr3@MOF-5 composites exhibited highly improved water resistance and thermal stability, as well as better pH adaptability over a wide range. Luminescent investigations demonstrate that CH3NH3PbBr3@MOF-5 composites not only featured excellent sensing properties with respect to temperature changes from 30 to 230 °C but also exhibited significant selective luminescent response to several different metal ions in aqueous solution. These outstanding characteristics indicate that the stable CH3NH3PbBr3@MOF-5 composites are potentially interesting for application in fluorescence sensors or detectors.

Size Effect of Silica Shell on Gas Uptake Kinetics in Dry Water.

Two kinds of dry water (DW) particles are prepared by mixing water and hydrophobic silica particles with nanometer or micrometer dimensions, and the two DW particles are found to have similar size distributions regardless of the size of the silica shell. The CO2 uptake kinetics of DW with nanometer (nanoshell) and micrometer shells (microshell) are measured, and both uptake rate and capacity show the obvious size effect of the silica shell. The DW with a microshell possesses a larger uptake capacity, whereas the DW with a nanoshell has a faster uptake rate. By comparing the uptake kinetics of soluble NH3 and CO2 further, we found that the microshell enhances the stability and the dispersion degree of DW and the nanoshell offers a shorter path for the transit of guest gas into the water core. Furthermore, molecular dynamics simulation is introduced to illustrate the nanosize effect of the silica shell on the initial step of the gas uptake. It is found that the concentration of gas molecules close to the silica shell is higher than that in the bulk water core. With the increase in the size of the silica shell, the amount of CO2 in the silica shell decreases, and it is easier for the gas uptake to reach steady state.

Origin of Self-preservation Effect for Hydrate Decomposition: Coupling of Mass and Heat Transfer Resistances.

Gas hydrates could show an unexpected high stability at conditions out of thermodynamic equilibrium, which is called the self-preservation effect. The mechanism of the effect for methane hydrates is here investigated via molecular dynamics simulations, in which an NVT/E method is introduced to represent different levels of heat transfer resistance. Our simulations suggest a coupling between the mass transfer resistance and heat transfer resistance as the driving mechanism for self-preservation effect. We found that the hydrate is initially melted from the interface, and then a solid-like water layer with temperature-dependent structures is formed next to the hydrate interface that exhibits fractal feature, followed by an increase of mass transfer resistance for the diffusion of methane from hydrate region. Furthermore, our results indicate that heat transfer resistance is a more fundamental factor, since it facilitates the formation of the solid-like layer and hence inhibits the further dissociation of the hydrates. The self-preservation effect is found to be enhanced with the increase of pressure and particularly the decrease of temperature. Kinetic equations based on heat balance calculations is also developed to describe the self-preservation effect, which reproduces our simulation results well and provides an association between microscopic and macroscopic properties.