Latest ArticlesBacteria producing β-lactamases have become a major issue in the global public health field. To restrain the development of drug resistance and reduce the abuse of antibiotics, it is very important to rapidly identify bacteria producing β-lactamases and put forward a reasonable treatment plan. Here, an integrated microfluidic chip-mass spectrometry system was proposed for rapid screening of β-lactamase-producing bacteria and optimization of β-lactamase inhibitor dosing concentration. The concentration gradient generator followed by an array of bacterial culture chambers, as well as micro-solid-phase extraction columns was designed for sample pretreatment before mass analysis. By using the combination system, the process of the hydrolysis of antibiotics by β-lactamase-producing bacteria could be analyzed. To validate the feasibility, four antibiotics and two antibiotic inhibitors were investigated using three strains including negative control, SHV-1 and TEM-1 strains. SHV-1 and TEM-1 strains were successfully distinguished as the β-lactamase producing strains. And the acquired optimal concentrations of β-lactamase inhibitors were in accordance with the results by that obtained from the traditional microdilution broth method. The total analysis time only needed around 2 h, which was faster than conventional methods that require a few days. The technique presented herein provides an easy and rapid protocol for β-lactamase resistance related studies, which is important for the inhibition of antimicrobial resistance development and the reduction of antibiotics abuse.
Carbon dioxide (CO2) is an attractive C1 building block in chemical synthesis due to its abundance, availability and sustainability. However, the low reactivity and high stability generally limits its transformations under mild conditions to value added chemicals. Recent advances in flow chemistry provide effective means for the chemical transformation of CO2, and many new methods and techniques that fully utilized the advantages of continuous flow platforms for the chemical fixation of CO2 have been realized. In view of the rapid development and the urgent need for continuous transformation of CO2, herein we wish to present an update of the recent advances in this research area.
Understanding the negative thermal expansion (NTE) mechanism is of great importance. In this work, we consider the new NTE compound GdFe(CN)6 (αv = −34.2×10-6 K-1) as a case study to investigate the NTE mechanism from the perspective of the lattice vibrational dynamics. The atomic mean-square displacements suggest that the NTE of GdFe(CN)6 comes from the strong tension effect induced by the transverse vibrations of the atomic –Fe–C≡N–Gd– linkages, with the largest contribution given by N atoms. Lattice dynamics calculations show that three low-frequency optical modes at about 50 cm-1 show the largest negative Grüneisen parameters thus providing the largest contribution to the NTE. The existence of these unusual low-frequency vibrational modes can be ascribed to the presence of GdN6 trigonal prisms in the framework structure of GdFe(CN)6.
Zn-gas batteries have attracted great attention in the area of energy conversion and storage owing to their high theoretical energy density in the past decades. In addition to the most widely researched Zn-air/oxygen battery, other novel Zn-gas batteries such as Zn-CO2, Zn-N2 and Zn-NO batteries as "killing two birds with one stone" strategy have emerged to provide energy power and upgrade the pollutant/useless gases simultaneously. This technology becomes more appealing as a low-cost and controllable method to produce value-added chemicals and fuels (such as CO, HCOO−, CH4, NH3) at the cathode driven by surplus electricity. However, there is an absence of a guide for the selection of catalyst and the construction of energy system. Herein, we overview recent achievements in typical Zn-gas batteries beyond Zn-air/oxygen, mainly including Zn-CO2, Zn-N2 and Zn-NO batteries. The energy storage mechanism of these novel Zn-gas batteries has been clearly elaborated. Then, the produced value-added chemicals and the design of cathodic catalyst materials are summarized. Lastly, the remaining challenges and possible directions of Zn-gas batteries, such as highly reduced products, high yield rate and remarkable battery performance, in the future are discussed.
Stable solid-electrolyte interphase (SEI) is crucial for advanced development of lithium metal batteries. However, the continuous collapse and reconstruction of SEI will deplete fresh Li and electrolytes upon cycling, leading to irreversible capacity loss. Herein, we addressed this issue by pre-formation of artificial robust hybrid interphase on a 3D layered graphene/lithium metal framework, in which is constructed by LiF associated with Li2TiF6 generated by the in-situ reaction between the surfacial lithium and titanium fluoride contained electrolytes. The as-obtained interphase can maintain the structure integrality and avoid continuous consumption of the fresh Li and electrolytes. As a consequence, the Li symmetric cells achieve high-efficiency Li deposition and stable cycling over 3600 h. When paired with LiFePO4 cathodes, the coin cells exhibit long lifespan (> 800 cycles) with almost 88.3% retention of the initial capacity.
Carbon-mediated persulfate advanced oxidation processes (PS-AOPs) are appealing in contaminant remediation. For the first time, S,B-co-doped carbon-based persulfate activators were synthesized through direct carbonization of sodium lignosulfonate and boric acid. By degrading sulfamethoxazole (SMX), CSB-750 obtained 98.7% removal and 81.4% mineralization within 30 min. In comparison with solo S or B doping, S and B co-doped carbon showed the coupling effect for enhanced catalysis. The rate constant (kobs) of 0.1679 min–1 was 22.38- and 279.83-fold higher than those of CS-750 (0.0075 min–1) and CB-750 (0.0006 min–1), respectively. The degradation was efficient at strong acidic and weak basic conditions (pH 3–9). Substantial inhibition effect was presented at strong basic condition (pH 10.95) and in presence of CO32–. The CO32–-caused inhibition was the combined result of the cooperation of pH and quenching O2·–. Thiophene sulfur, BC3, BC2O, and structural defects were identified as the active sites for PS activation. Radical and nonradical pathways were both involved in the CSB-750/PS/SMX system, where 1O2 dominated the degradation, SO4·–, ·OH and direct electron transfer played the subordinate role, and O2·– served as a precursor for the formation of partial 1O2. The toxicity of degradation system, the effect of real water matrix, and the reusability of carbocatalysts were comprehensively analyzed. Nine possible degradation pathways were proposed. This work focuses on the catalytic performance improvement through the coupling effect of S, B co-doping, and develops an advanced heteroatom doping system to fabricate carbonaceous persulfate activators.
Deuterated ethylene is an important building block for manufacturing various deuterated polyolefins and chemicals. However, low-cost and large-scale production of deuterated ethylene still remain a great challenge. Herein, with D2O as the D source, we first propose an electrocatalytic deuteration strategy for continuous production of deuterated ethylene from acetylene under ambient conditions. Specially, Ag nanoparticles exhibit a very high deuterated ethylene Faradic efficiency of up to 99.3% at –0.6 V vs. reversible hydrogen electrode. Meanwhile, Ag nanoparticles achieve a deuterated ethylene production rate of 3.72 × 103 mmol h–1 gcat–1 and an excellent long-term stability with deuterated ethylene Faradaic efficiencies of ~95% in a two-electrode flow cell, which substantially outperform state-of-the-art values for previously reported deuterated alkenes. In-situ electrochemical Infrared absorption and Raman spectroscopies reveal superior acetylene absorption and formation of deuterated ethylene on Ag nanoparticles. This efficient electrocatalytic deuteration strategy opens a new window for continuous and economic production of deuterated alkenes.
Ultra-low dielectric loss (Df) and low dielectric constant (Dk) materials are urgently required in high-speed and large-capacity transmission, in which the wholly aromatic liquid crystal polymer (LCP) has gained attention due to its excellent dielectric properties. However, the relationship between molecular structure and dielectric properties is still not clear. In this study, two copolyesters containing phenyl or naphthyl structures are synthesized, as well as the effects of benzene and naphthalene mesogens on dielectric properties are investigated. The synthesized copolyesters containing naphthalene structure have good comprehensive properties with high thermal stability (T5% = 479 ℃ and Tg = 195–216 ℃), inherent flame retardance (LOI = 33.0–35.0 and UL-94 V-0 level at 0.8 mm), low Dk (2.9–3.0@10 GHz) and low Df (0.0027–0.0047@10 GHz). Naphthalene mesogen can reduce the dielectric loss more significantly than benzene at high frequency by reducing the density and mobility of polarizable groups, which leads to the effectively limited dipole polarization in copolyesters. Consequently, we proposed a new strategy for designing low Dk and low Df materials.
The dioxygen activation catalyzed by 4-hydorxylphenyl pyruvate dioxygenase (HPPD) were reinvestigated by using hybrid quantum mechanics/molecular mechanics (QM/MM) approaches at the B3LYP/6-311++G(d, p): AMBER level. These studies showed that this reaction consisted of two steps including the dioxygen addition/decarboxylation and hetero OO bond cleavage, where the first step was found to be rate-determining. The former step initially runs on a septet potential energy surface (PES), then switches to a quintet PES after crossing a septet/quintet minimum energy crossing point (MECP) 5-7M2, whereas the rest step runs on the quintet PES. The reliability of our theoretical predictions is supported by the excellent agreement of the calculated free-energy barrier value of 16.9 kcal/mol with available experimental value of 16–17 kcal/mol. The present study challenges the widely accepted view which holds that the O2 activation catalyzed by α-keto glutamate (α-KG) dioxygenase mainly runs on the quintet PES and provides new insight into the catalytic mechanism of α-KG dioxygenase and/or other related Fe(Ⅱ)-dependent oxygenase.
The supercapacitive properties of manganese oxides (MnOx) are strongly affected by their crystal structure. Nevertheless, the relationship between the crystal structure and supercapacitive performance of MnOx is elusive. Herein, a temperature-controlled fabrication method was developed to achieve MnO2, Mn3O4, MnO and Mn2O3 microspheres with various crystal structure as electrode materials tunable for supercapacitors. The detailed material and electrochemical characterizations revealed the structure-activity relationship of MnOx microspheres by systematically investigating the effect of valence state, specific surface area, conductivity and morphology on supercapacitive performance. Among these MnOx materials, nanoneedle-like MnO2 delivered a relatively high specific capacitance of 274.1 F/g at 1 A/g due to a high Mn valence state of +4, a large specific surface area of 113.4 m2/g and a desirable electronic conductivity of 1.73 × 10–5 S/cm. Furthermore, MnO2 presented a remarkable cycle stability with 115% capacitance retention after 10,000 cycles owing to the enhancement of wettability. This work not only provides a facile strategy to modulate MnOx crystal structure, but also offers a deep understanding of structure-dependent supercapacitive performance of MnOx.
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