Label-free visualization of carbapenemase activity in living bacteria

Evaluating enzyme activity intracellularly on natural substrates is a significant experimental challenge in biomedical research. We report a label‐free method for real‐time monitoring of the catalytic behavior of class A, B, and D carbapenemases in live bacteria based on measurement of heat changes. By this means, novel biphasic kinetics for class D OXA‐48 with imipenem as substrate is revealed, providing a new approach to detect OXA‐48‐like producers. This in‐cell calorimetry approach offers major advantages in the rapid screening (10 min) of carbapenemase‐producing Enterobacteriaceae from 142 clinical bacterial isolates, with superior sensitivity (97 %) and excellent specificity (100 %) compared to conventional methods. As a general, label‐free method for the study of living cells, this protocol has potential for application to a wider range and variety of cellular components and physiological processes

Ultrafine Pd Nanoparticles Supported on Soft Nitriding Porous Carbon for Hydrogen Production from Hydrolytic Dehydrogenation of Dimethyl Amine-Borane

Simple and efficient synthesis of a nano-catalyst with an excellent catalytic property for hydrogen generation from hydrolysis of dimethyl amine-borane (DMAB) is a missing piece. Herein, effective and recycled palladium (Pd) nanoparticles (NPs) supported on soft nitriding porous carbon (NPC) are fabricated and applied for DMAB hydrolysis. It is discovered that the soft nitriding via a low-temperature urea-pretreatment induces abundant nitrogen-containing species on the NPC support, thus promoting the affinity of the Pd precursor and hindering the agglomeration of formed Pd NPs onto the NPC surface during the preparation process. Surface-clean Pd NPs with a diameter of sub-2.0 nm deposited on the NPC support (Pd/NPC) exhibit an outstanding catalytic performance with a turnover frequency (TOF) of 2758 h−1 toward DMAB hydrolysis, better than many previous reported Pd-based catalysts. It should be emphasized that the Pd/NPC also possesses a good stability without an obvious decrease in catalytic activity for DMAB hydrolysis in five successive recycling runs. This study provides a facile but efficient way for preparing high-performance Pd catalysts for catalytic hydrogen productions

Molecular Dynamics Study of Crystallization Behavior in the Solid State of Zr-Cu Amorphous Alloys

Amorphous alloys show interesting mechanical properties as well as unique physical and chemical properties due to their atomic stacking structure. However, when partial crystallization occurs in amorphous alloys, it can impact the properties of the original amorphous alloy. To study the crystallization phenomenon in the Zr-based amorphous alloy, a three-dimensional Zr-based amorphous alloy atomic-stacking model was established by molecular dynamics simulations, and the atomic structure evolution of the Zr-Cu amorphous system after partial crystallization was analyzed by the radial distribution function g(r), HA bond index and Voronoi polyhedron. The results showed that adding more copper (Cu) atoms to the Zr-Cu amorphous system greatly improves its stability at high temperatures. The atomic diffusion was analyzed by root-mean-square displacement of atoms (MSD); as the temperature rose, the MSD of atoms also increased, suggesting that the crystallization of the amorphous material occurs due to the short-range diffusion of atoms. The analysis of the mechanism of the high-temperature action time on the Zr80Cu20 amorphous alloy showed that the crystallization phase precipitation rate of the amorphous alloy gradually increases with time, but it does not change linearly

UV Light-Assisted Synthesis of Highly Efficient Pd-Based Catalyst over NiO for Hydrogenation of o-Chloronitrobenzene

Supported Pd-based catalyst over active nickel oxide (NiO) was repared using the impregnation method companying with UV-light irradiation. Moreover, the catalytic performance of the obtained Pd-based catalysts was evaluated towards the hydrogenation of o-chloronitrobenzene (o-CNB). Observations indicate that the as-prepared UV-irradiated Pd/NiO catalyst with a mole fraction 0.2% (0.2%Pd/NiO) has higher activity and selectivity in the o-CNB hydrogenation. Especially, UV-light irradiation played a positive role in the improvement of catalytic activity of 0.2%Pd/NiO catalyst, exhibiting an excess 11-fold activity superiority in contrast with non-UV-irradiated 0.2%Pd/NiO catalyst. In addition, it was investigated that effects of varied factors (i.e., reaction time, temperature, o-CNB/Pd ratio, Pd loading, hydrogen pressure) on the selective hydrogenation of ο-CNB catalyzed by UV-irradiated 0.2%Pd/NiO catalyst. Under the reaction conditions of 60 °C, 0.5 h, 1 MPa H2 pressure, 100% conversion of o-CNB, and 81.1% o-CAN selectivity were obtained, even at high molar ratio (8000:1) of o-CNB to Pd

One-Step Preparation and Fluorescence Enhancement Effect in SiO2/Eu2+ Doped with Ag Nanowires

Eu2+ single-doped SiO2 (SiO2/Eu2+) and Eu2+, Ag nanowires co-doped SiO2 (SiO2/Eu2+-Ag) luminescent nanomaterials were prepared by an efficient one-step sol-gel method. Their microstructure and optical properties were characterized, and the fluorescence enhancement of Eu2+ by Ag nanowires was investigated. The experimental results indicate that the average diameter of Ag nanowires doped is 12.5 nm, and the length-diameter ratio is 30. The Ag nanowires cannot only enhance the light absorption of SiO2/Eu2+ in the range of 230-350 nm, but also reduce the fluorescence lifetime of Eu2+. More importantly, the emission intensity is enhanced after doping Ag nanowires, and the red shift phenomenon of the emission spectrum is observed, red shift occurs between 10 and 56 nm. The highest fluorescence intensity is accessed under the Ag doping concentration of 0.10 %. Additionally, the emission of SiO2/Eu2+ with 0.10 % of Ag doping at 456 nm is 16 times stronger than that of pure SiO2/Eu2+. The present results indicate that the fluorescence enhancement is attributed to the local field enhancement and the increased radiative decay rates induced by Ag nanowires

Palladium Supported on Titanium Carbide: A Highly Efficient, Durable, and Recyclable Bifunctional Catalyst for the Transformation of 4-Chlorophenol and 4-Nitrophenol

Developing highly efficient and recyclable catalysts for the transformation of toxic organic contaminates still remains a challenge. Herein, Titanium Carbide (Ti3C2) MXene modified by alkali treatment process was selected as a support (designated as alk-Ti3C2X2, where X represents the surface terminations) for the synthesis of Pd/alk-Ti3C2X2. Results show that the alkali treatment leads to the increase of surface area and surface oxygen-containing groups of Ti3C2X2, thereby facilitating the dispersion and stabilization of Pd species on the surface of alk-Ti3C2X2. The Pd/alk-Ti3C2X2 catalyst shows excellent catalytic activity for the hydrodechlorination of 4-chlorophenol and the hydrogenation of 4-nitrophenol in aqueous solution at 25 °C and hydrogen balloon pressure. High initial reaction rates of 216.6 and 126.3 min−1· g pd − 1 are observed for the hydrodechlorination of 4-chlorophenol and hydrogenation of 4-nitrophenol, respectively. Most importantly, Pd/alk-Ti3C2X2 exhibits excellent stability and recyclability in both reactions without any promoters. The superior property of Pd/alk-Ti3C2X2 makes it as a potential material for practical applications