Quantitative monitoring ofloxacin in beef by TLC-SERS combined with machine learning analysis.

Ofloxacin is one kind of quinolone antibiotic drugs, the abuse of ofloxacin in livestock and aquaculture may bring bacterial resistance and healthy problem of people. The illegally feeding cattle with ofloxacin will help it keep health, but the sedimentation of ofloxacin could bring problem in food safety. The accurate, simple and instant monitoring ofloxacin from beef by portable sensor was of vital issue in food quality. A simple and reliable method was proposed for instant and quantitative detecting ofloxacin in beef, in which the thin-layer chromatography (TLC) -surface-enhanced Raman scattering (SERS) spectroscopy was in tandem with machine learning analysis base one principal component analysis-back propagation neural network (PCA-BPNN). The TLC plate was composed with diatomite, that was function as the stationary phase to separate ofloxacin from beef. The real beef juice was directly casted onto the diatomite plate for separating and detecting. The directly monitor ofloxacin from beef was achieved and the sensitivity down to 0.01 ppm. The PCA-BPNN was used as reliable model for quantitative predict the concentration of ofloxacin, that shown superior accuracy compared with the traditional model. The results verify that the diatomite plate TLC-SERS combined with machine-learning analysis is an effective, simple and accurate technique for detecting and quantifying antibiotic drug in meat stuff to improve the food safety.

Rapid, convenient, and ultrasensitive point-of-care sensing of histamine from fish: A Portable chromatographic platform based on derivatization reaction.

Food poisoning caused by histamine ingestion is one of the prevalent allergies associated with fish consumption in the world. Reliable detection of histamine from fish by a portable platform was of urgent importance to food safety. A portable technology for on-site monitoring of histamine in tuna was established through combined azo-derivatized thin-layer chromatography (TLC) with surface-enhanced Raman scattering (SERS) spectroscopy. The real tuna meat sample was directly applied onto the portable sensor for the separation of histamine and azo-derivatizing of histamine was reacted on the TLC plate. The colorless histamine was visualized by azo-derivatization after spraying Pauly reagent onto the diatomite TLC plate. The molecule information and concentration of the histamine was measured and calculated by SERS spectra. Diatomite TLC plate was capable of separating histamine with 1.32 × 10-7 M of Au colloid for the SERS enhancement. Accordingly, the limit of detection of histamine from mixture sample could achieve 2.8 × 10-4 ppm. These results indicated that the portable azo-derivatized TLC-SERS sensor not only visualizes the histamine but also improves the intensity of the Raman spectra. The azo-derivatized TLC-SERS sensor could be applied for rapid, convenient, and ultrasensitive point-of-care sensing of histamine in fish.

Suppress Loss of Polysulfides in Lithium-Sulfur Battery by Regulating the Rate-Determining Step via 1T MoS2-MnO2 Covering Layer.

The commercialization of lithium-sulfur batteries (LSBs) is obstructed by several technical challenges, the most severe of which is the irreversible loss of soluble polysulfide intermediates. These soluble polysulfides must be anchored or confined in the cathode side to maintain the long life of the LSBs. Here, 1T MoS2-MnO2/CC heterostructure functional covering layer is designed to regulate the rate-determining step from the liquid-to-solid reaction to solid-to-solid reaction. Rapid and uniform nucleation of solid Li2S2/Li2S is therefore achieved, and the loss of soluble polysulfides is retarded. The Li-S batteries assembled with 1T MoS2-MnO2/CC covering layer therefore deliver outstanding rate capabilities even under high sulfur loads and large current rates. This study paves a novel way to suppress the polysulfides' "farewell effect" from the perspective of the kinetics.

Platinum-Water Interaction Induced Interfacial Water Orientation That Governs the pH-Dependent Hydrogen Oxidation Reaction.

Understanding the electrode-water interface structure in acid and alkali is crucial to unveiling the underlying mechanism of pH-dependent hydrogen oxidation reaction (HOR) kinetics. In this work, we construct the explicit Pt(111)-H2O interface models in both acid and alkali to investigate the relationship between the HOR mechanism and electrode-electrolyte interface structure using ab initio molecular dynamics and density functional theory. We find that the interfacial water orientation in the outer Helmholtz layer (OHP) induced by the Pt-water interaction governs the pH-dependent HOR kinetics on Pt(111). In alkali, the strong Pt-interfacial water electrostatic interaction behaves as a narrow OHP, which increases the proportion of "H-down" interfacial water and leads to less adsorbed water entering the inner Helmholtz plane (IHP), decreasing the work function of Pt(111). Furthermore, the more "H-down" interfacial water stabilizes the Had adsorption, prevents Had desorption, and suppresses the Volmer step of HOR by forming the solvated [Had···H2O···H2O] complex. Our work provided a visualized molecular-level mechanism to understand the nature of pH-dependent HOR kinetics.

Removing miscellaneous heavy metals by all-in-one ion exchange-nanofiltration membrane.

The composition of wastewater containing heavy metal mixtures is often complex and poses a serious threat to human and environmental health. Effective removal of a variety of heavy metal ions with a single technology is challenging, and the conventional split integrated technologies require multi-step processing and a massive footprint. For the first time, we achieve hierarchically integrating ion exchange and nanofiltration into all-in-one "iNF" membranes. The iNF membrane has a hierarchical structure with an interfacial polymerization layer and an ion exchange layer, which can achieve highly efficient indiscriminate heavy metal ion removal, overcoming the defect that traditional nanofiltration membranes can only remove single metal cations or oxyanions. The ion exchange layer can remove heavy metal ions through sulfonic acid groups and quaternary amine groups. In addition, the ion exchange layer can be regenerated by electro-deionization, which is meaningful for sustainable membrane usage. This facile, scalable, and compact integrated process shows outstanding potential and universal applicability in complex wastewater treatment.

Interfacial Water Enrichment and Reorientation on Pt/C Catalysts Induced by Metal Oxides Participation for Boosting the Hydrogen Evolution Reaction.

State-of-the-art hydrogen evolution reaction (HER) catalysts have been Pt- or Pt-based alloys so far due to their extremely low onset potential; however, their HER kinetics become worse under strong cathodic polarization. Herein, we take commercial Pt/C decorated with a small amount of metal oxides (MOx-Pt/C) as model catalysts to improve the HER kinetics at a wide cathodic potential range in alkaline conditions. The MOx-Pt/C catalysts markedly reduce the Tafel slope and overpotential under both small and large cathodic polarization. Multiscale simulations reveal that the metal oxides can cause a so-called local electric field enhancement and induce interfacial water enrichment and reorientation. It accelerates the diffusion of hydrated K+ and facilitates the activation of interfacial water, which boosts the Volmer step to match the fast H2 evolution especially under strong potential polarization. Our work discloses important clues about how multiple components play a role in HER electrocatalysis.

A Facile Strategy to Enhance the Dielectric and Mechanical Properties of MWCNTs/PVDF Composites with the Aid of MMA-co-GMA Copolymer.

A facile strategy is adopted to prepare carboxylic functionalized multiwalled carbon nanotube (c-MWCNT) modified high dielectric constant (high-k) poly(vinylidene fluoride) (PVDF) composites with the aid of methyl methacrylate-co-glycidyl methacrylate copolymer (MG). The MG is miscible with PVDF and the epoxy groups of the copolymer can react with the carboxylic groups of c-MWCNT, which induce the uniform dispersion of c-MWCNT and a form insulator layer on the surface of c-MWCNT. The c-MWCNTs/MG/PVDF composites with 8 vol % c-MWCNT present excellent dielectric properties with high dielectric constant (~448) and low dielectric loss (~2.36) at the frequency of 1 KHz, the dielectric loss is much lower than the c-MWCNT/PVDF composites without MG. The obvious improvement in dielectric properties ascribes to the existence of MG, which impede the direct contact of c-MWCNTs and PVDF and avoid the formation of conductive network. Therefore, we propose a practical and simple strategy for preparing composites with excellent dielectric properties, which are promising for applications in electronics devices.