Degradation of tetracycline in water by gas-liquid plasma in conjunction with rGO-TiO_(2) nanocomposite

Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas–liquid plasma in the presence of rGO-TiO_(2)in solution.The rGO-TiO_(2)was prepared by modified hummers and hydrothermal method.The electrical and optical properties of the gas–liquid discharge plasma were studied and the produced long-lived reactive species were analyzed by spectrophotometer.The degradation efficiency of TC was improved by 41.4%after plasma treatment for 12 min in presence of 30 mg l-1 r GO-TiO_(2)compared to that with plasma alone.The degradation efficiency increased with increasing discharge power,but as the initial concentration was increased from 20 to 80 mg l-1,the degradation efficiency of TC decreased.The initial p H had no significant effect on the degradation of TC.The intermediate products were determined by UV–vis spectrophotometry and ESI(+)–MS,and the degradation mechanism was analyzed.The reactive species,including O_(3),·OH,and H_(2)O_(2),etc.,produced in the plasma/catalyst system attracted electron-rich functional groups(amino group,aromatic ring,and double bond).Therefore,the gas–liquid plasma/catalyst system could be an effective and promising method for pharmaceutical wastewater treatment in future.

Control of multidrug-resistant planktonic Acinetobacter baumannii:biocidal efficacy study by atmospheric-pressure air plasma

In this research,an atmospheric-pressure air plasma is used to inactivate the multidrug-resistant Acinetobacter baumannii in liquid.The efficacy of the air plasma on bacterial deactivation and the cytobiological variations after the plasma treatment are investigated.According to colony forming units,nearly all the bacteria（6-log） are inactivated after 10 min of air plasma treatment.However,7% of the bacteria enter a viable but non-culturable state detected by the resazurin based assay during the same period of plasma exposure.Meanwhile,86% of the bacteria lose their membrane integrity in the light of SYTO 9/PI staining assay.The morphological changes in the cells are examined by scanning electron microscopy and bacteria with morphological changes are rare after plasma exposure in the liquid.The concentrations of the long-living RS,such as H2O2,NO3^- and O3,in liquid induced by plasma treatment are measured,and they increase with plasma treatment time.The changes of the intracellular ROS may be related to cell death,which may be attributed to oxidative stress and other damage effects induced by RS plasma generated in liquid.The rapid and effective bacteria inactivation may stem from the RS in the liquid generated by plasma and air plasmas may become a valuable therapy in the treatment of infected wounds.

Engineering the axial coordination of cobalt single atom catalysts for efficient photocatalytic hydrogen evolution

Improving the catalytic activity of non-noble metal single atom catalysts(SACs)has attracted considerable attention in materials science.Although optimizing the local electronic structure of single atom can greatly improve their catalytic activity,it often involves in-plane modulation and requires high temperatures.Herein,we report a novel strategy to manipulate the local electronic structure of SACs via the modulation of axial Co-S bond anchored onto graphitic carbon nitride(C_(3)N_(4))at room temperature(RT).Each Co atom is bonded to four N atoms and one S atom(Co-(N,S)/C_(3)N_(4)).Owing to the greater electronegativity of S in the Co-S bond,the local electronic structure of the Co atoms is available to be controlled at a relatively moderate level.Consequently,when employed for the photocatalytic hydrogen evolution reaction,the adsorption energy of intermediate hydrogen(H*)on the Co atoms is remarkably low.In the presence of the Co-(N,S)/C_(3)N_(4)SACs,the hydrogen evolution rates reach up to 10 mmol/(g·h),which is nearly 10 and 2.5 times greater than the rates in the presence of previously reported transition metal/C_(3)N_(4)and noble platinum nanoparticles(PtNPs)/C_(3)N_(4)catalysts,respectively.Attributed to the tailorable axial Co-S bond in the SAC,the local electronic structure of the Co atoms can be further optimized for other photocatalytic reactions.This axial coordination engineering strategy is universal in catalyst designing and can be used for a variety of photocatalytic applications.

High-performance asymmetrical supercapacitor composed of rGO-enveloped nickel phosphite hollow spheres and N/S co-doped rGO aerogel

An asymmetrical supercapacitor （ASC）, comprising reduced graphene oxide （rGO）-encapsulated nickel phosphite hollow microspheres （NPOH-0.5@rGO） as positive electrode, and porous nitrogen/sulfur co-doped rGO aerogel （NS-3D rGO） as negative electrode has been prepared. The NPOH-0.5@rGO electrode combines the advantages of the NPOH hollow microspheres and the conductive rGO layers giving rise to a large specific capacitance, high cycling reversibility, and excellent rate performance. The NS-3D rGO electrode with abundant porosity and active sites promotes electrolyte infiltration and broadens the working voltage range. The ASC （NPOH-0.5@rGO//NS-3D rGO） shows a maximum voltage of up to 1.4 V, outstanding cycling ability （capacitance retention of 95.5% after 10,000 cycles）, and excellent rate capability （capacitance retention of 77% as the current density is increased ten times）. The ASC can light up an light-emitting diodes （LED） for more than 20 min after charging for 20 s. The fabrication technique and device architecture can be extended to other active oxide and carbon-based materials for next-generation high-performance electrochemical storage devices.

Computational design of bimetallic core-shell nanoparticles for hot-carrier photocatalysis

Computational design can accelerate the discovery of new materials with tailored properties,but applying this approach to plasmonic nanoparticles with diameters larger than a few nanometers is challenging as atomistic first-principles calculations are not feasible for such systems.In this paper,we employ a recently developed material-specific approach that combines effective mass theory for electrons with a quasistatic description of the localized surface plasmon to identify promising bimetallic core-shell nanoparticles for hot-electron photocatalysis.Specifically,we calculate hot-carrier generation rates of 100 different core-shell nanoparticles and find that systems with an alkali-metal core and a transition-metal shell exhibit high figures of merit for water splitting and are stable in aqueous environments.Our analysis reveals that the high efficiency of these systems is related to their electronic structure,which features a two-dimensional electron gas in the shell.Our calculations further demonstrate that hotcarrier properties are highly tunable and depend sensitively on core and shell sizes.The design rules resulting from our work can guide experimental progress towards improved solar energy conversion devices.

Frontier orbitals and quasiparticle energy levels in ionic liquids

Ionic liquids play an important role in many technological applications and a detailed understanding of their frontier molecular orbitals is required to optimize interfacial barriers,reactivity and stability with respect to electron injection and removal.In this work,we calculate quasiparticle energy levels of ionic liquids using first-principles many-body perturbation theory within the GW approximation and compare our results to various mean-field approaches,including semilocal and hybrid density-functional theory and Hartree-Fock.We find that the mean-field results depend qualitatively and quantitatively on the treatment of exchange-correlation effects,while GW calculations produce results that are in excellent agreement with experimental photoelectron spectra of gas phase ion pairs and ionic liquids.These results establish the GW approach as a valuable tool for understanding the electronic structures of ionic liquids.