Microwave-assisted synthesis of defective tungsten trioxide for photocatalytic bacterial inactivation:Role of the oxygen vacancy

Surface defect modulation has emerged as a potential strategy for promoting the photocatalytic activity of photocatalysts for various applications, while the impact of the oxygen vacancy on bacterial inactivation is still debated. In this study, oxygen vacancies were introduced to tungsten trioxide nanosheets(WO3–x) via a microwave-assisted route. The as-prepared WO3–x nanosheets exhibited excellent visible-light-driven photocatalytic activity toward E. coli K-12 inactivation, and 6 log orders of the bacterial cells could be completely inactivated within 150 min. The obtained bacterial inactivation rate constant was 15.2 times higher than that of pristine WO3 without oxygen vacancies, suggesting that the surface oxygen vacancy could significantly promote the bacterial inactivation efficiency. The mechanism study indicated that the inactivation of bacterial cells occurs via a direct h+ oxidation pathway. In addition, the role of the oxygen vacancy was studied in detail;the oxygen vacancy was found to not only promote interfacial charge separation but also tune the band structure of WO3, thereby leading to increased h+ oxidation power. Finally, a possible oxygen vacancy-dominated photocatalytic bacterial inactivation mechanism is proposed. This work is expected to offer new insights into the microwave-assisted synthesis of defective photocatalysts and the use of the oxygen vacancy for promoting photocatalytic antibacterial activities.

Immune response to inactivated bacterial vector carrying the recombinant K39 antigen of Leishmania infantum in mice

Objective:To evaluate the immunological response elicited by an inactivated bacterial vector carrying the K39 antigen of Leishmania infantum,and a purified antigen.Methods:Mice were subjected to the following treatments:(1)Purified recombinant K39(rK39)protein at a 20μg dose with complete Freund’s adjuvant;(2)Inactivated Escherichia coli(BL21 DE3)carrying the K39 protein at an equivalent total protein content of 200μg;(3)Inactivated bacteria lacking the K39 protein;(4)Non-immunized control animals.Serological monitoring was performed.All groups were challenged by intraperitoneal injection of 10^(7) Leishmania infantum promastigotes.After euthanasia,the liver and spleen were collected to analyze the levels of TNF,IFN-γ,IL-12,IL-4,and IL-10.Results:Mice immunized with purified rK39 or the inactivated bacterial vector carrying the K39 antigen of Leishmania infantum showed a long-lasting immune response with high levels of polyclonal antibodies specifically recognizing the recombinant proteins.The IgG1 subclass was the predominant immunoglobulin;however,the induction of IgG2a and the profile of cytokines produced were indicative of the induction of a mixed-type response.Conclusions:The inactivated bacterial vector carrying the K39 antigen,as well as the purified antigen can induce a long-lasting immune response in immunized mice,predominantly favouring a Th2 profile response.

Surface diffuse discharge mechanism of well-aligned atmospheric pressure microplasma arrays

A stable and homogeneous well-aligned air microplasma device for application at atmospheric pressure is designed and its electrical and optical characteristics are investigated. Current-voltage measurements and intensified charge coupled device （ICCD） images show that the well-aligned air microplasma device is able to generate a large-area and homogeneous discharge at the applied voltages ranging from 12 kV to 14 kV, with a repetition frequency of 5 kHz, which is attributed to the diffusion effect of plasma on dielectric surface. Moreover, this well-aligned microplasma device may result in the uniform and large-area surface modification of heat-sensitive PET polymers without damage, such as optimization in hydrophobicity and biocompatibility. In the biomedical field, the utility of this well-aligned microplasma device is further testified. It proves to be very efficient for the large-area and uniform inactivation of E. coli cells with a density of 103/cm2 on LB agar plate culture medium, and inactivation efficiency can reach up to 99% for 2-min treatment.

Development of a battery-operated floating-electrode dielectric barrier discharge plasma device and its characteristics

In this work,a portable floating-electrode dielectric barrier discharge(FE-DBD)device is designed with a rechargeable battery as the power supply.The characteristics of the FE-DBD with a metal electrode and human hand are studied and compared.The human contact safety is verified by calculating the current through the human body based on the equivalent circuit model.Escherichia coli inactivation experiments confirm the efficacy of the FE-DBD device in the envisaged applications.

Preparation of Ag-MnFe204-bentonite Magnetic Composite for Pb（II）/Cd（II） Adsorption Removal and Bacterial Inactivation in Wastewater

An Ag-MnFe2O4-bentonite composite was synthesized by a chemical co-precipitation method and used for adsorption removal of Pb（II）, Cd（II） and disinfection. The result of X-ray diffraction indicate that the diffraction peaks of MnFe2O4 and Ag can be perfectly indexed to the cubic spinel MnFe2O4（JCPDS No.88-1965） and metallic Ag（JCPDS No.41-1402）, respectively. The results of scanning electron microscopy and energy dispersive X-ray spectroscopy manifest the deposition of MnFe2O4 and Ag on the bentonite surface and the presence ofMn, Fe and Ag. The result of X-ray photoelectron spectroscopy displayed that the composition of Ag-MnFe2O4-bentonite was Mn（II）, Fe（III） and metallic Ag. The analysis of Brunauer-Emmett-Teller showed that the specific surface area of Ag-MnFe2O4-bentonite was the largest compared with that of bentonite, MnFe2O4 and MnFe2O4-bentonite. Thermo- dynamic studies revealed that the adsorption of Pb（II） and Cd（II） ions was spontaneous and endothermic. Langmuir model showed an adsorption capacity of 129.87 mg/g for Pb（II） and 48.31 mg/g for Cd（II） ions. The adsorption ki- netics of Pb（II） and Cd（II） ions onto Ag-MnFe2O4-bentonite can be best described by a pseudo-second-order model. The adsorption rate constant of the pseudo-second-order model was 0.0019 g·mg^-1·min^-1 for Pb（II） and 0.0065 g·mg^-1·min^-1 for Cd（II） ions. In addition to the adsorption experiment, the antibacterial properties of Ag-MnFe2O4-bentonite were studied through plate count method. Gram-negative（G-） bacteria Escherichia coli and Gram-positive（G＋） bacteria Lactobacillus plantarum were used to test the antibacterial properties. The results showed that the composite demonstrated excellent antibacterial activity. Thus, Ag-MnFe2O4-bentonite can be em- ployed as an adsorbent as well as an antimicrobial agent.

Effective E.coli inactivation of core-shell ZnO@ZIF-8 photocatalysis under visible light synergize with peroxymonosulfate:Efficiency and mechanism

How to utilize inexhaustible solar light as a means of disinfection technology for its cheap and green remains a challenge.In this work,core-shell ZnO@ZIF-8 was synthesized and used for bacterial inactivation synergizing with peroxymonosulfate(PMS)under visible light irradiation.It took 50 min to achieve thorough sterilization for 7.5-log Escherichia coli(E.coli)cells in vis/PMS/ZnO@ZIF-8 system,compared with that 4.5-log reduction completed in vis/PMS/ZnO system under the same conditions.The enhanced photocatalytic disinfection mechanisms of fabricated ZnO@ZIF-8 were investigated by UV-vis diffuse reflectance spectra,electrochemical impedance spectra and Mott-Schottky plots.The promoted bactericidal efficiency was attributed to higher charge-separation efficiency and stronger oxidation ability of photo-generated holes.Moreover,it was found that^(1)O_(2)and·OH induced bacterial cell lesion process,and the former was the main active species.The external reactive oxygen species(ROS)caused a series of cell wall damage,intercellular ROS up-regulation and genome DNA unwinding,finally resulted in irreversible bacterial death.A two-route mechanism in vis/PMS/ZnO@ZIF-8 system was proposed,in which the generation of^(1)O_(2)was supposed as the product of the oxygen oxidation of photo-generated holes and PMS dissociation.Our work is expected to provide advanced information about a low-cost water disinfection technology of visible light photocatalysis.

Bacteria inactivation by sulfate radical:progress and non-negligible disinfection by-products

Sulfate radicals have been increasingly used for the pathogen inactivation due to their strong redox ability and high selectivity for electron-rich species in the last decade.The application of sulfate radicals in water disinfection has become a very promising technology.However,there is currently a lack of reviews of sulfate radicals inactivated pathogenic microorganisms.At the same time,less attention has been paid to disinfection by-products produced by the use of sulfate radicals to inactivate microorganisms.This paper begins with a brief overview of sulfate radicals’properties.Then,the progress in water disinfection by sulfate radicals is summarized.The mechanism and inactivation kinetics of inactivating microorganisms are briefly described.After that,the disinfection by-products produced by reactions of sulfate radicals with chlorine,bromine,iodide ions and organic halogens in water are also discussed.In response to these possible challenges,this article concludes with some specific solutions and future research directions.

Promising graphdiyne-based nanomaterials for environmental pollutant control

ABSTRACT Environmental pollutants,including gas phase pollutants,liquid organic pollutants,heavy metal ions,and pathogenic bacteria,pose a serious threat to our ecological environment and human health.Effectively addressing these pollutants has become one of the most urgent issues.Graphdiyne(GDY),as an emerging carbon material for environmental remediation,has unique acetylene bonds and abundant pore structures.The unique carbon atomic structure of sp/sp2 hybrid endows it with tunable electronic structure and outstanding physical and chemical properties.This review summarizes the practical applications of GDY-based nanomaterials in the context of environmental pollution control,including carbon monoxide(CO)oxidation,ozone(O_(3))decomposition,heavy metal ion detection and adsorption,organic pollutant degradation,and bacterial inactivation.Furthermore,the structure-performance relationship of GDYbased nanomaterials is analyzed,and the issues and challenges in the field of environmental remediation of GDY-based materials are indicated.

Characterization and Photocatalytic Efficiency of TiO_2 /Ti Beads Fabricated by Simple Heat-Treatment

The goal of the present study was to investigate the photocatalytic efficiency of titanium dioxide （TiO2） formed on titanium （Ti） bead substrate （referred herein as TiO2/Ti beads） by heat treatment when exposing to ultraviolet （UV） light irradiation. Escherichia coli was used as the model test organism. The results show 4-log and 7-log decrease in bacterial concentration after a test time of 15 and 120 min, respectively, using TiO2/Ti beads irradiated with UV light in a tin-foil covered beaker. This article presents the potential of TiO2 on Ti bead substrate formed by simple heat-treatment together with UV light for bacterial inactivation.