Synthesis and Applications of Dimensional SnS2 and SnS2/Carbon Nanomaterials.

Dimensional nanomaterials can offer enhanced application properties benefiting from their sizes and morphological orientations. Tin disulfide (SnS2) and carbon are typical sources of dimensional nanomaterials. SnS2 is a semiconductor with visible light adsorption properties and has shown high energy density and long cycle life in energy storage processes. The integration of SnS2 and carbon materials has shown enhanced visible light absorption and electron transmission efficiency. This helps to alleviate the volume expansion of SnS2 which is a limitation during energy storage processes and provides a favorable bandgap in photocatalytic degradation. Several innovative approaches have been geared toward controlling the size, shape, and hybridization of SnS2/Carbon composite nanostructures. However, dimensional nanomaterials of SnS2 and SnS2/Carbon have rarely been discussed. This review summarizes the synthesis methods of zero-, one-, two-, and three-dimensional SnS2 and SnS2/Carbon composite nanomaterials through wet and solid-state synthesis strategies. Moreover, the unique properties that promote their advances in photocatalysis and energy conversion and storage are discussed. Finally, some remarks and perspectives on the challenges and opportunities for exploring advanced SnS2/Carbon nanomaterials are presented.

Fenton-like reaction driving the degradation and uptake of multi-walled carbon nanotubes mediated by bacterium.

Carbon nanotubes (CNTs) have been widely studied because of their potential applications. The increasing applications of CNTs and less known of their environmental fates rise concerns about their safety. In this study, the biotransformation of multi-walled carbon nanotubes (MWCNTs) by Labrys sp. WJW was investigated. Within 16 days, qPCR analysis showed that cell numbers increased 4.92 ± 0.36 folds using 100 mg/L MWCNTs as the sole carbon source. The biotransformation of MWCNTs, which led to morphology and functional group change, was evidenced by transmission electron microscopy and X-ray photoelectron spectroscopy analyses. Raman spectra illustrated that more defects and disordered carbon appeared on MWCNTs during incubation. The underlying biotransformation mechanism of MWCNTs through an extracellular bacterial Fenton-like reaction was demonstrated. In this bacteria-mediated reaction, the OH production was induced by reduction of H2O2 involved a continuous cycle of Fe(II)/Fe(III). Bacterial biotransformation of MWCNTs will provide new insights into the understanding of CNTs bioremediation processes.

Enhanced antibacterial activity of acid treated MgO nanoparticles on Escherichia coli.

Acid treatment is one of the effective methods that directly modifies surface physical and chemical properties of inorganic materials, which improves the materials' application potential. In this work, the surface modified MgO nanoparticles (NPs) were prepared through a facile acid-treatment method at room temperature. Compared with the untreated sample, the surviving Escherichia coli (E. coli, ATCC 25922) colonies of the modified MgO NPs decreased from 120 to 54 (102 CFU mL-1). The enhanced antibacterial activity may be due to the improvement of oxygen vacancies and absorbed oxygen (OA) content (from 41.6% to 63.1%) as confirmed by electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS). These findings revealed that the acid treatment method could directly modify the surface of MgO NPs to expose more oxygen vacancies, which would promote reactive oxygen species (ROS) generation. The membrane tube and single ROS scavenging results further indicated that the increased antibacterial ability originated from the synergetic effect of ROS damage (especially ˙O2 -) and direct contact between H-MgO NPs and E. coli.

Biogenic fenton-like reaction involvement in aerobic degradation of C60 by Labrys sp. WJW.

Buckminster fullerene (C60), the most representative type among fullerenes, has attracted widely attentions because of its many potential applications. The increasing application of fullerene and limited knowledge of its environmental fate are required concerns. Herein, the biotransformation of C60 by Labrys sp. WJW was investigated. Cell numbers reached 25.76 ± 1.85 folds within 8 days using 100 mg/L C60 as sole carbon source. The biotransformation of C60 by Labrys sp. WJW was analyzed by various characterization methods. Raman spectra indicated that strain WJW broke the soccer ball like structure of C60. After 12 days, over 60% of C60 was degraded evidenced by UV-vis spectrophotometry and liquid chromatography-mass spectrometry. The underlying biotransformation mechanism of C60 through an extracellular Fenton-like reaction was illustrated. In this reaction, the •OH production was mediated by reduction of H2O2 involving a continuous cycle of Fe(II)/Fe(III). Bacterial transformation of C60 will provide new insights into the understanding of C60 bioremediation process.

Enhanced anti-Escherichia coli properties of Fe-doping in MgO nanoparticles.

Hetero-elements doping is an effective way to modify the composition and nanostructure of metal oxides. These modifications could lead to changes in physical and chemical properties correspondingly. In this study, Fe-doped MgO nanoparticles (NPs) were synthesized by simple calcination method in air. The antibacterial activity of MgO NPs against Escherichia coli (E. coli, ATCC 25922) was significantly improved as shown by the bactericidal efficacy test results. According to X-ray diffraction (XRD) results, Fe was successfully doped into MgO lattice and mainly adopted interstitial doping. The Fe-doping led to increased oxygen vacancies and OA content (from 13.5% to 41.3%) on MgO surface, which may have facilitated the reactive oxygen species (ROS) generation and bacteria death. The wrinkled and sunken E. coli surface after contact with Fe-doped MgO NPs also confirmed the existence of adsorption damage mechanism. Thus, the antibacterial activity enhancement against E. coli was originated from the synergistic effect of increased ROS concentration and the interaction with Fe-doped MgO NPs.

Bacteria mediated Fenton-like reaction drives the biotransformation of carbon nanomaterials.

Carbon nanomaterials (CNs), which gain heightened attention as novel materials, are increasingly incorporated into daily products and thus are released into the environment. Limited research on CNs environmental fates lags their industry growth, only few bacteria have been confirmed to biotransform CNs and the mechanism behind has not been revealed yet. In this study, four types of commercial CNs, i.e. graphene oxide (GO), reduced graphene oxide (RGO), single walled carbon nanotubes (SWCNTs), and oxidized (carboxylated) SWCNTs, were selected for investigation. The biotransformation of CNs by Labrys sp. WJW, which could grow with these CNs as the sole carbon source, was investigated. The bacterial transformation was proved by qPCR, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, liquid chromatography/time-of-flight/mass spectrometry, and gas chromatograph-mass spectrometry analyses. The biotransformation resulted in morphology change, defect increase and functional group change of these CNs. Furthermore, the underlying mechanism of CNs biodegradation mediated by extracellular Fenton-like reaction was demonstrated. In this reaction, the OH production was mediated by reduction of H2O2 involved a continuous cycle of Fe(II)/Fe(III). These findings reveal a novel degradation mechanism of microorganism towards high molecular weight substrate, which will provide a new insight into the environmental fate of CNs and the guidance for their safer use.

Characterization of biogenic selenium nanoparticles derived from cell-free extracts of a novel yeast Magnusiomyces ingens.

A facile one-pot and effective green process for biogenic selenium nanoparticles (SeNPs) was obtained using the cell-free extracts of a novel yeast Magnusiomyces ingens LH-F1. The corresponding absorption peak of SeNPs was observed at ~ 560 nm by UV-vis spectrophotometer. In the present study, SeO2 2 mM, protein 500 mg L-1 and pH 7 were preferable to the biosynthesis of SeNPs. The effects of pH, SeO2 concentration and protein concentration on the synthesis process were different. Transmission electron microscopy image exhibited that all the SeNPs were spherical and quasi-spherical with the diameters mainly distributed in 70-90 nm (average particles size was 87.82 ± 2.71 nm). X-ray diffraction suggested that the nanoparticles were composed of standard hexagonal crystalline Se with high purity. Fourier transform infrared spectroscopy indicated that some biomolecules such as hydroxyl, carboxyl and amino groups in the yeast cell-free extracts might be involved in the formation of SeNPs. Analyses of sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that two proteins with low molecular weight approximately ~ 16 and ~ 21 kDa were detected on the surface of SeNPs and in the extracts, which could play the role of natural stabilizers and confer stability to synthesized SeNPs; whereas, unbound proteins on the SeNPs surface could act as reducing agents. Antibacterial analysis showed that the SeNPs could inhibit Arthrobacter sp. W1 (Gram positive) but not E. coli BL21 (Gram negative), which could provide reference for antimicrobial application of biogenic SeNPs.