A photoenhanced oxidation of amino acids and the cross-linking of lysozyme mediated by tetrazolium salts.

Tetrazolium salts (TZs) are pervasively utilized as precursors in the dye industry, colorimetric probes in enzyme assays and for exploring nanomaterial toxicity, but its own toxicity is not investigated enough so far. Using femtosecond transient absorption spectroscopy, nanosecond pulse radiolysis (ns-PRL), western blotting and UV-vis absorption spectroscopy, here we characterized a neutral tetrazolinyl radical (with the same maximum absorption at 420 nm and different lifetimes of 5.0 and 9.0 µs for two selected TZs), the key intermediate of TZs reduction, and noticed TZs-formazan production under UV light irradiation accompanied by 41% increase in the cross-linking of lysozyme (Lyso, model protein) compared to TZs-free sample, which uncovered the photoenhanced oxidation of TZs towards Lyso. The ns-PRL in a reductive atmosphere simulated the electron/proton donors of amino acid residues in Lyso upon photoexcitation and revealed the reduction mechanism of TZs, as that first followed one-electron-transfer and then probably proton-coupled electron transfer. This is the first time to report on the photoenhanced oxidation mechanism of TZs, which would provide new insights into the applications of TZs in cell biology, "click" chemistry and nanotoxicology.

The synthesis of 3D graphene/Au composites via γ-ray irradiation and their use for catalytic reduction of 4-nitrophenol.

Graphene oxide (GO) and gold ions (Au3+) can be simultaneously reduced and self-assembled into a three-dimensional (3D) graphene/Au composite (GA/Au) porous structure at room temperature via one-step γ-ray irradiation. The microstructure of GA/Au composites were observed under different magnifications and the pores were observed to be uniform 3D porous structure. In addition, Au nanoparticles were homogeneously attached to graphene sheets and had a typical diameter of 6 nm. These GA/Au composites were analyzed and characterized by x-ray diffraction analysis, x-ray photoelectron spectroscopy, and thermal gravity analysis. Due to synergistic catalysis between graphene and Au nanoparticles, GA/Au composites catalyzed 4-nitrophenol with excellent catalytic performance, even at concentrations up to 6.48 × 10-3 M. When the concentration of 4-nitrophenol was 2.16 × 10-3 M and 4.22 × 10-3 M, the first-order kinetic constants were 2.00 and 1.43 min-1, respectively.

Ion sieving in graphene oxide membranes via cationic control of interlayer spacing.

Graphene oxide membranes-partially oxidized, stacked sheets of graphene-can provide ultrathin, high-flux and energy-efficient membranes for precise ionic and molecular sieving in aqueous solution. These materials have shown potential in a variety of applications, including water desalination and purification, gas and ion separation, biosensors, proton conductors, lithium-based batteries and super-capacitors. Unlike the pores of carbon nanotube membranes, which have fixed sizes, the pores of graphene oxide membranes-that is, the interlayer spacing between graphene oxide sheets (a sheet is a single flake inside the membrane)-are of variable size. Furthermore, it is difficult to reduce the interlayer spacing sufficiently to exclude small ions and to maintain this spacing against the tendency of graphene oxide membranes to swell when immersed in aqueous solution. These challenges hinder the potential ion filtration applications of graphene oxide membranes. Here we demonstrate cationic control of the interlayer spacing of graphene oxide membranes with ångström precision using K+, Na+, Ca2+, Li+ or Mg2+ ions. Moreover, membrane spacings controlled by one type of cation can efficiently and selectively exclude other cations that have larger hydrated volumes. First-principles calculations and ultraviolet absorption spectroscopy reveal that the location of the most stable cation adsorption is where oxide groups and aromatic rings coexist. Previous density functional theory computations show that other cations (Fe2+, Co2+, Cu2+, Cd2+, Cr2+ and Pb2+) should have a much stronger cation-π interaction with the graphene sheet than Na+ has, suggesting that other ions could be used to produce a wider range of interlayer spacings.

Photo-enhanced oxidizability of tetrazolium salts and its impact on superoxide assaying.

Herein, we report for the first time the enhanced oxidation properties of tetrazolium salts induced by UV-irradiation, and demonstrate that there is real deviation in the photo-induced superoxide anion radical assay based on tetrazolium salts.

Antisuperbug Cotton Fabric with Excellent Laundering Durability.

Multidrug-resistant superbugs are currently a severe threat to public health. Here, we report a novel kind of antisuperbug material prepared by irradiation induced graft polymerization of 1-butyl-3-vinyl imidazole chloride onto cotton fabric. The reduction of superbugs on this fabric is higher than 99.9%. Attributed to the strong covalent bonding between the graft chains and the cellulose macromolecules, the antisuperbug performance did not decrease even after 150 equiv of domestic laundering cycles. Covalent bonding also prevented the release of the antibacterial groups during application and guarantees the safety of the material, which was proved by animal skin irritation and acute oral toxicity tests.

Covalent immobilization of metal-organic frameworks onto the surface of nylon--a new approach to the functionalization and coloration of textiles.

The prevention of refractory organic pollution caused by conventional dyeing and the development of new fabrics with various functions are two issues to be solved urgently in the field of textile fabrication. Here, we report a new environmentally friendly route for the simultaneous coloration and functionalization of textiles by the covalent immobilization of a metal-organic framework, Cr-based MIL-101(Cr), onto the surfaces of nylon fabrics by co-graft polymerization with 2-hydroxyethyl acrylate initiated by γ-ray irradiation. The Cr(III) clusters color the nylon fabric, and the color intensity varies with the MIL-101 content, providing a "green" textile coloration method that is different from conventional dyeing processes. An X-ray diffraction (XRD) analysis shows that the nanoporous structure of the original MIL-101 particles is retained during radiation-induced graft polymerization. Numerous nanopores are introduced onto the surface of the nylon fabric, which demonstrated better sustained-release-of-aroma performance versus pristine nylon fabric in tests. The modified fabrics exhibit laundering durability, with MIL-101 nanoparticles intact on the nylon surface after 30 h of dry cleaning.

Graphene Oxide Transparent Hybrid Film and Its Ultraviolet Shielding Property.

Herein, we first reported a facile strategy to prepare functional Poly(vinyl alcohol) (PVA) hybrid film with well ultraviolet (UV) shielding property and visible light transmittance using graphene oxide nanosheets as UV-absorber. The absorbance of ultraviolet light at 300 nm can be up to 97.5%, while the transmittance of visible light at 500 nm keeps 40% plus. This hybrid film can protect protein from UVA light induced photosensitive damage, remarkably.

Electrical Switchability and Dry-Wash Durability of Conductive Textiles.

There is growing interest in the area of conductive textiles in the scientific and industrial community. Herein, we successfully prepared a conductive textile via covalently grafting polyaniline (PANI) onto cotton by a multi-step treatment process. The conductivity of the resultant fabric could be tuned by immersing in water having different pH values. The conductive and insulating properties of the textile could be conveniently switched by alternately immersing in acidic and alkaline bath solutions. Most importantly, the resultant conductive fabrics were able to withstand 40 simulated dry-wash cycles, with almost no decay in the electrical conductivity, indicating their excellent dry-wash durability. The present strategy for fabricating conductive fabrics with excellent switchability of electrical properties and dry-wash durability is expected to provide inspiration for the production of multifunctional conductive textiles for use in hash or sensitive conditions.

Novel multifunctional nanofibers based on thermoplastic polyurethane and ionic liquid: towards antibacterial, anti-electrostatic and hydrophilic nonwovens by electrospinning.

Novel antibacterial, anti-electrostatic, and hydrophilic nanofibers based on a blend containing thermoplastic polyurethane (TPU) and a room-temperature ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], were fabricated by electrospinning. We investigated the effect of the IL on the morphology and the physical properties of the TPU nanofibers. Nanofibers with a 'bead-on-string' morphology were obtained by electrospinning from a neat TPU solution. The incorporation of the IL, at levels as low as 1 wt%, largely suppressed the formation of beads during electrospinning, and homogeneous nanofibers were obtained. The as-spun TPU/IL composite nanofibers showed significant activity against both Escherichia coli (E coli) and Staphylococcus aureus (S. aureus), with antibacterial activities of more than four and three, respectively. This means that the antibacterial efficiencies of TPU/IL composite nanofibers toward E coli and S. aureus are 99.99% and 99.9%, respectively. Moreover, nonwoven fabrics derived from the electrospun TPU/IL composite nanofibers exhibit better stretchability, elasticity, and higher electrical conductivity compared to those made using neat TPU without an IL. Additionally, the incorporation of the IL leads to a hydrophilic surface for the TPU/IL composite nanofibers compared to hydrophobic neat TPU nanofibers. These multifunctional nanofibers with excellent antibacterial, anti-electrostatic, and mechanical properties and improved hydrophilicity are promising candidates for biomedical and wastewater treatment applications.

Building up graphene-based conductive polymer composite thin films using reduced graphene oxide prepared by γ-ray irradiation.

In this paper, reduced graphene oxide (RGO) was prepared by means of γ -ray irradiation of graphene oxide (GO) in a water/ethanol mix solution, and we investigated the influence of reaction parameters, including ethanol concentration, absorbed dose, and dose rate during the irradiation. Due to the good dispersibility of the RGO in the mix solution, we built up flexible and conductive composite films based on the RGO and polymeric matrix through facile vacuum filtration and polymer coating. The electrical and optical properties of the obtained composite films were tested, showing good electrical conductivity with visible transmittance but strong ultraviolet absorbance.

Preparation of polymer decorated graphene oxide by γ-ray induced graft polymerization.

Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by γ-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes.