Wiyong Kangwansupamonkon

Determination of silver nanoparticle release from antibacterial fabrics into artificial sweat

Silver nanoparticles have been used in numerous commercial products, including textiles, to prevent bacterial growth. Meanwhile, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects on humans as well as the environment. This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated. The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight. The quantity of silver released from the different fabrics was likely to be dependent on the amount of silver coating, the fabric quality and the artificial sweat formulations including its pH. This study is the unprecedented report on the release of silver nanoparticles from antibacterial fabrics into artificial sweat. This information might be useful to evaluate the potential human risk associated with the use of textiles containing silver nanoparticles.

Antibacterial effect of apatite-coated titanium dioxide for textiles applications.

An antibacterial activity of apatite-coated titanium dioxide (TiO2) against four types of bacteria (Staphylococcus aureus, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), and Micrococcus luteus) was investigated. Its antibacterial performance was observed under black light, visible light, and dark conditions. The number of viable bacteria decreased with irradiation time and became most prominent at 24 hours. Distortion of bacterial cells by the nanoparticles was demonstrated by scanning electron microscopy. Apatite-coated TiO2 was fixed on cotton textiles by dip-coat technique, and the antimicrobial properties of corresponding fabrics were then investigated. The effect of irradiation source on antimicrobial activity of coated cotton fabrics was examined, wherein black-light irradiation demonstrated higher antibacterial activity than either visible-light irradiation or dark conditions. Microbial populations of coated cotton fabrics decreased with increasing irradiation intensity. Coated cotton fabrics have been shown to be nontoxic to human dermal fibroblasts. Our findings suggest that the presence of apatite-coated TiO2 shows antibacterial activity in the presence of black light or visible light, suggesting its potential use in reducing the risk of microorganism transmission for textile applications.

Photocatalytic Mineralization of Organic Acids over Visible-Light-Driven Au/BiVO4 Photocatalyst

Au/BiVO4 visible-light-driven photocatalysts were synthesized by coprecipitation method in the presence of sodium dodecyl benzene sulfonate (SDBS) as a dispersant. Physical characterization of the obtained materials was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), UV-Vis diffuse reflectance spectroscopy (DRS) and Brunauer, and Emmett and Teller (BET) specific surface area measurement. Photocatalytic performances of the as-prepared Au/BiVO4 have also been evaluated via mineralizations of oxalic acid and malonic acid under visible light irradiation. XRD and SEM results indicated that Au/BiVO4 photocatalysts were of almost spherical particles with scheelite-monoclinic phase. Photocatalytic results showed that all Au/BiVO4 samples exhibited higher oxalic acid mineralization rate than that of pure BiVO4, probably due to a decrease of BiVO4 band gap energy and the presence of surface plasmon absorption upon loading BiVO4 with Au as evidenced from UV-Vis DRS results. The nominal Au loading amount of 0.25 mol% provided the highest pseudo-first-order rate constant of 0.0487 min−1 and 0.0082 min−1 for degradations of oxalic acid (C2) and malonic acid (C3), respectively. By considering structures of the two acids, lower pseudo-first-order rate constantly obtained in the case of malonic acid degradation was likely due to an increased complexity of the degradation mechanism of the longer chain acid.

Composite Photocatalysts Containing BiVO4 for Degradation of Cationic Dyes

The creation of composite structures is a commonly employed approach towards enhanced photocatalytic performance, with one of the key rationales for doing this being to separate photoexcited charges, affording them longer lifetimes in which to react with adsorbed species. Here we examine three composite photocatalysts using either WO3, TiO2 or CeO2 with BiVO4 for the degradation of model dyes Methylene Blue and Rhodamine B. Each of these materials (WO3, TiO2 or CeO2) has a different band edge energy offset with respect to BiVO4, allowing for a systematic comparison of these different arrangements. It is seen that while these offsets can afford beneficial charge transfer (CT) processes, they can also result in the deactivation of certain reactions. We also observed the importance of localized dye concentrations, resulting from a strong affinity between it and the surface, in attaining high overall photocatalytic performance, a factor not often acknowledged. It is hoped in the future that these observations will assist in the judicious selection of semiconductors for use as composite photocatalysts.

The effect of iron doping on the photocatalytic activity of a Bi2WO6–BiVO4 composite

Visible-light-driven Fe-doped Bi2WO6–BiVO4 composites have been synthesized via a hydrothermal method with varying nominal iron contents in the range of 0.5–5.0 mol%. The physicochemical properties of the obtained materials were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET)-specific surface area, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and photoluminescence (PL) techniques. Methylene blue (MB) as probe pollutant was adopted to investigate the photocatalytic activity of all samples under visible light irradiation. The Fe-doped Bi2WO6–BiVO4 composites showed an enhanced photocatalytic activity for the degradation of MB under visible light, which was attributed to the iron ions acting as good electron and hole traps for facilitating the separation of charge carriers. Simultaneously, the high stability of the sample was also investigated by five successive photodegradation tests of MB under visible light. The relationship between the photocatalytic activities and the structures of Fe-doped Bi2WO6–BiVO4 composites was discussed. The possible photocatalytic mechanism of the composites was proposed to guide the further improvement of their photocatalytic performance.

Synthesis and Characterization of a Magnetically Separable CoFe2O4/TiO2 Nanocomposite for the Photomineralization of Formic Acid

A CoFe2O4/TiO2 nanocomposite was successfully synthesized by coupling the modified sol-gel with hydrothermal techniques. The obtained CoFe2O4/TiO2 nanocomposite was characterized by X-ray diffraction for phase composition and crystallinity. TEM images revealed that the shape of the as prepared samples was almost spherical and the average particle sizes were found to be in the range of 5–35 nm. The saturation magnetization (Ms) of CoFe2O4/TiO2 nanocomposite was determined to be 29.64 emu g-1. Photocatalytic activity and cycle stability were studied by the photomineralization of formic acid under solar light irradiation.

Methylene Blue Degradation over Photocatalyst Bismuth Vanadate Powder Synthesized by the Hydrothermal Method

Bismuth vanadate powder was synthesized by the hydrothermal method with bismuth nitrate and ammonium vanadate as the starting precursors with the mole ratio of bismuth and vanadium of 1:1. The mixed solution was adjusted with ammonium hydroxide until the pH of final solution was 7 and hydrothermally treated at 100 °C for 2-6h. The phase was studied by X-ray diffraction (XRD). Monoclinic structure was obtained after hydrothermal treated at 100 °C for 6h without calcination step. The morphology was investigated by scanning electron microscopy (SEM). The particle was needle-like in shape and highly agglomerate. The degradation of methylene blue over photocatalyst bismuth vanadate powder was examined by ultraviolet spectroscopy (UV). Bismuth vanadate powder synthesized by the hydrothermal method at 100 °C for 6h showed the highest photocatalytic activity.

Characterization of bismuth vanadate (BiVO4) nanoparticle prepared by solvothermal method

ABSTRACT Bismuth vanadate (BiVO4) nanoparticle was prepared by solvothermal method. The starting precursors were used as bismuth nitrate pentahydrate (Bi(NO3)3•5H2O), ammonium metavanadate (NH4VO3) and absolute ethanol (C2H5OH). Solution I: Bi(NO3)3•5H2O was dissolved in 2.0 M nitric acid (HNO3) and absolute ethanol (C2H5OH). Solution II: NH4VO3 was dissolved in 2.0 M ammonium hydroxide (NH4OH) and absolute ethanol (C2H5OH). The mixed solutions were stirred for 5 min and left into Teflon-lined stainless steel autoclave treatment at 200°C for 3 and 5 h. The yellow final solution was filtered and dried at 100°C for 24 h. All BiVO4 nanoparticle samples were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDXS) and Fourier transform infrared spectrometer (FTIR).

Microwave-assisted Synthesis Bismuth Vanadate (BiVO4) Powder

Bismuth vanadate (BiVO4) powder was synthesized by the microwave method. Bismuth nitrate pentahydrate (Bi(NO3)3.5H2O) and ammonium vanadate (NH4VO3) were used as the starting precursors with the mole ratio of 1:1. The mixed solution was stirred and adjusted the pH of solution to 7 with ammonium hydroxide (NH4OH). The yellow final solution was treated in the microwave with an irradiation power at 600, 700 and 800 Watt for 2, 4 and 6 min, respectively. The phase of BiVO4 powder was identified by X–ray diffraction (XRD). The morphology and chemical composition of BiVO4 powder were investigated by scanning electron microscopy (SEM) and energy dispersive X–ray spectroscopy (EDXS), respectively. The surface area of BiVO4 powder was determined by Brunauer–Emmett–Teller analysis (BET).

The Photocatalytic Degradation of Phenol and Chlorophenol onto Bismuth Vanadate Powder Prepared by the Solvothermal Method

Bismuth vanadate (BiVO4) powder was prepared by the solvothermal method. Bismuth nitrate and ammonium vanadate were used as the starting precursors with mole ratio of 1:1. The mixed solution was heated in the solvothermal vessel at 100°C for 2–6 h. The phase of BiVO4 powder was characterized by X–ray diffractometer (XRD). The morphology and chemical composition of BiVO4 powder were investigated by scanning electron microscope (SEM) and energy dispersive X–ray spectroscope (EDXS). The surface area of BiVO4 powder was determined by Brunauer, Emmett and Teller analyzer (BET). The photocatalytic degradation of phenol and chlorophenol onto BiVO4 powder was studied and determined by gas chromatograph (GC).