Abstract
Green synthesis of metal nanoparticles has been gaining great interest due to the increasing need for eco-friendly manufacturing and application of nanomaterials. Metal nanoparticles, especially silver nanoparticles, are widely used in water treatments and as environmental remedy. Here we present a method to synthesize silver nanoparticles at room temperature using green tea extract under visible light irradiation, along with an application for enhanced photocatalytic degradation on methylene blue (MB) dye. Ag nanoparticles were synthesized under different photoreduction times and then further characterized. The photocatalytic rate of synthesized nanoparticles was also investigated and compared with TiO2 nanowires under UV and visible light irradiations. The results showed that Ag nanoparticles can directly degrade MB dye through plasmonic excitation and electron transferring under visible light, and Ag nanoparticles can further enhance TiO2 photonic degradation by enhanced e-h separation with UV and/or a wide band light, including UV light. Ag nanoparticles under visible light photoreduction for 0.5 h presented better behavior for two kinds of plasmonic enhanced photodegradation; the average size of the nanoparticles is about 30 nm. Therefore, the green synthesized Ag nanoparticles exhibit promising prospects in chemical and biological pollutant treatment.
Highlights
Noble metal nanoparticles are being widely used in diverse areas such as microelectronics, medicine, and environment remedies due to both their unique electrical, optical and biological properties and special applications in areas such as catalysis, plasmonic devices, and biosensing [1,2]
Microbe-mediated synthesis of Ag NPs was first reported by using Pseudomonas stutzeri AG259, which was isolated from silver mines, showing the ability to produce Ag NPs [6]
The photocatalytic activity of the synthesized Ag NPs was evaluated by degradation of methylene blue (MB) under UV and visible radiation respectively. 0.02 mmol/L of MB was added to 1000 mL deionized water maintaining a concentration of 0.02 mmol/L
Summary
Noble metal nanoparticles are being widely used in diverse areas such as microelectronics, medicine, and environment remedies due to both their unique electrical, optical and biological properties and special applications in areas such as catalysis, plasmonic devices, and biosensing [1,2]. Rutile Iodine-doped TiO2 nanowires were reported to produce the highest methylene blue degradation under visible light excitation, compared to other synthesized non-metal doping nanomaterials, and the enhanced photocatalytic activity was attributed to existing oxygen vacancies, iodine multi-valences in I–O–Ti bonds, and 3d state Ti3+ sites in the TiO2 lattice [24]. By absorbing photons at the wavelength corresponding to their plasmonic absorption bands, Ag NPs generated strong LSPR; the bandgap excitation of the TiO2 particles nearby can be stimulated, increasing the photocatalytic activity due to the generation of more electron-hole pairs [30]. The effect of radiation time was evaluated to optimize the photocatalytic activity of synthesized Ag NPs. The plasmonic degradation of MB under visible light using Ag NPs was investigated and illustrated. To further confirm the plasmonic enhancement of Ag NPs under visible light, TiO2 nanowires were used to demonstrate enhanced photocatalytic activities. Teihrediergdreagdraatdioantriaotne rKatuesKingusAinggNAPgs sNaPmspslaem1–p5lesy1n–5thseysniztehdesbizye(d1)bhye(a1t)inhge;a(t2i–n5g); i(r2r–a5d)iairtrinagdifaotrin0g.5fohr, 10.h5,h1,.51hh,,21h.5. h, 2 h
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