Photocatalysis on supported gold and silver nanoparticles under ultraviolet and visible light irradiation

Abstract

Studies of the optical properties and catalytic capabilities of noble metal nanoparticles (NPs), such as gold (Au) and silver (Ag), have formed the basis for the very recent fast expansion of the field of green photocatalysis: photocatalysis utilizing visible and ultraviolet light, a major part of the solar spectrum.The reason for this growth is the recognition that the localised surface plasmon resonance (LSPR) effect of Au NPs and Ag NPs can couple the light flux to the conduction electrons of metal NPs, and the excited electrons and enhanced electric fields in close proximity to the NPs can contribute to converting the solar energy to chemical energy by photon-driven photocatalytic reactions. Previously the LSPR effect of noble metal NPs was utilized almost exclusively to improve the performance of semiconductor photocatalysts (for example, TiO 2 and Ag halides), but recently, a conceptual breakthrough was made: studies on light driven reactions catalysed by NPs of Au or Ag on photocatalytically inactive supports (insulating solids with a very wide band gap) have demonstrated that these materials are a class of efficient photocatalysts working by mechanisms distinct from those of semiconducting photocatalysts. There are several reasons for the significant photocatalytic activity of Au and Ag NPs. (1) The conduction electrons of the particles gain the irradiation energy, resulting in high energy electrons at the NP surface which is desirable for activating molecules on the particles for chemical reactions. (2) In such a photocatalysis system, both light harvesting and the catalysing reaction take place on the nanoparticle, and so charge transfer Sarina SarinaSarina Sarina received her B.Sc. degree from Inner Mongolia University in 2006 and M.Sc. degree from Inner Mongolia University in 2009. She is currently a PhD student at Science and Engineering Faculty, Queensland University of Technology, under the guidance of Prof. Huai Yong Zhu. Her research interests include new visible-light photocatalysts for fine organic synthesis, such as noble metal nanoparticles (and their alloy nanoparticles) and surface complex photocatalysts working by a radical mechanism and adsorbents for removal of radioactive ions from water for safe disposal.

A review of solar and visible light active TiO2 photocatalysis for treating bacteria, cyanotoxins and contaminants of emerging concern

“…Noble metals such as Ag [74][75][76], Au [75][76][77], Pt [78] and Pd [79] and/or combinations of these metals with each other or other materials have also been studied extensively for their properties and their contribution toward visible light absorption. Ag was of particular interest due to its well-known properties of improving the photocatalytic efficiency under visible light irradiation by acting as an electron trap and delaying the recombination of the electron-hole pair through the promotion of the interfacial charge transfer.…”

Photobiological synthesis of noble metal nanoparticles using Hydrocotyle asiatica and application as catalyst for the photodegradation of cationic dyes

“…3. The dye can be degraded on the surface of AgNPs due to hot electrons present on the surface created by the intraband transition of electrons (5sp) in the AgNPs due to the LSPR [67].…”

Role of surface defects on visible light enabled plasmonic photocatalysis in Au–ZnO nanocatalysts

“…Among these, improved visible light harvesting due to the localized SPR absorption and enhanced photo-generated charge separation across the metal-semiconductor interface are primarily important for efficient visible light photocatalytic degradation of pollutants. 16,19 Recently plasmonic Au-ZnO system has been studied extensively for enhancement of solar cell efficiencies as well as in photocatalysis, for improved visible light harvesting and reduced interfacial charge recombination at the Au-ZnO interface due to the formation of the Schottky barrier at the metal-semiconductor interface. [20][21][22] However, the formation of the Schottky barrier at the Au-ZnO interface is highly dependent on defects on the semiconductor surfaces.…”