Author(s) :

Woosung Choi, Wang Kai Y.

Volume/Issue :

Abstract :

Sick Building Syndrome arises from volatile organic compounds (VOCs) emitted indoors by household materials. Photocatalytic oxidation with TiO2 has been studied to reduce indoor VOCs, but TiO2 mainly absorbs ultraviolet light. Indoor lighting is dominated by visible light, so the use of TiO2 indoors becomes limited. In previous studies, AgNP was added on TiO2 to push its activation range into visible light, mostly by sol-gel methods. This research examined whether simply mixing two commercial products, a colloidal silver solution and a TiO2, can produce a visible-light driven AgNP-TiO2 without chemical synthesis. The key question was whether visible-light activation through SPR sensitization requires direct Ag-O-Ti chemical bonding, or whether physical proximity between AgNP and TiO2 in the dried coating is sufficient. 1 wt% and 5 wt% AgNP-TiO2 were prepared by physical mixing and characterized by UV-Vis spectrophotometry and X-ray diffraction (XRD). SPR peak was observed at around 430 nm. XRD confirmed the anatase phase of TiO2 with rutile, and no peak shift was observed after AgNP addition. The samples were sprayed on paint-coated containers, and VOC removal was measured under UV and fluorescent lamps. VOC removal under fluorescent light followed the order of 5 wt% > 1 wt% > pure TiO2. The visible-light activity in the absence of a chemical synthesis step can be understood from the photon-based nature of the SPR effect. AgNP absorbs visible photons by plasmonic oscillation of surface electrons, and the energy is transferred to TiO2 via near-field coupling. Such a process does not require Ag-O-Ti bonding.