[Enhanced visible-light absorbance of nanosized AgI/TiO2 by using calcination combined with light irradiation]

With the aim to enhance visible-light absorbance, calcination combined with light irradiation was used to modify nanosized AgI/TiO2. UV-Vis spectrum curves indicated that the modified sample exhibited an intense absorption in the whole visible light range and a spectrum shifted from 465 nm to 800 nm, and that absorbance at 500 nm was improved three times as much as that of the reported pertinent material. XRD analytic results demonstrated that calcined AgI/TiO2 possessed more rutile phase with reduced band gap from 2.89 eV to 2.81 eV, and that the following xenon-light irradiation further enhanced the relative contents of anatase TiO2, rutile TiO2 and AgI accompanied with produced AgCl phase, leading to the decrease in band gap to 1.55 eV. Formation of AgCl and increases in the relative contents of rutile TiO2 and AgI should take the main responsibilities for the decrease in the band gap and enlargement of visible-light absorbance. Additionally, it was confirmed that only the spectrum absorption of the calcined AgI/TiO2 could be improved by light irradiation, and that ultraviolet light played more role than visible part during the light irradiation. Moreover, it was proposed here that two or more silver halides supported on TiO2 could show more capabilities to stimulate visible-light activation of TiO2.