Zirconium hydroxide particles are reactive and photoluminescent, emitting blue light under ultraviolet (UV) irradiation. Adsorption-induced changes in the photoluminescence (PL) offer opportunities for gas sensor/filtration applications. The PL of Zr(OH)(4) is quenched in the presence of molecular oxygen, likely through trapping of surface electrons via the formation of O-2(-). Heating the powder high enough to desorb hydroxyl groups broadens the PL spectrum toward longer wavelengths. This 'red-stretch' also occurs upon reaction with sulfur dioxide, which replaces terminal hydroxyl groups with sulfite ones. Excessive UV irradiation correspondingly induces this effect. A mechanism is proposed to account for the red-stretch. (C) 2013 Elsevier B.V. All rights reserved.