Silica nanoparticles assisted photodegradation of acridine orange in aqueous suspensions

tSilica nanostructured materials are often used as catalyst support but their catalytic role has not beendeeply investigated yet. In the present study, the photocatalytic degradation of acridine orange zincchloride double salt (AO) has been studied using silica nanoparticles (NPs) as catalysts. NPs of differentsize (55 and 146 nm) were prepared by a sol–gel procedure and their surface was modified with aminogroups to investigate the role of the chemical groups linked to the silica surface on the dye degradation.The silica nanomaterials were fully characterized by use of transmission electron microscopy (TEM), zetapotential measurements and UV–vis spectrophotometric methods.The photodegradation experiments were carried out irradiating at 313 or 490 nm for 50 min the aque-ous samples containing the dye and the silica NPs of 55 or 146 nm in diameter. The photocatalyticdegradation of the dye was determined from the decrease of its fluorescence intensity. AO fluorescenceintensity did not change when bare SiO2beads were used as catalysts, whereas an efficient decoloration(up to 58%) was achieved with amino functionalized NPs, with a photodegradation rate constant valueof 0.136 m−1. The data collected from the degradation experiments demonstrated that the functionalgroups on the silica surface have a fundamental role in the efficiency of the degradation processes