Kompetenzzentrum für Mikro- und Nanotechnologien

Fast fashion and expansion into new markets, mainly in Asia, have drastically increased the demand for dyes. A significant proportion of toxic dyes enter the environment unfiltered, causing severe damage, such as disrupting photosynthesis and respiration in aquatic organisms even at low concentrations of 1 mg/L. Reducing the concentration or entirely removing those dyes is therefore essential to protect aquatic life and ensure clean drinking water. Here, we present a novel approach for fabricating photocatalytic ZnO and TiO2 nanostructures with high photocatalytic activity on a large scale using metastable atomic layer deposition (MS-ALD). Dose times and number of cycles were optimized to achieve structures with superior optical performance. Mean absorption rates of 79 % and 68 % were achieved over a broad spectral range (200 nm–2500 nm) for TiO2 and ZnO nano-structures, respectively. Optimized structures were used to test the degradation of the model analyte Acid Orange 7 (AO7) under UV light. ZnO structures demonstrated high activity, significantly reducing AO7 concentration, whereas TiO2 structures showed no photocatalytic activity. The inactivity of TiO2 could be attribute to numerous effects such as the absence of a crystalline phase or fast charge recombination.