Superhydrophobic and photocatalytic self-cleaning cotton fabric using flower-like N-doped TiO2/PDMS coating

Self-cleaning fabrics can be developed based on introducing two mechanisms of superhydrophobicity and photocatalytic activity to conventional fabrics. However, there are some downsides such as inefficiency of superhydrophobic coatings against oily contaminants and low effectiveness of photocatalytic surface treatments under visible light which have restricted the widespread applications of these functional products. This research presents the development of self-cleaning cotton fabric with dual functionalities of superhydrophobicity and photocatalytic activity using microhierarchial TiO2-based particles. It is aimed to fabricate fluorine-free durable superhydrophobic coatings with simultaneous photocatalytic self-cleaning under simulated sunlight. Fluorine-free coating formulations composed of flower-like particles, either TiO2 or nitrogen-doped TiO2, and polydimethyl siloxane (PDMS) polymer were applied to cotton fabrics using a facile dip-coating method. The self-cleaning performance of fabrics was assessed based on their superhydrophobicity and effective removal of oil-based stains under simulated sunlight. Additionally, the impact of nitrogen doping on enhancing the photocatalytic activity of flower-like TiO2 particles was investigated. The obtained results demonstrated that the presence of both PDMS and hierarchical particles generated excellent superhydrophobicity on the cotton fabric with a water contact angle of 156.7° ± 1.9°. In addition, the coated fabric exhibited highly efficient photocatalytic activity, decomposing absorbed stains after 30  min of irradiation. Nitrogen doping process significantly boosted the photocatalytic activity of TiO2 particles in degrading food stains and Rhodamine B dye solution. The developed fabrics showed high robustness against chemical and physical durability tests.