Simultaneous photocatalytic degradation and SERS detection of tetracycline with self-sustainable and recyclable ternary PI/TiO2/Ag flexible microfibers

Facile and efficient photocatalysts using sunlight, as well as fast and sensitive surface-enhanced Raman spectroscopy (SERS) substrates, are urgently needed for practical degradation of tetracycline (TC). To meet these requirements, a new paradigm for PI/TiO₂/Ag organic‒inorganic ternary flexible microfibers based on semiconducting titanium dioxide (TiO₂), the noble metal silver (Ag) and the conjugated polymer polyimide (PI) was developed by engineering a simple method. Under sunlight, the photocatalytic characteristics of the PI/TiO₂/Ag flexible microfibers containing varying amounts of Ag quantum dots (QDs) were evaluated with photocatalytic degradation of TC in aqueous solution. The results demonstrated that the amount of Ag affected the photocatalytic activity. Among the tested samples, PI/TiO₂/Ag-0.07 (93.1%) exhibited a higher photocatalytic degradation rate than PI/TiO₂ (25.7%), PI/TiO₂/Ag-0.05 (77.7%), and PI/TiO₂/Ag-0.09 (63.3%). This observation and evaluation conducted in the present work strongly indicated a charge transfer mechanism. Moreover, the PI/TiO₂/Ag-0.07 flexible microfibers exhibited highly sensitive SERS detection, as demonstrated by the observation of the Raman peaks for TC even at an extremely low concentration of 10^-10 moles per liter. The excellent photocatalytic performance and SERS detection capability of the PI/TiO₂/Ag flexible microfibers arose from the Schottky barrier formed between Ag and TiO₂ and also from the outstanding plasmonic resonance and visible light absorptivity of Ag, along with immobilization by the PI. The successful synthesis of PI/TiO₂/Ag flexible microfibers holds significant promise for sensitive detection and efficient photocatalytic degradation of antibiotics.