Insights into the generation of reactive oxygen species (ROS) over polythiophene/ZnIn₂S₄ based on different modification processing

The performance of a polythiophene-modified ZnIn₂S₄ hybrid photocatalyst was associated with the processing methods. We reported the influence of different modification methods (blending versus surface polymerization) on photogenerated reactive oxygen species (ROS) and photocatalytic degradation of tetracycline. The photocatalytic degradation of tetracycline was enhanced with polythiophene modification either by blending or by surface chemical polymerization, and 51% or 54% NPOC (non-purgeable organic carbon) removal was achieved, respectively, in comparison with 36% for ZnIn₂S₄. Nanosized particles in the range of 10-20 nm were observed in pure ZnIn₂S₄ and the blended sample (PTh-ZIS) via an ethanol-thermal method, resulting in a high surface area of 188 m² g^-1 and 209 m² g^-1, respectively. The optical property of ZnIn₂S₄ still dominated the blended samples so that superoxide radical (O₂^-) was generated from ZnIn₂S₄ through electron transfer. For surface polymerization samples, transmission electron microscopy (TEM) clearly showed that ZnIn₂S₄ particles were covered by a thin polythiophene film, which can act as a photosensitizer promoting the generation of singlet oxygen (¹O₂) through energy transfer. Overall, our work revealed important processing guidelines together with ROS detection for the conductive polymer-modified photocatalyst.