Facile Synthesis of Carbon Dot Deposited gamma-FeOOH Nanosheet/ Polypyrrole Composite: A Robust Photocatalyst for Degradation of Antibiotics under Sunlight Irradiation with Enhanced Antibacterial Activity

This work reports the fabrication of a nanocomposite using carbon dot-deposited gamma-FeOOH/polypyrrole composite through a facile in situ growth of gamma-FeOOH, polymerization of pyrrole, and deposition of carbon dots (CDs) in a single pot along with its application as a photocatalyst toward degradation of antibiotics under sunlight irradiation. Here, the expired pharmaceutical drugs (waste) were used as a source of the synthesis of CDs to realize a "waste-to-wealth" approach. A series of nanocomposites (PFL/CDs-x; x = 1, 2, 3, and 4) with different gamma-FeOOH content have been synthesized, and their photocatalytic activity was studied. Among all composites, PFL/CDs-2 exhibited the highest degradation efficiency of 97% within 90 min. The optimized gamma-FeOOH and CD content in PFL/CDs-2 enhanced light trapping, charge separation, surface area, and formation of distinct heterojunction, indicating it as a promising candidate in photocatalysis. The excellent photocatalytic activity of PFL/CDs-2 can be attributed to synergistic enhancement of the light harvesting due to slow photon effect of the gamma-FeOOH nanosheet and the inhibited recombination rate of photoexcited charge carriers based on a Z-scheme photocatalytic mechanism. In addition, the antibacterial potential of the synthesized nanocomposite was studied against Bacillus pumilus (Gram -positive) and Escherichia coli (Gram-negative) bacteria. Moreover, the PFL/CDs-2 composite was found to be magnetically separable and recycled without a significant loss of photocatalytic efficiency after four cycles, indicating the high reusability and stability of the photocatalyst.