Thermal decomposition synthesis of Zn-HAP (extracted from fish scale) nanopowder and its photocatalytic and antibacterial activities under visible light

Abstract

The present study, for the first time, reports synthesizes Zn-Hydroxyapatite (Zn-HAP) nanopowder through a novel thermal decomposition method. Zn-HAP was characterized using FE-SEM, EDX, XRD, BET, DRS, PL, and FT-IR spectroscopy techniques. FT-IR spectroscopy confirmed that the main characteristic peaks of HAP are preserved in Zn-HAP with little variations in peak positions. The XRD pattern also confirmed the intensity of peaks of Zn-HAP is slightly lowered due to zinc substitution, while the diffraction peak positions are not shifted. DRS data showed two band gaps energies of 2.9 eV and 3.5 eV. PL emission spectra represented that doping of Zn2+ ions into the crystal structure of HAP facilitates the separation of charge carriers, therefore suppress electron-hole recombination. It is also found that Zn-HAP can be used for adsorption and photocatalytic degradation of naphthalene under visible light (R% = 68.5%). The results of EIS and photocurrent generation measurements demonstrated that the Zn-HAP has faster transfer of the photogenerated electron–holes pairs and higher separation efficiency comparing with pure HAP. The antibacterial activity was examined on gram-positive (Streptococcus aureus and Bacillus subtilis) and gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia). The results show that HAP nanopowder does not exhibit antibacterial activity at the concentrations studied, while Zn-HAP displays antibacterial properties for both gram-positive and gram-negative bacteria. Moreover, inactivation of E. coli by various scavengers suggested that OH.,O2−. and hole are the major species involved in bacterial disinfection. Overall, the results revealed that prepared Zn-HAP is a good and inexpensive nanomaterial to remove bacteria and organic dyes from drinking water resources.