Fabrication of CS-TiO₂-Ag Nanocomposites by Laser Ablation for Antimicrobial Applications and Water Purification

In this study, we fabricated a series of nanocomposites using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser that was operated with specific parameters, as follows: wavelength, 1064 nm; energy output, 500 mJ; pulse number, 500; and frequency, 1 Hz. Four distinct types of nanocomposites were produced: chitosan (CS); chitosan-titanium oxide (CS-TiO₂); chitosan-silver (CS-Ag); and a composite of chitosan, titanium oxide, and silver (CS-TiO₂-Ag). A transmission electron microscopy (TEM) analysis was employed to characterize these nanocomposites, revealing particle sizes of 13, 15, 34, and 32 nm for CS, CS-TiO₂, CS-Ag, and CS-TiO₂-Ag, respectively. We further evaluated the antimicrobial efficacy of these nanocomposites against two prevalent bacterial strains, i.e., Escherichia coli and Klebsiella. Our observations indicated varying degrees of bactericidal effectiveness, as represented by the diameters of the killing zones. More specifically, for E. coli, the inhibition diameters were 20 mm (CS), 36 mm (CS-Ag), 38 mm (CS-TiO₂), and 40 mm (CS-TiO₂-Ag). Similar results were observed for Klebsiella, with inhibition diameters of 28 mm (CS), 35 mm (CS-Ag), 38 mm (CS-TiO₂), and 43 mm (CS-TiO₂-Ag). Moreover, the CS-TiO₂-Ag nanocomposite was further studied regarding its potential for use in environmental applications, especially water purification. An experiment combining 30 mL of the CS-TiO₂-Ag nanocomposite with 30 mL of contaminated water resulted in successful purification, as corroborated by a subsequent analysis. In conclusion, this study offered important insights into the fabrication of chitosan-based nanocomposites and their respective antimicrobial performances against E. coli and Klebsiella. Furthermore, it illustrated the promising potential of the CS-TiO₂-Ag nanocomposite for use in water purification applications, thus demonstrating its potential for broader environmental utility.