Laser fluence dependent antibacterial activity of cadmium sulfide quantum dots prepared by one step laser ablation in liquid

Cadmium sulfide (CdS) quantum dots (QDs) were synthesized using pulsed laser ablation in liquid (PLAL) at different laser fluences. The effect of laser fluence on the optical, structural, morphological, and electrical properties of CdS QDs was investigated by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), zeta potential, photoluminescence (PL), transmission electron microscopy (TEM), UV–Visible absorption spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). XRD analysis show that the synthesized CdS QDs have a hexagonal wurzite structure and the crystallite size was in the range of 6–11 nm. They also exhibit negative surface charge about − 2.7, − 18.2, and − 19.0 mV, all that for CdS QDs, which were prepared at 1.27, 3.82, and 7.64 J/cm², laser fluences, respectively. The antibacterial activity of the CdS QDs was evaluated against both Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus, Streptococcus agalactiae). The results showed varying inhibition zones depending on the concentration, surface deformation, and particle size of the CdS QDs, in which the smallest size QDs, which were prepared by using 7.64 J/cm² laser fluence, show higher inhibition zones than other particles. In addition, the minimum inhibitory concentration (MIC) was determined for each bacterial strain.