Investigation of Structural, Optical, Spectral and Biomedical Characteristics of ZnS Quantum Dots Using Guava Leaves Extract

Nanostructured materials with unique mechanical, optical, and electrical properties have been increasingly utilized in the fields of optoelectronics, medicine, and pharmaceuticals. This study introduces a novel green synthesis method using guava Leaves Extract to produce ZnS quantum dots (QDs) for the first time. The synthesized ZnS QDs underwent characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV–Visible spectroscopy analysis. The in vitro antibacterial activity against S. aureus (Gram-positive), E. coli, and Klebsiella pneumoniae (Gram-negative) was assessed via the paper disk agar diffusion method. Hemolysis studies were conducted to evaluate potential toxicity on red blood cells. Analysis indicated a mean crystallite size of 2.131 nm, a bandgap of 4.32 eV, and a cubic structure for the ZnS QDs. The hemolysis study showed minimal harm to red blood cells at low QD doses. The QDs exhibited the most significant inhibitory zone of 12 mm against S. aureus, while showing the least activity against Klebsiella pneumonia (10 nm) and E. coli (9 mm).