Synthesis, characterization, and electroanalytical investigation of copper-based materials with antibacterial investigation

Abstract

Copper-amino acid-based materials have attracted significant interest because of their unique physicochemical, electrochemical, and biological properties. In this work, a copper(II)-cysteine coordination product and L-cysteine-capped copper nanoparticles (L-Cys-CuNPs) were prepared using a simple wet-chemical method. Cyclic voltammetry revealed that L-Cys-CuNPs exhibited more pronounced redox behaviour and better electron-transfer kinetics than the copper–cysteine coordination product. UV-visible spectroscopy confirmed copper-cysteine coordination and nanoparticle formation through characteristic absorption (580 nm) features. FTIR analysis showed that copper and cysteine interacted strongly via thiols (-SH) and carboxylate (COO^-) groups, thus confirming that the copper nanoparticles were effectively surface-capped with L-cysteine. X-ray Diffraction (XRD) results showed that the copper–cysteine coordination product was mostly amorphous. In contrast, the L-Cys-CuNPs showed sharp diffraction peaks at 2θ = 43.1, 50.1, and 73.8, indicating crystalline copper. Scanning electron microscopy (SEM) images showed that the copper–cysteine coordination product had an irregular shape. The L-Cys-CuNPs appeared well dispersed, nearly spherical, and showed less clumping. EDS analysis showed C, N, O, and Cu in the Cu(II)-cysteine coordination product and L-cysteine-capped copper nanoparticles. The elemental composition supports the incorporation of cysteine-associated elements with copper in the synthesized material. Antibacterial tests on selected Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) showed that L-Cys-CuNPs had stronger antibacterial activity.