Cu-doped ZnS nanoparticle-PMMA thin films with enhanced nonlinear optical response for photonics applications

Cu-doped ZnS nanoparticles (NPs) (1–3 wt%) surface-modified with l -alanine were synthesized by a simple co-precipitation method and embedded in a polymethyl methacrylate (PMMA) host matrix as thin films via spin coating. X-ray diffraction confirmed the cubic zinc blende phase, while energy-dispersive X-ray spectroscopy verified the presence of only the desired elements. High-resolution transmission electron microscopy revealed uniform NPs of 2–5 nm in size. Optical absorption spectra exhibited peaks at 290–320 nm, and Tauc’s plot analysis indicated band gap enhancement at the nanoscale. Nonlinear optical characterization using the Z-scan technique showed negative nonlinear refraction and reverse saturable absorption, attributed to thermal, surface state, and dielectric effects. These findings demonstrate the strong potential of Cu-doped ZnS-PMMA thin films for photonics applications. • L -alanine capped Cu-doped ZnS nanoparticles embedded in PMMA films. • Phase-pure cubic zinc blende structure with 2–5 nm uniform particles. • Cu successfully incorporated without secondary phase formation. • Band gap modulation and UV-Vis excitonic absorption observed. • Strong third-order nonlinear optical response demonstrated via Z-scan.