Ag-doped CuO nanoparticles (Ag@CuO NPs) were synthesized via hydrothermal method and exposed to 50 kGy gamma irradiation. XRD analysis showed a crystallite size reduction from 25.50 nm to 17.98 nm and a decrease in crystallinity from 62.8% to 53.2%. UV–Visible spectra exhibited a red shift in the peak from 371 to 382 nm) and a bandgap reduction from 2. 41 eV to 2.28 eV, attributed to radiation-induced defects. FTIR spectra indicated bond modifications, while Kramers–Kronig (KK) analysis revealed a red shift in optical phonon modes due to lattice distortions. Z-scan measurements showed enhanced nonlinear optical (NLO) properties, with the third-order susceptibility, \({\chi }^{(3)}\) increasing from \(4.963\times {10}^{-4} esu\) to \(7.681\times {10}^{-4} esu\) post-irradiation. These results confirm the impact of gamma irradiation in tuning the structural and optical properties of Ag@CuO NPs. To support the experimental findings, Monte-Carlo simulations were conducted to model defect generation and structural changes in Ag@CuO NPs due to gamma irradiation. The results showed an energy deposition of \(3.10\times {10}^{23} eV/{cm}^{3}\) , leading to a defect density of \(\sim 4.2\times {10}^{18} {cm}^{-3}\) , which disrupted the crystalline order. This correlated well with the XRD peak broadening and crystallinity reduction. The simulations also confirmed the formation of mid-gap states, explaining the bandgap narrowing observed experimentally. These findings highlight the significant role of gamma irradiation in tailoring the optical and electronic properties of Ag@CuO NPs for applications in optical limiting, photonic switching, and radiation shielding.
