: In this study, graphene oxide nanoclusters with a cysteine-capping agent, having a particle size of approximately 1 nm, were synthesized and analyzed. Gamma-ray spectroscopy revealed that these nanoclusters exhibit high mass attenuation coefficients across different gamma-ray energy ranges, indicating their potential for shielding applications against high-energy radiation. Fourier Transform Infrared (FTIR) spectroscopy confirmed that the presence of cysteine modifies the chemical properties of the nanoclusters, including alterations in existing bonds and an increased incorporation of nitrogen and sulfur within the graphene structure. These modifications can significantly influence the electronic and optical properties of the material. Furthermore, using the Kramers-Kronig method, the optical parameters, including refractive index, extinction coefficient, and dielectric function of these nanoclusters, were determined. A detailed analysis of these coefficients enabled the extraction of transverse optical (TO) and longitudinal optical (LO) phonon modes, which were found at 1670 cm⁻¹ and 1730 cm⁻¹, respectively. These findings confirm the influence of the cysteine ligand on the electronic and optical structure of graphene oxide nanoclusters.