Photophysical Interactions of CuO Nanoparticles With Nile Blue Dye: A Comprehensive Study

In this study, CuO nanoparticles (NPs) were synthesized via a simple precipitation method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The CuO NPs exhibited high crystallinity with a monoclinic phase and an average crystalline size of 22 nm. UV-visible spectroscopy revealed an excitonic absorption peak at 251 nm and a bandgap of 3.78 eV, while photoluminescence (PL) studies showed a distinct emission peak at 379 nm, attributed to radiative recombination and defects in the NPs structure. The interaction between CuO NPs and NB-690 dye was explored through UV-visible and fluorescence spectroscopy, showing enhanced absorption and fluorescence quenching upon complex formation. The apparent association constant (K_app) was determined to be 1 × 10⁶ M^-1, with a low limit of detection (12 nM). Stern-Volmer analysis revealed a binding constant of 6.21 × 10⁵ M^-1 and a binding site value of 1.7 in the excited state. These results highlight the potential of CuO NPs for applications in environmental monitoring, biomedical imaging, and drug delivery, demonstrating their ability to modulate light absorption and fluorescence in complex biological and chemical systems.