A. G. Bharathi Dileepan, S. Jeyaram
Abstract The issue of industrial effluent has been a long‐standing concern for researchers, particularly regarding effective and sustainable wastewater treatment methods. Among the potential solutions, photocatalysis has emerged as a promising approach. In this study, we present the green synthesis of selenium dioxide (SeO 2 ) nanoparticles (NPs) using the methanolic extract of Shuteria involucrata , a plant that has not previously been explored for this purpose. The novelty of this work lies in both the eco‐friendly synthesis method and the dual functional evaluation of the resulting SeO 2 NPs for photocatalytic and nonlinear optical (NLO) applications. Structural and morphological analyses were conducted using XRD, HRTEM, FESEM, and EDS. BET results indicated a mesoporous structure, which is favorable for moderate adsorption. Optical characterization through UV‐DRS revealed a narrow bandgap of 1.47 eV, contributing to a photocatalytic degradation efficiency of 32.7% for Rhodamine B (RhB) under visible light in just 90 min—a notable performance for green‐synthesized SeO 2 . Furthermore, we investigated the NLO properties using the Z‐scan technique under continuous wave laser excitation at 405 nm. The results indicated self‐defocusing behavior and reverse saturable absorption (RSA) related to nonlinear coefficients. These findings suggest that green‐synthesized SeO 2 NPs not only function as effective photocatalysts but also exhibit significant nonlinear optical behavior, making them suitable for multifunctional applications in both environmental and photonic fields.