Nanobioengineered Al₂O₃ Core–Shell Nanoparticle Preparation Using <i>Bauhinia Variegate</i> Plant Extract for Efficient Photocatalysis and Electrochemical Sensing

Core-shell-based nanomaterials have garnered considerable attention in the recent past not only in catalytic applications but also in their potentiality in selective and efficient sensing. Present research reports the first and successful biosynthesis of the core (c-Al₂O₃)-shell nanoparticles (NPs) using <i>Bauhinia variegate</i> blossom extract as reducing and capping agents. The synthesized c-Al₂O₃ NPs were characterized and utilized to fabricate nanobioengineered electrodes on indium tin oxide (ITO) substrates via electrophoretic deposition. Electrochemical analysis, including cyclic voltammetry and differential pulse voltammetry, revealed quasi-reversible processes with high electron-transfer rates (<i>K</i>_s = 0.66 s^-1) and a diffusion coefficient (<i>D</i> = 5.84 × 10^-2 cm² s^-1). The electrode exhibited a very high sensitivity (23.44 μA μM^-1 cm^-2) and a low detection limit (0.463 μM) for sodium azide (NaN₃) over two linear ranges of 1-6 and 8-20 μM. Additionally, c-Al₂O₃ NPs demonstrated the effective photocatalytic degradation of crystal violet dye under visible light, following pseudo-first-order kinetics. The fabricated electrode showed excellent selectivity, stability, and reproducibility, highlighting its potential for environmental monitoring and clinical diagnostics.