Quantum-sized Ag nanoparticle conjugates on biofunctionalized La2O3–rGO ternary nanocomposite-based platform for the electrocatalytic determination of dopamine

Abstract

In order to synthesize distinctive ternary nanocomposites, this study combines nanostructured lanthanum oxide (La₂O₃), reduced graphene oxide (rGO), and quantum size (5–6 nm) silver nanoparticles (AgNPs). La₂O₃ does not aggregate when AgNPs are introduced with rGO, which also increases bioactivity for the immobilization of biomolecules. Further, effective surface contacts are made possible by the functional groups of rGO and hexagonal La₂O₃ nanoparticles and the large surface area of rGO increases the electrical conductivity of its electron clouds. The rGO and La₂O₃ (L) are conjugated with AgNPs using an ex situ hydrothermal technique to create L-rGO/Ag nanocomposites. Prepared ternary L-rGO/Ag nanocomposites have been confirmed using various characterization methods, such as XRD, FT-IR, UV-visible, PL, Raman, SEM, TEM, and EDAX. Further, the tyrosinase enzyme has been immobilized onto the L-rGO/Ag/ITO electrode for electrochemical dopamine biosensing via DPV analysis. Standard dopamine samples were investigated in the range of 1 to 95 μM and the bioelectrode displayed outstanding sensitivity of 24.32 × 10⁻⁴ mA μM⁻¹ cm⁻² for lower concentrations (1–35 μM) and 20.88 × 10⁻⁴ mA μM⁻¹ cm⁻² for higher concentrations (40–95 μM), and limit of detection (LOD) of 0.34 μM. In addition to this, the bioelectrode exhibits 40 days of stability, minimal interference, and 8 cycles of reusability without significant deterioration. Its low Michaelis–Menten constant (K_m) value of 3.70 μM emphasizes its great dopamine sensitivity and affinity. Hence, the use of this bioelectrode in real sample analysis is motivated by the encouraging results in standard sample analysis of dopamine, opening possibilities for a variety of useful practical applications for timely monitoring and managing neurodegenerative disordered.