Synthesis of ZnO/SnO₂/CQDs Nanocomposites and its Application in Uric Acid Detection by Photoluminescence Method

In this study, a Zinc oxide/Tin dioxide/Carbon quantum dots nanocomposite (ZnO/SnO₂/CQDs NCPs) was successfully synthesized and comprehensively characterized, and its application as a photoluminescence-based sensor for highly sensitive uric acid detection was explored. Individual nanoparticles of CQDs, ZnO, and SnO₂ were synthesized via a hydrothermal method, while the final composite was fabricated through a straightforward physical mixing approach. Characterization results obtained from UV-vis spectroscopy, XRD, TEM, and EDX analyses confirmed the structural integrity, morphology, and improved surface properties of the as-prepared nanocomposite. TEM images revealed that SnO₂ nanoparticles possessed an average diameter of ≈ 3 nm, ZnO nanoparticles ≈ 50 nm, and CQDs ≈ 22 nm, with ZnO, SnO₂, and CQDs randomly interconnected within the ZnO/SnO₂/CQDs nanocomposites (ZnO/SnO₂/CQDs NCPs). The sensing mechanism was governed by the "turn-on" photoluminescence phenomenon, arising from electron transfer between the excited nanocomposite and uric acid molecules. The fabricated sensor exhibited outstanding analytical performance, including an ultra-low limit of detection (LOD) of 0.085 nM, an exceptionally wide linear detection range spanning from 10^-13 M to 0.1 M, and a strong linear correlation coefficient (R² = 0.992) at the excitation wavelength of 420 nm, attributed to the synergistic interactions among the components. These findings underscore the composite's potential as a highly sensitive and reliable platform for uric acid detection. This work thus provides a simple, cost-effective, and promising strategy for clinical diagnostics and broader biomedical applications.