Structure-property correlation of scheelite SrAO4 (A = Mo and W) for electrochemical detection of quercetin: Experimental and DFT insights into the oxidation mechanism.

Quercetin (QCT), a widely distributed bioactive flavonoid, requires sensitive and selective monitoring in complex aqueous and food matrices. Current work reports a systematic structure-property investigation of scheelite-type strontium-based binary oxides (SrAO4, A = Mo, W) as electrocatalytic modifiers for high-performance electrochemical detection of QCT. SrMoO4 and SrWO4 nanomaterials were synthesized via a facile hydrothermal route and comprehensively characterized to establish correlations between their crystal structure, morphology, and charge-transfer behavior. Electrochemical studies reveal that SrMoO4 exhibits markedly enhanced interfacial electron transport, reduced charge-transfer resistance, and a higher electrochemically active surface area, resulting in superior sensing performance. The SrMoO4/SPCE delivers a wide linear detection range (0.1-1100 μM) with LOD of 2 nM. Excellent selectivity, antifouling behavior, and operational stability enable the accurate quantification of QCT in green tea and river water samples with high recovery. Additionally, DFT calculations elucidate the oxidation mechanism of QCT during the electrochemical process.