<i>Tagetes erecta</i> synthesized bimetallic Ag–Au nanoparticles and their potential application in electrochemical detection and estimation of ampicillin in raw milk

This study focuses on the green synthesis of Ag-Au nanoparticles using <i>Tagetes erecta</i> extract and their potential application in electrochemical detection and estimation of ampicillin in raw milk. The synthesised nanoparticles were characterized using both physical as well as electrochemical techniques to assess their structural, morphological and conductive properties. The Ag-Au nanoparticles were covalently bonded to the hydroxylated fluorine doped tin oxide electrode surface through silane chemistry enabling the effective interaction of the 5' thiolated-aptamer with the nanoparticle-modified surface for aptasensor development. The proposed aptasensor displayed a highly sensitive and selective electrochemical response towards ampicillin within a range of 0.1 ng mL^-1 to 1000 ng mL^-1 with a limit of detection of 0.40 ng mL^-1 and a shelf-life of 30 days. Moreover, the aptasensor demonstrated reliable performance with both spiked milk samples and real milk samples, detecting a concentration of 194 ng mL^-1 in raw milk with results closely matching with those obtained by LC-MS. Therefore, this study highlights the feasibility of plant-based nanoparticle synthesis for developing cost-effective and efficient electrochemical sensors in food safety monitoring.