Ultrasensitive detection of amoxicillin by TiO2-g-C3N4@AuNPs impedimetric aptasensor: Fabrication, optimization, and mechanism.

The trace amount of antibiotics in water can be enriched in the human body through the food chain, leading to extremely harmful effects on people's health. Therefore, it is urgent to develop new methods to detect trace pollutants in various aquatic phase. An analytical method utilizing the synergistic effect between the sensing strategy and catalytic material with high electron transfer capacity can be used to detect trace antibiotics. In this paper, an ultrasensitive impedimetric aptasensor was fabricated by the synergy between functionalized materials (TiO2-g-C3N4) and gold nanoparticles (Au NPs). Due to the formation of the 'Au-S' bond between the thiol-aptamer and Au NPs, amoxicillin and the aptamer can be specifically recognized on the modified glassy carbon electrode (GCE), and the impedance signal increased rapidly. Meanwhile, the Box-Behnken Design (BBD) strategy was used to reduce the random error of the experiment, so that the prepared aptasensor has the highest sensitivity to the detection of amoxicillin. Under optimized conditions, the sensor successfully achieved the detection of amoxicillin in the ultra-low detection range (0.5-3 nM) and reached the ultra-low detection limit (0.2 nM). The detection strategy has good selectivity, reproducibility, and stability, and thus has good potential to detect amoxicillin in actual wastewater.