Hydrogen-bond induced enhanced emission ratiometric fluorescent handy needle for visualization assay of amoxicillin by smartphone sensing platform

Amoxicillin (AMO) is one of the most commonly used antibiotics, and its abuse in animal husbandry or clinical therapy can pose unpredictable hazards to humans. Therefore, it is crucial to develop a real-time and rapid method to accurately determine AMO content. Here, we designed a fluorescent nanoprobe for qualitative and quantitative AMO determination by using as-synthesized green safe materials of nontoxic red carbon dots (RCDs) and blue carbon dots (BCDs). In the presence of AMO, a reaction promoting hydrogen bonding occurred immediately, resulting in an instant increase in the intensity of the blue fluorescence of BCDs, accompanied by a marked color change from red to blue. For practical application, we designed a nontoxic sensing fluorescent handy needle to directly and quantitatively detect AMO in real samples. This portable and easy-to-use device was demonstrated on a smartphone platform based on 3D printing technology, which offers the advantages of simple production, excellent visualization, fast response, and instant quantitative detection. The device requires an extremely short detection time and has a sensitive detection limit of 2.39 nM. The method presented here enables real-time assessment for food safety, as well as on-site detection under field conditions to track various trace substances for timely health checks.