Ratiometric fluorescence determination of chlortetracycline based on the aggregation of copper nanoclusters triggered by aluminum ion

Abstract

The aggregation-induced emission (AIE) characteristic of copper nanoclusters (CuNC) was for the first time used to construct a ratiometric fluorescence probe (CuNC-Al 3+ ) for detection of chlortetracycline (CTC). Aluminum ion (Al 3+ ) can aggregate free CuNC and make it emit a bright and stable red fluorescence. A slight excess of Al 3+ in CuNC-Al 3+ solution can form a CTC-Al 3+ complex to limit the conformational rotation of CTC molecule and enhance CTC fluorescence. So, the red fluorescence of CuNC-Al 3+ probe and the enhanced CTC fluorescence are used as a reference signal and a response signal to detect CTC, respectively. The method developed shows a good linear relationship between the CTC concentration and the fluorescence intensity ratio (I 495 /I 575 ) in the range 0.1-3.0 µM, and the detection limit is 25.3 nM (S/N = 3). In addition, the fluorescent color of CuNC-Al 3+ probe changes from red to yellow-green as the concentration of CTC increases. Based on this observation, a fluorescent test paper has also been fabricated.

Portable Smartphone Platform Based on Aggregation-Induced Enhanced Emission Carbon Dots for Ratiometric Quantitative Sensing of Fluoride Ions

“…The XPS-deconvoluted spectrum of Al 2p showed that its characteristic peaks at 72.65 and 73.47 eV are attributed to the Al–O bond (Figure D), which was consistent with the fact that AA-CDs were rich in active functional groups such as hydroxyl groups in Figure C, indicating that OH – /COO – in AA-CDs interacted with Al 3+ to induce cross-linking and aggregation of AA-CDs. Based on the above findings, we inferred that Al 3+ formed Al–O bonds after combining with AA-CDs, which limited the vibration and rotation of active functional groups in AA-CDs, and the formation of aggregated states also reduced the interaction between AA-CDs and solvents, thereby reducing the probability of nonradiative transitions, resulting in enhanced fluorescence and lifetime of AA-CDs, and this phenomenon was attributed to Al 3+ -induced fluorescence AIE enhancement properties. ,− Furthermore, the fluorescence intensity of AA-CDs was positively correlated with the concentration of Al 3+ (Figure E), and the change trend of the fluorescence intensity and the B/R ratio was nearly identical, demonstrating that the B/R ratio can replace fluorescence as a signal reading method for quantitative detection (Figure F). However, the variation range of a single fluorescence color is narrow and the poor visual resolution hinders its practical application.…”