A ratiometric fluorescent probe for the detection of fluoroquinolones and tetracyclines

Antibiotics are widely used globally, leading to significant environmental issues and food contamination. This has sparked interest in developing methods to detect various antibiotics. In this study, we synthesized blue fluorescent carbon dots (g-CDs) using a microwave heating technique. The produced g-CDs were combined with red fluorescent iron nanoclusters (Fe NCs) and Zn²⁺ ions, forming a g-CDs-Fe NCs-Zn²⁺ system that exhibited two distinct fluorescence emission peaks at 460 nm and 580 nm when excited at 400 nm. Upon the addition of ciprofloxacin (CIP) or enrofloxacin (ENR), the fluorescence intensity at 460 nm showed minimal change, while the fluorescence intensity at 580 nm significantly decreased. In contrast, the addition of gatifloxacin (GAT) caused the fluorescence peak at 460 nm to enhance and shift to 480 nm. When tetracycline (TC) or oxytetracycline (OC) were introduced, the fluorescence intensity at 460 nm remained stable, but a new fluorescence peak at 525 nm gradually appeared. Additionally, the addition of aureomycin (AC) caused the fluorescence peak at 460 nm to weaken and shift to 525 nm. Thus, this study presents a novel g-CDs-Fe NCs-Zn²⁺ system for detecting various antibiotics, including CIP, ENR, GAT, TC, OC, and AC, utilizing different fluorescent detection modes.