Casein-Tb-Ti3C2 quantum dots ratiometric fluorescence probe for the detection of ciprofloxacin.

A water-stable ratiometric fluorescence probe based on casein-Tb-Ti3C2 quantum dots was developed for the highly sensitive and selective detection of ciprofloxacin. With the increase in ciprofoxacin concentration, the fluorescence intensity at 440 nm remained relatively stable, while the fluorescence emission at 543 nm exhibited progressive enhancement. This may be attributed to ciprofloxacin being able to effectively coordinate with Tb3+ ions while displacing surrounding water molecules, leading to enhanced luminescence. Thus, the I543/I440 ratio was utilized as an indicator for monitoring changes in ciprofloxacin concentration. The ratiometric fluorescence probe demonstrated excellent linearity across a concentration range 0.1-800 µM and exhibited high sensitivity, achieving a detection limit of 0.018 μM for ciprofloxacin. Furthermore, the ratiometric fluorescence probe was successfully employed for the detection of ciprofloxacin in pork, beef, fish, honey, eggs, and milk samples, achieving recoveries that ranged from 76.5 to 123%. Owing to its advantages of high sensitivity and excellent selectivity, the ratiometric fluorescence probe demonstrates significant potential for practical applications in ciprofloxacin detection.