“Rapid visual screening” and precise quantification: A colorimetric-ratiometric fluorescent dual-mode sensing platform based on DT-Cu nanozymes for rapid detection of kasugamycin

A Cu–N-centered DT–Cu nanozyme enables dual-channel KSM readout. • Chromatography-free sensing enables on-site screening and FL confirmation. • For the first time, B-CDs-referenced readouts cross-validate KSM in food matrices. • The rapid method achieves a low LOD and 90.0–103.6% recoveries in food samples. Rapid screening and quantitative confirmation of kasugamycin (KSM) residues in foods remain challenging without chromatographic instruments. Herein, a low-cost colorimetric/dual-excitation ratiometric fluorescent platform was developed using 3,5-diamino-1,2,4-triazole-coordinated copper nanozymes (DT–Cu). Characterization verified Cu–N-associated active sites and homogeneous elemental distribution. DT–Cu catalyzed H 2 O 2 -mediated oxidation of Ampliflu Red to resorufin, whereas KSM inhibited its peroxidase-like activity through coordination/hydrogen-bonding-associated interactions, causing color fading and red fluorescence attenuation. Blue carbon dots were introduced as an internal reference to construct an I 435 /I 584 readout, improving resistance to matrix and instrumental fluctuations. Under optimized conditions, KSM was detected over 0.001–50 μg mL −1 with a detection limit of 2.31 pg mL −1 within 40 min. The probe showed good 7-day storage stability. Recoveries of 90.0%–103.6% with RSDs of 0.11%–5.89% were obtained in real samples, demonstrating its potential for rapid on-site screening. Download: Download high-res image (188KB) Download: Download full-size image