Construction of dual-channel ratio sensing platform and molecular logic gate for visual detection of oxytetracycline based on biomass carbon dots prepared from cherry tomatoes stalk

[Display omitted] •The addition of tryptophan greatly improves the fluorescence quantum yield of biomass CDs.•The dual-channel ratio sensing platform is derived from the fluorescence emission of CDs and antibiotic-Eu complex.•Realized visual identification and quantitative detection of OTC.•Revealed the resonance effect of water molecules bound with Eu-antibiotics and its influence. In this work, blue carbon dots (Stalk-Trp CDs) with high fluorescence quantum yield were successfully prepared from biological waste cherry tomato stalk and tryptophan. The morphology, composition, and properties of Stalk-Trp CDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, ultraviolet–visible absorption spectroscopy, and fluorescence spectroscopy. On this basis, a dual-channel ratio sensing platform (Stalk-Trp CDs@Eu) was constructed using the interaction of Stalk-Trp CDs with Eu3+, which reduced the detection limit of the antibiotic oxytetracycline from 0.15 µmol/L to 0.018 µmol/L. Channel 1 of the dual-channel ratio sensing platform is a neutral environment (pH = 6.5), and the specific response of the probe to OTC causes its fluorescence to change from blue to purple. Channel 2 is an alkaline environment (pH = 11.5), and the fluorescence of the probe turns green only in the presence of OTC. The interaction mechanism of the dual-channel ratio sensing platform with the antibiotics oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC) was also revealed. The detection results of OTC in honey and milk by using Stalk-Trp CDs@Eu were highly consistent with the HPLC method recommended by the national standard. This shows that the dual-channel ratio sensing platform has great practical application value in the field of antibiotic detection.