Bifunctional Nitrogen‐Doped Yellow‐Green Carbon Dots: Integrated Fluorescent Probe for Sensitive Antibiotic Detection and Oxygen “Breathing Color” Tracking

Nitrofurantoin (Nit), a widely used antimicrobial agent classified as a Group 3 carcinogen, demands rapid, sensitive detection and practical monitoring for environmental and food safety. This study's unique contribution lies in developing bifunctional nitrogen‐doped yellow‐green carbon dots (YG‐CDs) integrating sensitive Nit detection and oxygen “breathing color” tracking. YG‐CDs were synthesized via a one‐step solvothermal method using bromothymol blue and 2‐mercaptobenzimidazole, with structural/optical characterization via Fourier transform infrared, X‐ray photoelectron spectroscopy, UV–vis, and fluorescence spectroscopy; YG‐CDs‐gelatin composites were fabricated for visualization. Key findings: YG‐CDs emit at 555 nm (long‐wavelength) with a quantum yield of 26.1%, excellent stability (salt, temperature, UV), and high selectivity/anti‐interference for Nit, achieving a detection limit of 2.1 μM and 96.5–100.5% recovery in lake water. The YG‐CDs‐gelatin composite exhibits oxygen‐responsive color shifts (yellow‐green to green), enabling instrument‐free food freshness monitoring. This work provides a novel, integrated strategy for on‐site antibiotic residue detection and intelligent packaging, advancing practical applications in environmental monitoring and food safety.