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A ratiometric fluorescence probe is proposed for sensitive and visual detection of tetracyclinee (TC) based on cascade fluorescence signal amplification induced by bovine serum albumin–stabilized copper nanoclusters (BSA-CuNCs) and yttrium ions (Y3+). TC can combine with Y3+ to form the complex (TC-Y3+) to enhance the fluorescence of TC at 515 nm. Then, positively charged TC-Y3+ and negatively charged BSA-CuNCs was bonded together by electrostatic interactions to achieve the fluorescence resonance energy transfer (FRET) process. With the increase of TC concentration, the fluorescence intensity of TC-Y3+ at 515 nm (F515) gradually increased; meanwhile, the fluorescence intensity of BSA-CuNCs at 405 nm (F405) decreased gradually. The ratio of F515 and F405 was used for the quantitative determination of TC. The linear range of the constructed fluorescent probe is 1.0 to 60.0 μM, and the limit of detection is 0.22 μM. The method was successfully applied to the determination of TC in spiked milk with recoveries ranging from 94.3 to 112%. Furthermore, the color of this platform can be observed from dark violet to bright green under the UV lamp. Since the response time of the reaction is less than 10 s, an intelligent sensing platform based on the use of the smartphone as image acquisition equipment was also established to realize rapid on-site and portable detection of TC through the colorimetric recognition application. [ABSTRACT FROM AUTHOR]