Carbon Dots and a CdTe Quantum Dot Hybrid-Based Fluorometric Probe for Spermine Detection

Spermine is an indicator of the meat freshness, and thus, developing efficient approaches with low cost for spermine detection is highly desirable. Here, we report a fluorometric probe for the sensitive and selective detection of spermine. This probe is composed of blue fluorescent carbon dots (CDs) and red fluorescent cadmium telluride quantum dots (CdTe QDs), in which CdTe QDs act as the response signal and CDs as the internal reference. The red fluorescence of CdTe QDs is efficiently quenched, while the CD fluorescence remained constant with the addition of spermine, leading to a distinguishable fluorescent color variation of the probe solution from shallow pink to blue. This probe can selectively identify spermine from other organic amines with a low limit of detection (76 nM). Furthermore, a ratiometric fluorescent paper is developed and employed as an on-site, rapid-responsive, and cost-effective method for real time and visually monitoring the freshness of pork.