A Self-Calibrating Sensing Platform Based on Amine-Responsive Excitation Wavelength-Dependent Fluorescent Polymers for Real-Time and Visual Detection of Food Freshness

Accurate assessment of food freshness is critical to maintaining human health. However, the complex environment of food usually leads to false-positive measurements result. Therefore, the development of sensing platforms with self-calibration for accurate detection of food freshness in complex environments is essential. Here, using the green fluorescence-emitting FITC-ene and the red fluorescence-emitting DBA-ene-Eu3+ as fluorescent units, fluorescent polymeric materials P1-P4 with excitation wavelength-dependent (254 and 365 nm, matched with standard UV lamp) emission are prepared. P1-P4 responded rapidly to biogenic amines (BAs). Among them, P3 exhibits the widest linear range, and the most noticeable fluorescence color change (from orange-red to yellow-green) under 254 nm excitation and enhanced green fluorescence under 365 nm excitation. The changes of P3-prepared labels at different excitation wavelengths can be utilized to rapidly evaluate the food's freshness. Furthermore, by using a smartphone to read the Red/Green/Blue values of the labels, the total volatile basic nitrogen (TVBN) values can be output to quantitatively evaluate the food freshness, and the output TVBN values at different excitation wavelengths are utilized for mutual calibration to improve the accuracy of the estimation results. This self-calibrating sensing platform is fast and nondestructive, which provides an effective method for the accurate evaluation of food freshness. As food spoilage increased, the excitation wavelength-dependent luminescent polymer P3-prepared labels shows a purplish-red-to-green fluorescence change as well as an turn-on of green fluorescence under 254 and 365 nm UV lamps, respectively. By using a smartphone to read the R/G/B values of fluorescent labels at different excitation wavelengths to output TVBN values, self-calibration of the evaluation results can be achieved. image