Smartphone-integrated fluorescent aerogel sensor using ionic liquid modified carbon dots for visual quantification of total polar materials in edible oils

G-CDs polarity probe synthesized via ionic liquid modification. • Dual-mode platform: fluorescence and smartphone colorimetry. • Aerogel sensor enables on-site TPC detection in oils. The content of total polar materials (TPM) in edible oil is a critical indicator for evaluating oil quality. In this study, a novel dual-mode sensing platform integrating fluorescence spectrometry and smartphone-based colorimetric analysis was developed for the rapid and on-site detection of TPM. The platform is based on green-emitting carbon dots (G-CDs) synthesized via a one-step solvothermal method using 1-hexyl-3-methylimidazolium tetrachloroferrate ([HMIM]FeCl₄) and o -phenylenediamine (o-PDA) as precursors. The G-CDs exhibit strong polarity-responsive fluorescence quenching upon exposure to TPM, enabling sensitive fluorescence detection with limits of detection (LODs) of 0.29%, 0.64%, and 0.16% for soybean, peanut, and rice oils, respectively, over a wide linear range of 1.81%–58.01%. Notably, by loading G-CDs onto a wood sponge aerogel, a portable fluorescent sensor was constructed. When coupled with a smartphone for colorimetric readout, this sensor achieved significantly improved LODs of 0.09%, 0.13%, and 0.11% for the three oils—surpassing both the fluorescence method in this work and many previously reported TPM sensing approaches—while maintaining a comparable broad linear range. Analysis of actual oil samples showed good agreement with the national standard method (GB 5009.202–2016). This work demonstrates that the integration of a G-CDs-based aerogel sensor with smartphone colorimetry offers a simple, sensitive, and field-deployable tool for TPM monitoring in edible oils. Download: Download high-res image (122KB) Download: Download full-size image