Porphyrin-functionalized molecularly imprinted paper sensor for selective colorimetric detection of caffeine in...

In this work, a novel portable paper-based sensor is developed using a porphyrin-embedded molecularly imprinted polymer for caffeine quantification. This study entraps tetraphenylporphyrin (TPP) within the template-induced cavities of cellulose molecular aggregation-polished porous particles, thereby modulating TPP's optical response. All techniques (FTIR, XRD, and TEM) demonstrated successful polymer formation with selective binding cavities and reversible caffeine interactions via non-covalent forces. The sensor covered a linear range of 1-100 µM with a 1.62 µM limit of detection and a Stern-Volmer correlation (R ² = 0.99). Stability was demonstrated with high selectivity, an imprinted factor of ∼3, over 85% response after five cycles, and less than <10% signal loss over 30 days. Average recoveries of 93-99% (real-samples analysis - tea, coffee) provide a cost-effective and readily interpretable approach for the field-based monitoring of caffeine.