Dispersed iron on N,F-doped porous carbon derived from tea waste for caffeic acid electrochemical detection

N,F co-doped porous carbon materials were synthesized from waste tea leaves via a facile pyrolysis approach. • Highly dispersed Fe species and abundant Fe-N x active sites enhanced electrocatalytic activity toward caffeic acid. • The Fe/N,F-TC-0.25/GCE sensor exhibited a wide detection range (0.05–100 μM) and a low detection limit of 0.014 μM. • Synergistic effects of porous carbon structure and Fe-N x sites improved electron transfer and sensing performance. • The sensor reliably caffeic acid in tablet and blueberry samples, confirming practical applicability. Caffeic acid (CA), a phenolic compound widely present in natural foods, exhibits multiple pharmacological activities and plays an important role in regulating food quality. However, its dose-dependent biotoxicity and the demand for accurate determination in complex matrices pose significant challenges to analytical techniques. In this study, waste tea leaves were employed as a biomass-derived carbon source naturally containing elements such as N and F. Through Fe 3+ pre-complexation followed by pyrolysis, N,F co-doped porous carbon modified with highly dispersed Fe species was obtained. Under optimized conditions, the constructed Fe/N,F-TC-modified glassy carbon electrode (Fe/N,F-TC/GCE) electrochemical sensor exhibited excellent performance for CA detection. This superior performance can be mainly attributed to the porous structure of N,F-TC, which facilitates CA mass transfer and enhances reaction efficiency. Meanwhile, the high density of Fe-N active sites provides abundant catalytically active centers. Their synergistic catalytic effect significantly amplifies the redox signal of CA, thereby improving the electrocatalytic activity. The Fe/N,F-TC-0.25/GCE electrode showed a good linear response in the range of 0.4–7 μM and an overall working range over 0.05–100 μM. The statistically estimated limit of detection (LOD) was as low as 0.014 μM. Moreover, the sensor was successfully applied to the spiked detection of CA in tablet and blueberry samples, with recoveries close to 100%, demonstrating the excellent analytical performance of this method and its applicability to real-sample analysis. This study provides a simple, environmentally friendly, efficient, and sensitive detection strategy for CA related food quality control and pharmaceutical analysis, highlighting both theoretical significance and practical application potential. A Fe-containing N,F co-doped porous carbon (Fe/N,F-TC) was constructed from waste tea leaves through Fe 3+ pre-coordination followed by pyrolysis. The hierarchical porous framework, highly dispersed Fe species, and Fe-N x sites facilitate CA mass transport and electrocatalytic oxidation, markedly enhancing the electrochemical sensing performance toward caffeic acid. Download: Download high-res image (198KB) Download: Download full-size image