MXene-enabled disposable electrochemical sensor array for rapid determination of esculetin and quercetin in the herb of Viola tianschanica Maxim

A fully printed high-performance nanomaterial-modified electrochemical sensor. • Sensor array enables co-detection of esculetin and quercetin in Chinese herbs. • EC combined with SPE enables highly sensitive assaying target in complex samples. • MXene/MWCNTs decorated SPSA exhibits low resistance and excellent activity. Viola tianschanica Maxim is a crucial medicinal herb in traditional Chinese medicine. However, current rapid quality evaluation methods for Chinese medicine herbs face significant limitations, thereby hindering the industrial development of cultivation and processing. Here, a fully screen-printed sensor array (SPSA) decorated with Ti 3 C 2 T x /MWCNTs was prepared and applied for the determination of key bioactive compounds (esculetin and quercetin) listed in the Chinese Pharmacopoeia. Ti₃C₂Tₓ and MWCNTs were directly formulated into a printable ink, enabling a single-step fabrication of the nanomaterial-modified sensor interface via screen-printing. This approach largely avoids the cumbersome multi-step modification procedures and the resulting batch-to-batch performance variations inherent in the conventional fabrication of electrochemical sensors. The composite exhibits a pronounced synergistic effect: MXene with abundant terminal functional groups effectively adsorbs the analytes, while the MWCNTs network provides rapid electron transfer pathways. Electrochemical studies revealed that both esculetin and quercetin undergo an adsorption-controlled process on the electrode surface, following a quasi-reversible two-proton, two-electron transfer mechanism and exhibiting excellent electrochemical activity in acidic buffer systems. The SPSA demonstrated a linear response range of 2–200 μmol/L for both analytes, with a detection limit (LOD) of 10 nmol/L (S/N = 3). In addition, with the assistance of solid phase extraction for purifying and enriching the analytes in herbal samples, the SPSA exhibited good selectivity, robustness, and accuracy. No significant difference was observed between the results obtained by the SPSA and those obtained by conventional HPLC-PDA, confirming the high practical value of this strategy for rapid quality assessment in Chinese medicine cultivation, processing, and trade. Download: Download high-res image (230KB) Download: Download full-size image