A smartphone-based tunable tyrosinase functional mimic modulated portable amperometric sensor for the rapid and real-time monitoring of catechol

Abstract

A smartphone-based electrochemical sensor for rapid detection of catechol (CC) was designed. The system contained a smartphone, a hand-held detector, and tyrosinase enzyme mimicking material modified screen-printed carbon electrode (SPCE). Metal nanoparticles confined in porous carbon have been widely used as enzyme mimics owing to their enhanced electrochemical activity. However, the fabrication of enzyme-mimicking catalysts in a scalable and tunable manner is challenging. A two-step synthesis strategy was followed: carbonization of the silica template to form cubic-structured mesoporous carbon (CMC) and high-temperature calcination for copper confinement into CMC (Cu–CMC). The non-covalent interactions enable the Cu precursors to coordinate with the carbon atoms in the face-centered cubic lattice of CMC. The uncalcined material is the as-synthesized (As–Cu–CMC), while the 900 °C calcined are stage 1 (Cu–CMCS1) and stage 2 (Cu–CMCS2) materials with different Cu loadings. The Cu–CMCS2 possess a large pore volume (0.224 cm3g−1) and high surface area (104.2 m2/g). The Cu–CMCS2 modulated sensors enable rapid and real-time detection of CC. Under optimized conditions, the linear range of 1.0–1000 µM (0.0 V vs. integrated Ag/AgCl reference electrode) with the sensitivity and lower detection limit of 10.21 µA µM−1 cm−2 and 0.099 μM (S/N=3) was achieved. The excellent sensor performance is attributed to the increased number of Cu vacancies that mimic the native tyrosinase enzyme. The sensor connected to a portable potentiostat enable high-throughput real-time testing of the CC without sophisticated equipment. Furthermore, the sensor detected CC in green tea and water samples, and the results were validated using UV–visible spectrophotometry and high-performance liquid chromatography.Abbreviations: CMC, cubic-structured mesoporous carbon; Cu–CMCS2, copper loaded stage 2 material; CC, catechol; CMS, cubic mesoporous silica; SPCE, screen-printed carbon electrode; HF, hydrofluoric acid; P123, Pluronic 123; TEOS, Tetraethyl orthosilicate; AA, ascorbic acid; Glu, glucose; HQ, hydroquinone; 4-NP, 4-nitrophenol; CA, caffeic acid; RS, resorcinol; Cu–CMCS1, copper loaded stage 1 material; UV–Vis, UV–visible spectrophotometry; FE-SEM, field-–emission scanning electron microscopy; EDS, energy–dispersive X–-ray spectroscopy; Si, silica; TEM, transmission electron microscopy; NPs, nanoparticles; SAED, selected area electron diffraction; FT-IR, Fourier-Transform Infrared Spectroscopy; BET, Brunauer–Emmett–Teller; BJH, Barrett–Joyner–Halenda; TGA, Thermogravimetric analysis; CV, cyclic voltammetry; ipa, anodic peak current; ECSA, electrochemically active surface area; EIS, electrochemical impedance spectroscopy; Rct, charge-transfer resistance; CA, chronoamperometry; LOD, limit of detection.