Multishell Au@Ag@SiO2 nanorods embedded into a molecularly imprinted polymer as electrochemical sensing platform for quantification of theobromine.

A highly uniform and monodisperse silica-encapsulated Au@Ag multilayered core-shell nanorods (~ 80 nm in length) has been prepared with excellent electrocatalytic properties. Using the Au@Ag@SiO2 nanoassemblies to substantially enhance the sensitivity and the sol-gel molecularly imprinted polymer (MIP) with imprinted cavities to present special molecular recognition sites, a novel electrochemical sensing platform was rationally designed, fabricated, and tested for efficient theobromine (THB) quantification. The formation of final Au@Ag@SiO2@MIP was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The performance of the Au@Ag@SiO2@MIP modified electrode was evaluated by differential pulse voltammetry with the changes in peak current of hexacyanoferrate redox probe measured at a working potential of 0.2 V (vs. saturated calomel electrode) as determination signal. Under optimal conditions, the quantitation of THB was attained in a broad linear range from 10 nM to 100 µM with a detection limit of 8.0 nM. The selectivity of Au@Ag@SiO2@MIP was examined according to its recognition to THB and the interferents. Finally, the sensing platform was successfully applied to extract and determine THB from food, biological, and environmental samples with acceptable recoveries (92.20-107.1%) and relative standard deviation < 4%. The propsed sensor provides a robust means for monitoring alkaloids in complex matrices and a promising opportunity to develop sensitive and selective electrode materials with good reusability. Graphical abstract.