Tuning Cu₂O Shell on Gold Nanocube Core Employing Amine-Functionalized Silane for Electrocatalytic Nitrite Detection

A facile synthetic method for depositing copper(I) oxide (Cu2O) shell on Au nanocube (AuNC) core with different core–shell ratios (1:1, 1:5, 1:10, and 1:20) is reported. An innovative approach of tuning the Cu2O nanoshell for utilizing the catalytic activity of the AuNC@Cu2O core–shell nanostructures is investigated. N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TPDT) silane played a dual role in the formation and stabilization of the Cu2O shell on the AuNC core. The optimal concentration of TPDT silane required for forming a stable Cu2O shell is studied systematically and deployed for fabricating AuNC@Cu2O core–shell nanostructures with various core-to-shell ratios. UV–vis absorption spectroscopy, high-resolution electron transmission microscopy analyses, scanning electron microscopy coupled with line scan energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and inductively coupled plasma mass spectrometry techniques were used to characterize the prepared AuNC@Cu2O core–shell nanostructures. High-angle annular dark-field scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy mapping images–line scan image and scanning electron microscopy coupled with line scan energy-dispersive X-ray spectroscopy were recorded to understand the core–shell nature of AuNC@Cu2O nanostructures. The electrocatalytic activity of AuNC@Cu2O core–shell nanostructures with different Cu2O shell thicknesses toward nitrite detection was investigated using the cyclic voltammetry technique. The TPDT-stabilized AuNC@Cu2O nanostructure with the core–shell ratio of 1:10 showed the best electrocatalytic activity, and the estimated detection limit of nitrite concentration was found to be as low as 14.7 nM.