CNT/Al2O3 core–shell nanostructures for the electrochemical detection of dihydroxybenzene isomers

Abstract

We report CNT/Al₂O₃ core–shell nanostructures for the electrochemical detection of dihydroxybenzene (DHB) isomers. Amorphous films of Al₂O₃ (1.2–15.4 nm in thickness) are uniformly deposited onto the inner and outer walls of CNTs by atomic layer deposition. The effect of the Al₂O₃ shell thickness on the electrochemical detection of dihydroxybenzene isomers was explored using cyclic and square-wave voltammetry. The best sensing properties are found at a shell thickness of approx. 2.4 nm (CNT/Al₂O₃(9) sensor), where the oxidation peak currents (sensor-signal) increased ca. 10 times as compared to a sensor fabricated with non-coated CNTs. All of the three DHB isomers (hydroquinone, catechol and resorcinol) are independently detected in the concentration ranges of 2–1000 μmol L⁻¹, 0.5–700 μmol L⁻¹ and 3.5–500 μmol L⁻¹, respectively. The sensors show reliable repeatability, reproducibility, long-term stability, and applicability in the analysis of real samples. Based on these findings, a plausible mechanism is proposed highlighting the role of the Al₂O₃–shell.