Engineered carbon electrode with graphene-cyclodextrin/ferrocenyl-carnosine nanoassembly for Mn(ii) detection

The modification of electrodes using carbon-based nanomaterials is an efficient strategy for enhancing their electrical conductivity and working surface area. In this study, we explore the ability of a screen-printed carbon electrode (SPCE) modified with graphene-cyclodextrin/ferrocenyl-carnosine (GCD/FcCAR) supramolecular assembly for the determination of Mn(ii) in an aqueous solution. Although Mn(ii) is an essential nutrient for humans, it can be toxic at elevated levels, leading to neurotoxic symptoms. Consequently, accurate analytical determination is necessary. The graphene platform (G-Alk) was derivatized with mono-6-deoxy-6-azido-β-cyclodextrin (CD) via a click chemistry reaction. The chemical-physical properties of the GCD system were investigated using thermogravimetric analysis, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. An aliquot of GCD dispersion was cast on the surface of the SPCE (SPCE/GCD), and its electrochemical response was evaluated using cyclic voltammetry (CV) with [Fe(CN)₆]^3- as the redox probe. A notable 30% increase in the signal was observed for SPCE/GCD compared with the bare SPCE. Additionally, the remarkable metal-ion complexing and electroanalytical abilities of FcCAR were leveraged in this study. Therefore, CV and differential pulse voltammetry (DPV) experiments were conducted to assess the voltammetric response of FcCAR on SPCE/GCD (SPCE/GCD/FcCAR) toward Mn(ii). DPV measurements allowed us to obtain a limit of detection (LOD) and limit of quantification (LOQ) of 0.69 and 2.3 nmol L^-1, respectively, within a linear concentration range (0.17 ≤ [Mn(ii)]/nmol L^-1 ≤ 48). The LOD obtained is one of the lowest reported in the literature, highlighting the potential applicability of the SPCE/GCD/FcCAR system for Mn(ii) determination in aqueous solutions.