Electrochemical insights into manganese-cobalt doped $\alpha-Fe_2O_3$ nanomaterial for cholesterol detection: A comparative approach
Herein, a self-assembled hierarchical structure of hematite ($\alpha$-$Fe_2O_3$) was synthesized via a one-pot hydrothermal method. Subsequently, the nanomaterial was doped to get $M_{x}Fe_{2-x}O_3$ (M = Mn-Co; x = 0.01, 0.05, 0.1) at precise concentrations. The electrode was fabricated by coating the resulting nanocomposite onto a Nickel Foam (NF) substrate. The electrochemical characterization demonstrated the excellent performance of cobalt-doped $\alpha$-$Fe_2O_3$, among which, $Co_0.05Fe_0.95O_3$ (CF5) exhibited superior performance, showing a two-fold increase in sensitivity of 1364.2 $\mu$A.m$M^{-1}$.$cm^{-2}$ $(\pm 0.03, n = 3)$ in 0.5 M KOH, a Limit of Detection (LOD) of $\sim 0.17 mM$, and a Limit of Quantification (LOQ) of {\sim}0.58 mM. Density Functional Theory (DFT) was performed to understand the doping prompting in the reduced bandgap. The fabricated electrode displayed a rapid response time of 2 s and demonstrated 95% stability, excellent reproducibility, and selectivity, as confirmed by tests with several interfering species. A comprehensive evaluation of the electrode's performance using human blood serum highlighted its robustness and reliability for cholesterol detection in clinical settings, making it a promising tool for clinical and pharmaceutical applications.