Investigation of Mn doped ZnO nanoparticles towards ascertaining myocardial infarction through an electrochemical detection of myoglobin

Mn-doped ZnO nanostructures were synthesized with three different estimated Mn concentration (atoms/cm³) using sol-gel technique. As synthesized nanostructures were analyzed using X-ray diffraction spectroscopy (XRD), Fourier-transform-infrared spectroscopy (FTIR), and field-emission secondary electron microscopy (FE-SEM). XRD pattern reveals of doped ZnO nanostructures reveal a peak related to Zn₂Mn₃O₈ phase along with peaks related to pure ZnO. Average particle size, estimated using Scherer formula, increases with Mn-doping. FE-SEM reveals morphological change from spherical particles (∼15-20 nm) to nano-rods then nano-belt like 2 D super lattice structure after doping. Optical band gap obtain from Tauc's plot is 3.82, 2.05, 2.1 and 2.47 eV for pure-ZnO and Mn-doped samples with 13×10¹⁷, 20×10¹⁷ and 32×10¹⁷ Mn atoms/cm³, respectively. Presence of vibration band from 665 to 680 cm⁻¹ in FTIR spectra endorses metal oxide formation. Nanomaterials were screen printed over working electrode of pre-fabricated three terminal electrode. This was used for electrochemical detection of myoglobin (Mb); a biomarker for acute myocardial infarction and were tested for Mb concentrations from 0-15 nM using cyclic voltammetry and electrochemical impedance spectroscopy. Redox current and charge transfer resistance varied linearly with Mb concentration. 7-fold increased sensitivity towards Mb in Mn-doped ZnO sensors is attributed to doping induced stress in nanostructures. Maximum sensitivity of 95µA-cm⁻² nM⁻¹ with LOD of 0.35 nM is observed for ZnO with 13 × 10¹⁷ Mn atomic/cm³. Response time of ∼10 ms is observed. Interference carried out with 7 nM Cytochrome c and 5 mM HSA reveal different oxidation potential and current value for Mb.