An Electrochemical Sensor Based on a Facile Synthesis of Chitosan-Blend-Polyaniline Decorated COOH-MWCNT-Hollandite/ α -MnO2 Nanocomposites for Creatinine Detection

This article comprehensively reports novel synthesis of bio-compatible and sustainable nano-composite based electrochemical sensor comprising of natural and conducting polymers; chitosan (CHIT) and polyaniline (PANI), carboxylic acid functionalized multiwalled carbon-nanotubes (COOH-MWCNTs) and transition metal oxide; Hollandite $\left(\alpha \right.$ -MnO2), an allotrope of manganese dioxide for creatinine (CRE) detection. A facile chemical solution methodology is utilized for the synthesis process. The work emphasizes on a novel anatomical approach that promises excellent CRE affinity. $\left(\alpha \right.$ -MnO2) is ingeniously encapsulated within the nano-tubes of COOH-MWCNT $\left(\alpha \right.$ -MnO2@COOH-MWCNT) and thereafter, blended polymers (CHIT-b-PANI) are decorated over $\left(\alpha \right.$ -MnO2@COOH-MWCNT) conjugate. The final composite obtained is CHIT-b-PANI/ $\alpha$ -MnO2@COOH-MWCNT. Drop coating technique is implemented to deposit CHIT-b-PANI/MnO2@COOH-MWCNT on indium tin oxide (ITO) laminated glass plate. Powder X-ray diffraction (P-XRD), high resolution transmission electron microscopy (HR-TEM), field emission transmission electron microscopy (FETEM), field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), atomic field microscopy (AFM), Fourier transform infrared spectroscopy (F-TIR), and UV-Visible Spectroscopy confirmed the successful anatomical morphology and chemical conformation of CHIT-b-PANI/ $\alpha$ -MnO2@COOH-MWCNT. The electro-catalytic affinity of CHIT-b-PANI/ $\alpha$ -MnO2@COOH-MWCNT/ITO toward CRE is investigated in a three electrode arrangement with a buffer solution (0.1 M, pH 8) containing commercial CRE in different concentrations $(1-334.46 \mu \mathrm{M})$ . The developed CRE electrochemical sensor displayed excellent CRE-compatibility results exhibitin wider detection range, 1–243.48 $\mu \mathrm{M}$ (Regression coefficient, R2 = 0.9601), inflated sensitivity of 3204.02 $\mu \mathrm{AmM}^{-1}$ low LOD and LOQ of 1.02 and 3.12 $\mu \mathrm{M}$ . Superior temperature stability $\left(30^{\circ} \mathrm{C}-60^{\circ} \mathrm{C}\right)$ , excellent anti-interference characteristics (COV 3.75%); exorbitant reproducibility (COV 0.75%), highly acceptable repeatability (COV 1.32%) and broader storage stability of eight months (COV 5.34%) assured optimum sustainability of the developed sensor.