Polyaniline/MWCNTs/starch modified carbon paste electrode for non-enzymatic detection of cholesterol: application to real sample (cow milk).

Nanocomposite materials are potentially revolutionizing many technologies, including sensors. In this paper, we described the application of "PANI/MWCNTs/Starch" modified carbon paste electrode (PCS-CPE) as a simple and highly sensitive cholesterol sensor. This novel nano-composite material has integrated nano-morphology, where polyaniline could interact effectively with the additives; pi-pi stacking "MWCNTs," and covalently bonded with starch. Specific binding sites (sugar chains), better electro-catalytic properties and fast electron transfer facilitated the oxidation of cholesterol. Fourier transform infrared spectra confirmed the interaction of cholesterol with the composite material. The sensing response of PCS was measured by cyclic voltammetry and chronoamperometry (0.1 M PBS-5 used as supporting electrolyte). As the amount of cholesterol increased in the test solution, cyclic voltammograms showed a rise of peak current (cathodic and anodic). Under the normal experimental conditions, the developed sensor exhibited wide linear dynamic range (0.032 to 5 mM) (upper limit is due to lack of solubility of cholesterol), high sensitivity (800 µAmM-1 cm-2), low detection limit (0.01 mM) and shorter response time (within 4-6 s). Analytical specificity, selectivity, and sensitivity during cholesterol estimation were compared with the response of some other analytes (ascorbic acid, glucose, l-dopa, urea and lactic acid). This novel sensor was successfully applied to estimate cholesterol in cow milk (used as a model real sample). The sensing platform is highly sensitive and shows a linear response towards cholesterol without using any additional redox mediator or enzyme, thus this material is extremely promising for the realization of a low-cost integrated cholesterol sensor device. Graphical abstract Cyclic voltammetric response of cholesterol of composite modified carbon paste capillary electrode.

Preparation and characterization of green-nano-composite material based on polyaniline, multiwalled carbon nano tubes and carboxymethyl cellulose: For electrochemical sensor applications.

In this paper, we are presenting the preparation and characterization of "polyaniline/multiwalled carbon nanotubes/carboxymethyl cellulose" based novel composite material. It's morphological, thermal, structural, and electrochemical properties were investigated by using different instrumental techniques. During the in-situ chemical polymerization of aniline in the aqueous suspension of CMC and MWCNTs, the particle size change in two different ways "top to bottom" (low molecular weight oligomers grows in size) and "bottom to top" (long fibers of CMC fragmented in the reaction mixture). The combination of these two processes facilitated the fabrication of an integrated green-nano-composite material. In addition, a little amount of conductive nanofillers (MWCNTs) boosts the electrical and electrocatalytic properties of the material. Electron-rich centers of benzenoid rings exhibited π-π stacking with sp2 carbon of MWCNTs. CMC dominantly impact on the properties of PANI, negatively charged carboxylate group of CMC ionically bonded with protonated amine/imine. FTIR and Raman analysis confirmed that the material has dominated quinoid units and effective charge transfer. Hydroxyl and carboxyl groups and bonded water molecules of CMC results in a network of hydrogen bonds (which induced directional property). PANI/MWCNTs/CMC have nanobead-like structures (TEM analysis), large surface area, large pore volume, small pore diameter (BET and BJH studies) and good dispersion ability in the aqueous phase. Nanostructures of aligned PANI exhibited excellent electrochemical properties have attracted increasing attention. Modified carbon paste electrode was used for electrocatalytic detection of ascorbic acid (as a model analyte). The sensor exhibited a linear range 0.05 mM-5 mM, sensitivity 100.63 µA mM-1 cm-2, and limit of detection 0.01 mM. PANI/MWCNTs/CMC is suitable nanocomposite material for apply electroactive/conducting ink and membrane (which could be used in electrochemical sensor applications).

Polyaniline/multiwall carbon nanotubes/starch nanocomposite material and hemoglobin modified carbon paste electrode for hydrogen peroxide and glucose biosensing.

This paper describes the application of novel nanocomposite material polyaniline/multiwall carbon nanotubes/starch (designated as PCS) as a good electrode material for electrochemical sensing. The developed ternary composite system has manifold interactions and synergistic improved properties - high surface area, good electro-activity, conductivity, stable dispersion, biocompatible, hydrophilic and hydrophobic regions, multifunctional, and nanoturmeric shape morphology. Hydrogen peroxide biosensor was fabricated as a model system using PCS and hemoglobin (HB) modified carbon paste electrode. PCS and HB compatible and effectively communicate with each other, facilitate the charge transfer (potassium ferricyanide used as electroactive marker). Thus, PCS and HB (in combination) is a good electrode material for sensitive and selective detection of peroxide. The developed biosensor showed a linear range (0.1 mM-5 mM, R2 = 0.9975), limit of detection (0.032 mM), sensitivity (76.43 µA/mM cm2) and long-term storage and stability. This material could be used a platform to develop some other sensors by using other redox enzymes. As a model, we incorporate glucose oxidase to detect Glucose. Thus, the favorable properties indicate that the proposed material system suitable for low-cost sensor strips.