In this work, we report the synthesis of MnO2/RGO (reduced graphene oxide)/P25 nanocomposites for a non-enzymatic hydrogen peroxide sensor. MnO2/RGO/P25 nanocomposites were synthesized with a photo-reduction approach and characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. A non-enzymatic hydrogen peroxide sensor was fabricated by dropping MnO2/RGO/P25 nanocomposites on the surface of a glassy carbon electrode. Electrochemical measurements of the MnO2/RGO/P25 modified electrode were carried out on an electrochemical workstation. The as-prepared sensor exhibited high electrocatalytic activity, selectivity and stability towards the oxidation of H2O2. Under optimum conditions, the calibration curve for H2O2 determination was linear in the range from 1.0 × 10−6 to 4.0 × 10−3 M (R2 = 0.999) with a detection limit of 3 × 10−7 M (S/N = 3).

•Bio-functionalization of rGO by NC-assisted BSA based on π-stacking interaction.•The BSA-NC-rGO nanocomposite possesses properities of excellent biocompatibility, high specific surface area, good hydrophilcity and stability.•A novel electrochemical impedance biosensor was fabricated based on the AuNPs/BSA-NC-rGO nanocomposite for CEA determination.•The proposed biosensor possesses a wide range of 0.1−200 ng mL−1.A novel protocol of label-free electrochemical impedance immunosensor based on bovine serum albumin-nitidine chloride-reduced graphene oxide (BSA-NC-rGO) nanocomposite was proposed for quantitative determination of carcino-embryonic antigen (CEA). BSA was anchored to rGO via the aromatic plane of NC by π-stacking interaction to realize bio-functionalization of rGO, and then gold nanoparticles (AuNPs) were electrodeposited onto the surface of BSA-NC-rGO nanocomposite. The morphology, conductivity and interaction of different nanocomposites were characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and UV–vis spectrum. CEA monoclonal antibody (anti-CEA) was conjugated to AuNPs via gold-thiol chemistry to construct electrochemical immunosensing platform, and the specific immunoreaction between CEA and anti-CEA was monitored by EIS. Under optimum conditions, CEA could be quantified in a wide range of 0.1–200 ng mL−1 (R=0.9948) with low detection limit of 0.067 ng mL−1. The proposed immunosensor exhibited great potential for detecting blood samples.

•The AuNPs/dsDNA-GO nanocomposite was synthesized and applied for thrombin biosensing.•GO was covalently functionalized with dsDNA via a facile amidation process, which improves the dispersibility of GO in PBS.•The developed electrochemical impedance aptasensor showed a good analytical performance.A novel label-free electrochemical impedance aptasensor based on a gold nanoparticles/double-stranded DNA-graphene (AuNPs/dsDNA-GO) nanocomposite modified glassy carbon electrode was presented for quantitative determination of thrombin. GO was covalently functionalized with dsDNA via a facile amidation process, and then AuNPs were electrodeposited onto the surface of dsDNA-GO. The morphology, conductivity and interaction of the as-prepared nanocomposites were characterized by scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy (EIS), Raman and Fourier transform infrared spectroscopy. The thrombin-binding aptamer (TBA) was conjugated to AuNPs via gold-thiol chemistry to construct electrochemical aptasensing platform, and the specific recognition between TBA and thrombin was monitored by EIS. Under optimum conditions, thrombin could be quantified in a wide range of 0.1–100 nM (R2 = 0.9960) with low detection limit of 0.06 nM (S/N = 3).

•GMCFs were synthesized by electrospinning and calcination in an Ar atmosphere.•Graphene enhances the electrocatalytic activity of MnCo2O4 nanofibers.•Spinel-type nanofibers as supports are beneficial to graphene distribution.•GMCF/GCE exhibits excellent electrocatalytic activity towards glucose oxidation.Graphene decorated MnCo2O4 composite nanofibers (GMCFs) were synthesized by electrospinning and subsequent calcination in an Ar atmosphere. The structural and morphological characterizations of GMCFs were performed using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, energy-dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. The synthesized GMCFs combine the catalytic activity of spinel-type MnCo2O4 with the remarkable conductivity of graphene. In addition, electrospinning can process MnCo2O4 materials into nanosized architectures with large surface area to prevent magnetic nanoparticles from aggregating. The obtained GMCFs were applied as a novel platform for glucose biosensing. Electrochemical studies show that the developed biosensor exhibits excellent electrocatalytic activity towards glucose oxidation over a wide linear range of 0.005–800 µM with a low detection limit of 0.001 µM.

Spinel-type MnCo2O4 nanofibers (MCFs) were successfully synthesized by electrospinning and sequential calcination. The crystal structure, composition and morphology of the synthesized MCFs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Due to the outstanding electron-transfer ability of spinel MnCo2O4 and the large surface area of nanofibers, the synthesized MCFs were employed as electrocatalysts for the oxidation of glucose. Cyclic voltammetry and amperometry were used to evaluate the electrocatalytic activities of the MCFs towards glucose. The non-enzymatic glucose sensor showed a wide linear range of 0.05–800 μM with a low detection limit of 0.01 μM (S/N = 3).

Spinel-type MnCo2O4 nanofibers (MCFs) were successfully synthesized by electrospinning and sequential calcination. The crystal structure, composition and morphology of the synthesized MCFs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Due to the outstanding electron-transfer ability of spinel MnCo2O4 and the large surface area of nanofibers, the synthesized MCFs were employed as electrocatalysts for the oxidation of glucose. Cyclic voltammetry and amperometry were used to evaluate the electrocatalytic activities of the MCFs towards glucose. The non-enzymatic glucose sensor showed a wide linear range of 0.05–800 μM with a low detection limit of 0.01 μM (S/N = 3).