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Nanorods assembled 3D microspheres of TiO2/MnO2 were prepared via a simple one-pot hydrothermal approach. The resultant composite material exhibited remarkable electrocatalytic activity for hydrogen peroxide (H2O2) in comparison to each single component. The electrochemical sensor constructed with TiO2/MnO2 exhibited a linear relationship within the range 0.0001–5.6 mmol·L−1 for H2O2. The limit of detection (LOD) and sensitivity for H2O2 were 0.03 µmol·L−1 (S/N = 3) and 316.6 µA (mmol·L−1)−1 cm−2. Moreover, this sensor can be employed to detect trace amount of H2O2 in serum and urine samples successfully, supporting an insight and strategy for a more sensitive electrochemical sensor. [ABSTRACT FROM AUTHOR]

A hollow urchin-like α-MnO2 material has been synthesized by a hydrothermal method starting from MnSO4·H2O and (NH4)2S2O8, and by using silver(I) as the catalyst. It has a hollow morphology with diameters of 5–6 μm and consists of densely aligned nanowires, with a 30–40 nm width and a 1.5 μm length. The diameter of the cavities and the thickness of the shell are about 1.2 μm and 300 nm, respectively. The material was placed on a glassy carbon electrode (GCE), and electrochemical experiments showed the respective sensor to possess good stability and reproducibility. The modified GCE displays response to both hydrogen peroxide (H2O2) and dopamine (DA) at working potentials of −0.40 V and +0.4 V, respectively (both versus SCE). H2O2 can be detected with an 80 nM detection limit, and DA with a 12 nM detection limit (at S/N = 3). Graphical abstract Schematic presentation of synthesis of a hollow urchin-like α-MnO2, which taking MnSO4.H2O and (NH4)2S2O8 as raw materials and was further used to construct an electrocatalytic sensor for hydrogen peroxide and dopamine with low detection limit, desirable selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Co3O4/carbon hybrid hollow nanospheres (hs-Co3O4/C) with an empty cavity and a thin shell, were synthesized starting from the pectin and cobalt acetate via cross-linking deposition at room temperature and post-calcination. The hierarchical structure is constructed from the interconnected nanoparticles in the residual carbon matrix, and the carbon content can be adjusted by changing the calcination temperature. The gas sensor based on hs-Co3O4/C calcined at 300 °C in air shows high response towards 50 ppm of H2S (S = 95.5) and good selectivity at a low working temperature (92 °C). The detection limit is as low as 0.1 ppm. The non-enzymatic glassy carbon electrode based sensor constructed from the same material exhibits excellent electrocatalytic activity for H2O2 with the sensitivity of 405.8 μA∙mM∙cm−2 at 0.3 V (vs. SCE) in alkaline solution. The chronoamperometric response time is < 3 s and the detection limit (at S/N = 3) is 0.30 μM. The good sensing performances are attributed to the synergetic effect of unique hollow nanostructure and appropriate amount of carbon in the hybrid material. The porous nanostructure can increase the mass transfer efficiency, and the cross-linked nanoparticles with good crystallinity also improve the conductivity of materials. The presence of carbon enhances the charge transfer ability and increases the specific surface, thereby improving the sensor performance.Schematic illustration of the formation of hollow Co3O4 nanospheres composited with pectin-derived carbon. The material displays excellent selectivity for H2S gas and in non-enzymatic detection of dissolved H2O2. [ABSTRACT FROM AUTHOR]