Glucose and calcium ion play key roles in human bodies. The needlelike NiCo2O4 nanostructures are in situ deposited on three-dimensional graphene foam (3DGF) by a facile hydrothermal procedure. The structure and morphology of the hierarchical NiCo2O4/3DGF are characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. With the self-standing NiCo2O4/3DGF as electrochemical electrode, it can realize the high-sensitivity detections for glucose and calcium ion. The limit of detection can reach 0.38 and 4.45 μM, respectively. In addition, the electrochemical electrode presents excellent selectivity for glucose and calcium ion. This study demonstrates that NiCo2O4/3DGF is a unique and promising material for practical application in both glucose and calcium ion sensing.

Herein, ZnO nanorods with an average diameter of 50 nm were uniformly anchored on the surface of carbon cloth directly by a simple hydrothermal method. The nanorods growing in situ along the specific direction of (002) have single-crystalline features and a columnar structure. On the basis of the ZnO nanorod/carbon cloth composite, free-standing electrodes were fabricated for the simultaneous determination of dihydroxybenzene isomers. The ZnO nanorod/carbon cloth electrodes exhibited excellent electrochemical stability, high sensitivity, and high selectivity. The linear ranges of concentration for hydroquinone, catechol, and resorcinol were 2-30, 2-45, and 2-385 μM, respectively, and the corresponding limits of detection (S/N = 3) were 0.57, 0.81, and 7.2 μM. The outstanding sensing properties of ZnO/carbon cloth electrodes have a great promise for the development of free-standing biosensors and other electrochemical devices.

However, the electrochemical oxidation of hydrazine at glassy carbon electrode or bare metal is restricted by the high overpotential and sluggish kinetics, which generates a poor detection performance. [ 11 ] Although, lots of materials (such as zinc oxide nanonails, [ 12 ] ZnO nanorods, [ 13 ] polypyrrole nanoplates, [ 14 ] etc.) have been used in electrochemical sensors, exploring an effi cient and sensitive electrode material is of vital importance.In the past few decades, carbon-based composites, such as epoxy/carbon fi ber, [ 15 ] MnO 2 /graphene, [ 16 ] graphene oxide (GO)/ Fe, [ 17 ] MHTiO 2 @C-Au, [ 18 ] and Ni(OH) 2 /3D graphene, [ 19 ] have attracted tremendous interests owning to their unique physical and chemical properties. Specially, carbon cloth (CC) composites, consisting of reinforcing carbon fi bers and functional nanomaterials, are widely used in microwave absorption, [ 20 ] catalysis, [ 21,22 ] and supercapacitors, [ 23,24 ] due to its excellent mechanical strength, good corrosion resistance, high electrical conductivity, excellent fl exibility, and low-cost. However, to our knowledge, the application of carbon cloth in preparing freestanding electrode materials for electrochemical detection devices for hydrazine detection has never been reported.In this work, porous Co 3 O 4 nanosheets, vertically deposited onto the surface of graphene oxide modifi ed carbon cloth, were synthesized through a facile diffusion method at room temperature without the existence of any auxiliary reagents following a thermal annealing process (See Figure 1 ). The GO nanosheets on the surface of CC make the CC present hydrophilic and provide amounts of reactive oxygen functional groups. [ 25 ] Furthermore, the GO reduced at high temperature can greatly enhance the conductivity of CC. Compared with the previously reported method of dealing with nitric acid, [ 26 ] modifi ed CC with GO was simple and environmental friendliness. More importantly, the constructed Co 3 O 4 /reduced graphene oxide (rGO)/CC electrode demonstrates high sensitivity, low limit of detection (LOD), and excellent selectivity for hydrazine detection. Results and Discussion Structure and Morphology

Ultra-sensitive and highly selective detection of glucose is essential for the clinical diagnosis of diabetes. In this paper, an ultra-sensitive glucose sensor was successfully fabricated based on cobalt oxide (Co3O4) nanosheets directly grown on nickel foam through a simple hydrothermal method. Characterizations indicated that the Co3O4 nanosheets are completely and uniformly wrapped onto the surface of nickel foam to form a three-dimensional heterostructure. The resulting self-standing electrochemical electrode presents a high performance for the non-enzymatic detection of glucose, including short response time (<10 s), ultra-sensitivity (12.97 mA mM(-1) cm(-2)), excellent selectivity and low detection limit (0.058 μM, S/N = 3). These results indicate that Co3O4 nanosheets wrapped onto nickel foam are a low-cost, practical, and high performance electrochemical electrode for bio sensing.