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s To achieve uninterrupted detection of position contacting with robot environment, this paper proposes a new type of tactile sensor. The sensor was developed with the principle of distributed planar electric field based on the uniqueness of steady electric field. The coordinate of contact position can be obtained from the potential value distributed on the planar electric field. The tactile sensor has a non-array structure, and consists of two conductive layers, an insulating layer and two viscoelastic layers. The feasibility was verified by the finite element simulation with COMSOL software and the sensor sample fabrication. The robot application experiments on an industrial robot arm with six degrees of freedom shows that the sensor has good accuracy of position detection and high space resolution. The sensor is thin and soft, easy to make and use, and has only 4 wires. Signal processing is also simple. It is capable of covering large areas of robot arms, and provides safety solutions for most robots.

A novel ionic liquid, 4-hydroxy-1-methyl-[1-(3-pyrrolyl-propyl)]-piperidinium bromide, was synthesized and characterized. Carboxylic-functionalized graphene oxide nanosheets were modified with this ionic liquid to fabricate a nanocomposite which was denoted as GrO-COO-IL. Characterizations of FTIR, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy confirmed the successful conjunction of these two components. GrO-COO-IL nanocomposites were homogeneously dispersed with utralpure water, and were then coated onto glassy carbon electrode surface. Followed by cyclic voltammetric scanning, a graphene oxide-polymerized ionic liquid film modified electrode (GrO-COO-Poly-IL/GCE) was prepared, and was studied with electrochemical impedance spectroscopy and scanning electron microscope. It was found that both honokiol and magnolol exhibit sensitive voltammetric response at the GrO-COO-Poly-IL/GCE. Simultaneous assay of honokiol and magnolol was realized with differential pulse voltametry. In the presence of magnolol, the oxidation peak current was linearly related to honokiol concentration in the range of 1.0 × 10−8 ∼ 1.0 × 10−5 mol L−1 with a detection limit of 1.53 × 10−9 mol L−1 (S/N = 3). Meanwhile, in the presence of honokiol, a linear relationship between the oxidation peak current and magnolol concentration was found from 7.0 × 10−8 to 1.0 × 10−5 mol L−1. The detection limit is calculated to be 8.27 × 10 −9 mol L−1 (S/N = 3). In addition, GrO-COO-Poly-IL/GCE was successfully used for determination of honokiol in the traditional Chinese medicine, and was demonstrated to be an effective and sensitive method.

Mesoporous NiCo2O4 nanoneedles were directly grown on three dimensional (3D) graphene-nickel foam which was prepared by chemical vapor deposition, labeled as NCO/GNF. The structure and morphology of NCO/GNF were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, element mapping and Raman spectroscopy. The NCO/GNF was employed as electrodes for supercapacitor and methanol electro-oxidation. When used for supercapacitor, the NiCo2O4 nanoneedles exhibit hi exhibit high specific capacitance (1588 F g−1 at 1 A g−1), high power density and energy density (33.88 Wh kg−1 at 5 kW kg−1) as well as long cycling stability. In methanol electro-oxidation, the NiCo2O4 nanoneedles deliver high electro-oxidation activity (93.3 A g−1 at 0.65 V) and electro-oxidation stability. The good electrochemical performance of NiCo2O4 nanoneedles is attributed to the 3D structure with large specific area, high conductivity and fast ions/electrons transport.

NiCo 2 O 4 nanowires/nitrogen-doped graphene (NCO/NG) composite materials were synthesized by hydrothermal treatment in a water–glycerol mixed solvent and subsequent thermal transformation. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The electrochemical performance of the composites was evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrum techniques. NiCo 2 O 4 nanowires are densely coated by nitrogen-doped graphene and the composite displays good electrochemical performance. The maximum specific capacitance of NCO/NG is 1273.13 F g −1 at 0.5 A g −1 in 6 M KOH aqueous solution, and it exhibits good capacity retention without noticeable degradation after 3000 cycles at 4 A g −1 .

Graphene nanosheets (GS) were easily prepared via one-step liquid exfoliation of graphite powder in N-methyl-2-pyrrolidone, and then hybridized with porous Fe 2 O 3 microspheres, as confirmed by the measurements of transmission electron microscopy and X-ray diffraction. Scanning electron microscopy tests indicated that the surface roughness of GS-Fe 2 O 3 hybrid was larger, and three-dimensional structure was more abundant. Compared with GS and Fe 2 O 3 microspheres, the resulting GS-Fe 2 O 3 hybrid remarkably increased the oxidation signals of bisphenol A (BPA). Moreover, the oxidation signals of BPA on GS-Fe 2 O 3 hybrid surface was further enhanced greatly after addition of hexadecyltrimethylammonium bromide (CTAB). Based on the synergetic signal amplification of GS-Fe 2 O 3 hybrid and CTAB, a novel electroanalytical method with high sensitivity was developed for BPA, and the limit of detection was as low as 2.5 nM.

It is quite important to develop sensitive and simple analytical methods for the detection of toxic heavy metal ions, such as Cd2+ and Pb2+. Herein, liquid phase-exfoliated graphene nanosheets were easily prepared through a one-step exfoliation of graphite powder in N-methyl-2-pyrrolidone. The obtained graphene suspension was directly used to modify the surface of a glassy carbon electrode (GCE), constructing a novel and highly-sensitive electrochemical sensor for Cd2+ and Pb2+. Compared with an unmodified GCE, and a reduced graphene oxide-modified GCE, the resulting liquid phase-exfoliated graphene-modified GCE significantly increased the response signals towards Cd2+ and Pb2+, showing remarkable signal amplification effects. The use of this defect-abundant, few-layered graphene sample, with small lateral flake sizes, has led to the beneficial responses observed. The influences of the supporting electrolyte, volume of the graphene suspension, deposition potential and accumulation time were examined. As a result, a sensitive, rapid and convenient electrochemical method was developed for the simultaneous detection of Cd2+ and Pb2+. The detection limits were estimated to be 1.08 μg L−1 and 1.82 μg L−1 for Cd2+ and Pb2+. This new sensor was used in water sample analysis, and the results were consistent with the values obtained by inductively coupled plasma-atomic emission spectroscopy.

Graphene nanosheets (GNSs) were synthesized by reducing exfoliated graphite oxides. Their structure, surface morphology and lithium storage mechanism were characterized and investigated systematically using X-ray diffraction, atomic force microscopy, scanning electron microscopy, charge-discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the GNSs, which were obtained via chemical synthesis, were primarily less than 10 graphene layers. The GNS electrodes, which were fabricated from the reduced GNSs, exhibited an enhanced reversible lithium storage capacity and good cyclic stability when serving as anodes in lithium-ion batteries. Also, the first-cycle irreversible capacities of the system were relatively high, because of the formation of a solid electrolyte interphase film on the surface of the GNS electrode and the spontaneous stacking of GNSs during the first lithiation. The electrochemical impedance spectroscopy results suggest that the solid electrolyte interphase film on the GNS electrode during first lithiation were primarily formed at potentials between 0.95 and 0.7 V. Also, the symmetry factor of the charge transfer was measured to be 0.446.