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Nickel foam (NF) was used as sacrificial template to synthesize graphene foam (GF) by chemical vapor deposition (CVD). ZnO NSAs were grown on the GF by hydrothermal synthesis to fabricate ZnO NSA/GF, which was used to detect dopamine in the presence of ascorbic acid and uric acid. The inter-connected ZnO NSAs with the sheet size of ~ 10 μm and thickness of ~ 500 nm uniformly distributed on the GF. The ZnO NSA/GF shows a sensitivity of 0.95 μA μM−1 in the concentration range of 0–80 μM and a measured limit of detection of 1 μM for determination of dopamine. Furthermore, the prepared electrode displays a reliable anti-interference to ascorbic acid and uric acid. It also shows an excellent reproducibility and long-time stability. The ZnO NSA/GF electrode was applied in human urine samples and exhibited satisfied recoveries. [ABSTRACT FROM AUTHOR]

Carbon nanofiber (CNF) was prepared by electrospinning using polypropylene and nickel was coated on the CNF by electroless plating. Then, graphene (Gr) was synthesized on the surface of nickel by chemical vapor deposition. After etching nickel, the Gr/CNF was obtained eventually and then used as a working electrode for the determination of levodopa in the presence of uric acid by cyclic voltammetry and differential pulse voltammetry. The morphology and structure were investigated by scanning electron microscopy and Raman spectroscopy, respectively. The results indicate that the electrode exhibits a high sensitivity of 0.26 μA·μM−1 and a low measured limit of detection of 1 μM for levodopa in the range of 1–60 μM. The electrode shows excellent selectivity, reproducibility, and stability. It was also applied to determine levodopa in the spiked human urine samples. [ABSTRACT FROM AUTHOR]

Nickel powders were prepared by the liquid phase reduction method. Using the nickel powders as the template, three-dimensional graphene foam (3D GF) was prepared via chemical vapor deposition (CVD) at high temperature, followed by acid etching. It was transferred onto the indium tin oxide (ITO) glass (3D GF/ITO) and acted as the electrode for the simultaneous determination of dopamine (DA) and uric acid (UA). The 3D GF/ITO electrode shows a high sensitivity and excellent selectivity for the detection of DA and UA. The measured detection limit for DA and UA is 0.1 μM, respectively. The 3D GF/ITO was employed for the measurement of human urine, exhibiting satisfactory results. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected network graphene foam (GF) was synthesized by chemical vapor deposition. The GF was transferred onto indium tin oxide glass, acting as an electrode for the selective determination of L-dopa in the presence of ascorbic and uric acid. Using differential pulse voltammetry (DPV) method, the oxidation peak current is well linear with L-dopa concentration in the range of 0.05-1 μM with a sensitivity of 2.64 μA μM−1 and in the range of 1-40 μM with a sensitivity of 1.82 μA μM−1. The detection limit of this electrode for L-dopa is about 20 nM. The proposed electrode can also effectively avoid the interference of ascorbic acid and uric acid, making the proposed sensor suitable for the accurate determination of L-dopa in human urine fluids. This electrode will have a wide range of potential application prospect in electrochemical detection. [ABSTRACT FROM AUTHOR]

An electrochemical sensor is described for simultaneous voltammetric determination of dopamine (DA) and uric acid (UA). It is based on the use of a nanomaterial composed of gold nanoparticles and 3-dimensional graphene (Au NP@3D GR). The 3D GR was prepared by chemical vapor deposition using nickel nanoparticles as the template at a temperature of around 900 °C. The surface of 3D GR contains oxygen-functional groups after treatment with acid. Carboxylated Au NP were self-assembled and anchored onto the surface of 3D GR. The nanomaterial was placed on a ITO electrode. The few-layer graphene on the ITO glass has a porous structure and the distribution of Au NP is uniform. The electrode shows a high sensitivity and a low detection limit for DA and UA. Figures of merit include detection limits of 0.1 M for DA and of 0.1 μM for UA, and well separated peaks at potentials of 0.18 and 0.30 V (vs. Ag/AgCl), respectively, at pH 7.0. The electrode has good repeatability and stability. [ABSTRACT FROM AUTHOR]