Shuo Huang

ZnO nanowire arrays on 3D hierachical graphene foam: biomarker detection of Parkinson's disease.

We report that vertically aligned ZnO nanowire arrays (ZnO NWAs) were fabricated on 3D graphene foam (GF) and used to selectively detect uric acid (UA), dopamine (DA), and ascorbic acid (AA) by a differential pulse voltammetry method. The optimized ZnO NWA/GF electrode provided a high surface area and high selectivity with a detection limit of 1 nM for UA and DA. The high selectivity in the oxidation potential was explained by the gap difference between the lowest unoccupied and highest occupied molecular orbitals of a biomolecule for a set of given electrodes. This method was further used to detect UA levels in the serum of patients with Parkinsons disease (PD). The UA level was 25% lower in PD patients than in healthy individuals. This finding strongly implies that UA can be used as a biomarker for PD.

Synthesis of ZnO nanowire arrays/3D graphene foam and application for determination of levodopa in the presence of uric acid

Three-dimensional (3D) graphene foam (GF) was prepared by chemical vapor deposition (CVD) using nickel foam as the template. ZnO nanowire arrays (ZnO NWAs) were vertically grown on the 3D GF by hydrothermal synthesis to prepare ZnO NWAs/GF. This hybrid combines the properties of ZnO NWAs and 3D GF, which has favorable electrocatalysis and outstanding electrical conductivity. The vertically aligned ZnO NWAs grown on the GF enlarged the electroactive surface area, which was investigated from the Fe(CN)63-4+ redox kinetic study. The ZnO NWAs/GF was used as an electrochemical electrode for the determination of Levodopa (LD) in the presence of uric acid (UA). The electrochemical responses of the ZnO NWAs/GF electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the sensitivity of the electrode for LD is 3.15μAμM-1 in the concentration range of 0.05-20μM and the measured detection limit of the electrode for LD is 50nM. The electrode also shows good selectivity, reproducibility and stability. The proposed electrode is succsefully used to determine LD in human plasma samples and it is potential for use in clinical research.

Highly sensitive and selective uric acid biosensor based on a three-dimensional graphene foam/indium tin oxide glass electrode

A three-dimensional (3D) continuous and interconnected network graphene foam (GF) was synthesized by chemical vapor deposition using nickel foam as a template. The morphologies of the GF were observed by scanning electron microscopy. X-ray diffraction and Raman spectroscopy were used to investigate the structure of GF. The graphene with few layers and defect free was closely coated on the backbone of the 3D nickel foam. After etching nickel, the GF was transferred onto indium tin oxide (ITO) glass, which acted as an electrode to detect uric acid using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The GF/ITO electrode showed a high sensitivity for the detection of uric acid: approximately 9.44xa0mAxa0mM(-1) in the range of 25xa0nM-0.1xa0μM and 1.85xa0mAxa0mM(-1) in the range of 0.1-60xa0μM. The limit of detection of GF/ITO electrode for uric acid is 3xa0nM. The GF/ITO electrode also showed a high selectivity for the detection of uric acid in the presence of ascorbic acid. This electrode will have a wide range of potential application prospects in electrochemical detection.

3-Dimensional hollow graphene balls for voltammetric sensing of levodopa in the presence of uric acid

AbstractThe development of novel nanomaterials brings new opportunity and challenge for high sensing detection of biomolecules. The authors describe the preparation of 3-dimentional hollow graphene balls (3D HGBs) using nickel nanoparticles (Ni-NPs) as the template. The Ni-NPs were synthesized by chemical reduction of nickel chloride and then graphene was coated onto their surface via carburization and carbonization. After etching Ni-NPs, 3D HGBs with few layers and a typical size of 100xa0nm were obtained. They were sprayed onto indium tin oxide glass to obtain a working electrode for electrochemical determination of levodopa in the presence of uric acid. Due to the unique hollow porous structure of the 3D HGBs, the electrode exhibits a sensitivity of 0.69xa0μA·μM−1·cm−2 and a 1 μM limit of detection. It is selective, reproducible and stable. It was applied to the determination of levodopa in spiked human plasma samples and it isxa0of potential use in clinical research.n Graphical abstractSchematic presentation of the preparation of 3-dimensional hollow graphene balls (HGBs) by using nickel nanoparticles as a template that can be removed by etching. The HGBs were sprayed onto indium tin oxide (ITO) glass to obtain a working electrode that hasxa0a sensitivity of 0.69 μA⋅μM−1·cm−2 and a 1 μM limit of detection for the determination of levodopa.

Determination of levodopa in the presence of uric acid using a ZnO nanoflower-modified indium tin oxide glass electrode

ZnO nanoflowers (ZnONFs) were synthesized by a simple hydrothermal method which is a convenient, environment-friendly, inexpensive process. The ZnONF suspension was sprayed onto the surface of ITO-coated glass (ZnONFs/ITO), which acts as the working electrode for the determination of levodopa by cyclic voltammetry and differential pulse voltammetry. The effect of reaction regents on the sizes of ZnONFs was investigated. The morphologies and structure of ZnONFs were characterized by scanning electron microscopy and X-ray diffraction analysis, respectively. The results show that the optimized length and diameter of ZnONFs are ~2.5xa0μm and 50xa0nm, respectively. The sensitivity and measured limit of detection of the ZnONFs/ITO electrode for levodopa are 0.10xa0μA/μM and 2.5xa0μM in the range of 2.5–40xa0μM, respectively. The electrode can accurately detect levodopa in the presence of uric acid. Meanwhile, the electrode shows good repeatability and stability.

Preparation of three-dimensional hollow graphene balls and simultaneous electrochemical determination of dopamine and uric acid

Nickel nanoparticles (Ni-NPs) were synthesized by the reduction reaction of NiCl2·6H2O, N2H4·H2O and NaOH, and then the graphene layers were coated on the surface of Ni-NPs by the carbide cladding method while triethylene glycol was used as carbon source. After etching Ni, the obtained 3D hollow graphene balls (HGBs) were sprayed onto the ITO coated glass to fabricate 3D HGBs/ITO electrode, which acted as a working electrode for determining dopamine and uric acid simultaneously. The results indicate that the multi-layered 3D HGBs maintain the original size of Ni-NPs (the diameter of ~u2009100xa0nm) and have few defects. The 3D HGBs/ITO electrode exhibits a high sensitivity of 1.16 and 0.94xa0μAxa0μM−u20091 for detecting dopamine and uric acid, respectively. Also, it shows a low measured limit of detection, excellent selectivity, reproducibility and stability. It is potential for use in clinical research.

Preparation of Fe 2 O 3 coated aluminum borate whiskers by a sol-gel method

Fe<inf>2</inf>O<inf>3</inf> coated aluminum borate whiskers were prepared by a sol-gel process. The preparation process and characterizations of Fe<inf>2</inf>O<inf>3</inf> coated aluminum borate whiskers were investigated. The results show that after Fe<inf>2</inf>O<inf>3</inf> xerogel coated aluminum borate whiskers are calcined at 400°C, Fe<inf>2</inf>O<inf>3</inf> can be uniformly coated on the surface of the whiskers. Moreover, Fe<inf>2</inf>O<inf>3</inf> does not take place phase transformation and no interfacial reaction takes place between Fe<inf>2</inf>O<inf>3</inf> and aluminum borate whiskers in the range of 400 and 800°C.