Sol-gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uric acid and paracetamol in urine.

Institute of Chemistry, State University of São Paulo, PO Box 780, 13560-970 São Carlos, SP, Brazil. Electronic address: .
Talanta (Impact Factor: 3.5). 11/2013; 116:726-35. DOI: 10.1016/j.talanta.2013.07.044
Source: PubMed

ABSTRACT This work describes the preparation, characterization and application of a hybrid material composed of disordered mesoporous silica (SiO2) modified with multiwalled carbon nanotubes (MWCNTs), obtained by the sol-gel process using HF as the catalyst. This hybrid material was characterized by N2 adsorption-desorption isotherms, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission microscopy (HR-TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). This new hybrid material was used for the construction of a thin film on a glassy carbon electrode. The modified electrode using this material was designated SiO2/MWCNT/GCE. The electrocatalytic properties of the electrode toward dopamine, uric acid and paracetamol oxidation were studied by differential pulse voltammetry. Well-defined and separated oxidation peaks were observed in phosphate buffer solution at pH 7.0, in contrast with the ill-defined peaks observed with unmodified glassy carbon electrodes. The electrode had high sensitivity for the determination of dopamine, uric acid and paracetamol, with the limits of detection obtained using statistical methods, at 0.014, 0.068 and 0.098µmolL(-1), respectively. The electrode presented some important advantages, including enhanced physical rigidity, surface renewability by polishing and high sensitivity, allowing the simultaneous determination of these three analytes in a human urine sample.

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    ABSTRACT: This paper describes the synthesis, characterization and application of amorphous nickel (II) hydroxide particles, a-Ni(OH) 2 , onto a hybrid material composed of silica and graphene oxide, SiO 2 /GO. The sol-gel process using HF as the catalyst was used to obtain this organic-inorganic matrix. The Ni(OH) 2 were prepared directly on the surface of the matrix using nickel (II) acetate and N,N-dimethylformamide (DMF) as a solvent. The SiO 2 /GO/Ni(OH) 2 material was characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. A glassy carbon electrode modified with the SiO 2 /GO/Ni(OH) 2 material was used in the development of a sensitive electrochemical sensor for the determination of vitamin D 3 by pulse differential voltammetry. A well-defined electro-oxidation peak of vitamin D 3 was observed in sodium hydroxide at pH 13. The results indicated that the resultant SiO 2 /GO/Ni(OH) 2 modified electrode is highly selective and very sensitive with a limit of detection, in pure laboratory solutions of 3.26 Â 10 À9 mol dm À3 ; therefore, it can be used to detect vitamin D 3 in real samples.


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May 22, 2014