The electrochemical syntheses and characterizations of nickel nanoparticles and zinc-nickel nanoalloy on composite graphite substrate
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Date
2009
Authors
Mohammad Ali Tehrani, Ramin
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Abstract
The nickel (Ni) nanocrystals with an average size of 9.7 ± 2.3 nm were deposited
onto composite graphite electrode from a plating solution of 5.0 mM NiCl2.6H2O and
1.0 M NH4Cl using scan rate of 6500 mVs-1. The initial potential −1.5 V vs. Ag/AgCl,
final potential −0.5 V and applied time 120 s were used for the whole deposition
process. The variation of applied potentials and times has affected the characteristics of
deposited Ni nanocrystals. It was found that the structural formation of Ni nanocrystals
obtained were almost hexagonal close-packed (hcp).
The hcp nanocrystalline Ni modified composite graphite (hcp-nano Ni/CG)
electrode was investigated for the catalytic oxidation of methanol in alkaline medium
through the formation of NiOOH. A high anodic current was obtained at peak potential
of +570 mV vs. Ag/AgCl. Both the scan rate and the methanol concentration affected
the oxidation of methanol. The results showed that catalytic activity had increased with
decreasing Ni particle size. Thus, the modified electrode was the most efficient catalyst
in the oxidation of methanol.
The single phase gamma Zinc–Nickel alloy (γ–Zn3Ni) nanocrystal was deposited
on composite graphite electrode at a scan rate of 10,000 mVs-1. The average particles
size obtained was 11.8 ± 3.1 nm. The TEM analysis indicated that co-deposition applied
potential, i.e. nucleation overpotential, scan rate, and co-deposition time were critical on
crystals sizing and Ni content in the matrix. Cyclic voltammetry and analysis of XRD
have also indicated that single phase (γ–phase) alloy was, indeed, obtained at the scan
rate used. The results also revealed that 19.0 wt. % Ni nanoparticles were, uniformly,
dispersed in the phase compositions of the alloy coating.
The γ-Zn3Ni nanoalloy modified CG (nano-γ-Zn3Ni/CG) was employed for
detection of uric acid (UA) by voltammetry techniques. This non-enzymatic modified
electrode had an excellent response and specificity to the electrocatalytic oxidation of
UA in 0.2 M phosphate buffer (PB) (pH 7.0) at +280 mV vs. Ag/AgCl as compared to
an unmodified electrode at +360 mV. A limit of detection (S/N = 3) at 0.2 μM and
concentration linear range from 1 to 400 μM UA were obtained. The presence of
ascorbic acid (AA) did not interfere in the measurement. The nano-γ-Zn3Ni/CG was
used for the determination of UA in untreated human urine and serum samples with
satisfactory results.
Description
PhD
Keywords
Chemical science , Electrochemical syntheses , Nickel nanoparticles , Zinc-nickel nanoalloy