Amperometric glucose sensor based on nickel nanoparticle / chitosan and multiwall carbon nanotube on modified graphite electrode

A novel Ni (Nickel)/CS(chitosan)/CNT(carbon nanotube) network nanocomposite was constructed on graphite electrode for glucose detection . Firstly, multi-walled carbon nanotubes were purified and characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM). The modified electrode with the Ni/CS/CNTs showed excellent electrocatalytical response to the oxidation, which was studied by cyclic voltammetry (CV). The synthesized biosensor exhibited rapid response, low detection limit, broad linear range, good reproducibility and stability.


Introduction:
Many studies about providing suitable coating on the electrodes have been investigated.
Electron transfer chemical and electrocatalysis properties is very important for them.Exact determination of glucose concentration is necessary for treatment of diabet and food industry [1].
Chitosan include excellent biocompatibility, biodegradability, nontoxicity, high mechanical strength, good adhesion and cheapness properties, therefore it has been used as an immobilization matrix.Although it has poor electrical conductivity, but it usually has been combined with carbon nanotubes, redox mediator and metal nanoparticles.Carbon nanotubes have been used in various sensors due to unique properties such as high electronical and mechanical stability.
Modified electrodes by various metal (gold, platinum) metal oxide (tungsten oxide, nickel oxide), metal decorated carbon nanotubes and metallic complexes that uniformly dispersed in insoluble organic film (cabolt phethalocyamine), have been recognized [2].
Nickel hydroxide severely adsorbs some organic substance, such as chitosan, and has high electrocatalytical properties.Therefore it has been used for preparation of modified electrodes [3].
In this work, a film of Ni/CS/CNTs network was prepared for oxidation of glucose.The electrochemical properties of this biosensor were investigated.This biosensor exhibited rapid response, low detection limit and broad linear range [2][3][4][5].

Materials:
In this study we used chitosan were purchased from Sigma-Aldrich.Multi walled Carbon Nanotubes (MWCNTs) were purchased from Arkema.Acetic acid, nickel hydroxide, sodium hydroxide, d-glucose were obtained from Merck company.All solutions were prepared with doubly distilled water.

Apparatus:
A three-electrode system including Ni/CS/CNTs electrode as the working electrode, a Pt wire as the counter electrode and an Ag/AgCl as the reference electrode was used in electrochemical measurement .The microstructure was observed by using a scanning electron microscope (SEM) (TESCAN, VEGA, Czech Republic.Electrochemical characterizations were carried out by an electrochemical workstation (SAMA, 500 electro analyzer, Iran).FTIR spectra were recorded on a shimadzu S8400 Fourier transform infrared spectrometer.

Method:
0.1g chitosan was dissolved in 10 ml acetic acid (1%) to obtain soluble chitosan (1%).The chitosan solution was left at room temperature.The resulting was filtered carefully because of the dust.MWCNTs were functionalized with HNO3.After that, functionalized MWCNTs were dispersed in 5 ml of the above solution and were solubilized by sonication for 20 min.The nickel hydroxide powder was mixed and was stirred uniformly for 24 h until complete dissolution.Finally, the resulting solution was ready for cover on the electrode.The biosensors prepared, was stored at 4 °   A novel Ni/CS/CNTs was prepared and an electrode made of this film was used in the electrocatalytic glucose oxidation.This biosensor exhibited better electrocatalytic properties such as increased electroactive surface area, high sensitivity, low detection limit, good reproducibility and stability.

Fig. 1
Fig. 1 shows the FTIR spectra of the MWCNT-COOH (a) and CS-MWCNT (b).The sharp absorbance at 1712.67 cm -1 shows C=O stretching of -COOH in the spectra of MWCNT-COOH.The strong absorbance at 1634.45 cm -1 indicates the -COOH of MWCNT were reacted with the -NH2 of CS and turned into -NHCOin the spectra of CS-MWCNT [6].

Fig 4 .
Fig 4.peak currents in Ni/CS/CNTs electrode depend on concentration of glucose