Elsevier

Analytica Chimica Acta

Volume 526, Issue 1, 15 November 2004, Pages 13-17
Analytica Chimica Acta

Fabrication and characterization of copper nanoparticle thin-films and the electrocatalytic behavior

https://doi.org/10.1016/j.aca.2004.08.060Get rights and content

Abstract

Copper nanoparticles, stabilized by cysteine, have been formed thin-films on indium tin oxide (ITO) electrodes with (3-mercaptopropyl) trimethoxysilane (MPTMS). Scanning electron micrograph (SEM) demonstrates that the films are uniform and the copper nanoparticles are homogeneously distributed on the ITO electrode surface. Electrochemical experiments reveal that the obtained copper nanoparticles modified electrodes show improved electron-transfer characteristics and exhibit high electrocatalytic activity to the reduction of nitrite and nitric oxide, which can be utilized as an efficient electrochemical sensor.

Introduction

Nanostuctured particles have attracted extensive scientific and industrial interest due to their unique electronic, optical, and catalytic properties [1], [2], [3], [4], [5]. Gold and silver nanoparticles are the most widely studied particles and these particles exhibit useful applications in catalysis and biosensing [3], [4], [5]. Since 1990s, copper nanoparticles have attracted much attention of scientists. Many techniques such as chemical reduction [6], radiolytic reduction [7], reduction of copper ions with supercritical fluids [8], and laser irradiation of CuO powders [9], [10], are developed to synthesize copper nanoparticles. The primary application of copper nanoparticles is in catalysis, just like the bulk copper metal [11]. On the other hand, copper nanoparticles offer higher catalytic efficiency per gram than the bulk one due to their large surface-to-volume ratios [12].

Nitrite ion can be used as an important precursor in the formation of N-nitrosamines, many of which have been shown to be carcinogens [13], [14]. In addition, the occurrence of nitrite salts in the environment and their use for food preservation is widespread [15]. Nitric oxide (NO) is a neuronal signal in the central nervous system. It can be synthesized by mammalian cells and can be act as a physiological messenger and cytotoxic agent [16]. Therefore, it is important to develop sensitive and accurate methods for the determination of nitrite and NO. Numerous methods have been proposed for the determination of the two species [17], [18]. Among them, electrochemical methods offer useful alternatives since such analysis is faster, cheaper and safer. However, the redox reaction of nitrite at bare electrode involves a large overpotential. One of the most promising methods is to modify the electrode surface with suitable catalyst, which can not only improve the redox response of nitrite and NO, but also provide a means of extending the dynamic range in analytical determinations [15], [19].

With the hope of developing more efficient and robust electrocatalyst to improve the redox response of nitrite and NO, we have started research on metal nanoparticles (NPs). NPs offer higher catalytic efficiency per gram than larger materials because of their large surface-to-volume ratios [12]. Furthermore, the integration of metal NPs into films is particularly important for various applications such as in biological sensing and in the preparation of optoelectronic nanodevice [3], [20]. In this report, we described a simple method for the fabrication of copper NPs thin-films on ITO substrate. The resultant modified electrodes exhibited excellent stability and high catalytic activity towards the reduction of nitrite and NO. Compared with other catalyst [15], [21], the copper NPs were easily available, and the obtained modified electrodes showed wide linear concentration range for the determination of nitrite.

Section snippets

Experimental

(3-mercaptopropyl) trimethoxysilane (MPTMS) was obtained from Across.

Copper nanoparticles stabilized by cysteine were prepared according to the modified Brust method [22]. In a typical reaction, 0.01 M CuSO4 was dissolved in 5 ml water, to which was added 4 ml solution of 0.01 M NaOH containing 0.01 M cysteine under vigorous stirring, then 1 ml freshly prepared solution with 0.0233 g NaBH4 was added into the above solution immediately. A change of color from dark brown to wine-red was observed. The

Results and discussion

XPS measurement is performed on the copper NPs/MPTMS modified ITO substrate to know the oxidation state of the copper NPs. Fig. 1 displays the XPS spectra of Cu2p3/2 and Cu2p1/2, which appear at 932.3 and 952.1 eV, respectively, indicating that the Cu particles in the film are Cu(0) [23].

The morphology of copper NPs/MPTMS modified ITO substrate is evaluated by SEM. A piece of ITO coated with copper NPs was fixed onto the SEM mounting stage with two-side adhesives. Fig. 2B shows the SEM image of

Conclusions

The preparation and characterization of copper NPs thin-films on ITO electrodes are demonstrated in this work. SEM is used to investigate the surface morphology of the NPs modified electrode. The obtained modified electrodes are stable and show electrocatalytic properties for the reduction of nitrite and NO, which may find its promising application as an electrochemical sensor for the detection of NO. Furthermore, the method for the fabrication of the copper NPs thin-films is simple and can be

Acknowledgements

This work is supported by the National Natural Science Foundation of China (no. 20175023 and no. 20375034) and Jiangsu Province Natural Science Foundation (no. BK2002045).

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