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Highlights in Chemical Science

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Electrochemical sensor for toxic compound

13 August 2010

Scientists develop a highly efficient and chemically stable hydrazine sensor using carbon modified zinc oxide nanorods. 

Hydrazine, N2H4 is highly neurotoxic and carcinogenic and can cause sever damage to the liver, lungs and kidneys. It is used extensively in industry, primarily as a foaming agent in the manufacture of polymer foams, as well as a precursor in the synthesis of catalysts, agrochemicals and pharmaceuticals. Therefore, for safety considerations, a reliable hydrazine sensor is highly desirable. 

Of the wide range of hydrazine detection techniques reported, electrochemical devices are the most promising since they are low cost, portable and generally offer fast response times and good sensitivity. Nanoparticle modified electrodes, such as zinc oxide nanostructures, are particularly advantageous because of their increased surface area, reduced resistance and a high signal-to-noise ratio. But, while highly sensitive the electrodes are insufficiently stable in various electrolytes for practical application. 

Carbon-modified zinc nanorod array

Carbon-modified zinc nanorod array has impoved sensing ability

Jinping Liu and colleagues at Huazong Normal University in China have overcome this problem by coating zinc oxide nanorods in a layer of carbon just a few nanometers thick using a simple immersion-calcination method. The high electrical conductivity of carbon improves the sensitivity of the sensor by facilitating the electron transport related to hydrazine oxidation. In addition, the chemical inertness of carbon improves the stability of the sensor by protecting the ZnO nanorod from corrosion by the electrolyte. 

'While the sensitivity and stability of sensor have been improved, our electrode design also avoids conventional electrode fabrication processes, which are typically laborious and expensive,' adds Liu. 

Gregory Wildgoose,  an expert in carbon nanotube surfaces for enhanced sensing and catalytic applications at the University of East Anglia, comments, 'the synergy between the amorphous graphitic coating and the underlying ZnO material that gives rise to improved electroanalytical performance when compared to vertically aligned carbon nanotube arrays is intriguing. There are clearly some interesting nano-scale interactions occurring in this system worthy of further investigation.'

The fabricated electrode may also find application in other devices such as batteries and photoelectrochemical cells. Liu says, 'the next step is to further optimise the synthetic techniques to allow very large-scale, uniform and reproducible growth of carbon coated nanorod arrays directly onto the current collector.' 

Jacob Bush 

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Link to journal article

C@ZnO nanorod array-based hydrazine electrochemical sensor with improved sensitivity and stability
Jinping Liu, Yuanyuan Li, Jian Jiang and Xintang Huang, Dalton Trans., 2010, 39, 8693
DOI: 10.1039/c0dt00258e

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