Inexpensive, reliable sensors are a crucial part in most manufacturing processes. The current demand for increasingly more integrated consumer products has created a strong need for ultra low cost materials with exceptional sensing and mechanical or thermal stability.
Reducing flame synthesis gave access to the large scale production of metallic copper nanoparticles up to about 20 g/h. The transmission electron micrograph right shows that the as-prepared copper nanoparticles had an average size of 10-20 nm. The copper nanoparticles were covered by thin carbon layers resulting in a nanocomposite with a remarkable air stability enabling their use for further processing. These carbon coated copper nanoparticles also exhibited a high temperature resistance up to 200°C. Pressing of the as-prepared nanomaterial to pills and measuring their electrical resistivity revealed novel electrical properties, which could be further applied for sensing applications.
Water-based dispersions of carbon coated copper nanoparticles could be applied to produce C/Cu-polymer nanocomposite films. Exposure to water vapor or organic solvents like ethanol or acetone resulted in a highly sensitive and reversible coloration of the film. This nanomaterial is a promising low-cost alternative for electronic circuit-free humidity sensing.
The carbon coated copper nanoparticles exhibit a highly pressure and temperature dependent electrical resistivity. The pronounced negative temperature conductivity (NTC) behavior of the nanocomposite has similar or greater sensitivity than commercially applied metal oxide based spinels and perovskites.
E. K. Athanassiou, R. N. Grass, W. J. Stark, Nanotechnology 2006, 17, 1668
N. A. Luechinger, S. Loher, E. K. Athanassiou, R. N. Grass, W. J. Stark, Langmuir 2007, 23, 3473.
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