A surprisingly wide range of uses
However, for many sensor applications it is important that the response time be as short as possible, something which is hardly possible with compact plasma dye layers. It is, on the other hand, possible with layers which have very a porous structure, resembling the nap of a nanometer-scale carpet. Scientists hope to derive further benefits from such layers because they increase the area onto which the gas molecules to be detected can adsorb, and also shorten the diffusion distances, allowing the sensor to respond faster. Physicist Ana Borras thereupon developed a new vacuum deposition process for synthesizing organic nanowires.
In the meantime the Empa researchers made progress, learning how to manufacture nanowires with very widely varying characteristics by appropriately selecting the starting molecule and the experimental conditions. Nanowires of metallo-phthalocyanine molecules have diameters of a mere 10 to 50 nanometers and a length of up to 100 microns. What is unusual and unexpected about the new method is that by exactly controlling the substrate temperature, molecule flow and substrate treatment, the organic nanowires develop a previously unattained, perfectly monocrystalline structure.
Immediately after the first studies were made with the electron microscope it was clear to Groening that the new process could not only provide nanowires for the gas sensors but also make it possible to create complex "nanowire electric circuits" for electronic and optoelectronic applications such as solar cells, transistors and diodes. This is because the different types of nanowires can be combined as required to form networks with widely varying properties, as Groening and coworkers report in the scientific journal Advanced Materials and elsewhere.
|Contact: Sabine Voser|
Swiss Federal Laboratories for Materials Testing and Research (EMPA)