The advanced synthesis of high quality nanowires and nanotubes in large quantities is the basis of our effort of finding viable applications. Among them, carbon nanotubes and TiO2 nanowires are used the most. Below a few of these applications are highlighted.
We have developed a novel morphology for solid-state dye-sensitized solar cells based on the simple and straightforward self-assembly of nanorods into a 3D fibrous network of fused single-crystalline anatase nanowires (left panel). This architecture offers a high roughness factor, significant light scattering, and up to several orders of magnitude faster electron transport to reach a near-record-breaking conversion efficiency of 4.9%.(the fabrication and the test bench for the photovoltaic cell is shown.)
Methylene blue (MB) molecules deposited on titanate nanowire networks dimerize upon exposure to humidity which changes the optical absorption. Based on the observed humidity dependent on metachromasy, we fabricated a humidity sensor using optical fiber technology which is adapted for medical, industrial or environmental applications. The sensor operates with excellent linearity over the relative humidity (RH) levels ranging from 8 to 98%. The response and recovery time can be reduced to 0.5s while the device exhibit excellent reproducibility with low hysteresis. The effect has been observed for other dyes as well.
Fuel cell application
In the quest of renewable sources of energy, fuel cells represent a clean technology to convert chemical energy into electricity. We focus on the design of new materials suitable for proton exchange membrane fuel cell (PEMFC) applications. A the bench-mark for PEMFC technology is a the commercially available ion-exchange resin, Nafion™. The highly proton conducting channels are randomly oriented in the polymer. Our strategy is to order them by the interaction with an aligned CNT carpet. The SEM image shows this composite membrane (nafion+CNTs). The proton conduction is highly improved.
SU8 is a very popular epoxy resin largely used in microfabrications since by UV polymerization one can form well defined, high aspect ratio structures. The disadvantage is that it is an electrical insulator, a poor thermal conductor and it is brittle. All these properties can be improved by homogeneously dispersing CNTs. The SEM image shows a good homogeneity of the composite (left), which gives the pattern a well defined structure (middle). Furthermore, the composite is elastic, as demonstrated by its bending deposited on a polymer film (right).