Organic light sources become steadily more important in the growing field of optoelectronics. Especially in the area of nanoscale optics, much research is devoted to one-dimensional nanostructures that are utilized as building units for nanoelectronics and photonics. Recently, Francesca Di Benedetto and colleagues from the Italian Institute of Technology, Lecce, and the Scuola Superiore ISUFI, Lecce, have succeeded in an approach to easily produce organic nanofibres of conjugated aromatic polymers by means of electrostatic spinning and enhance their optical properties via nanoimprinting, [Nature Nanotechnology (2008) 3, 614.]
“Among other nano-technologies, electrospinning and nanoimprinting are particularly interesting in the respect of mass production,” says Dario Pisignano, the corresponding author. “Both of them are able to process large quantities of materials in short times. Electrospinning may process large volumes of polymer solution in a continuous way. Nanoimprinting as patterning technology can work on relatively large areas, and continuous processing chains. Combining high-throughput nanofabrication approaches is a unique way to make commercially interesting produced nanomaterials.”
The method of electrostatic spinning can manufacture large quantities of polymers into fibres of sub-micrometer diameter through plastic stretching (typical diameters are about 400 nm). In this process, the more or less parallel orientation of the organic molecules within the fibre is promoted by the applied external field. Once the fibres are spun, they are nano-patterned by the technique of Room-Temperature
NanoImprint Lithography (RT-NIL). This high-throughput method employs a rigid nanostructured silicon template, which is applied with high pressure (about 260 MPa) onto the fibres, without the drawbacks of hot embossing that would deteriorate the optoelectronic properties by the incorporation of oxygen into the fibres.
Furthermore, Di Benedetto and her group assessed the optical properties of the nano-patterned fibres. They found clear evidence for an enhancement of the light output from the fibres which had undergone RT-NIL compared to those which hadn't. “In addition, we found that they act as cylindrical waveguides in the visible and near infrared range and, more important, patterning is a powerful method to tune and tailor the emission wavelength of the fibers,” explains Pisignano. He sees these materials as promising candidates for nanoscale LEDs, sensors, catalysts and lasers. “Our very first next step will concern the realization of nano-patterned lasers. We are also interested in developing catalytic applications based on patterned nanofibers,” says Pisignano.