Jun 17, 2010
Nanoimprinting improves polarization properties of nanofibres
The achievement of miniaturized light-emitting sources is gathering a lot of interest in view of integration in optoelectronics, biosensors and lab-on-a-chip devices. Polarized luminescence is generally reported from individual organic and inorganic nanowires and nanorods, and from molecular materials oriented on substrates. A low-cost alternative is offered by polarized light-emitting fibres realized via electrostatic spinning. This simple and inexpensive technique can deliver nanofibres with lengths up to kilometres. The polarization properties of the material can be tailored by nanopatterning, which can be enabled through room temperature nanoimprint lithography (RT-NIL).
Scientists from the Soft Matter Nanotechnology Group at the National Nanotechnology Laboratory in Lecce, Italy, have used a home-made electrospinning set-up to realize individual light-emitting fibres as well as ordered arrays of fibres. As-spun nanofibres made of light-emitting conjugated materials emit light polarized prevalently along their axis.
Fibres are nanostructured via RT-NIL, which involves the use of a press and master templates consisting of parallel grooves with a sub-micrometre period. The imprinting procedure, carried out entirely at room temperature, is specifically designed and implemented in order to avoid degradation of the optical properties of conjugated polymers. In fact, on nanostructuring, single fibres with grooves imprinted longitudinally to their axis exhibit more than double the light polarization found in pristine samples. The opposite effect is found by nanostructuring the material with grooves orthogonal to the longitudinal fibre axis.
Applications for these modified fibres include the coupling of tailored, nanofibre-based light sources into microfluidic devices and in nanophotonics, where nanopatterned electrospun fibres can be used as basic building blocks to build nanoscale light-emitting elements and lasers.
The researchers presented their work in the journal Nanotechnology.
About the author
The study was performed by the Soft Matter Nanotechnology Group at NNL in Lecce, Italy. The team is part of a collaborative research effort involving scientists from the University of Salento, the CNR-Istituto Nanoscienze and the Italian Institute of Technology (IIT), and is investigating the structural, fluidic and optoelectronic properties of organic materials and bio-systems by a Converging Science Approach. Dr Dario Pisignano, who co-ordinates the team, is currently assistant professor at the University of Salento. Prof. Roberto Cingolani is scientific director at IIT, Dr Andrea Camposeo and Dr Luana Persano, who conducted the optical and nanofabrication experiments, are CNR Researchers. Dr Elisa Mele, who carried out NIL on nanofibres, is currently senior postdoc at the Center for Biomolecular Nanotechnologies of IIT@Unile. Dr Stefano Pagliara just completed his PhD on optically active nanofibres. The authors of the study also thank Dr R Stabile, now at Technical University of Eindhoven, and G Potente, a PhD student in the group, for electron-beam lithography, and acknowledge funding from Regione Puglia ("Progetti Strategici"-Ponamat) and the MIUR-Firb Contract RBIP06SH3W.