Lab talk
May 29, 2009
Patterned nanocomposites: a simple route to success
Size-tuned semiconductor nanocrystals can be formed in situ in selected areas of polymer matrices leading to nanocomposite materials. Nanocomposites of this kind are of great research interest because they combine nanocrystals with unique size-dependent electronic and optical properties, and polymers that can act as protective agents against oxidation and aggregation, while providing the opportunity for easy manipulation and processing, which is essential for any application. The main target for many groups involved in the field is the formation of nanocomposite structures on the micro/nanoscale with simultaneous control over the dimensions of the nanoparticles involved.
Despina Fragouli and her colleagues at the National Nanotechnology Laboratory (NNL), Lecce, Italy, have come up with a simple and fast route to achieving well defined patterns of nanocomposite materials with full control of the size of the incorporated nanoparticles.
The group uses polymer films containing metal precursors as starting materials. On pulsed UV laser irradiation of the sample, the researchers observe a chemical modification of the precursors leading to the formation of CdS nanocrystals, strictly in the irradiated area. The host polymer matrix remains macroscopically and microscopically unaffected and regions adjacent to the irradiation areas are left intact.
It is shown that the very first laser pulses form very small CdS nanoparticles in the quantum size regime. With an increasing number of pulses, an increase in the size of the CdS nanoparticles is observed, which results in a red shift of the emission of the nanocomposites. Testing different precursors reveals the best combination of polymer-precursor-irradiation conditions, giving the possibility of homogeneous formation of nanocrystals with narrow emission dependent on their size.
The team is continuing its study by testing various polymers, precursors and different irradiation conditions, and is looking to widen the applicability of this method across a variety of fields such as gas or biosensors, emitting devices and microfluidics.
The researchers presented their work in Nanotechnology.
About the author
Despina Fragouli is a postdoc fellow in the Nanocomposite and Responsive Materials Division of the National Nanotechnology Laboratory (NNL) at Lecce, Italy, with PhD student Gianvito Caputo, division leader Dr Athanassia Athanassiou and director Prof. Roberto Cingolani. Her main research interest is focused on the development, fabrication and characterization of solid composite materials that are realized by the appropriate combination of polymers and inorganic nanoparticles. The main target is the formation of nanocomposites that exhibit unique optical, electronic or magnetic properties, and the appropriate combination with smart responsive molecules, leading to the development of novel materials and as a next step, devices with enhanced characteristics. For the realization of this work, the group collaborated with Dr Pier Paolo Pompa, researcher of the division of Nanobiomolecular Electronics and Nanobiotechnology at NNL, and with the group of Prof. Leander Tapfer of the Advanced Physical Technologies and New Materials Department at the Italian National Agency for New Technologies, Energy and the Environment (ENEA) at Brindisi, Italy, with main contributors Dr Vincenzo Resta and Dr Anna Maria Laera.
