Device applications of polymer-nanocomposites

Abstract

In recent years significant progress has been achieved in the synthesis of various types of polymer-nanocomposites and in the understanding of the basic principles which determine their optical, electronic and magnetic properties. As a result nanocomposite-based devices, such as light emitting diodes, photodiodes, photovoltaic solar cells and gas sensors, have been developed, often using chemically orientated synthetic methods such as soft lithography, lamination, spin-coating or solution casting. Milestones on the way in the development of nanocomposite-based devices were the discovery of the possibility of filling conductive polymer matrices, such as poly(aniline), substituted poly(paraphenylenevinylenes) or poly(thiophenes), with semiconducting nanoparticles: CdS, CdSe, CuS, ZnS, Fe3O4 or fullerenes, and the opportunity to fill the polymer matrix with nanoparticles of both n- and p- conductivity types, thus providing access to peculiar morphologies, such as interpenetrating networks, p-n nanojunctions or "fractal" p-n interfaces, not achievable by traditional microelectronics technology. The peculiarities in the conduction mechanism through a network of semiconductor nanoparticle chains provide the basis for the manufacture of highly sensitive gas and vapor sensors. These sensors combine the properties of the polymer matrix with those of the nanoparticles. It allows the fabrication of sensor devices selective to some definite components in mixtures of gases or vapors. Magnetic phenomena, such as superparamagnetism, observed in polymer-nanocomposites containing Fe3O4 nanoparticles in some ranges of concentrations, particle sizes, shapes and temperatures, provide a way to determine the limits to magnetic media storage density, a problem which has been intensively investigated over the last five years.