Device applications of polymer-nanocomposites

In recent years significant progress has been achieved in the synthesis of various types of polymer-nanocomposites and in the understanding of the bas ic principles which determine their optical, electronic and magnetic proper ties. As a result nanocomposite-based devices, such as light emitting diode s, photodiodes, photovoltaic solar cells and gas sensors; have been develop ed, often using chemically orientated synthetic methods such as soft lithog raphy, lamination, spin-coating or solution casting. Milestones on the way in the development of nanocomposite-based devices wer e the discovery of the possibility of filling conductive polymer matrices, such as poly(aniline), substituted poly(paraphenylenevinylenes) or poly(thi ophenes), with semiconducting nanoparticles: CdS, CdSe, CuS, ZnS, Fe3O4 or fullerenes, and the opportunity to fill the polymer matrix with nanoparticl es of both n- and p- conductivity types, thus providing access to peculiar morphologies, such as interpenetrating networks, p-n nanojunctions or "frac tal" p-n interfaces, not achievable by traditional microelectronics technol ogy. The peculiarities in the conduction mechanism through a network of semicond uctor nanoparticle chains provide the basis for the manufacture of highly s ensitive 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 gase s or vapors. Magnetic phenomena, such as superparamagnetism, observed in polymer-nanocom posites containing Fe3O4 nanoparticles in some ranges of concentrations, pa rticle sizes, shapes and temperatures, provide a way to determine the limit s to magnetic media storage density, a problem which has been intensively i nvestigated over the last five years.