## 3 Nanocomposite Properties
### Nanocomposites for sensing applications.  
Recently a large area of research has focused on the incorporation of nanoscale metals in polymers to design and fabricate advanced optoelectronic and sensor devices.  
Surface modified gold nanorods with thiele terminated poly(ethylene glycol) (PEG) have been homogeneously dispersed in PMMA films to investigate the thermal reshaping of nanostructures at various annealing temperatures [131]. Depending on the annealing temperature, an increasing blue shift of the longitudinal plasmon resonance has been observed and attributed to a decrease in nanorod length. The combination of the thermal induced tunable absorption properties of gold nanorod with polymers can be exploited to fabricate nanoscale devices for sensing applications.  
Dodecanethiol capped Au NPs have been incorporated in an organometallic \(\pi\)-conjugated polymer, namely Pt(II)diethylhypliphenyl (Pt-DEPB) [132]. The formed nanocomposites have been characterized by microstructural, microanalytical and spectroscopical investigations to study their chemical physical properties. Uniform dispersion of Au NPs in the polymer matrix has been achieved and the non-covalent Au-S interaction as well as the chemical composition of the polymer has been preserved in the nanocomposite formation.  
The optical properties based on the plasmon resonance of noble metal NPs are extremely relevant in electrochromic applications. Since surface plasmon absorption depends also on the dielectric properties of the NP host matrix, the incorporation of metal NPs in conducting polymers can be used to fabricate tunable electrochromic devices. Ag and Au NPs have been blended with conducting polymer poly(3,4-ethylenedioxythiophene):poly styrene sulfonate (PEDOT:PSS) to fabricate electrochromicdevices [133]. The spectral tuning of the electrochromic window by simply varying an external bias has been observed. Time response behaviors of the prepared devices have shown slow relaxivities attributed to the high capacitance of the embedded metal NPs. Both the tunable absorption and time response properties exhibited by the prepared nanocomposites make such materials exploitable in the manufacture of full color electrochromic displays.  
In a recent work, [PERSON] and [PERSON] fabricated Schottky barrier diodes consisting of a conducting polymer, such as poly(o-methoxy aniline) (POMA) and Ag NPs [134]. Electrical measurements on the nanocomposites pointed out different I-V behaviors depending on the size and density of NPs, that result in a tuning of the electronic properties from rectification behavior to switching behavior.  
Recently, the optical properties and influence of the addition of Ag NPs on thermal properties of PMMA matrix has been investigated [135]. Spectroscopical measurements of the optical properties have shown that Ag NPs preserve their plasmon absorption when embedded in the polymer matrix. By differential scanning calorimetry (DSC) and thermogravimetry (TG) analyses, the improvement of the polymer matrix thermal stability upon incorporation of a small amount of silver NPs has been observed. Furthermore, metal NPs have been found to enhance thermooxidative stability and glass transition temperature of PMMA matrix.