Synthesis, Fabrication and Characterization of Silver-Polyaniline Nanocomposite for Electric Devices.

Abstract

Composites of metal nanoparticles with polymers are developing and interesting area of research. The dispersion of the metal nanoparticles in polymer matrices is an important factor while making nanocomposites. The aim of this thesis is to discuss about the synthesis, fabrication and characterization of silver Polyaniline nanocomposite for electronic devices. Two commonly reported classes of methods are available for the preparation of Ag-PANIEB nanocomposite: in-situ and ex-situ methods. In in-situ methods, two steps are generally required. In the first step, the aniline monomer is polymerized in the solution, and silver ions are introduced before or after the polymerization. In the second step, Ag ions in the polymer matrix are decomposed either chemically, thermally, with UV irradiation, or by some other suitable method [1]. In ex-situ methods, Ag nanoparticles are first synthesized by some soft chemistry technique and then dispersed into the polymer matrix using an appropriate method [2]. The ex-situ preparation methods are simple and provide minimum disturbances to the conducting polymer matrix as a host material. But unfortunately, this method has a tendency to form nanoparticle agglomerations and is limited to low nanoparticle concentrations [1]. Generally, nanoparticle agglomeration takes place as a consequence of the large attractive forces between the nanoparticles. These forces of attraction depend on many factors. Avoiding excessive agglomeration in the ex-situ preparation method is an ongoing challenge [3]. In this study, bimodal Ag nanoparticles were prepared by precipitation method in semi-batch reactor [4]. Silver nanoparticles and polyaniline emeraldine base (PANIEB) nanocomposite were synthesized, and the Ag nanoparticles were simply and efficiently blended inside the PANIEB matrix. The uniform distribution of Ag nanoparticles inside the polymer matrix was achieved using isopropyl alcohol (IPA) colloids. The nanocomposites were characterized at Ag nanoparticle weight concentrations of 10%, 15%, and 20%. Transmission electron microscope (TEM) images revealed spherical Ag nanoparticles with a bimodal size distribution (~6 ± 1 and ~9.5 ± 0.5 nm) along with uniform dispersion in the PANIEB matrix. XRD studies proved the presence of Ag nanoparticles in the PANIEB matrix. The optical properties and the chemical compositions of the nanocomposites were determined using UV-vis and FTIR spectroscopy. The presence of PANIEB and IPA were confirmed in all samples. The thermal stability of the nanocomposites was improved by increasing the concentration of silver nanoparticles, as confirmed by TGA analysis. The current-voltage (I-V) characteristics of the thin nanocomposite films showed a linear non-rectifying behavior similar to that of a metal and were compared to those of the pure PANIEB thin film. In addition, the conductivity of the nanocomposite improved several fold with increased Ag nanoparticle concentration. This work extends the practical applications of Ag-PANIEB nanocomposites and offers insight into the interactions of Ag nanoparticles and IPA colloids in the presence of a PANIEB matrix.