Polypyrrole Nanotubes-Silver Nanoparticles Hybrid Nanocomposites: Dielectric, Optical, Antimicrobial and Haemolysis Activity Study

Abstract

In recent times, organic conducting polymers such as polypyrrole (PPy), polyaniline (PAni) and polythiophene (PTh) based hybrid nanocomposites have attracted the immense attention of the researchers worldwide due to their potential technological applications. Owing to their high thermal stability, redox activity, and electrical conductivity, conducting polymer nanostructures are used to entrap metal or metal oxide nanoparticles and carbon-based nanostructured materials. The hybrid nanocomposites overcome the poor processability of the metal or metal oxide nanoparticles. By combining the excellent electrical, optical and biological properties of different nanostructures with good thermal stability, biocompatibility and dielectric properties of conducting polymer nanostructures, the hybrid nanocomposites are unique multifunctional materials for varied applications in microelectronics, sensing, biotechnology, energy storage, etc. Among the conducting polymers, PPy nanostructures are gaining intensive attention due to their remarkable properties such as good environmental stability, redox activity and low toxicity and are excellent host material for metal/metal-oxide nanoparticles. Similarly, silver nanoparticles are of immense interest because of their excellent electrical, surface plasmon absorption and biocidal activity. The present chapter deals with synthesis, characterization, properties and applications of the conducting polymer nanostructures with metal/metal-oxide nanoparticles, carbon nanomaterial and ternary nanocomposites in general and polypyrrole nanotubes-silver nanoparticles hybrid nanocomposites, in particular. The different synthesis approaches of these hybrid nanomaterials with their application on the diverse field have been presented. Moreover, the chapter gives a glimpse of possible future work in this particular area. In the second part of this chapter, the dielectric, optical, antimicrobial and haemolysis activity of polypyrrole nanotubes (PPy-NTs): silver nanoparticles (Ag-NPs) hybrid nanocomposites synthesized by in situ reduction method in our laboratory will be discussed. PPy-NTs synthesized by reactive template method are used as the matrix as well as a capping agent for Ag-NPs synthesized by in situ reduction of silver nitrate. The formation of hybrid nanocomposites is revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The dielectric properties and ac conductivity with varying Ag-NPs loading is analyzed. Maximum conductivity of the order of 1.6 × 10−3 S/cm has been achieved with 15 wt% of Ag-NPs. The effect of Ag-NPs concentration on antimicrobial activity of the nanocomposites is investigated by Kirby–Bauer method. It is observed that the bactericidal performance of the nanocomposites increases with the concentration of Ag-NPs in the nanocomposites. Maximum zone of inhibition is measured around 23 mm with 15 wt% of Ag-NPs against gram negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria. The lowest minimum inhibitory concentration (MIC) values are determined as 0.078 and 0.15625 mg/ml for the nanocomposites having 15 wt% of Ag-NPs against E. coli and S. aureus, respectively. Haemolysis activity of the nanocomposites is carried out with mammalian red blood cell (RBC). All the nanocomposites exhibit haemolysis below the permissible limit of 5 % up to a concentration of 2.5 mg/mL.