Inherently fluorescent polyaniline nanoparticles in a dynamic landscape

Abstract

a b s t r a c tIn this paper we report for the first time on the emissive behavior of two polyaniline (PANI) nanoparticle systems produced via oxidative chemical polymerization in the presence of either poly(vinyl alcohol) (PVA) or chitosan as polymeric stabilizers in water. The emission from PANI nanoparticles is irreversibly quenched by an increase of pH of the suspending medium from acid to neutral (chitosan-PANI) or alkaline (PVA-PANI). Conversely, PANI nanorods synthesized in the same conditions of the above, but in presence of poly(N-vinyl pyrrolidone), is not emissive at any pH. The role of the polymeric surfactant as a soft template is key in controlling the morphology and the properties of the obtained PANI dispersions. FTIR, UV-Vis absorption and photoluminescence excitation (PLE) spectra studies suggest that the emissive properties are related to the establishment of strong, non-covalent interactions between nanoscalar PANI particles and the polymeric surfactant at the pH of synthesis. Morphology examination of the three systems, by both dynamic light scattering (DLS) and Transmission Electron Microscopy (TEM), reveal that photoluminescence is associated to the presence of a genuinely 3D nanoscalar morphology, together with an ordered disposition of PANI chains into aligned crystal planes. Concomitant to the irreversible quenching of the emission signal with increasing pH, there is an evolution of the morphology leading to particle coalescence, coarsening and ultimately phase-separation, with consequent modification of PANI-polymeric surfactant interactions, PANI chains supra-molecular organization and optical properties of the PANI nanoparticles dispersion.

Synthesis, Characterization and Electrical Properties of Nano Metal and Metal-Oxide Doped with Conducting Polymer Composites by in-Situ Chemical Polymerization

“…The very strong peak at 1504 cm -1 is associated with N-B-N stretching vibrations (where B refers to benzenoid ring). The peaks observed in the present work well matches with Pani [5][6][7][8][9][10] Figure 1(b & c) shows all the characteristics peak of Pani with some slight spectral intensity changes. The strong peaks at 2926cm -1 are assigned to asymmetric and symmetric stretching vibration mode of methyl groups [7].…”

Measurement on the structural, morphological, electrical and optical properties of PANI-CSA nanofilms

“…Among all the conducting polymers, due to high electrical conductivity, charge transport mechanism, environmental stability and low synthesis cost, polyaniline (PANI) stands as the most potential conducting polymer. It finds application in bio sensors namely cholesterol sensor [1], glucose sensor [2], gas sensors [3,4] and in other fields such as electromagnetic shielding [5], light emitting devices [6,7], photovoltaic applications [8][9][10][11], light weight batteries [12], organic displays [13] etc. PANI can be tuned to either conducting or insulating nature by doping or dedoping procedure respectively, through reversible chemical, electrochemical process.…”

Synthesis of poly(aniline-co-o-toluidine) nanocolloidal particles in aqueous poly(styrene sulfonic acid) by dispersion polymerization method

“…The most intense peak at 1,400 cm -1 is not straightforward. The above peak can be related to protonated nitrogen atoms of the polymer backbone or to ammonium sulfate byproduct, deriving from APS and incorporated as ''ionic cross linker'' among PAT chains and/or among PAT and the polymeric stabilizer PSS chains [33]. The higher wt% of PSS shows the new peaks at 1,160 and 1,030 cm -1 , which are attributed to asymmetric stretching and symmetric stretching vibration of sulfonic groups, respectively.…”