The reduction of silver nitrate with various polyaniline salts to polyaniline–silver composites

Synthesis and characterization of antimicrobial colloidal polyanilines

The potential application of colloidal polyaniline (PANI) as an antimicrobial is limited by challenges related to solubility in common organic solvents, scalability, and antimicrobial potency. To address these limitations, we introduced a functionalized PANI (fPANI) with carboxyl groups through the polymerisation of aniline and 3-aminobenzoic acid in a 1:1 molar ratio. fPANI is more soluble than PANI which was determined using a qualitative study. We further enhanced the solubility and antimicrobial activity of fPANI by incorporating Ag nanoparticles onto the synthesized fPANI colloid via direct addition of 10 mM AgNO3. The improved solubility can be attributed to an approximately 3-fold reduction in size of particles. Mean particle sizes are measured at 1322 nm for fPANI colloid and 473 nm for fPANI-Ag colloid, showing a high dispersion and deagglomeration effect from Ag nanoparticles. Antimicrobial tests demonstrated that fPANI-Ag colloids exhibited superior potency against Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli, and Bacteriophage PhiX 174 when compared to fPANI alone. The minimum bactericidal concentration (MBC) and minimum virucidal concentration (MVC) values were halved for fPANI-Ag compared to fPANI colloid and attributed to the combination of Ag nanoparticles with the fPANI polymer. The antimicrobial fPANI-Ag colloid presented in this study shows promising results, and further exploration into scale-up can be pursued for potential biomedical applications.

Mapping and Tuning the Fluorescence of Perfluorinated Polyanilines Synthesized through Liquid-Liquid Interfaces

A series of light-emitting perfluorinated polyanilines were synthesized by the oxidative polymerization of 3-perfluorooctyl aniline through a variety of aqueous/organic interfaces. According to the interfacial tension between the two solvents (the organic being chloroform, dichloromethane, perfluorinated ether, toluene, or o-dichlorobenzene), we obtain distinctive classes of materials based on the crystal packing, protonation, and oxidation state of the polymeric chains. We distinguish between soluble fractions with a distinctive, strong, and red-shifted photoluminescence pattern and an insoluble precipitate which can be subsequently solubilized in a mixture of acetone and toluene. The emission maximum for the insoluble fraction is located in the ultraviolet or blue region with a small Stokes shift; maxima for the soluble counterparts are in the green to yellow region. The soluble derivatives demonstrate a significantly smaller band gap compared to the monomer and large Stokes shifts up to 163 nm; the emission maximum for the most red-shifted emission was located at λ(em) = 548 nm. Their redox activity toward silver nanoparticles, their sensor reactivity with organic acid and bases, and the subsequent changes in the optical properties were demonstrated and the structure of the materials was evaluated with NMR, X-ray diffraction, and FTIR/Raman spectroscopy.

Self-patterning of fine metal electrodes by means of the formation of isolated silver nanoclusters embedded in polyaniline

A novel self-patterning technique, which is not based on surface energy differentiation with low or high surface energy as used in conventional surface energy techniques, is presented, using polyaniline and an organometallic silver compound. The underlying mechanisms used to control the electrical conductivity of the metallic silver converted from the organometallic silver compound by a thermal process are also analysed, with electrical and microstructural characterizations. It is found that polyaniline in conjunction with the organometallic silver compound changes its oxidation state from the conductive emeraldine form to the non-conductive pernigraniline form, and silver nanoclusters in the presence of polyaniline do not form a continuous conductive network, although the sheet resistance of silver nanoclusters in the absence of polyaniline is as low as 4.27 +/- Omega/ square at the curing temperature of 230 degrees C. By means of these chemical and physical traits of polyaniline and the organometallic silver compound, alternating conductive and non-conductive stripes were self-patterned without the aid of surface energy patterning techniques, the linewidth and nominal pitch of which went down to 23.2 +/- 0.7 microm and 40 microm, respectively.