Advanced synthesis of conductive polyaniline using laccase as biocatalyst

18 p.-7 fig.-1 tab.Polyaniline is a conductive polymer with distinctive optical and electrical properties. Its enzymatic synthesis is an environmentally friendly alternative to the use of harsh oxidants and extremely acidic conditions. 7D5L, a high-redox potential laccase developed in our lab, is the biocatalyst of choice for the synthesis of green polyaniline (emeraldine salt) due to its superior ability to oxidize aniline and kinetic stability at the required polymerization conditions (pH 3 and presence of anionic surfactants) as compared with other fungal laccases.Doses as low as 7.6 nM of 7D5L catalyze the polymerization of 15 mM aniline (in 24 h, room temperature, 7% yield) in the presence of different anionic surfactants used as doping templates to provide linear and water-soluble polymers. Aniline polymerization was monitored by the increase of the polaron absorption band at 800 nm (typical for emeraldine salt). Best polymerization results were obtained with 5 mM sodium dodecylbenzenesulfonate (SDBS) as template. At fixed conditions (15 mM aniline and 5mM SDBS), polymerization rates obtained with 7D5L were 2.5-fold the rates obtained with commercial Trametes villosa laccase. Moreover, polyaniline yield was notably boosted to 75% by rising 7D5L amount to 0.15 μM, obtaining 1g of green polyaniline in 1L-reaction volume. The green polymer obtained with the selected system (7D5L/SDBS) holds excellent electrochemical and electro-conductive properties displayed in water-dispersible nanofibers,which is advantageous for the nanomaterial to be readily cast into uniform films for different applications.This work was funded by INDOX (KBBE-2013-7-613549) European project and NOESIS (BIO2014-56388-R) Spanish national project.Peer reviewe

Naive realism and the cognitive penetrability of perception

Perceptual experience has representational content. My argument for this claim is an inference to the best explanation. The explanandum is cognitive penetration. In cognitive penetration, perceptual experiences are either causally influenced, or else are partially constituted, by mental states that are representational, including: mental imagery, beliefs, concepts and memories. If perceptual experiences have representational content, then there is a background condition for cognitive penetration that renders the phenomenon prima facie intelligible. Naïve realist or purely relational accounts of perception leave cognitive penetration less well-explained, even when formulated with so-called â��standpointsâ�� or â��third relata.â�

Cyclic voltammetry curves of PANI obtained with 7D5L and SDBS (a) or AOT (b) as templates (after isolation with ethanol) compared with commercial emeraldine salt (c).

<p>Cyclic voltammetry curves of PANI obtained with 7D5L and SDBS (a) or AOT (b) as templates (after isolation with ethanol) compared with commercial emeraldine salt (c).</p

Advanced Synthesis of Conductive Polyaniline Using Laccase as Biocatalyst

<div><p>Polyaniline is a conductive polymer with distinctive optical and electrical properties. Its enzymatic synthesis is an environmentally friendly alternative to the use of harsh oxidants and extremely acidic conditions. 7D5L, a high-redox potential laccase developed in our lab, is the biocatalyst of choice for the synthesis of green polyaniline (emeraldine salt) due to its superior ability to oxidize aniline and kinetic stability at the required polymerization conditions (pH 3 and presence of anionic surfactants) as compared with other fungal laccases. Doses as low as 7.6 nM of 7D5L catalyze the polymerization of 15 mM aniline (in 24 h, room temperature, 7% yield) in the presence of different anionic surfactants used as doping templates to provide linear and water-soluble polymers. Aniline polymerization was monitored by the increase of the polaron absorption band at 800 nm (typical for emeraldine salt). Best polymerization results were obtained with 5 mM sodium dodecylbenzenesulfonate (SDBS) as template. At fixed conditions (15 mM aniline and 5mM SDBS), polymerization rates obtained with 7D5L were 2.5-fold the rates obtained with commercial <i>Trametes villos</i>a laccase. Moreover, polyaniline yield was notably boosted to 75% by rising 7D5L amount to 0.15 μM, obtaining 1g of green polyaniline in 1L-reaction volume. The green polymer obtained with the selected system (7D5L/SDBS) holds excellent electrochemical and electro-conductive properties displayed in water-dispersible nanofibers, which is advantageous for the nanomaterial to be readily cast into uniform films for different applications.</p></div

Comparison of 7D5L and <i>T</i>. <i>villosa</i> laccase (TvL) for stability at acid pH and high temperature, and relative activity on aromatic amines (DMPD) respecting the activity with ABTS.

<p>Comparison of 7D5L and <i>T</i>. <i>villosa</i> laccase (TvL) for stability at acid pH and high temperature, and relative activity on aromatic amines (DMPD) respecting the activity with ABTS.</p

Advanced Synthesis of Conductive Polyaniline Using Laccase as Biocatalyst - Fig 3

<p>UV-visible spectra of aniline polymerized for 24 h with 0.1 U/mL of 7D5L and different concentrations of SDBS (10-fold diluted) (a). Aniline (15 mM) polymerization followed by the increase of absorbance at 800 nm, using 5 mM SDBS and 0.1 (diamonds), 1 (squares) or 2 U/mL (crosses) of pure 7D5L produced in <i>A</i>. <i>oryzae</i> (b).</p

Polymerization rates (followed by the increase of absorbance at 800 nm) during 24 h of reaction with 0.1 U/mL of 7D5L and TvL using 15mM aniline and 5 mM SDBS.

<p>Polymerization rates (followed by the increase of absorbance at 800 nm) during 24 h of reaction with 0.1 U/mL of 7D5L and TvL using 15mM aniline and 5 mM SDBS.</p

Polyaniline structures observed by SEM.

<p>Polymerization was carried out with 7D5L, 15 mM aniline and 5mM of different templates. Nanofibers obtained with SDBS (a). Granular spheres obtained with 5 mM AOT (b). Splinters obtained with 5 mM SDS (c). Amorphous agglomerates obtained with 5 mM SLES (d). Amorphous agglomerates obtained after washing (a) with ethanol (e). Micro-sized granular agglomerates of commercial PANI (f).</p

FTIR spectroscopy of PANI showing the representative bands for emeraldine salt.

<p>PANI obtained with 7D5L, 15 mM aniline and 5 mM SDBS (a). Same polymer after removal of SDBS with ethanol (b). Commercial emeraldine salt (c).</p