Acid Blue dyes in polypyrrole synthesis: The control of polymer morphology at nanoscale in the promotion of high conductivity and the reduction of cytotoxicity
Graphical abstract
Introduction
The preparation of conducting polymer materials has become an important branch of materials research. Nanostructured conducting polymers [1], such as polypyrrole (PPy) [[2], [3], [4]] or polyaniline [5,6], are fabricated by various chemical-oxidation methods. The preparation of one-dimensional polymer morphologies requires the presence of structure-guiding additives that produce hard templates [7,8], soft templates [9,10], reactive-templates [11], or self-degraded templates [12]. Template-free method has also been demonstrated in the preparation of polyaniline nanotubes [13]. The understanding of the processes underlying the formation of a specific morphology and its relation to the conductivity, however, is still a challenge.
Polypyrrole [14,15] in various nanostructures (e.g., nanoparticles, nanotubes, nanowires, thin films, etc.) has been prepared by oxidation of pyrrole in aqueous media and it has subsequently been used in supercapacitors [4,[16], [17], [18], [19]], sensors [[20], [21], [22], [23]], corrosion protection [24], as catalysts supports [25], and as anodes for high-performance lithium-ion batteries [26,27]. The promising applications are expected in biomedicine, where conducting polymers will be used in electrical monitoring or stimulation of biological objects. For example, polypyrrole and its composites can promote neurite outgrowth [28,29], be used as electrically controlled drug-delivery systems [30] or as artificial muscles [31,32].
A substantial effort has recently been exerted on the preparation of polypyrrole nanotubes, in order to increase the conductivity of resulting materials from units S cm–1, which is typical for globular PPy, to 60 S cm–1 [2], and even above 100 S cm–1 [33]. The most common way how to convert the morphology in favour of nanotubes is represented by addition of methyl orange (MO) to the polymerization mixture [2,12,34,35]. The use of resulting materials in biological application, however, is difficult due to the toxicity of MO. Other dyes, such as Acid Blue 25 [36], Acid Blue 41 [37], Acid Red G [38], Acid Violet 19 [39], or methylene blue [40] have also been studied as structure-guiding agents for PPy preparation. The morphology of PPy prepared in the presence of Acid Blue 25 turned to clusters of nanowires with simultaneous increase in conductivity from units S cm–1 up to ≈20 S cm–1. Such one-dimensional structures have successfully been tested as electrode material in supercapacitors [36]. Also the addition of Acid Violet 19 improved conductivity of PPy nanoparticles to ≈40 S cm–1 [39]. However, the presence of some other dyes, such as Acid Green 25, Reactive Black 5, Thymol blue or Indigo carmine, led to a significant decrease in conductivity of PPy [40].
The biocompatibility is a complex materials property for applications pertaining the field of biomedicine. The cytotoxicity is generally believed to be the test of the first choice when the biocompatibility of any material is considered. This is due to the fact that many biological tests can be predicted by the results of cytotoxicity. There are only few studies focused on the biocompatibility of PPy [[41], [42], [43]], especially in form of powders. It is generally accepted, that the biocompatibility of conducting polymers is influenced especially by protonating acids and the presence of residual precursors or oligomers rather than by the polymer itself [44]. The effort to find alternative dopants is therefore obvious in the literature. Also the study focusing on the purification of conducting polymers has been published [45]. The nanostructured conducting polymers possess physicochemical properties which enable their biomedical applications. Their cytotoxicity assessments, however, have been generally neglected in the literature and this motivated the present work.
In the present paper, the influence of two closely related anthraquinone dyes, Acid Blue 25 and Acid Blue 129 (Fig. 1a), on the morphology and electrical conductivity of PPy has been studied. It is shown for the first time that, despite the similarity in molecular structure, their influence on PPy formation substantially differs. Acid Blue 25 acts as a template to produce PPy nanowires during the oxidation of pyrrole with iron(III) chloride as oxidant (Fig. 1b), with enhanced conductivity up to 60 S cm–1, which is three times higher than that reported for this dye in the literature [30]. The presence of the second dye also improved the conductivity but it had no impact on morphology of PPy, which remained globular. The special attention was paid to investigate the cytotoxicity of new highly conducting polypyrroles.
Section snippets
Preparation
Pyrrole (≥98%), iron(III) chloride hexahydrate, Acid Blue 25 (AB 25; sodium 1-amino-4-anilinoanthraquinone-2-sulfonate, dye content 45%) and Acid Blue 129 (AB 129; sodium 1-amino-4-(2,4,6-trimethylanilino)anthraquinone-2-sulfonate, dye content 25%), all from Sigma-Aldrich, have been used as supplied without any correction for true dye content.
Polypyrrole was prepared by the oxidation of pyrrole with iron(III) chloride in aqueous medium [40] (Fig. 1b). In a typical synthesis, 0.2 M pyrrole was
Morphology
The typical polymerization of pyrrole led to a globular morphology which is well known from literature [14,15,40,46]. After introducing a structure-guiding agent AB 25 to the synthesis, PPy nanowires were produced (Fig. 2Figs. 2a,c, Fig. 33a and Fig. 44a,c). In the presence of AB 129 at all oxidant-to-pyrrole mole ratios, the globular PPy has exclusively been obtained (Fig. 2Figs. 2b,d, Fig. 33b and Fig. 44b,d). When the ratio increased, the small increase in PPy particle size was visible.
The role of dyes
The
Conclusions
The preparation of polypyrrole nanowires by the oxidation of pyrrole with iron(III) chloride in the presence of structure-guiding dye, Acid Blue 25, is reported. The dye produces a template for the growth of polypyrrole under acidic conditions afforded by iron(III) chloride oxidant. The conductivity was improved from units S cm–1, which is typical for globular polypyrrole prepared in the absence of dyes, to ca 60 S cm–1, for polypyrrole prepared in the presence of Acid Blue 25. Both the yield
Acknowledgments
The authors thank the Czech Science Foundation (17-04109S) for financial support. Y. L. and Y. P. participated in the Postgraduate Course in Polymer Science 2015/6 and 2016/7, respectively, organized by the Institute of Macromolecular Chemistry in Prague. J. Hromádková is acknowledged for SEM and TEM micrographs.
References (54)
- et al.
Recent advances in synthesis, physical properties and applications of conducting polymer nanotubes and nanofibers
Prog. Polym. Sci.
(2011) - et al.
Nanostructured polypyrrole as a flexible electrode material of supercapacitor
Nano Energy
(2016) - et al.
Polyaniline nanostructures and the role of aniline oligomers in their formation
Prog. Polym. Sci.
(2010) - et al.
Template mediated formation of shaped polypyrrole particles
Colloids Surf. A
(2010) - et al.
Synthesis and investigation of microwave characteristics of polypyrrole nanostructures prepared via self-reactive flower-like MnO2 template
Synth. Met.
(2016) - et al.
Preparation, properties and applications of polypyrroles
React. Funct. Polym.
(2001) - et al.
Synthesis and structural study of polypyrroles prepared in the presence of surfactants
Synth. Met.
(2003) - et al.
Facile decoration of polypyrrole nanoparticles onto graphene nanosheets for supercapacitors
Synth. Met.
(2012) - et al.
Polypyrrole electrodes doped with sulfanilic acid azochromotrop for electrochemical supercapacitors
J. Power Sources
(2013) - et al.
Facile synthesis of polypyrrole nanospheres and their carbonized products for potential application in high-performance supercapacitors
Polymer
(2014)
Polypyrrole nanosphere embedded in wrinkled graphene layers to obtain cross-linking network for high performance supercapacitors
Electrochim. Acta
Comparative analysis of sensor responses of thin conducting polymer films to organic solvent vapors
Sens. Actuators B Chem.
Catalytic activity of polypyrrole nanotubes decorated with noble-metal nanoparticles and their conversion to carbonized analogues
Synth. Met.
Facile synthesis of mesoporous ZnCo2O4 coated with polypyrrole as an anode material for lithium-ion batteries
J. Power Sources
Electrical stimulation alters protein adsorption and nerve cell interactions with electrically conducting biomaterials
Biomaterials
Polymer artificial muscles
Mater. Today
Biomimetic electrochemistry from conducting polymers. A review. Artificial muscles, smart membranes, smart drug delivery and computer/neuron interfaces
Electrochim. Acta
Acid blue AS doped polypyrrole (PPy/AS) nanomaterials with different morphologies as electrode materials for supercapacitors
Chem. Eng. J.
Effect of Acid Blue BRL on morphology and electrochemical properties of polypyrrole nanomaterials
Powder Technol.
Polypyrrole nanotubes: the tuning of morphology and conductivity
Polymer
Cytotoxicity of, and innate immune response to, size-controlled polypyrrole nanoparticles in mammalian cells
Biomaterials
Purification of a conducting polymer, polyaniline, for biomedical applications
Synth. Met.
Polyaniline and polypyrrole: a comparative study of the preparation
Eur. Polym. J.
In situ resonance Raman spectroelectrochemistry of polypyrrole doped with dodecylbenzenesulfonate
J. Electroanal. Chem.
Characteristics of vibration modes of polypyrrole on surface-enhanced Raman scattering spectra
J. Electroanal. Chem.
Colloids of polypyrrole nanotubes/nanorods: a promising conducting ink
Synth. Met.
Biocompatibility of polyaniline
Synth. Met.
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