Vertically Aligned and Ordered One-Dimensional Mesoscale Polyaniline

Abstract

The growth of vertically aligned and ordered polyaniline nanofilaments is controlled by potentiostatic polymerization through hexagonally packed and oriented mesoporous silica films. In such small pore template (2 nm in diameter), quasi-single PANI chains are likely to be produced. From chronoamperometric experiments and using films of various thicknesses (100-200 nm) it is possible to evidence the electropolymerization transients, wherein each stage of polymerization (induction period, growth, and overgrowth of polyaniline on mesoporous silica films) is clearly identified. The advantageous effect of mesostructured silica thin films as hard templates for the generation of isolated polyaniline nanofilaments is demonstrated from enhancement of the reversibility between the conductive and the nonconductive states of polyaniline and the higher electroactive surface areas displayed for all mesoporous silica/PANI composites. The possibility to control and tailor the growth of conducting polymer nanofilaments offers numerous opportunities for applications in various fields including energy, sensors and biosensors, photovoltaics, nanophotonics, or nanoelectronics.

Mesoporous Silica-Based Materials for Electronics-Oriented Applications

“…On the opposite, polythiophene nanowires of 6 nm in diameter are produced by electropolymerization [166], suggesting that the conducting polymer growth occurs also out of the film (as this value is larger than the mesopore diameter of 2–3 nm for such films). Template electropolymerization can be extended to the generation of other types of electronically-conductive nanowires, such as polypyrrole (PPy) [167], polyaniline (PANI) [168], poly(3,4-ethylenedioxythiophene) (PEDOT) [169] and other kinds of polythiophene [170], or even polyquinone [171]. A strategy to ensure strong and durable attachment of the nanowires onto the electrode surface is the formation of an underlying electrode previously modified with a thin film of the target conducting polymer onto which the mesoporous silica layer is formed and used as hard template for nanowires grown by in situ electropolymerization, remaining attached to the support even after template removal [169,172].…”

“…A strategy to ensure strong and durable attachment of the nanowires onto the electrode surface is the formation of an underlying electrode previously modified with a thin film of the target conducting polymer onto which the mesoporous silica layer is formed and used as hard template for nanowires grown by in situ electropolymerization, remaining attached to the support even after template removal [169,172]. As pointed out for PANI, the growth of polymeric nanowires through the pores can be controlled by the experimental conditions (notably by tuning the electrodeposition parameters, in either potentiostatic or galvanostatic mode), and the resulting nanofilaments isolated from each other (thanks to the mesoporous silica template) exhibit considerably improved electrochemical reversibility (faster switching between doped and undoped states) in comparison to bulk PANI [168]. From charge–discharge measurements, it also appears that the high surface areas developed by the conducting polymer nanowires enable to reach extremely large capacitance values, by several orders of magnitude as compared to PANI or PPy films deposited in the absence of template [168,173].…”

“…As pointed out for PANI, the growth of polymeric nanowires through the pores can be controlled by the experimental conditions (notably by tuning the electrodeposition parameters, in either potentiostatic or galvanostatic mode), and the resulting nanofilaments isolated from each other (thanks to the mesoporous silica template) exhibit considerably improved electrochemical reversibility (faster switching between doped and undoped states) in comparison to bulk PANI [168]. From charge–discharge measurements, it also appears that the high surface areas developed by the conducting polymer nanowires enable to reach extremely large capacitance values, by several orders of magnitude as compared to PANI or PPy films deposited in the absence of template [168,173]. To date, such nanocomposite films made of conducting polymers confined in oriented mesoporous silica films have been essentially applied for electrocatalysis and electroanalysis purposes [174,175,176], but they are also promising in the field of energy [168,173] as briefly mentioned above in the supercapacitors section.…”

“…From charge–discharge measurements, it also appears that the high surface areas developed by the conducting polymer nanowires enable to reach extremely large capacitance values, by several orders of magnitude as compared to PANI or PPy films deposited in the absence of template [168,173]. To date, such nanocomposite films made of conducting polymers confined in oriented mesoporous silica films have been essentially applied for electrocatalysis and electroanalysis purposes [174,175,176], but they are also promising in the field of energy [168,173] as briefly mentioned above in the supercapacitors section.…”

Non‐covalent Immobilization of Iron‐triazole (Fe(Htrz)3) Molecular Mediator in Mesoporous Silica Films for the Electrochemical Detection of Hydrogen Peroxide

“…Long-range charge transfer by electron hopping has been demonstrated for a vertically-aligned ferrocenefunctionalized film [35], but the rate of charge transfer remains limited [34], except in special configuration [36]. Promising ways to promote charge transport in mesoporous silica films are via conducting polymers electropolymerized in the mesopore channels [37] or via the use of redox-active coordination polymers as template in the synthesis of the films [38] because these strategies ensure the electroactive moieties being very close to each other in the hybrid film. Here, we plan to use the iron-triazole complex, Fe(Htrz) 3 (Htrz = 1,2,4,-1H-triazole), as coordination polymer template to generate Fe(Htrz) 3 -doped mesoporous silica films by electrochemically-assisted selfassembly (EASA) on indium-tin oxide (ITO) electrode and its subsequent use for the electrocatalytic detection of hydrogen peroxide.…”