PPy/CNT composite films

Figure 7.9 SEM morphology for PPy [a-c) and PPy/CNTs composite films (d-f) obtained galvanostatically at 0.1mA cm" for 20 min and CVs in 0.1 M LiC104 in propylene carbonate of the PPy/CNTs composite films compared with the pure polymeric ones galvanostatically obtained at different charge densities. Reprinted from Ref. 201.

In another work by the same group, the flexible films with polypyrrole/carbon nanotube (PPy-CNT) composite homogeneously distributed between GN sheets were prepared by flow assembly of the mixture dispersion of GN and PPy-CNT. The thickness of GN-PPy-CNT composite film was 39.7 pm. The SCs of GN-PPy-CNT (52 wt% PPy-CNT) were reported to be 211 Fg and 122 F cm at a current density of 0.2 A g which was higher than those of the GN films (73 Fg and 79 F cm ) and PPy-CNT (164 Fg and 67 F cm ) composites respectively. Significantly the GN-PPy-CNT electrode showed excellent cycling stability (5 % capacity loss after 5000 cycles) [19]. 

PPy or PEDOT/CNT composites are conventionally synthesized by electrodeposition from a monomer/CNT electrolyte solution [93-100]. In general, the presence of CNTs has increased the conductivity of CPs and improved their sensitivity when applied to biosensors. Wu et al. [101] reported that the electrical conductivity of 3 wt% multiwalled carbon nanotube (MWNT)/PPy composites was 150% higher than that of bulk PPy film. While Long et al. [98] reported two orders of magnitude increase in conductivity for MWNT-PPy composites. However, CNTs, especially single-walled nanotubes (SWNTs), have been reported as potentially cytotoxic [102,103]. Sayes et al. reported that addition of carboxyl or sulfonyl phenyl chains to the sidewall of SWNTs reduced their cytotoxic effect [104]. 

Carbon nanotubes (CNTs) can be used as templates for conducting polymers. Composite films of CNTs with PANl, PPy, or PEDOT were prepared via electrochemical codeposition from solutions containing acid treated CNTs and the corresponding monomer [192], Electrochemical synthesis of PPy/CNT nanoscale composites using well-aligned carbon nanotube arrays was reported [193]. 

As was mentioned earlier, negatively charged CNTs can act as counterions in the electrochemical deposition of ECPs [19]. This straightforward method has been used for preparation of amperometric enz mie electrodes via entrapment of the enz3mie in the resulting ECP-CNT composite [63, 64]. Wang et al. developed amperometric glucose biosensors based on the PPy-MWCNT-GOD composite [63]. The composite was prepared by a simple one-step electrochemical method in which p3U role was electropolymerized at a constant potential of 0.7 V in the presence of c-MWCNTs and GOD. Results from the CV measurements showed that the incorporated c-MWCNTs act as counterions that maintain the electrical neutrality of the film. The influence of different parameters, such as the amount of the used MWCNTs, and the... 

Kim et al. electrochemically deposited PPy on a CNT/silica film substrate using a potential cycling method at room temperature. After removal of silica with hydrofluoric acid (HF), CNT/PPy composites with controlled pore size in a three-dimensional (3D) entangled structure of a CNT film were prepared as electrode materials for a pseudo-capacitor [36]. The pore size of the final CNT/PPy composite film could be controlled by changing the amount of silica in the mixed suspension of CNTs and nanosize silica. The SC of the CNT/PPy composite with 83.4 wt.% PPy was 250 F/g at a potential scan rate 10 mV/s in 1.0 mol/L KCl and it decreased by only 15% to 211 F/g at 500 mV/s. 

CNTs, and PPy were electrodeposited simultaneously to construct a 3D highly porous film electrode [85]. Such ternary composite film electrode exhibited a high SC of 300 F/g at 1 A/g as well as a remarkable cycling stability at high rates, which was related to its unique nanostructure and high electrical conductivity. 

The above-discussed factors can be incorporated in CPs by adding nanofiUers (such as CNT or graphene) to CPs [27]. The CP-CNT composites (particularly PPy-CNT and PANi-CNT) have been reported to be used for supercapacitve properties to fulfil the requirements mentioned above. To achieve the goal, the composites have been optimized by using improved synthesis techniques, controlling the nano thickness of the fillers, uniform distribution of the nano-film, etc. 

Composite films of CNTs with other materials, such as conducting polymers or ceramics, are very fascinating materials for the development of electrochemical sensors. Yang and co-workers fabricated an electrode via electropolymerization of acid chrome blue K at an MWNT-functionalized glassy carbon electrode for simultaneous determination of dihydrox-ybenzene isomers in real water samples through applying the first-order linear sweep derivative voltammetry. Polypyrrole (PPy) or polyaniline (PANI) was electrochemically deposited on SWNT networks by Ferrer-Anglada and co-workers ° in 2006, which has been used as solid-state pH sensors. 

Electrochemical polymerization of pyrrole on an SWNT electrode using an aqueous HCl 0.5 M solution as electrolyte, resulted in deposition of a PPy film onto the SWNT layer leading to a composite with a bilayer structure, as demonstrated by Raman spectroscopy [112]. Anew method was developed by S.Cosner eta/, in 2008 [111] SWNTs were functionalized by electropolymerizable pyrrole groups following covalent and noncova-lent strategies. The covalent pyrrole grafting was carried out by ester formation between pyrrole alcohol and chemically oxidized SWNTs. The strong Ti-interactions between pyrene and SWNTs were exploited for the noncovalent adsorption of a new pyrene-pyrrole derivative on the pristine CNT surface. The pyrrole-ester-SWNTs were solubilized in THE and electropolymerized by controlled potential electrolysis at 0.95 V. The PPy/SWNT... 

For the third process, conducting polymers and metal oxides can be simultaneously deposited onto carbonaceous scaffolds by using CNTs or graphene as frameworks during chemical process or electrodes in the electrochemical procedure. This is similar to the one-pot synthesis of binary composites. Besides sequential compositing, ternary composites can also be fabricated by a one-step electrochemiccd deposition to reach desirable porous architectures due to its simplicity and reliability. It was proposed to prepare unique PPy/reduced GO/CNT ternary composites, where reduced GO, CNT, and PPy were electro-deposited simultaneously to construct a three-dimensionally highly porous film electrode (Dingetal., 2012). 

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