Dedoping electrochemical

Redox cycled polymers, which electrochemically doped and dedoped, are used for energy storage (batteries) and when one wants to have a property tuned by a potential. For instance, in the case of smart windows the color or absorbance of a glass window can be controlled electrically. 

PPy film is blue-violet in doped (oxidized) stet. Electrochemical reduction yields the yellow-green undoped form. The schematic of the doping/dedoping process can be given as... 

NMR spectroscopy will provide a simpler spectral pattern, when compared with NMR spectroscopy, because a given N resonance line may correspond to a given structure. Therefore, the structure of doped and dedoped N-labeled polypyrrole films can be successfully studied by high resolution solid-state NMR [14, 15]. Doped and dedoped samples were prepared by electrochemical polymerization [16] using 20-30% N-labeled pyrrole. To obtain a dedoped sample, the electrodes were inverted after the doping experiment and the same voltage applied. 

Random co-polymers of methyl and octyl thiophenes were prepared electrochemically by Pei et al. [101] with the purpose of checking the thermal dedoping behaviour of such materials, based on the idea that long and short side chains simultaneously present should create additional space for the dopant molecules. It was found that the doping stability is intermediate between that of the parent polymers, and depends on the composition. Sfructural studies of the materials were not performed. 

PANI-NFA 2O5 is promising nanocomposite material for utilization as a cathode for ion-Li batteries [292,293]. PANI-NFs have been used as a cathode material for rechargeable Li-polymer cells assembled with a gel polymer electrolyte [152], and in an aqueous PANI-Zn rechargeable battery [261]. Dispersions of dedoped PANI-NFs in poly(vinyhdene fluoride-hexafluoropropylene)-based gel polymers can be used as electrolyte membranes for rechargeable Li batteries [513]. PANI-NF and PANI-NT arrays, which show superior electrochemical properties to the bulk counterpart, can be applied to Li-polymer thin-film batteries, which are shape-flexible and specifically suitable for powering integrated circuit cards and microelectromechanical systems [514,515]. 

Figure 5.10 Raman spectra (Kexc= 1064 nm) of PANI/SWNT composites obtained by electrochemical polymerization of aniline on a SWNT film in HCI 0.5 M. Curve 1 corresponds to the SWNT film Raman spectrum. Curves 2-4 and 6-8 show the evolution of the Raman spectrum after 25, 50, 75, 100, 150, and 300 cycles, respectively, carried out in the potential range (-200 +700) mV vs. SCE with a sweep rate of 100 mV s The dedoping of the PANI-salt-functionalized SWNT films (curves 4 and 8), as a result of the chemical reaction with NH4OH 1M solution, is illustrated in curves 5 and 9. (Reprinted with permission from Carbon, Covalent functionalization of single-walled carbon nanotubes by aniline electrochemical polymerization by M. Baibarac, I. Baltog, S. Lefrant et ah, 42, 15, 3143-3152. Copyright (2004) Elsevier Ltd)...

Repetitive square-wave potential techniques switch the potential continuously between the strongly reductive value necessary for the nucleation of the metal particles and a more positive one that is chosen to promote reoxidation of the CP material and thus recuperation of its conducting state, and/or unproved penetration of metal complex anions in the CP layer. Metal complex anions that are used as sources of metal reduction become partially consumed, but also expulsed as doping anions in the course of the reductive dedoping pulse. The size of the electrodeposited metal particles has been found to depend essentially on the frequency of the potential pulses [37,169] (Table 7.3). In fact, the data summarized in Table 7.3 show that by appropriate adjustment of the corresponding parameters, all of the currently exploited electrochemical techniques may result in the deposition of metal NPs in CPs. 

Fig. 7.4 Absorption spectra of doped and dedoped DG-structured P3MT films on FTO-coated glass. Negative absorbance values are most likely due to a higher reflectance of the bare FTO substrate used for calibration compared to the dull polymer films, a Chemical dedoping for Imin in an aqueous hydrazine solution (50-60%). Since the films are handled in air after reduction they might be subject to oxidation before recording the dedoped spectrum, b Electrochemical dedoping performed in an aqueous O.IM liC104 solution. Compared to (a) these spectra were measured in-situ. The data was recorded by Harry Benison and Michael Price...

Hu, Y., Tracy, C., Gao, J., 2006. High-resolution imaging of electrochemical doping and dedoping processes in luminescent conjugated polymers. Appl. Phys. Lett. 88,123507-1123507. 

In this section, we introduce post-synthetic treatments that enable further modification of the physical properties such as the structural, electrical, and optical properties of the as-prepared light-emitting polymer nanostructures. Of the various methods of controlling the intrinsic characteristics of nanostructures, we discuss the electrochemical doping and dedoping process using cyclic voltammetry (CV) and unfocused electron (E)-beam irradiation. Hydrothermal treatment of undoped NPs is presented, which involves application of external pressure and heat to NPs. Finally, we describe hybridization with nanoscale... 

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