Mechanism of dc conduction in polyaniline doped with sulfuric acid

Luthra, Vandna; Singh, Ramadhar; Gupta, Shweta; Mansingh, Abhai

doi:10.1016/s1567-1739(02)00205-5

Cited by 77 publications

(54 citation statements)

References 19 publications

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“…This is a very important result because the two previous theoretical works 6,7 predicted huge energy differences ͑Ͼ11 kcal/ mol͒ between polaron and bipolaron structures, thus making it impossible to rationalize the experimentally observed equilibrium between these two lattices. [12][13][14][15][16][17][18][19][20] Furthermore, exploiting our computer capabilities until the very limit ͑837 basis functions͒, we computed the stability of a The actual periodicity is 2c according to Fig. 1 …”

Section: -2mentioning

confidence: 99%

“…This fact leads to the conclusion that the real picture of doped PANI emerging from the present study is a ESI͑S͒ ͓bipolaron͔ * ESIIЈ͑D͒ ͓polaron͔ thermodynamic equilibrium shifted toward the polaronic lattice, in full agreement with experimental evidence. [12][13][14][15][16][17][18][19][20] Neither CPMD simulations 7 nor ab initio 1D calculations 6 were able to predict the coexistence of both lattices. Indeed, both methodologies predict a huge energy difference ͑Ͼ11 kcal/ mol͒ between them.…”

Section: Mechanismmentioning

confidence: 99%

“…5 Although recent theoretical works [6][7][8] have greatly contributed to the understanding of the experimental behavior exhibited by doped PANI, a number of fundamental questions remain to be uncovered, namely, ͑a͒ the mechanism proposed by Stafström et al 4 has been analyzed by using a one-dimensional ͑1D͒ model 6 but it remains to be theoretically validated by using more realistic two-dimensional ͑2D͒ and three-dimensional ͑3D͒ models; ͑b͒ although polaronic 4 and bipolaronic [9][10][11] lattices have been proposed for doped PANI, solid and abundant experimental evidence strongly suggests that a combined model with the coexistence of polarons and bipolarons is very likely. [12][13][14][15][16][17][18][19][20] Depending on the preparation technique and composition of the sample, one of the two lattices can prevail over the other. 21,22 However, ab initio calculations 6 and Car-Parrinello molecular dynamics ͑CPMD͒ simulations 7 predict energy differences between polaron and bipolaron lattices to be greater than 11 kcal/ mol.…”

Section: Introductionmentioning

confidence: 99%

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A suitable model for emeraldine salt

Varela‐Álvarez

Sordo

2008

The Journal of Chemical Physics

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A new mechanism for the formation of doped polyaniline is presented. Besides providing suitable structural and spectroscopic parameters, the new mechanism allows for the rationalization of the experimentally observed equilibrium between polaron and bipolaron defects in emeraldine salt. The magnetic behavior and the “metallic island” model for conduction in doped polyaniline are also theoretically supported by the new proposal.

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Section: -2mentioning

confidence: 99%

Section: Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A suitable model for emeraldine salt

Varela‐Álvarez

Sordo

2008

The Journal of Chemical Physics

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“…The variable-range hopping (VRH) conduction mechanism originally proposed by Mott for amorphous semiconductors (Mott & Davis, 1979) assuming a phonon-assisted hopping process has also been observed in conducting polymers and their composites at low temperature (Ghosh et al, 2001;Luthra et al, 2003;Singh et al, 2003). Bulk conductivity of conducting polymers depends upon several factors, such as the structure, number and nature of charge carriers, and their transport along and between the polymer chains and across the morphological barriers (Long et al, 2003).…”

Section: Variable-range Hopping Mechanismmentioning

confidence: 97%

Charge Transport and Electrical Switching in Composite Biopolymers

Katana¹,

Kipnusu²

2011

Biomaterials - Physics and Chemistry

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“…17 Their structural versatility is attracting researchers for their multiple applications such as in rechargeable batteries, light emitting diodes, super capacitors, sensors, solar cells, actuators, separation and etc.…”

Section: -16mentioning

confidence: 99%

Nano Structured Potentiometric Sensors Based on Polyaniline Conducting Polymer for Determination of Cr (VI)

Mohammad‐Khāh

Ansari²,

Delavar³

et al. 2012

Bulletin of the Korean Chemical Society

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In this paper, a potentiometric sensor based on polyaniline conducting polymer for potentiometric determination of Cr (VI) ions is reported. Polyaniline was synthesized electrochemically (cyclic voltammetry method) onto a micro pencil graphite electrode (0.7 mm diameter) in the presence of HCl and diphenylcarbazide (termed as (PGE/PAni/DPC). Some initial experiments were performed in order to find out the optimized conditions for preparation of the introduced Cr (VI) sensor electrode. The plot of E vs. log [Cr (VI)], showed a linear response in the range from 1.0 × 10 −6 to 1.0 × 10 −1 M. High repeatability with the detection limit of 8.0 × 10M was obtained.Key Words : Chromium (VI), Potentiometric sensor, Polyaniline, Diphenylcarbazide IntroductionChromium is an element widely used in industrial activities such as chrome plating and electroplating, metal smelting and metallurgy to manufacture alloys, dye stuff industries, leather tanning and wood treatment.1,2 It exists in the environment as Cr (III) and Cr (VI) oxidation states, which present different chemical properties. Cr (III) is a stable and slightly soluble cation considered an essential microelement, while Cr (VI) is a soluble and mobile anion, known as a highly toxic pollutant, with mutagenic and carcinogenic effects.3,4 While chromium in its Cr (III) form is not considered a toxic element and is a required diet nutrient. In humans, Cr (VI) exposure caused marked irritation of the respiratory tract and ulceration and perforation of the nasal septum in workers in the chromate producing and using industries.Due to the high toxicity of Cr (VI), it is essential to determine Cr (VI) rather than the total chromium concentration using a rapid and simple method that can be applied in industrial and environmental fields.4,5 The chemistry of Cr (VI) is very dependent on the pH of solution. Under acidic conditions (pH=2-4) chromium ion is predominantly exist as HCrO 4 − and Cr 2 O 7 2− and under neutral or alkaline media it exist predominantly as chromate ion (Eqs. 1, 2).Several analytical techniques have been developed to detect chromium, ranging from visible-light spectrophotometry to ion chromatography, atomic absorption spectrometry, GC-MS, electron probe microanalysis, flow injection analysis-ICP, synchrotron X-ray microprobe, isotope dilution mass spectroscopy and etc. Most of them, however, do not distinguish the oxidation state of chromium, and only total concentrations are measured. When the discrimination of the chromium species is necessary, for example in environmental and biochemical studies, chemical sensors can be a good choice. 5-7Potentiometry is an analytical technique very used for monitoring because it presents a number of advantages, such as simplicity, low cost, short measurement time, selectivity, adequate precision and accuracy, as well as ability to determine the analytes in coloured and turbid samples.8 Also, it is possible to determine and differentiate between chemical species of one metal depending on the used compound as the sensing...

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Mechanism of dc conduction in polyaniline doped with sulfuric acid

Cited by 77 publications

References 19 publications

A suitable model for emeraldine salt

A suitable model for emeraldine salt

Charge Transport and Electrical Switching in Composite Biopolymers

Nano Structured Potentiometric Sensors Based on Polyaniline Conducting Polymer for Determination of Cr (VI)

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