Fourier transforms infrared study on the role of nickel-nanoclusters incorporated in polyaniline films having structure of layer by layer

Fourier transform infrared (FTIR) studies showed the changes in a relative intensity of stretching vibrations of the PANI and PANI-Ni films, in a band of 1480 and 1590 cm-1 , as well as those in a band of 1200 and 1350 cm-1 , and evidenced the conversion of quinoid form of PANI to bipolaron structure, and finally to the more delocalized polaronic sites during protonation. This also shows that nickel-nanoclusters play a role as a source supplying protons to promote the protonation, giving a change in population of quinoid and aromatic forms of PANI, and increasing a number of NH bond. By the promoted protonation, the pernigraniline base and emeraldine base that were formed during electrosynthesis will be transformed into emeraldine salt forms having NH2 + groups breaking the coupling between the P-electrons of nitrogen, and making new positive sites. This may make advantages for the.
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Fourier transforms infrared study on the role of nickel-nanoclusters incorporated in polyaniline films having structure of layer by layer Journal of Chemistry, Vol. 44 (1), P. 128 - 132, 2006 Fourier transforms infrared study on the role of nickel-nanoclusters incorporated in polyaniline films having structure of layer by layer Received 26 July 2005 Tran Trung Department of Electrochemistry, Faculty of Chemical Technology, HUT summary Fourier transform infrared (FTIR) studies showed the changes in a relative intensity of stretching vibrations of the PANI and PANI-Ni films, in a band of 1480 and 1590 cm-1, as well as those in a band of 1200 and 1350 cm-1, and evidenced the conversion of quinoid form of PANI to bipolaron structure, and finally to the more delocalized polaronic sites during protonation. This also shows that nickel-nanoclusters play a role as a source supplying protons to promote the protonation, giving a change in population of quinoid and aromatic forms of PANI, and increasing a number of NH bond. By the promoted protonation, the pernigraniline base and emeraldine base that were formed during electrosynthesis will be transformed into emeraldine salt forms having NH2+ groups breaking the coupling between the P-electrons of nitrogen, and making new positive sites. This may make advantages for the shuttling of electrons between polaronic sites consisting of C-N+ and C-N+•. Two processes, on which the conversion of quinoid-to-aromatic form of PANI can be done, are proposed as follows: i- during the one-step process the conversion occurs simultaneously in the coupling several segments of the same kind of PANI; ii- meanwhile the two-step process, the conversion and the coupling occur alternatively. Key words: FTIR, PANI, Ni-nanoclusters, conversion, protonation. I - Introduction source to promote an internal molecular electron transfer and also as a bridging center for So far, polyaniline (PANI) is still one of the shuttling electronic charge between polymer most widely studied organic conducting chains via a strong hybrid of the unfilled-d polymers, because an important concern of orbitals of transition metal oxide and the lone practical applications of PANI is the strongly pair of electrons of heteroatoms in polymer dependence of its conductivity on the synthesis chains, such as nitrogen atoms [6], or via approach and its parameters, nature of electrostatic interaction between doping electrolyte and of dopants, etc. This gives a molecular anions and potonated imine centers of number of various approaches to prepare a lot of PANI [7]. kind of polyaniline composites in various The deep insights into electrode processes morphology and structures [1 - 5]. Especially, may be laid on IR-based techniques that have nanoparticles that are incorporated in been considered as useful tools in order to conducting polymer matrix are known as a investigate any electrochemical system. Since 128 1981, IR spectroscopy had been used to study containing polyaniline films (PANI-Ni) having the potential-dependent population of the structure of layer by layer were electrodeposited species in the double layer formed at a Pt on a platinum sheet under conditions that are electrode immersed in CH3CN/0.1 M described in elsewhere [2]. For FTIR LiClO4/(n-butyl)4NBF4 [8, 9]. Now there is a lot measurements, both the PANI and PANI-Ni of works [10 - 13], in which IR spectroscopy films were washed in acetone for several times, has been offering a major contribution yielding then scrapped from the working electrode and information on species at or near an electrode, heated at 45oC for 1 hour, under nitrogen such as the determination of molecular atmosphere. A thermonicolet NEXUS 870 symmetries; the identification of functional spectrometer was used to record the FTIR groups, or compound identification; the nature spectra of both PANI and PANI-Ni. of chemical bond. FTIR study also offers further information of intramolecular forces acting III - Results and discussion between atoms of molecule; the intermolecular forces. The obtained FTIR spectra of PANI (Fig. 1) In previous work [2] the effects of nickel and PANI-Ni (Fig. 2) films, respectively show nanoclusters incorporated in PANI matrix on the stretching vibrations at the 1581 and 1486 protonation and formation polaron lattice, a ...