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http://cimav.repositorioinstitucional.mx/jspui/handle/1004/406| “SYNTHESIS AND CHARACTERIZATION OF PANI / GRAPHENE COMPOSITES | |
| ELCIN COSKUN | |
| ERASTO ARMANDO ZARAGOZA CONTRERAS | |
| Acceso Abierto | |
| Atribución-NoComercial-SinDerivadas | |
| The PAni/Graphene composites by two different methods are studied. In the first
method, graphene oxide is used as the dopant of polyaniline taking the advantage of
GO makes itself as a dopant to polyaniline (PAni) due to its carboxylic acids on its
surface. According to that idea graphene oxide (GO) is reduced by leucoemeraldine
state of PAni, instead of using another reducing agent both to remove oxygene
functionality on the graphite oxide and oxide the PAni in leucoemeraldine state to the
conducting emeraldine state. PAni/reduced graphene (PAni/RGO) with different mass
ratio is prepared. For comparison, PAni/GO composites also is prepared by in situ
polymerization of polyaniline. The composites have been characterized by Fourier
Transform Infrared Spectrum (FTIR spectroscopy), UV-visible (UV-VIS) spectroscopy
and cyclic voltammetry (CV).
FTIR spectroscopy of the PAni/RGO materials showed the typical peaks of the PAni
which can be concluded the presence of PAni in the composites. The characteristic
peaks of the GO were not observed. It was the direct evidence of the removal of the
oxygene functional groups. UV-VIS spectroscopy indicated the same results as FTIR.
According to the results, the leucoemeraldine state of PAni oxided to emeraldine state
while GO reduced. CV studies showed that the materials are electrochemically active. The electrochemical performances were affected by the mass ratio PAni : RGO. The electrochemical performances of the PAni / RGO 100 exhibits closer electrochemical performance to PAni. According to the four-probe technique the electrical conductivity of the materials iii were 0. 845, 0. 44, 0. 279, 0. 06, 0. 05, 0. 02 S cm-1 for PAni, PAni / GO, PAni / RGO 100, PAni / RGO 200, PAni / RGO 300, and PAni / RGO 500 respectively. As a second method, the sulfonation of graphene by two different strategies is studied. Hybrids of PAni and sulfonated graphene (SGrf) are prepared by the polymerization of aniline in the presence of the SGrf . The materials have been characterized by RAMAN spectroscopy, FTIR spectroscopy, thermogravimetric analyse (TGA) , CV and Transmission Electron Microscopy (TEM). Raman spectroscopy results used to calculate D / G intensities of sulfonated graphenes. The results for reduced and sulfonated graphene sheets by sulfonic acid (GSA) and reduced and sulfonated graphene sheets by 6-amino-4-hydroxy-2- naphthalenesulfonic acid (GNSA) and GO samples were 0.96, 0.92 and 0.87 respectively which indicates the formation of smaller graphitic domains than those in GO and graphene-oxide reduction. FTIR spectroscopy of the PAni/ SGrf s showed that clear bands at 1095 and 1037 cm-1 , which are assigned to the symmetric and anti-symmetric stretching of sulfonic groups respectively which points to successful sulfonation of the graphenes. UV-VIS spectroscopy was used to calculate water solubility of the sulfonated graphenes. According to the results, the solubilities of the GSA and GNSA samples were 0. 104 and 0. 138 mg mL -1 respectively. FTIR spectroscopy of the PAni/ SGrf s showed that clear bands at 1095 and 1037 cm-1 , which are assigned to the symmetric and anti-symmetric stretching of sulfonic groups respectively which points to successful sulfonation of the graphenes. UV-VIS spectroscopy was used to calculate water solubility of the sulfonated graphenes. According to the results, the solubilities of the GSA and GNSA samples were 0. 104 and 0. 138 mg mL -1 respectively. TGA indicated that less volatile functionalities are present on GSA and GNSA surfaces comparing to GO as a result of the successful reduction. This pointed to sulfonation method was the efficient way to obtain more thermostable compositions. iv TEM results showed typical-wrinkled morphology of the reduced-sulfonated graphene sheets. Morphologies of the PAni/ SGrf showed the particles of PAni intercalated/covered on the surfaces of the graphene sheets. According to the EDS results the ratio of sulfur element was % 5. 78 in the GNSA sample. It is a good indicator of the sulfonation efficiency. The CV results showed that the materials are electrochemically active at physiological pH likely due to the doping of PAni with SGrf. . In fact, a good electrochemical response is obtained at pH 6 for the PAni/ SGrf s. In addition high conductivity values are obtained by four probe technique. The electrical conductivities were 1. 42, 13. 60, 14. 09, 25. 60, 26. 33 S cm-1 for PAni, GSA, GNSA, PAni/ GSA, PAni/ GNSA samples respectively. General results indicated that the both method was efficient to obtain electrochemically active and electrically conductive materials. This let us the conclude that methods of the dopping the polyaniline with graphene oxide and funcionalization of the polyaniline with the modified graphenes worked very well. The sulfonation method was prominent as higher conductivities obtained compare to pure PAni due to surface modificated graphenes provides better interconnection with PAni as it was stated in the hypotheses. | |
| 20-02-2012 | |
| Tesis de doctorado | |
| Inglés | |
| BIOLOGÍA Y QUÍMICA | |
| Aparece en las colecciones: | Doctorado en Ciencia de Materiales |
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