XRD layers after oxidation. Also the characteristic

XRD measurements were done to investigate the changes incrystalline structure and intercalation of polymer (PPC) between GOinterlayers. Graphite (Fig.

1A) presents a sharp diffraction peak at 2?=26ocorresponding to 0.3435 nm d-spacing. The XRD of GO displays a new peak at2?=11.45o corresponding to 001 reflection with d-spacing = 0.7718nm. The increase in the d-spacing is attributed to the presence of epoxide,carboxylic and hydroxyl groups intercalated between the layers after oxidation.Also the characteristic (002) peak of graphite at 45o wasdisappeared indicating successful oxidation of graphite and the creation ofoxygen containing groups that are distributed between the basal planes leadingto their expansion 26, Regarding CS/GO (Fig.1B), the broad peak at 2? = 11.

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01ocan be explained by the intercalation of CS chains in the interlayer spacing ofGO. In addition, the disappearance of the 11.01o peak afterpolymerization of PY was attributed to the destruction and exfoliation of theregular layered structured GO sheets. In addition no crystalline feature wasobserved for PPY in PPC/GO .The FT-IR spectrum (Fig.2A) were carried out to investigate thesurface chemical nature of pristine graphite and exfoliated graphene. In the spectrum of graphite, the absorption bandsat               3448 cm-1 was known to be the O-H stretchingvibrations, the peak located at 1638 cm-1 could be attributed to the skeletalvibration of C=C from unoxidized sp2 bonds. After the oxidation reaction,the FT-IR spectra of GO apparently changed compared to that of graphite.

Apartfrom the O-H stretching vibrations and skeletal vibration, three newrepresentative peaks arising from GO could be indexed at 1736 cm-1, 1404 cm-1 , 1231cm-1, whichcorresponded to the stretching band of C=O in carboxylic acid moieties, C-OH,C-O-C, respectively. The FT-IR results indicated that oxygen-containingfunctional groups were introduced onto the surface of graphiteconfirming the successful oxidation of graphite into GO. 27-29. Also FT-IRspectrum showed that the sharp characteristic band of hydroxyl group at 3448 cm-1of graphite was shifted to 3428 cm-1 in the case of GO. Chitosan is a well-knowncationic polymer with multi-hydroxyl and amino groups, while GO is negativelycharged with plenty of hydroxyls and epoxides. For chitosan, the peaks at3437cm?1 are corresponding to the N?H stretching vibration, andthe adsorption peaks at          1087cm-1 and 1157cm?1are attributed to the primary alcoholic group of C6?OH and thesecondary alcoholic group of C3?OH. The peak at 1637cm?1is assigned to the carbonyl stretching vibration of the acetylated amino group.After mixing with GO, the band at 1736 cm-1 , 1404 cm-1 ,   1231cm-1 , 3428cm-1 whichcorresponded to the stretching band of C=O in carboxylic acid moieties, C-OH,C-O-C, -OH were shifted to 1711 cm-1, 1379 cm-1, 1155cm-1, 3424cm-1 respectively inthe case of CS/GO (Fig.

2A), which indicating the formation of hydrogen bondingand an electrostatic interaction between chitosan and GO. 30. For the Polypyrrole powders  (Fig. S1), FT-IR spectrum showedthe main characteristic peaks at 788 cm?1 corresponding to C-N bond,1311 cm?1 corresponding to C-H deformation, 1546 cm?1 and1458 cm?1 corresponding to the fundamental vibrations of polypyrrolering, the peak at 1633 cm?1 corresponding to C=C stretching, thepeak at 3423 cm?1 corresponds to the N-H stretching 31, 32. After insitu polymerizationof PY with CS/GO, the FT-IR spectrum (Fig.2B), of PPC/GO nanocomposite showsthe appearance of peaks at 1462 cm-1, 1550 cm-1 and 3415cm-1 are related to the C=C, C=N and N=H stretching vibration in thePPY ring, respectively. The absorption peaks found at 2919 cm-1 and2844 cm-1 are ascribed to asymmetric stretching and symmetricvibrations of CH2, respectively.

The peak at 1711 cm-1characteristicto C=O in CS/GO was shifted to 1721 cm-1 in the case of PPC/GO suggesting the ?-?interaction between the graphene layers and aromatic PPY rings. The appearanceof peak at 787 cm-1 this may be due to additional bond formedbetween pyrrole radical cation and residual carboxyl group of GO during polymerization. Sharp band at 1044Cm-1 due to more skeletal stretching and presence of –NH group forpolypyrrole.

After loading of P4R dye (Fig .2B), the adsorption peaks of PPC/GOat 1462 cm-1, 1550 cm-1, and 3415 cm-1 thatare related to the C=C, C=N, and N=H stretching vibration in the PPY ring wereshifted to 1401cm-1, 1520cm-1 and 3449 cm-1 whilethe absorption peaks found at  2919 cm-1and         2856 cm-1are ascribed to asymmetric stretching and symmetric vibrations of CH2shifted to 2923cm-1 and 2865 cm-1, the C=O stretchingband shift from 1721cm-1 to 1780 cm-1 the bond formedbetween pyrrole radical cation and residual carboxyl group of GO shifted from 787 cm-1 to 790 cm-1,skeletal stretching of –NH of PPY shifted from 1044 cm-1 to 1029 cm-1,this shifts confirms the electrostatic attraction between the anionic P4R dyeand the PPC/GO surface as shown in (table 1) . To explore the successful intercalation of the polymer into GOinterlayers and gain insight into the state of dispersion GO layers within thepolymer matrix and calculate the average flake thickness, SEM analysis (Fig.3)was performed at different magnifications for GO, CS/GO and PPC/GO. GO  powder is composed of aggregated stackednanosheets, this is due to its high surface area, the GO flakes (Fig.3 A,B,C)connected to form these aggregations via ?-? interactions, vanderwaals forcesand H-bonding.

Upon intercalation GO with CS 33, 34, disaggregation into thinner layers is observed in (Fig.3 D,E,F).This suggests the intercalation of CS polymer chains between the GO sheetsto form CS/GO nanocomposites. The hydrogen bonding  intra chain between oxygen in -OH and -COOHgroups of GO sheets and hydroxyl group in CS and the ionic interaction between-COO- and NH3+ would exceed the vanderwaalsforces and ?-? slacking interactions that maintain the aggregation of GOsheets. This leads to the expanding of GO sheets during ultra-sonicationprocess. There is appearance of spherical structure in the case of PPC/GO (Fig.

3G,H,I)  that shows polypyrrole on thesurface of CS/GO. These results confirm that the intercalation of polymers intoGO interlayer induces dissagregation of the GO sheets resulting into thinnersheets. Regarding PPC/GO nanocomposite a homogenous dispersion of GO flakeswithin polymer matrix is observed, the flakes appear to be bended withoutoccurrence of clusters or agglomerate. The morphology of GO, CS/GO ,PPC/GO was examined thoroughly by TEMimages,  (Fig.4) GO showsthe formation of several transparent thin sheets or films, as was observed inSEM images (Fig.4 A,B) as similar micrographs done by several researchers 35, 36, the GO sheets have athickness between 20 nm and 23 nm. This thickness of a single GO layer is about0.

61 nm 37, it indicates that the sample consists mostly of few layersgraphene nanosheets. The presence of black curly lines in CS/GO indicated thatthe GO sheets had been dispersed homogeneously in the CS matrix (Fig.4 C,D),and no aggregation of GO was observed.

Moreover, the presence of PPy within thenanocomposite can be confirmed by the dark portion that appears on thespherical shape (Fig.4 E,F). Both PY and carbon have similar characters,pyrrole has an SP2 bond character which is identical to the bands ofcarbons, It can be noticed that majority of CS/GO sheets are covered with polypyrrole(spherical cluster structure). The large contact area of CS/GO sheets andpolypyrrole in the polymer composite resulted in a more uniform compositestructure. The SEM and TEM analyses are in good agreement with FT-IR and XRDresults of polymer composite, confirming a strong interaction betweenpolypyrrole and CS/GO to form PPC/GO nanocomposites.


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