Influence of Dodecylbenzene Sulfonic Acid Doping on Structural, Morphological, Electrical and Optical Properties on Polypyrrole/3C-SiC Nanocomposites

Dodecylbenzene sulfonic acid (DBSA) doped nanocomposites of Polypyrrole-silicon carbide (PPy-SiC) were synthesized via insitu chemical oxidation polymerization of Pyrrole act as monomer. Dodecylbenzene sulfonic acid and Iron (III) chloride were used as a dopant and oxidization agent, respectively. The molar ratio of monomer unit to oxidization agent was 1:2.4. These nanocomposites were characterized for their structure, thermal stability, surface morphology and DC electrical conductivity by UV-Visible spectroscopy, FT-IR, XRD, TGA, SEM and four-probe method respectively. The electrical property of chemically prepared Polypyrrole and Polypyrrole/SiC in aqueous solution was found to be strongly depending on doping material, oxidant and solvent. It obeys Ohm’s Law and convincing applies for battery technology and sensor applications. *Corresponding author: Sacchidanand Shrikrushna, Department of Applied Sciences, College of Engineering, Pune, Maharashtra, India, Tel: 02025507000; E-mail: shrivigraha@gmail.com Received July 27, 2015; Accepted September 05, 2015; Published October 01, 2015 Citation: Shrikrushna S, Kher JA, Kulkarni MV (2015) Influence of Dodecylbenzene Sulfonic Acid Doping on Structural, Morphological, Electrical and Optical Properties on Polypyrrole/3C-SiC Nanocomposites. J Nanomed Nanotechnol 6: 313. doi:10.4172/2157-7439.1000313 Copyright: © 2015 Shrikrushna SA, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Introduction
'Pyrrole Black' is readily obtained in its conducting form by chemical or electrochemical oxidation of Pyrrole. Chemical synthesis of Polypyrrole yields a conducting polymer that incorporates the anion as counter ion, which electrically neutralizes the partially charged polymer chain [1]. It has been noticed that the conductivity of Polypyrrole film is highly dependent on the nature of the anions in the polymerization solution. Silicon carbide (SiC) is a wide-band gap semiconductor material show signs of mechanical and electrical properties suitable for formulating devices for use in high temperature. Silicon carbide can subsist in many different crystal arrangements depending on growth conditions, a phenomenon called polytypism. Polytypism is an unusual case of polymorphism, in which the crystal structures between two polymorphs are at variance only in the way indistinguishable, two-dimensional layers of close-packed layers are heap. Early 1900s, conducting polymers reported as 'aniline black' and 'Pyrrole black' conducting polymers, on the other hand, differ greatly from these insulating polymers because, as their name suggests, they are intrinsically conducting [2]. The development of these polymers is largely due to the Conducting polymers can be easily synthesized by both chemical and electrochemical routes [3,4] and preparation of various polymers in both aqueous and non aqueous solutions has been reported [5]. In this work, synthesis, characterization of Dodecylbenzene sulfonic acid Doped Polypyrrole/3C-SiC nanocomposites and study of their thermal and electrical property studied.

Experimental Materials
Pyrrole monomer was double distilled before use. Silicon Carbide, Dodecylbenzene sulfonic acid (DBSA) were purchased from Sigma Aldrich and used as received. Distilled water was used for preparation of all aqueous solutions.

UV-VIS analysis
LABINDIA UV 3000. Operated at room temperature. PPy display absorption peak at 446 nm which are in support with literature values [6].

FT-IR analysis
Bruker FT-IR Spectrophotometer operated at room temperature in the normal IR region 4000-650 cm −1 and 4 cm −1 band resolutions was used for structural analysis [7].

X-ray diffraction analysis
The X-ray diffraction studies of the samples were done on a Rigaku X-ray Diffractometer with Cu-Kα (1.5418 A°) radiation operating at 30 kV and 20 mA. Scanning was carried out in the 2θ range from 10° to 80°at a scan speed of 2° per minute.

SEM analysis
SIGMA HV Field Emission-Scanning Electron Microscope (FE-SEM) was used for microstructure analysis. It was operated at back scattered electron image mode. Before observations, the samples were sputtered for 15 min. and mounted on an aluminum stub with conductive silver paint so that no gas in vacuum chamber.

Thermal gravimetric analysis
TGA analysis was performed by SDT Q600. The calorimeter cell was flushed with 100 mL min −1 of nitrogen. An aluminum pan was used as a reference. The runs were performed from room temperature to 1050°C with a heating rate of 10°C /min.

Electrical conductivity
DC electrical conductivity of samples was measured by standard four-probe technique at room temperature (25°C). Compressed pellets (Diameter-15 mm) of materials were made under hydraulic pressure of 10 tones by using Kimaya Engg. Hydraulic press. Figure 1 represents the UV-Vis spectra of PPy and PPy/SiC exhibit absorption peak at 326 nm and 330 nm respectively reveals π→π* transition in benzenoid rings of DBSA [8]. The band 520 nm is associated with the transition from the valence band to the antibonding polaron state. Figures 2 and 3 represents the FT-IR spectra of pure PPy and DBSA dope PPy/SiC nanocomposite respectively. The band at1558 cm −1 and a weak band at 1468 cm −1 are assigned to stretching vibration of C=C and C-C in the Pyrrole ring [9][10][11]. The absorption at 1284 cm −1 corresponds to C-H in plane deformation modes [12][13][14]. PPy shows characteristic C-N and C-H stretching vibration of Pyrrole at1159 cm −1 and 1031 cm −1 respectively in the infrared spectrum [13]. The band observed at 1004 cm −1 and 676 cm −1 maybe recognized to the out of plane ring deformation and to the N-H vibrations in polymer [13]. The band at 2907 cm -1 , 1558 cm -1 , 1159 cm -1 , is assigned to C-H stretch (strong), N-H bending vibration of C=C and C-C in the Pyrrole ring, C-N stretch, confirming the Polypyrrole formation [15]. Frequencies and their assignment of DBSA doped PPy-SiC nanocomposite is described in Table 1.

X-ray diffraction (XRD) analysis
The XRD patterns of the PPy sample are shown in Figure 4. The   PPy-SiC and DBSA dope PPy-SiC nanocomposites shows exceptionally higher crystalline compared to the undope samples Figures 5 and 6. X-ray diffraction studies show that the Polypyrrole powder is amorphous in nature. Figure 5 indicate that the pure Polypyrrole broad peak presented by peak 2θ = 20.530 is due to PPy existence [16,17].
The crystal planes spacing is calculated using the Bragg's equation nλ=2dsin θ, where n is an integer determined by the order given, λ is the wavelength of the Cu Kα radiation source (λ) 1.5406 A°, and θ is the angle between the incident ray and the scattering planes [18]. The XRD patterns of the Silicon carbide nanoparticles in Polypyrrole matrix. Figure 6 can be seen clearly that the samples consist of crystalline phases presented by four main diffraction peaks at 2θ = 36.110, 42.290, 60.480, and 72.470 that correspond to the lattice planes (111), (200), (220), and (311). Dodecylbenzene sulfonic acid doped Polypyrrole silicon carbide composites shows similar but very sharp peaks hence uniformly distributed in polymer matrix ( Figure 6). The XRD patterns show that the silicon carbide is (3C-SiC) type and crystal structure of the sample is Face centered cubic was confirmed by JCPDS file no. 29-1129.

Scanning electron microscopy (SEM) analysis
Scanning electron micrograph of chemically synthesized Polypyrrole has shown mostly the growth in the bulbous porous form but changes due to dopant molecules. Typical SEM images of Polypyrrole are shown in Figures 7a and 7b. Each and every one SEM image shows a globular porous structure and it was observed that individual granules were nearly spherical and has a close packing [19]. It was shown that such spherulites are growing over the other and forming a continuous      Thermal Gravimetric Analysis (TGA) Figure 8 flaunts the thermal gravimetric analysis of PPY and DBSA doped PPY/SiC nanocomposite under O 2 atmospheres. It reveal that the thermal stability of DBSA doped PPY\SiC is much higher than that of PPy in the temperature range of 30-1050°C. Due to the evaporation of residual water molecules, nearly 10 wt% weight loss of PPY has occurred at 200°C while only 2 wt% weight losses for DBSA dope PPy/SiC nanocomposites. The main mass loss of PPy and PPy/ SiC nanocomposites starts at about 300°C corresponding to PPy degradation as the temperature elevate. Finally at 1050°C temperature, 80% weight loss of PPY is much more than DBSA doped PPY/SiC nanocomposites (40%).

DC conductivity measurements
The electrical conductivities of PPy, PPy/SiC and DBSA dope PPy/ SiC nanocomposites are determined using a Digital AC milivoltmeter four point probe resistivity measurement system. It is observed that the room temperature electrical conductivity of Polypyrrole is 4.5 S/ cm shown in Figure 9. PPy/SiC shows a conductivity of (28 S/cm) and DBSA doped PPy/SiC give high value of conductivity depend upon doping concentration [20]. Table 2 shows the variation of electrical conductivity (σ) with increasing doping concentration of DBSA into PPY/SiC measured at the slower rate according to the standard four point probe method at room temperature.

Conclusions
In summary, we were able to prepare PPy, PPy/SiC and DBSA dope PPy/SiC nanocomposite particles by direct oxidation of Pyrrole with unhydrous ferric chloride by insitu-chemical polymerization. The processability of Polypyrrole/silicon carbide composites improved with increasing content of dopant. The UV-Vis absorption spectra showed π→π* transition in benzenoid rings of DBSA. FTIR study confirmed the presence of dopant in the composite structure. The fine and sharp XRD peaks were observed after doping with DBSA. The particle size distribution of PPy, PPy/SiC and DBSA doped PPY/SiC composites were found at 67-276 nm. The SEM study showed the granular morphology and aggregation of particles with higher concentration of dopant. It was observed that the conductivity of Polypyrrole composite increases with increasing wt% of SiC as well as molar concentration of DBSA and IV analysis gives linear pitch curve. The results suggest that the PPY/SiC prepared in the presence of DBSA has ohmic conducting property and better thermal stability.