This is to declare that the thesis entitled "Fabrication of Polyaniline-Based Nanomaterials for Application in Energy Harvesting and Sensing Devices" has been submitted by me to the Indian Institute of Technology Guwahati for the award of the degree of Doctor of Philosophy. The fourth major contribution of the thesis is the preparation of hierarchically ordered polyaniline (PANI) nanorods in the presence of anionic (sodium dodecyl sulfate, SDS) and nonionic surfactant (pluronic F127) as the SDAs.
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List of Acronyms
List of Symbols
Introduction
Examples of CPs are polypyrrole, polythiophene, polyacetylene, poly(paraphenylene), poly(phenylene-vinylene), poly(thienylene), poly(furylene-vinylene), polypyridine, poly(fluorene), poly(indole), poly( diphenylamine), and polyaniline etc. The electrical properties of CPs can be tuned to facilitate different conductivity and redox properties.
Preparation of PANI nanomaterials
Schematic illustration of oxidation states of PANI, protonated form of emeraldine salt, neutral form of emeraldine base and fully oxidized state of pernigraniline. The acid-doped emeraldine salt form of PANI is only electrically conductive among the three types due to the presence of organic counterions (X-), which retain both oxidized and reduced forms of iminium and amine nitrogen groups, respectively [5].
Application of PANI nanomaterials
These hybrid materials include a multitude of uses such as in catalysis, wear resistance or solid lubrication, and in energy storage applications. One of the vital uses of CPs is in sensing and energy storage devices (batteries and supercapacitors), although they offer poor cyclic stability.
Supercapacitors
The Brian Evans Conway declared a new idea of charge disturbance, based on redox reactions at the electrode region, and named as "pseudocapacitor." The first pseudocapacitor was developed using the RuO2 film as electrode material with excellent performance in terms of long cyclic stability and reversibility [27]. The presence of carbon nanotubes or graphene will increase the storage performance of the electrode material.
Biosensors
Mainly, receptor molecules are analyzed at the recognition element, which controls the sensitivity and selectivity of the sensors. The primary use of biosensors is the detection of biomolecules that can be either a disease symptom or drug target.
Motivations and objectives 1. Motivations
- Objectives
Organization of thesis
Introduction
The resulting nanocomposite showed an excellent electrocatalytic behavior with increased capacity retention, which is attributed to the specific structure of the composite together with a cooperative effect of MoS2 and PANI. In this work, we demonstrate that two-dimensional nanosheet PANI nanocomposites (ie, MoS2 and graphene) would be an excellent candidate for use as a supercapacitor with a cycling stability of ~98%.
Experimental section 1. Materials
- Synthesis of chemically exfoliated graphene and MoS 2 nanosheets
- Synthesis of PANI, PANI-G and PANI-G-MoS 2 nanocomposites
- Materials characterization and measurements
Schematic diagram of the experimental method: (a) binary nanocomposites of PANI and graphene, (b) ternary nanocomposite of PANI, graphene and MoS2. Micro Raman spectra of the nanocomposites were recorded using a Horiba Jobin Vyon, Model LabRam HR with an excitation wavelength of 514 nm.
Results and discussions
- Materials structure and morphology
- Electrochemical analysis
Three electrode measurements of all samples. a) Cyclic voltammograms (CV) at a scan rate of 50 mV s-1, (b) specific capacitance (Cs) as a function of scan rate, (c) galvanostatic charge/discharge (GCD) at a current density of 1.4 A g-1, and (d) specific capacitance at different current densities from 0.2 to 2.0 A g-1. Two electrode measurements of PANI-G-MoS2. a) CV profile at different scan rates, (b) Cs as a function of scan rate, (c) galvanostatic charge/discharge (GCD) behavior at different current densities, the inset shows an equivalent series resistance (ESR ) and (d ) Cs at different current densities from 0.98 to 1.37 A g-1.
Conclusions
Chapter 3 Graphene-based PANI/MnO2 nanocomposites with improved dielectric properties for high energy density materials.
Introduction
A higher amount of CNT has enabled the nanocomposite to cross the barrier height of an insulating region of PANI with a conductivity percolation threshold of ~1%. The degree of improvement of various properties of the nanocomposites strongly depends on the interaction of PANI with the nanofillers. In this nanocomposite, BF nanoparticles are essentially functionalized with RGO, which in turn facilitates the formation of the nanocomposites.
Materials and methods .1 Materials
- Synthesis of GO and RGO
- Synthesis of PANI-GO and PANI-RGO binary nanocomposites
- Synthesis of PANI-GO-MnO 2 and PANI-RGO-MnO 2 ternary nanocomposites To prepare ternary composites, we first prepared MnO 2 by following the reduction method
- Characterization
A further 50 ml of DI water was added and the mixture was stirred at 450 rpm for another three hours. The above RGO-MnO suspension was transferred to an ice bath and an aniline solution (6.0 mL aniline in 40 mL 1.0 M HCl) was slowly added. After approximately 30 minutes, a solution of 2.0 g of APS in 40 mL of 1 M HCl was added to the above mixture to ensure complete polymerization.
Results and discussion
- Structures and morphologies
- Thermal stability
- Electron spin resonance analysis
- Electrical conductivity
- Dielectric and electrostatic properties
However, the ternary nanocomposite of PANI, RGO and MnO2 (Figure 3.4d) exhibits a significantly different surface structure, compared to PANI-GO-MnO2. We observed that the average size of the PANI-RGO-MnO2 nanorod is slightly deviated from the FESEM image (Figure 3.4d). The increased electrical conductivity of PANI-RGO-MnO2 is attributed to the uniform shape of the nanorods (see Figure 3.4d) that facilitates easy charge transport.
Conclusion
In the binary nanocomposites (PANI-GO and PANI-RGO) the skin effect is significantly less with a low impedance due to the significant charge localization. Therefore, PANI-RGO-MnO2 will be suitable in the applications for high frequency absorption as stealth materials. The remarkable properties of PANI-RGO-MnO2 are attributed to the well-dispersed hexagonal nanorods, which facilitate easy charge transfer and improve the dielectric property.
Introduction
38] have reported that the PA6/graphene nanocomposite exhibited good electrical conductivity with superior surface capacitance. It has been reported that nanocomposites based on PA6 and PANI possess remarkable conductivity that can be applied in energy storage devices as PA6 has helped to improve the specific permittivity. The excellent energy storage behavior is attributed to the synergistic effect of all three components present in the nanocomposite.
Experimental section 1. Materials
- Synthesis of rGO
- Synthesis of rGO/PANI nanocomposite
- Synthesis of PA6/PANI and PA6/rGO/PANI nanocomposites
- Characterization
- Electrochemical measurements of symmetric supercapacitor
- Structure and morphology
- Thermal stability
- Electron paramagnetic resonance (EPR) analysis
- I-V characteristics
- Dielectric and electrostatic properties
- Electrochemical analysis
The FETEM micrograph (Figure 4.3b) shows the symmetrical distribution of the "flower-shaped" morphology of the PA6/rGO/PANI 1:2 nanocomposite. Dielectric and electrical properties versus frequency of nanocomposites (a) dielectric permittivity, (b) dielectric loss, (c) capacitance and (d) AC. Numerical values of solution resistance (Rs), charge transfer resistance (Rct), correction factor (n) and relaxation time (𝝉𝟎) of nanocomposites.
Conclusions
The modest Rct value of PA6/rGO/PANI 1:2 is attributed to excellent electrical conductivity. A Ragone plot (e.g., ED vs. PD) is attributed to the CCD efficiency of a symmetric supercapacitor based on PA6/rGO/PANI 1:2 (Figure 4.18c). Thus, it is evaluated that the PA6/rGO/PANI 1:2 nanocomposite appears to be a potential electrode material for electrochemical energy storage applications.
Introduction
Herein, we report the fabrication of SSC-based tandem supercapacitor using PANI-RGO-ZnO ternary nanocomposite for significant energy storage applications. Among all nanocomposites, PANI-RGO-ZnO 2:1 (PANI:ZnO) appears to be the most suitable electrode material for energy storage devices with distinctive properties such as high electron conduction, high specific capacitance, and remarkable energy density. We have demonstrated several applications (two terminals as well as tandem devices) based on PANI-RGO-ZnO 2:1 nanocomposites.
Experimental section 1. Materials
- Synthesis of PANI-RGO-ZnO derivatives
- Characterization
- Fabrication and electrochemical measurements of the symmetric supercapacitor The working electrodes for three-electrode system were prepared by the active electrode
Furthermore, 30 ml of ammonia solution was mixed dropwise under stirring (450 rpm) at 70 ºC for 2 hours in the above solution. As shown in Figure 5.1a, first a homogeneous dispersion of 20 mg RGO and 3 ml aniline in a 40 ml DI water was prepared. A separate solution of 3 g of APS in 10 ml of 1 M HCl was prepared and added dropwise to the above solution under stirring at 300 rpm in an ice bath for 6 hours.
Results and discussion
- Structures and morphologies
- Thermal stability
- Brunauer, Emmett, and Teller (BET) measurements
- Electrochemical measurements
Furthermore, the nanocomposites were found in a hierarchical order due to a 'nanopetal-shaped' structure of ZnO (Figure 5.6a). The morphologies of ZnO and PANI-RGO-ZnO are in good agreement with the work reported by Ghanbari and Moloudi [52 ]. Two-electrode measurements of the PANI-RGO-ZnO 2:1-based symmetric supercapacitor device: (a) CV profile at various scan rates, (b) cyclic charge-discharge (CCD) measurements at various current densities, (c) specific capacitance and columbian efficiency against current densities, and (d) cyclic stability analysis. The graph of capacitance (C”) versus frequency of the SSC device of PANI-RGO-ZnO 2:1.
Conclusions
Chapter-6 Growth of Polyaniline Heterostructural Layers by Thermal Vacuum Evaporation and Fabrication of Thin Film Capacitors. Dasmahapatra, Growth of Polyaniline Heterostructural Layers by Thermal Vacuum Evaporation and Fabrication of Thin Film Capacitors, J.
Introduction
36], using the pulsed excimer laser ablation (KrF) method, have successfully deposited a thin film of PANI with good electrical and structural properties. Most of the research work has explored the fabrication of single-layer thin films of either PANI-ES or PANI-EB for sensing applications. Fabricated thin film capacitors (on a glass substrate) show excellent charge transport properties attributed to the good storage permittivity and capacitance.
Experimental Section 1. Materials
- Synthesis of PANI-ES and PANI-EB
- Thin film deposition
- Characterization and measurements
In the vacuum evaporator, the distance between the substrate holder and the target was 21 cm; the size of the target holder was 27⨯12 mm2 with an inner diameter of 9 mm. The reflectance spectra of the thin film samples were measured with a dual beam UV/VIS/NIR spectrometer (PerkinElmer, Lambda 950) equipped with an integrating sphere in the wavelength range 200‒800 nm. AC conductivities, dielectric and electrostatic properties of the fabricated devices were investigated using impedance analyzer (IM7581, HIOKI) in the frequency range from 1 kHz to 200 kHz at room temperature.
Result and discussion
- Structure and morphology
- Ellipsometric analysis
- Fabrication of thin film capacitors
- Electrical and dielectric properties
- Electrostatic charge storage properties
Spectroscopic Ellipsometric analysis of ψ for (a) PANI-ES, (b) PANI-EB and (c) PANI-ES/PANI-EB thin films. The real function of dielectric permittivity (ε1) for (a) PANI-ES, (b) PANI-EB and (c) PANI-ES/PANI-EB thin films. Therefore, the PANI-EB surface revealed higher ɛ' compared to the PANI-ES/PANI-EB thin film.
Conclusion
The capacitors PANI-EB and PANI-ES/PANI-EB show a response at a higher decay of the electric field. A thin layer of PANI-EB requires a higher threshold for the polarization of electrostatic charge carriers due to the non-conductive phase. Dasmahapatra, Mixed surfactant synthesis of hierarchical PANI nanorods for an enzymatic glucose biosensor, ACS Appl.
Introduction
This work reports the preparation of PANI-SDS-F127 nanocomposite via the in-situ polymerization method of aniline monomers in the presence of aqueous solution of SDS and F127 (mixed surfactants such as SDA). We have observed that the morphology of the resultant compounds strongly depends on the PANI:F127 ratio. For the 1:1 ratio composition of PANI:F127, we have observed the formation of nanowires with extremely high electrical properties, suitable for sensory application.
Experimental 1. Materials
- Synthesis of polyaniline and its functionalized derivatives
- Characterization and measurement
- Electrode fabrication for electrochemical measurements
- Structure and morphology
- Thermal analysis
- Electrical and dielectric properties
The FESEM image of the PANI-SDS-F127 at 1:0.6 ratio shows (Figure 8.7a) rod-shaped mesoporous structure with an average diameter of 473 nm. FESEM micrograph (Figure 7.9a) of the PANI-SDS-F127 at 1:0.9 ratio is due to the swollen nature of PANI backbone chain, at an increased weight of F127. The overall maximum 37% mass loss of the samples was recorded by the differential thermogravimetric (DTG) analysis in the range of 250-285 °C (Figure 7.10d).
