Synthesis, characterisation and potential applications of polyaniline/chitosan‐Ag‐nano‐biocomposite

Abstract

Biodegradable polymers have greatly promoted the development of environmental, biomedical and allied sciences because of their biocompatibility and doping chemistry. The emergence of nanotechnology has envisaged greater options for the development of biodegradable materials. Polyaniline grafted chitosan (i.e. biodegradable PANI) copolymer was prepared by the chemical in situ polymerisation of aniline using ammonium per sulphate as initiator while Ag nanoparticle were synthesised by chemical reduction method and incorporated in to the polymer matrix. The as prepared materials were characterised by X‐ray diffraction, Fourier transform Infra‐red spectroscopy, transmission electron microscopy, energy dispersive X‐ray analysis. Moreover energy storage capacity, impedance properties were also studied. The main focus was on the photocatalytic degradation of organic dyes to remove the toxic and carcinogenic pollutants. This polymer nano‐biocomposite has multifold applications and can be used as excellent materials for enhanced photodegradation and removal of toxic contaminants from waste waters and natural water streams. In addition, the biocompatible materials with excellent mechanical properties and low toxicity can also be used for tissue engineering, drug delivery and electrical energy storage devices.

1 Introduction

Biodegradable polymers are defined as macromolecules in which the primary degradation mechanism is through the action and metabolism of microorganisms [1]. In general, biodegradable polymer materials are degraded into biomass, carbon dioxide and/or methane. Thus, the macromolecular backbone suffers breakdown and is used as a source of carbon and energy. A major forefront for the application of biodegradable polymers is in medical science, environmental, electrical and electronic fields as well as nanotechnology. In addition they are used as temporary substitutes for natural tissues and degrade in vivo over a predetermined period of time generating safe end products. However, they can also be used as sensors, smart materials, energy storage devices and photocatalyst [2]. Biodegradable polymers with conducting properties are similar to those of metals and inorganic semiconductors with improved electric/heat conductivity and enhanced mechanical properties can be used as electrical and electronic sensors [3, 4, 5, 6]. Among the wide range of conducting polymers such as polyaniline (PANI), polythiophene, polyhydroxyalkanoates, polyfuran etc., are of particular interest because of its ease of availability, environmental stability and doping chemistry [7, 8].

Traditionally, PANI because of its ease of availability and low cost it has been successfully utilised by forming blends and composites with a conventional polymer. It has great advantage in processing and combining the mechanical properties of the conventional polymer and the functional properties of PANI [9]. The most straight forward approaches towards processing polymers include fabricating the composites to films, hydrogels microsphere and fibres [10]. However, high‐environmental stability with low biodegradability gives rise to bioaccumulation of PANI or Ppy which is not sustainable [4, 11, 12]. Hence there is an urgent need to develop conducting biodegradable polymers by incorporating a matrix of natural biodegradable polymers such as chitosan, gelatin, collagen or cellulose [13, 14].

Polymer nano‐composite is basically a hybridisation process between polymer matrices and nanoparticle with an intention to integrate their properties such as lightweight, cost‐effectiveness ease of processing, excellent biodegradability and biocompatibility, increased electrical conductivity and enhanced mechanical properties [3, 4, 5, 6]. These biocompatible polymers found use in almost number of fields such as tissue engineering, drug delivery, artificial skin, sensors etc. [15, 16]. They can be also used as sensors for both detection of gases as well as for liquid. Electricity generation is also possible by using the composites through a photoelectrochemical fuel cell using photocatalysis process. Metal nanoparticles such as silver (Ag) have excellent electrical conductivity and antibacterial activity. However, due to inferior mechanical properties, poor processability and hydrophobicity its applications are getting limited.

This research aims to synthesise polymer nanocomposites by using a conducting PANI with doping of Ag nanoparticles to enhance the activity and conductivity of that matrix and further this matrix has been added to biopolymer so that it could be degrade to some extent to reduce any burden on environment. These polymer bionanocomposites have been used further the degradation of dyes. As some organic dyes which cannot degrade in the industry are discharges into water bodies, these dyes being toxic and carcinogenic in nature leads to health hazards of human being as well as aquatic species. The photocatalytic activity of conducting polymer nanocomposites for degradation of dye have been evaluated through mineralisation process which degrade dye into CO₂ and H₂ O by using visible light as a source of energy [17]. The synthesised chitosan grafted PANI biodegradable polymers and thereafter incorporating Ag NPs into the biodegradable polymer chains followed by their characterisation through Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X‐ray diffraction (XRD), UV visible. The biodegradability claim of the polymers were also tested and confirmed. The work further involves measurement of impedance properties, capacitance and photocatalytic activity of materials in removing toxic pollutants along with process optimisation. The paper further explores the kinetics of photodegradation of toxic dyes in presence of as prepared materials and the effect of pH on photodegradation.

2 Material and methods

2.1 Chemicals

All the reagents were of analytical grade and supplied by Fisher Scientific, India. Chitosan, Silver nitrate, Hydrazinium hydrate, CTAB (hexadecyl‐trimethyl ammonium bromide) surfactant, ammonium per sulphate and hydrochloric acid were used as received. However, aniline was distilled prior to its in situ polymerisation.

2.2 Synthesis of PANI‐Chitosan biodegradable polymer

Biodegradable PANI was be prepared by using chemical copolymerisation technique in accordance with Hosseini et al. [18] Briefly, 0.4 g chitosan was added to 20 ml of distilled aniline (0.2 M) in a round bottom flask kept over ice bath at (0–5°C). Later, 0.1 M Ammonium persulphate was added drop wise under constant stirring to get good yield. The stirring will be continued for a further period of 12 h until the mixture becomes black. The precipitate thus obtained was collected by centrifugation and washed thoroughly with distilled water. Dried at 40°C for 24 h under vacuum, a green black powder was obtained. The complete reaction sequence followed by stirring for another is presented in Fig. 1.

Fig. 1.

Reaction scheme for the preparation of chitosan grafted PANI in the present work

2.3 Synthesis of Ag NPs based biodegradable and conducting nano‐biocomposite

Ag NPs were prepared by chemical reduction method by appropriately mixing hydrazinium hydroxide solution (100 mm, 0.5 ml) with AgNO₃ solution (50 mm, 0.5 ml) and adding CTAB (hexadecyl‐trimethyl ammonium bromide) as surface active agent (1 mM, 20 ml) in sequence and then reaction mixture was stirred for another 10 min at 30°C [19].

For the synthesis of polymer nano‐biocomposite, Ag nanodispersions were added to aniline solution containing chitosan (0.4 g) prior to its in situ chemical polymerisation followed by drop wise addition of ammonium per sulphate under constant stirring. The precipitates was finally separated by centrifugation and thoroughly washed with distilled water and dried as described above.

2.4 Characterisation

The crystal structure and particle size of the pure Ag NPs and PANI/Chitosan/Ag nano‐biocomposite materials were determined by powder XRD (Phillips PW1729) with Cu Kα radiations. The average crystallite size of nano‐biocomposites was calculated from the diffraction peaks using Debye–Scherer's formula [4, 20] as given in the following equation:

$$d=\frac{0.9\lambda }{\beta \mathrm{Cos}\theta }$$

where d is the average crystallite size, λ is the X‐ray wavelength, β is the broadening of the diffraction peak at half maximum and θ is the diffraction angle. The morphological and elemental composition of the as prepared biodegradable and conducting materials was studied with the help of scanning electron microscopy (Jeol JSM‐6360) coupled with energy dispersive x‐ray (EDX) analyser. Particle size and shape was also be confirmed by analysing the NPs with the TEM (Philips CM200). The functional group characterisation was done by using the ‘Interspec 2020‐Spectrolab UK, FTIR spectrometer.

2.5 Biodegradability assay

2.5.1 Bacterial culture

To test the biodegradability characteristics of nano‐biocomposite, the bacterial strains used in the present study was Gram positive Listeria monocytogene (Microbial Type Culture Collection and Gene Bank (MTCC)^® 657TM; MTCC, IMTECH, Chandigarh, India). L. monocytogene s was cultured in Brain Heart Infusion broth medium for 12–18 h at 37°C. L. monocytogenes is a gram positive, rod shaped, facultative anaerobic and food borne bacterium.

2.5.2 Biodegradability analysis of synthesised nano‐biocomposite

Biodegradability test was performed on the sterile glass cover slips (12 mm diameter and 0.11 mm thickness, HiMedia India Pvt. Ltd.) placed in six‐well cultured plates procured from Eppendorf India Limited. To evaluate the biodegradable characteristics of nano‐biocomposite, we prepared thin films nano‐biocomposite and placed on the cover slip in laboratory condition under perfect growth medium of food born bacteria. Further, 1 × 10³ bacterial cells suspended in the PBS pH 7.4 was further incubated on the film. The setup was incubated at 25°C temperature and studied periodically after 0, 7 and 14 days.

2.5.3 Determination of biodegradable nature of as synthesised nano‐biocomposite

Biodegradable nature of the nano‐biocomposite is determined by following the published protocol of Samzadeh‐Kermani et al. [21] with certain modification. The biodegradable nature of the nano‐biocomposite was determined by examining the loss of weight after exposing the sample with the microorganism for the stipulated time period. For this, fixed amount of nano‐biocomposite is dispensed in the culture micro‐vial for day 0, 1, 7 and 14 to observe the weight loss. The percentage weight loss of nano‐biocomposite is directly correlated with the biodegradation of the synthesised material.

$$\begin{array}{rl}& \mathrm{Biodegradation}\propto \text{\%}\mathrm{weight}\mathrm{loss}\\ & \text{\%}\mathrm{Weight}\mathrm{loss}=\frac{\mathrm{Change}\mathrm{in}\mathrm{weight}\mathrm{after}\mathrm{exposing}\mathrm{material}}{\mathrm{Initial}\mathrm{cumulative}\mathrm{weight}}\times 100\end{array}$$

2.6 Photodegradation experiments

The photodegradation of Ponceau BS in presence of the as‐prepared materials was studied in a visible‐photoreactor and the absorbance of an aqueous solution of Ponceau BS dye was measured under visible lamp (Power 500 W, Intensity 9500 Lumens). The absorbance of the dye was monitored at different time interval till equilibrium under visible light illumination in presence of as synthesised catalysts using a UV‐visible spectrophotometer (Shimadzu‐1601, Japan). Later, the absorbance values were used to calculate the unknown concentrations of azo‐dye with the help of a calibration curve with a correlation coefficient (R ²) of 0.99. Effect of pH was studied by modelling the photodegradation experiments at different pH ranging from acidic to basic values.

2.7 Energy storage properties

The energy storage potential of the nano‐biocomposite materials was tested by measuring the capacitance and resistance of the samples at variable temperatures ranging from 25 to 200°C. Capacitance and impedance measurements were performed by using computerised LCR Meter/Impedance analyser–Wayner Kerr. The powders were compressed at 6 tons to form pellets and coated with silver paste in order to enhance the electrical conductivity between the pellet and electrodes.

3 Results and discussions

3.1 XRD analysis

The XRD patterns of biodegradable PANI (i.e. chitosan grafted PANI) and biodegradable PANI/Ag (i.e. PANI/Chitosan/Ag) are shown in Fig. 2. It can be clearly seen in case of the PANI/chitosan blend that the XRD pattern shows nearly semi‐crystalline structure. The peaks centred at 2θ = 25.059° are ascribed to the periodicity parallel and perpendicular to the polymer chains [6, 22]. Presence of chitosan shifts the characteristic peak of PANI towards right and appeared at 30°. However, the peaks at 2θ = 35°, 45° and 65° with corresponding indices (111) (200) and (220), respectively, in the second spectrum match well with the planes of Ag which is confirm by the JCPDS (File no. 04‐0783 indicating the presence of Ag nanoparticle in the composite) pattern of Ag nanoparticle. Wang et al. 2008 [23] reported the reflection peak was indexed to face centred cubic Ag. Thus, the XRD pattern confirms the crystalline structure of Ag nanoparticle with the face centred cubic structure. The data show that after adding the Ag nanoparticle the peak shift to the lower side. The crystallite size of the Ag nanoparticle calculated from Sherer's formula and XRD peak data was found to be 34 nm.

Fig. 2.

X‐ray diffractograms of the as‐prepared materials (PANI/chitosan and PANI/chitosan/Ag)

3.2 Surface characterisation and elemental composition by SEM/EDX/TEM

The SEM micrographs show typical features of the biodegradable polymer nanocomposite (Fig. 3). Both micrographs are mainly composed of irregularly arranged granular flakes with sharp edges. The structure looks more porous and uniform. The microscopic image in Fig. 3 a light coloured chitosan mixed with dark coloured PANI chains. The Ag particles are embedded in to the PANI/chitosan matrix forming the core‐shell structure (Fig. 3 b) clearly show the dark coloured globular shape of Ag nanoparticle are clearly monodispersed in PANI/chitosan matrix as a result of the different electron penetrability.[24]. SEM Micrograph confirms the biodegradable polymer matrix is an excellent host matrix to avoid the aggregation of silver nanoparticle. The matrix further helps to form an encapsulation acting as good capping agent providing chemical and environmental stability as well. The size of Ag nanoparticle was <50 nm (as observed from SEM micrographs) and it is spherical in shape. EDX peaks show the presence of various elements (C, N, O, S and Cl). The elements C, H, O and N in Fig. 3 a confirms the presence of PANI [(C₆ H₅ NH‐)_n], and the presence of chitosan [(C₅ H₁₀ O₄ N‐)_n] while Ag show that of Ag nanocomposites Fig. 3 b. Interference of chloride ion confirms the usage of HCl as precursor.

Fig. 3.

SEM images, EDX spectra (inset) and weight per cent of different elements in the as prepared materials

(a) Biodegradable PANI, (b) Biodegradable PANI/Ag nano‐biocomposites

TEM images in Fig. 4 shows that the particle size of the as prepared materials is <50 nm (i.e. nano‐range). The Ag nanoparticles are uniformly distributed within the polymeric matrix. The structure gets denser upon the addition of Ag nanoparticle into the polymer matrix. Conversely, the microscopic image in Fig. 4 b represents the metallic (Ag) nanocomposites entrenched into the net like structure of PANI/chitosan matrix.

Fig. 4.

TEM images of

(a) PANI/chitosan, (b) PANI/chitosan/Ag nano‐biocomposites

3.3 Functional groups identification by FTIR

The FTIR spectra of (i) Pure PANI (ii) PANI/Chitosan (iii) PANI/Chitosan/Ag composites are shown in Fig. 5. It shows several characteristics peak corresponding to polyaniline including peaks at 1578 and 1492 cm⁻¹ for C = C stretching of benzenoid and quinoid ring structure. Bands at 1358 and 1320 cm⁻¹ refer to C―N stretching of secondary amine while the peak at 3480 cm⁻¹ is attributed to N‐H stretching mode (Fig. 5). Peaks at 2936 cm⁻¹ refers to cross‐linking mode of the polymer chains and the peaks at 1174–1158 cm⁻¹ corresponds to C―H bending mode [3, 25]. The characteristic broad band for O‐H group (in the presence of H band) of chitosan appears at 3429 cm⁻¹. The characteristic absorption band of pure chitosan (3429 cm⁻¹) and PANI (1584, 1492, 1314 and 795 cm⁻¹) have been both present in the spectrum of their blends PANI/chitosan. Upon comparing the relative intensity band around 3429 cm⁻¹, we also find that the band of the stretching vibration of ‐OH group in the composite is apparently weaker than the same band in pure natural polymer. Furthermore, the absorption peak at 3496 cm⁻¹ in the spectrum of pure chitosan is blue‐shifted to 3429 cm⁻¹ in the spectrum of the composite. These phenomena confirm that chitosan is successfully activated by superfluous acids. The intermolecular hydrogen bonds are broken and the more hydrogen groups become more accessible. The bands obtained in the range 400–600 cm⁻¹ are attributed to Ag nanoparticles without any organic moiety. The various peak positions are presented in Table 1

Fig. 5.

FTIR spectra of pure PANI, PANI/chitosan and PANI/chitosan/Ag

Table 1.

FTIR peak assignments for PANI, PANI/chitosan and PANI/chitosan/Ag

Peak assignment	Absorption frequency, cm−1
	PANI	PANI/chitosan	PANI/chitosan/Ag
quinoid ring	1578	1584	1616
benzenoid ring	1492	1463	1490
aromatic C‐N stretching	1358	1316	1320
N‐H stretching	3480	3482	3498
crosslinking	2936	2944	2940
C‐H bending	1174	1154	1158
Ag	—	—	400–600

3.4 Biodegradability assay

Biodegradability studies are very important to ensure the bioaccumulative potential of the material under investigation and to measure the extent of trouble the material may put on the environment if it is non‐biodegradable. Thus the primary objective behind this tests was to substantiate the claim that the as prepared polymer samples were biodegradable. After the stipulated time period (i.e. 0, 7 and 14 days) slides were observed under the bright field microscope (Zeiss, Axiocam Imager MRM M2 fluorescence microscope (Thornwood, NY US). The results of the microscopy showed that the food borne bacteria was prominently observed under the microscope on the thin film of nano‐biocomposite layer after 14 days as compared with other incubation time periods (i.e. 0 and 7 days). Bright field images demonstrated that the synthesised nano‐biocomposite supports the growth of food born bacteria as shown in Fig. 6.

Fig. 6.

Bright field images of biodegradable nano‐biocomposite films incubated with food borne bacteria for stipulated time periods

(a) 0 day, (b) 7 days and (c) 14 days

Arrow indicate the degradation of material sheet, clearance of the sheet represent the disintegration of the synthesised material by the microbial communities

Excessive growth of the microbial communities in polymeric medium over the test duration shows non‐toxicity and biodegradability of the polymer samples [26]. Our claim that the samples were biodegradable was verified by the clearance of the synthesised nano‐biocomposite sheet as represented by the arrows in the microscopic results. Thus, the synthesised materials (i.e. chitosan grafted PANI) are non‐toxic and biocompatible. Hence, they can be used safely for various fields without putting an extra burden on the environment [27].

3.5 Biodegradable property of nano‐biocomposite

The result of the biodegradation assay was confirmed the biodegradable and stable nature of the synthesised nano‐biocomposite as shown in Fig. 7. The biodegradation result showed the slow and sustained degradation for the extended period of time. Besides this, it was also observed that the rate of weight loss significantly elevated after day 5 and the explanation of this is that the processed components of the composite were further easily biologically degraded by the microorganisms.

Fig. 7.

Graph of percentage weight loss of nano‐biocomposite with time

3.6 Photodegradation and effect of pH

The photocatalytic efficiency of the materials was tested by studying the photodegradation of Poncaeu BS in presence of UV illuminating source in a quartz jacketed photoreactor. The removal of the dye was confirmed by scanning the UV spectra of the samples collected at every 10 min intervals during the experiment. The merged UV spectra are shown in Fig. 8. The diminishing peak intensities support the claim that the as‐prepared nano‐biocomposite was capable of degrading the azo‐dye. The effect of pH on the photocatalytic activity was also studied by varying the pH of the dye solution and monitoring the degradation rate correspondingly. It can be seen from Fig. 9 that pH has a significant effect on the photodegradation. The extent of degradation shows a negative correlation with pH, i.e. the higher the pH of the medium, lower will be the extent of degradation.

Fig. 8.

UV spectra of Ponceau BS under visible irradiation in presence of as‐prepared polymer nanocomposite (PANI/chitosan/Ag)

Fig. 9.

Effect of pH on photodegradation of Ponceau BS dye samples in presence of

(a) PANI/chitosan and (b) PANI/chitosan/Ag

In fact, there exists an electrostatic interaction between the catalyst surface and the dye molecules which consequently enhances or inhibits the photodegradation rate. The effect of pH value on photocatalysis is generally due to surface charge of the catalyst and the charge on dye molecules [28]. The change in pH shifts the redox potentials of the valence and conduction bands, which might alter the interfacial charge transfer [29, 30]. Acidic pH found to be more favourable for dye degradation. The surface of Ag is positively charged at low pH whereas; with rise in pH the surface becomes negatively charged. As PBS is a cationic dye, low‐pH favours the adsorption of dye molecule on the catalyst surface followed by its rapid cleavage which results in high degradation efficiency. The degradation rate was higher in acidic conditions with its maxima at pH 3.

3.7 Kinetics of photodegradation

After optimising the reactor pH, kinetics of photodegradation of the dye was studied at optimised pH value (i.e. pH 3). The results of kinetic studies were presented in Fig. 10.

Fig. 10.

Kinetics of photodegradation‐ Residual concentrations of Ponceau BS dye during photodegradation experiments (optimum pH of 3.0 was maintained)

The fractional residual dye concentrations (C /C ₀) was plotted against time (min) and the straight line plots between C /C ₀ and time (t) show that the first order kinetics has been followed (Fig. 10)

$$\frac{C}{C_0}={\mathrm{e}}^{-kt}$$ (1)

$$\ln \left[\frac{C}{C_0}\right]=-kt$$ (2)

where C ₀ is the initial concentration and C is the concentration at any time (t), however, k is rate constant in min⁻¹. The experiment shows high degradation rate in both the cases (i.e. PANI/chitosan and PANI/chitosan/Ag) with slightly higher rate in case of polymer samples only. The rate of dye degradation decreases by incorporating Ag nanoparticle due to decreased charge separation and enhanced charge recombination rates [31]. Thus, the materials can be successfully used for removing toxic and complex dyes from aqueous media and hence can be employed for the treatment of contaminated water.

3.8 Electrical properties (energy storage potential)

The degree to which an object conducts electricity or the ability of compound to have free electrons to conduct electricity calculated as the ratio of the current which flows to the potential difference present. This is the reciprocal of the resistance, and is measured in Siemens or mhos. However, the electric properties are very sensitive to several factors such as the method of preparation, concentration of solution, chemical composition and temperature [32, 33]. For the investigation of ionic conductivity, impedance spectroscopy is very important tool. This technique is quite useful for the separation of resistive and capacitive components of the electrical parameter [34]. To show the electrical properties of materials, the real impedance Z ′ (i.e. Z Cosθ) is plotted against as function of temperature at a frequency of 75.00 MHz. It is clear that the Z ′ of the polymer samples is significantly less upon the addition of non‐conducting natural polymer (chitosan) in to the conducting PANI chains. The chitosan molecules act as a barrier in the flow of electron by breaking the conjugation resulting in to lower conductivity. The impedance analysis of biodegradable polyaniline and biodegradable polyaniline doped Ag can be studied over a wide range of temperature. It can be studied with the phenomena of bulk material and grain boundary [35]. Generally the grains are effective in high‐frequency region and grain boundaries are effective in low‐frequency region. In polyaniline chitosan sample grain boundaries is maximum and that cause electron flow easily minimise the resistance whereas in case of doping of nanoparticle cause grain size decreases and that causes resistivity increase [36]. Smaller grain sizes imply smaller grain‐grain surface contact area and therefore reduce electron flow. It is clear from Fig. 11 Ag doped biodegradable polyaniline have high‐impedance value resulting high resistivity as compared with biodegradable PANI.

Fig. 11.

Plots showing the real component of impedance of as‐prepared materials as a function of temperature (25–200°C) at frequency of 75.00 MHz

Capacitance on the other hand, measured in farad or micro farad (F or μF) is the ability of physical structure to accumulate electrical free charge under certain voltage and thus act as a carrier for energy. These electrons start flowing when a potential difference is created to generate electrical energy. Any material which is electrically charged exhibits capacitance and the materials with a large capacitance hold more electric charges at a given voltage, than those with low capacitance.

The capacitor's ability to store this electrical charge (Q) between its plates is proportional to the applied voltage, V for a capacitor of known capacitance in farads, F. Capacitance C is always positive and never negative. The greater the applied voltage the greater will be the charge stored on the plates of the capacitor. Likewise, the smaller the applied voltage, smaller will be the charge. Therefore, the actual charge Q on the plates of the capacitor and can be calculated by the relation:

$$Q=C\cdot V$$ (3)

where Q is the charge in coulombs, C is capacitance in farad and V is voltage in volt. There are three basic factors of capacitor that determines the amount of capacitance created by a system namely plate area, plate spacing and dielectric materials.

As can be clearly seen from Fig. 12, capacitance increases as we dope Ag nanoparticle in to the biodegradable polymer nanocomposite.

Fig. 12.

Variation of electrical capacitance (energy storage) of the as‐prepared materials over the temperature range 25–200°C at frequency of 75.00 MHz

Capacitance, on doping silver nanoparticle increases because silver provide some more electron to the composites which results in the leading of charge storage capacity. The electrically conducting and biodegradable polymers can be used to store energy and power scientific devices at remote locations such as in space craft, oceans, deserts etc. The as prepared materials can also be used to power pace makers or artificial tissues within the body.

Moreover, dielectric permittivity is another important property which is a direct measure of a material's capability to store electrical energy when placed in an electric field. The performance of dielectric constant depends on both frequency and temperature [37]. Fig. 13 shows the dielectric properties of the materials as a function of temperature at a specified frequency of 75.00 MHz.

Fig. 13.

Dielectric constant versus temperature graph showing the energy storage capacity of prepared biodegradable and conducting nano‐biocomposite

It is clearly evident from Fig. 13 that Ag doped biodegradable polymers possess significantly high energy storage and dielectric properties. Thus, in addition to excellent electrical capacitance, the nano‐biocomposite possess superior dielectric properties and can be successfully used in energy storage.

4 Conclusions

Biodegradable and conducting polymers were prepared by incorporating natural polymer (chitosan) and Ag NPs in to polyaniline chains. The materials thus obtained were found to possess superior electrical conductivity and high photocatalytic activity against organic dye pollutants. The electrical capacitance and dielectric permittivity of the materials was also tested to ensure if the materials can store energy and used for powering scientific devices in remote locations. The materials show good capacitance properties. Biodegradability tests were carried out to verify the claim of producing biodegradable polymers by allowing microbial communities to grow on the as prepared polymer as sole substrate for up to 21 days. A significant growth of microbial communities shows that the samples were biodegradable. The photodegradation of the Ponceau BS dye follows pseudo first order kinetic model. The photodegradation was a pH dependent response and high removal rates were obtained at low pH. Thus, chemical in situ polymerisation can be used for synthesising natural polymer‐based biodegradable as well as conducting nano‐biocomposite for application in various fields including wastewater treatment.