Situ synthesis and characterization of polypyrrole/ZnO Nanocomposites for optical and photocatalytic activity

In situ polymerisation process used for manufacturing polypyrrole (PPy) nanoparticle-reinforced various doping concentration of zinc oxide (ZnO NPs) nanocomposites. Fourier transform infrared(FTIR), Scanning electron microscopy(SEM), Photo luminescence (PL) and UV-vis spectroscopy was used to characterise the polymer nanocomposite. The ZnO nanoparticles are distributed throughout PPy matrix as shown in the SEM pictures of the nanocomposites. Distinctive peaks of Pure PPy and metal oxide bond of ZnO are as displayed in the FTIR spectra. Optical property of PPy, ZnO and PPy/ZnO was studied by using PL and UV-DRs spectrophotometer. These outcomes demonstrated that the synthesised PZ30 nanoparticles could potentially use in the treatment of wastewater.

Pollutants in water cause serious ecological issues for every living organism.The main contributors to pollution are synthetic organic compounds, which include dyes produced by a variety of industries, including pigment, cosmetics, paper, plastic, skin, leather, photography, food, and medicines, among others.Highly poisonous and possibly cancer-causing dyes have been connected to a number of human and animal disorders [1][2][3].Associated with textile dyes are allergenic to skin conditions and problems with the central neurological system.These problems may originate from the inactivation of the enzymes due to cofactor replacement [4,5].When ingested or inhaled, textile dyes can irritate the skin and eyes, especially if they have been exposed to dust [6,7].The aromatic structure of dyes increases their resistance to deterioration in the presence of the environment.Because pollution has significantly increased, worldwide environmental standards are growing stricter to cut pollution, and technology to remove dyes has been progressing [8,9].One of the popular methods to remove contaminants in water is photocatalytic degradation (PCD) [10,11].Photocatalysts are the best materials for converting solar energy for use in oxidation and reduction processes.Photocatalysts are used in a variety of processes, including as removing impurities from water and the air, splitting water to create H2, controlling Oduors, inactivating bacteria and cancer cells, and managing odors [12][13][14].
Due to its potential to remove hazardous and harmful substances from the environment, photocatalyst materials have gained significant research during the past 10 years [15,16].There is a great deal of promise for the removal of hazardous substances with semiconductor photocatalysts.Because of recent developments in its synthesis and its distinct optoelectronic, catalytic, and photochemical capabilities, zinc oxide (ZnO), that has a broad band gap of 3.2 eV, has attracted a large amount of interest [17].Photocatalysts cause the generation of reactive oxygen, which helps in the decomposition of contaminants.Incorporating two photocatalysts with various bandgaps leads to a greater separation of electron/hole pairs, where more species would exist for reactions to degrade contaminants.
In this study, the PPy/ZnO NPs were synthesized by insitu polymerisation method.Synthesized nanocomposites were characterized by FTIR, SEM with EDX, UV-Vis and PL.This study evaluated visible light using PPy/ZnO nanocomposites as a catalyst.

Synthesis of PPy
Chemical oxidative polymerization was employed to synthesize PPy using the pyrrole (C4H5N) monomer.As an oxidising agent, ammonium per-sulphate of analytical grade (APS, (NH4)2S2O8) was used.A 1:1 volume ratio of 0.1M aqueous solution of pyrrole and 0.1M of APS was used to carry out the chemical polymerization in a beaker.The polymerization process took place at room temperature for 4 hours.Black precipitate was produced after the polymerization process ended.To get rid of any potential oligomers, the precipitate was filtered, repeatedly washed with distilled water, and then dried for six hours at 60°C.

Synthesis of ZnO NPs
ZnO nanoparticles (NPs) were created using the co-precipitation technique.To prepare ZnO, 0.04M solution of Zn(NO3)26H2O (2.97g/250ml) was stirred continuously while sodium hydroxide solution (4M) was gradually added.White precipitate was obtained at pH 11, then filtered and was dried at room temperature after being rinsed with ethanol/DI water.In order to create ZnO NPs, the precipitate was ultimately heated to 450°C for three hours in a muffle furnace (heating rate: 5°C min-1).

Synthesis of PPy/ZnO Nanocomposite
Pyrrole is dissolved in water at 0.1M was mixed with the necessary weight percent of ZnO NPs (15, 30, and 45%), and this mixture was added to the monomer solution to begin the chemical polymerization process.Drop wise addition of 0.1M of APS in a volume-to-volume ratio of 1:1.The polymerization took place for 4 hours at the ambient temperature.The result of the polymerization process was the formation of the black precipitate.To create the PPy/ZnO nanocomposite and remove any possible oligomers, the precipitate was filtered and washed multiple times in distilled water.It was dried for six hours at 60 °C.

Characterization
Using a JASCO FTIR 6800, FTIR spectrometer in the range from 400 to 4000 cm -1 was used measuring the functional group of the PPy/Zno.SEM analysis was used to analyse the morphological investigations (Neo-Scope JCM-6000 PLUS system).UV spectroscopy was used to analyse the absorption spectra for the presence of functional groups (DS5Graphic_RGB-1024x667), and double excitation and emission monochromator photoluminescence spectrometer (FLS1000) was used to detect the PPy/Zno photoluminescence.

Fourier Transform Infrared Spectrometer (FTIR)
The FTIR spectra of pure PPy, ZnO nanoparticles, and PPy/ZnO nanoparticle composites loaded with varying ZnO contents are displayed in Figure 2. From spectra it is observed that, the FTIR spectrum of synthesized nanoparticle in the range of 400 -4000 cm -1 the stretching mode of ZnO appears at around 433 cm -1 ( Figure 2 ) .The synthesis of PPy was confirmed by the spectra of bulk PPy, as illustrated in Figure 2. Bands at 1556 cm - 1 and 1480 cm -1 , respectively, are responsible for the weak band's and C=C and C-C's stretching vibration in the pyrrole ring [18].At 1182 cm -1 and 1051 cm -1 in the IR spectrum, respectively, PPy displays the usual C-N and C-H stretching vibration of pyrrole.The peak at 1030 cm -1 is the result of PPy being absorbed by N-H in-plane deformation.The band found at 917 cm -1 and 602 cm -1 may be caused by the N-H vibration in polymers and the out-of-plane ring deformation.

3.UV-DRS Analysis
UV-DRS spectra was used to determine the band-gap of synthesized nanoparticles.As shown in Figure 3, maximum reflectance of PPy, ZnO, 15PZ, 30PZ, and 45PZ nanocomposites was 395nm, 380 nm, 375 nm 345nm and 366 nm respectivly.The equation ( 3) was used to determine the energy band gap (Eg) of the PPy, ZnO and nanocomposites of PPy/ ZnO from the Tauc's plot, to get (αhν) 2 vs hν graphs, In this case, the index n relies on the kind of electronic transitions, the photon's energy is hv, the absorption coefficient is, the band gap energy is Eg, the absorption constants for indirect transitions are A. For PPy, ZnO, 15PZ, 30PZ, and 45PZ nanocomposites, the observed Eg values were 1.9 eV, 3.2 eV, 3.1 eV, 2.82 eV, and 2.86 eV, respectively.This suggests that increasing PPy can decrease bandgap, which in turn can enhance photocatalytic activity in the presence of sunlight.

Photoluminescence (PL) studies
Figure 4 displays the PL spectra for PPy, ZnO, and PPy/ZnO nanocomposites.At room temperature, excitation wavelength of PPy was 269 nm, while ZnO, PZ15, PZ30, and PZ45 had excitation wavelengths of 330 nm.At the same time, PPy emission peak was 293 nm, and the emission wavelengths of ZnO, PZ15, PZ30, and PZ45 was 492 nm.One of the best methods for determining a photocatalyst's efficiency is the PL study.High rates of electron and hole recombination decrease photocatalytic activity, as electrons and holes are essential to photocatalysis.Consequently, reduced photoluminescence intensity would result in higher photocatalytic activity [19].According to photoluminescence spectra, PZ30 is a highly effective photocatalyst.Due to the fact that the photoluminescence intensity is lower than in other nanocomposites.

Figure 3 .
Figure 3. (a)& (b) Excitation peak and emission peak of PPy, (c)&(d) Excitation peak and emission peak ZnO and PPy/ZnO nanocomposites 3.4 Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) analysis SEM and EDX analysis are two possible techniques for analysing the morphology and chemical composition of prepared samples.SEM picture in Figure 5 (a &c) shows that, PPy spherical grains structures are loosely aggregated and ZnO nanoparticles have structure that resembles a flower like structure with sharp edges.The surface morphology of 30PZ is displayed in Figure 5 (e).SEM pictures make it abundantly evident that the PZ30 nanocomposite has an agglomeration-sponge-like heterostructure, a porous surface, and erratically formed clusters of spherical grains (Figure 5(e)).With this heterostructure, the surface area, active sites, and photocatalytic activity are all boosted.Figure 5(b, d &f) displays the EDX spectrum for the PPy, ZnO and PZ30 nanocomposite, It demonstrates that synthetic samples contain C, N, O, and Zn.
This study effectively made PPy/ZnO NPs synthesized by eco-friendly coprecipitation and in situ polymaerisation method.Morphological research SEM pictures display the PZ30 nanocomposite has an agglomeration-sponge-like heterostructure, a porous surface, and erratically formed clusters of spherical grains.The optical energy bandgap increases as ZnO doping increases.ZnO, PZ15, PZ30 and PZ45.These outcomes demonstrated that the synthesised PZ30 nanoparticles could potentially use in the treatment of wastewater.