Elsevier

Environmental Research

Volume 203, January 2022, 111842
Environmental Research

Structure, morphology and modelling studies of polyvinylalcohol nanocomposites reinforced with nickel oxide nanoparticles and graphene quantum dots

https://doi.org/10.1016/j.envres.2021.111842Get rights and content

Highlights

  • NiO/GQDs reinforced PVA (PNG) films were prepared by solution casting technique.

  • Significant variations in the properties of PVF/TiO2 nanocomposites was observed.

  • Interactions of the constituents of PNG films were proved by DFT studies.

  • NiO/GQDs incorporation into PVA matrix to be employed for functional applications.

Abstract

Nickel oxide (NiO) nanoparticles (NPs) and graphene quantum dots (GQDs) reinforced polyvinyl alcohol (PVA) nanocomposite films were prepared using a solution casting technique. The physicochemical characteristics of PVA/NiO/GQDs (PNG) nanocomposite films were studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). The obtained PNG nanocomposite films showed good mechanical flexibility and improved tensile strength. The influence of nanofiller concentrations on PNG nanocomposite film. The obtained results demonstrate an increase in the activation energy (Ea) up to PNG3 upon increasing the GQDs concentration and thereafter, its decreases. The fundamental interactions of the constituents of PNG nanocomposite film were investigated using density functional theory (DFT). This study on electronic structure reveals that the PVA model indirectly interacts with GQDs through the NiO model. This configuration is favoured in terms of interaction energy (−78 kJ/mol) compared to the one in which PVA interacts directly with the GQDs model.

Introduction

Recently, polymers have attracted great attention in a broad range of applications in various technological areas. Traditionally, poly (vinyl alcohol) (PVA) has been widely used amidst a range of conducting and non-conducting polymers owing to its availability in different molecular weights and cost-effectiveness. Furthermore, it exhibits significant film forming characteristic, good water solubility, and easy processability. Also, it is non-toxic, biocompatible, biodegradable and illustrates good resistance to chemical effect (Adhikari and Majumdar, 2004; Ningaraju et al., 2018; Thangamani et al., 2017). Moreover, it demonstrates excellent optical, electrical, and thermal properties. These remarkable properties make PVA an ideal candidate for many applications that include biomedical devices, drug delivery, membrane technology, fuel cells, and gas sensors (Karuppasamy et al., 2021a, Karuppasamy et al., 2021b; Davar et al., 2018; Nangia et al., 2019). To enhance the properties of PVA, various nanofillers are usually added. The changes in the polymer properties occur due to the large surface area of the nanofillers (Theerthagiri et al., 2021; Karuppasamy et al., 2021; Thangamani et al., 2017; Davar et al., 2018). One such nanofiller is nickel oxide (NiO) nanoparticles (NPs), a p-type semiconducting metal oxide with a wide energy bandgap of 3.6–4.0 eV. It has excellent properties such as high chemical stability, high melting point (1960 °C) and excellent electrical and optical properties. The electrical conductivity varies due to the change in the charge carriers of NiO nanoparticles. The variation in NiO structures is due to the non-stoichiometric effect that makes them suitable for solar cells, electrochromic devices, optoelectronic and sensing applications (Theerthagiri et al., 2021; Hotovy et al., 2002; Tian et al., 2016; Gomaa et al., 2018).

On the other hand, graphene quantum dots (GQDs) belong to the family of carbon materials. They have remarkable electrical properties with tunable optical and electrical properties as compared to graphene. They are zero-dimensional materials obtained from two-dimensional graphene, which results in edge effect and quantum confinement makes them very good candidates for diverse applications (Tian et al., 2018; Raeyani et al., 2016; Kumar et al., 2020). Edge atoms in GQDs lead to a good interaction with the surrounding molecules compared to graphene due to the large surface to volume ratio (Zhang et al., 2012). The bandgap tuning property and electron transport ability with a change in the size of GQDs can be used in sensing (Feng et al., 2019). Hydroxyl, carboxyl, and carbonyl pendant groups serve as a linker in GQDs, making them possible to combine with polymers such as PVA. Due to proper dispersion in the polymer solution, NiO and GQDs are considered potential candidates to fabricate novel hybrid materials for various applications. On this context, NiO and GQDs were used as nano fillers and integrated into the PVA matrix (Adhikari and Majumdar, 2004). In this study, an attempt has been made to synthesise and characterise PNG nanocomposite film by incorporating various composition of NiO and GQDs into the PVA matrix. This investigation also explores the possible physical forces involved in stabilising the formed complex from the results of density functional theory (DFT). In recent days, first principle DFT studies have been widely used in the field of basic research to applications due to the development of efficient algorithms and codes (Hafner et al., 2006; Narasimhan, 2020).

Section snippets

Materials

PVA was purchased from SD Fine Chem. Ltd, India with an average molecular weight of 85,000–1,24,000 g/mol−1 with the degree of hydrolysis of 86–89 %. NiO was purchased from Sigma Aldrich, India. NiO NPs were about <50 nm size with a molecular weight of 74.69 g/mol. GQDs of nearly15 nm and thickness between 0.5 and 2 nm were purchased from Sisco Research Laboratories (SRL) Pvt. Ltd, India. Distilled water was used as a solvent throughout the work.

Synthesis of PNG nanocomposite film

In a typical PNG nanocomposite film synthesis,

FTIR spectroscopy analysis

FTIR is a promising technique to characterise the functional groups and molecular interactions in the materials. In the present study, this technique is used to understand and characterise the PNG nanocomposite films. Fig. 2 shows the FTIR spectra of PG, PN and PNG nanocomposite film at various concentrations. A broad region between 3016 cm−1 and 3668 cm−1 corresponds to the stretching band of the hydroxyl group. The presence of a broad peak around 3284 cm−1 is due to the stretching of the O–H

Conclusions

PVA nanocomposite films reinforced with NiO NPs and GQDs (PG, PN, PNG1-PNG6)were synthesised by the solution casting technique. The physicochemical characteristics and thermal studies were carried out using FTIR, XRD, FESEM and TGA. The XRD patterns revealed the formation of PNG nanocomposite films. All the functional groups in the PNG nanocomposite films were confirmed through FTIR spectroscopic analysis. GQDs and NiO nanofillers' complex formation is confirmed through FESEM images and

Credit author contribution statement

Y. Ravi Kumar – Conceptualization, Writing – review & editing. Kalim Deshmukh – Writing – review & editing. M. Mohamed Naseer Ali – Writing – review & editing. Gade Abhijay – Writing – review & editing. Wedad A. Al-Onazi – Writing – review & editing. Amal M. Al-Mohaimeed – Project administration, Investigation, Supervision. S.K. Khadheer Pasha - Project administration, Resources, Supervision, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements:

This work was supported by RGEMS project, VIT-AP/2021/VC/IIC/RGEMS. The authors extend their appreciation to the researchers supporting project number (RSP-2021/247) at King Saud University, Riyadh, Saudi Arabia.

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