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SYNTHESIS AND OPTICAL CHARACTERIZATION OF NICKEL DOPED ZINC OXIDE NANOPARTICLES USING CHEMICAL BATH DEPOSITION METHOD

CHAPTER ONE

INTRODUCTION 

1.1  Background of the Study

The synthesis and optical characterization of nickel-doped zinc oxide (ZnO) nanoparticles are of significant interest in the field of materials science due to their potential applications in various technological domains. Zinc oxide, a wide-bandgap semiconductor with a bandgap of about 3.37 eV, has garnered attention for its use in electronic and optoelectronic devices (Hsu et al., 2018). The incorporation of transition metals such as nickel into ZnO can modify its electronic and optical properties, making it suitable for applications in catalysis, sensors, and photodetectors (Kumar et al., 2020).

Nickel doping in ZnO alters the material’s electronic structure by introducing new energy levels within the bandgap. This process can lead to enhanced photocatalytic activity, increased electrical conductivity, and modified optical properties (Nakamura et al., 2022). The chemical bath deposition (CBD) method, a low-cost and versatile technique, is commonly used for the synthesis of doped ZnO nanoparticles due to its simplicity and ability to produce high-quality films over large areas (Jha et al., 2019). This method involves the deposition of a thin film from a solution containing the precursors of ZnO and the dopant, which results in the formation of nanoparticles with controlled size and composition (El-Sayed et al., 2021).

The optical characterization of nickel-doped ZnO nanoparticles is crucial for understanding their potential applications. Techniques such as UV-Vis spectroscopy, photoluminescence (PL) spectroscopy, and Raman spectroscopy are employed to investigate the absorption, emission, and vibrational properties of these nanoparticles (Zhang et al., 2023). UV-Vis spectroscopy provides insights into the absorption edge and bandgap modification due to doping, while PL spectroscopy reveals the defect states and recombination mechanisms within the material (Patel et al., 2020). Raman spectroscopy, on the other hand, helps in identifying the vibrational modes and confirming the incorporation of nickel into the ZnO lattice (Cheng et al., 2022).

Recent studies have demonstrated that nickel doping can significantly enhance the photocatalytic activity of ZnO, making it an effective material for environmental applications such as the degradation of organic pollutants under UV light (Ghosh et al., 2021). Additionally, nickel-doped ZnO nanoparticles have shown promise in improving the performance of optoelectronic devices, including solar cells and light-emitting diodes (LEDs) (Singh et al., 2022). Understanding the relationship between doping concentration, particle size, and optical properties is essential for tailoring the material to specific applications and optimizing its performance.

The synthesis of nickel-doped ZnO nanoparticles using the chemical bath deposition method has been explored in various studies. For instance, Sharma et al. (2019) investigated the effect of nickel concentration on the structural and optical properties of ZnO nanoparticles and found that higher doping levels lead to increased defect density and changes in optical absorption. Similarly, Gupta et al. (2021) reported that the CBD method allows for precise control over the size and distribution of nanoparticles, which directly impacts their optical properties and performance in photocatalytic applications.

Overall, the synthesis and optical characterization of nickel-doped ZnO nanoparticles using the chemical bath deposition method represent a significant area of research with the potential to impact various technological fields. Understanding the effects of nickel doping on ZnO's properties will contribute to the development of advanced materials with tailored functionalities for specific applications.

1.2 Statement of the Problem

The increasing demand for advanced materials with tailored optical properties has driven significant research into the synthesis of doped semiconductor nanoparticles. Despite extensive studies on zinc oxide (ZnO) nanoparticles, the effects of nickel doping on their optical properties, particularly under varying doping concentrations and deposition conditions, remain inadequately understood. The challenge lies in optimizing the synthesis process using the chemical bath deposition method to achieve nanoparticles with desirable characteristics for specific applications. This research aims to address the gap in knowledge regarding how nickel doping influences the optical properties of ZnO nanoparticles and to develop a comprehensive understanding of their potential applications in photodetectors, sensors, and photocatalysts.

1.3 Objectives of the Study

The main objective of this study is to determine the effects of nickel doping on the optical properties of zinc oxide nanoparticles synthesized using the chemical bath deposition method.

Specific objectives include:

i. To evaluate the impact of nickel doping concentration on the structural and optical properties of ZnO nanoparticles.

ii. To determine the relationship between the synthesis conditions and the optical characteristics of nickel-doped ZnO nanoparticles.

iii. To find out the potential applications of nickel-doped ZnO nanoparticles based on their optical properties.

1.4 Research Questions

i. What is the effect of nickel doping concentration on the structural and optical properties of ZnO nanoparticles?

ii. What is the relationship between the synthesis conditions and the optical characteristics of nickel-doped ZnO nanoparticles?

iii. How does the optical characterization of nickel-doped ZnO nanoparticles influence their potential applications?

1.5 Research Hypotheses

Hypothesis I

H0: There is no significant impact of nickel doping concentration on the structural and optical properties of ZnO nanoparticles.

H1: There is a significant impact of nickel doping concentration on the structural and optical properties of ZnO nanoparticles.

Hypothesis II

H0: There is no significant relationship between the synthesis conditions and the optical characteristics of nickel-doped ZnO nanoparticles.

H2: There is a significant relationship between the synthesis conditions and the optical characteristics of nickel-doped ZnO nanoparticles.

Hypothesis III

H0: There is no significant influence of optical characterization on the potential applications of nickel-doped ZnO nanoparticles.

H3: There is a significant influence of optical characterization on the potential applications of nickel-doped ZnO nanoparticles.

1.6 Significance of the Study

This study is significant as it provides insights into the synthesis and optical characterization of nickel-doped ZnO nanoparticles, which are crucial for developing advanced materials with specific optical properties. The findings will contribute to the optimization of the chemical bath deposition method, enhance the understanding of the effects of doping on ZnO nanoparticles, and potentially lead to improved performance in various applications such as photocatalysis, photodetection, and optoelectronics.

1.7 Scope of the Study

The study focuses on the synthesis of nickel-doped ZnO nanoparticles using the chemical bath deposition method and their subsequent optical characterization. The scope includes investigating the impact of different nickel doping concentrations and synthesis conditions on the optical properties of the nanoparticles. The study will cover the use of UV-Vis spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy for optical characterization.

1.8 Limitations of the Study

The study may be limited by factors such as the availability of high-purity reagents, the precision of the chemical bath deposition method, and the reproducibility of the synthesis process. Additionally, the characterization techniques used may have limitations in terms of resolution and sensitivity, which could affect the accuracy of the results.

1.9 Definition of Terms

Nickel-Doped Zinc Oxide (ZnO) Nanoparticles: Zinc oxide nanoparticles that have been doped with nickel to modify their optical and electronic properties.

Chemical Bath Deposition Method: A technique used to deposit thin films of materials from a chemical solution, resulting in the formation of nanoparticles on a substrate.

Optical Characterization: Techniques used to analyze the optical properties of materials, including absorption, emission, and vibrational characteristics.

Photocatalysis: The acceleration of a chemical reaction using light, often involving the degradation of organic pollutants.

Photodetectors: Devices that detect and measure light, converting optical signals into electrical signals.

Photoluminescence (PL) Spectroscopy: A technique used to study the emission of light from a material after it has absorbed photons.

Raman Spectroscopy: A technique used to study vibrational modes in a material by analyzing the scattering of monochromatic light.