화학적 검출을 위한 비정질 탄소 기반 전계 효과 트랜지스터 = Amorphous carbon based-field effect transistor for chemical detections

다국어 초록 (Multilingual Abstract)

Field-effect transistors (FETs) are a promising approach to tiny, low-power chemical sensors. But they are limited by the surface instability of semiconducting channels and the short lifetime of enzyme-based interfaces. The primary purpose of this thesis is to create a high-performance ZnO thin film that is covered with a polymer-like amorphous carbon (PAC). So that it can insulate the semiconductor channel from the outside environment and improve its pH sensing performance, second, provide a strong, non-chemical method of dry surface functionalization using ammonia plasma to form covalent bonds with AKCN. The ZnO/PAC-AKCN functionalized devices were studied utilizing analytical techniques such as confocal fluorescence microscopy, which measured the AKCN surface covering intensity. Lastly, the enhanced sensor platform was able to identify small chemicals, insecticides, and heavy metal ions. Chapter 1 provides a theoretical overview of the shortcomings of earlier methods and explains how the FET-based sensing platform incorporates nanozyme (AKCN) for real-time chemical detection in order to address the conventional issues with enzymatic-based sensors. This section summarizes extensive research on the significance of nanozyme integration into FET systems. This chapter describes the development and characterization of a ZnO thin film shielded by a PAC layer. The fabrication of ZnO thin devices using sputter, photolithography, ICP, thermal evaporator, and furnace is covered in the first chapter. To address the issue of ZnO instability, it was further funtionalized with a PAC dielectric layer. The amorphous carbon (PAC) layer protects the semiconductor channel from the external environment and improves its pH sensing robustness.
Chapter 3 describes functionalization of receptors like AKCN nanozyme(a nanomaterial with enzyme-like activity). After the initial optimization, modified graphitic carbon nitride nanozyme (AKCN) with glucose oxidase-like and peroxidase-like activity was first synthesized and characterized. Initially, GCN was synthesized using Melamine. In order to increase the overall performance of GCN, it was modified with KOH and KCL during the process of thermal calcination. A novel material was synthesized, known as AKCN, for further functionalization on the already established ZnO/PAC sensing platform. This chapter also describes the effects of ammonia plasma treatments(time and pressure) on the surface coverage of synthesized AKCN. After the initial characterization of ammonia plasma by XPS, further confirmation of AKCN immobilization was done by confocal fluorescence microscopy using the value of surface coverage intensity calculated by Zen(lite) software.
Chapter 4 describes real-time detection. It describes pH and Hydrogen peroxide detection using a ZnO/PAC sensing platform. Protection of ZnO with PAC makes this sensing platform sensitive and stable to different pH levels and hydrogen peroxide. This chapter also describes the Detection of Glucose and hydrogen peroxide in a single platform using ZnO/PAC funtionalized AKCN devices. The AKCN surface coverage has a direct impact on the sensitivity of glucose sensing. The sensing mechanism of the light effect was also derived based on sensing results. The AKCN-functionalized ZnO/PAC FET platform exhibited reversible responses, with minimal pH dependence. Part 2 describes the Diquat detection of ZIPF and AKCN-functionalized ZnO/a-C thin-film devices. The devices also show selective detection capability of diquat solution as compared to other pesticides and metal ions. Finally, the established platform was tested across different pH environments to assess its applicability for real-time applications. Overall, this thesis describes a viable chemical surface functionalization process that combines PAC- PAC-stabilized ZnO FET design with AKCN-type nanozymes to offer stable, pH-tolerant, and non-enzymatic FET-based detection. The potential of a heterogeneous solid-state platform for upcoming integrated, continuous chemical monitoring applications is demonstrated by the detection of pH, hydrogen peroxide(H2O2), glucose, and diquat.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1. Biochemical Sensor and the Principle of FETs 2
• 1.2. Graphitic carbon nitride (g-C₃N₄) as a multifunctional platform 6
• 1.3. Recent trends for glucose biosensors and pesticide detection 14
• 1.4. Overview of current methods for the detection of pesticides 20
• 1.4.1. Fluorescence and Colorimetric sensing for paraquat and diquat detection 22
• 1.4.2. SERS-based Raman spectroscopic detection of diquat 23
• 1.4.3. Electrochemical platforms for the detection of pesticides 24
• 1.4.3. Field effect transistor(FET) based sensor for pesticide detection 25
• 1.5. Literature studies of glucose-sensing mechanisms 29
• 1.6. Previous studies of FET-based sensors 35
• 1.6.1 Ammonia-plasma-functionalized ZnO/PAC FET platform 35
• 1.6.2 Electrolyte-gated ZnO/PAC and 2D-material FET-based pH sensor 36
• 1.7 Earlier studies of modified g-C₃N₄-based Glucose and DQ detection 41
• 1.8. Limitations of the previous solution-based sensors 48
• 1.9. Motivations and originality of this work 49
• Chapter 2. Fabrication and characterization of ZnO/PAC thin film 52
• 2.1. Introduction 52
• 2.2. Experimental details 57
• 2.3. Results and Discussion 66
• 2.3.1. Characterization of ZnO Film and ZnO/PAC surface 66
• 2.3.2. Optimization and characterization of PAC thin film 71
• 2.3.3. Electrical characteristics of the devices(back-gate and Solution top-gate) 75
• 2.4. Summary 79
• Chapter 3. Surface functionalization process of FET-based sensor 80
• 3.1. Introduction 80
• 3.2. Experimental details 84
• 3.2.1. Synthesis process of AKCN and ZIPF polymer for the functionalization 84
• 3.2.2. Device functionalization with AKCN as a receptor 85
• 3.2.3. Ammonia plasma deposition process by ICP(Inductively coupled plasma) 85
• 3.3. Results and Discussion 95
• 3.3.1. Characterization of synthesized AKCN and ZIPF 95
• 3.3.2. XPS Analysis of the Amine Functionalized Surface 99
• 3.3.3. Optimization of ammonia plasma condition for AKCN surface coverage 102
• 3.3.4. Electrical characteristics of funtionalized surface 108
• 3.4. Conclusion 110
• Chapter 4. Real-time detections using plasma-based functionalization 111
• 4.1. Detection of Hydrogen Peroxide/Glucose using AKCN funtionalized devices 111
• 4.1.1. Introduction 111
• 4.1.2. Experimental Details 117
• 4.1.3. Results and Discussion 118
• 4.1.3.1. Real-time detection of pH on the ZnO/PAC device 118
• 4.1.3.2. Hydrogen peroxide detection using an unfunctionalized device 122
• 4.1.3.3. Real-time detection of Glucose using the AKCN funtionalized surface 130
• 4.1.4. Summary 130
• 4.2. Diquat detection using ZIPF and AKCN functionalized ZnO/PAC devices 153
• 4.2.1. Introduction 153
• 4.2.2. Experimental details 156
• 4.2.3. Result and discussion 157
• 4.2.3.1. Detection of Diquat using ZIPF funtionalized surface 157
• 4.2.3.2. Real-time detection of Diquat using AKCN functionalized ZnO/PAC thin film surface 162
• Summary and future work 185
• Acknowledgments 189
• References 190