Preface

Nanostructured materials (NMs) are at the heart of 21st-century nanotechnology. They are artificial materials formed as microstructures with length on the nanometer scale. NMs may be defined as those materials whose structural elements, including cluster, crystal, and molecule, have dimensions in the range of 1–100 nanometers. The explosion in both academic and industrial interest in NMs arises from their remarkable variations in fundamental electrical, optical, and magnetic properties, which range from macroscopic solids to accountable atomic particles. This book provides a comprehensive overview of the current state of the art in the synthesis, device design, and investigation of functional NMs as well as their potential applications, focusing on their outstanding physical and chemical aspects at the micro/nanoscale. Carbon materials (CVD graphene, graphene oxides, and carbon nanotubes (CNTs)), plasmonic 2D materials, and other nanostructures (metal nanowires, metal oxides, nanoparticles (NPs), nanofibers, metamaterials, nanocomposites, and nanofertilizers) play an important role in nanoscience and nanotechnology and thus this book examines them in detail. The book also addresses emerging achievements of NM-based applications for industry, biomedicine, and sustainable agriculture. This book is divided into five sections. The first section describes the physic aspects of NMs in photodetectors and transistors, and the superconductivity for quantum technology, while the second section introduces representative plasmonic 2D materials (e.g., CVD graphene, graphene oxide, hBN, MXenes, pnictogens, metal oxides) and related applications in electronics and optoelectronics. The third section discusses emerging NMs. Since many NMs have been developed recently, this section introduces readers to only the topmost emerging NMs. It provides a fundamental demonstration of NMs for applications in industry and biomedicine. The fourth section briefly discusses nanofertilizers and their applications in sustainable agriculture and the environment. The fifth and final section highlights the behaviors of electrochemistry at the interfaces of electrode/solution under in-depth theoretical analysis and features of electrochemical impedance spectroscopy.

Chapter 1 introduces various approaches to using nanostructured metasurface designs to increase the photon capture on a thin detector architecture, which helps to minimize thermally generated dark current and achieve higher absorption efficiency.

Chapter 2 examines the physic impact of noises such as random telegraph noise, thermal noise, flicker noise, and shot noise on Tunnel FET devices and circuits integrated with Si/Ge and III–V groups. The reliability issues of the device have a profound impact on the circuit level design for practical perspectives. Noise is one of the important parameters in terms of reliability and very few research papers address this issue in comparison to other parameter studies. This chapter will help increase understanding of noise issues.

Chapter 3 presents recent advances in plasmonic 2D materials (graphene, graphene oxides, hexagonal boron nitride, pnictogens, MXenes, metal oxides, and nonmetals) and discusses their potential for emerging applications. The chapter is

divided into several sections to elaborate on recent theoretical and experimental developments along with potential in the photonics and energy storage industries.

Chapter 4 is a significant contribution to mid-wave infrared (MWIR) detection and imaging for NASA Earth Science applications using high-performance bilayer graphene-HgCdTe detector technology. This chapter discusses the principles, structures, fabrication process, and theoretical modeling for graphene/HgCdTe interface, as well as doping and transfer techniques on bilayer graphene.

Chapter 5 analyzes the heat transfer of water-based CNTs in non-coaxial rotation flow affected by magnetohydrodynamics (MHD) and porosity. Here, single-walled carbon nanotubes (SWCNTs) provide high values of Nusselt number compared to multi-walled carbon nanotubes (MWCNTs). For verification, the chapter presents a comparison between the present solutions and a past study that shows excellent agreement.

Chapter 6 reviews the experimental work and progress of nanowire technology over the last several decades, with more focus on recent work. The final section of this chapter discusses future trends in nanowire research, including nanowire implementation in daily electronic tools to satisfy the demand for electronics of low weight and small size.

Chapter 7 provides a comprehensive summary of fundamental principles of synthesis strategies to control the dimensionality of anisotropic nanowires, their crystal growth, and optical and electrical properties in the fabrication of ultrathin metal hydroxide/oxide nanowires for optoelectronic applications. The chapter highlights the governing theories of crystal growth processes and kinetics that control the anisotropy and dimensions of nanowires.

Chapter 8 begins with a survey of metal-oxide semiconductors (MOS) and their 1D nanostructures with the greatest potential for use in the next generation of chemical sensors, which will be of very small size, low-power consumption, low price, and superior sensing performance compared to chemical sensors on the market currently. The chapter also describes 1D MOS nanostructures, including composite and hybrid structures, and their synthesis techniques. Then, the chapter presents the architectures of current resistive and FET sensors and discusses the methods for integrating 1D MOS nanostructures into these sensors on a large scale and in a cost-effective manner. The chapter concludes with an outlook of the challenges facing chemical sensors based on 1D MOS nanostructures if their massive use in sensor networks is to become a reality.

Chapter 9 deals with the topochemical synthesis of blue titanium oxide (b-TiO2) and its energy storage application as an electrode material for supercapacitor devices in aqueous and organic electrolytes. The mechanism of formation of b-TiO2 via topochemical synthesis and its characterization using X-ray diffraction, UV–visible, photoluminescence, electron spin resonance spectroscopy, laser Raman spectrum, X-ray photoelectron spectroscopy, and morphological studies (FE-SEM and HR-TEM) are discussed in detail. Collectively, this chapter highlights the use of b-TiO2 sheets as advanced electrodes for 3.0 V supercapacitors.

Chapter 10 examines the use of NPs in biomedical fields. It presents the features of biopolymer silk fibroin and its applications in nanomedicine. Silk fibroin, obtained from the Bombyx mori silkworm, is a natural polymeric biomaterial whose main

features are its amphiphilic chemistry, biocompatibility, biodegradability, excellent mechanical properties in various material formats, and processing flexibility. All these properties make silk fibroin a useful candidate to act as a nanocarrier. As such, this chapter reviews the structure of silk fibroin, its biocompatibility, and its degradability. In addition, it reviews silk fibroin NP synthesis methods. Finally, the chapter discusses the application of silk fibroin NPs for drug delivery systems.

Chapter 11 reviews the design of NPs proposed as drug delivery systems in biomedicine. It begins with a historical review of nanotechnology including the most common types of NPs (metal NPs, liposomes, nanocrystals, and polymeric NPs) and their advantages as drug delivery systems. These advantages include the mechanism of increased penetration and retention, transport of insoluble drugs, and controlled release. Next, the chapter discusses NP design principles and routes of administration of NPs (parental, oral, pulmonary, and transdermal) as well as routes of elimination of NPs (renal and hepatic).

Chapter 12 studies the green synthesis of different NPs from metal. The inspiring applications of metal oxide NPs have attracted the interest of scientists. Various physical, chemical, and biological methods in materials science are being adapted to synthesize different types of NPs. Green synthesis has gained widespread attention as a sustainable, reliable, and eco-friendly protocol for biologically synthesizing a wide range of metallic NPs. Green synthesis has been proposed to reduce the use of hazardous compounds and as a state of a harsh reaction in the production of metallic NPs. Plant extracts are used for the biosynthesis of NPs such as silver (Ag), cerium dioxide (C2O2), copper oxide (CuO), gold (Au), titanium dioxide (TiO2), and zinc oxide (ZnO). This chapter gives an overview of the plant-mediated biosynthesis of NPs that are eco-friendly and have less hazardous chemical effects.

Chapter 13 explores the development of metamaterials (MMs) and metasurfaces and clarifies their exotic behavior. MMs are artificial materials that obtain their properties from their accurately engineered meta-atoms rather than the characteristics of their constituents. The size of the meta-atom is small compared to the light wavelength. It also addresses the promising applications of MMs in medicine, aerospace, sensors, solar-power management, crowd control, antennas, army equipment, and reaching earthquake shielding and seismic materials.

Chapter 14 illustrates the synthesis of nanocomposite materials through horizontal vapor phase growth (HVPG) and future trends. Since the application of nanomaterials can be found in very wide aspects, the synthesis process of nanomaterials using HVPG can be an alternative method. The future trend as shown in the chapter ensures the sustainability of the synthesis of nanomaterials without compromising the environment and human health.

Chapter 15 provides brief information about production methods (e.g., electrospinning, wet spinning, drawing), characterization methods (e.g., SEM, TEM, AFM), and tissue engineering applications (e.g., core-shell fibers, antibacterial fibers, NPs incorporated fibers, drug-loaded fibers) of nanofibers.

Chapter 16 summarizes recent achievements in nanofertilizers that use nanocomponents such as nanozeolite, nano-hydroxyapatite, macronutrient, NPs, nano-bio fertilizers, and others for innovative applications in horticulture and sustainable agriculture and environment.

Chapter 17 reveals one of the most useful tools to understand the electrode/solution interface: electrochemical impedance spectroscopy (EIS). This tool allows us to describe electrode behavior in presence of a certain electrolyte in terms of electrical parameters such as resistances, capacitances, and so on. With this information, we can infer the electrochemical behavior towards a specific reaction and the capacity of the electrode to carry on the electron transfer depending on its resistance (impedance) values. This chapter presents information on theory, such as Ohm´s Law and its derivations, as well as actual applications.

I acknowledge all the contributing authors for their excellent chapters. I would also like to thank the staff at IntechOpen for their assistance throughout the preparation and publication of this book.

> **Phuong V. Pham** School of Micro-Nano Electronic, Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China
