In this thesis, we introduce approaches to carbon nanotube-based sensing for applications in environmental monitoring, disease diagnostics, and food analysis: In Chapter 1, we introduce carbon nanotube-based sensing. We describe parameters that give rise to the sensing capabilities of CNT-based sensors and discuss important performance parameters of carbon nanotube sensors. In Chapter 2, we demonstrate voltage-activated sensing of carbon monoxide using a sensor comprising iron porphyrin and functionalized single walled carbon nanotubes (F-SWCNTs). Modulation of the gate voltage offers a predicted extra dimension for sensing. Specifically, the sensors show significant increase in sensitivity toward CO when negative gate voltage is applied. In Chapter 3, we describe the design of a sensor for the highly selective detection of acrylates using conditions for the aerobic oxidative Heck reaction. The sensors mirror the catalytic processes and selectively respond to electron deficient alkenes by adapting a catalytic reaction system to modulate the doping levels in carbon nanotubes. In Chapter 4, we introduce sensor arrays consisting of imidazolium-based ILs with different substituents and counterions to provide selective responses for known biomarkers of infectious diseases of the lungs. In Chapter 5, we discuss a sensor array comprised of platform 20 functionalized SWCNT sensing channels for the classification of cheese, liquor, and edible oil samples based on their odor. We classify unknown food samples using a k-nearest neighbors model and a random forest model trained on extracted features. This protocol allows us to accurately differentiate between five cheese and five liquor samples (91% and 78% respectively) and only slightly lower (73%) accuracy for five edible oils.

Carbon Nanotube-Based Sensors: Fabrication, Characterization, and Implementation highlights the latest research and developments on carbon nanotubes (CNTs) and their applications in sensors and sensing systems. It offers an overview of CNTs, including their synthesis, functionalization, characterization, and toxicology. It then delves into the fabrication and various applications of CNT-based sensors. FEATURES Defines the significance of different forms of CNT-based sensors synthesized for diverse engineering applications and compares the feasibility of their generation Helps readers evaluate different types of fabrication techniques to generate CNTs and their subsequent sensing Discusses fabrication of low-cost, efficient CNTs-based sensors that can be used for diverse applications and sheds light on synthesis methods for a range of printing techniques Highlights challenges and advances in security-related issues using CNTs-based sensors This book is aimed at researchers in the fields of materials and electrical engineering who are interested in the development of sensor technology for industrial, biomedical, and related applications.

Carbon nanotubes, with their extraordinary mechanical and unique electronic properties, have garnered much attention in the past five years. With a broad range of potential applications including nanoelectronics, composites, chemical sensors, biosensors, microscopy, nanoelectromechanical systems, and many more, the scientific community is more moti

Application as well as detection of different chemicals plays an important role in the progress of modern science and technology. The beauty of various characteristics of materials and the inherent logic behind their working mechanisms can be wisely utilized for sensing different chemicals. The mechanisms as well as performances of different materials viz. carbon nanotube, graphene, metal oxides, biomaterials, luminescent metal-organic frameworks, hydrogels, textiles, quantum dots, ligands, crown ethers etc. for identification of different chemicals has been discussed here. This book would be a valuable reference to select suitable materials for possible use in chemical sensors.

The major theme of this thesis is to investigate the influence of defects on the sensing mechanisms and performance of gas sensors made from films of carbon nanotubes, chemical vapor deposition (CVD) graphene film, CVD graphene ribbons, and surfactant exfoliated graphene. The definition of defects on carbon materials is the disordered carbon atoms formed due to dislocations, vacancies, and deformations. These defects were introduced during processing. The thesis is separated into three sections that analyze various types of defects on these carbon based chemical sensors. First section focuses on single-walled carbon nanotubes with point defects. It will be demonstrated that these point defects can alter the main sensing mechanism of the CNT based sensors. There is a controversy in literature on whether the sensing response seen in carbon nanotube chemiresistors is associated with a change in the resistance of the individual carbon nanotubes or changes in the resistance of the junctions. A network analysis was carried out to better understand the relative contributions of the carbon nanotubes and the junctions on the change in resistance of the carbon nanotube network. It was found that the dominant mode of detection in carbon nanotube networks changes according to the defect level in the carbon nanotubes which may explain the apparently contradictory results in the literature. With high concentration of the point defects in the carbon nanotube film along with applying high electric field, the Poole-Frenkle conduction regime can be induced. Generally, desorption of gases from carbon nanotubes is a slow process that limits the carbon nanotubes0́9 utility as sensors. It will be demonstrated that electron flows in the carbon nanotube above the Poole-Frenkel conduction threshold can stimulate adsorbates to desorb without heating the sensor significantly. This desorption process is analogous to electron stimulated desorption, but with an internally conducted rather than externally applied source of electrons. As a result, this gives a fast and reversible CNT sensor within seconds. An application can be utilized to use carbon nanotubes based GC detector for multi-component chemical analysis. The approach is to use a CNT based detector in a series configuration with a gas chromatography column. It will demonstrated that a mixture of nine different compounds can be detected with these CNT based detectors when the detector operates in current stimulated desorption (CSD) mode. This is the first demonstration of a CNT based GC detector to analyze multi-component gas mixtures providing a new sensing approach for online air quality control and health monitoring applications. The second section of the thesis focuses on analyzing two-dimensional line defects arises from wrinkles and grain boundaries as well as edge defected created manually on the graphene film synthesized with chemical vapor deposition (CVD) process. Due to two-dimensional nature of the graphene film, adsorption of isolated analyte molecules on point defects has minimal effect on graphene resistance because current pathways can always form around the adsorbate. In contrast, analytes adsorbing on line defects lead to significant changes in resistance. It will be demonstrated that polycrystalline graphene easily obtained through chemical vapor deposition contains line defects. This can offer a scalable path to 50x more sensitive chemiresistors than mechanically exfoliated crystalline graphene. Moreover, current flow can be confined by cutting the polycrystalline graphene into ribbons, the sensitivity increases by another factor of four. These results show that polycrystalline graphene has extraordinary sensitivity, achieved through geometry and linear defect density. The last section of the thesis focuses on intrinsic two-dimensional edge defects on graphene isolated with sodium cholate surfactant assisted exfoliation of graphite powders. With this technique, it is possible to produce high edge defect concentrations for individual graphene island due to its micron-sized dimension offering more defects per unit area. Various randomly-stacked oxide-free graphene films can be formed with various filtration volumes. It will be demonstrated the films produced can range 6 orders of magnitude in film conductance. At thinner graphene films, the electron transport mechanism is mainly through two-dimensional variable range hopping. At thicker graphene films, electron transport is through fluctuation-assisted tunneling. It is also observed the graphene films go from semiconducting-like to metallic-like behavior at around 8 mL filtration volume. At low filtration volumes, oxide-free randomly stacked graphene film sensors showed better sensitivity towards target molecules compared to polycrystalline/ribbon graphene and defective CNT gas sensors due to two-dimensional electron hopping. As the graphene film thickness increases, there is a shift in conduction mechanism from two-dimensional electron hopping to metallic-like conduction which explains the drop in sensitivity as the filtration volume increases.

Carbon-Based Nanomaterials and Nanocomposites for Gas Sensing discusses the state of the art, emerging challenges, properties, and opportunities of various carbon-based nanomaterials and nanocomposites, for their application in smart gas sensors. The book focuses on various carbon-based nanomaterials and their nanocomposites, sensing mechanism, device fabrication, and their application for the sensing of various hazardous gases. This is important for several industries, environmental monitoring, and human healthcare, due to increased industrialization. Carbon-Based Nanomaterials and Nanocomposites for Gas Sensing provides systematic and effective guidelines for researchers who want to gain a fundamental understanding of how this class of materials is being used for gas sensing. Since these sensors can be applied for the automation of numerous industrial processes, as well as for everyday monitoring of various activities, such as public safety, engine performance, medical therapeutics, and in many other situations, this book will catch the attention of readers and motivate them for advanced research in the development of smart and efficient gas sensors. - Offers a one-stop resource, bringing together information currently scattered over journal papers and project reports - Presents a focused concept reflecting the properties, synthesis, and sensing capabilities of carbon-based nanomaterials and their composites - Combines fundamental experimental and theoretical information with industrial needs and engineering design methods

Chemical sensors that identify and monitor volatile organic compounds (VOCs) have an important role in assessing public security, food and water quality, industrial environment, and health. The fabrication of carbon-based sensors by printing, dip coating, drop casting, or drawing has advantages of being simple and low-cost without the need for highly specialized facilities. We have investigated the fabrication of sensors both by drop casting and drawing. Single-walled carbon nanotubes (SWCNT) electronic and spectroscopic properties for sensory applications are described. SWCNTs have unique properties wherein their conductance can be altered by environmental effects. These carbon nanomaterials can be easily integrated into a chemiresitive device to detect various analytes. In our studies using the drop cast method, we noncovalently functionalized SWCNT with a trifunctional selector that has three important properties: it noncovalently functionalizes SWCNTs with cofacial n-n interactions, it binds to cyclohexanone (a target analyte for explosive detection) via hydrogen bond, and it improves the overall robustness of SWCNT-based chemiresistors (e.g., humidity and heat). In our other studies, we fabricated sensors by drawing. Abrasion is a safe, simple, solvent-free, and low cost method for deposition of carbon-based materials onto a substrate. We successfully demonstrated fabrication on a wide variety of substrates (e.g., weighing paper, polymethyl methacrylate, silicon, and adhesive tape) of fully-drawn chemical sensors on a chip that can detect in real time parts-per-million (ppm) quantities of various vapors using SWCNTs as sensing materials and graphite as electrodes. This fabrication methodology does not require specialized facilities (e.g., clean room, thermal evaporator) and can be performed entirely on a desktop (with appropriate ventilation and safety precautions for handling nanomaterials). We also extended the abrasion method to detect anions such as fluoride (use to manufacture nuclear weapons) and cyanide (chemical warfare agent). These sensor are highly sensitive detecting the United State Environmental Protection Agency (EPA) maximum contaminant level (MCL) of fluoride and cyanide selectively.

Carbon Nanomaterials and their Nanocomposite-Based Chemiresistive Gas Sensors: Applications, Fabrication and Commercialization sets out how carbon nanomaterials based chemiresistive gas sensor are made, and their applications at lab and industrial levels. The book focuses on major advances in the field of chemiresistive gas sensors in recent years and their potential applications in environmental monitoring and healthcare. Carbon Nanomaterials and their Nanocomposite-Based Chemiresistive Gas Sensors: Applications, Fabrication and Commercialization provides systematic and effective guidelines to the researchers as well as learners about sensor, their fabrication and applications. Chemiresistive sensors are widely used in automation of numerous industrial processes as well as for everyday monitoring of various activities as public safety, engine performance, medical therapeutics, and in many other situations hence the book will catch the attention of readers and motivate them for advanced research for the development of smart and efficient gas sensors. With full coverage of the state of the art in this active research field, the book will appeal to researchers in a broad range of disciplines, including nanotechnology, engineering, materials science, chemistry and physics. - Offers a one-stop resource, bringing together information currently scattered over journal papers, industrial/lab outcomes and project reports - Presents information about the properties, synthesis of nanomaterials, their device fabrication and applications as sensing materials - Combining fundamental, experimental and theoretical knowledge with industrial needs and engineering design methods

Carbon nanomaterials have gained relevance in chem/bio sensing applications owing to their unique chemical, mechanical, electrical, and thermal characteristics. Written by leading experts in the field, this book discusses selected, state-of-the art carbon-based nanomaterials, including nanodiamonds, graphene nanodots, carbon nanopores, and nanocellulose. It presents examples of chem/bio sensing applications ranging from biomedical studies, such as DNA sequencing and neurotransmitter sensing, to heavy-metal detection in environmental monitoring scenarios, and reviews the unique properties of carbon-based nanomaterials with respect to targeted sensing applications. Further, it highlights exciting future applications. Providing comprehensive information for practitioners and scientists working in the field of carbon nanomaterial technologies and their application, it is also a valuable resource for advanced students of analytical chemistry, biochemistry, electrochemistry, materials science, and micro-/nanotechnology and -sensing.

Carbon Nanomaterials-Based Sensors: Emerging Research Trends in Devices and Applications covers the most recent research and design trends for carbon nanomaterials-based sensors for a variety of applications, including clinical and environmental uses, and more. Carbon nanomaterials-based sensors can be used with high sensitivity, stability and accuracy compared to other techniques. Written by experts in their given fields from around the world, this book helps researchers solve the particular challenges they face when developing new types of sensors. It instructs how to make sensitive, selective, robust, fast-response and stable carbon nanomaterial-based sensors, as well as how to utilize them in real life. - Covers the environmental monitoring and analytical implications of electro-analytical methods, one of the most dynamically developing branches of carbon nanomaterials - Includes a complete discussion of functionalized nanostructure materials reformulated with noble materials and advanced characteristics for improved applications when compared to standard materials - Covers sustainability and challenges in the commercialization of carbon nanomaterials-based sensors