Functionalization and applications of CNTs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2012.Vita. Cataloged from PDF version of thesis.Includes bibliographical references.Carbon nanotubes (CNTs) possess a unique set of electrical and mechanical properties and have been used in a variety of applications. In this thesis, we explore strategies to functionalize CNTs as well as applications which are enabled by functionalized CNTs. Chapter 1 gives an overview of emerging applications of CNTs. In Chapter 2, we describe a route that leads to highly water-soluble multi-walled CNTs (MWCNTs). The good solubility facilitates processing and manipulation of the CNTs. Furthermore, we explore the use of soluble MWCNTs as electrical interconnects in water. Using a Wacker type oxidation reaction, we demonstrate that this type of CNTs can have a positive effect on reactions that involve a metal to metal electron transfer. In Chapter 3, we explore catalytic aziridination reactions to functionalize CNTs as well as [60]fullerene and graphite. In Chapter 4, we use amine functionalized single-walled CNTs (SWCNTs) to attach receptors for gas sensing applications. We optimize the receptors and test the functionalized SWCNTs in an array sensor with regard to sensitivity, selectivity, stability and reproducibility. In Chapter 5, we demonstrate a highly selective sensor for N-methylammonium salts based on SWCNTs that are functionalized with a cavitand. In Chapter 6, we describe a sensor for the plant hormone ethylene. The sensor is based on SWCNTs that are non-covalently functionalized with a copper complex. The device shows good sensitivity and selectivity for ethylene and could be useful in the horticultural industries.by Jan M. Schnorr.Ph.D

Carbon-based materials for humidity sensing: a short review

Humidity sensors are widespread in many industrial applications, ranging from environmental and meteorological monitoring, soil water content determination in agriculture, air conditioning systems, food quality monitoring, and medical equipment to many other fields. Thus, an accurate and reliable measurement of water content in dierent environments and materials is of paramount importance. Due to their rich surface chemistry and structure designability, carbon materials have become interesting in humidity sensing. In addition, they can be easily miniaturized and applied in flexible electronics. Therefore, this short review aims at providing a survey of recent research dealing with carbonaceous materials used as capacitive and resistive humidity sensors. This work collects some successful examples of devices based on carbon nanotubes, graphene, carbon black, carbon fibers, carbon soot, and more recently, biochar produced from agricultural wastes. The pros and cons of the dierent sensors are also discussed in the present review

Carbon Nanotube-Based Polymer Composites: Synthesis, Properties and Applications

The present chapter covers the designing, development, properties and applications of carbon nanotube-loaded polymer composites. The first section will provide a brief overview of carbon nanotubes (CNTs), their synthesis, properties and functionalization routes. The second section will shed light on the CNT/polymer composites, their types, synthesis routes and characterization. The last section will illustrate the various applications of CNT/polymer composites; important properties, parameters and performance indices backed by comprehensive literature account of the same. The chapter concludes with the current challenges and future aspects

Sebuah Review: Polianilin (PANi) Sebagai Bahan Aktif Pendeteksi Asam

AbstrakArtikel ini berisi tentang aplikasi polianilin (PANi) sebagai bahan aktif pendeteksi asam yang terdiri dari asam kuat yaitu hidrogen klorida (HCl) dan asam lemah terdiri dari hidrogen sulfida (H2S), asam askorbat (C6H8O6), dan asam asetat (CH3COOH). Analit tersebut merupakan senyawa yang biasa ditemui dalam kehidupan sehari-hari. Pengunaan PANi dan kompositnya dapat meningkatkan selektivitas dan sensitivitas yang baik untuk mendeteksi keberadaan senyawa asam. Pembentukan PANi dan kompositnya menjadi lapisan tipis, pelet, dan elektroda menarik perhatian sebagai bahan aktif pendeteksi asam. Berdasarkan review ini dapat diketahui bahwa semakin besar konsentrasi analit maka sensitivitas yang dihasilkan juga semakin besar. Nilai konsentrasi minimal analit HCl, H2S, C6H8O6, dan CH3COOH yang mampu dideteksi oleh PANi dan kompositnya masing – masing adalah 0,2 ppm; 0,05 ppm; 4,7 ppm; dan 1 ppm.Kata Kunci: PANi, Sensitivitas, Selektivitas, Asam AbstractThis article contains the application of polyaniline (PANi) as an active acid detection ingredient consisting of strong acids namely hydrogen chloride (HCl) and weak acids consisting of hydrogen sulfide (H2S), ascorbic acid (C6H8O6), and acetic acid (CH3COOH). This analyte is a compound commonly found in daily life. The use of PANi and its composites can increase selectivity and good sensitivity for acid compatibility. The formation of PANi and its composites into thin layers, pellets, and electrodes attracts attention as active ingredients for acid detection. Based on this review more analytes can be obtained, the resulting sensitivity is also greater. The minimum concentration of analytes HCl, H2S, C6H8O6, and CH3COOH that can be detected by PANi and its composites are 0.2 ppm; 0.05 ppm; 4,7 ppm; and 1 ppm.Keywords: PANi, Sensitivity, Selectivity, Aci

Recent Trends in the Microwave-Assisted Synthesis of Metal Oxide Nanoparticles Supported on Carbon Nanotubes and Their Applications

The study of coating carbon nanotubes with metal/oxides nanoparticles is now becoming a promising and challenging area of research. To optimize the use of carbon nanotubes in various applications, it is necessary to attach functional groups or other nanostructures to their surface. The combination of the distinctive properties of carbon nanotubes and metal/oxides is expected to be applied in field emission displays, nanoelectronic devices, novel catalysts, and polymer or ceramic reinforcement. The synthesis of these composites is still largely based on conventional techniques, such as wet impregnation followed by chemical reduction of the metal nanoparticle precursors. These techniques based on thermal heating can be time consuming and often lack control of particle size and morphology. Hence, there is interest in microwave technology recently, where using microwaves represents an alternative way of power input into chemical reactions through dielectric heating. This paper covers the synthesis and applications of carbon-nanotube-coated metal/oxides nanoparticles prepared by a microwave-assisted method. The reviewed studies show that the microwave-assisted synthesis of the composites allows processes to be completed within a shorter reaction time with uniform and well-dispersed nanoparticle formation

Development of electrochemical nitrite biosensors using cytochrome c nitrite reductase from Desulfovibrio desulfuricans ATCC 27774

Dissertação apresentada para a obtenção do Grau de Doutor em Química Sustentável pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaREQUIMTE ; Fundação para a Ciência e Tecnologia -(POCI/QUI/58026/2004 and SFRH/BD/28921/2006

Graphene — A Platform for Sensor and Biosensor Applications

Graphene, mother of all carbon materials, has opened up new era of exploration due to its unique properties. Graphene, one-atom thick, exhibits a unique chemical structure and outstanding electronic, optical, thermal, and mechanical properties that made it compelling for various engineering applications. Graphene and graphene-based materials are promising candidates for fabricating state-of-the-art nano-scale sensors and biosensors. They featured with good conductivity and large specific surface area thereby; graphene-based sensors/biosensors performed well with good accuracy, rapidness, high sensitivity and selectivity, low detection limits, and long-term stability. They are ideally used as gas sensors, electrochemical sensors for heavy metal ions, immunosensors and dihydronicotinamide dinucleotide NADH, DNA, catecholamine neurotransmitters, paracetamol, glucose, H2O2, hemoglobin, and myoglobin biosensors. This chapter reviews the applications of graphene in nanotechnology since it came to the field particularly in sensing and biosensing applications. It updates the reader with the scientific progress of the current use of graphene as sensors and biosensors. There is still much room for the scientific research and application development of graphene-based theory, materials, and devices. Despite the vast amount of research already conducted on graphene for various applications, the field is still growing and many questions remain to be answered

Understanding Heterostructure Chemiresistive Gas Sensing at Room Temperature

Chemiresistive sensors are the most widely investigated gas sensors due to their ease in fabrication, cost-effectiveness, simplicity of operation, and offer advances in miniaturization. Up to date, typical and well-researched resistive-type sensing materials include semiconductor metal oxides, noble metals, carbon-based nanomaterials (e.g., graphene and carbon nanotubes), and conducting polymers. Gas sensors based on a single material were found difficult to meet the practical requirements for multi-sensing properties, including sensitivity, selectivity, speed of response/recovery, stability, limit of detection, and room temperature operation. Rational design through a combination of chemically or electronically dissimilar nanomaterials is an effective route to enhancing gas sensing performance. Because the chemical composition varies with position, especially at the interface between two dissimilar materials, the newly hybridized structure is defined as a heterostructure. During the past decades, there has been significant research effort in exploring the nanocomposite heterostructures for chemiresistive room-temperature gas sensors. However, sensing mechanisms for such heterostructures are still elusive without solid analysis or direct characterization results. The objective of this dissertation study is to understand the sensing mechanisms of heterostructure-based chemiresistive gas sensors through in situ investigation and analysis under real operating conditions. Various novel heterostructures have been developed for specific types of gas sensing, with a variety of in situ/operando techniques applied to investigate the sensing mechanisms toward different gases. Firstly, nickel oxide-tungsten oxide (NiO-WO3) nanowire-based heterostructures with various component ratios were fabricated via a facile, sonication-based solution mixing method. The exhibited heterojunction effect is maximally observed for W3N1 (75 mol% WO3-25 mol% NiO) and confirmed by observation of the increase in resistance due to the formation of a diode-like p-n junction at the NiO-WO3 interface. The excellent hydrogen sulfide (H2S) sensing performance for W3N1 is attributed to the p-n junction effect, sulfurization by H2S (formation of tungsten sulfides (WS2-x), and nickel sulfides (NiS1-x)), and the ideal ratio of the NiO component in the composite. The formation of reactive semi-metallic products due to sulfurization on the sensor surface was confirmed by in situ X-ray diffraction (XRD) analyses. Operando impedance measurements and resistor-capacitor (RC) equivalent circuit analyses during gas sensing experiments were performed to evaluate the effect of grain-grain boundary or the p-n junction on the sensing performance. It was found that for pure WO3 and W3N1 samples, these contributing effects are in the same direction, resulting in a cooperative and highly sensitive performance, whereas, for other compositions, the samples exhibited competing influences, resulting in low sensitivity. Secondly, the gold doped tin oxide/reduced graphene oxide (Au-SnO2/rGO) ternary nanohybrid heterostructure was designed with improved room temperature hydrogen (H2) sensing performance. The sputtered Au nanoparticles enhanced both sensitivity and recovery of the SnO2-rGO platform. Such an enhancement was attributed to the increased surface area and the oxygen ions spillover effect of loaded Au nanoparticles. The catalytic effect of Au nanoparticles for hydrogen adsorption and desorption was then revealed through the temperature-dependent gas sensing test and the Arrhenius analysis. A better balance between sensitivity and recovery can be further achieved in the future by tuning the deposition conditions of Au nanoparticles. A prototype handheld device based on the Au-SnO2/rGO composites was finally developed for hydrogen detection. The prototype device demonstrates the potential for real-time hydrogen monitoring. The availability of such sensors will contribute to promoting a sustainable hydrogen economy, protecting public safety, and enhancing lead-acid battery safety in a wide range of applications. Thirdly, the nickel-doped tin oxide-reduced graphene oxide (Ni/SnO2-rGO) ternary nanohybrid heterostructure was prepared with enhanced room temperature sulfur dioxide (SO2) sensing performance. The Ni additives significantly improved the lower detection limit (ppb level) of the SnO2-rGO platform. The SO2 concentration calibration curve is well fitted by the Langmuir isotherm. The humidity effect on the sensing performance was also investigated. The results suggested that current nanohybrid materials still suffer from the humidity effect. Metal oxide nanocomposite doping enhanced the SO2 sensing and activated the adsorption of water molecules, which diminished the sensor response to sulfur dioxide gas. Finally, the Poly[3-(3carboxypropyl)thiophene-2,5-diyl]regioregular (PT-COOH)-GO binary nanocomposite heterostructure was prepared. The gas sensing properties were investigated toward NO2, NH3, SO2, and CO. The PT-COOH based sensors exhibited tunable sensing performance through the drain voltage modulation. PT-COOH-GO sensors indicated enhanced NO2 sensing performance with good sensitivity, recovery, and stable responses. The statistical signal analysis was conducted to obtain proof-of-concept results for gas discrimination through signal processing. This study reveals the electronic conduction gas sensing model of multi-metal oxide -nanowires-based chemiresistive gas sensors through the combination of direct current (DC) and alternating current (AC) impedance measurements. The research also suggests that two-dimensional (2D) rGO with proper modifications can be efficient gas sensing materials toward various gaseous analytes. Combining in situ characterization and critical sensing factor analyses, results from the study will offer valuable and comprehensive insights for the rational design of superior heterostructure-based chemiresistive gas sensors

Recent Advances in Chemical Functionalisation of Graphene and Sensing Applications

Graphene, a one-atom-thick, sp2-hybridised allotrope of carbon has attracted massive interest due to its outstanding electrical, mechanical, thermal and optical properties. The material of graphene is remarkably stable, with a huge potential for developing various types of sensors, including biomedical sensing where enhanced specificity, sensitivity, label-free nature and cost effectiveness for rapid point-of-care detection of diseases are paramount. This is due to the simplicity with which its electronic properties can be modified since each atom in the structure directly interacts with the sensing environment. These unique characteristics can be exploited for several kinds of sensing applications such as electrochemical and electrical sensors as well as optical sensors. While pristine graphene is desirable for applications that require high electrical conductivity, many other applications require functionalised graphene for optimal performance. Therefore, the functionalisation of graphene is a significant step towards tuning its structure for various sensing applications. In this review, we report recent technological progress in the chemical functionalisation of graphene and its sensing applications