Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2791

Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2791

A comprehensive review: SnO2 for photovoltaic and gas sensor applications

184-193Tin oxide is remarkable material in today’s research era due to its unique properties in electrical and optical fields. Due to its wide band gap (3.6 eV), it has been used as a core material in many important applications in the field of optoelectronics, spintronics, photovoltaic, thin-film transistors, photocatalysis, dielectrics, sensors and transparent electronic devices. Thin film technology provides many advantages towards photovoltaic area which includes low cost, less material and energy consumption and easy to access. Fabrication of photovoltaic cells by SnO2 thin films can open the different technological routes for future generation with excellent conversion efficiencies which may range 15% to 20%. It is one of the best candidates for gas sensor applications too with highest sensitivity and selectivity behavior, good oxidizing power, strong chemical bonding, non toxicity and unique transport properties. Tin oxide thin films with various combinations of materials can be synthesized by chemical and physical routes. The detailed advancement in various preparation methods and characterization techniques including X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy have been presented and discussed by authors. Characteristics measurement by Valence Band Structure, Photoluminence Intensity and Scanning Electron Microscope has been also reported with their performance, effect of solar energy conversion efficiency and quick response time in case of gas sensors. Prospective areas of SnO2 research for photovoltaic and gas sensor applications has been discussed and summarized by the authors. The obtained results will illustrate the possibilities of scheming Physical, chemical, magnetic and optical properties of SnO2 for sensing devices and photovoltaic applications

Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented

Amorphous-Carbon/Si Heterojunction device for Room Temperature NH3 Sensing and Development of Readout Circuit for Chemiresistive Sensor

Classical metal oxide gas sensors are used to be operated at relatively high temperatures to achieve good sensitivity. So there is a strong need to develop a gas sensing platform that provides either low temperature or room temperature sensing, so as to reduce the power consumption. Keeping this in mind, in this work, we have proposed and fabricated an amorphous-Carbon/Silicon (a-C/Si) heterojunction based room temperature ammonia gas sensor. We have optimized the fabrication process flow for obtaining a stable a-C thin film on Si substrate with strong adhesion. Here, to develop the a-C film, we have used pyrolysis of negative photoresist material SU8, which also provides us with the added benefit of photo-patternability. One of the desired outcomes of the proposed work is to provide a reduced response and recovery time. Also, we have targeted to achieve a low limit of detection with high selectivity. Additionally, we have developed a readout circuit for chemiresistive sensors, where change in device resistance is used as a transduction principle for targeted analyte detection. The circuit is designed to meet the specification of the sensor, where the desired detection range extended up to a few hundred Mega ohms. The requirements of the system have been studied and implemented using Cadence. The prototype of the circuit has been designed and tested

Perovskites-Based Nanomaterials for Chemical Sensors

The perovskite structure is adopted by many compounds in solid-state chemistry. The sensitivity, selectivity, and stability of many perovskite nanomaterials have been devoted the most attention for chemical sensors. They are capable to sense the level of small molecules such as O2, NO, and CO. This chapter provides a comprehensive overview of perovskite nanoscale materials that concentrate on chemical sensors. The perovskite structure, with two differently sized cations, is amenable to a variety of dopant additions. This flexibility allows for the control of transport and catalytic properties, which are important for improving sensor performance. We devote the most attention on the synthesis, structural information, and sensing mechanism. We will later elaborate on the development mechanism of chemical sensors based on perovskite nanomaterials. We conclude this chapter with the personal perspectives on the directions toward future works on a novelty of nanostructured chemical sensors

Low-temperature Fabrication Process for Integrated High-Aspect Ratio Metal Oxide Nanostructure Semiconductor Gas Sensors

This work presents a new low-temperature fabrication process of metal oxide nanostructures that allows high-aspect ratio zinc oxide (ZnO) and titanium dioxide (TiO2) nanowires and nanotubes to be readily integrated with microelectronic devices for sensor applications. This process relies on a new method of forming a close-packed array of self-assembled high-aspect-ratio nanopores in an anodized aluminum oxide (AAO) template in a thin (2.5 µm) aluminum film deposited on a silicon and lithium niobate substrate (LiNbO3). This technique is in sharp contrast to traditional free-standing thick film methods and the use of an integrated thin aluminum film greatly enhances the utility of such methods. We have demonstrated the method by integrating ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes onto the metal gate of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and the delay line of a surface acoustic wave (SAW) device to form an integrated ChemFET (Chemical Field-Effect Transistor) and a orthogonal frequency coded (OFC) SAW gas sensor. The resulting metal oxide nanostructures of 1-1.7 µm in height and 40-100 nm in diameter offer an increase of up to 220X the surface area over a standard flat metal oxide film for sensing applications. The metal oxide nanostructures were characterized by SEM, EDX, TEM and Hall measurements to verify stoichiometry, crystal structure and electrical properties. Additionally, the electrical response of ChemFETs and OFC SAW gas sensors with ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes were measured using 5-200 ppm ammonia as a target gas at room temperature (24ºC) showing high sensitivity and reproducible testing results

GAS SENSING PROPERTIES AND TRANSPORT PROPERTIES OF MULTI WALLED CARBON NANOTUBES

Multi walled carbon nanotubes (MWCNT) grown in highly ordered porous alumina templates were incorporated into a resistive gas sensor design and were evaluated for their sensitivities. The material characteristics and electrical properties of the nanotubes were analyzed. A study was undertaken to elucidate the effect of UV light on desorption characteristics and the dependence of sensitivity on (i) thickness of amorphous carbon layers and (ii) flow rates of analyte gases. These sensors were highly responsive to both oxidizing and reducing gases with steady state sensitivities of 5% and 10% for 100ppm of NH3 and NO2 respectively, at room temperature. As part of a comparative study, thick films of MWCNTs grown on Si/SiO2 substrates were integrated into various nano-composite based sensors and were evaluated for their response. Steady state sensitivities as high as 10% and 11% were achieved for 100ppm of NH3 and NO2 respectively, at room temperature. MWCNTs were characterized for their electrical properties by I–V measurements at room temperatures. A typical I-V curve with an ohmic behavior was observed for a device with high work function metals (example: Au, Pt); Schottky behavior was observed for devices with metal contacts having low work functions (example: Al, Cu)

Nanocomposite Films for Gas Sensing

Nanocomposite films are thin films formed by mixing two or more dissimilar materials having nano-dimensional phase(s) in order to control and develop new and improved structures and properties. The properties of nanocomposite films depend not only on the individual components used but also on the morphology and the interfacial characteristics. Nanocomposite films that combine materials with synergetic or complementary behaviours possess unique physical, chemical, optical, mechanical, magnetic and electrical properties unavailable from that of the component materials and have attracted much attention for a wide range of device applications such as gas sensors.NRC publication: Ye

Gas Sensors Based on Electrospun Nanofibers

Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films