In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer a wide spectrum of materials and their sensitivities for different gaseous species, making it a better choice over other options. In this article a critical parameter analysis of different metal oxides that are known to be sensitive to various gaseous species are thoroughly examined. This includes phase of the oxide, sensing gaseous species, operating temperature range, and physical form of the material for the development of integrated gas sensors. The oxides that are covered in this study include oxides of aluminum, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, indium, iron, manganese, molybdenum, nickel, niobium, ruthenium, tantalum, tin, titanium, tungsten, vanadium, zinc, zirconium, and the mixed or...

Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review

A gas-sensing mode based on chemiluminescence generated on the surface of nanosized materials is proposed in the present work. Seven nanosized materials were tested, and chemiluminescence was detected from six of them during the catalytic oxidation of organic vapors in air. The luminescence characteristics of ethanol and acetone vapors passing through the surface of TiO2 chosen were studied with a chemiluminescence-based detection system. The linear range of chemiluminescence intensity versus concentration of organic compounds is 40-400 microg/mL for ethanol and 20-200 microg/mL for acetone dissolved in water, respectively. X-ray powder diffraction and Raman spectrometry were used to investigate the changes in catalytic activity of TiO2 after a 60-h reaction at 380 degrees C. The results showed that the carbon deposited on the surface of TiO2, decreasing the catalytic activity, but can be removed in air by controlling the temperature at 500 degrees C for 3 h. Regenerability and no consumption of sensor substrate signify the long lifetime of the gas sensor.

Development of a gas sensor utilizing chemiluminescence on nanosized titanium dioxide.

Ferroelectric e-WO3 nanoparticles were synthesized and stabilized above room temperature for the first time. A sensor based on this material was found to be highly sensitive and selective to acetone gas which will serve as a good candidate for diabetes diagnosis based on human breath analysis.

Ferroelectric WO3 Nanoparticles for Acetone Selective Detection

Quartz as a natural luminescence dosimeter

Chemical and biological sensors have found their niche among modern analytical instruments when real-time determination of the concentration of specific sample constituents is required. Development of sensors with new capabilities is driven by the ever-expanding monitoring needs of a wide variety of species in gases and liquids. On the basis of a variety of definitions of sensors, 1-3 here we will accept that a chemical or biological sensor is an analytical device that utilizes a chemically or biologically responsive sensing layer to recognize a change in a single or multiple chemical or biological parameters of a measured environment and to convert this information into an analytically useful signal. In a sensor device, a sensing material is applied onto a suitable physical transducer to convert a change in a property of a sensing material into a suitable physical signal. The obtained signal from a single transducer or an array of transducers is further processed to provide useful information about the identity and concentration of species in the sample. The energy transduction principles that have been employed for chemical and biological sensing involve radiant, electrical, mechanical, and thermal types of energy. 4,5 Specific sensing concepts are further implemented with each energy transduction. Sensors based on radiant energy of transduction can employ intensity, wavelength, polarization, phase, or time resolution detection. Sensors based on electrical energy of transduction can employ conductometric, potentiometric, or amperometric detection. Sensors based on mechanical energy of transduction can employ gravimetric or viscoelastic detection. Sensors based on thermal energy of transduction can employ calorimetric or pyroelectric detection. Hyphenated techniques in sensing are of significant importance and combine several transduction techniques in one sensor. 6,7 In addition to a sensing material layer and a transducer, a modern sensor system often incorporates other important components such as sample introduction and data processing components. In contrast to sensing based on intrinsic analyte properties (e.g., spectroscopic, dielectric, thermal), indirect sensing utilizes a responsive sensing material. 2,5,8-13 This approach dramatically expands the range of detected species, improves sensor performance (e.g., analyte detection limits), and is more straightforwardly adaptable for miniaturization. 6,14-33

Combinatorial and high-throughput development of sensing materials: the first 10 years.

‘Cataluminescence’ is a kind of chemiluminescence emitted during catalytic oxidation of combustible gas. This paper describes a new method using a system which can measure spectroscopic images on a cataluminescence-based sensor to discriminate and determine concentrations of organic vapors in air. Using this equipment, we can measure continuously the image of ‘cataluminescence’ intensity, which reflects the type and concentration of organic vapor, as a function of wavelength and catalyst temperature. Not only the difference between alcohol and ketone, but also the kind of alcohol, e.g. ethanol and butanol, can be distinguished and determined quantitatively by means of this system.

A new method for recognizing organic vapor by spectroscopic image on cataluminescence-based gas sensor

A new method using cataluminescence (CTL)-based gas-sensor detecting hydrocarbon in air is proposed. CTL is a kind of chemiluminescence (CL), which is emitted during catalytic oxidation of organic vapors, e.g., ethanol and acetone. By depositing Dy on the γ-Al2O3 catalyst, we measured the extra CTL spectrum due to Dy3+ during the catalytic oxidation of hydrocarbon gas, while no such CTL was emitted from the γ-Al2O3 catalyst without Dy. By investigating the luminescence mechanism of Dy, the existence of active species produced in a course of catalytic oxidation to excite Dy directly was clarified. The CTL-based gas-sensor using γ-Al2O3 activated with Dy3+ has high sensitivity and linear characteristic. The detection limit of iso-butane in air is 0.2 ppm.

High sensitive hydrocarbon gas sensor utilizing cataluminescence of γ-Al2O3 activated with Dy3+

A chemiluminescence(CL)-based gas sensor made of γ-Al2O3 emits CL during catalytic oxidation of a combustible odor vapor. The CL intensity is proportional to the concentration of ethanol or acetone vapor in air. The algebraic sum rule is applicable to the CL intensities by the mixed gas of these two kinds of vapors, when the sensor is heated above 450°C. The CL intensities are measured in periodic temperature cycles between 650 and 450°C. The concentrations of vapor components can be detected analytically by measuring total CL intensities during the high and low temperatures for air containing mixed vapors of various concentrations of ethanol below 400 ppm and acetone below 200 ppm.

Analytical detection system of mixed odor vapors using chemiluminescence-based gas sensor

A new method is proposed for recognizing organic molecules dissolved in water using a chemiluminescence-based sensor made with a γ-Al2O3 catalyst. When a mixture of air and organic molecules, e.g. ethanol and acetone vaporized from a solution, flows around the sensor, chemiluminescence (CL) is emitted during its catalytic oxidation. The CL spectra consist of subbands peaking at the same wavelengths independent of the type of vapors. The peak wavelengths of these subbands are the same as those for CL with a CaCO3 catalyst. The relative CL intensity of each band, however, depends on the type of the vapor and the temperature of the sensor. This implies that CL originates in the same kinds of luminous species produced during the course of catalytic oxidation. By keeping a sample gas around the sensor in a state of laminar flow and by keeping the catalytic oxidation on the sensor under the diffusion-controlled condition, the CL intensity becomes stable and reproducible. The CL intensity is proportional to the concentration of these organic vapors in the gas phase within the concentration range of from 1 - 500 ppm.

/pdf/detection-of-organic-molecules-dissolved-in-water-using-a-g-wm8n711wpx.pdf

Detection of Organic Molecules Dissolved in Water Using a γ-Al2O3 Chemiluminescence-Based Sensor

Thermoluminescence caused by adsorbates (adsorption thermoluminescence) appears in the process of heating Al2O3 powder that had previously adsorbed the vapour of an organic solvent, such as ethanol or acetone, at room temperature. The profiles of the thermoluminescence spectrum and glow curve depend on the kind of adsorbed vapour. The total amount of emitted light L depends on the concentration of the vapour in air, and L increases with an increase in the duration of adsorption. The adsorbates that act as the origin of the thermoluminescence are accumulated through a Langmuir-type adsorption process of very low activation energy (about 0.02 eV). These characteristics of the adsorption thermoluminescence enable us to discriminate and determine very low concentrations of these vapours. For example, L is proportional to the concentration of acetone vapour below 20 ppm for an adsorption time of 10 min, and the 1 ppm of vapour can be measured with good reproducibility.

Masuo Nakagawa

Papers

A new method for recognizing organic vapor by spectroscopic image on cataluminescence-based gas sensor

High sensitive hydrocarbon gas sensor utilizing cataluminescence of γ-Al2O3 activated with Dy3+

Analytical detection system of mixed odor vapors using chemiluminescence-based gas sensor

Detection of Organic Molecules Dissolved in Water Using a γ-Al2O3 Chemiluminescence-Based Sensor

Discrimination and determination of gases utilizing adsorption luminescence