Compact hollow waveguide mid-infrared gas sensor for simultaneous measurements of ambient CO2 and water vapor

A compact, sensitive and stable hollow waveguide (HWG) mid-infrared gas sensor, based on gas absorption lines using wavelength modulation spectroscopy with a second harmonic (WMS-2f) detection scheme, was developed for simultaneous measurements of ambient CO 2 and water vapor. Optimization of the laser modulation parameters and pressure parameter in the HWG are performed to improve the strength of the WMS-2f signal and hence the detection limit, where 14.5-time for CO 2 and 8.5-time for water vapor improvement in system detection limit is achieved compared to those working at 1 atm. The stability of the sensor has been improved significantly by optimizing environmental disturbances, incoupling alignment of the HWG and laser scanning frequency. An Allan variance analysis shows detection limit of the developed sensor of ~3 ppmv for CO 2 and 0.018% for water vapor, which correspond to an absorbance of 2.4 × 10 -5 and 2.7 × 10 -5 , with a stability time of 160 s, respectively. Ambient CO 2 and water vapor measurement have been performed in two days in winter and spring separately. The measurement precision is further improved by applying a Kalman adaptive filter. The HWG gas sensor demonstrates the ability in environmental monitoring and the potential to be used in other areas, such as industrial production and biomedical diagnosis

Review of low-cost sensors for the ambient air monitoring of benzene and other volatile organic compounds

This report presents a literature review of the state of the art of sensor based monitoring of air quality of benzene and other volatile organic compounds. Combined with information provided by stakeholders, manufacturers and literature, the review considered commercially available sensors, including, PID based sensors, semiconductor (resistive gas sensor) and portable on-line measuring devices (sensor arrays). The bibliographic collection includes the following topics: sensor description, field of application in fixed, mobile, indoor and ambient air monitoring, range of concentration levels and limit of detection in air, model descriptions of the phenomena involved in the sensor detection process, gaseous interference selectivity of sensors in complex VOC matrix, validation data in lab experiments and under field conditions.JRC.C.5-Air and Climat

Synthesis, characterisation and photocatalytic activity of porous silicon-based materials

As a free and abundant alternative energy source, the use of sunlight to store and transfer energy is of great importance to a clean and sustainable future. Aiming for an environmentally and economically friendly approach to utilizing solar energy, metal-free, earth-abundant mesoporous silicon with hydrogen termination were developed via inexpensive electrochemical etching. By means of a range of characterisation tools, a detailed structural analysis was established, showing a large surface area, open porous system and abundant quantum confined Si nanocrystallites of which the morphological properties can be controllably tuned through adjusting etching parameters and wafer resistivity. As a result, an excellent efficiency in degrading methyl orange under visible light irradiation was achieved in the following photocatalytic study, which also revealed the influence of different structural factors on the photocatalytic performance by affecting mass transport, light absorption and photoexcited charge recombination. The photocatalytic mechanism of mesoporous silicon in methyl orange degradation was also investigated in this research, with insights gained into the electronic band properties, photocatalytic oxidation facilitated by the generation of reactive oxygen species and the roles of surface hydrides on the degradation pathways of methyl orange. By coupling with graphitic carbon nitride (g-C3N4) nanosheets, the formed heterostructure showed an enhanced degradation activity towards methyl orange under visible light illumination. An exciton-related pathway was proposed to explain the promoted reducing power of the surface hydrides upon irradiation with or without the participation of g-C3N4. In general, this work highlighted the potentiality of H-terminated mesoporous silicon in photocatalytic applications and deepened the understanding of its photocatalytic mechanism and degradation behaviour for future exploration of porous silicon-based photocatalysts

Summaries of FY 1997 Research in the Chemical Sciences

The objective of this program is to expand, through support of basic research, knowledge of various areas of chemistry, physics and chemical engineering with a goal of contributing to new or improved processes for developing and using domestic energy resources in an efficient and environmentally sound manner. Each team of the Division of Chemical Sciences, Fundamental Interactions and Molecular Processes, is divided into programs that cover the various disciplines. Disciplinary areas where research is supported include atomic, molecular, and optical physics; physical, inorganic, and organic chemistry; chemical energy, chemical physics; photochemistry; radiation chemistry; analytical chemistry; separations science; heavy element chemistry; chemical engineering sciences; and advanced battery research. However, traditional disciplinary boundaries should not be considered barriers, and multi-disciplinary efforts are encouraged. In addition, the program supports several major scientific user facilities. The following summaries describe the programs

37th Rocky Mountain Conference on Analytical Chemistry

Final program, abstracts, and information about the 37th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 23-27, 1995

SELF-ORGANIZATION IN MICROWAVE FILAMENTARY DISCHARGES

We studied the self organising phenomena im filamntary microwave discharge at various pressures and excitation types

43rd Rocky Mountain Conference on Analytical Chemistry

Final program, abstracts, and information about the 43rd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 29 - August 2, 2001