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Optical Oxygen Sensor Using Silica Aerogel
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Silica aerogels are ideal materials for active and passive components in optical sensors. Their visible transparency, high surface area, facile transport of gases through the material, thermal and chemical stability, and ability to be filled with additional active phases are the key properties that aerogels bring to sensor applications. The Microstructured Materials Group at Berkeley Lab has recently discovered a new process that induces a permanent, visible photoluminescence in silica aerogels. Photoluminescence occurs when a material absorbs a photon of sufficient energy. The sensor is based on the observation that that the intensity of the photoluminescence is inversely proportional to the amount of gaseous oxygen within the aerogel.
The sensor is intended to perform as a low-cost, moderate sensitivity device operating most effectively in the concentration range of 0-30% oxygen. It operates independently of the nature of the other gases present in the feed gas, and of the feed gas flow rate. The prototype sensor has been successfully operated over a temperature range of -25 to +85°C (this range is based on other experimental limitations of the system, the actual usable range is larger). The highest sensitivity is observed at lower temperatures.
The prototype sensor used a mercury-arc lamp for excitation (330 nm), and a silicon photodiode for detection of the emission (500 nm). The recent availability of ultraviolet light emitting diodes makes the instrument much more attractive in terms of size and power requirements. The prototype design can be miniaturized easily, and a device can be designed with built-in pressure and temperature compensation.
Arlon Hunt, Senior Scientist
Physical Properties |
Chemical Properties |
Thermal Properties |
Gas Properties |
Nuclear Radiation |
Nano- and Fine Particle Measurement
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