A new device analyzes gas mixtures using semiconductor sensors. Odor is determined by a combination of existing gases in the atmosphere. Researchers have found that the conductivity of a semiconductor probe changes during sedimentation of the gas molecules from the atmosphere, which indicates their presence, says Timur Muksunov. During manufacture, the sensor can be customized to react differently to various atmospheric gases.
However, according to the scientist, it is impossible to make a sensor that reacts to only one gas—the system is needed to achieve sensitivity and selectivity. This allows, via certain processing techniques, accurately identifying the gas mixture in the air, which experiments confirm.
One of the experiments attempted to determine the freshness of fruits and vegetables. Fruits and vegetables emit hydrogen sulphide, ammonia and other gases. The closer the sell-by date of the products, the more of these gases were detected.
"We investigated the apples: A control was refrigerated and the rest were left at room temperature," says the scientist. "After 12 hours, the device was able to identify that the unchilled fruit emits gases more intensively than the control fruit. Now, the vegetable warehouse receives products by their organoleptic characteristics, and using the device will more accurately determine the shelf life of products, which will affect quality."
The device is fully developed and is being tested for effectiveness.
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T. R. Muksunov et al. Increase in the Sensitivity and Selectivity of Semiconductor Gas Sensors, Russian Physics Journal (2015). DOI: 10.1007/s11182-015-0376-1