The nose is good, but a sensor is better


Chemists from the Voronezh State Technology Academy, in cooperation with colleagues from the Smolensk production combine Analytpribor have developed sensitive and durable sensors to determine the concentration of hydrogen sulphide in the air.

Their basis lies in so-called piezo-quartz resonators. These are devices in which the main component is a quartz substrate, coated with a special layer, which vibrates at a strictly determined frequency under the influence of an applied voltage. And if one is to try really hard, and can find such a material for this coating that would effectively and, of particular importance, selectively extract molecules of a particular substance from the air, one would get an original set of scales. Having become heavier with the molecules of the defined substance, “captured” from the air, the coating begins to vibrate on a new frequency, the value of which depends on precisely how much of the compound being analysed has accumulated in the coating material.

The authors used different materials for the receptor coating, the very same layer on the surface of the quartz substrate, including beeswax, which demonstrated pretty good results. However the best modifier proved to be Apiezon, a kind of thick lubricant or resin. To make it adhere well to the surface of the quartz the scientists propose that it first be treated with a polystyrene or starch solution.

Made in strict accordance with this methodology, the sensors will be able to define the content of hydrogen sulphide in the air 80,000 times. Then they can be changed and the old ones simply thrown away; this is a disposable and relatively inexpensive material.