I'd like to know what a piezoelectric sorption detector is. I can hardly find information about, only a small number of research papers which are mostly not accessable for me.
Only given from the term I cannot really imagine its functionality.
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The resonance frequency of a piezo-electric "tuning fork" is influenced by the mass of adsorbed molecules.
I know this kind of instruments as piezo thickness monitors when evaporating metals in vacuum equipment. They can be very sensitive.
Edit: there is a long article on Wikipedia. I did not read it all but it explains how this works. https://en.wikipedia.org/wiki/Quartz_crystal_microbalance
Edit 2: Such a piezoelectric resonator can be functionalized for sorption with a coating as described in 1964 by King in his article "Piezoelectric sorption detector"
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$\begingroup$ That was fast, thank you very much! I just want to ensure that I understand it correctly (I'm not a native speaker): Molecules or atoms get absorbed at these crystals and they produce voltage like "usually" for a piezoelectric effect? $\endgroup$– BenCommented Jul 24, 2020 at 8:58
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$\begingroup$ That was so fast, I'm not able to accept the answer already :) $\endgroup$– BenCommented Jul 24, 2020 at 8:59
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$\begingroup$ No. The extra mass of the adsorbed layer changes the mechanical resonance frequency of a piece of material. In this case, that resonator is like the quartz oscillator in a watch, coupled by the piezoelectric voltage to electronics. $\endgroup$– user137289Commented Jul 24, 2020 at 9:35
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$\begingroup$ Oh, ok, thanks for clearification! Do you know any online source where I can read up a bit on this topic? $\endgroup$– BenCommented Jul 24, 2020 at 9:55
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2$\begingroup$ Not exactly correct - the key difference is the ‘sorption’ part. For, say humidity, a hygroscopic layer is added to a MEMS device (could be just a simple QCM), which then makes the device more sensitive to whatever it preferentially absorbs. $\endgroup$ Commented Jul 24, 2020 at 12:13