The detection of halogenated hydrocarbons via host–guest chemistry—a mass‐sensitive sensor study with QMB‐ and SAW‐devices

Abstract

Dedicated to Dr. Heinz Kimmel on the occasion of his 65th birthdayHost-guest chemistry is already widely used for the detection of ions['* 2] with suitable electrodes[31 and especially with the ion-sensitive field-effect transistor (ISFET)l3], a high selectivity being achieved in this way. These methods of molecular recognition are also well known for the inclusion of neutral molecules[4] by hosts in water. Only a few sensor applications exist in this field. The reason for this are the problems with the mass-sensitive devices,15] namely the quartz microbalance (QMB) and the more sensitive surfaceacoustic-wave oscillator (SAW). The oscillations of these elements are strongly damped in liquids and therefore a special type of elastic waves have to be used.[61 More favorable conditions, however, exist for the detection of gases and vapors using these mass-sensitive devices, and many examples of pure absorption processes have been reported, ['] although there are only a few reports about chemical reactions[*] and especially molecular recognitionL9, ' ' 1 being applied as the sensor phenomena. Shape recognition of the analyte can be achieved if the guest is included within the cavity of the host and not purely absorbed outside the hole. This strategy can lead to a high selectivity in analogy to the extremely specific but chemically unstable biosen~ors [~] where enzymes are the sensitive material.It is possible to decide whether the principles of host-guest chemistry are applicable for the detection of vaporous ana-

Acoustic Wave Sensors

“…Vapor sorbed among tethering alkyl chains or between cavitand molecules will give the same types of sensor signals as those bound inside the cavity. This fundamental question was recognized in early studies by Kohnke and Dickert (separately) [202,206]. Although responses have been interpreted in terms of host-guest inclusion complexes in many studies, there exists evidence for other possibilities.…”

“…Cavitand-coated sensors have been exposed to gas phase vapors and responses have been observed [200][201][202][203][204][205][206][207][208][209][210][211]. In some experiments, the sensors were exposed to brief pulses of vapors, such that steady state responses were not obtained, and the cavitand layer did not come to thermodynamic equilibrium with the gas phase vapor concentration.…”

“…It has been observed that cavitand-coated sensors respond to a great variety of vapors, rather than responding solely to those vapors with an ideal "fit" [200][201][202][203][204][205][206][207][208][209][210][211]216]. Thus, the promise of compound specific sensors has not been achieved by this approach.…”

Sensors for organic solvent detection in the ppm range based on dioxo[6.1.6.1]paracyclophanes—from molecular modeling to analyte recognition

“…Muter. 1993, 5, No. 4 Communications ADVANCED ___ MATERIALS more sensitive devices, while an optimized fit gives these layers improved recognition abilities.…”

Polyphenylene Dendrimers as Sensitive and Selective Sensor Layers This work has been supported by the TMR European Research Program, through the SISITOMAS Project, by the Volkswagen Foundation, the German Science Foundation (DFG), the German Federal Ministry for Science and Technology (BMBF), and the Fonds of the German Chemical Industry, Frankfurt (Main); U.M.W. thanks the latter for a graduate fellowship, we all thank C. Beer and S. Spang for valuable support during the syntheses.

“…These types of sensors are of increasing significance in many aspects of daily life, be it monitoring the manufacture or storage of foodstuff,2 controlling chemical reactions such as polymerization,3 or safety standards in the chemical industry, such as monitoring the maximum allowed concentration of VOCs in the work environment 4. QMBs are mass‐sensitive devices, which are easy to apply, yet of low cost, and they provide both high selectivity and excellent sensitivity down to concentrations of VOCs of only 5 ppm 5. Both properties of these gravimetric sensors crucially depend on the type of sensor‐active layer coated on top of the QMBs.…”