Supramolecular detection of solvent vapours with QMB and SAW devices

Effective Use of Molecular Recognition in Gas Sensing: Results from Acoustic Wave and in Situ FT-IR Measurements

“…A number of reports attribute shape or class selectivities to cage compounds for sorption of various analytes. − Some of these “selectivities”, however, correlate more strongly with key thermodynamic properties of the analytes (e.g., saturation vapor pressure) than with a demonstrable specific interaction or recognition process. Consequently, the general idea of molecular recognition in gas sensors was questioned by Grate et al Nonetheless, we recently presented convincing evidence for specific recognition of certain target analytes, including the discrimination of enantiomers using supramolecular cages 9 and the detection of Lewis basic, nitrogen-containing volatile organic compounds (VOCs) using metal coordination; ongoing investigations of phthalocyanines provide further evidence for specific recognition .…”

Detection of Nonpolar Vapors on Quartz Crystal Microbalances with Ni(SCN)2(4-picoline)4 Coatings

“…Similarly, spin-coated Ni(SCN) 2 (pyridine) 4 and Co(SCN) 2 (4picoline) 4 films, like their corresponding spray-coated films, yield 17 We hypothesize that a nonclathrating tetrahedral complex of cobalt is preferentially deposited during spin-coating. The presence of the tetrahedral color in the deposition solution is indicated by its deep purple color.…”

“…2 To improve the sensitivity of piezoelectric sensors, researchers have examined alternative coatings with preformed cavities or channels. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Such coatings are anticipated to have higher partition coefficients for organic vapors than the amorphous polymers because the energy cost of forming a cavity for the solute molecule in the polymer solvent is reduced. The experiments of Yan and Bein 16 indicate that a partition coefficient of 35 000 could be obtained for octane vapor in a zeolite coating.…”

“…However, in the absence of strong intermolecular forces such as hydrogen bonding, their sensitivity to organic vapors limits the dynamic range of the sensor to higher vapor concentrations (above ppm levels) . To improve the sensitivity of piezoelectric sensors, researchers have examined alternative coatings with preformed cavities or channels. − Such coatings are anticipated to have higher partition coefficients for organic vapors than the amorphous polymers because the energy cost of forming a cavity for the solute molecule in the polymer solvent is reduced. The experiments of Yan and Bein 16 indicate that a partition coefficient of 35 000 could be obtained for octane vapor in a zeolite coating.…”

Surface Acoustic Wave (SAW) for Chemical Sensing Applications of Recognition Layers

“…The relative sensitivity and selectivity of cyclodextrin-derived mono- and multi-layers was compared, which revealed that going from mono- to multi-layer, the relative selectivity remains unchanged, however, the sensitivity increased by a factor of 140. Nonetheless, the thickness of the sensor layer is also important in reducing the noise level during sensor measurement since in another study [ 59 ] it was observed that cyclodextrin monolayers result in a homogeneous coating which showed noise of only 4 Hz for a 433 MHz SAW device.…”