Using clathrate pseudopolymorphism for a single sensor detection of target component in the headspace of liquid mixture

A new sensing mechanism for mass-sensitive sensors is offered, which is based not on the preferential binding as usual, but on the specific shape of sensor kinetic response. The used mechanism includes formation of an intermediate clathrate and then of a saturated clathrate between a substrate (guest) and a receptor (host), which breaks the sensor response into two separate steps. The corresponding host–guest pseudopolymorphism allows the discrimination of a target substrate in complex mixtures using a single gravimetric sensor. This mechanism does not require for a substrate to have multiple functional groups for a complementary host–guest binding. Moreover, qualitative and quantitative molecular recognition of hydrocarbon in the mixtures with its close homologues can be achieved. Such ability was performed in the present work for a thiacalix[4]arene derivative coating of a quartz-microbalance sensor, which is able to recognize benzene in the headspace of its liquid mixtures with toluene, xylenes, ethylbenzene, water, nitriles, alcohols and other compounds. The pseudopolymorphism of host–guest clathrate and low-temperature polymorphism of the host was confirmed by the determination of vapor sorption isotherms, thermoanalysis and X-ray powder diffraction analysis of the host–guest saturation products.