Study of calixarenes thin films as chemical sensors for the detection of explosives

摘要

Calix(n)arenes (n = 4, 6, 8) are used as sensitive coatings for Quartz Crystal Microbalance (QCM)-based chemical sensors, and specially for the detection of dinitrotoluene as a model explosive molecule. Calix(n)arenes complex organic architectures were deposited by spray on gold-coated wafer surfaces, and DNT detection tests were performed by measuring both frequency changes and IR spectra during exposure to DNT vapours. The adsorption of DNT on calixarenes surface is proved by Polarisation Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) experiments, which brings a chemical characterisation of the sensing surfaces. Kinetics of interaction of DNT with the surface was measured by QCM. When deposited onto QCM, calixarenes showed an excellent sensitivity to DNT vapours; no significant effect of the size of the cage was observed. The main drawback is the poor reversibility of these sensors, possibly due to a too strong interaction of dinitrotoluene inside the cage of the calixarenes, or to a loss of the ternary structure of these molecules, which in turn induces a loss of interaction strength with host molecules.