Fullerene C60-cryptand coated surface acoustic wave quartz crystal sensor for organic vapors

A fullerene C60-cryptand 22 (C60-di-propylamine-cryptand 22) coated surface acoustic wave (SAW) quartz crystal gas detection system with 250 MHz oscillator and a computer interface for signal acquisition and data processing was prepared to detect various organic vapors. The C60-cryptand 22 coated SAW quartz crystal sensor exhibited sensitivity to both polar and nonpolar organic molecules. The C60-cryptand 22 was demonstrated as a better and more sensitive coating material than fullerene C60 or cryptand 22 for polar organic molecules. Comparison of C60-cryptand 22 coated SAW crystal and quartz crystal microbalance (QCM) sensors was also made and the SAW sensor exhibited much better response than the piezoelectric sensor for organic molecules with the same concentrations. The C60-cryptand 22 coated SAW crystal sensor could be repeatedly reused for the detection of most of organic vapors, e.g. alcohols, aldehydes, ketones, ethers, alkanes and alkenes. The selectivity of the C60-cryptand 22 coated SAW crystal sensor for various polar organic vapors seem to be in the order: alcohols>aldehydes>ketones>ethers. For nonpolar organic molecules, the C60-cryptand 22 coated SAW crystal sensor showed sensitivity for alkenes, e.g. hexene and benzene than for alkanes, 1-hexane and cyclohexane. Effects of molar mass, steric structures and isomers of organic molecules on the SAW frequency responses were also investigated. The SAW detection system showed the good detection limit of 0.1–3.0 mg/ml for these organic molecules. The C60-cryptand 22 coated SAW crystal sensor was successfully applied as a quite sensitive gas chromatography (GC) detector for various organic compounds. The C60-cryptand 22 coated surface acoustic wave GC detector compared well with the commercial thermal conductivity detector (TCD) for various organic molecules, e.g. organic halides, alcohols, alkenes and ketones.