Piezoelectric crystal membrane chemical sensors based on fullerene C60

Various reusable and sensitive piezoelectric (PZ) quartz crystal membrane sensors with home-made computer interfaces for signal acquisition and data processing were developed to detect organic/inorganic vapors and organic/inorganic species in solutions, respectively. Fullerene C60 and synthesized fullerene derivatives, e.g. C60-cryptand22 and C60-dibenzo-16-crown-5 were applied as coating materials on quartz crystals of the PZ crystal sensors. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic or inorganic species onto coating material molecules on the crystal surface. The C60-coated PZ crystal sensor was firstly prepared to study the adsorption and the interaction between fullerene C60 and organic molecules. Only amines, dithios, alkynes and 1,3-dienes seem to perform chemisorption onto fullerene while physical adsorption is found in all other cases like alcohols, aldehydes and carboxylic acids. The reactivities of fullerene C60 and other conjugated olefins to various organic molecules seem to be in the order β-carotene>C60>pyrene. The fullerene C60-coated PZ crystal sensor also can be employed to sensitively detect some organic molecules, e.g. aldehydes, carboxylic acids, amines and olefins. A C60-cryptand22-coated PZ gas sensor for both polar/nonpolar organic vapors was also prepared. The cryptand22-coated PZ gas sensor can be employed as a GC detector for organic molecules. The C60-cryptand22-coated crystal GC-PZ detector compared well with the commercial thermal conductivity detector (TCD). Various liquid PZ crystal sensor based on C60-cryptand22 and dibenzo-16-crown-5-C60 were also prepared as liquid chromatographic (LC) detectors for metal ions, anions and polar/nonpolar organic molecules in solutions. The frequency responses of the C60-cryptand22-coated LC-PZ detectors for various organic molecules and metal ions were compared well with the responses of a commercial UV–VIS detector and a conductivity detector which are generally used in LC systems.