Fabrication of Thin Films of Phosphonated Calix[4]Arene Bearing Crown Ether and Their Gas Sensing Properties

Calix[4]arenes bearing phosphate and crown ether groups are shown to hold considerable promise as the active layer in volatile organic compound (VOC) vapor sensor. Its chemical sensing selectivity and sensitivity can be altered by different alkyl side chains. These organic architectures were successfully deposited by the spin coating method on gold-coated glass surfaces. Surface plasmon resonance technique was used for VOCs detection to evaluate the chemical-sensing properties of these calix[4]arene derivatives. Spun thin films of calix[4]arene derivatives were exposed to a variety of VOC vapors, and the resonance angles changes of these films were recorded for the specific analyte vapors, such as chloroform, carbon tetrachloride, dichloromethane, ethanol, benzene, and toluene. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. The sensing results showed similar response patterns, and our data strongly indicate that response of used thin films of calix[4]arene derivatives to chloroform is much higher than those of any other VOCs used with the values of 0.47 x 10 ^-3 , 1.042 x 10 ^-3 , and 1.952 x 10 ^-3 (% / ppm) for the compounds 1, 2, and 3, respectively. Furthermore, gas sensing interaction mechanisms of the thin films were evaluated in terms of the molar volumes, dipole moments, and refractive indexes of the analyzed gas molecules.