Zeolite crystal layers coupled to piezoelectric sensors

Microporous zeolite crystals were successfully coupled onto the gold electrodes of quartz crystal microbalances (QCM). A self-assembled monolayer of thiol-alkoxysilane coupling agent on the gold surface was used as the interfacial layer to promote adhesion of the zeolite crystals to the QCM. The resulting, densely packed single layers of zeolite crystals were stable to at least 625 K. Transient sorption behavior of organic vapor pulses, dynamic vapor sorption isotherms and nitrogen sorption isotherms at liquid nitrogen temperature were examined to characterize the zeolite-coated QCMs. Depending on the type of zeolite coating, the resonance frequency response to vapor pulses could be increased up to 500-fold compared to the bare QCM. The regular micropores (0.3-0.8 nm) of the QCM-attached zeolite crystals were found to control molecular access into the extensive intrazeolite volume. Selectivity of the frequency response in excess of 100:1 toward molecules of different size and/or shape could be demonstrated. An additional recognition mechanism based upon intrazeolite diffusion rates was also established

Encapsulation of polyaniline in zeolite Y and mordenite

Synthetic strategies to encapsulate polyaniline in the crystalline channel system of faujasite (three-dimensional) and mordenite (one-dimensional) have been explored. The adsorption of anilinium precursor into the zeolite host and its successful oxidation to polyaniline have been studied utilizing FTIR, Fourier Transform Raman, and electronic spectroscopies. The dimensionality of the host channel system and the concentratio

EXAFS studies on the reduction of palladium(II) in X zeolites

Palladium tetraammine ion exchange into zeolite, temperature treatments under different atmospheres, and hydrogen reduction have been studied by EXAFS at the Pd Κ edge. Complete autoreduction is found to take place between 473 and 623 Κ under vacuum. Α bidisperse Pd metal phase is formed which agglomerates at the expense of the small particles upon prolonged heating at 623 Κ. In contrast, a similar treatment under oxygen suppresses autoreduction , and the Pd cations remain in zeolite coordination sites. Additional small amounts of palladium oxide are observed under these conditions. If hydrogen is admitted to the dehydrated, ionic system at 295 K. the oxygen coordination of the Pd disappears and evidence is obtained for the formation of Pd(0) dimers that interact with the framework via a long Pd-0 bond