SELF-ASSEMBLY OF ALUMINUM-PILLARED CLAY ON A GOLD SUPPORT

Multilayer films of self-assembled aluminium Keggin ion pillared lapon ite and saponite have been grown layer-by-layer on a gold support. 4-A minothiophenol (4-ATP) was used for anchoring the first clay layer on the gold surface. Subsequently layers of clay and Al pillar were adsor bed by dipping the substrate into the appropriate solutions. Character ization of the films was performed by X-ray photoelectron spectroscopy (XPS), IR spectroscopy (FTIR-ERS), ellipsometric thickness measuremen ts and X-ray diffraction (XRD). XPS elemental analysis showed that bot h clay and pillar were present on the gold substrate. From the atomic film compositions, the charges on the Keggin ions were determined to b e +3 and +5 for laponite and saponite, respectively. Ellipsometry and IR spectroscopy indicated gradual and regular growth for both films. S tructural order in the synthesized films was demonstrated by X-ray dif fraction. The interlayer free spacing (IFS) was found to be 6 Angstrom by XRD, which corresponds to the increase in ellipsometric film thick ness after each aluminium layer adsorption. Aluminium-pillared laponit e films have been used as chemically sensitive films on surface acoust ic wave (SAW) devices to measure the adsorption capacity of six volati le organic compounds (VOCs). The influences of the different terminal Blm layers and calcination-induced chemical changes on the extent of a dsorption of the VOCs were investigated.