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The selectivity of an Al13-pillared saponite and an Al13-pillared montmorillonite for Cd2+ and Cu2+ adsorption was investigated. Pillared clays adsorb more cadmium and copper than classic aluminum hydroxides which is because of a higher density of surface aluminum groups. A number of differences in behavior were seen between pillared montmorillonite and pillared saponite. Pillared montmorillonite is more acidic, which is correlated with a more advanced degree of structural modification of the pillars on calcination.

The microporosity of Al13-intercalated and -pillared synthetic saponites with variable layer charge was investigated by high-resolution quasi-equilibrium adsorption volumetry and low-temperature adsorption microcalorimetry. Results indicated a strong correlation between adsorbed quantities of nitrogen and argon, and the amount of intercalated aluminum. This indicates that a simple micropore-filling procedure cannot interpret N2 and Ar adsorption on intercalated and pillared clays.

We investigated the mechanism of enzyme immobilization on silanized surfaces through coupling agents (cross-linkers) in order to understand the role of these molecules on interfacial processes and their effect on catalytic activity. To this end, we used a model multimeric enzyme (G6PDH) and several cross-linking molecules with different chemical properties, including the nature of the end-group (-NCO, -NCS, -CHO), the connecting chain (aliphatic vs aromatic), and geometrical constraints (meta vs para-disubstituted aromatics). There did not seem to be radical differences in the mechanism of enzyme adsorption according to the linker used as judged from QCM-D, except that in the case of DIC (1,4-phenylene diisocyanate) the adsorption occurred more rapidly. In contrast, the nature of the cross-linker exerted a strong influence on the amount of enzyme immobilized as estimated from XPS, and more unexpectedly on the stability of the underlying silane layer. DIC, PDC (1,4-phenylene diisothiocyanate), or GA (glutaraldehyde) allowed successful enzyme immobilization. When the geometry of the linker was changed from 1,4-phenylene diisothiocyanate to 1,3-phenylene diisothiocyanate (MDC), the silane layer was subjected to degradation, upon enzyme adsorption, and the amount of immobilized molecules was significantly lowered. TE (terephtalaldehyde) and direct enzyme deposition without cross-linker were similar to MDC. The organization of immobilized enzymes also depended on the immobilization procedure, as different degrees of aggregation were observed by AFM. A correlation between the size of the aggregates and the catalytic properties of the enzyme was established, suggesting that aggregation may enhance the thermostability of the multimeric enzyme, probably through a compaction of the 3D structure.

In this work the mechanism of (3-aminopropyl)triethoxysilane (APTES) interaction with silicon surfaces is investigated at the molecular level. We studied the influence of experimental parameters such as time, temperature, and concentration on the quality of the APTES layer in terms of chemical properties, morphology, and stability in aqueous medium. This was achieved using a highly sensitive IR mode recently developed, grazing angle attenuated total reflection (GA-ATR). This technique provides structural information on the formed APTES layer. The topography of this layer was investigated by atomic force microscopy in aqueous medium. The hydrophilicity was also studied using contact angle measurement. Combining these techniques enables discussion of the mechanism of silane grafting. Considerable differences were observed depending on the reaction temperature, room temperature or 90 °C. The data suggest the presence of two adsorption sites with different affinities on the oxidized silicon layer. This also allows the optimal parameters to be established to obtain an ordered and stable silane layer. The adsorption of proteins on the APTES layer was achieved and monitored using in situ quartz crystal microbalance with dissipation monitoring and ex situ GA-ATR analyses.