The reactions of Ga(i-Bu) 3 (i-Bu = CH 2 CH-(CH 3 ) 2 ) with the dehydrated and partially dehydroxylated surfaces of alumina (Al 2 O 3−500 ) and silica (SiO 2−700 ) were studied by IR, high field solid-state NMR and EXAFS spectroscopies, as well as elemental analysis. Grafting onto Al 2 O 3−500 occurs selectively by protonolysis at individual surface hydroxyl groups, resulting in the formation of mononuclear [(AlO)Ga(i-Bu) 2 L] (L = surface oxygen) sites as the major surface organometallic entities. Conversely, grafting on silica affords dinuclear species [(SiO) 2 Ga 2 (i-Bu) 3 ] by a combination of protonolysis and isobutyl group transfer to Si. Further evidence for the difference in nuclearity was obtained by analysis of the WT-EXAFS. The mononuclear alumina-supported Ga sites show much higher activity in propane dehydrogenation than their dinuclear silica-supported counterparts. The propane dehydrogenation reaction may require the presence of Al−O−Ga bonds to promote heterolytic C− H bond activation. Comparisons with benchmark catalysts and related systems show that the effect of the catalyst diluent is significant under the reaction conditions and must be carefully assessed in order to attribute reactivity correctly.

Self-construction of films using polyelectrolytes bearing complementary chemical groups is a recent emerging concept in the coating field. Herein, we describe the one-pot morphogen film self-construction through formation of covalent bonds between polyelectrolytes and homobifunctional spacers by Huisgen click-chemistry. One-pot solution of poly(acrylic acid) bearing alkyne groups (PAA-Alk), bisazides ethylene glycol (Az-EG n -Az) spacers and CuSO 4 was brought into contact with a gold electrode. Cu(I), the morphogen, was generated electrochemically from Cu(II) at the electrode/one-pot solution interface. The PAA-Alk/Az-EG n -Az film buildup was investigated by varying the length of the EG n spacer (n ¼ 2, 13 and 50) leading to different growth rates. By increasing the pH of the solution, a reversible swelling of the films (up to 400% for n ¼ 13 or 50) is obtained due to electrostatic repulsion between PAA chains. Further investigations on film swelling were performed by using PAA-Alk and an original bisazide spacer based on two pyrene units connected by a triamine spacer (Az-bispyrene-Az). This spacer has the property to adopt an extended conformation under acidic conditions and a ''stacked'' conformation under basic conditions, which both can be monitored by fluorimetry. Despite the mechanical tension due to film swelling at basic pH, bispyrene spacers adopt a stacked conformation. This allowed us to monitor the pH within PAA-Alk/Az-bispyrene-Az films. The pH remains fairly stable and below the pK a of PAA when the pH of the contacting solution varies from pH 5 to pH 7 and increases above pH 8, which explains why film swelling takes place essentially above pH 8.

GFP has been genetically modified at two specific positions of its molecular architecture. These modifications allow its covalent attachment onto PEG brushes grafted on functionalized silicone surfaces. The stretching of this material leads to a reversible decrease of the fluorescence intensity due to stretch-induced forces applying on GFP molecules.