Ion-exchange properties of imidazolium-grafted SBA-15 toward AuCl4(-) anions and their conversion into supported gold nanoparticles.

Imidazolium groups were successfully prepared and grafted on the surface of SBA-15 mesoporous silica. The ion-exchange properties of the functionalized porous solid (SBA-15/R(+)Cl(-)) toward AuCl(4)(-) anions were evaluated through an ion-exchange isotherm. The calculated values of the equilibrium constant (log ß = 4.47) and the effective ion-exchange capacity (t(Q) = 0.79 mmol g(-1)) indicate that the AuCl(4)(-) species can be loaded and strongly retained on the functionalized surface as counterions of the imidazolium groups. Subsequently, solids containing different amounts of AuCl(4)(-) ions were submitted to a chemical reduction process with NaBH(4), converting the anionic gold species into supported gold nanoparticles. The plasmon resonance bands, the X-ray diffraction patterns, and transmission electron microscopy images of the supported gold nanoparticles before and after thermal treatment at 973 K indicate that the metal nanostructures are highly dispersed and stabilized by the host environment.

Highly-controlled grafting of mono and dicationic 4,4'-bipyridine derivatives on SBA-15 for potential application as adsorbent of CuCl2 from ethanol solution.

This work describes a highly controlled post-grafting of mono and dicationic 4,4'-bipyridine alkoxysilane derivatives (Bipy(+) and Bipy(2+)) onto the surface of an ordered mesoporous silica, SBA-15. The materials obtained are designated as SBA-15/Bipy(+)Cl(-) and SBA-15/Bipy(2+)Cl(2)(-), both possessing chloride as counter ion. The regular arrangement of uniform pores of this inorganic matrix is likely to ensure good accessibility to the active centers (electron acceptors) attached to the surface. The materials are excellent adsorbents due to the ability of the functional groups to retain copper chlorides on their surfaces as anionic complexes (CuCl(2+n)(n-)) in ethanol. From the adsorption, results it was possible to probe the functional surface monolayer of the materials, which present a highly homogenous distribution of functional groups inside the ordered SBA-15 channels, with an exchange efficiency of 93% for SBA-15/Bipy(+)Cl(-) and 94% for SBA-15/Bipy(2+)Cl(2)(-). Both adsorbent materials are potentially useful in the pre-concentration and further analysis of Cu(II) present in trace amounts in ethanol, extensively used as an automotive fuel in Brazil.