A complex moiety containing copper (II) has been anchored covalently into the organic-modified Si-MCM-41 to prepare a new catalyst. The amine group containing organic moiety 3-aminopropyl-triethoxysilane has been first anchored on the surface of Si-MCM-41 via silicon alkoxide route. The amine group upon condensation with salicyldehyde affords a bidentate ligand in the mesoporous matrix for anchoring copper(II) ions. The prepared catalyst has been characterized by UV-vis, electron paramagnetic resonance (EPR), and infrared (IR) spectroscopic analysis, small-angle X-ray diffraction, and N2 sorption study. A remarkable difference in the pore structure has been observed after the immobilization of copper(II) complex in Si-MCM-41. The catalyst showed excellent catalytic efficiency in epoxidation reactions with various olefinic compounds including styrene and allyl alcohol, using tert-BuOOH as oxidant. Notably, styrene shows unprecedented high conversion (97%) as well as epoxide selectivity (89%) with tert-BuOOH over the Cu-MCM-41 catalyst.

Palladium(0) has been immobilized into the silica-based mesoporous material to develop catalyst Pd(0)-MCM-41, which is found to be highly active in carbon-carbon coupling reactions. [Pd(NH3)4]2+ ions have been incorporated into the mesoporous material during synthesis of MCM-41 and subsequently upon treatments with hydrazine hydrate Pd2+ ions present in mesoporous silica matrix were reduced to Pd(0) almost instantaneously. The catalyst has been characterized by small-angle X-ray diffraction, N2 sorption, and transmission electron microscopy (TEM). TEM and surface area measurements clearly demonstrate that the immobilization of Pd(0) into the mesoporous silica has a significant effect on pore structure of the catalyst. Nevertheless, after immobilization of palladium the meso-porosity of the material is retained, as evidenced in the nitrogen sorption measurement. The TEM micrograph shows that both MCM-41 and Pd(0)-MCM-41 have similar types of external surface morphology; however, Pd(0)-MCM-41 was less ordered. Pd(0)-MCM-41 showed high catalytic activity toward carbon-carbon bond formation reactions like Heck and Sonogashira coupling, as evidenced in high turn-over numbers. In contrast to many other Pd-based catalysts reported so far, Pd(0)-MCM-41 acts as a truly heterogeneous catalyst in C-C coupling reactions. Notably, the new heterogeneous catalyst is found to be efficient in the activation of arylchloride to give impressive conversion in cross coupling (15-45% for Heck and 30% for Sonogashira) reactions under mild conditions.

Nanoscale architectures have been designed by entrapping rhodamine 6G dye molecules into the channels of mesoporous silica and Au nanoparticles anchor onto the surface of the mesoporous matrix. The surface energy transfer between confined dye and Au nanoparticles has been studied by steady state and time-resolved spectroscopy. The appearance of second surface plasmon band at 680 nm with increasing the concentration of mesoporous silica indicates the formation of self-assembled structure of Au nanoparticles which is established by TEM and DLS studies. A mechanism for self-assembled Au nanoparticles is proposed. The PL quenching (76.3% to 27.4%) and energy transfer efficiency (51.8% to 17.4%) can be tuned with changing the arrangement of Au nanoparticles. Analysis reveals that the energy transfer from dye to Au nanoparticles is a surface energy transfer process and it follows 1/d 4 distance dependence. This anisotropy decay reveals that the dye molecules are aligned inside the channels of mesoporous silica. Such energy transfer between confined dye and Au nanoparticles could pave the way for designing new optical based materials for the application in chemical sensing or light harvesting system.

A new optical-based nanostructured materials having coumarin 480 dye confined within Y-zeolite and Y-zeolite functionalized Au nanoparticles has been designed for light-harvesting system. Unprecedented PL quenching (94%) of confined dye and efficient energy transfer (70%) between confined dye and Au nanoparticles are obtained. The enhanced fluorescence and large blue shift (9 nm) in the emission maximum of C480 in zeolite confirm the confinement of the probe dye molecules inside the zeolite cavity. The anisotropy study reveals that this type of supramolecular organization of the dyes inside the zeolite channels will allow light harvesting. Such nanostructured materials could be useful for efficient light-harvesting or chemical-sensing applications.