a b s t r a c tDevelopment of new zeolite based materials is essential for a variety of applications in catalysis, separations, and medicine. Increasing the specific surface area and decreasing the micropore diffusion pathlength in zeolites are important factors for improving the performance of zeolites in catalytic applications and these factors can be optimized by decreasing the zeolite particle size. Creation of a hierarchical zeolite material that possesses both micro-and mesopores with very large surface areas and improved mass transport properties is an effective solution. In this study, a facile approach to a one step synthesis of nanocrystalline ZSM-5 zeolite from a single template system in 12-24 h at 140°C and with high yield is presented. ZSM-5 zeolite crystals as small as 6 nm which form mesoporous aggregates of approximately 200 nm in diameter were synthesized using this method. The mesopore volume and size distribution showed a dependence on particle size such that smaller particles lead to higher mesopore volumes and narrower pore size distributions. The size of individual crystals, as well as mesopore surface area and pore volume can be controlled by adjusting the pH of the reaction mixture, as well as the hydrothermal treatment temperature and duration.

In this report, we describe the synthesis and characterization of nanocrystalline silicalite (the purely siliceous form of the zeolite, ZSM-5) of defined crystal size and surface functionalization and determine the effect on the type and degree of cytotoxicity induced in two distinct model cell lines. The silicalite materials were characterized by powder X-ray diffraction, dynamic light scattering and zeta potential, solid state NMR, thermal gravimetric analysis, and nitrogen adsorption using the BET method to determine specific surface area. The silicalite samples were functionalized with amino, thiol, and carboxy groups and had crystal sizes of approximately 30, 150, and 500 nm. The cytotoxicities of the silicalite samples with different crystal sizes and different surface functional groups were investigated using human embryonic kidney 293 (HEK-293) cells and RAW264.7 macrophage cell lines. We used the lactic dehydrogenase release assay to measure damage to the cell membrane, the caspase 3/7 activity assay to measure key molecules involved in apoptosis, and the Annexin V-propidium iodide staining method to provide visual confirmation of the types of cell death induced. We have shown that the impact of size and surface functionalization of silicalite nanoparticles on cell toxicity and mechanism of cell death is cell type-dependent. Thirty nanometer silicalite nanoparticles were nontoxic in RAW264.7 cells relative to untreated controls but caused necrosis in HEK293 cells. Carboxy-functionalized 500 nm silicalite nanoparticles resulted in apoptosis and necrosis in RAW264.7 cells and predominantly activated apoptosis in HEK293 cells.

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As part of our recent effort to attach well-defined molecular photocatalysts to solid-state surfaces, this present study investigates adsorption and photochemical properties of a tricarbonyl rhenium(I) compound, Re(bpy)(CO)3Cl (bpy = 2,2'-bipyridine), in hierarchical mesoporous ZSM-5. The molecular Re(I) catalyst, a Ru(bpy)3(2+) photosensitizer, and an amine-based electron donor were coadsorbed in the mesopores of the hierarchical ZSM-5 through simple liquid-phase adsorption. The functionalized ZSM-5 was then characterized with infrared and UV-visible spectroscopies and was tested in CO2 reduction photocatalysis at the gas-surface interface. In the mesoporous ZSM-5, CO2 molecules were adsorbed on the amine electron-donor molecules as bicarbonate, which would release CO2 upon light irradiation to react with the Re(I) catalyst. The formation of important reaction intermediates, particularly a Re-carboxylato species, was revealed with in situ Fourier transform infrared spectroscopy in combination with isotopic labeling. The experimental results indicate that hierarchical mesoporous zeolites are promising host materials for molecular photocatalysts and that zeolite mesopores are potential "reaction vessels" for CO2 reduction photocatalysis at the gas-solid interface.