Silica films with a single-crystalline mesoporous structure
ABSTRACT Films of mesoporous materials attract broad interest because of their wide applicability in the fields of optics and electronics. Although many of these films have a regular local porous structure, the structural regularity has not been used practically yet because of difficulties in its control on macroscopic scales. Here, we demonstrate the preparation of mesoporous silica films whose porous structure can be described as a single crystal, that is, a long-range order of cage-like pores is maintained over centimetre scales. These films have a three-dimensional hexagonal (space group P6(3)/mmc) porous structure, and the in-plane arrangement of the pores is strictly controlled by a polymeric substrate surface that has been treated by rubbing. This new class of single-crystalline films with mesoscopic periodic structure is a significant breakthrough in bottom-up nanotechnology, and could lead to novel devices, for example, optics in a soft X-ray region, and quantum electronics.
- SourceAvailable from: Emad A Elshehy
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- "Mercury ions undergo a series of biogeochemical transformations to toxic chemical species   . The toxicity of Hg 2+ mainly arises from its high binding affinity for thiol (–SH) and amino (–NH 2 ) groups of proteins , and may contribute to adverse effects on the central nervous system , pulmonary kidney functions, chromosomes, and the immune system . Although copper is essential for the human body metabolism at a trace level, exposure to high levels of copper leads to eye and skin irritations. "
ABSTRACT: The design of a simple, pH-dependent, micro-object optical sensor based on mesoporous Ia3d aluminosilica pellets functionalized by a porphyrinic chelating ligand for the monitoring and removal of ultra-trace levels of toxic metals, such as Hg(II), Cu(II), and Cd(II), from aqueous media, such as drinking water and biological fluids, is described in this study. This micro-object optical sensor has large surface area-to-volume ratios and uniformly shaped pores in three-dimensional (3D) nanoscale gyroidal structures, and its active sites consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures. These mesostructures are densely coated with chelating ligand to permit ultra-fast, specific, pH-dependent visualization and the removal of toxic metals at sub-picomolar concentrations (∼10−11 mol dm−3) from aqueous media, including drinking water and a suspension of red blood cells, via a colorimetric signal visible to the naked eye, as well as via UV–Vis reflectance spectroscopy. The adsorption of metal ions forms a monolayer on the interior pore surfaces of the pellets in this sensor system. Given that the pellets exhibit long-term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be useful for the fabrication of inexpensive sensor devices for naked-eye detection of toxic pollutants. Furthermore, the usage of the pellets to remove metal ions from a physiological fluid (i.e., blood cells) was evaluated.Separation and Purification Technology 09/2013; 116:73–86. DOI:10.1016/j.seppur.2013.05.011
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- "The maximum stress concentration factor k(R) at the boundary of a circular nano-pore of radius R in a plate under uniaxial tension is kðRÞ kðNÞ Z 1K 7ðl l C 2l m Þ 3R ; ð3:3Þ where k(N)Z3 is the classical elasticity result. The transverse Young modulus E T (R) of a nanochannel-array material containing parallel cylindrical nano-pores (Masuda & Fukuda 1995; Miyata et al. 2004 "
ABSTRACT: In this brief communication, we identify intrinsic length scales of several physical properties at the nano-scale and sho that, for nano-structures whose characteristic sizes are much larger than these scales, the properties obey a simple scalin law. The underlying cause of the size-dependence of these properties at the nano-scale is the competition between surfac and bulk energies. This law provides a yardstick for checking the accuracy of experimentally measured or numerically compute properties of nano-structured materials over a broad size range and can thus help replace repeated and exhaustive testin by one or a few tests.Proceedings of The Royal Society A 05/2006; 462(2069):1355-1363. DOI:10.1098/rspa.2005.1637
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ABSTRACT: Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m2g−1) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20nm or 20–30nm silica colloids as templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450°C resulted in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created mesopores in the TiO2 nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity and crystallites’ growth at a higher calcination temperature (e.g., 1000°C) were investigated. Silica colloids suppressed the growth of TiO2 crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N2 sorption.Journal of Sol-Gel Science and Technology 02/2009; 53(2):287-292. DOI:10.1007/s10971-009-2089-9