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Quartz has been widely used as a bulk material in optics, the microelectronic industry, and sensors. The nanostructuring and direct integration of oriented quartz crystals onto a semiconductor platform has proven to be challenging. However, here, a new approach is presented to integrate epitaxial quartz films with macroperforations within the range of 500 nm and 1 μm using chemical solution deposition. This method constitutes an appealing approach to develop piezoelectric mass sensors with enhanced resonance frequencies due to the thickness reduction. Perforated quartz films on (100)-silicon are prepared from amorphous silica films deposited via dip-coating and doped with metal cations that catalyze quartz crystallization. The metal cations are also active in the formation of the macroperforations, which arise due to a phase separation mechanism. Cationic surfactant-anion-metal cation assemblies stabilize droplets of water, creating an indentation in the hydrophilic silica matrix which remains after solvent evaporation. Many cations induce phase separation, including Li+, Na+, Sr2+, Mn2+, Fe2+/Fe3+, Ca2+, Ce3+ and La3+ but only the Sr2+ and Ca2+ cations in this series induce the epitaxial growth of α-quartz films under the conditions studied. The combination of sol-gel chemistry and epitaxial growth opens new opportunities for the integration of patterned quartz on silicon. [ABSTRACT FROM AUTHOR]

Abstract: We report the singular filtration properties of an ultrafiltration membrane made with mesoporous silica that exhibits cylindrical pores aligned mostly normal to the support. This membrane supported on tubular commercial macroporous alumina supports was prepared by the interfacial growth mechanism between stable silica–surfactant hybrid micelles made of the association of silica oligomers with polyethyleneoxide-based (PEO) surfactants and sodium fluoride, a well-known silica condensation catalyst [Boissière et al., An ultrafiltration membrane made with mesoporous MSU-X silica, Chem. Mater. 15 (2003) 460–463]. It appears that the combined effect of the silica nature of the membrane, whose surface charge can be easily adjusted by changing the pH and the non-connected cylindrical shape of the pores provides a new behavior in the retention properties, as proved by the filtration of polyoxyethylene polymers (PEO) with different molecular weights. Depending on the filtration conditions, a rejection rate of 80% and a steep cut-off at 2000Da can be obtained or, on the reverse, polymers three times bigger than the pore diameter can diffuse through the membrane. This new filtration mechanism, which opens up new modes of separation modes, is explained in the light of both topology of the porous network and pH-dependent interactions between PEO polymers and silica porous media. [Copyright &y& Elsevier]

Abstract: We present a general review on the synthesis of mesoporous silica obtained with nonionic surfactants and bloc-copolymers as templates. This silica, referred as MSU silica, was obtained by a two-step process that led to the formation of stable hybrid micelles after a first stage of assembling between silica and surfactants, followed by the fluoride-catalyzed condensation of silica. This process allows some unique features: the final pore size can be adjusted with some synthesis parameters such as temperature or amount of catalyst, the particle shape is spherical and in the micrometric range, different shapes and nanostructures can be achieved, including hexagonal-like frameworks. Finally, we demonstrate how an accurate control of the synthesis itself may allow us to adapt this synthesis for applications dedicated to separation processes, including liquid filtration of HPLC chromatography. To cite this article: É. Prouzet, C. Boissière, C. R. Chimie 8 (2005). [Copyright &y& Elsevier]

A novel technique combining inkjet printing (IJP), evaporation-inducedself-assembly (EISA), and click chemistry is implemented for elaboratingmesoporous silica-based multifunctional microdots arrays. The microdotsare in situ azide-functionalized with (3-azidopropyl)triethoxysilane(AzPTES). AzPTES is directly added to the initial sol before IJP andco-condenses with the silica precursor (TEOS) during the evaporation-inducedself-assembly (EISA) of micelles on the substrate. After extractingthe surfactants to release the porosity, model alkynes, namely propargylalcohol, methyl pent-4-ynoate, ethynylferrocene, and N-propargyl-4-amino-1,8-naphthalimide, are grafted by the azide–alkyneCuAAC click reaction. The demonstration is established that the clickreaction is nearly quantitative and occurs in the whole volume ofthe microdots attesting the accessibility of the azide groups. Byintegrating an alkyne-containing silylated precursor in a similarroute, azide-containing functional groups are anchored in the microdotsby click reaction. A demonstration of the multifunctionalization ofsuch microdots arrays is achieved by reacting clickable dyes on alternatealkyne- and azide-functionalized lines of microdots, as evidencedby confocal fluorescence microscopy. Such multifunctional mesoporoussilica microdots arrays offer promising perspectives for biosensingapplications. [ABSTRACT FROM AUTHOR]