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Shunai Che

Publications and source records attributed to Shunai Che.

11 recordsLinked to original sources
PubMed2006

Chiral mesoporous materials based on the self-assembly.

Ordered mesoporous materials with various structures are synthesized based on the self-assembly of surfactant and inorganic precursors and covered by several excellent reviews. However, less work has been directed to chiral structured mesoporous materials, although these could have wide-ranging applications on the manufacturing of enantio-pure chemicals and pharmaceuticals as catalysts and separation media with both shape selectivity and enantioselectivity. This short review will address the synthesis of chiral mesoporous materials by chiral organic compounds templating route, covering single and 2-dimensional ordered chiral channel mesoporous materials. Non-porous helical fiber, atomic-scale enantio-morphism and zeolite-like materials with three-dimensional helical pores are beyond the scope of this paper.

Macromolecular Substances↗
PubMed2005

Characterization of chiral mesoporous materials by transmission electron microscopy.

By using transmission electron microscopy (TEM), the chirality of novel mesoporous materials has been studied. In addition, a computer simulation that uses a simple structural model was employed. The existence of chiral channels inside a tubelike material was confirmed by the observation of fringes along the length of the tubes. The chiral pitch of the channels was measured from the intermittent period, the chirality (right- or left-handed) was determined from the tilt direction of a tube compared with the direction of incident electrons and the curvature direction of the curved intermitted fringes as viewed in the TEM images.

Absorption↗
PubMed2004

Synthesis and characterization of chiral mesoporous silica.

Chirality is widely expressed in organic materials, perhaps most notably in biological molecules such as DNA, and in proteins, owing to the homochirality of their components (d-sugars and l-amino acids). But the occurrence of large-scale chiral pores in inorganic materials is rare. Although some progress has been made in strategies to synthesize helical and chiral zeolite-like materials, the synthesis of enantiomerically pure mesoporous materials is a challenge that remains unsolved. Here we report the surfactant-templated synthesis of ordered chiral mesoporous silica, together with a general approach for the structural analysis of chiral mesoporous crystals by electron microscopy. The material that we have synthesized has a twisted hexagonal rod-like morphology, with diameter 130-180 nm and length 1-6 micro m. Transmission electron microscopy combined with computer simulations confirm the presence of hexagonally ordered chiral channels of 2.2 nm diameter winding around the central axis of the rods. Our findings could lead to new uses for mesoporous silica and other chiral pore materials in, for example, catalysis and separation media, where both shape selectivity and enantioselectivity can be applied to the manufacturing of enantiomerically pure chemicals and pharmaceuticals.

Journal Article↗
PubMed2003

A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure.

Anionic surfactants are used in greater volume than any other surfactants because of their highly potent detergency and low cost of manufacture. However, they have not been used as templates for synthesizing mesoporous silica. Here we show a templating route for preparing mesoporous silicas based on self-assembly of anionic surfactants and inorganic precursors. We use aminosilane or quaternized aminosilane as co-structure-directing agent (CSDA), which is different from previous pathways. The alkoxysilane site of CSDA is co-condensed with inorganic precursors; the ammonium site of CSDA, attached to silicon atoms incorporated into the wall, electrostatically interacts with the anionic surfactants to produce well-ordered anionic-surfactant-templated mesoporous silicas (AMS). These have new structures with periodic modulations as well as two-dimensional hexagonal and lamellar phases. The periodic modulations may be caused by the coexistence of micelles that differ in size or curvature, possibly owing to local chirality. These mesoporous silicas provide a new family of mesoporous materials as well as shedding light on the structural behaviour of anionic surfactants.

Anions↗
PubMed2002

The effect of the counteranion on the formation of mesoporous materials under the acidic synthesis process.

The presence of various counteranions at the interfacial region of the silicate-surfactant mesophase introduces opportunities for manipulation of the phase structure. Well-ordered 3D-hexagonal P63/mmc, cubic Pmn, 2D-hexagonal p6mm, and cubic Iad mesoporous materials have been synthesized with the same surfactant, cetyltriethylammonium bromide, in the presence of various acids. The counteranions of acidic media have resulted in increasing the surfactant packing parameter g in the order SO42- < Cl- < Br- < NO3-, which leads to the different time course of formation of mesostructures. The effect of counteranions on the formation of mesostructures is explained in terms of not only the adsorption strength on the headgroups of the surfactant micelle but also the rate of silica condensation affecting the charge density matching between the surfactant and silica. It has been found that the mesophase is always transformed from the larger g parameter into the smaller one. The distinct morphologies of the 3D-hexagonal P63/mmc mesophases have been rationally explained by supposing this particular mesostructure. The cubic Iad phase has been first synthesized under acidic conditions.

Journal Article↗