Lamellar Mesopores Research Articles

Helical mesoporous organic–inorganic hybrid silica nanofibers prepared using a TPE-based silane for explosive detection

Helical mesoporous organic–inorganic hybrid silica nanofibers with blue fluorescence were synthesized by co-condensation of 1,2-bis(triethoxysilyl)ethane and tetraphenylethylene (TPE)-containing triethoxysilane with aggregation-induced emission (AIE) property. The pore channels of the hybrid silicas were arranged in a hexagonal structure. Lamellar mesopores were identified on the surfaces of the nanofibers. The fluorescence quantum yields increased with increasing the TPE weight ratio. These hybrid silicas exhibit sensitive fluorescence quenching responses towards the nitroaromaticexplosivepicric acid. This is ascribed to the ordered mesoporous structure which helps guest molecules to enter the pores quickly and interact with TPE chromophore.

Preparation and characterization of helical carbon/silica nanofibers with lamellar mesopores on the surfaces

Abstract Helical 1,2-ethylene–silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like mesopores inside were prepared according to literature procedures. After carbonization, helical carbon/silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were obtained. The morphologies and pore architectures of the carbon/silica nanofibers were characterized using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction and N 2 sorptions. Although the mesopores inside shrank into micropores, the helical nanostructure remained. Moreover, several carbon/silica nanofibers with lamellar mesopores on the surfaces and concentric circular micropores inside were also obtained. After being calcined in air, helical silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were produced as well.

Formation of silica multilamellar vesicles through dual-templating

Silica multilamellar vesicles were prepared with a dual-templating approach using cetyltrimethylammonium bromide (CTAB) and 2-(perfluoro-n-octyl)ethanol (PFOE). The number of layers of the lamellar mesopores increased with increasing PFOE/CTAB molar ratio from 0.2:1 to 0.7:1. When the PFOE/CTAB molar ratios were 0.2:1 and 0.4:1, worm-like pore channels were identified near the outer surfaces, and shrunk lamellar silica shells were identified near the inner surfaces, of the shells of the vesicles. The formation of the mesopores was studied by taking TEM images after different reaction times. It was found that the multilamellar vesicles served as the templates for the lamellar mesopores and the “nucleation” sites for growing silica/surfactant micelles.

Preparation and characterizations of helical mesoporous silica nanorods using CTAB and alcohols

Abstract Helical mesoporous silica nanorods were prepared using cetyltrimethylammonium bromide and achiral alcohols as the co-structure-directing agents. They were characterized using field-emission scanning electron microscopy, transmission electron microscopy, nitrogen sorptions, and small angle X-ray diffraction. The length of the silica nanorods increases with increasing the length of the alcohols. When n -heptanol and n -octanol were used, helical mesoporous silica nanorods with lamellar mesopores on the surfaces were obtained.

Formation of Ethylene–Silica Nanofibers with Concentric Circular Mesopores Inside and Lamellar Mesopores on the Surfaces

Ethylene-silica nanofibers with concentric circular mesopores inside and lamellar mesopores outside were prepared using stearyltrimethylammonium bromide (STAB) as template and (S)-beta-citronellol as a co-structure-directing agent. They were formed at the (S)-beta-citronellol/STAB molar ratio range of 3:1 to 4:1. Field emission scanning electron microscopy and transmission electron microscopy images taken after different reaction times revealed a phase transition from hexagonal to lamellar phase on the surface of the organic-inorganic hybrid silica nanofibers. The nanofibers with concentric circular pore channels were proposed to be formed from spherical micelles. With increasing the (S)-beta-citronellol/STAB molar ratio from 0.5:1 to 5:1, the morphology changed from short hexagonal rod to long nanofiber, and then to shrunk multilamellar vesicle. Moreover, 1,4-phenylene-silica nanofibers and nanoparticles with concentric circular mesopores inside and lamellar mesopores outside were also prepared.

Preparation of Hierarchical Mesoporous Silica Nanoparticles through a Single‐Templating Approach

AbstractSilicas with hierarchical porous architectures attracted much attention, due to their potential applications in catalysis and separation. Generally, they were prepared through dual‐ or triple‐templating approaches. Herein, mesoporous silica nanoparticles with rod‐like pore channels inside and lamellar mesopores on the surfaces were prepared using the self‐assemblies of a chiral low‐molecular‐weight amphiphile as templates through a single‐templating approach. The formation of the lamellar mesopores was studied by taking field‐emission scanning electron microscopy and transmission electron microscopy images after different reaction times. The lamellar pores were proposed to be formed by merging rod‐like micelles during the sol‐gel process. Moreover, helical nanofibers with rod‐like pore channels inside and lamellar mesopores on the surfaces were prepared with the addition of n‐octanol as a co‐structure‐directing agent.

From Nanotubes to Nano-Cocoons with Coiled Pore Channels

Silica nanotubes with coiled pore channels and hollow spheres with coiled or concentric circular pore channels have been prepared using the self-assemblies of chiral cationic amphiphiles as templates. However, the relationship among these morphologies and pore architectures has not been well studied. For a better understanding the relationship, silica nanostructures were systematically prepared by tuning the reaction conditions. With increasing the stirring rate, silica nanotube with coiled pore channels changed to linked nano-cocoon with coiled pore channels. With increasing the concentration of the reaction mixture, the morphology changed from sphere to linked cocoon, and then to nanorod with lamellar mesopores on the surface. Transmission electron microscopy images taken after different reaction times indicated a cooperation mechanism.

Preparation of Helical Mesoporous Ethenylene‐silica Nanofibers with Lamellar Mesopores on Their Surface

AbstractThe morphologies and pore architectures of mesoporous ethenylene‐silica were controlled using cetyltrimethylammonium bromide (CTAB) as template and (S)‐β‐citronellol as a co‐structure‐directing agent under basic conditions. When the (S)‐β‐citronellol/CTAB molar ratios are in the range of 0.75–2.0, helical nanofibers were obtained. With increasing the (S)‐β‐citronellol/CTAB molar ratio, the lengths of the nanofibers increases. Lamellar mesopores were identified on the surfaces of the nanofibers prepared in the (S)‐β‐citronellol/CTAB molar ratio range of 1.5–2.0. At the (S)‐β‐citronellol/CTAB molar ratio of 2.5:1, nanoparticles with nanoflakes on the surfaces were obtained. The field emission scanning electron microscopy images taken after different reaction times indicated that the helical pitches of the nanofibers decreased with increasing the reaction time. Helical 1,4‐phenylene‐silica and methylene‐silica nanofibers were also prepared. The results indicated that the morphologies and pore architectures of the obtained organic‐inorganic hybrid silicas are also sensitive to the hybrid silica precursors. Helical ethenylene‐silica nanofibers with lamellar mesopores on their surfaces can be also prepared using the mixtures of CTAB and racemic citronellol within a narrower citronellol/CTAB molar ratio range.

Structural Control of Mesoporous 1,4‐Phenylene‐silica Using the Mixture of CTAB/SDS

AbstractThe morphology, pore architecture and crystallinity of the mesoporous 1,4‐phenylene‐silicas were controlled using the mixtures of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS). When the SDS/CTAB molar ratio increased from 0 to 1.0, the morphology of the mesoporous 1,4‐phenylene‐silicas changed in a sequence of sphere, hexagonal short rod, worm‐like, bent flake and flower‐like structure; the pore architecture of them changed from a hexagonal arranged tubular structure to a lamellar one; and the organization of the smallest repeat units within the wall changed from a random structure to a crystalline structure. At the SDS/CTAB molar ratios of 0.3 and 0.5, 1,4‐phenylene‐silica nanofibers with lamellar mesopores outside and tubular pore channels inside were obtained. The lamellar mesopores should be formed by merging the rod‐like micelles during the reaction process.

Preparation of helical mesoporous ethylene–silica nanofibers using CTAB and ( S)-2-methyl-1-butanol

The morphology and pore architecture of mesoporous ethylene–silicas were controlled using cetyltrimethylammonium bromide (CTAB) as the template and ( S)-2-methyl-1-butanol (MB) as a co-structure-directing agent. X-ray diffraction, nitrogen sorption, field emission scanning electron microscopy and transmission electron microscopy techniques have been used to characterize the ethylene–silicas. When the MB/CTAB molar ratio is 20, mesoporous nanoparticles with lamellar mesopores on their surfaces were identified. Helical nanofibers were obtained at the MB/CTAB molar ratios of 0.5–10. Although MB could not drive the formation of single-handed helical nanofibers, with increasing the MB/CTAB molar ratio, the diameter and the helical pitch of the mesoporous ethylene–silica nanofibers decreased and the pore size increased.

Preparation of helical mesoporous ethylene–silica nanofibers with lamellar mesopores on the surfaces

Helical ethylene-silica nanofibers with chiral pore channels inside and lamellar pores on the surfaces were prepared using cetyltrimethylammonium bromide and (S)-beta-citronellol as a co-structure-directing agent under basic conditions, the formation mechanism of which was studied by taking field-emission scanning electron microscopy images after different reaction times.

Synthesis of silica particles with lamellar and wormhole-like bi-modal mesopores using anionic surfactant as the template

Silica particles with lamellar and wormhole-like bi-modal mesopores have been synthesized using anionic surfactant (N-lauroylsarcosine sodium) as the template. The particles with diameters of 300–500 nm possess bi-modal mesopores with pore sizes of 3 nm and 12 nm, which were ascribed to the disordered wormhole-like mesophase and lamellar mesophase, respectively. The BET surface area of the particles was 536 m2/g and the pore volume was 0.83 cm3/g. The lamellar mesophase and cylindrical mesophase were formed due to the co-assembly of the anionic surfactant and its protonized polar oil.

Separation of alkylbiphenyls

Helical mesoporous organic–inorganic hybrid silica nanofibers with blue fluorescence were synthesized by co-condensation of 1,2-bis(triethoxysilyl)ethane and tetraphenylethylene (TPE)-containing triethoxysilane with aggregation-induced emission (AIE) property. The pore channels of the hybrid silicas were arranged in a hexagonal structure. Lamellar mesopores were identified on the surfaces of the nanofibers. The fluorescence quantum yields increased with increasing the TPE weight ratio. These hybrid silicas exhibit sensitive fluorescence quenching responses towards the nitroaromatic explosive picric acid. This is ascribed to the ordered mesoporous structure which helps guest molecules to enter the pores quickly and interact with TPE chromophore.