Periodic Mesoporous Organosilica Hollow Spheres with Tunable Wall Thickness

3D hierarchically ordered composite block copolymer hollow sphere arrays by solution wetting

Hierarchically ordered 3D arrays of block copolymer hollow spheres have been fabricated by using solution wetting of silica inverse colloidal crystals. Subsequent drying and annealing in the molten state yield nanopatterned shells due to the microphase separation of the block copolymers. The shell thickness can be controlled by properly selecting the polymer solution concentration, and the nanostructures inside the shells can be manipulated by varying molecular weights and/or compositions of the block copolymers. This versatile strategy can be readily applied to fabricate patterned metal (gold and palladium) nanoparticles inside the shells of the highly ordered hollow spheres. Thus, the locally ordered nanostructures of block copolymers are integrated into long-range 3D order defined by the silica inverse colloidal crystal templates, promising convenient fabrication of highly integrated devices.

Interfacially controlled synthesis of hollow mesoporous silica spheres with radially oriented pore structures

This paper reports an alternative process to prepare hollow mesoporous silica spheres (HMS) using a single cationic surfactant with a tunable wall thickness and radially oriented pore structures. Using N,N-dimethylformide (DMF) as the intermediate solvent bridging the organic and aqueous phase, hollow mesoporous silica spheres were synthesized with interfacial hydrolysis reactions at the surface of liquid droplets. These spheres have an ordered pore structure aligned along the radial direction, and the wall thickness and sphere sizes can be tuned by adjusting the experimental conditions. Transmission electron microscopy and nitrogen absorption techniques were used to characterize HMS and its formation procedure. A hypothetic formation mechanism was proposed on the basis of a morphology transformation with the correct amount of DMF and a careful observation of the early hydrolysis stages. Au and magnetic Fe(3)O(4) nanoparticles have been encapsulated in the HMS hollow core for potential applications.

Fine-tuning of silica nanosphere structure by simple regulation of the volume ratio of cosolvents

Silica nanospheres with varied morphologies and pore structures, including mesoporous nanospheres, nanospheres with hierarchical pores (from 2 to 100 nm), and hollow nanospheres of mesoporous shell, were fabricated at room temperature simply by regulating the ethanol/ethyl ether volume ratio in the starting solution. The silica nanostructures were characterized by small-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurements. Based on experimental results, a plausible mechanism for the structural regulation of mesoporous silicas has been put forward. These novel nanostructures of hierarchical pores provide an ideal scaffold for biological, medical, and catalytic applications.

Functionalized periodic mesoporous organosilicas for enhanced and selective peptide enrichment

The analysis of peptides by the mass spectrometry (MS) technique is important in modern life science. The enrichment of peptides can increase the detection efficiency and is sometimes indispensable for collecting the information on proteins with low-abundance. Herein, we first report that functionalized periodic mesoporous organosilica (PMO) materials have a superior peptide enrichment property. It is demonstrated that the PMO materials with an organo-bridged (-CH(2)-) hybrid wall composition display a highly enhanced peptide enrichment ability compared to the pure silica material (SBA-15) with similar mesostructured parameters and morphology. More importantly, by surface modification of PMO with amino groups (denoted NH(2)-PMO), PMO and NH(2)-PMO with opposite charged surfaces (-25.2 and +39.0 mV, respectively) show selective affinities for positively and negatively charged peptides, respectively. By directly adding PMO, NH(2)-PMO as well as pure silica materials to the peptides solution with a low concentration (1-2 fmol/microL), 36 and 28 peptides can be detected from the BSA digestion in the presence of PMO and NH(2)-PMO, respectively, while only 6 and 4 are monitored in the case of SBA-15 enrichment and from solution without enrichment, respectively. Moreover, 69.4% (25 of 36) of enriched peptides by PMO have pI > or = 6 and 80% (21 of 28) of enriched peptides by NH(2)-PMO possess pI < or = 6. Combining the results from the NH(2)-PMO and PMO enrichment together, 51 peptides can be identified with a MOWSE score of 333. It is also noted that similar conclusions can also be obtained from the peptides solution originated from other proteins. This might be an important contribution to the understanding of the interaction between peptides and porous hosts, and the proposed method is promising for the development of both material science and biotechnology.

Recent progress on silica coating of nanoparticles and related nanomaterials

In recent years, new strategies for silica coating of inorganic nanoparticles and organic nanomaterials, which differ from the classical methodologies, have emerged at the forefront of materials science. Silica as a coating material promises an unparalleled opportunity for enhancement of colloidal properties and functions by using core-shell rational designs and profiting from its synthetic versatility. This contribution provides a brief overview of recent progress in the synthesis of silica-coated nanomaterials and their significant impact in different areas such as spectroscopy, magnetism, catalysis, and biology.

Titanate-silica mesostructured nanocables: synthesis, structural analysis and biomedical applications

1D hierarchical composite mesostructures of titanate and silica were synthesized via an interfacial surfactant templating approach. Such mesostructures have complex core-shell architectures consisting of single-crystalline H(2)Ti(3)O(7) nanobelts inside the ordered mesoporous SiO(2) shell, which are nontoxic and highly biocompatible. The overall diameter of as-prepared 1D hierarchical composite mesostructures is only approx. 34.2 nm with a length over 500 nm on average. A model to explain the formation mechanism of these mesostructures has been proposed; the negatively charged surface of H(2)Ti(3)O(7) nanobelts controls the formation of the octadecyltrimethylammonium bromide (C(18)TAB) bilayer, which in turn regulates the cooperative self-assembly of silica and C(18)TAB complex micelles on the interface to produce a mesoporous silica shell. More importantly, the application of synthesized mesostructured nanocables as anticancer drug reservoirs has also been explored, which indicates that the membranes containing these mesoporous nanocables have a great potential to be used as transdermal drug delivery systems.

Polymer-mesoporous silica materials templated with an oppositely charged surfactant/polymer system for drug delivery

In this paper, polymer-mesoporous silica nanoparticles have been synthesized by a dual-template technology. Cationic polymer quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] (PEPU) and anionic surfactant sodium dodecyl sulfate (SDS) were used to form a homogeneous comicelle system to induce mesoporous silica spherical nanoparticles with diameters of 50-180 nm. The formation mechanism was studied by transmission electron microscopy (TEM), which suggested that PEPU played a cotemplate role in the synthesis process, and no mesoporous structure was generated without it. After removing the anionic surfactant, SDS, by an ion-exchange method, the cationic polymer-mesoporous silica nanoparticles were obtained. Using the materials as the host and ibuprofen (IBU)/captopril (CapH(2)) as the model drugs, the system revealed well-sustained release profiles.

Synthesis and tuning of bimodal mesoporous silica by combined hydrocarbon/fluorocarbon surfactant templating

Hydrocarbon and fluorocarbon surfactants show highly nonideal mixing that under some conditions results in demixing of the two types of surfactants into distinct populations of fluorocarbon-rich and hydrocarbon-rich aggregates. This also occurs in materials prepared by cooperative assembly of hydrolyzed tetraethoxysilane with mixtures of cetyltrimethylammonium chloride (CTAC) and 1,1,2,2-tetrahydro-perfluorodecylpyridinium chloride (HFDePC). Here, we report conditions under which demixed micelles lead to bimodal mesoporous materials (including specific concentrations of ammonia and salt in the synthesis solution) and show that the sizes of the hydrocarbon-templated and fluorocarbon-templated pores can be finely and independently controlled by adding lipophilic or fluorophilic oils, respectively. Nitrogen sorption isotherms and transmission electron microscopy provide clear evidence for a single phase of demixed but disordered wormhole-like pores.

Structure transition from hexagonal mesostructured rodlike silica to multilamellar vesicles

We studied the synthesis of siliceous structures by using a nonionic block copolymer (Pluronic P123) and perfluorooctanoic acid (PFOA) as cotemplates in an acid-catalyzed sol-gel process. Different siliceous structures were obtained through systematically varying the molar ratio (R) of PFOA/P123, and the resultant materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen sorption analysis, and Fourier-transform infrared spectroscopy. The results are consistent and reveal a structure transition from a highly ordered 2D hexagonal (HEX) mesostructure with a rodlike morphology to multilamellar vesicles (MLVs) with sharp edges when R is increased. The fact that the MLVs are initiated from the end of hexagonally mesostructured rods provides key evidence in such a novel structure transition. Our finding indicates that, at least in our observations, the MLVs are developed gradually from HEX structures, rather than by a direct cooperative self-assembly mechanism. It is suggested that PFOA molecules with rigid fluorocarbon chains closely interact with PEO. This interaction model may well explain (1) the "wall-thicken" effect in HEX mesostructures by enlarging the hydrophilic PEO moiety (R = 0-1.4), (2) the subsequent HEX to multilamellar structure transition by modifying the hydrophilic/hydrophobic volume ratio (R = 1.4-2.8), and (3) the formation of MLVs with sharp edges by increasing the bending energy. This model provides insight into the fabrication of novel porous materials by the use of block copolymers and fluorinated surfactant mixed templates.