Synthesis of surface-modified iron oxide nanocrystals using supercritical carbon dioxide as the reaction field

We applied the supercritical CO2 technology, which is an excellent solventless process, to the synthesis of surface-modified iron oxide nanocrystals.

In situ synthesized hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolytic dehydrogenation of ammonia borane

The present study investigated the fabrication of hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolitic dehydrogenation of ammonia borane.

Double Epitaxy as a Paradigm for Templated Growth of Highly Ordered Three-Dimensional Mesophase Crystals

Molecular templating and self-assembly are fundamental mechanisms for controlling the morphology of biominerals, while in synthetic two-dimensional layered materials similar levels of control over materials structure can be achieved through the epitaxial relationship with the substrate. In this study these two concepts are combined to provide an approach for the nucleation and growth of three-dimensional ordered mesophases on solid surfaces. A combined experimental and theoretical study revealed how atomic ordering of the substrate controls the structure of surfactant template and the orientation and morphology of the epitaxially grown inorganic material. This dual epitaxial relationship between the substrate, surfactant template, and inorganic mesophase gives rise to a highly ordered porous mesophase with a well-defined cubic lattice of pores. The level of control over the material's three-dimensional architecture achieved in this one-step synthesis is reminiscent of that in biomineralization.

Transcription of G-quartet supramolecular aggregates into hierarchical mesoporous silica nanotubes

Hierarchical porous silica nanotubes or porous silica hollow spheres were prepared employing a low concentration of G-quartet supramolecular aggregates as a template.

Amphiphile self-assemblies in supercritical CO2 and ionic liquids

Supercritical (sc) CO2 and ionic liquids (ILs) are very attractive green solvents with tunable properties. Using scCO2 and ILs as alternatives of conventional solvents (water and oil) for forming amphiphile self-assemblies has many advantages. For example, the properties and structures of the amphiphile self-assemblies in these solvents can be easily modulated by tuning the properties of solvents; scCO2 has excellent solvation power and mass-transfer characteristics; ILs can dissolve both organic and inorganic substances and their properties are designable to satisfy the requirements of various applications. Therefore, the amphiphile self-assemblies in scCO2 and ILs have attracted considerable attention in recent years. This review describes the advances of using scCO2 or/and ILs as amphiphile self-assembly media in the last decade. The amphiphile self-assemblies in scCO2 and ILs are first reviewed, followed by the discussion on combination of scCO2 and ILs in creating microemulsions or emulsions. Some future directions on the amphiphile self-assemblies in scCO2 and ILs are highlighted.

Hollow-structured mesoporous materials: chemical synthesis, functionalization and applications

Hollow-structured mesoporous materials (HMMs), as a kind of mesoporous material with unique morphology, have been of great interest in the past decade because of the subtle combination of the hollow architecture with the mesoporous nanostructure. Benefitting from the merits of low density, large void space, large specific surface area, and, especially, the good biocompatibility, HMMs present promising application prospects in various fields, such as adsorption and storage, confined catalysis when catalytically active species are incorporated in the core and/or shell, controlled drug release, targeted drug delivery, and simultaneous diagnosis and therapy of cancers when the surface and/or core of the HMMs are functionalized with functional ligands and/or nanoparticles, and so on. In this review, recent progress in the design, synthesis, functionalization, and applications of hollow mesoporous materials are discussed. Two main synthetic strategies, soft-templating and hard-templating routes, are broadly sorted and described in detail. Progress in the main application aspects of HMMs, such as adsorption and storage, catalysis, and biomedicine, are also discussed in detail in this article, in terms of the unique features of the combined large void space in the core and the mesoporous network in the shell. Functionalization of the core and pore/outer surfaces with functional organic groups and/or nanoparticles, and their performance, are summarized in this article. Finally, an outlook of their prospects and challenges in terms of their controlled synthesis and scaled application is presented.

Spherical silica micro/nanomaterials with hierarchical structures: synthesis and applications

This paper reviews the progress made recently in synthesis and applications of spherical silica micro/nanomaterials with multilevel (hierarchical) structures. The spherical silica micro/nanomaterials with hierarchical structures are classified into four main structural categories that include (1) hollow mesoporous spheres, (2) core-in-(hollow porous shell) spheres, (3) hollow spheres with multiple porous shells and (4) hierarchically porous spheres. Due to the complex structures and being focused on spherical silica micro/nanomaterials, some novel methods based on the combination of two routine methods or two surfactants, and some special synthetic strategies are proposed to produce the spherical silica micro/nanomaterials with hierarchical structures. Compared with the same-sized solid, porous or hollow silica spheres, these fantastic spherical silica micro/nanomaterials with hierarchical structures exhibit enhanced properties which may enable them to be used in broad and promising applications as ideal scaffolds (carriers) for biological, medical, and catalytic applications.

Hollow mesoporous silica nanoparticles for intracellular delivery of fluorescent dye

In this study, hollow mesoporous silica nanoparticles (HMSNs) were synthesized using the sol-gel/emulsion approach and its potential application in drug delivery was assessed. The HMSNs were characterized, by transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), nitrogen adsorption/desorption and Brunauer-Emmett-Teller (BET), to have a mesoporous layer on its surface, with an average pore diameter of about 2 nm and a surface area of 880 m²/g. Fluorescein isothiocyanate (FITC) loaded into these HMSNs was used as a model platform to assess its efficacy as a drug delivery tool. Its release kinetic study revealed a sequential release of FITC from the HMSNs for over a period of one week when soaked in inorganic solution, while a burst release kinetic of the dye was observed just within a few hours of soaking in organic solution. These FITC-loaded HMSNs was also found capable to be internalized by live human cervical cancer cells (HeLa), wherein it was quickly released into the cytoplasm within a short period of time after intracellular uptake. We envision that these HMSNs, with large pores and high efficacy to adsorb chemicals such as the fluorescent dye FITC, could serve as a delivery vehicle for controlled release of chemicals administered into live cells, opening potential to a diverse range of applications including drug storage and release as well as metabolic manipulation of cells.

A versatile method for controlled synthesis of porous hollow spheres

A versatile method was developed to synthesize nickel silicate, silica, and silica-nickel composite porous hollow spheres by using silica spheres as templates. In the preparation, silica spheres were treated with a mixture of NiSO(4)·6H(2)O and NH(3)·H(2)O. The nickel-based ingredient reacted with the silica to form a shell while the alkaline solution could remove the silica core, thus forming the nickel silicate hollow spheres. After these spheres were further treated with hydrogen in reduction or with HCl in etching, they became silica-nickel hollow spheres or silica hollow spheres, respectively. The sizes of these hollow spheres depended on the concentration of the precursor. Our investigation also found that their surface properties or magnetic properties could be tailored by adjusting the fabrication parameters.

Template-free synthesis of mesoporous CuO dandelion structures for optoelectronic applications

A simple template-free hydrothermal route was used for the synthesis of novel mesoporous CuO dandelion structures formed by self-organized CuO nanorods. A very high surface area approximately 325 m(2)/g and remarkably enhanced photoconductivity under white light irradiation of the CuO dandelions were observed compared to the nanocrystals. The extremely high photoconductivity is attributed to the presence of oxygen related hole-trap states at the large surface area of the dandelions. The fast response (tau = 24 s) of the photocurrent holds promise for the fast photo-sensing device applications.

A facile methodology for the design of functionalized hollow silica spheres

A new amino acid derived amphiphile, lauryl ester of tyrosine (LET) is shown to provide a facile methodology for the preparation of hollow silica spheres. In a previous study on the interface adsorption, it was shown that phenolic OH group in LET plays a key role in the formation and stabilization of close packed structures, typically at the oil/water interface. Drawing an analogy between the air/water and the oil/water interface, we detail here a procedure where air droplets are capped with LET aggregated structures, and in turn they are utilized as viable templates in the production of hollow silica spheres. We demonstrate that hollow silica spheres are formed at pH 4.0 specifically under conditions of vortexing within a short period of time (ca. 15 min). The dimensions of the structures are 0.43±0.15 μm in diameter and they have then subsequently been used as templates for directing the synthesis of silica-silver and silica-polyanthranilic composite hollow spheres.

Two-minute synthesis of PbS nanocubes with high yield and good dispersibility at room temperature

A novel water/glycerol/polyvinylpyrrolidone (PVP) ternary system is developed to realize the successful growth of PbS nanocubes with a narrow size distribution and sharp facets and edges using a one-step synthesis at room temperature for the first time. The synthesis is very fast, high yield, environment-friendly, and low cost. The product possesses uniform dimensionality, high crystallinity and better dispersibility. After dispersing the nanocubes in water or ethanol, the as-formed colloidal suspensions can maintain excellent stability for more than one year under ambient conditions. Uniform silica layers were successfully coated onto the nanocubes via a modified Stöber method to enhance their performance for promising applications. Moreover, by soaking the as-prepared PbS/SiO(2) core-shell nanocubes in hydrochloric acid aqueous solution, well-resolved cubic SiO(2) nanoboxes were obtained. The formation mechanism and the reason for the better dispersibility and excellent stability of the as-obtained nanocubes are also discussed rationally.

Elaboration of monodisperse spherical hollow particles with ordered mesoporous silica shells via dual latex/surfactant templating: radial orientation of mesopore channels

Monodisperse spherical hollow nanoparticles of mesoporous silica featuring mesopores with a radial orientation in the silica shell were synthesized via a dual-templating method. Specifically designed polystyrene latexes with anionic or cationic surface charges acted as the core templates, while cetyltrimethylammonium bromide served as a co-template to structure the mesopore formation during tetraethoxysilane hydrolysis/condensation. The particles were well-separated and presented homogeneous mesoporous silica shells. Average particle diameters were less than 200 nm, and the particles displayed high values of specific surface area and pore volume. The shell thickness and the hollow core diameter could be tuned independently while the radial pore structure was preserved. A detailed analysis of the nitrogen adsorption-desorption isotherms proved that the central cavity was completely isolated from the external medium, that is, only accessible through the radial mesopores of the shell. Consequently, our particles gather the advantages of a well-defined structure, straight penetrating channels across the silica shell, and a high accessible porous volume of the central core. These properties make them far better candidates than simple mesoporous particles for any storage and/or controlled release applications.

Facile synthesis of monodisperse microspheres and gigantic hollow shells of mesoporous silica in mixed water-ethanol solvents

Mesoporous silica materials with a variety of morphologies, such as monodisperse microspheres, gigantic hollow structures comprising a thin shell with a hole, and gigantic hollow structures consisting of an outer thin shell and an inner layer composed of many small spheres, have been readily synthesized in mixed water-ethanol solvents at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained mesoporous silica generally shows a disordered mesostructure with typical average pore sizes ranging from 3.1 to 3.8 nm. The effects of the water-to-ethanol volume ratio (r), the volume content of tetraethyl orthosilicate TEOS (x), and the CTAB concentration in the solution on the final morphology of the mesoporous silica products have been investigated. The growth process of gigantic hollow shells of mesoporous silica through templating emulsion droplets of TEOS in mixed water-ethanol solution has been monitored directly with optical microscopy. Generally, the morphology of mesoporous silica can be regulated from microspheres through gigantic hollow structures composed of small spheres to gigantic hollow structures with a thin shell by increasing the water-to-ethanol volume ratio, increasing the TEOS volume content, or decreasing the CTAB concentration. A plausible mechanism for the morphological regulation of mesoporous silica by adjusting various experimental parameters has been put forward by considering the existing state of the unhydrolyzed and partially hydrolyzed TEOS in the synthesis system.