Precise Synthesis of Well-Defined Inorganic-Organic Hybrid Particles

Synthesis of hybrid particles toward precisely designed hierarchical nanoarchitectures is summarized. In order to satisfy the demands for a variety of materials' performances, the selection of materials, composition and synthesis is carefully done. Flow reactors are one of the useful synthetic means to prepare hybrid materials, especially those with hierarchically and precisely designed multi-components hybrid particles, owing to the efficient mixing and heat exchange in the reactor as well as its connectable (both parallel and sequential) feature. In this review article, after the summary of the preparation of hybrids based on oxides and organics through conventional batch reactors, the application of flow reactors to the preparation of various hybrid particles is introduced to highlight the present status and future possibility of the flow reactor synthesis.

Preparation of Eu(iii) acetylacetonate-doped well-defined titania particles with efficient photoluminescence properties

Eu(iii) acetylacetonate-doped well-defined titania particles were synthesized to demonstrate composition dependent efficient luminescence properties.

Mesoporous silica coated silica-titania spherical particles: from impregnation to core-shell formation

The coating of solid surfaces with inorganic materials is a promising approach not only to impart various functionalities but also to modify physicochemical properties that are affected by the geometry/structure of the coating. In this study, a silica-hexadecyltrimethylammonium (silica-CTA) hybrid layer was deposited on monodispersed spherical particles composed of titania and octadecylamine (titania-ODA) by a sol-gel reaction of tetraethoxysilane in aqueous CTA/ammonia/methanol solution. The formation of the coating was confirmed by SEM and TEM observations. The coating thickness varied from a few nm to 100 nm depending on the Si/Ti ratio. We found that Si/Ti = 0.68 resulted in the formation of microporous silica-titania particles with the pore size of 0.7 nm as revealed by nitrogen adsorption/desorption measurements. Because the titania-ODA particles can be converted to mesoporous titania particles after removing ODA by acid/base treatment, the silica species can be impregnated into the titania particles and replace ODA under basic conditions. By increasing the Si/Ti molar ratio up to 1.4, silica-titania particles with non-porous structures were obtained. An amorphous to anatase transition occurred at around 800 °C, indicating the complete impregnation of silica inside the titania particles. Further increases of the Si/Ti molar ratio (to 3.4 and 6.8) led to the formation of the silica-CTA shell on the core particles, and the shell was converted to mesoporous silica layers with a pore size of 2 nm after calcination at 550 °C for 5 h. Non-linear control of the pore size/structure is presented for the first time; this will be useful for the precise design of diverse hybrid materials for optical, catalytic and biomedical applications.

Controlled growth of silica-titania hybrid functional nanoparticles through a multistep microfluidic approach

Silica/titania-based functional nanoparticles were prepared through controlled nucleation of titania and subsequent encapsulation by silica through a multistep microfluidic approach, which was successfully applied to obtaining aminopropyl-functionalized silica/titania nanoparticles for a highly sensitive humidity sensor.

Designed synthesis of well-defined titania/iron(iii) acetylacetonate nanohybrids with magnetic/luminescent properties

Synthesis and magnetic/luminescent properties of well-defined titania/octadecylamine/iron(iii) acetylacetonate hybrid functional particles were demonstrated.

Preparation of luminescent titania/dye hybrid nanoparticles and their dissolution properties for controlling cellular environments

Monodispersed titania/octadecylamine/fluorescein-isothiocyanate hybrid nanoparticles are synthesized to demonstrate a proof-of-concept for nanomedicines: an indirect molecular delivery system with no cytotoxicity.

Synthesis of cytocompatible luminescent titania/fluorescein hybrid nanoparticles

Luminescent titania-fluorescein (FS) hybrid nanoparticles (NPs) were successfully synthesized by a sol-gel reaction of titanium alkoxide in the presence of octadecylamine using a fluidic reactor with a Y-type channel. The molar ratio of FS/Ti ratio was varied in the range from 1/1000 to 1/100 in order to obtain the hybrid NPs with the different luminescent behavior. The shape of the NPs is spherical and their sizes are 400 nm which is almost the same irrespective of the FS content, suggesting the different FS molecular states in one NP. We also demonstrated that the hybrid NPs exhibited a characteristic luminescence; the NPs with the higher and lower FS contents exhibited an enhanced luminescence in PBS and air, respectively, indicating that the FS states responded to the molecular environment. Through cytocompatible experiments using the NPs, it turned out that they had a high compatibility for fibroblasts. Therefore, the preparation of a series of the luminescent NPs with a tunable luminescence property was achieved. The results will lead to a guideline to determine a proper combination between material composition and an environment where they are used, being useful for biomedical applications.

Effective Surface Functionalization of Carbon Fibers for Fiber/Polymer Composites with Tailor-Made Interfaces

Composites between carbon fibers (CFs) and heterogeneous materials have been widely studied and their fabrication techniques have been developed. However, their hydrophobic surfaces make it difficult to disperse CFs into hydrophilic resins, which results in weak junctions with ceramics. To develop high-strength composite fibers, it is important to design interfacial chemical bonds. Thus, surface-modification techniques of CFs have recently become the main focus and their interfaces have been characterized by various analytical methods. In this Minireview, various techniques that modify the CF surface by coating with inorganic polymers (metal oxide compounds) are highlighted, and the applications of novel nanocomposite fibers are also described. Furthermore, interfacial bonds between CFs and polymer resins are reviewed and discussed in terms of CF-reinforced plastics and their future prospects.

Oxide-based inorganic/organic and nanoporous spherical particles: synthesis and functional properties

This paper reviews the recent progress in the preparation of oxide-based and heteroatom-doped particles. Surfactant-templated oxide particles, e.g. silica and titania, are possible candidates for various potential applications such as adsorbents, photocatalysts, and optoelectronic and biological materials. We highlight nanoporous oxides of one element, such as silicon or titanium, and those containing multiple elements, which exhibit properties that are not achieved with individual components. Although the multicomponent nanoporous oxides possess a number of attractive functions, the origin of their properties is hard to determine due to compositional/structural complexity. Particles with a well-defined size and shape are keys for a quantitative and detailed discussion on the unique complex properties of the particles. From this viewpoint, we review the synthesis techniques of the oxide particles, which are functionalized with organic molecules or doped with heteroatoms, the physicochemical properties of the particles and the possibilities for their photofunctional applications as complex systems.