Abstract

The first use of magnetic nanoparticles (MNPs) as assembling components in complex coacervation is presented. The single-step formation of MNP-based microspheres (see figure) can be considered as a NP self-assembly process induced by the presence of polyelectrolytes, in which solid microspheres are rapidly generated at ambient temperature, without the need for a solid template.

A rapid-setting, mesoporous, bioactive glass cement (MBGC, see figure) that exhibits highly desirable plasticity and superior in vitro bioactivity is described. The calcium-deficient hydroxyapatite nanocrystals that form during cement setting act as linkers between mesoporous bioactive glass particles to make the cement mechanically robust. The MGBC is promising for applications in clinical orthopedics, drug delivery, and tissue engineering.

Mesoporous silica nanofibers with longitudinal pore channels are synthesized in high yields using cetyltrimethylammonium bromide as the structure-directing agent in hydrobromic acid solutions. These nanofibers are used as templates to prepare gold nanoparticles along the fiber axis. For the gold-precursor-loaded nanofibers that are not completely dried, nearly spherical gold nanoparticles are produced by hydrogen reduction. As the reduction temperature is lowered, the size of the gold nanoparticles decreases and the number density greatly increases, resulting in surface plasmon coupling between neighboring gold nanoparticles. For the gold-precursor-loaded nanofibers that undergo an additional drying process, ellipsoidal gold nanoparticles are obtained, with their major axes oriented along the direction of the pore channels. The major axes of ellipsoidal gold nanoparticles can be controlled to be oriented either parallel or perpendicular to the fiber axis by use of nanofibers with either longitudinal or circular pore channels, respectively. These gold-nanoparticle-embedded nanofibers can be expected to find interesting applications in the area of photonics and optoelectronics.

Nimm einfach ein Stück Band: Mesoporöse Siliciumdioxidbänder mit einer Dicke von 50 bis 250 nm, einer Breite von 0.4 bis 1.5 μm und einer Länge von mehreren hundert Mikrometern wurden mit kationischen Tensiden als Templaten unter sauren Bedingungen hergestellt. Ihre Querschnitte wurden mit SEM- und TEM-Techniken untersucht (siehe Bild).

Take a length of ribbon: Mesoporous silica ribbons that are typically 50–250 nm thick, 0.4–1.5 μm wide, and hundreds of micrometers long were prepared by a one-phase approach with cationic surfactants as templates under acidic conditions, and their cross-sections were studied by SEM and TEM techniques (see picture).

An approach for multibit-per-site optical data storage has been proposed and demonstrated using mesostructured composite films incorporated with uniformly dispersed photoacid generator and pH-sensitive dye molecules. Upon light illumination, photoacid generator molecules produce acid, which induces a change in the absorption property of pH-sensitive dye molecules. Because the amount of the generated acid is proportional to the illumination time, the resulting change in the absorption property of mesostructured composite films varies as a function of the illumination time. This function between the absorption property of mesostructured composite films and the illumination time can be used for multibit-per-site optical data storage. Recording is performed by using certain discrete values of the illumination time to represent information bits. Reading out is achieved by measuring the absorbance of composite films at a particular wavelength, from which the stored information bits can be determined. In general, N-bit-per-site storage can be realized using 2^N discrete values of the illumination time. This multibit-per-site approach for optical data storage is compatible with the current single-bit-per-site technology used for compact disks and digital versatile disks, and will provide significantly larger optical storage capacity. It is also suitable for two-photon multilayer optical data storage if the photoacid generators and pH-sensitive dyes are properly designed.

Spontan entstehen Mikrokügelchen, wenn geladene Polyaminosäuren mit entgegengesetzt geladenen mehrwertigen organischen Ionen vereint werden. Die Kugeloberflächen sind chemisch aktiv und dienen als Template für die Kondensation von Kieselsäuren, wobei je nach Säure leere oder polymergefüllte Systeme erhalten werden (siehe Bild; das fluoreszierende Polymer bildet eine Schicht in einer durch kondensiertes kolloidales Silicat bedeckten Kugel).

Hochgeordnete mesoporöse Filme mit einer Mehrkomponentenwandstruktur aus nanokristallinem Anatas zusammen mit amorphem Titandioxid und Cadmiumchalkogenid (siehe Bild, der Balken entspricht 20 nm) sind durch ein schnelles und einfaches Reagensglas-Syntheseverfahren auf der Grundlage von Sol-Gel-Chemie und supramolekularer Strukturdirektion zugänglich. Die Filme zeigten in Experimenten zur Photostromerzeugung erhöhte Empfindlichkeit für sichtbares Licht.

Spontaneous formation of microspheres is observed when charged poly(amino acid)s are combined with certain oppositely charged, multivalent organic ions. The surfaces of the spheres are chemically active and act as templates for silica condensation, and the assemblies can be made hollow or polymer-filled, depending on the silica precursor (see image; the fluorescent polymer forms a layer inside a colloidal-silica-coated sphere).

Highly ordered mesoporous films with a multicompositional nanocrystalline anatase titania/cadmium chalcogenide wall structure (see figure, scale bar is 20 nm) were synthesized by a fast and inexpensive one-pot single-precursor sol–gel-chemistry route based on supramolecular templating. These films show enhanced sensitivity to visible light in photocurrent generation experiments.

Dyeing for excitement? Laser excitation of rhodamine 101 doped 2D hexagonally ordered SBA-15 mesostructured silica thin films results in anti-Stokes luminescence with high quantum efficiencies; the emitted light is higher in energy than the absorbed one (see picture). It is shown that this effect is attributed to an energy up-conversion that involves a direct single-photon absorption process from high-energy vibration–rotation levels of the ground singlet state S₀ to one of the vibration–rotation levels of the first excited singlet state S₁.

Die wohldefinierte Anordnung von Poren und Wänden aus Nanokristalliten in einem mesoporösen Titanoxid-Dünnfilm kann mit hohen Konzentrationen (bis zu 8 Mol-%) von Eu³⁺ unter Bildung eines rot photolumineszierenden Materials dotiert werden (siehe Bild). Die Photolumineszenz stammt von einem Energietransfer von den Bandlückenzuständen der Titanoxid-Nanokristallite in die Kristallfeldzustände der Europium-Ionen; eine Photolumineszenz-Konzentrationslöschung wird aufgrund der großen Oberfläche und nanokristallinen Struktur des Materials verhindert.

The well-ordered array of pores and walls made up of nanocrystallites in a mesoporous titania thin film can be doped with high concentrations of Eu³⁺ (up to 8 mol %) to create a bright red photoluminescent material (see picture). The photoluminescence arises from energy transfer through excitation of the titania nanocrystallites in their band gap to the crystal field states of the europium ions; photoluminescence concentration quenching is prevented because of the high surface area and nanocrystalline structure of the material.

Mesostructured and mesoporous materials with incorporated photo-active species are currently attracting attention as components for compounds with novel optical properties. The nanoscale organization (2–15 nm) of organic/inorganic arrays or the porous structure can be used to tailor the properties and microenvironments. Polymer alignment within the pores (as shown in the picture), the generation of size-limited silicon clusters, and the one-step synthesis of laser materials are some highlighted examples.