Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called “small size effect”, yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given

Silica Materials for Medical Applications

The two main applications of silica-based materials in medicine and biotechnology, i.e. for bone-repairing devices and for drug delivery systems, are presented and discussed. The influence of the structure and chemical composition in the final characteristics and properties of every silica-based material is also shown as a function of the both applications presented. The adequate combination of the synthesis techniques, template systems and additives leads to the development of materials that merge the bioactive behavior with the drug carrier ability. These systems could be excellent candidates as materials for the development of devices for tissue engineering

Surface modification of as-synthesized lamellar mesostructured silica obtained by liquid crystal templating

We report a study of lamellar silica phase silylation, starting from as-synthesized silica, without the usual heat treatment step. Characterizations of the modified silica include X-ray diffraction, thermal analysis, electron microscopy and solid state NMR. Special attention is given to the possibility of keeping the lamellar organisation along with the elimination of the organic template

Mesoporous materials for heavy metal ion adsorption synthesized by displacement of polymeric template

A successful application of the template displacement synthesis to the polymer templated mesoporous silica SBA-15 resulted in the preparation of materials with high surface area and open porosity. It was shown for the first time that such procedure is applicable for neutral polymer templated silica-based materials. Some of the materials, particularly the sample with attached 1-allyl-3-propylthiourea functionality, exhibited promising properties towards mercury ion adsorption. The maximum mercury loading from aqueous solution is 0.16 g Hg2+/g or 0.8 mmol Hg2+/g. The mercury desorption was accomplished by washing the mercury-loaded samples with aqueous thiourea solution.close121

Kontrolle und Visualisierung der Verteilung funktioneller Gruppen auf mesoporösem Siliciumdioxid

Die Verteilung von fluoreszenzmarkierten Aminogruppen auf mesoporösem Siliciumdioxid wurde durch konfokale Laser-Scanning-Mikroskopie visualisiert. Die Mobilität der zur Funktionalisierung eingesetzten Aminosilane bestimmt den relativen Anteil der an der Oberfläche verankerten Gruppen. Ausgehend von dieser Beobachtung wurde eine einfache Methode zur Modifizierung der äusseren Oberfläche von mesoporösem Siliciumdioxid entwickelt