Beata Borak

Active Sol-Gel Materials

Sol-gel technology has attracted considerable attention due to possibility of obtaining submicron and nano-sized materials. The method of silica and titania nanopowders and thin films obtaining will be presented. Also properties and prospective application of these materials will be express. Additionally, methods of obtaining nanomaterials with different grains shape and specific properties (submicron spherical silica powders, titania nanofibers) will be showed. One of the main advantages of the sol-gel technique is the easiness of doping of the obtained materials with various substances (inorganic, organic, biological). Materials activated this way possess several useful properties. For example, silica spherical matrices with metallic nano-islands on their surface will be presented. Such silver-doped silica powders display anti-microbial capabilities and can be used to obtain doped thin-film coatings e.g. for the production of bacteriostatic textiles. Moreover, materials obtained by the sol-gel method have found wide application in the area of sensors. Examples of optical sensors based on sol-gel derived thin films and optical fiber or planar wave-guide will be also presented.

Insights into the multistep transformation of titanate nanotubes into nanowires and nanoribbons

Abstract Different types of titanate one-dimensional nanostructured materials were synthesized and characterized using scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The results presented in this work unquestionably showed dependence of morphology and structure of the titanate nanopowders on parameters of hydrothermal synthesis. It was found that nanotubes, nanowires and nanoribbons are three unavoidable kinetic products of hydrothermal reaction. Moreover, increasing temperature of reaction or hydrothermal treatment duration results in acceleration of nanotube-nanowire-nanoribbon transformation. However, the sequence of titanate morphology transformation is invariable. The detailed studies further revealed that the crystal structure of hydrothermally prepared nanotubes and nanowires are indistinguishable but the determination of the exact structure is practically impossible. Because of higher crystallinity, the structure of nanoribbons can be established. It was shown that it corresponds to the monoclinic layered trititanic acid H2Ti3O7 and is isostructural with sodium derivatives Na2_xHxTi3O7.nH20 (with x near 2).

Glass photonic structures fabricated by sol-gel route

To emphasize the scientific and technological interest in the silica-based glassy systems and the versatility of the sol-gel route, nano and micrometer scale structures are discussed focusing the attention mainly on the rare-earth-activated materials and their spectroscopic characterization. We have demonstrated that various SiO2-based binary systems can be successfully employed for the fabrication of amorphous planar waveguides, glass–ceramic waveguides, and tapered rib waveguide laser. Different technological processes allowed to realize Er3+ -activated microspheres that can be exploited as microresonator and it has been evidenced that through specific coating it is possible to modify modal free spectral range and/or modal dispersion of the microresonator and achieve laser action. In the case of rare-earth-doped 3-D colloidal crystals in different configurations (direct and inverse one), it has been shown that the relaxation dynamics of the electronic states can be engineered.

Luminescent sol–gel-derived micro and nanoparticles

This paper presents a short review of the results obtained by the authors in the field of the sol–gel-derived glass nanoparticles activated with lanthanides ions. The attention is focused on the systems that are particularly interesting for photonic structures and bioapplications. We discuss how the sol–gel technology allows to prepare different kind of active nanoparticles and how is possible to use them in specific applications. Some examples showing fabrication techniques of spherical micro- and nanoparticles are given, including preparation of rare-earth-doped silica and silica-calcia glass. The proper structures are mentioned to tailor the optical and spectroscopic properties of microresonators. Glass-ceramics systems are also reminded where nanocrystalline particles are derived. Fabrication and spectroscopic assessment of rare earth doped HfO2 and SnO2 nanoparticles are presented as well. Finally, it is discussed how bioactive properties of SiO2– CaO nanoparticles can be used in medicine, for example in tracking using their luminescent properties.