Emanuel Gutmann

Solvothermal preparation of metallized titania sols for photocatalytic and antimicrobial coatings

The one-pot preparation of metal doped titania sols for coatings with photocatalytic and antimicrobial properties can be realized by using solvothermal conditions in alcoholic solvents at temperatures of 140 °C and above. Under these conditions, hydrolysis of Ti(OR)4 results in photoactive anatase modification while simultaneously added silver or palladium salts will be reduced to colloidal metals. The formation of the nanosized anatase particles is confirmed by wide-angle X-ray scattering (WAXS) and Raman measurements, and the formation of nanosized metal particles of silver and palladium is demonstrated by WAXS and high-resolution transmission electron microscopy (HRTEM). Dynamic light scattering investigations into the particle size of solvothermal TiO2 and Ag sols (compared with their mixtures) suggest that common composite agglomerates are formed due to considerable interactions between the sol particles. After being coated onto viscose fabrics the Ag/TiO2 and Pd/TiO2 composite sols show strong photocatalytic properties. These were determined via decomposition of the organic dye Acid Orange 7, and by antimicrobial effects against gram negative bacteria E. coli even in the dark. Therefore, since no annealing is required to form the photoactive anatase modification, solvothermal sols are well suited to functionalizing less thermally-stable materials such as textiles, polymer foils or paper.

Preparation of Silver Nanoparticles Suitable for Textile Finishing Processes to Produce Textiles with Strong Antibacterial Properties against Different Bacteria Types

This study describes the development of a preparation technique for silver nanoparticles useable as antimicrobial material which is especially useful for textile treatment to realize antimicrobial fabrics. The silver particles need to be prepared by reduction of AgNO3 under moderate conditions and with a moderate and non-toxic reductive agent. Comparative investigations were carried out with silver particles prepared by a solvothermal process or with NaBH4 as reductive agent. Particularly, suitable silver solutions are obtained by stabilizing the silver particles with polyvinylpyrollidone PVP of high molecular weight (Mw ~ 360000 gmol−1) and the use of the non-toxic reductive agents ascorbic acid and fructose. Under these conditions the diameters of the silver particles are in the range of 10 to 30 nm as determined by HR-TEM. The formation of elemental silver has been verified by transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical spectroscopy. The properties of silver particle-containing liquids were investigated by using UV/Vis spectroscopy and dynamic light scattering. Further information on particle size and size distribution was gained through SEM investigations. The prepared solutions of silver nanoparticles can be applied easily onto textiles as liquid coating agents. All prepared textile samples exhibited a high antimicrobial activity against Escherichia coli. However, only few solutions containing silver particles of smaller size exhibit high antimicrobial activity also against other types of bacteria such as Staphylococcus aureus and Streptococcus pneumoniae. Because of this high antimicrobial potential gained with silver solutions prepared in a simple process without usage of toxic components, the developed materials offer a broad range of potential applications. Graphical Abstract Preparation of Silver Nanoparticles Suitable for Textile Finishing Processes to Produce Textiles with Strong Antibacterial Properties against Different Bacteria Types

ELNES study of chemical solution deposited SrO(SrTiO3)n Ruddlesden–Popper films: Experiment and simulation

This article analyzes electron energy-loss near-edge fine structures of the SrO(SrTiO(3))(n=1) Ruddlesden-Popper system and of the parent compounds SrTiO(3) and SrO by comparison with first principles calculations. For that, the fine structures of chemical solution deposited Ruddlesden-Popper films have been experimentally recorded by means of transmission electron microscopy. Moreover, density of states computations using an all-electron density-functional code have been performed. It is shown that the appearance and shape of the experimental O-K and Ti-L(2,3) fine structure features result from the crystallography-dependent electronic structure of the investigated oxides, which display technologically interesting dielectric as well as lattice-structural properties.

Evidence of SrO(SrTiO3)n Ruddlesden-Popper Phases by High Resolution Electron Microscopy and Holography

SrTiO3 (STO) is a preferred substrate material for ferroelectric, ferromagnetic or superconducting films. Its special electrical properties strongly depend on deviations from the stoichiometric chemical composition. Due to the reluctance of introducing point defects into the perovskite lattice, a compositional excess of Sr is compensated through the formation of Ruddlesden-Popper Phases (RP) Srn+1TinO3n+1 characterized by insertion of additional SrO planes into the perovskite lattice. These phases belong to a homologous series of so-called crystallographic shear phases [1–3] (Fig.1).