The development of small and smallest particle is one of today’s key features in modern science. The goal is to form materials with improved properties than their classical” ancestors with just a fractional amount of raw material. However, the characterization of these particles is as important as their way of preparation. Different techniques with their origins in physics, inorganic, organic and physical chemistry have to be combined to reveal the secrets of this important field of science. This book gives a short overview of theoretical basics and synthesis methods to form and characterize gold and zirconia nanoparticles. Phenomenon like plasmon resonance self-assembly of surfactants and the different structures of ZnO2 are explained. Furthermore, analytical tools, like small angle X-ray scattering, X-ray powder diffraction and scanning electron microscopy are introduced. In addition, details on the synthesis of gold and zirconia nanoparticles are presented and are examined by the mentioned analytical and calorimetric methods.

Text Sample: Chapter 4.2, Electron based method: scanning electron microscopy (SEM): The use of X-rays for structural analysis is well established nowadays. However, problems occur when structures containing larger and smaller particles should be analyzed during one experiment. Compared with light microscopy, X-ray dependent methods are not able to give an image of the focused sample. Since light microscopy is limited in resolution because of the limited use of light due to optical components, the influence of the optical aperture and the Rayleigh criterion, which describes the limit in size of observable structures by using visible light, other ways of imaging had to be found. By using electrons instead of electromagnetic waves, optical problems are bypassed. This led to the development of transmission electron microscopy (TEM) and scanning electron microscopy (SEM), where the latter has major advantages in sample preparation, diversity and resolution. 4.2.1, Principal setup: Images are produced by scanning a sample with an electron-beam while displaying the signal from an electron detector on a computer monitor. By choosing the appropriate detection mode, either topographic or compositional contrast can be obtained. Spatial resolution better than 10 nm in topographic mode and 100 nm in compositional mode can be achieved. The big advantage of the topographic mode is the large depth of field in SEM images. An important factor in the success of the SEM is that images of three-dimensional objects are usually accessible to immediate intuitive interpretation by the observer, just like in optical microscopy. The range of applications of SEM can be extended by adding other types of detection, e.g. for light emission caused by electron bombardment or cathodoluminescence (CL), or the use of an X-ray-detector for energy dispersive X-ray spectroscopy (EDX) to perform elemental analysis. Fig. 4.11 gives a simplified overview of a typical SEM with two electron detectors. Classical SEM instruments are operating at vacuum, so an interaction of electrons with gas-molecules is minimized. Electrons are emitted by an electron gun, which is typically a thermionic cathode. With the highest melting point of all metals (3422 °C), tungsten has optimal characteristics for high efficient electron-emitting filaments. A direct current heats the filament to about 2400 °C. At this temperature, tungsten emits electrons into the surrounding vacuum (thermionic emission). The emitted electrons are accelerated in an electric field of about 30 kV. The result is an electron beam, which is focused on a small part of a sample by magnetic lenses. The impact of electrons on the sample induces several interactions with the electrons. The detection of these interactions gives information on the specific part of the sample, where the emission of secondary electrons is the most common information source. Electrons of the primary beam effect an emission of electrons of the outer shells of the atoms located at the sample’s surface. Therefore, topographic information is gained. To obtain information on the chemical composition, back-scattered electrons can be detected. These electrons are reflected by atoms on the specimen’s surface, where big atoms have a greater ability to reflect electrons as small ones. The mechanism of reflection is supposed to be an elastically impact of electrons on surface electrons.

• nanoparticles

• Gold

• Zirconia

• SAXS

• Ascorbic acid derivates

• Small angle X-ray scattering

Stephan Dankesreiter, Dipl. Chem. (univ.), was born 1984 in Zwiesel. After his basic studies at the University of Regensburg, he joined the COSOM-program (Complex Condensed Materials and Soft Mater) and was able to get a closer look on synthesis and characterization methods of nanoparticles. In 2009, he was able to work on this field during his diploma-thesis at the University of Florence (CSGI, Center for Colloidal and surface science) and finished successfully his studies in chemistry with the diploma degree.