Early approaches to grow diamond from the vapor phase used thermal decomposition of carbon-containing gases such as CBr4 CI4, CO, or CH4, and were carried out at gas temperatures between 600°C and 1200°C. For these thermal low pressure chemical vapour deposition (CVD) processes, the gas temperatures did not differ much from the surface temperature of the diamond seeds used as substrates. Introduction of a hot zone in the CVD gas phase by means of activation elements such as hot graphite disks, or hot filaments led to substantially higher growth rates, revitalization of the field, and growing interest in vapor-deposited diamond by industrial corporations. Electron cyclotron resonance plasmas were introduced to diamond CVD because they seemed to offer an option to coat large substrate areas. Interaction of plasmas with substrate surfaces can be a serious problem for any plasma-based deposition process.

The examples described in this article illustrate that plasma-assisted CVD processes are versatile tools for preparing the highly sophisticated materials and properties needed in today’s high-tech industries. They feature low temperature processing, non-equilibrium material compositions, high purity of the product, and excellent controllability of the process. Despite a history of more than two decades, the full application potential of plasma-assisted CVD is yet to come. However, in many cases, additional basic knowledge of plasmachemical reactions is necessary in order to further optimize existing technologies and to develop new plasma applications.

Carbon nanotubes (CNTs) are considered very promising for the realization of low-cost field emission electron sources. However, despite intensive research and development efforts, the fabrication of reliable CNT cathodes for high current density (> 100 mA/cm(2)) applications remains a formidable challenge. In this study we use scanning anode field emission microscopy (SAFEM) to investigate the microscopic origins of macroscopic emission performance variations in chemical vapor deposition (CVD) grown CNT planar field emission cathodes. The field enhancement distributions are determined and the field emission properties of individual emission sites on the cathodes are probed. Contact I(V) measurements are carried out to estimate the resistance of individual emitters. The degradation behavior of individual sites is also studied and can be related with the macroscopic cathode performances. Scanning (SEM) and transmission electron microscopy (TEM) provide additional information on the contact and structural properties of the cathodes. Our results indicate that the sample macroscopic performances depend strongly on the individual emitter field emission properties in terms of maximum current before degradation and contact resistance. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Aim: To develop a multilevel approach that includes different toxicity tests and gene-expression studies for toxicity evaluation of engineered nanomaterials developed for biomedical applications. Materials & methods: K-562, MCF-7 and U-937 human-derived cell lines were used as models for in vitro toxicity tests. These tests included viability assays (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium [MTS] assay); evaluation of apoptosis/necrosis by propidium iodide staining and DNA laddering assay; evaluation of mitochondrial toxicity (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolcarbocyanine iodide [JC-1] assay); transmission electron microscopy analysis and gene expression analysis by DNA microarray. For in vivo toxicity evaluation, Swiss mice were used for monitoring acute or chronic effects. Two superparamagnetic contrast agents approved for human use (Resovist (R) and Primovist (R)) and two new lanthanide-based luminescent nanoparticles were tested. Results & discussion: The nanomaterials approved for human use did not show significant toxicities in our assays. Toxicity studies performed on lanthanide-based nanoparticles (EDTA120 and EDTA120D) complexed with the chelating agent EDTA revealed that these nanomaterials induced necrosis in U-937 and K-562 cells while no toxicity was observed in MCF-7 cells. Moreover, no in vivo effects have been observed. The comparative analysis of the nanomaterials and their separated components showed that the toxicity in U-937 and K-562 cells was mainly due to the presence of EDTA. Conclusion: The multilevel approach proved to be useful for nanomaterial toxicity characterization. In particular, for the lanthanide-based nanoparticles tested in this work, the EDTA was identified as the main cause of the toxicity in vitro, suggesting a possible applicability of these nanoparticle suspensions for in vivo optical imaging.

For the next generation x-ray imaging system, small focal spot combined with fast switching electron emitter is desired to obtain high resolution images and minimize motion-induced blurring of images of moving organs such as the heart. Carbon nanotubes (CNTs) have the potential to be excellent emitters for novel x-ray imaging applications that overcome the limitations imposed by conventional thermal emitters. One of the challenges for achieving high emission current from CNT is the early breakdown of emitters due to the Joule heating of the CNT/substrate interface, field evaporation of CNTs and subsequent formation of ions leading to arcing. CNT emitters require emission stability and reproducibility.

This chapter deals with inorganic luminescent materials and consists of two parts. It starts with a general description of luminescence‐ and excitation mechanisms, by giving a description of the way they operate in well‐known devices, like lamps or medical imaging equipment. In the second part, we concentrate on emerging medical applications. The focus is on the interplay between the performance of the luminophores required by the application and material properties of the luminescent compounds.

Optical imaging using unspecific contrast agents as well as targeted and disease-specific agents play a vital role in preclinical research. Moreover, optical imaging is on the verge of establishing itself as a clinically relevant imaging modality. Also in-vitro diagnostical procedures rely to a large degree on optical labels to report disease-specific events. Materials that fulfill the basic requirements of this market are being used today, with cyanine dyes and semiconductor quantum dots being excellent examples. Other materials are being tested in laboratories throughout the world. Design rules suitable to develop new optical labels for in-vivo near-infrared optical imaging procedures have been formulated by us, and we have developed synthesis routes that lead to nano particles with small diameter, narrow size distribution, high quantum yield, and with stable surfaces required for bioconjugation to disease-specific ligands.

In this work we report a novel approach to grow structured, highly oriented Carbon Nanotubes (CNTs) that are vertically aligned to the substrate with adequate field emission. Growth is done at lithographically defined dots of catalysts, which can be deposited on metallic, semi-conducting and glass substrates. A sandwiched catalyst structure and microwave plasma chemical vapor deposition led to the formation of uniform CNT-arrays of 3 x 3 mu m(2). The method is easily scalable to large areas. The CNT-arrays exhibit a stable field emission of 20 mA and a current density of 50 mA/cm(2) at a rather low electric field of 5. 33 V/mu m.