Simple dose rate measurements for a very high synchrotron X‐ray flux

Dose measurements based on methylene blue (MB) bleaching, widely used for ultraviolet light, can also be applied to X‐rays including very high flux levels. This method has been tested by using both MB bleaching and Fricke dosimetry for a conventional monochromatic X‐ray source and then for `white‐beam' synchrotron radiation. The results show that MB bleaching dosimetry can easily measure X‐ray doses up to at least 10⁵ Gy s^?1, as long as the MB concentration is sufficiently high. This condition can be verified from the deviations from linearity of the bleaching versus exposure time.     

X-ray microscopy and tomography detect the accumulation of bare and PEG-coated gold nanoparticles in normal and tumor mouse tissues

We demonstrate that, with appropriate staining, high-resolution X-ray microscopy can image complicated tissue structures--cerebellum and liver--and resolve large or small amounts of Au nanoparticles in these tissues. Specifically, images of tumor tissue reveal high concentrations of accumulated Au nanoparticles. PEG (poly(ethylene glycol)) coating is quite effective in enhancing this accumulation and significantly modifies the mechanism of uptake by reticuloendothelial system (RES) organs.     

Using photoelectron emission microscopy with hard-X-rays

We present several successful test cases of using photoelectron emission microscopy (PEEM) for photon energy up to 25 keV. First, the full extended X-ray absorption fine structure analysis was implemented in areas as small as 100 μm² for transition-metal K edge absorption spectra and, therefore, demonstrated the feasibility of combining structural and chemical analysis with hard-X-ray absorption spectroscopy with high lateral resolution. We also show that PEEM can be used in a transmission (radiography) mode as an imaging detector for hard-X-ray. This approach again leads to the unprecedented 0.3 μm lateral resolution, particularly critical for the use of coherence-based phase contrast techniques in real time X-ray radiology.     

High-resolution photoemission in low-dimensional conductors and superconductors

We review some recent spectroscopic results on low-dimensional systems, including high-T_c superconductors, and charge density wave compounds. We briefly discuss the reasons for the present interest in these materials, and the relevance of band mapping experiments by angle-resolved photoemission spectroscopy. The main focus of the paper is on high-energy resolution, which can be exploited to probe the quasiparticle excitations, and to study the characteristic instabilities of the Fermi surface. Gap spectroscopy in the ordered phases is a prominent part of this research, namely in the cuprates. The normal state properties, however, are often as interesting. This is particularly true in 1D, where the photoemission results indicate strong deviations from a Fermi liquid scenario.     

X‐ray‐induced Cu deposition and patterning on insulators at room temperature

X‐ray irradiation is shown to trigger the deposition of Cu from solution, at room temperature, on a wide variety of insulating substrates: glass, passivated Si, TiN/Ti/SiO₂/Si and photoresists like PMMA and SU‐8. The process is suitable for patterning and the products can be used as seeds for electroplating of thicker overlayers.     

Infrared near-field microscopy with the Vanderbilt free electron laser: overview and perspectives

Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences.