TY - JOUR A1 - Wolff, Timo A1 - Mantouvalou, I. A1 - Malzer, W. A1 - Nissen, J. A1 - Berger, D. A1 - Zizak, I. A1 - Sokaras, D. A1 - Karydas, A. A1 - Grlj, N. A1 - Pelicon, P. A1 - Schütz, R. A1 - Zitniki, M. A1 - Kanngießer, B. T1 - Performance of a polycapillary halflens as focussing and collecting optic - a comparison N2 - Polycapillary halflenses are widely used to focus X-ray radiation onto a small spot. Additionally they can reduce the field of view of a semiconductor detector when placed in front of one. In 3D micro X-ray fluorescence spectroscopy (3D Micro-XRF) with synchrotron radiation, two polycapillary halflenses are used in a confocal geometry. Up until now, characterization measurements in the focal plane have only been performed in the case of the lens focusing parallel radiation. Assumptions have been made, that in the other case, when isotropic radiation from a spot source is transported to a detector, the acceptance distribution in the focal plane is also Gaussian. We performed measurements with an electron beam as well as a proton beam which confirm this assumption. In addition, a comparison between measurements in collecting and focusing mode show differences in spot size and transmission. These differences exemplify the fact that there is not one global spot size or transmission function of a polycapillary halflens. Illumination and divergence effects can alter both characteristic lens parameters. PY - 2009 DO - https://doi.org/10.1039/b817828c SN - 0267-9477 SN - 1364-5544 VL - 24 SP - 669 EP - 675 PB - Royal Society of Chemistry CY - London AN - OPUS4-19415 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - da Costa, P. F. G. M. A1 - Merízio, L. G. A1 - Wolff, N. A1 - Terraschke, H. A1 - de Camargo, Andrea T1 - Real-time monitoring of CdTe quantum dots growth in aqueous solution N2 - Quantum dots (QDs) are remarkable semiconductor nanoparticles, whose optical properties are strongly size-dependent. Therefore, the real-time monitoring of crystal growth pathway during synthesis gives an excellent opportunity to a smart design of the QDs luminescence. In this work, we present a new approach for monitoring the formation of QDs in aqueous solution up to 90 °C, through in situ luminescence analysis, using CdTe as a model system. This technique allows a detailed examination of the evolution of their light emission. In contrast to in situ absorbance analysis, the in situ luminescence measurements in reflection geometry are particularly advantageous once they are not hindered by the concentration increase of the colloidal suspension. The synthesized particles were additionally characterized using X-ray diffraction analysis, transition electron microscopy, UV-Vis absorption and infrared spectroscopy. The infrared spectra showed that 3-mercaptopropionic acid (MPA)-based thiols are covalently bound on the surface of QDs and microscopy revealed the formation of CdS. Setting a total of 3 h of reaction time, for instance, the QDs synthesized at 70, 80 and 90 °C exhibit emission maxima centered at 550, 600 and 655 nm. The in situ monitoring approach opens doors for a more precise achievement of the desired emission wavelength of QDs. KW - CdTe quantum dots KW - In situ synthesis KW - Real time growth control PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-603596 DO - https://doi.org/10.1038/s41598-024-57810-8 VL - 14 IS - 1 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-60359 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -