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CdSe quantum dots combined with [FeFe] hydrogenase mimics as molecular catalytic reaction centers based on earth abundant elements have demonstrated promising activity for photocatalytic hydrogen generation. Direct linking of the [FeFe] hydrogenase mimics to the quantum dots surface is expected to enhance the activity of the system by establishing close contact between the [FeFe] hydrogenase mimics and the light harvesting quantum dots supporting the transfer and accumulation of several electrons which are needed to drive hydrogen evolution. To circumvent the problem of limited colloidal stability upon covalent functionalization of the quantum dots under optimal pH conditions for hydrogen evolution, in this work, we report on the functionalization of quantum dots immobilized in a thin film architecture on a substrate with [FeFe] hydrogenase mimics by covalent linking via carboxylate groups as anchoring functionality to bind to the QD surface. The functionalization was monitored via UV/Vis absorption, photoluminescence, infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) and quantified via micro X-ray fluorescence spectrometry (μXRF). The activity of the molecularly functionalized thin film was demonstrated and in dependence on the linker length TONs in the range of 360-580 (short linker) and 130-160 (long linker) were achieved. This work presents a proof of concept study showing the potential of thin film architectures of immobilized quantum dots as platform for light-driven hydrogen evolution and beyond.

Trace elements are essential for life and their concentration in cells and tissues must be tightly maintained and controlled to avoid pathological conditions. Established methods to measure the concentration of trace elements in biological matrices often provide only single element information, are time-consuming, and require special sample preparation. Therefore, the development of straightforward and rapid analytical methods for enhanced, multi-trace element determination in biological samples is an important and raising field of trace element analysis. Herein, we report on the development and validation of a reliable method based on total reflection X-ray fluorescence (TXRF) analysis to precisely quantify iron and other trace metals in a variety of biological samples, such as the liver, parenchymal and non-parenchymal liver cells, and bone marrow–derived macrophages. We show that TXRF allows fast and simple one-point calibration by addition of an internal standard and has the potential of multi-element analysis in minute sample amounts. The method was validated for iron by recovery experiments in homogenates in a wide concentration range from 1 to 1600 μg/L applying well-established graphite furnace atomic absorption spectrometry (GFAAS) as a reference method. The recovery rate of 99.93 ± 0.14% reveals the absence of systematic errors. Furthermore, the standard reference material “bovine liver” (SRM 1577c, NIST) was investigated in order to validate the method for further biometals. Quantitative recoveries (92–106%) of copper, iron, zinc, and manganese prove the suitability of the developed method. The limits of detection for the minute sample amounts are in the low picogram range., publishedVersion

Extracorporeal human lymphatic organs are expected to be excellent tools in the study of human molecular and cellular bases of the immunologic balance and tissue harmony. A rational approach and process to design a device and a procedure to recreate the human lymph node environment in vitro is described with emphasis on T-cell activation. Based on this approach, a bioreactor and a process supporting self-assembly of human lymphatic tissues due to proper emulation of human architecture and homeostasis could be developed.