Study on 3D- and picoliter printed multi-elemental references and element species properties with respect to energy storage and recycling

The preparation and application of references in analytical chemistry play a decisive role in the evaluation of analytical procedures and method development. Reference materials stand out for their homogeneity and their well characterized elemental concentrations by metrologically valid procedures. Reference materials are not limited to be of well-defined elemental concentrations but may also be of defined morphology, i.e., position on a sample support. The main goal of this work was the preparation of reference materials with defined morphology and position for static and dynamic processes with different techniques for their application in X-ray based analytics. A novel modular picoliter printer was designed and build from off-the-shelf parts, open-source project resources and self-made components and software to provide “drop-on-demand” picoliter droplets which contained the desired elemental composition. 65 elements were identified being printable. The generated droplets were characterized in terms of droplet volume by gravimetric measurements of multiple droplets as well as in terms of elemental concentrations and deposited masses via total reflection X-ray fluorescence analysis (TXRF) and inductively coupled optical emission spectroscopy (ICP-OES). Dried residues from these droplets were found to be in general of a hemi-spherical morphology excellently suited for probing X-ray – sample interactions and probing the droplet evaporation on a quartz crystal microbalance. The detector field of view was determined for a laboratory TXRF device using the picoliter printed micro residues with defined specimen offsets relative to the sample carrier centre and position-dependent errors in signal intensities were evaluated experimentally. The relative sensitivity and the influence on the quantification was probed in several studies. Picoliter derived residues were used in the optimization of reconstruction methods in full-field micro X-ray fluorescence analysis (microXRF) with coded apertures. Defined elemental patterns served as references for the reconstruction algorithm. By preparation of defined sample morphologies, the characteristic angle-scans of "particle-like" and "film-like" specimen could be obtained experimentally. For this purpose, grazing-incidence X-ray fluorescence analysis was performed on picoliter derived specimens. Linear combination fits of the experimental data showed good agreement with angle-scans of synthetic "in between" specimen, that exhibit characteristics of both sample morphologies in their respective angle-scans. In addition to the picoliter printed references, 3D printed elemental references were obtained from stereo lithography where the resin was supplied with soluble metal complex solution to validate a Monte-Carlo based ray-tracing model for experimental confocal microXRF data. The printed structures were probed with several methods for well-characterized samples. In order to determine the homogeneity of the sample, a laboratory microXRF device was constructed and characterized. Reference materials were prepared for studies in polymer electrolyte membranes (PEM) for vanadium redox flow batteries (VFB). The vanadium uptake was determined with TXRF as well as ICP-OES and the soaked membranes were used as references in micro X-ray absorption near edge structure analysis (XANES). Diffusion studies with the observation of redox reaction taking place inside the PEM were performed in in-plane and through-plane direction as well as cyclized PEM from VFBs. The diffusion profile of vanadium(III) in hydrated PEMs was determined experimentally and compared to molecular dynamic simulations. Additional studies on the speciation of vanadium were conducted with high performance liquid chromatography. Synthetic mineral references were prepared as picoliter derived residues as well as macroscopic powders for the synthesis and characterization of artificial slags. The slags were probed with microXANES as well as with laboratory-based XANES. A first BAYESIAN optimization in the data acquisition of lab-XANES was applied minimizing the necessary data points.