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We report the application of lanthanide-binding tags (LBTs) for two- and three-dimensional X-ray imaging of individual proteins in cells with a sub-15 nm beam. The method combines encoded LBTs, which are tags of minimal size (ca. 15-20 amino acids) affording high-affinity lanthanide ion binding, and X-ray fluorescence microscopy (XFM). This approach enables visualization of LBT-tagged proteins while simultaneously measuring the elemental distribution in cells at a spatial resolution necessary for visualizing cell membranes and eukaryotic subcellular organelles.

In this report, we have applied a facile, ligand-free, ambient synthesis protocol toward the fabrication of not only a series of lead-free Ge-based perovskites with the general formulation of MA 1- x FA x GeI 3 (where x was changed from 0, 0.25, 0.5, 0.75, to 1) but also CsGeI 3 . Specifically, our methodology for producing ABX 3 systems is generalizable, regardless of the identity of either the A site cation or the X site halide ion. Moreover, it incorporates many advantages, including (i) the possibility of efficiently generating pure Ge-based perovskite particles of any desired chemical composition, (ii) the use of readily available, commercial precursors and comparatively lower toxicity solvents, (iii) the practicality of scale up, and (iv) the elimination of the need for any superfluous organic surface ligands or surfactants. In addition to providing mechanistic insights into their formation, we have examined the chemical composition, crystallite size, morphology, surface attributes, oxidation states, and optical properties of our as-prepared perovskites using a combination of diffraction, microscopy, and spectroscopy techniques. Specifically, we noted that the optical band gap could be reliably tuned as a function of chemical composition, via the identity of the A site cation. Moreover, we have probed their stability, not only under standard storage conditions but also, for the first time, when subjected to both e-beam- and X-ray-induced degradation, using cumulative data from sources such as synchrotron-based scanning hard X-ray microscopy. Importantly, of relevance for the potential practical incorporation of these Pb-free perovskites, our work has emphasized the possibility of controlling the chemical composition within Ge-based perovskites as a means of rationally tuning their observed band gaps and optical behavior., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

III-As nanowires are candidates for near-infrared light emitters and detectors that can be directly integrated onto silicon. However, nanoscale to microscale variations in structure, composition, and strain within a given nanowire, as well as variations between nanowires, pose challenges to correlating microstructure with device performance. In this work, we utilize coherent nanofocused X-rays to characterize stacking defects and strain in a single InGaAs nanowire supported on Si. By reconstructing diffraction patterns from the 21̅1̅0 Bragg peak, we show that the lattice orientation varies along the length of the wire, while the strain field along the cross-section is largely unaffected, leaving the band structure unperturbed. Diffraction patterns from the 011̅0 Bragg peak are reproducibly reconstructed to create three-dimensional images of stacking defects and associated lattice strains, revealing sharp planar boundaries between different crystal phases of wurtzite (WZ) structure that contribute to charge carrier scattering. Phase retrieval is made possible by developing multiangle Bragg projection ptychography (maBPP) to accommodate coherent nanodiffraction patterns measured at arbitrary overlapping positions at multiple angles about a Bragg peak, eliminating the need for scan registration at different angles. The penetrating nature of X-ray radiation, together with the relaxed constraints of maBPP, will enable the in operando imaging of nanowire devices.