Correlative Light and Scanning X-Ray Scattering Microscopy of Healthy and Pathologic Human Bone Sections

Scanning small and wide angle X-ray scattering (scanning SWAXS) experiments were performed on healthy and pathologic human bone sections. Via crystallographic tools the data were transformed into quantitative images and as such compared with circularly polarized light (CPL) microscopy images. SWAXS and CPL images allowed extracting information of the mineral nanocrystalline phase embedded, with and without preferred orientation, in the collagen fibrils, mapping local changes at sub-osteon resolution. This favorable combination has been applied for the first time to biopsies of dwarfism syndrome and Paget's disease to shed light onto the cortical structure of natural bone in healthy and pathologic sections

Macromolecular Fingerprinting of Sulfolobus Species in Biofilm: A Transcriptomic and Proteomic Approach Combined with Spectroscopic Analysis

Microorganisms in nature often live in surfaceassociated sessile communities, encased in a self-produced matrix, referred to as biofilms. Biofilms have been well studied in bacteria but in a limited way for archaea. We have recently characterized biofilm formation in three closely related hyperthermophilic crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus, and S. tokodaii. These strains form different communities ranging from simple carpet structures in S. solfataricus to high density tower-like structures in S. acidocaldarius under static condition. Here, we combine spectroscopic, proteomic, and transcriptomic analyses to describe physiological and regulatory features associated with biofilms. Spectroscopic analysis reveals that in comparison to planktonic life-style, biofilm life-style has distinctive influence on the physiology of each Sulfolobus spp. Proteomic and transcriptomic data show that biofilm-forming life-style is strain specific (eg ca. 15% of the S. acidocaldarius genes were differently expressed, S. solfataricus and S. tokodaii had ∼3.4 and ∼1%, respectively). The -omic data showed that regulated ORFs were widely distributed in basic cellular functions, including surface modifications. Several regulated genes are common to biofilm-forming cells in all three species. One of the most striking common response genes include putative Lrs14-like transcriptional regulators, indicating their possible roles as a key regulatory factor in biofilm development

In situ high-Temperature X-ray diffraction study of Sc-doped titanium oxide nanocrystallites

Titanium dioxide is an inexpensive wide-gap highly ionic semiconductor with striking photocatalytic capabilities in several heterogeneous photoredox reactions. A small crystal size is desirable to maximize the surface area, since photocatalytic reactions occur at the surface of a photocatalyst. Presented here are the synthesis and microstructural characterization of 4\u2005at.% Sc-doped TiO2 (4SDT) prepared by water-based co-precipitation. The crystal structure of 4SDT was examined via in situ high-Temperature powder X-ray diffraction experiments from 25 to 1200\ub0C. Rietveld analysis revealed single-phase anatase up to 875\ub0C, while at 900\ub0C the anatase-To-rutile phase transformation occurred and at higher temperatures additional reflections of Sc-rich phases (Sc2TiO5 from 975\ub0C and Ti3Sc4O12 or Sc2O3 at 1200\ub0C) were observed. Debye function analysis (DFA) was applied to model the total scattering pattern directly in reciprocal space, allowing the reconstruction of Ti vacancies. Both Rietveld and DFA methods were applied to estimate the nanocrystallite size and shape with consistent growth in crystallite size with temperature: An ellipsoid shape with equatorial 3c4.7\u2005nm\u2005/\u2005axial (001) 3c6.9\u2005nm at 25\ub0C to equatorial 3c27.9\u2005nm\u2005/\u2005axial (001) 3c39.6\u2005nm at 900\ub0C refined by Rietveld analysis, versus a cylinder shape with D a,b = 4.3\u2005nm and size dispersion \u3c3 ab = 1.5\u2005nm, L c = 4.9\u2005nm and \u3c3 c = 2.3\u2005nm at 25\ub0C to D a,b = 21.4\u2005nm, \u3c3 ab = 8.3\u2005nm, L c = 23.9 and \u3c3 c = 10.9\u2005nm at 900\ub0C estimated by DFA. The microstructural changes obtained by Rietveld and DFA methods were supported by high-resolution transmission electron microscopy image analysis, as well as by the less direct nitrogen sorption techniques that provide information on the size of non-Agglomerated and dense particles. The Ti site-occupancy factor showed a linear increase from 0.6-0.8 at 25\ub0C to unity at 900\ub0C for anatase, and from 3c0.7 at 900\ub0C to unity at 1200\ub0C for rutile, via Rietveld analysis and DFA

Ligand-induced symmetry breaking, size and morphology in colloidal lead sulfide QDs: from classic to thiourea precursors

Colloidal lead chalcogenide quantum dots (CQDs) exhibit promising optoelectronic properties for applications in solar cell devices and as thermoelectrics. Herein, we report and discuss a ferroelectric structural distortion, at the picometer scale resolution, in PbS CQDs prepared using both classic and new synthetic pathways. The investigation was performed using synchrotron X-ray total scattering data and advanced methods of analysis that rely on a homo-core-shell model and evaluate the atomic arrangement, stoichiometry, size and morphology of nanocrystals. The CQDs show comparable size-dependent relative elongation, up to 0.7 % of one body diagonal of the cubic rock-salt structure, which corresponds to a rhombohedral lattice deformation. The findings suggest a joint role for the oleate ligands (which induce surface tensile strain) and the Pb(II) lone pair as the driving forces of the deformation. Pb displacements along the [111] direction, which provoke a ferrolectric distortion related to the lattice change, fall in the 0.0 \u2013 0.1 \uc5 range. Overall, the findings suggest the local nature of the metal off-centering, leading to different average displacements which depend on the synthetic conditions

Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots

Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar 110 facets. On varying the nature of the surface ligands, differences in lattice strains are found