Anomalous oriented attachment growth behavior on SnO2 nanocrystals

This work reports a detailed characterization of an anomalous oriented attachment behaviour for SnO2 nanocrystals. Our results evidenced an anisotropic growth for two identical 〈110〉 directions, which are equivalent according to the SnO2 crystallographic structure symmetry. A hypothesis is proposed to describe this behaviour

Impact of occlusion duration on the success rate and outcomes of percutaneous coronary intervention in chronic total occlusions

ABSTRACTBackgroundInitial studies have shown that old occlusions or those with indeterminate occlusion duration have been associated with percutaneous coronary intervention (PCI) failure and a worse prognosis. This study aimed to determine the impact of occlusion duration on the success and outcomes of contemporary PCI on chronic total occlusion (CTO).MethodsThe authors analyzed a retrospective cohort of consecutive patients submitted to PCI in CTO, who were compared according to the confirmed occlusion duration (COD) < 12 months, ≥ 12 months, or indeterminate occlusion duration (IOD).ResultsA total of 168 patients were treated, 122 (72.6%) with COD (80 < 12 months, 42 ≥ 12 months) and 46 (24.7%) with an IOD. Lesion extension was 17.0 ± 13.6mm, in 2.90 ± 0.58mm vessels, and the anterograde approach was used in 98.8% of cases. Angiographic success was attained in 79.2% of patients (80.0% vs. 73.8% vs. 82.6%; p = 0.73). The main cause of failure was the inability to cross the lesion with the guidewire (68.6%). Occlusion duration had no impact on in-hospital events (4.8% vs. 7.1% vs. 6.0%; p = 0.73), which were almost entirely explained by periprocedural myocardial infarction, or on late outcomes (18.8% vs. 7.1% vs. 15.3%; p = 0.23). At the multivariate analysis, lesion length ≥ 20mm (odds ratio - OR = 7.27; 95% confidence interval - 95% IC 1.94-29.1; p = 0.003), calcification (OR = 4.72; 95% CI 1.19-19.1; p = 0.02), and tortuosity of the occluded segment (OR = 15.98; 95% CI 2.18-144.7; p = 0.007) were predictors of failure.ConclusionsOcclusion duration was not associated with increased failure rate of the procedure or worse PCI outcomes in CTO

Using a fast hybrid pixel detector for dose-efficient diffraction imaging beam-sensitive organic molecular thin films

We discuss the benefits and showcase the applications of using a fast, hybrid-pixel detector (HPD) for 4D-STEM experiments and emphasize that in diffraction imaging the structure of molecular nano-crystallites in organic solar cell thin films with a dose-efficient modality 4D-scanning confocal electron diffraction (4D-SCED). With 4D-SCED, spot diffraction patterns form from an interaction area of a few nm while the electron beam rasters over the sample, resulting in high dose effectiveness yet highly demanding on the detector in frame speed, sensitivity, and single-pixel count rate. We compare the datasets acquired with 4D-SCED using a fast HPD with those using state-of-the-art complementary metal-oxide-semiconductor (CMOS) cameras to map the in-plane orientation of π -stacking nano-crystallites of small molecule DRCN5T in a blend of DRCN5T: PC _71 BM after solvent vapor annealing. The high-speed CMOS camera, using a scintillator optimized for low doses, showed impressive results for electron sensitivity and low noise. However, the limited speed restricted practical experimental conditions and caused unintended damage to small and weak nano-crystallites. The fast HPD, with a speed three orders of magnitude higher, allows a much higher probe current yet a lower total dose on the sample, and more scan points cover a large field of view in less time. A lot more faint diffraction signals that correspond to just a few electron events are detected. The improved performance of direct electron detectors opens more possibilities to enhance the characterization of beam-sensitive materials using 4D-STEM techniques

Nanotubes from Chalcogenide Misfit Compounds: Sn–S and Nb–Pb–S

Carbon fullerenes and nanotubes revolutionized understandingof the reactivity of nanoscale compounds. Subsequently, our group and others discovered analogous inorganic compounds with hollow, closed nanostructures. Such inorganic nanostructures offer many applications, particularly in the energy and electronics industries.One way to create inorganic nanostructures is via misfit layer-ed compounds (MLC), which are stacks of alternating two-dimensional molecular slabs, typically held together via weak van der Waals forces. They contain “misfits” in their a–b plane structures that can make them unstable, leading to collapse of the slabs into tubular nanostructures. For example, metal chalcogenide MLCs of the general formula (MX)1+y/TX2 (M = Sn, Pb, Bi, Sb, and other rare earths; T = Sn, Ti, V, Cr, Nb, Ta, etc.; X = S or Se) consist of a superstructure of alternating layers where the MX unit belongs to a (distorted NaCl) orthorhombic symmetry group (O), the TX2 layer possesses trigonal (T) or octahedral symmetry, and the two layers are held together via both van der Waals and polar forces. A misfit in the a axis or both a and b axes of the two sublattices may lead to the formation of nanostructures as the lattices relax via scrolling. Previous research has also shown that the abundance of atoms with dangling bonds in the rims makes nanoparticles of compounds with layered structure unstable in the planar form, and they tend to fold into hollow closed structures such as nanotubes.This Account shows that combining these two triggers, misfits and dangling bond annihilation in the slab rims, leads to new kinds of nanotubes from MLCs. In particular, we report the structure of two new types of nanotubes from misfits, namely, the SnS/SnS2 and PbS/NbS2 series. To decipher the complex structures of these nanotubes, we use a range of methods: high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED) analyses, scanning electron microscopy (SEM), and Cs-corrected scanning transmission electron microscopy (STEM) in the high-angle annular dark-field mode (HAADF). In both new types, the lattice mismatch between the two alternating sublayers dictates the relative layer-stacking order and leads to a variety of chiral tubular structures. In particular, the incommensuration (a type of misfit) of the SnS2/SnS system in both the (in plane) a and b directions leads to a variety of relative in-plane orientation and stacking orders along the common c-axis. Thus the SnS/SnS2 nanotubes form superstructures with the sequence O–T and O–T–T, and mixtures thereof. We also report nanotubes of the misfit layered compound (PbS)1.14NbS2, and of NbS2 intercalated with Pb atoms, with the chemical formula PbNbS2. Thus, the possibility to use two kinds of folding mechanisms jointly offers a new apparatus for the synthesis of unique 1-D nanostructures of great complexity and a potentially large diversity of physicochemical properties

Electrochemically Induced Ostwald Ripening in Au/TiO 2_{2} Nanocomposite

The report describes the Ostwald ripening process in a nanocomposite comprising gold nanoparticles and TiO2 semiconductor under electrochemical conditions. The phenomenon is considered in relation to previous observations on the Ostwald ripening process in metallic nanostructures. Possible processes involved are discussed, and a mechanism is proposed based on the size dependence of the electrochemical parameters of gold nanostructures

Analysis of Dopant Atom Distribution and Quantification of Oxygen Vacancies on Individual Gd-Doped CeO 2 Nanocrystals

This work reports the analysis of the distribution of Gd atoms and the quantification of O vacancies applied to individual CeO2 and Gd-doped CeO2 nanocrystals by electron energy-loss spectroscopy. The concentration of O vacancies measured on the undoped system (6.3±2.6 %) matches the expected value given the typical Ce3+ content previously reported for CeO2 nanoparticles. The doped nanoparticles have an uneven distribution of dopant atoms and an atypical amount of O vacant sites (37.7±4.1 %). The measured decrease of the O content induced by Gd doping cannot be explained solely by the charge balance including Ce3+ and Gd3+ ions

Nanotubes from Chalcogenide Misfit Compounds: Sn–S and Nb–Pb–S

Carbon fullerenes and nanotubes revolutionized understandingof the reactivity of nanoscale compounds. Subsequently, our group and others discovered analogous inorganic compounds with hollow, closed nanostructures. Such inorganic nanostructures offer many applications, particularly in the energy and electronics industries.One way to create inorganic nanostructures is via misfit layer-ed compounds (MLC), which are stacks of alternating two-dimensional molecular slabs, typically held together via weak van der Waals forces. They contain “misfits” in their <i>a</i>–<i>b</i> plane structures that can make them unstable, leading to collapse of the slabs into tubular nanostructures. For example, metal chalcogenide MLCs of the general formula (MX)_1+<i>y</i>/TX₂ (M = Sn, Pb, Bi, Sb, and other rare earths; T = Sn, Ti, V, Cr, Nb, Ta, etc.; X = S or Se) consist of a superstructure of alternating layers where the MX unit belongs to a (distorted NaCl) orthorhombic symmetry group (O), the TX₂ layer possesses trigonal (T) or octahedral symmetry, and the two layers are held together via both van der Waals and polar forces. A misfit in the <i>a</i> axis or both <i>a</i> and <i>b</i> axes of the two sublattices may lead to the formation of nanostructures as the lattices relax via scrolling. Previous research has also shown that the abundance of atoms with dangling bonds in the rims makes nanoparticles of compounds with layered structure unstable in the planar form, and they tend to fold into hollow closed structures such as nanotubes.This Account shows that combining these two triggers, misfits and dangling bond annihilation in the slab rims, leads to new kinds of nanotubes from MLCs. In particular, we report the structure of two new types of nanotubes from misfits, namely, the SnS/SnS₂ and PbS/NbS₂ series. To decipher the complex structures of these nanotubes, we use a range of methods: high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED) analyses, scanning electron microscopy (SEM), and Cs-corrected scanning transmission electron microscopy (STEM) in the high-angle annular dark-field mode (HAADF). In both new types, the lattice mismatch between the two alternating sublayers dictates the relative layer-stacking order and leads to a variety of chiral tubular structures. In particular, the incommensuration (a type of misfit) of the SnS₂/SnS system in both the (in plane) <i>a</i> and <i>b</i> directions leads to a variety of relative in-plane orientation and stacking orders along the common <i>c</i>-axis. Thus the SnS/SnS₂ nanotubes form superstructures with the sequence O–T and O–T–T, and mixtures thereof. We also report nanotubes of the misfit layered compound (PbS)_1.14NbS₂, and of NbS₂ intercalated with Pb atoms, with the chemical formula PbNbS₂. Thus, the possibility to use two kinds of folding mechanisms jointly offers a new apparatus for the synthesis of unique 1-D nanostructures of great complexity and a potentially large diversity of physicochemical properties

Stable colloidal suspensions of nanostructured zirconium oxide synthesized by hydrothermal process

Abstract Nanocrystalline zirconium oxide was synthesized by hydrothermal treatment of ZrO(NO 3 ) 2 and ZrOCl 2 aqueous solutions at different temperatures and time in presence of hydrogen peroxide. Hydrothermal treatment of zirconium salts (0.25 and 0.50 mol L -1 ) produced nanocrystalline monoclinic ZrO 2 powders with narrow size distribution, which were formed by the attachment of the smaller particles with crystallites size of 3.5 nm, estimated by means of the Scherrer&apos;s equation and confirmed by transmission electronic microscopy. Typical monoclinic zirconium oxide X-ray powder diffraction patterns and Raman spectra were obtained for all the crystalline powders. It was observed that the crystallization depends strongly on the temperature, resulting in amorphous material when the synthesis was realized at 100°C, and crystalline with monoclinic phase when synthesized at 110°C, independently of the salt used. Zirconium oxide colloidal nanoparticles were formed only at hydrothermal treatments longer than 24 h. The stability of the colloids was successfully characterized of zeta potential, showing an initial value of ? 59.2 mV in acid media and isoelectric point at pH = 5.2, in good agreement with previous studies

Dopant segregation analysis on Sb:SnO2 nanocrystals

The development of reliable nanostructured devices is intrinsically dependent on the description and manipulation of materials properties at the atomic scale. Consequently, several technological advances are dependent on improvements in the characterization techniques and in the models used to describe the properties of nanosized materials as a function of the synthesis parameters. The evaluation of doping element distributions in nanocrystals is directly linked to fundamental aspects that define the properties of the material, such as surface-energy distribution, nanoparticle shape, and crystal growth mechanism. However, this is still one of the most challenging tasks in the characterization of materials because of the required spatial resolution and other various restrictions from quantitative characterization techniques, such as sample degradation and signal-to-noise ratio. This paper addresses the dopant segregation characterization for two antimony-doped tin oxide (Sb:SnO2 ) systems, with different Sb doping levels, by the combined use of experimental and simulated highresolution transmission electron microscopy (HRTEM) images and surface-energy ab initio calculations. The applied methodology provided threedimensional models with geometrical and compositional information that were demonstrated to be self-consistent and correspond to the systems mean properties. The results evidence that the dopant distribution configuration is dependent on the system composition and that dopant atom redistribution may be an active mechanism for the overall surface-energy minimization