The structure, size, and shape of gamma-Al(2)O(3)-supported Pt nanoparticles (NPs) synthesized by inverse micelle encapsulation have been resolved via a synergistic combination of imaging and spectroscopic tools. It is shown that this synthesis method leads to 3D NP shapes even for subnanometer clusters, in contrast to the raft-like structures obtained for the same systems via traditional deposition-precipitation methods. Furthermore, a high degree of atomic ordering is observed for the micellar NPs in H(2) atmosphere at all sizes studied, possibly due to H-induced surface reconstruction in these high surface area clusters. Our findings demonstrate that the influence of NP/support interactions on NP structure can be diminished in favor of NP/adsorbate interactions when NP catalysts are prepared by micelle encapsulation methods.

An in-depth understanding of the fundamental structure of catalysts during operation is indispensable for tailoring future efficient and selective catalysts. We report the evolution of the structure and oxidation state of ZrO(2)-supported Pd nanocatalysts (∼5 nm) during the in situ reduction of NO with H(2) using X-ray absorption fine-structure spectroscopy and X-ray photoelectron spectroscopy. Prior to the onset of the reaction (≤120 °C), a NO-induced redispersion of our initial metallic Pd nanoparticles over the ZrO(2) support was observed, and Pd(δ+) species were detected. This process parallels the high production of N(2)O observed at the onset of the reaction (>120 °C), while at higher temperatures (≥150 °C) the selectivity shifts mainly toward N(2) (∼80%). Concomitant with the onset of N(2) production, the Pd atoms aggregate again into large (6.5 nm) metallic Pd nanoparticles, which were found to constitute the active phase for the H(2)-reduction of NO. Throughout the entire reaction cycle, the formation and stabilization of PdO(x) was not detected. Our results highlight the importance of in situ reactivity studies to unravel the microscopic processes governing catalytic reactivity.

We show that the noncrystalline-to-crystalline transition of supported Pt nanoparticles (NPs) in the subnanometer to nanometer size range is statistical in nature, and strongly affected by particle size, support, and adsorbates (here we use H2). Unlike in the bulk, a noncrystalline phase exists and is stable in small NPs, reflecting a general mesoscopic feature. Observations of >3000 particles by high-resolution transmission electron microscopy show a noncrystalline-to-crystalline transition zone that is nonabrupt; there is a size regime where disordered and ordered NPs coexist. The NP size at which this transition occurs is strongly dependent on both the adsorbate and the support, and this effect is general for late 5d transition metals. All results are reconciled via a statistical description of particle-support-adsorbate interactions.

Unraveling the complex interaction between catalysts and reactants under operando conditions is a key step toward gaining fundamental insight in catalysis. We report the evolution of the structure and chemical composition of size-selected micellar Pt nanoparticles (∼1 nm) supported on nanocrystalline γ-Al(2)O(3) during the catalytic oxidation of 2-propanol using X-ray absorption fine-structure spectroscopy. Platinum oxides were found to be the active species for the partial oxidation of 2-propanol (<140 °C), while the complete oxidation (>140 °C) is initially catalyzed by oxygen-covered metallic Pt nanoparticles, which were found to regrow a thin surface oxide layer above 200 °C. The intermediate reaction regime, where the partial and complete oxidation pathways coexist, is characterized by the decomposition of the Pt oxide species due to the production of reducing intermediates and the blocking of O(2) adsorption sites on the nanoparticle surface. The high catalytic activity and low onset reaction temperature displayed by our small Pt particles for the oxidation of 2-propanol is attributed to the large amount of edge and corner sites available, which facilitate the formation of reactive surface oxides. Our findings highlight the decisive role of the nanoparticle structure and chemical state in oxidation catalytic reactions.

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Background: Left ventricular thrombus(LVT) can lead to serious complications, and mostly formed after ST-Elevation myocardial infarction(STEMI). The Off-label use of new oral anticoagulants(NOACs) in the triple therapy of LVT after STEMI has increased in the past few years. As one of the most widely used NOACs, the data of safety and efficacy of rivaroxaban in LVT after STEMI is limited and warrants continued exploring.Methods: We conducted a retrospective cohort study involving STEMI patients underwent primary percutaneous coronary intervention (PCI). Among patients who developed LVT after STEMI, we evaluated the efficacy and safety of rivaroxaban plus DAPT therapy associated with thrombus resolution and clinical adverse events, compared with triple therapy with VKA. Results: In 1,335 patients with STEMI, a total of 77 (5.7%) developed LVT over the follow up period (median 25.0 months). Of the patients diagnosed with LVT, 31 patients were started on triple therapy with VKA, 33 patients on triple therapy with rivaroxaban. There was a consistent similarity in LVT resolution with rivaroxaban application compared to VKA application during the follow-up period[HR:1.57(95%CI 0.89-2.77), p=0.096; Adjusted HR:1.70(95%CI 0.90-3.22), p=0.104]. When the analysis focused on LVT resolution at different time points during the follow-up period, triple therapy with rivaroxaban showed quicker resolution than with VKA(6months:p=0.049; 12months:p=0.044; 18months:p=0.045). Meanwhile, similar risks of ISTH bleeding were recorded in both groups, with no difference between the two groups(Rivaroxaban 6.1% vs VKA 9.7% , p=0.444). Fewer net adverse clinical events(NACE) were observed in the rivaroxaban group compared with the VKA group[Rivaroxaban 24.2% vs VKA 58.1%; HR:0.31(95%CI 0.14-0.68), p=0.003; Adjusted HR: 0.23(95%CI 0.09-0.57), p=0.001].Conclusions: This observational study suggests triple therapy with rivaroxaban has similar and quicker LVT resolution in patients with LVT after STEMI, compared with triple therapy with VKA, and perhaps was accompanied with a better clinical benefit. Larger sample sizes and randomized controlled trials are needed to confirm this observation.

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A model catalyst system of Pt nanoparticles (2–5 nm) dispersed on γ-Al2O3 (111) was prepared to study the support effects on nanoparticles shape and structure by cross-sectional high-resolution electron microscopy. A dewetting equilibrium shape of Pt nanoparticles was observed with a low-index plane orientation relation: Pt(111)[211]∥γ-Al2O3(111)[211] and Pt(100)[011]∥γ-Al2O3(111)[211]. Lattice-matching epitaxy of Pt(110)∥γ-Al2O3(110) was found across their interface to maintain a minimum interface strain during particle growth. To quantitatively interpret the interfacial energy and adhesion energy of the nanoparticles, the Wulff–Kaischew theorem was applied by taking into account the γ-Al2O3 support modifications to the equilibrium shape of nanoparticles. The present approach quantitatively solved the adhesion energy of the particle/support and could help to interpret nanoparticles equilibrium shape and stability.