Quantum dot attachment and morphology control by carbon nanotubes

Novel applications in nanotechnology rely on the design of tailored nano-architectures. For this purpose, carbon nanotubes and nanoparticles are intensively investigated. In this work we study the influence of non-functionalized carbon nanotubes on the synthesis of CdSe nanoparticles by means of organometallic colloidal routes. This new synthesis methodology does not only provide an effective path to attach nanoparticles non-covalently to carbon nanotubes but represents also a new way to control the shape of nanoparticles.Comment: 6 pages, 6 figure

Function Follows Form: From Semiconducting to Metallic toward Superconducting PbS Nanowires by Faceting the Crystal

In the realm of colloidal nanostructures, with its immense capacity for shape and dimensionality control, the form is undoubtedly a driving factor for the tunability of optical and electrical properties in semiconducting or metallic materials. However, influencing the fundamental properties is still challenging and requires sophisticated surface or dimensionality manipulation. In this work, we present such a modification for the example of colloidal lead sulphide nanowires. We show that the electrical properties of lead sulphide nanostructures can be altered from semiconducting to metallic with indications of superconductivity, by exploiting the flexibility of the colloidal synthesis to sculpt the crystal and to form different surface facets. A particular morphology of lead sulphide nanowires has been synthesized through the formation of {111} surface facets, which shows metallic and superconducting properties in contrast to other forms of this semiconducting crystal, which contain other surface facets ({100} and {110}). This effect, which has been investigated with several experimental and theoretical approaches, is attributed to the presence of lead rich {111} facets. The insights promote new strategies for tuning the properties of crystals as well as new applications for lead sulphide nanostructures.Comment: 23 pages, 6 figure

Growth and reductive transformation of a gold shell around pyramidal cadmium selenide nanocrystals

We report the growth of an unstable shell-like gold structure around dihexagonal pyramidal CdSe nanocrystals in organic solution and the structural transformation to spherical domains by two means: i) electron beam irradiation (in situ) and (ii) addition of a strong reducing agent during synthesis. By varying the conditions of gold deposition, such as ligands present or the geometry of the CdSe nanocrystals, we were able to tune the gold domain size between 1.4 nm to 3.9 nm and gain important information on the role of surface chemistry in hetero nanoparticle synthesis and seed reactivity, both of which are crucial points regarding the chemical design of new materials for photocatalysis and optoelectronic applications.Comment: 5 pages, 4 figure

Single‐Crystalline Colloidal Quasi‐2D Tin Telluride

Tin telluride is a narrow‐gap semiconductor with promising properties for infrared (IR) optical applications and topological insulators. A convenient colloidal synthesis of quasi‐2D SnTe nanocrystals through the hot‐injection method in a nonpolar solvent is reported. By introducing the halide alkane 1‐bromotetradecane as well as oleic acid and trioctylphosphine, the thickness of 2D SnTe nanostripes can be tuned down to 30 nm, while the lateral dimensional can reach 6 µm. The obtained SnTe nanostripes are single crystalline with a rock‐salt crystal structure. The absorption spectra demonstrate pronounced absorption features in the IR range revealing the effect of quantum confinement in such structures

TCT-4 Efficacy and Safety of Concurrent Administration of Clopidogrel-loading (600mg) and Prasugrel-loading (60mg) in Patients with Acute ST-Segment Elevation Myocardial Infarction

Background: Current STEMI guideline recommendations limit the use of prasugrel to clopidogrel-naïve patients. However, in daily clinical practice a considerable proportion of STEMI patients undergoing primary PCI are preloaded with clopidogrel. Whether the use of prasugrel in clopidogrel pretreated STEMI patients is safe remains unknown. Similarly, the efficacy of a combined loading dose regimen has not been evaluated. Methods: Between 1 September 2009 and 15 October 2012, a total of 1,157 STEMI patients were included in the randomized COMFORTABLE AMI trial (NCT 00962416) and 891 STEMI patients in the SPUM ACS registry (NCT 01000701) at 12 centers. Patients were divided into three groups according to type of peri-procedural antiplatelet loading: (1) Clopidogrel and subsequent Prasugrel loading dose [CP], (2) Prasugrel loading dose alone [P] (3) Clopidogrel loading dose alone [C]; 23 patients were excluded because they were not exposed to Clopidogrel and Prasugrel. The primary safety endpoint was the rate of BARC type 3, 4 and 5 bleeding at 30 days. The primary efficacy endpoint was the composite of cardiac death, nonfatal MI and nonfatal stroke at 30 days. Outcomes were analyzed using Cox's Regressions (crude) and multinomial ITPW weighted Cox's Regressions. Results: A total of 2,025 patients were analysed of whom 428 (21.1%) had received CP, 447 (22.1%) patients P alone, and 1,150 (56.8%) patients C alone. The primary safety endpoint was observed among 1.2% of CP, 1.6% of P, and 1.5% of C patients (CP vs C ad. HR 0.99 (0.36-2.72), PC vs P ad. HR 0.73 (0.22-2.41). The primary safety endpoint occurred less frequently among CP (1.9%) compared with C patients (5.0%, adjusted HR 0.47 (0.22-1.00), but with similar frequency among P and C patients (2.9% vs 5.0%, ad. HR 0.68 (0.27-1.73). The net clinical benefit outcome parameter tended to be lower among CP (2.8%) compared with C patients (6.3%, ad. HR 0.56 (0.30-1.05), whereas no significant difference was observed between P and C patients (3.8% vs 6.3%, ad. HR 0.85 (0.39-1.86). Conclusions: Among STEMI patients preloaded with Clopidogrel, the concurrent administration of a Prasugrel loading dose appears safe and potentially more effective than Clopiogrel alone

Thermoelectric properties of lead chalcogenide core-shell nanostructures

We present the full thermoelectric characterization of nanostructured bulk PbTe and PbTe-PbSe samples fabricated from colloidal core-shell nanoparticles followed by spark plasma sintering. An unusually large thermopower is found in both materials, and the possibility of energy filtering as opposed to grain boundary scattering as an explanation is discussed. A decreased Debye temperature and an increased molar specific heat are in accordance with recent predictions for nanostructured materials. On the basis of these results we propose suitable core-shell material combinations for future thermoelectric materials of large electric conductivities in combination with an increased thermopower by energy filtering.Comment: 12 pages, 8 figure

Pore geometry effect on the synthesis of silica supported perovskite oxides

The formation of perovskite oxide nanoparticles supported on ordered mesoporous silica with different pore geometry is here presented. Systematic study was performed varying both pore shape (gyroidal, cylindrical, spherical) and size (7.5, 12, 17 nm) of the hosts. LaFeO$_3$, PrFeO$_3$ and LaCoO$_3$ were chosen as target guest structures. The distribution of the oxide nanoparticles on silica was comprehensively assessed using a multi-technique approach. It could be shown that the pore geometry plays a determining role in the conversion of the infiltrated metal nitrates to metal oxide. In particular, slow degradation kinetic was observed in highly curved pores, which fostered nucleation and crystallization of the guest species. In spherical pore systems the enhancement of pore size caused a remarkable delay of the decomposition of the metal salts, but at the same time improved the homogeneous distribution of the oxide particles in the matrix