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For the first time, shape-controlled Pt3Sn,PtSn, andPtSn2intermetallic nanocrystals were synthesized in octadecene(ODE) by a versatile hot-injection method with 1,2-hexadecanediol(HDD) as the reducing agent. Transmission electron microscopy (TEM)measurements reveal that the metal composition has an influence onthe particle morphology: with the increase in the Sn content, thePt/Sn nanoparticles obtained by the hot-injection synthesis show flower-like,irregular faceted, cubic/tetrahedral, hexagonal, and spherical/nanowirestructures. A facile phase-transfer preparative procedure for thesynthesis of Pt/Sn core/shell nanoparticles was also developed, inwhich ligand-free Pt nanoparticles were used as precursors. X-raydiffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurementsconfirm a Pt-core/Sn-shell structure. The surface characteristic ofthe Pt/Sn core/shell nanoparticles was also investigated by IR spectroscopyof CO adsorption experiments (i.e., with a highly surface sensitivetechnique). These experiments reveal a few Pt atoms to be left onthe surface as adsorption sites for CO. However, the intensity ofthe corresponding infrared (IR) bands is almost negligible. Furthermore,Pt/Sn random-alloy nanoparticles with different metal compositionsand particle sizes were synthesized in this work by heating-up methods.Energy dispersive X-ray (EDX) and XRD analyses show different alloyingextent of Sn with Pt. [ABSTRACT FROM AUTHOR]

PtSn bimetallic nanoparticles with different particle sizes (1–9 nm), metal compositions (Sn content of 10–80 mol %), and organic capping agents (e.g., amine, thiol, carboxylic acid and polymer) were synthesized by colloidal chemistry methods. Transmission electron microscopy (TEM) measurements show that, depending on the particle size, the as-prepared bimetallic nanocrystals have quasi-spherical or faceted shapes. Energy-dispersive X-ray (EDX) analyses indicate that for all samples the signals of both Pt and Sn can be detected from single nanoparticles, confirming that the products are actually bimetallic but not only a physical mixture of pure Pt and Sn metal nanoparticles. X-ray diffraction (XRD) measurements were also conducted on the bimetallic particle systems. When compared with the diffraction patterns of monometallic Pt nanoparticles, the bimetallic samples show distinct shifts of the Bragg reflections to lower degrees, which gives clear proof of the alloying of Pt with Sn. However, a quantitative analysis of the lattice parameter shifts indicates that only part of the Sn atoms are incorporated into the alloy nanocrystals. This is consistent with X-ray photoelectron spectroscopy (XPS) measurements that reveal the segregation of Sn at the surfaces of the nanocrystals. Moreover, short PtSn bimetallic nanowires were synthesized by a seed-mediated growth method with amine-capped bimetallic particles as precursors. The resulting nanowires have an average width of 2.3 nm and lengths ranging from 5 to 20 nm. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) continue to attract research interest due to their increasing applications in display and lighting markets. A current field of development is the application of solution-based deposition techniques for the organic layers. However, in general, corresponding devices do not yet reach the performance of OLEDs with vapor deposited materials. In the present work, we have used a model system with a sulfur-containing host material in the emission layer that can either be deposited by thermal evaporation or spin coating. The structure of the corresponding devices was analyzed by a combination of transmission electron microscopy and spatially resolved energy-dispersive x-ray analysis. To investigate the devices’ cross section, wedge shaped, electron transparent lamellas were prepared by focused ion beam milling. Significant differences of the spatial distribution of sulfur have been observed in the devices. [ABSTRACT FROM AUTHOR]