Elemental (im-)miscibility determines phase formation of multinary nanoparticles co-sputtered in ionic liquids

Non-equilibrium synthesis methods allow to alloy bulk-immiscible elements into multinary nanoparticles, which broadens the design space for new materials.Whereas sputtering onto solid substrates can combine immiscible elements into thin film solid solutions, this is not clear for sputtering of nanoparticles in ionicliquids. Thus, the suitability of sputtering in ionic liquids for producing nanoparticles of immiscible elements is investigated by co-sputtering the systems Au-Cu (miscible), Au-Ru and Cu-Ru (both immiscible), and Au-Cu-Ru on the surface of the ionic liquid 1-butyl-3-methylimidazolium bis-trifluoromethylsulfonyl)imide [Bmim][(Tf)2N]. The sputtered nanoparticles were analyzed to obtain (i) knowledge concerning the general formation process ofnanoparticles when sputtering onto ionic liquid surfaces and (ii) information, if alloy nanoparticles of immiscible elements can be synthesized as well as (iii)evidence if the Hume-Rothery rules for solid solubility are valid for sputtered nanoparticles. Accompanying atomistic simulations using density-functional theoryfor clusters of different size and ordering confirm that the miscibility of Au-Cu and the immiscibility of Au-Ru and Cu-Ru govern the thermodynamic stabilityof the nanoparticles. Based on the matching experimental and theoretical results for the NP/IL-systems concerning NP stability, a formation model of multinaryNPs in ILs was developed

Analysis of multinary nanoparticles combinatorially sputtered in ionic liquids in terms of formation, stabilization, properties and large-scale synthesis

Metallic nanoparticles (NPs) are multifunctional materials with many interesting characteristics and applications due to the unique physical conditions arising at the nanoscale. NPs can be synthesized in ionic liquids (ILs) by sputtering elements onto these liquids, however, there are still open questions for this method regarding the formation and properties of the synthesized NPs. Therefore, the formation process of sputtered NPs in ILs as well as the influence of pure ILs and IL mixtures on NP properties with respect to their size and, for multinary (co-sputtered) NPs additionally in dependence of the miscibility of the combined elements, their composition were investigated in this dissertation. Furthermore, the potential of sputtering on ILs for large-scale NP fabrication was tested and the NP were investigated directly in the stabilizing IL using synchrotron radiation.Metallische Nanopartikel (NP) sind multifunktionale Materialien mit vielen interessanten Eigenschaften und Anwendungen, welche auf den im Nanobereich auftretenden einzigartigen physikalischen Charakteristika basieren. NP können in ionischen Flüssigkeiten (ILs) durch das Sputtern von Elementen auf diese Flüssigkeiten synthetisiert werden, allerdings gibt es für diese Methode noch offene Fragen hinsichtlich der Bildung und Eigenschaften der hergestellten NP. Deshalb wurde im Rahmen dieser Dissertation der Bildungssprozess von gesputterten NP in ILs sowie der Einfluss von reinen ILs und IL-Mischungen auf die NP-Eigenschaften bezüglich deren Größe und, für multinäre (co-gesputterte) NP zusätzlich in Abhängigkeit der Mischbarkeit der kombinierten Elemente, deren Zusammensetzung untersucht. Darüber hinaus wurden das Potential von Sputtern auf ILs für eine NP-Herstellung im großen Maßstab getestet und die NP mittels Synchrotronstrahlung direkt in der stabilisierenden IL untersucht

On the effects of diluted and mixed ionic liquids as liquid substrates for the sputter synthesis of nanoparticles

The synthesis of nanoparticles by combinatorial sputtering in ionic liquids is a versatile approach for discovering new materials. Whereas the influence on nanoparticle formation of different pure ionic liquids has been addressed, the influence of (I) dilution of ionic liquid with solvents and (II) different mixtures of ionic liquids is less known. Therefore, mixtures of the ionic liquid $[Bmim][(Tf)_{2}N]$ with the organic solvent anisole and other ionic liquids $([Bmim][(Pf)_{2}N]$, $[BmPyr][(Tf)_{2}N]$ were used as liquid substrates for the sputter synthesis of nanoparticles, in order to investigate the influence of these mixtures on the size of the nanoparticles. First, mixtures of anisole with a suspension of sputtered Ag nanoparticles in $[Bmim][(Tf)_{2}N]$ were prepared in different volumetric steps to investigate if the stabilization of the NPs by the ionic liquid could be reduced by the solvent. However, a continuous reduction in nanoparticle size and amount with increasing anisole volume was observed. Second, Ag, Au and Cu were sputtered on ionic liquid mixtures. Ag nanoparticles in $[Bmim][(Tf)_{2}N]/[Bmim][(Pf)_{2}N]$ mixtures showed a decrease in size with the increasing volumetric fraction of $[Bmim][(Tf)_{2}N]$, whereas all nanoparticles obtained from $[Bmim][(Tf)_{2}N]/[BmPyr][(Tf)_{2}N]$ mixtures showed increasing size and broadening of the size distribution. Maximum sizes of sputtered Ag and Au NPs were reached in mixtures of $[Bmim][(Tf)_{2}N]$ with 20 vol.% and 40 vol.% $[BmPyr][(Tf)_{2}N]$. The results indicate that ionic liquid mixtures with different portions of cations and anions have the capability of influencing the ionic liquid stabilization characteristics with respect to, e.g., nanoparticle size and size distribution

Enhanced antibacterial performance of ultrathin silver/platinum nanopatches by a sacrificial anode mechanism

The development of antibacterial implant surfaces is a challenging task in biomaterial research. We fabricated a highly antibacterial bimetallic platinum (Pt)/silver(Ag) nanopatch surface by short time sputtering of Pt and Ag on titanium. The sputter process led to a patch-like distribution with crystalline areas in the nanometer-size range (1.3–3.9 nm thickness, 3–60 nm extension). Structural analyses of Pt/Ag samples showed Ag- and Pt-rich areas containing nanoparticle-like Pt deposits of 1–2 nm. The adhesion and proliferation properties of S. aureus on the nanopatch samples were analyzed. Consecutively sputtered Ag/Pt nanopatches (Pt followed by Ag) induced enhanced antimicrobial activity compared to co-sputtered Pt/Ag samples or pure Ag patches of similar Ag amounts. The underlying sacrificial anode mechanism was proved by linear sweep voltammetry. The advantages of this nanopatch coating are the enhanced antimicrobial activity despite a reduced total amount of Ag/Pt and a self-limited effect due the rapid Ag dissolution

Design of complex solid‐solution electrocatalysts by correlating configuration, adsorption energy distribution patterns, and activity curves

Complex solid‐solution electrocatalysts (also referred to as high‐entropy alloy) are gaining increasing interest owing to their promising properties which were only recently discovered. With the capability of forming complex single‐phase solid solutions from five or more constituents, they offer unique capabilities of fine‐tuning adsorption energies. However, the elemental complexity within the crystal structure and its effect on electrocatalytic properties is poorly understood. We discuss how addition or replacement of elements affect the adsorption energy distribution pattern and how this impacts the shape and activity of catalytic response curves. We highlight the implications of these conceptual findings on improved screening of new catalyst configurations and illustrate this strategy based on the discovery and experimental evaluation of several highly active complex solid solution nanoparticle catalysts for the oxygen reduction reaction in alkaline media