Pascal Bockstaller

Tungsten nanoparticles from liquid-ammonia-based synthesis

Tungsten nanoparticles were obtained from liquid-ammonia-based synthesis via reduction of WCl6 with dissolved sodium. The W(0) nanoparticles exhibit a diameter of 1-2 nm and can be dispersed in alkanes, showing a grayish-orange color due to red-shifted plasmon resonance absorption.

Sodium-Naphthalenide-Driven Synthesis of Base-Metal Nanoparticles and Follow-up Reactions†

Mo(0), W(0), Fe(0), Ru(0), Re(0), and Zn(0) nanoparticles—essentially base metals—are prepared as a general strategy by a sodium naphthalenide ([NaNaph])-driven reduction of simple metal chlorides in ethers (1,2-dimethoxyethane (DME), tetrahydrofuran (THF)). All the nanoparticles have diameters ≤10 nm, and they can be obtained either as powder samples or long-term stable suspensions. Direct follow-up reactions (e.g., Mo(0)+S8, FeCl3+AsCl3, ReCl5+MoCl5), moreover, allow the preparation of MoS2, FeAs2, or Re4Mo nanoparticles of similar size as the pristine metals (≤10 nm).

Ammonia‐in‐Oil‐Microemulsions and Their Application

Liquid ammonia on the nanoscale: Ammonia-in-oil microemulsions are used to synthesize Bi, Re, CoN, and GaN nanoparticles, which can be obtained without further thermal treatment. These microemulsions are as reproducible and simple as their water-in-oil conterparts, with the exception of the required low temperature of -40 °C.

Light-induced modification of silver nanoparticles with functional polymers.

A mild, efficient and ambient temperature photochemical approach for the synthesis of silver nanoparticle core-shell structures employing a zwitterionic polymer as well as polyethylene glycol is presented.

Bulk Heterojunction Nanomorphology of Fluorenyl Hexa-peri-hexabenzocoronene–Fullerene Blend Films

In this study, the nanomorphology of fluorenyl hexa-peri-hexabenzocoronene:[6,6]-phenyl C61-butyric acid methyl ester (FHBC:PC61BM) absorber layers of organic solar cells was investigated. Different electron microscopical techniques, atomic force microscopy, and grazing incidence wide-angle X-ray scattering were applied for a comprehensive nanomorphology analysis. The development of the nanomorphology upon sample annealing and the associated change of the device performance were investigated. It was shown that the annealing process enhances the phase separation and therefore the bulk heterojunction structure. Due to π-π stacking, the FHBC molecules assemble into columnar stacks, which are already present before annealing. While the nonannealed sample consists of a mixture of homogeneously distributed PC61BM molecules and FHBC stacks with a preferential in-plane stack orientation, crystalline FHBC precipitates occur in the annealed samples. These crystals, which consist of hexagonal arranged FHBC stacks, grow with increased annealing time. They are distributed homogeneously over the whole volume of the absorber layer as revealed by electron tomography. The FHBC stacks, whether in the two phase mixture or in the pure crystalline precipitates, exhibit an edge-on orientation, according to results from grazing incidence wide-angle X-ray scattering (GIWAXS), dark-field transmission electron microscopy (DF TEM) imaging and selective area electron diffraction (SAED). The best solar cell efficiencies were obtained after 20 or 40 s sample annealing. These annealing times induce an optimized degree of phase separation between donor and acceptor material.

Comparison of the Catalytic Performance and Carbon Monoxide Sensing Behavior of Pd-SnO2 Core@Shell Nanocomposites

The catalytic activity of Pd‐SnO2 core@shell nanocomposites in the oxidation of CO and their CO‐sensing behavior were compared. For this purpose, Pd particles were placed on the inside and the outside of SnO2 hollow spheres, as demonstrated by electron tomography, X‐ray photoelectron spectroscopy, and X‐ray absorption spectroscopy. Both the sensing and catalytic effect were studied in a systematic manner on such nanocomposites, and striking differences in the catalytic performance of the nanocomposites in CO oxidation and CO and H2 sensing were found. At low temperatures, SnO2@Pd was found to be a good sensor, and the light‐off temperature was significantly lower than that of Pd@SnO2. Above the ignition temperature, CO was probably rapidly removed from the gas so that the sensing effect disappeared. This demonstrated that understanding of the sensing and catalytic behavior can help in unraveling the functional properties of core@shell and Pd‐SnO2 nanocomposites in more detail.