Tin(II)sulfide
(SnS) is a well-known representative of IV–VI
semiconducting materials with a layered crystal structure. SnS is
of great interest due to its low toxicity and its optical and electrical
properties. Here, we report on the first colloidal synthesis of hexagonally
shaped single crystalline SnS nanosheets with tunable dimensions.
The SnS nanosheets crystallize in the thermodynamically preferred
orthorhombic α-phase. High-resolution transmission electron
microscopy and electron diffraction were executed in order to determine
the growth direction of these hexagonally formed nanosheets. The simple
hot-injection approach comprises the injection of a sulfur-oleylamine
complex into a hot solution mixture containing oleylamine, oleic acid,
tin(II)chloride, and hexamethyldisilazane (HMDS). HMDS is an essential
chemical for many colloidal syntheses of two-dimensional nanosheets,
but its function is not well described until now. Here, we elucidate
the function of HMDS as an essential additive for the formation of
two-dimensional nanostructures. Furthermore, we identify the role
of oleylamine and oleic acid on the formation mechanism and depict
how size and thickness of the nanosheets, as well as the crystal structure
of α-SnS to π-SnS, can be changed by the ratio of oleylamine
isomers or the amount of oleic acid. For our reaction system, we identified
the growth mechanism to follow the law of Ostwald’s step rule
(Ostwaldsche Stufenregel) instead of the oriented attachment growth
mechanism.
We present a novel,
straightforward, and reproducible method to
form tailored CuS@Au hybrid structures consisting of two-dimensional
copper sulfide nanoplatelets and gold nanoparticles that are formed
exclusively on the sides of the two-dimensional nanoplatelets. For
the realization of these dual-plasmonic structures, covellite copper
sulfide nanoplatelets are first prepared via a wet-chemical
route. In the second step, these platelets react with tetrachloroauric(III)
acid trihydrate, oleylamine, and oxalic acid dihydrate at room temperature
under a nitrogen atmosphere and in the absence of light. By varying
the amount of added gold(III) ions, not only the number and size but
also the interparticle distance between the gold nanoparticles along
the sides of the copper sulfide nanoplatelets can be tailored, which
can influence the optical properties of the hybrid structures. A combination
of scanning transmission electron microscopy, Raman spectroscopy,
and X-ray photoelectron spectroscopy on the hybrid structures prepared
at different reaction times allows for a detailed understanding of
the underlying selective gold growth on the CuS nanoplatelets and
also provides insights into the metal–semiconductor interface.
Vaporization of the solid bis(diethyldithiocarbamato)tin(ii) into pulsed RF plasma leads to the growth of crystalline, highly conductive SnS nanowalls.
An extremely efficient ethanol fuel cell electrode is produced by combining the large surface area of vertically oriented and highly conductive few-layer graphene sheets with electrochemically deposited palladium nanoparticles. The electrodes show an extraordinary high catalyst activity of up to 7977 mA/(mg Pd) at low catalyst loadings of 0.64 µg/cm² and a very high current density of up to 106 mA/cm² at high catalyst loadings of 83 µg/cm². Moreover, the low onset potentials combined with a good poisoning resistance and long-term stability make these electrodes highly suitable for real applications. These features are achieved by using a newly developed electrochemical catalyst deposition process exploiting high voltages of up to 3.5 kV. This technique allows controlling the catalyst amount ranging from a homogeneous widespread distribution of small (≤ 10 nm) palladium nanoparticles to rather dense layers of particles, while every catalyst particle has electrical contact to the graphene electrode.2
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