Noble-metal-free copper-zinc nanoalloy (<150 nm) is found to be uniquely suited for the highly selective catalytic conversion of 5-hydroxymethylfurfural (HMF) to potential biofuels or chemical building blocks. Clean mixtures of 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) with combined product yields up to 97 % were obtained at 200-220 °C using 20-30 bar H2 . It is also possible to convert 10 wt % HMF solutions in CPME, with an excellent DMF yield of 90 %. Milder temperatures favor selective (95 %) formation of 2,5-furandimethanol (FDM). The one-pot conversion of fructose to valuable furan-ethers was also explored. Recycling experiments for DMF production show remarkable catalyst stability. Transmission electron microscopy (TEM) characterization provides more insight into morphological changes of this intriguing class of materials during catalysis.
Stretchable
conductive films were obtained by screen printing and
thermal treatment of a homogenous ink comprising a thermally reducible
silver formate complex, an acrylate monomer, and a radical initiator.
In the curing process, both the filler nanoparticles and the polymer
matrix are generated in situ, at temperatures as low as 100 °C.
The obtained conductors, consisting of percolated silver nanoparticles
embedded in a polymeric matrix, typically show a resistivity of (2–4)
× 10–5 Ω·m. When applied on an elastomeric
substrate, the composite is stretchable up to 200% with very low R/R
0 values, which is unprecedented
for stretchable silver composite inks. Quasi-in situ confocal laser
scanning microscopy of the strained samples revealed an initial fracture
strain above 40%, which is unusually high for metal–nanoparticle
films. The described system was compared to some commercial stretchable
screen-printing inks and proved superior with regard to both R/R
0 and resistance to cyclic
tensile loading.
Optical waveguides have been fabricated via photopolymerization of stable, inkjet-printed patterns. In order to obtain high-profile lines, the properties of both the ink and the substrate were adjusted. We prove that suitable patterns, with contact angles close to 90°, can be printed by using not fully cured, "sticky" PDMS as a substrate. In addition, we propose a simple sliding-drop experiment to show the crucial difference in how the ink dewets the "sticky" and the fully cured substrate, which is otherwise difficult to demonstrate. The light attenuation vs strain curve of the obtained waveguides was determined experimentally and was found to be almost linear within the measured strain range.
We have developed a strategy for the stereoselective synthesis of cyclolignans related to podophyllotoxin and its derivatives. The crucial step of the synthesis is the photocyclization of a chiral atropoisomeric 1,2-bisbenzylidenesuccinate amide ester, which can be prepared from suitable aromatic aldehydes, diethyl succinate and l-prolinol. The photocyclization was found to be more efficient when irradiation was performed in a home-built continuous flow photochemical reactor. The in-flow irradiation also allowed us to perform the reaction on a multigram scale. The chiral auxiliary was removed by reductive cleavage with the Schwartz's reagent to give the cytotoxic 1R,2R-cis-podophyllic aldehyde, which in turn could be easily reduced to the corresponding alcohol, completing the formal synthesis of (-)-podophyllotoxin.
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