RESUMEN
Nanoscale materials are frequently coated with surface stabilization layers during growth that prevent flocculation in solution and facilitate processing technologies such as ink-jet device printing. Here, we show that few-nanometer-thick stabilization layers typically used swell in the presence of certain solvents and impart significant stresses to the nanomaterial that remains even after the solvent has evaporated. Solvent swelling of the surface layer dramatically enhances nanomaterial-substrate adhesion via the collapse of the stabilization layer during solvent evaporation, preventing stress relaxation. We demonstrate the stress modulation of Ag, Au, and Si nanowires functionalised with surface polymers and surfactant layers and detect strain levels between 0.1 and 0.6% using atomic force microscopy mechanical measurement and Raman spectroscopy. Dry-transferred nanowires exhibit poor adhesion and show no evidence of incorporated stress but become stressed immediately following solvent exposure. Strain engineering is demonstrated by coating nanowires with few-nanometer-thick solvent-responsive polymer layers.
RESUMEN
Crystalline aluminum oxide is a brittle ceramic material. Here we show that individual alumina nanotubes with internal and external radii of â¼15 nm and â¼50 nm, respectively and lengths of the order of 100 µm can be readily separated from amorphous alumina membranes fabricated by a hard anodisation process under a magnetic field of up to 1.5 T. The ceramic nanotubes are extremely flexible and exhibit an exceptional plasticity of ±70% at room temperature without breaking. Elastic properties investigated by the double clamped beam method include a tensile strength of 4.1 GPa, corresponding to a breaking strain of 5%. These values are respectively 17 and 70 times greater than those of polycrystalline alumina fibres. The plasticity of anodic amorphous alumina helps explain the formation of ordered arrays of nanopores in the alumina membranes.
RESUMEN
Here we have investigated the influence of the antenna group position on both the formation of chiral amphiphilic Eu(III) -based self-assemblies in CH3 CN solution and, on the ability to form monolayers on the surface of quartz substrates using the Langmuir-Blodgett technique, by changing from the 1-naphthyl (2(R), 2(S)) to the 2-naphthyl (1(R), 1(S)) position. The evaluation of binding constants of the self- assemblies in CH3 CN solution was achieved using conventional techniques such as UV/Visible and luminescence spectroscopies along with more specific circular dichroism (CD) spectroscopy. The binding constants obtained for EuL, EuL2 and EuL3 species in the case of 2-naphthyl derivatives were comparable to those obtained for 1-naphthyl derivatives. The analysis of the changes in the CD spectra of 1(R) and 1(S) upon addition of Eu(III) not only allowed us to evaluate the values of the binding constants but the resulting recalculated spectra may also be used as fingerprints for assignment of the chiral self-assembly species formed in solution. The obtained monolayers were predominantly formed from EuL3 (≈85 %) with the minor species present in ≈15 % EuL2 .
RESUMEN
In this article, we present a comprehensive investigation of the photothermal properties of plasmonic nanowire networks. We measure the local steady-state temperature increase, heat source density, and absorption in Ag, Au, and Ni metallic nanowire networks under optical illumination. This allows direct experimental confirmation of increased heat generation at the junction between two metallic nanowires and stacking-dependent absorption of polarized light. Due to thermal collective effects, the local temperature distribution in a network is shown to be completely delocalized on a micrometer scale, despite the nanoscale features in the heat source density. Comparison of the experimental temperature profile with numerical simulation allows an upper limit for the effective thermal conductivity of a Ag nanowire network to be established at 43 Wm(-1) K(-1) (0.1 κbulk).
