RESUMO
Solvent-induced aggregates of nanoring cyclic polymers may be transferred by electrospray deposition to a surface where they adsorb as three-dimensional columnar stacks. The observed stack height varies from single rings to four stacked rings with a layer spacing of 0.32 ± 0.04 nm as measured using scanning tunneling microscopy. The flexibility of the nanorings results in distortions from a circular shape, and we show, through a comparison with Monte Carlo simulations, that the bending stiffness increases linearly with the stack height. Our results show that noncovalent interactions may be used to control the shape and mechanical properties of artificial macromolecular aggregates offering a new route to solvent-induced control of two-dimensional supramolecular organization.
Assuntos
Substâncias Macromoleculares/química , Substâncias Macromoleculares/ultraestrutura , Modelos Químicos , Modelos Moleculares , Nanopartículas/química , Nanopartículas/ultraestrutura , Porfirinas/química , Simulação por Computador , Módulo de Elasticidade , Teste de MateriaisRESUMO
The interaction of water with Fe3O4(001) is studied by density functional theory calculations including an on-site Coulomb term. For isolated molecules, dissociative adsorption is strongly promoted at surface defect sites, while at higher coverages a hydrogen-bonded network forms with alternating molecular and dissociated species. This mixed adsorption mode and a suppression of the (square root of 2 x square root of 2)R45 degrees reconstruction are confirmed by a quantitative low energy electron diffraction analysis. Adsorbate induced electron transfer processes add a new dimension towards understanding the catalytic activity of magnetite(001).
RESUMO
We show that thin films of C60 with a thickness ranging from 10 to 100 nm can promote adhesion between a Au thin film deposited on mica and a solution-deposited layer of the elastomer polymethyldisolaxane (PDMS). This molecular adhesion facilitates the removal of the gold film from the mica support by peeling and provides a new approach to template stripping which avoids the use of conventional adhesive layers. The fullerene adhesion layers may also be used to remove organic monolayers and thin films as well as two-dimensional polymers which are pre-formed on the gold surface and have monolayer thickness. Following the removal from the mica support the monolayers may be isolated and transferred to a dielectric surface by etching of the gold thin film, mechanical transfer and removal of the fullerene layer by annealing/dissolution. The use of this molecular adhesive layer provides a new route to transfer polymeric films from metal substrates to other surfaces as we demonstrate for an assembly of covalently-coupled porphyrins.
RESUMO
Stacked layers of cyclic porphyrin nanorings constitute nanoscale receptacles with variable height and diameter which preferentially adsorb sublimed molecules. Using scanning tunnelling microscopy we determine the filling capacity of these nanoring traps, and the dependence of adsorbate capture on stack height and diameter.