The Tortoise beetle Charidotella egregia is able to modify the structural colour of its cuticle reversibly, when disturbed by stressful external events. After field observations, measurements of the optical properties in the two main stable colour states and SEM and TEM investigations, a physical mechanism is proposed to explain the colour switching on this insect. It is shown that the gold colouration (rest state) arises from a chirped multilayer reflector maintained in a perfect coherent state by the presence of humidity in the porous patches within each layer, while the red colour (disturbed state) results from the destruction of this reflector by the expulsion of the liquid from the porous patches, turning the multilayer into a translucent slab that leaves a view on a deeper-lying pigmental red substrate. This mechanism not only explains the change of hue but also the change of scattering mode from specular to diffuse. Quantitative modelling is developed in support of this analysis.

A H-bond-driven, noncovalent, reversible solubilization/functionalization of multiwalled carbon nanotubes (MWCNTs) in apolar organic solvents (CHCl(3), CH(2)Cl(2), and toluene) has been accomplished through a dynamic combination of self-assembly and self-organization processes leading to the formation of supramolecular polymers, which enfold around the outer wall of the MWCNTs. To this end, a library of phenylacetylene molecular scaffolds with complementary recognition sites at their extremities has been synthesized. They exhibit triple parallel H-bonds between the NH-N-NH (DAD) functions of 2,6-di(acetylamino)pyridine and the CO-NH-CO (ADA) imidic groups of uracil derivatives. These residues are placed at 180° relative to each other (linear systems) or at 60°/120° (angular modules), in order to tune their ability of wrapping around MWCNTs. Molecular Dynamics (MD) simulations showed that the formation of the hybrid assembly MWCNT•[X•Y](n) (where X = 1a or 1b -DAD- and Y = 2, 3, or 4 -ADA-) is attributed to π-π and CH-π interactions between the graphitic walls of the carbon materials and the oligophenyleneethynylene polymer backbones along with its alkyl groups, respectively. Addition of polar or protic solvents, such as DMSO or MeOH, causes the disruption of the H-bonds with partial detachment of the polymer from the CNTs, followed by precipitation. Taking advantage of the chromophoric and luminescence properties of the molecular subunits, the solubilization/precipitation processes have been monitored by UV-vis absorption and luminescence spectroscopies. All hybrid MWCNTs-polymer materials have been also structurally characterized via thermogravimetric analysis (TGA), transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS).

The effect of annealing of Co∕ZnO(0001) was studied by scanning tunneling microscopy, low energy electron diffraction, and Auger electron spectroscopy. At room temperature, Co forms islands on ZnO. Annealing up to 940K leads to coalescence of the islands. At 970K, Co diffuses into ZnO where it partially replaces Zn. A model of the Auger intensities, based on exponential attenuation with thickness and including correction for matrix effects, confirms this interpretation and suggests that the fraction of Zn replaced by Co is near 50% or higher.

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