The costs of metal corrosion amount to several percent of the GDP of an industrialized country. [1] In the case of aluminum, chromate-based coatings [2] provide highly effective corrosion protection, but environmental regulations are increasingly restricting their use. Anodization [3] increases the thickness of the oxide layer, but it retains its porous nature.[4] Layered materials such as anionic clays (e.g., layered double hydroxides ) [5,6] and cationic clays (e.g., montmorillonite) [7] have been widely investigated as additives in organic anticorrosion coatings or as polymer-clay nanocomposite corrosion-resistant coatings. Zeolites [8,9] have also been explored as corrosion-resistant coating materials. Hydrophobic self-assembled monolayers (SAMs) [10] of surfactant molecules on the surface have recently been proposed as corrosion inhibitors but suffer from the drawbacks that the layers have limited stability and molecule-sized defects which allow water to reach the underlying surface. These problems should be mitigated if the surfactant could be incorporated in an inorganic host matrix, a thin film of which has been previously strongly bonded to the aluminum surface.Layered double hydroxides (LDHs) are one such potential inorganic host. They can be expressed by the generalwhere the cations M 2+ and M 3+ occupy the octahedral holes in a brucite-like layer and the anion A nÀ is located in the hydrated interlayer galleries.[11] The ability to vary the composition over a wide range allows materials with a wide variety of properties to be prepared. We recently showed [12] that an NiAl-LDH-CO 3 2Àfilm can be formed directly on porous anodic alumina/ aluminum (PAO/Al) substrates; since PAO/Al is the only source of Al 3+ , the thin film grows directly on the substrate and thus exhibits good adhesion and mechanical stability. [13] Treatment with sodium laurate (n-dodecanoate) results in surface-bonded laurate films showing superhydrophobicity with water contact angles (CA) greater than 1608. Here we show that intercalation of laurate anions by ion exchange with ZnAl-LDH-NO 3 À film precursors on a PAO/Al substrate leads to a hierarchical micro/nanostructured superhydrophobic film which provides a very effective corrosion-resistant coating for the underlying aluminum.The aluminum substrate was first coated with a layer of porous anodic alumina by conventional anodization and subsequently treated with an alkaline solution of zinc nitrate in the presence of an excess of nitrate anions. In addition to the peaks of the PAO/Al substrate, the XRD pattern of the film shows two low-angle reflections at 8.874 and 4.462 (Figure 1 a), which can be assigned to the [003] and [006] reflections of an LDH phase with a basal spacing of 0.887 nm, consistent with the literature for ZnAl-LDH-NO 3 À .[14] The presence of NO 3 À in the interlayer galleries of the LDH film was confirmed by the characteristic peak at 1384 cm À1 in the FTIR spectrum. It is well known that LDHs in their usual powder form readily exchange NO 3 À ions for oth...

Thermal decomposition of layered double hydroxides (LDHs) is a way of fabricating mixed metal oxide (MMO) nanocomposite materials composed of metal oxide and spinel phases. A detailed understanding of the mechanism of the transformation of the LDH precursor to the MMO should allow the properties of the resulting MMO nanocomposites to be tailored to specific applications. Here we report a systematic investigation of the structure, composition, and morphology evolution from ZnAl-LDHs to ZnO-based MMO nanocomposites composed of ZnO and ZnAl 2 O 4 on calcination at different temperatures. The nucleation and oriented growth of ZnO crystallites and the formation of ZnAl 2 O 4 were monitored by high resolution transmission electron microscopy (HRTEM) combined with selected-area electron diffraction (SAED), in situ X-ray diffraction (XRD), solid-state 27 Al magic-angle spinning nuclear magnetic resonance ( 27 Al MAS NMR), and thermogravimetric and differential thermal analyses (TG-DTA). The layered structure of the LDH precursor was maintained as the temperature was increased from room temperature to 180 °C. Upon further heating from 200 to 400 °C, ZnO nuclei doped with Al 3þ were first formed as an amorphous phase and then underwent oriented growth along the AE1010ae direction. The high aspect ratio of the LDH platelets is responsible for the oriented growth of the resulting ZnO crystallites. On further increasing the calcination temperature, Zn 2þ ions were continuously released from the amorphous phase resulting in the formation of crystalline ZnO nanoparticles doped with Al 3þ , which are homogeneously dispersed throughout the amorphous phase. When the calcination temperature reached 500 °C, Al 3þ ions were released from the ZnO-like structure resulting in the formation of ZnAl 2 O 4 spinel and the crystallinity of the spinel increased gradually with increasing temperature. Sintering of ZnO and ZnAl 2 O 4 , with concomitant loss of the platelet-like morphology, occurred below 800 °C. UV-visible spectroscopy showed that the ZnO/ZnAl 2 O 4 nanocomposite prepared by calcination of the ZnAl-LDH precursor at 800 °C has superior UV-blocking properties to both commercial ZnO and a physical mixture of ZnO and ZnAl 2 O 4 .

By means of scanning tunneling microscopy (STM), we have observed for the first time well-ordered supramolecular nanopatterns formed by mixing two complementary DNA bases: adenine (A) and thymine (T), respectively, at the liquid/solid interface. By mixing A and T at a specific mixing molar ratio, cyclic structures that were distinctly different from the structures observed by the individual base molecules separately were formed. From an interplay between the STM findings and self-consistent charge density-functional based tight-binding (SCC-DFTB) calculation method, we suggest formation of A-T-A-T quartets constructed on the basis of A-T base pairing. The formation of the A-T-A-T quartets opens new avenues to use DNA base pairing as a way to form nanoscale surface architecture and biocompatible patterned surfaces particularly via host-guest complexation that might be suitable for drug design, where the target can be trapped inside the cavities of the molecular containers.

A zinc-aluminum layered double hydroxide (ZnAl-LDH)/alumina bilayer film has been fabricated on an aluminum substrate by a one-step hydrothermal crystallization method. The LDH film was uniform and compact. XRD patterns and SEM images showed that the LDH film was highly oriented with the c-axis of the crystallites parallel to the substrate surface. The alumina layer existing between the LDH film and the substrate was formed prior to the LDH during the crystallization process. Polarization measurements showed that the bilayer film exhibited a low corrosion current density value of 10(-8) A/cm(2), which means that the LDH/alumina bilayer film can effectively protect aluminum from corrosion. Electrochemical impedance spectroscopy (EIS) showed that the impedance of the bilayer was 16 MOmega, meaning that the film served as a passive layer with a high charge transfer resistance. The adhesion between the film and the substrate was very strong which enhances its potential for practical application.

Nanostructures formed by coadsorption of the complementary DNA bases guanine (G) and cytosine (C) at a graphite surface in 1-octanol solvent were investigated by in situ scanning tunneling microscopy. The high-resolution observations showed for the first time a well-ordered coadsorption structure, attributed to rows formed from Watson-Crick G-C pairs, which was distinctly different from the structures observed for the individual G/C components. The observed coadsorption structure has been modeled by self-consistent charge density-functional-based tight-binding (SCC-DFTB) calculations, providing information on the intermolecular interactions underlying its formation.