Surface Selective Deposition of PMMA on Layered Double Hydroxide Nanocrystals Immobilized on Solid Substrates

Abstract

Assembly of nanometer-sized particles on various solid substrates has been the focus of intense interest in the development of new integrated functional materials. Layered double hydroxides (LDHs), known as anionic or hydrotalcite-like clays, have been investigated as a multifunctional inorganic material, for example, host materials, [1] catalysts, [2] sorbents, [3] and bioinorganic [4] and polymer-inorganic composites. [5] To date in this area, most of the work performed has been on powder samples in colloidal solutions, where the bulk properties of the randomly assembled nanocrystals predominate over the contribution of the individual ones. LDH particles in the form of powders are considered one of the strongly correlated systems in the field of strong interparticle interactions [6] involving electrostatic forces as well as hydrogen bonding. These hydrophilic ensembles of LDH particles are expected to be less reactive toward incoming reactants, especially organic anions such as carboxylates. In this context, we recently introduced a novel method of controlling the face-to-face assembly of [Mg 4 Al 2 (OH) 12 ]CO 3 Á nH 2 O (MgAl-LDH) nanocrystals on Si substrates in closely packed arrays with a highly-ordered orientation, which can be used for solvothermal anion exchange to give a drastic anisotropic size change that can be observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). [7] Multilayer LDH nanocrystals on solid substrates not only make chemical reactions much more reliable, but also open up a new platform of other useful chemical interfaces difficult to achieve in a bulk system. Motivated by the need to assemble functional nanomaterials based on hybrid thin films, we demonstrate in the present study that the LDH nanocrystal organization method can provide a tunable reactive inorganic interface, depending on the liquid media and the surface characteristics of the applied substrates. We were able to precisely modify the surface potentials of the LDH nanocrystals in colloid solutions by changing the solvents, leading to the well-oriented LDH monolayer films acting as a reactive inorganic interface for the fabrication of polymer-LDH hybrid films.The hydroxide groups of LDH provide a facile route to produce the additional surface modification required to develop nanoscale inorganic composite thin films, such as superhydrophobic [8] and polymer-inorganic hybrid films.[9] Among the existing synthetic approaches to the preparation of polymer-inorganic hybrid nanocomposites, surface-initiated polymerization (SIP) allows for the high affinity of the graft polymer by employing the surface modification of the initiator on the surface of layered inorganic compounds.[10] Graft polymers generated on clay surfaces by SIP have especially attracted considerable interest because of their practical applications involving improved mechanical, thermal, and barrier properties.[11] The density of the grafting surfaces could be adjusted by employing different initiators. However, in most systems b...

Ultrasound‐Induced Rapid Intercalation of Biselenite in Layered Double Hydroxides

“…The IR spectra of the LDH-biselenite films revealed the intermolecular hydrogen bonding of the HSeO 3 -dimers because the very broad band centred around 3370 cm -1 has also been ascribed to intermolecular hydrogen bonding. [14][15][16][17][18] The present model favoured the intercalation of HSeO 3 -with a cyclic dimer structure, where the dimers were vertically oriented to the horizontal axes of the Mg-Al hydroxide layers and displayed intermolecular hydrogen-bonding. Moreover, a positive surface characteristic of the MgAl-LDH-carbonate rapidly decreased over the pH range from 7 with an isoelectric point at pH 11.…”

“…We have recently reported anisotropic 2D assemblies of LDH nanocrystals with good orientations on solid surfaces as an intercalation platform which provided the desired solvothermal anionexchange reactions in ethanol/toluene mixed solutions with protic organic acids, such as linear dicarboxylic acid and poly(acrylic acid), as guest molecules. [14][15][16][17][18] In those studies, the small amount of alcohol enabled not only solubility of the organic acids but also space for high diffusion rates into the LDH interlayer space. The morphology of the LDH particles was found to be preserved after the reactions.…”

“…The bonding between the LDH and the Si wafer can be ascribed to electrostatic attraction re- sulting from positively charged LDH particles and the negatively charged Si substrate. [14][15][16][17][18] Topotactic exchange of CO 3 2-with HSeO 3 -in the gallery space of the LDHs occurred in a 100 mm selenous acid/ethanol solution assisted by ultrasound. The SEM image of the LDH-biselenite shows that the lateral positions and the lateral size of the LDH crystals were unchanged.…”

Electrocatalysis of gold nanoparticles/layered double hydroxides nanocomposites toward methanol electro-oxidation in alkaline medium

“…At the same time, the lamellar structure and anion exchange properties of LDHs makes them attractive for technological applications as host structures for nanocomposite materials [13,14]. A large number of organic and inorganic anions or polymers have been incorporated into LDHs for different purposes [15][16][17]. However, our literature search revealed that few reports have been directed at the preparation of noble metal/LDH nanocomposites, much less their applications in the electrocatalytic field [18].…”

Morphologies, Preparations and Applications of Layered Double Hydroxide Micro-/Nanostructures

“…One advantage of fabrication of well-oriented or self-supporting LDH films is to avoid spontaneous aggregation of LDH powders. Previous studies have shown the fabrications of LDH films with microsized LDH platelets oriented perpendicularly or horizontally to the underlying metal or surface-modified substrates [21,22,23,24,25,26,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62]. With regards to orientation, 2-D LDH films can be classified into two main types: perpendicular and parallel oriented.…”