Bioinspired Synthesis of a Soft-Nanofilament-Based Coating Consisting of Polysilsesquioxanes/Polyamine and Its Divergent Surface Control

The synthesis of polysilsesquioxanes coating with controllable one-dimensional nanostructure on substrates remains a major long-term challenge by conventional solution-phase method. The hydrolytic polycondensation of organosilanes in solution normally produces a mixture of incomplete cages, ladderlike, and network structures, resulting in the poor control of the formation of specific nanostructure. This paper describes a simple aqueous process to synthesize nanofilament-based coatings of polysilsesquioxanes possessing various organo-functional groups (for example, thiol, methyl, phenyl, vinyl, and epoxy). We utilized a self-assembled nanostructured polyamine layer as a biomimetically catalytic scaffold/template to direct the formation of one-dimensional nanofilament of polysilsesquioxanes by temporally and spatially controlled hydrolytic polycondensation of organosilane. The surface nanostructure and morphology of polysilsesquioxane coating could be modulated by changing hydrolysis and condensation reaction conditions, and the orientation of nanofilaments of polysilsesquioxanes on substrates could be controlled by simply adjusting the self-assembly conditions of polyamine layer. The nanostructure and polyamine@polysilsesquioxane hybrid composition of nanofilament-based coatings were examined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The template role of nanostructured polyamine layer for the formation of polysilsesquioxane nanofilament was confirmed by combining thin film X-ray diffraction (XRD) and XPS measurements. Moreover, these nanotextured coatings with various organo-functional groups could be changed into superhydrophobic surfaces after surface modification with fluorocarbon molecule

Synthesis of TiO₂ Nanocoral Structures in Ever-Changing Aqueous Reaction Systems

A far-from-equilibrium strategy is developed to synthesize coral-like nanostructures of TiO₂ on a variety of surfaces. TiO₂ nanocoral structures consist of anatase base film and rutile nanowire layers, and they are continuously formed on substrates immersed in aqueous TiOSO₄–H₂O₂. The sequential deposition of TiO₂ starts with hydrolysis and condensation reactions of titanium peroxocomplexes in the aqueous phase, resulting in deposition of amorphous film. The film serves as adhesive interface on which succeeding growth of rutile nanowires to occur. This initial deposition reaction is accompanied by shift in pH of the reaction media, which is favorable condition for the growth of rutile nanocrystals. During the growth of rutile nanocoral layers, the amorphous base films are transformed to anatase phase. These sequential deposition reactions occur at temperatures as low as 80 °C, and the mild synthetic condition allows the use of a wide range of substrates such as ITO (indium tin oxide), glass, and even organic polymer films. The thickness of nanocoral layer is controllable by repeating the growth reaction of rutile nanocorals. TiO₂ nanocorals show photocatalytic activity as demonstrated by site-specific reduction of Ag­(I) ions, which proceeds preferentially on the rutile nanowire layer. The rutile nanowire layer also shows photocatalytic decomposition of acetaldehyde, which is promoted upon increase of the thickness of the nanowire layer. The use of temporally transforming reaction media allows the formation of biphasic TiO₂ nanocoral structures, and the concept of nonequilibrium synthetic approach would be widely applicable to developing structurally graded inorganic nanointerfaces

Chiral Skeletons of Mesoporous Silica Nanospheres to Mitigate Alzheimer’s β‑Amyloid Aggregation

Chiral mesoporous silica (mSiO2) nanomaterials have gained significant attention during the past two decades. Most of them show a topologically characteristic helix; however, little attention has been paid to the molecular-scale chirality of mSiO2 frameworks. Herein, we report a chiral amide-gel-directed synthesis strategy for the fabrication of chiral mSiO2 nanospheres with molecular-scale-like chirality in the silicate skeletons. The functionalization of micelles with the chiral amide gels via electrostatic interactions realizes the growth of molecular configuration chiral silica sols. Subsequent modular self-assembly results in the formation of dendritic large mesoporous silica nanospheres with molecular chirality of the silica frameworks. As a result, the resultant chiral mSiO2 nanospheres show abundant large mesopores (∼10.1 nm), high pore volumes (∼1.8 cm3·g–1), high surface areas (∼525 m2·g–1), and evident CD activity. The successful transfer of the chirality from the chiral amide gels to composited micelles and further to asymmetric silica polymeric frameworks based on modular self-assembly leads to the presence of molecular chirality in the final products. The chiral mSiO2 frameworks display a good chiral stability after a high-temperature calcination (even up to 1000 °C). The chiral mSiO2 can impart a notable decline in β-amyloid protein (Aβ42) aggregation formation up to 79%, leading to significant mitigation of Aβ42-induced cytotoxicity on the human neuroblastoma line SH-ST5Y cells in vitro. This finding opens a new avenue to construct the molecular chirality configuration in nanomaterials for optical and biomedical applications