Preparation of Mesoporous Bimetallic Au-Pt with a Phase-Segregated Heterostructure Using Mesoporous Silica.

Mesoporous bimetallic Au-Pt with a phase-segregated heterostructure has been prepared by using mesoporous silica SBA-15 as a template. Au nanoparticles were prepared as a seed metal within the mesopores, and subsequently Pt was deposited, sandwiching the Au seeds. Energy-dispersive X-ray (EDX) spectral mapping showed that the framework of mesoporous bimetallic Au-Pt, prepared by removing the silica template with HF, was composed of Au nanoparticles joined with Pt nanowires. The Au/Pt ratio of the mesoporous bimetallic Au-Pt could be varied by controlling the number of Au deposition cycles. Pre-adsorbed CO (COad) stripping voltammetry of the mesoporous bimetallic Au-Pt showed that the surfaces of the joined bimetallic structure were electrochemically active. This could be attributed to the open framework structure having a high ratio of exposed bimetallic mesopore surfaces. The described preparative approach, involving a mesoporous silica template and stepwise deposition within the mesopores, enables control of the nanostructure of the bimetallic material, which is greatly promising for the further development of synthetic methodologies for bimetallic structures.

Platinum nanopeapods: spatial control of mesopore arrangements by utilizing a physically confined space.

Spherical mesopores: Mesoporous Pt rods containing cage-type mesopores were prepared with porous anodic alumina membranes (PAAMs). It is noteworthy that spherical mesopores are aligned in the rods due to physical confinement by the PAAM channels. Both the mesopore alignment and the morphological control are realized simultaneously, which could be important for bottom-up approaches to nanometals with desirable structural features (see figure).

Capture, store, and discharge. Shuttling photogenerated electrons across TiO2-silver interface.

UV irradiation of TiO(2) nanoparticles in the presence of Ag(+) ions results in the quantitative reduction and deposition of silver on its surface. Continued UV irradiation following the deposition of Ag on the TiO(2) surface causes a blue shift in the surface plasmon peak from 430 to 415 nm as these particles become charged with excess electrons. Under UV irradiation, both the charging and discharging of electrons occur at different rates, thus allowing the system to attain a steady state. Upon stopping the UV irradiation, a fraction of these electrons remain stored. The electron storage is dependent on the amount of Ag deposited on TiO(2) nanoparticles with maximum capacity seen at 8.6 µM of Ag in a suspension containing 5.8 mM of TiO(2). Such electron charging and discharging processes in semiconductor-metal composites need to be taken into account while evaluating the plasmon resonance induced effects in photocatalysis and photoelectrochemistry.

Pt nanoworms: creation of a bumpy surface on one-dimensional (1D) Pt nanowires with the assistance of surfactants embedded in mesochannels.

A new type of platinum nanowire with a bumpy surface "Pt nanoworm" is electrochemically synthesized in mesochannels of mesoporous silica films with the assistance of a nonionic surfactant (C(16)EO(8)).

A rational repeating template method for synthesis of 2D hexagonally ordered mesoporous precious metals.

A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor-infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen-adsorption-desorption isotherm, and small-angle X-ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft-templating methods, can be prepared. This study has overcome the composition variation limitations of the soft-templating method.

Tailored synthesis of mesoporous platinum replicas using double gyroid mesoporous silica (KIT-6) with different pore diameters via vapor infiltration of a reducing agent.

We demonstrate facile synthesis of mesoporous Pt replicas using double gyroid mesoporous silica (KIT-6) with different pore diameters via vapor infiltration of a reducing agent. Through controlling the complementary pore size, it becomes possible to selectively deposit Pt into one side pore of the Ia3d bicontinuous structure, thereby forming a mesoporous Pt replica with relatively large mesopores (over 10 nm).

Tailored electrochemical synthesis of 2D-hexagonal, lamellar, and cage-type mesostructured Pt thin films with extralarge periodicity.

We report the synthesis of mesostructured Pt films with extralarge periodicity from lyotropic liquid crystals consisting of block copolymers (polystyrene-b-polyethylene oxide, PS-b-PEO) on Au substrates by electrochemical deposition. The Pt films with three types of (two-dimensional (2D)-hexagonal, lamellar, and cage-type) mesostructures are successfully synthesized by controlling the compositional ratio between block copolymers and Pt species in precursor solutions. The mesostructured Pt films have high electrochemically active surface areas. The bumpy mesopore surfaces, which reflect the mesopore walls consisting of connected nanoparticles, greatly contribute to the enhancement of the surface areas. The mesopore walls have single crystal domains over 400 nm(2) region proved by the lattice fringes of Pt extending over several nanoparticles.

Fabrication of mesoporous Pt nanotubes utilizing dual templates under a reduced pressure condition.

Pt nanotubes with mesoporous walls have been successfully prepared for the first time by the combination of hard templates (porous anodic alumina membranes, PAAM) and soft templates (lyotropic liquid crystals, LLC).

Pt fibers with stacked donut-like mesospace by assembling pt nanoparticles: guided deposition in physically confined self-assembly of surfactants.

A stacked donut-like mesospace is successfully introduced into Pt fibers by assembling Pt nanoparticles with uniform particle size, by utilizing the guided deposition of Pt nanoparticles in preferentially oriented liquid crystals. We clearly demonstrate that the collaboration of both LLC templating by electrochemical processes and hard templating utilizing a confined effect can lead to the genesis of new nanostructured metals. Such a unique metal-based nanoarchitecture enhances the surface area and enables the high-mass transportation of guest species. Preferentially oriented mesochannels should contribute significantly to the fine control and transport of electronic carriers through metal fibers.