Electron Microscopic Study on Aerosol-Assisted Synthesis of Aluminum Organophosphonates Using Flexible Colloidal PS‑<i>b</i>‑PEO Templates

A wide variety of synthetic approaches from homogeneous precursor solutions have so far been developed for precise structural design of materials in multiscale. In organic templating approaches for porous materials design, we have recently developed a new approach to fabricate colloidal polystyrene-<i>block</i>-poly­(oxyethylene) (PS-<i>b</i>-PEO) templated large pores that can be controlled in thick films of aluminum organophosphonate (AOP). In this study, we extended this approach using colloidal PS-<i>b</i>-PEO aggregates to aerosol-assisted synthesis for the fabrication of spherical particles. Structural variations (morphology and porous structure) depended on the synthetic conditions, which were mainly investigated by using electron microscopies (SEM and TEM). In addition to the insight on the colloidal PS-<i>b</i>-PEO templating of spherical pores in AOP spheres, it was found that colloidal PS-<i>b</i>-PEO aggregates were flexible for further design of pore shape that was strongly affected by external morphology. In this context, we proposed this method as flexible colloidal PS-<i>b</i>-PEO templating to fabricate unusual macroporous structures during morphological control from precursor solutions containing colloidal PS-<i>b</i>-PEO aggregates. The insights will be promising for precise construction of unique devices using porous materials templated by colloidal organic aggregates. In addition, we found a useful water adsorption–desorption behavior over the macroporous AOP bulky powders when the macropores were connected through large pores, which is also significant for future development of AOP-based porous materials

Metallic Nanocages: Synthesis of Bimetallic Pt–Pd Hollow Nanoparticles with Dendritic Shells by Selective Chemical Etching

We report a facile synthesis of Pt–Pd bimetallic nanoparticles, named “metallic nanocages”, with a hollow interior and porous dendritic shell. This synthesis is easily achieved by selective chemical etching of Pd cores from dendritic Pt-on-Pd nanoparticles. The obtained Pt–Pd nanocages show superior catalytic activity for methanol oxidation reaction compared to other Pt-based materials reported previously

Polymeric Micelle Assembly for the Direct Synthesis of Platinum-Decorated Mesoporous TiO₂ toward Highly Selective Sensing of Acetaldehyde

Platinum-decorated mesoporous TiO₂ is synthesized by the self-assembly of polymeric micelles of an asymmetric triblock copolymer with three chemically distinct units in an acidic tetrahydrofuran solution. The strong hydrophobic interaction of platinum­(II) 2,4-pentanedionate with a polystyrene core and electrostatic interaction of titanium tetraisopropoxide with a poly­(vinylpyridine) shell enable us to directly synthesize crystalline mesoporous TiO₂ with platinum nanoparticles. A thermally stable block copolymer prevents collapse of the ordered mesostructure during the calcination process. The platinum source is in situ reduced to form the platinum nanoparticles on the TiO₂ walls. The sensing performance of platinum-decorated mesoporous TiO₂ is studied in detail using a quartz crystal microbalance technique, and it is found that it shows excellent sensitivity for acetaldehyde

Preparation of Au Nanowire Films by Electrodeposition Using Mesoporous Silica Films as a Template: Vital Effect of Vertically Oriented Mesopores on a Substrate

Films consisting of polycrystalline Au nanowires were prepared by electrodeposition using mesoporous silica films with vertically oriented mesochannels as a template. The importance of the mesostructure near the surface of the substrate is emphasized by the comparison of films possessing vertically aligned mesochannels to the substrate with those having parallel aligned mesochannels from the viewpoints of Au deposition in the films and the presence or absence of the resulting cracking. When all mesopores lie parallel to the substrate, the mesoporous film was cleaved by the deposition of Au, which is in clear contrast to the case of Pt deposition. Fabricated Au nanowires are not interconnected with each other unlike Pt, irrespective of the presence of interconnected micropores

All-Metal Layer-by-Layer Films: Bimetallic Alternate Layers with Accessible Mesopores for Enhanced Electrocatalysis

We have prepared multilayer mesoporous bimetallic (Pt/Pd) alternating films by layer-by-layer (LbL) electrochemical deposition. Because of the high surface area and heterometallic interfacial atomic contacts, enhanced electrocatalytic activity for methanol oxidation reaction is realized. This novel LbL approach allows optimization of the electrocatalytic performance through precise tuning of the thickness of each layer

Superior CO Catalytic Oxidation on Novel Pt/Clay Nanocomposites

Nanostructured novel Pt/Clay nanocomposites consisting of well-defined Pt nanoparticles prepared by clay-mediated in situ reduction displays very high thermal stability, large BET surface area and superior catalytic activity for CO oxidation as compared to a model reference Pt/SiO₂ catalysts. CO oxidation has attracted renewed attention because of its technological importance in the area of pollution control. The Pt/Clay system consisting of Pt nanoparticles strongly immobilized between the atomic layers of clay inhibits nanoparticle sintering and loss of catalytic activity even after prolonged heating at high temperatures. At elevated temperatures (300 °C), the Pt/Clay system demonstrates significant enhancement of catalytic activity, with almost 100% CO conversion in less than 5 min. Emphasis is given to the role played by the clay supporting material which is chemically and thermally stable under the catalytic conditions of exhaust purification

One-Step Synthetic Strategy of Hybrid Materials from Bimetallic Metal–Organic Frameworks for Supercapacitor Applications

This work reports a facile one-step method for the synthesis of new hybrid porous materials using bimetallic NiCo-MOF-74 as the starting precursor. By controlling the calcination atmosphere and temperature, the bimetallic NiCo-MOF-74 particles can be converted into a series of hybrid materials consisting of carbon, metal, and metal oxides. The direct carbonization of the bimetallic NiCo-MOF-74 particles at 800 °C under N₂ atmosphere results in the formation of graphitic carbon/Ni<i>_x</i>Co_1−<i>x</i> composites (termed NC-800). In contrast, the heat treatment of NiCo-MOF-74 in air at 350 °C (termed NC-350) yields Ni_<i>x</i>Co_1−<i>x</i>/Ni_<i>x</i>Co_1−<i>x</i>O composites (with a small trace of carbon) as the product. When evaluated as electrode materials for supercapacitors, NC-800 and NC-350 exhibit high specific capacitances of 715 and 513 F g^–1, respectively, at a high current density of 1 A g^–1. Furthermore, these hybrid materials also show good cycling stability with no visible degradation in their specific capacitance after 2,500 cycles. The excellent electrochemical performance of these hybrid materials may be attributed to (i) the synergistic effect of the graphitic carbon and binary mixed metals which can enhance the electrical conductivity of the composites, (ii) the presence of mesopores which can facilitate easy diffusion of electrolyte, and (iii) their large surface area and pore volume which can provide significantly more electroactive sites. The outstanding electrochemical properties of these MOF-derived hybrid materials indicate their promising potential as electrode materials for high-performance supercapacitors

Tailored Design of Multiple Nanoarchitectures in Metal-Cyanide Hybrid Coordination Polymers

Recently, coordination polymers (CPs) with nanoscale porosity and unique property have demonstrated great potential in many applications. Encouraged by significant progress in the controlled synthesis of nanomaterials, such as metals and semiconductors, the morphologically controlled synthesis of CPs has been considered a potential way to further enhance the inherent properties and develop new functions. In particular, hollow-based CPs are promising nanoarchitectures that can bring several properties derived from crystalline thin shells and interior cavities. Here we demonstrate an exquisite construction method to synthesize CPs with multiple hollow-based nanoarchitectures. Through step-by-step CP crystal growth and subsequent etching processes, various types of CPs with shell-in-shell, yolk-shell, and yolk-double-shell hollow structures can be synthesized for the first time. This type of nanoarchitecture is powerful for the exploration of alternative properties of CPs. The resultant hollow-based nanoarchitectures significantly increase gas adsorption and bring out interesting magnetic properties

Phosphonate-Derived Nanoporous Metal Phosphates and Their Superior Energy Storage Application

Nanoporous nickel, aluminum, and zirconium phosphates (hereafter, abbreviated as NiP, AlP, and ZrP, respectively) with high surface areas and controlled morphology and crystallinity have been synthesized through simple calcination of the corresponding phosphonates. For the preparation of phosphonate materials, nitrilotris­(methylene)­triphosphonic acid (NMPA) is used as phosphorus source. The organic component in the phosphonate materials is thermally removed to form nanoporous structures in the final phosphate materials. The formation mechanism of nanoporous structures, as well as the effect of applied calcination temperatures on the morphology and crystallinity of the final phosphate materials, is carefully discussed. Especially, nanoporous NiP materials have a spherical morphology with a high surface area and can have great applicability as an electrode material for supercapacitors. It has been found that there is a critical effect of particle sizes, surface areas, and the crystallinities of NiP materials toward electrochemical behavior. Our nanoporous NiP material has superior specific capacitance, as compared to various phosphate nanomaterials reported previously. Excellent retention capacity of 97% is realized even after 1000 cycles, which can be ascribed to its high structural stability

Fullerene Crystals with Bimodal Pore Architectures Consisting of Macropores and Mesopores

A new class of fullerene (C₆₀) crystals with bimodal pore architectures consisting of macropores and mesopores was synthesized by using a liquid–liquid interfacial precipitation (LLIP) method involving an interface between isopropyl alcohol (IPA) and a saturated solution of C₆₀ in a mixture of benzene and carbon tetrachloride (CCl₄). By varying the mixing fraction of CCl₄ in benzene, the porosity and electrochemically active surface area can be flexibly controlled