Soft Template-Based Synthesis of Mesoporous Phosphorus- and Boron-Codoped NiFe-Based Alloys for Efficient Oxygen Evolution Reaction.

Controlling the morphology, composition, and crystalline phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P- and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chemical reduction and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm-2 , which is significantly smaller than that of B-doped NiFe MNs (274 mV) and commercial RuO2 (269 mV) in alkaline electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.

Universal Electrochemical Synthesis of Mesoporous Chalcogenide Semiconductors: Mesoporous CdSe and CdTe Thin Films for Optoelectronic Applications.

Here we report the soft-template-assisted electrochemical deposition of mesoporous semiconductors (CdSe and CdTe). The resulting mesoporous films are stoichiometrically equivalent and contain mesopores homogeneously distributed over the entire surface. To demonstrate the versatility of the method, two block copolymers with different molecular weights are used, yielding films with pores of either 9 or 18 nm diameter. As a proof of concept, the mesoporous CdSe film-based photodetectors show a high sensitivity of 204 mW-1 cm2 at 680 nm wavelength, which is at least two orders of magnitude more sensitive than the bulk counterpart. This work presents a new synthesis route for nanostructured semiconductors with optical band gaps active in the visible spectrum.

Coalescence-Driven Verticality in Mesoporous TiO2 Thin Films with Long-Range Ordering.

Mesoporous semiconducting films with continuous interconnectivity and minimal tortuosity, such as densely ordered arrays of vertical channels, are ideal for ensuring a maximal surface area at the heterojunction to increase the density of charges or photons. While the design of these films with nanostructures below 50 nm using modern lithography is not feasible, continuously perpendicular pores can be obtained throughout a TiO2 film using a traditional soft-templating approach and lyotropic crystal engineering. We demonstrate here that a polystyrene-b-poly(ethylene oxide) block copolymer in a three-solvent system can self-assemble into a body-centered cubic Im3̅m template. The long-range three-dimensional periodicity of the template combined with a high degree of vertical contraction results in coalescence of the pores into orthogonal channels that are strongly interconnected with their nearest neighbors in the (011̅) plane. This work presents evidence of lateral long-range ordering with continuously transverse vertical porosity in a TiO2 material, which will enable functional applications, such as filtration, sensing, catalysis, and optoelectronics. To this end, we demonstrate the ability of the films to template and host methylammonium lead iodide perovskite nanocrystals.

Designed Patterning of Mesoporous Metal Films Based on Electrochemical Micelle Assembly Combined with Lithographical Techniques.

Mesoporous noble metals and their patterning techniques for obtaining unique patterned structures are highly attractive for electrocatalysis, photocatalysis, and optoelectronics device applications owing to their expedient properties such as high level of exposed active locations, cascade electrocatalytic sites, and large surface area. However, patterning techniques for mesoporous substrates are still limited to metal oxide and silica films, although there is growing demand for developing techniques related to patterning mesoporous metals. In this study, the first demonstration of mesoporous metal films on patterned gold (Au) substrates, prefabricated using photolithographic techniques, is reported. First, different growth rates of mesoporous Au metal films on patterned Au substrates are demonstrated by varying deposition times and voltages. In addition, mesoporous Au films are also fabricated on various patterns of Au substrates including stripe and mesh lines. An alternative fabrication method using a photoresist insulating mask also yields growth of mesoporous Au within the patterning. Moreover, patterned mesoporous films of palladium (Pd) and palladium-copper alloy (PdCu) are demonstrated on the same types of substrates to show versatility of this method. Patterned mesoporous Au films (PMGFs) show higher electrochemically active surface area (ECSA) and higher sensitivity toward glucose oxidation than nonpatterned mesoporous Au films (NMGF).

Solid/Solid Interfacial Architecturing of Solid Polymer Electrolyte-Based All-Solid-State Lithium-Sulfur Batteries by Atomic Layer Deposition.

Solid polymer electrolytes (SPEs)-based all-solid-state lithium-sulfur batteries (ASSLSBs) have attracted extensive research attention due to their high energy density and safe operation, which provide potential solutions to the increasing need for harnessing higher energy densities. There is little progress made, however, in the development of ASSLSBs to improve simultaneously energy density and long-term cycling life, mostly due to the "shuttle effect" of lithium polysulfide intermediates in the SPEs and the low interfacial compatibility between the metal lithium anode and the SPE. In this work, the issues of solid/solid interfacial architecturing through atomic layer deposition of Al2 O3 on poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide SPE surface are effectively addressed. The Al2 O3 coating promotes the suppression of lithium dendrite formation for over 500 h. ASSLSBs fabricated with two layers of Al2 O3 -coated SPE deliver high gravimetric/areal capacity and Coulombic efficiency, as well as excellent cycling stability and extremely low self-discharge rate. This work provides not only a simple and effective approach to boost the electrochemical performances of SPE-based ASSLSBs, but also enriches the fundamental understanding regarding the underlying mechanism responsible for their performance.

Metal-Organic Frameworks and Their Derived Materials: Emerging Catalysts for a Sulfate Radicals-Based Advanced Oxidation Process in Water Purification.

With the ever-growing environmental issues, sulfate radical (SO4•- )-based advanced oxidation processes (SR-AOPs) have been attracting widespread attention due to their high selectivity and oxidative potential in water purification. Among various methods generating SO4•- , employing heterogeneous catalysts for activation of peroxymonosulfate or persulfate has been demonstrated as an effective strategy. Therefore, the future advances of SR-AOPs depend on the development of adequate catalysts with high activity and stability. Metal-organic frameworks (MOFs) with large surface area, ultrahigh porosity, and diversity of material design have been extensively used in heterogeneous catalysts, and more recently, enormous effort has been made to utilize MOFs-based materials for SR-AOPs applications. In this work, the state-of-the-art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials for SR-AOPs, is summarized. The mechanisms, including radical and nonradical pathways, are also detailed in the discussion. This work will hopefully promote the future development of MOFs-based materials toward SR-AOPs applications.

Electrochemical Deposition: An Advanced Approach for Templated Synthesis of Nanoporous Metal Architectures.

Well-constructed porous materials take an essential role in a wide range of applications, including energy conversion and storage systems, electrocatalysis, photocatalysis, and sensing. Although the tailored design of various nanoarchitectures has made substantial progress, simpler preparation methods are compelled to meet large-scale production requirements. Recently, advanced electrochemical deposition techniques have had a significant impact in terms of precise control upon the nanoporous architecture (i.e., pore size, surface area, pore structure, etc.), enabling access to a wide range of compositions. In this Account, we showcase the uniqueness of electrochemical deposition techniques, detail their implementation toward the synthesis of novel nanoporous metals, and finally outline the future research directions. Nanoporous metallic structures are attractive in that they can provide high surface area and large pore volume, easing mass transport of reactants and providing high accessibility to catalytically active metal surface. The great merit of the electrochemical deposition approach does not only lie in its versatility, being applicable to a wide range of compositions, but also in the nanoscale precision it affords when it comes to crystal growth control, which cannot be easily achieved by other bottom-up or top-down approaches. In this Account, we describe the significant progress made in the field of nanoporous metal designed through electrochemical deposition approaches using hard templates (i.e., porous silica, 3D templates of polymer and silica colloids) and soft templates (i.e., lyotropic liquid crystals, polymeric micelles). In addition, we will point out how it accounts for precise control over the crystal growth and describe the unique physical and chemical properties emerging from these novel materials. Up to date, our group has reported the synthesis of several nanoporous metals and alloys (e.g., Cu, Ru, Rh, Pd, Pt, Au, and their corresponding alloys) under various conditions through electrochemical deposition, while investigating their various potential applications. The orientation of the channel structure, the composition, and the nanoporosity can be easily controlled by selecting the appropriate surfactants or block copolymers. The inherent properties of the final product, such as framework crystallinity, catalytic activity, and resistance to oxidation, are depending on both the composition and pore structure, which in turn require suitable electrochemical conditions. This Account is divided into three main sections: (i) a history of electrochemical deposition using hard and soft templates, (ii) a description of the important mechanisms involved in the preparation of nanoporous materials, and (iii) a conclusion and future perspectives. We believe that this Account will promote a deeper understanding of the synthesis of nanoporous metals using electrochemical deposition methods, thus enabling new pathways to control nanoporous architectures and optimize their performance toward promising applications such as catalysis, energy storage, sensors, and so forth.

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption.

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al2 O3 ) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al2 O3 nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al2 O3 multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al2 O3 nanosheets possess high surface areas up to 425 and 371 m2 g-1 , respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al2 O3 multilayered nanosheets exhibit Mo adsorption capacities of 33.1-40.8 mg g-1 . The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.

Fabrication of Nanoporous Carbon Materials with Hard- and Soft-Templating Approaches: A Review.

Hard- and soft-templating approaches are one of potential strategies for the fabrication of functional nanoporous carbon materials with desired morphologies and properties. Enormous efforts have been paid for understanding the synthetic mechanisms that strongly influence the materials design and applications. All of these investigations are crucial to encourage the application of hard- and soft-templating approaches for the precise synthesis of nanoporous carbon materials. In this review, we mainly summarize significant works employing different synthetic methods for making carbon materials with various pore sizes and functionalities. The content of the review article contains: (i) Hard-templating synthesis of microporous carbon from zeolites; (ii) Hard-templating synthesis of mesoporous carbon from mesoporous silica; (iii) Hard-templating synthesis of macroporous carbon; and (iv) Soft-templating synthesis of mesoporous carbon. This review aims to provide a detailed glimpse of hard- and soft-templating approaches for future development of functional nanoporous carbon materials.

Preparation of Ultraviolet Curing Type Silicone Rubbers Containing Mesoporous Silica Fillers.

Here we have been focusing on mesoporous silica (MPS) as inorganic filler material to improve the mechanical strength of silicone rubbers. The MPS particles are more effective in reducing the coefficient of thermal expansion (CTE) and hardening silicone rubber composites when compared to commercially available nonporous silica particles. In this study, we utilize ultraviolet curing type silicone rubbers and prepare MPS composites according to a simple single-step method. From an industrial viewpoint, simplifying the fabrication processes is critical. The thermal stability and mechanical strength are examined in detail in order to showcase the effectiveness of MPS particles as filler materials.

Stable Blue Luminescent CsPbBr3 Perovskite Nanocrystals Confined in Mesoporous Thin Films.

Creating CsPbBr3 perovskite nanocrystals with bright blue emission is challenging because their optical properties depend sensitively on structure. Growing perovskites in mesoporous templates bypasses some of these purification issues because the size of the nanocrystal is governed by the dimensions of the pores. Mesoporous silica consisting of aligned channels with tunable diameter can be easily synthesized and used as a template. When the perovskite solution evaporates and retreats, some of the liquid remains trapped in the interconnecting pores by discontinuous dewetting. The precursor crystallizes, generating stable ca. 3.1 nm blue-emitting perovskite nanocrystals. The mesoporous template also serves as a protective barrier to preserve the optical properties of the CsPbBr3 from atmospheric conditions. Compared to the bulk crystals and the powder composite, the strong blue-shift of the emission peak in the film is accompanied by a decrease in the longer lifetime component and an 8-fold increase in the external quantum efficiency.

Synthesis of Carbon Nanospheres Through Carbonization of Areca nut.

We demonstrate a bio-inspired one-pot synthesis of carbon nanospheres with micro-porosity achieved from a promising carbon-rich source (Areca nut) using direct pyrolysis in nitrogen atmosphere at 550 °C in a tube-furnace without adding any catalysts. The resultant carbon spheres are highly monodispersed, uniformly shaped and possess good absorption behaviour (10.5 mg · g−1) for methylene blue (MB).

Understanding chemically processed solar cells based on quantum dots.

Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum resources are now close to depletion and their combustion is known to be responsible for the release of a considerable amount of greenhouse gases and carcinogenic airborne particles. Novel third-generation solar cells include a vast range of device designs and materials aiming to overcome the factors limiting the current technologies. Among them, quantum dot-based devices showed promising potential both as sensitizers and as colloidal nanoparticle films. A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these nanostructures is also expected to result in marginal mechanisms, such as the collection of hot carriers and generation of multiple excitons, which would increase the theoretical conversion efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell with CQD films absorbing in different regions of the solar spectrum.

Layer-by-Layer Motif Architectures: Programmed Electrochemical Syntheses of Multilayer Mesoporous Metallic Films with Uniformly Sized Pores.

Although multilayer films have been extensively reported, most compositions have been limited to non-catalytically active materials (e.g. polymers, proteins, lipids, or nucleic acids). Herein, we report the preparation of binder-free multilayer metallic mesoporous films with sufficient accessibility for high electrocatalytic activity by using a programmed electrochemical strategy. By precisely tuning the deposition potential and duration, multilayer mesoporous architectures consisting of alternating mesoporous Pd layers and mesoporous PdPt layers with controlled layer thicknesses can be synthesized within a single electrolyte, containing polymeric micelles as soft templates. This novel architecture, combining the advantages of bimetallic alloys, multilayer architectures, and mesoporous structures, exhibits high electrocatalytic activity for both the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR).

Observation of Quantum Confinement in Monodisperse Methylammonium Lead Halide Perovskite Nanocrystals Embedded in Mesoporous Silica.

Hybrid organic-inorganic metal halide perovskites have fascinating electronic properties and have already been implemented in various devices. Although the behavior of bulk metal halide perovskites has been widely studied, the properties of perovskite nanocrystals are less well-understood because synthesizing them is still very challenging, in part because of stability. Here we demonstrate a simple and versatile method to grow monodisperse CH3NH3PbBrxIx-3 perovskite nanocrystals inside mesoporous silica templates. The size of the nanocrystal is governed by the pore size of the templates (3.3, 3.7, 4.2, 6.2, and 7.1 nm). In-depth structural analysis shows that the nanocrystals maintain the perovskite crystal structure, but it is slightly distorted. Quantum confinement was observed by tuning the size of the particles via the template. This approach provides an additional route to tune the optical bandgap of the nanocrystal. The level of quantum confinement was modeled taking into account the dimensions of the rod-shaped nanocrystals and their close packing inside the channels of the template. Photoluminescence measurements on CH3NH3PbBr clearly show a shift from green to blue as the pore size is decreased. Synthesizing perovskite nanostructures in templates improves their stability and enables tunable electronic properties via quantum confinement. These structures may be useful as reference materials for comparison with other perovskites, or as functional materials in all solid-state light-emitting diodes.

Ordered Mesoporous Cobalt Phosphate with Crystallized Walls toward Highly Active Water Oxidation Electrocatalysts.

A hexagonally ordered mesoporous cobalt phosphate (CoPi) material is prepared by a facile one-pot soft-templating strategy using cetyltrimethylammonium bromide template. Because of its highly accessible surface area and crystalline framework with abundant active sites, the mesoporous CoPi shows a high catalytic activity for the oxygen evolution reaction compared to previously reported noble/transition-metal and nonmetal catalysts.

Direct Assembly of Mesoporous Silica Functionalized with Polypeptides for Efficient Dye Adsorption.

Herein, we introduce a new polypeptide-functionalized mesoporous silica template fabricated from a biodegradable poly(ethylene oxide-b-ɛ-caprolactone) (PEO-b-PCL) diblock copolymer and a poly(tyrosine) (PTyr) biopolymer. The crystallization behavior of the PEO-b-PCL diblock copolymer changes after blending, but the secondary structure of PTry remains stable. After selective solvent extraction in THF, the PEO-b-PCL is removed, but PTyr remains within the silica matrix due to its different solubility. Fourier-transform IR spectroscopic analysis (FTIR), thermal gravitometry analysis (TGA), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD) studies confirm the retention of PTyr to form a polypeptide-functionalized mesoporous material. The adsorption of methylene blue hydrate (MB) from aqueous solution into the polypeptide-functionalized mesoporous silica is investigated, thus revealing that the nanocomposite exhibits a high adsorption capacity relative to pure silica due to hydrogen-bonding interactions between the hydroxy phenolic group of PTyr and the N-containing aromatic ring from MB.

A Highly Energetic N-Rich Metal-Organic Framework as a New High-Energy-Density Material.

Metal-organic framework (MOF)-based energetic material [Cu3 (MA)2 (N3 )3 ] (1; MA=melamine) was synthesized and structurally characterized (47.55 % N). The structural analysis revealed the existence of unusual multiwalled tubular channels and interweaving of single and double helical units in 1. The standard molar enthalpy of formation was found to be 1788.73 kJ mol(-1) , which is the highest value among previously reported MOF-based energetic materials. The calculated detonation properties showed that 1 can be used as a potential explosive. Sensitivity tests revealed that 1 is insensitive and thus can function as a high-energy-density material with a favorable level of safety.

Pd@Pt Core-Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction.

A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers.

Hydrogels Containing Prussian Blue Nanoparticles Toward Removal of Radioactive Cesium Ions.

Recent reports have demonstrated the practical application of Prussian blue (PB) nanoparticles toward environmental clean-up of radionuclide 173Cs. Herein, we prepared a large amount of PB nanoparticles by mixing both iron(III) chloride and sodium ferrocyanide hydrate as starting precursors. The obtained PB nanoparticles show a high surface area (440 m2. g-1) and consequently an excellent uptake ability of Cs ions from aqueous solutions. The uptake ability of Cs ions into poly(N-isopropylacrylamide (PNIPA) hydrogel is drastically increased up to 156.7 m2. g-1 after incorporating our PB nanoparticles, compared to 30.2 m2 . g-1 after using commercially available PB. Thus, our PB-containing PNIPA hydrogel can be considered as an excellent candidate for the removal of Cs ions from aqueous solutions, which will be useful for the remediation of the nuclear waste.