A Micelle Fusion–Aggregation Assembly Approach to Mesoporous Carbon Materials with Rich Active Sites for Ultrasensitive Ammonia Sensing

Solvent-Induced Self-Assembly Strategy to Synthesize Well-Defined Hierarchically Porous Polymers

Porous polymers with well-orchestrated nanomorphologies are useful in many fields, but high surface area, hierarchical structure, and ordered pores are difficult to be satisfied in one polymer simultaneously. Herein, a solvent-induced self-assembly strategy to synthesize hierarchical porous polymers with tunable morphology, mesoporous structure, and microporous pore wall is reported. The poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer micelles are cross-linked via Friedel-Crafts reaction, which is a new way to anchor micelles into porous polymers with well-defined structure. Varying the polarity of the solvent has a dramatic effect upon the oleophobic/oleophylic interaction, and the self-assembly structure of PEO-b-PS can be tailored from aggregated nanoparticles to hollow spheres even mesoporous bulk. A morphological phase diagram is accomplished to systematically evaluate the influence of the composition of PEO-b-PS and the mixed solvent component on the pore structure and morphology of products. The hypercrosslinked hollow polymer spheres provide a confined microenvironment for the in situ reduction of K₂ PdCl₄ to ultrasmall Pd nanoparticles, which exhibit excellent catalytic performance in solvent-free catalytic oxidation of hydrocarbons and alcohols.

In situ construction of metal–organic framework (MOF) UiO-66 film on Parylene-patterned resonant microcantilever for trace organophosphorus molecules detection

UiO-66 film is directly grown on the sensing area of a resonant microcantilever for toxic organophosphorus molecules detection.

Eco-friendly and facile one-step synthesis of a three dimensional net-like magnetic mesoporous carbon derived from wastepaper as a renewable adsorbent

Millions of tons of paper and its derivatives are annually wasted without being recycled and reused. To promote the comprehensive utilization of resources and eco-friendly preparation, waste filter paper, printer paper, and napkins were chosen as carbon sources to one-step synthesize three types of three dimensional (3D) net-like magnetic mesoporous carbon (MMC) by an eco-friendly and low-cost method. These mesoporous (3.90–7.68 nm) composites have a high specific surface area (287–423 m² g⁻¹), well-developed porosity (0.24–0.74 cm³ g⁻¹) and abundant oxygen-containing functional groups. Compared to the other two composites, the adsorbent derived from filter paper showed the highest adsorption capacity towards methylene blue (MB) (q_max = 332.03 mg g⁻¹) and rhodamine B (RhB) (q_max = 389.59 mg g⁻¹) with a high adsorption rate (<5 min). According to the effect of pH value on adsorption capacity, and combining the analysis of Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy, the main adsorption mechanisms can be summarized as hydrogen bonds, electrostatic interactions, and π–π interaction. Besides, the occurrence of redox reactions between Fe²⁺/Fe⁰ and dye cannot be ignored. Finally, experiments on reusability were performed. They showed that the 3D net-like MMC could be easily regenerated and still maintained a removal efficiency of above 80% for RhB and 90% for MB after five cycles.

Millions of tons of paper and its derivatives are annually wasted without being recycled and reused.

Standing Mesochannels: Mesoporous PdCu Films with Vertically Aligned Mesochannels from Nonionic Micellar Solutions

Mesoporous bimetallic palladium (Pd) alloy films with mesochannels perpendicularly aligned to the substrate are expected to show superior electrocatalytic activity and stability. The perpendicular mesochannels allow small molecules to efficiently access the active sites located not only at the surface but also within the film because of low diffusion resistance. When compared to pure Pd films, alloying with a secondary metal such as copper (Cu) is cost-effective and promotes resistance against adventitious poisoning through intermediate reactions known to impair the electrocatalytic performance. Here, we report the synthesis of mesoporous PdCu films by electrochemical deposition in nonionic micellar solutions. The mesoporous structures are vertically aligned on the substrate, and the final content of Pd and Cu can be adjusted by tuning the initial precursor molar ratio in the electrolyte solution.

New insights into the structure-performance relationships of mesoporous materials in analytical science

Mesoporous materials are ideal carriers for guest molecules and they have been widely used in analytical science. The unique mesoporous structure provides special properties including large specific surface area, tunable pore size, and excellent pore connectivity. The structural properties of mesoporous materials have been largely made use of to improve the performance of analytical methods. For instance, the large specific surface area of mesoporous materials can provide abundant active sites and increase the probability of contact between analytes and active sites to produce stronger signals, thus leading to the improvement of detection sensitivity. The connections between analytical performances and the structural properties of mesoporous materials have not been discussed previously. Understanding the "structure-performance relationship" is highly important for the development of analytical methods with excellent performance based on mesoporous materials. In this review, we discuss the structural properties of mesoporous materials that can be optimized to improve the analytical performance. The discussion is divided into five sections according to the analytical performances: (i) selectivity-related structural properties, (ii) sensitivity-related structural properties, (iii) response time-related structural properties, (iv) stability-related structural properties, and (v) recovery time-related structural properties.

Nanostructured binary copper chalcogenides: synthesis strategies and common applications

Nanostructured binary copper chalcogenides (NBCCs) have been the subject of extensive research as promising candidates in energy-related and biological applications due to their advantageous properties, environmental compatibility, and abundance. The remarkable properties of these materials is born out of the variable stoichiometry between the copper and chalcogens, as well as the structural versatility, with zero-dimension to three-dimension structures, which consequently improves their electrical, optical, and catalytic properties. Here, the research history and development process of the binary copper chalcogenides are introduced. Typical synthesis strategies for NBCCs vary according to structure dimensionality and specific energy-related and biological applications dependent on the structure and stoichiometry are summarized. The future development of designed nanostructures and tuned stoichiometry in NBCCs for further high-performance applications are outlined.

Electrochemical Synthesis of Mesoporous Au-Cu Alloy Films with Vertically Oriented Mesochannels Using Block Copolymer Micelles

We synthesized Au-Cu bimetallic alloy films with a controlled mesoporous architecture through electrochemical deposition using an electrolyte solution containing spherical polymeric micelles. The composition of the alloy films can be easily controlled by tuning the ratio between the Au and Cu species present in the electrolyte solution. At low Cu content, cage-type mesopores are formed, reflecting the parent micellar template. Surprisingly, upon increasing the Cu content, the cage-type mesopores fuse to form vertically aligned one-dimensional mesochannels. The vertical alignment of these mesopores is favorable for enhanced mass and ion transfer within the channels due to low diffusion resistance. The atomic distribution of Au and Cu is uniform over the entire film and free of any phase segregation. The as-synthesized mesoporous Au-Cu films exhibit excellent performance as a nonenzymatic glucose sensor with high sensitivity and selectivity, and the current response is linear over a wide range of concentrations. This work identifies the properties responsible for the promising performance of such mesoporous alloy films for the clinical diagnosis of diabetes. This micelle-assisted electrodeposition approach has a high degree of flexibility and can be simply extended from monometallic compounds to a multimetallic system, enabling the fabrication of various mesoporous alloy films suitable for different applications.

Metal-Nitrogen-doped Porous Carbons Derived from Metal-Containing Ionic Liquids for Oxygen Reduction Reaction

This study describes a self-doping and additive-free strategy for the synthesis of metal-nitrogen-doped porous carbon materials (CMs) via carbonizing well-tailored precursors, metal-containing ionic liquids (M-ILs). The organic skeleton in M-ILs serves as both carbon and nitrogen sources, while metal ions acts as porogen and metallic dopants. A high nitrogen content, appropriate content of metallic species and hierarchical porosity synergistically endow the resultant CMs (MIBA-M-T) as effective electrocatalysts for the oxygen reduction reaction (ORR). MIBA-Fe-900 with a high specific surface area of 1567 m²  g^-1 exhibits an activity similar to that of Pt/C catalyst, a higher tolerance to methanol than Pt/C, and long-term durability. This work supplies a simple and convenient route for the preparation of metal-containing carbon electrocatalysts.

Ordered mesoporous NiFe2O4 with ultrathin framework for low-ppb toluene sensing

Highly sensitive and selective detection against specific target gases, especially at low-ppb (part per billion) level, remain a great number of challenges in gas sensor applications. In this paper, we first present an ordered mesoporous NiFe₂O₄ for highly sensitive and selective detection against low-ppb toluene. A series of mesoporous NiFe₂O₄ materials were synthesized by templating from mesoporous silica KIT-6 and its framework thickness was reduced from 8.5 to 5 nm by varying the pore size of KIT-6 from 9.4 to 5.6 nm, accompanied with the increase of the specific surface area from 134 to 216 m² g^-1. The ordered mesoporous NiFe₂O₄ with both ultrathin framework of 5 nm and large specific surface area of up to 216 m² g^-1 exhibits a highest response (R_gas/R_air - 1 = 77.3) toward 1,000 ppb toluene at 230 °C and is nearly 7.3 and 76.7 times higher than those for the NiFe₂O₄ replica with thick framework and its bulk counterpart respectively, which also possesses a quite low limit of detection (<2 ppb), and good selectivity.

Growth of 2D Mesoporous Polyaniline with Controlled Pore Structures on Ultrathin MoS2 Nanosheets by Block Copolymer Self-Assembly in Solution

The development of versatile strategies toward two-dimensional (2D) porous nanocomposites with tunable pore structures draws immense scientific attention in view of their attractive physiochemical properties and a wide range of promising applications. This paper describes a self-assembly approach for the directed growth of mesoporous polyaniline (PANi) with tunable pore structures and sizes on ultrathin freestanding MoS₂ nanosheets in solution, which produces 2D mesoporous PANi/MoS₂ nanocomposites. The strategy employs spherical and cylindrical micelles, which are formed by the controlled solution self-assembly of block copolymers, as the soft templates for the construction of well-defined spherical and cylindrical mesopores in the 2D PANi/MoS₂ nanocomposites, respectively. With potential applications as supercapacitor electrode materials, the resultant 2D composites show excellent capacitive performance with a maximum capacitance of 500 F g^-1 at a current density of 0.5 A g^-1, good rate performance, as well as outstanding stability for charge-discharge cycling. Moreover, the 2D mesoporous nanocomposites offer an opportunity for the study on the influence of different pore structures on their capacitive performance, which helps to understand the pore structure-property relationship of 2D porous electrode materials and to achieve their electrochemical performance control.

Structurally Analogous Degradable Version of Fluorene-Bipyridine Copolymer with Exceptional Selectivity for Large-Diameter Semiconducting Carbon Nanotubes

Separation of electronically pure, narrowly dispersed, pristine, semiconducting single-walled carbon nanotubes (CNTs) from a heterogeneous as-synthesized mixture is essential for various semiconducting technologies and biomedical applications. Although conjugated polymer wrappers are often utilized to facilitate electronic-type sorting, it is highly desirable to remove organic residues from the resulting devices. We report here the design and synthesis of a mild acid-degradable π-conjugated polyimine polymer, poly[(9,9-di-n-octyl-2,7-fluoren-dinitrilomethine)-alt-co-(6,6'-{2,2'-bipyridyl-dimethine})] (PFO-N-BPy), that is structurally analogous to the commonly used and commercially available poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-(2,2'-bipyridine))] (PFO-BPy). An acid cleavable imine link (-HC═N-) was introduced in the PFO-N-BPy backbone to impart degradability, which is absent in PFO-BPy. PFO-N-BPy was synthesized via a metal catalyst-free aza-Wittig reaction in high yields. PFO-N-BPy with a degree of polymerization of just ∼10 showed excellent (>99% electronic purity) selectivity for both large-diameter (1.3-1.7 nm) arc-discharge semiconducting CNTs (S-CNTs) and smaller diameter (0.8-1.2 nm) high-pressure carbon monoxide disproportionation reaction S-CNTs. Overall, the selectivity for the semiconducting species is similar to that of PFO-BPy but with an advantage of complete depolymerization under mild acidic conditions into recyclable monomers. We further show by ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy that the PFO-N-BPy-wrapped S-CNTs can be aligned into a monolayer array on gate dielectrics using a floating evaporative self-assembly process from which the polymer can be completely removed. Short channel field effect transistors were fabricated from the polymer-stripped aligned S-CNT arrays, which further confirmed the semiconducting purity on the order of 99.9% or higher.

Directed growth of graphene nanomesh in purified argon via chemical vapor deposition

Graphene nanomeshes (GNMs), new graphene nanostructures with tunable bandgaps, are potential building blocks for future electronic or photonic devices, and energy storage and conversion materials. In previous works, GNMs have been successfully prepared on Cu foils by the H₂ etching effect. In this paper, we investigated the effect of Ar on the preparation of GNMs, and how the mean density and shape of them vary with growth time. In addition, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM) revealed the typical hexagonal structure of GNM. Atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) indicated that large copper oxide nanoparticles produced by oxidization in purified Ar can play an essential catalytic role in preparing GNMs. Then, we exhibited the key reaction details for each growth process and proposed a growth mechanism of GNMs in purified Ar.

Mesoporous metallic rhodium nanoparticles

Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ∼2.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O₂.

Mesoporous noble metal nanostructures offer great promise in catalytic applications. Here, Yamauchi and co-workers synthesize mesoporous rhodium nanoparticles using polymeric micelle templates, and report appreciable activities for methanol oxidation and NO remediation.

Enhanced Thermal Decomposition Properties of CL-20 through Space-Confining in Three-Dimensional Hierarchically Ordered Porous Carbon

High energy and low signature properties are the future trend of solid propellant development. As a new and promising oxidizer, hexanitrohexaazaisowurtzitane (CL-20) is expected to replace the conventional oxidizer ammonium perchlorate to reach above goals. However, the high pressure exponent of CL-20 hinders its application in solid propellants so that the development of effective catalysts to improve the thermal decomposition properties of CL-20 still remains challenging. Here, 3D hierarchically ordered porous carbon (3D HOPC) is presented as a catalyst for the thermal decomposition of CL-20 via synthesizing a series of nanostructured CL-20/HOPC composites. In these nanocomposites, CL-20 is homogeneously space-confined into the 3D HOPC scaffold as nanocrystals 9.2-26.5 nm in diameter. The effect of the pore textural parameters and surface modification of 3D HOPC as well as CL-20 loading amount on the thermal decomposition of CL-20 is discussed. A significant improvement of the thermal decomposition properties of CL-20 is achieved with remarkable decrease in decomposition peak temperature (from 247.0 to 174.8 °C) and activation energy (from 165.5 to 115.3 kJ/mol). The exceptional performance of 3D HOPC could be attributed to its well-connected 3D hierarchically ordered porous structure, high surface area, and the confined CL-20 nanocrystals. This work clearly demonstrates that 3D HOPC is a superior catalyst for CL-20 thermal decomposition and opens new potential for further applications of CL-20 in solid propellants.

Functionalized Natural Carbon-Supported Nanoparticles as Excellent Catalysts for Hydrocarbon Production

We report a one-pot and eco-friendly synthesis of carbon-supported cobalt nanoparticles, achieved by carbonization of waste biomass (rice bran) with a cobalt source. The functionalized biomass provides carbon microspheres as excellent catalyst support, forming a unique interface between hydrophobic and hydrophilic groups. The latter, involving hydroxyl and amino groups, can catch much more active cobalt nanoparticles on surface for Fischer-Tropsch synthesis than chemical carbon. The loading amount of cobalt on the final catalyst is much higher than that prepared with a chemical carbon source, such as glucose. The proposed concept of using a functionalized natural carbon source shows great potential compared with conventional carbon sources, and will be meaningful for other fields concerning carbon support, such as heterogeneous catalysis or electrochemical fields.

Molybdenum Carbide-Derived Chlorine-Doped Ordered Mesoporous Carbon with Few-Layered Graphene Walls for Energy Storage Applications

In this work, we propose a one-step process to realize the in situ evolution of molybdenum carbide (Mo₂C) nanoflakes into ordered mesoporous carbon with few-layered graphene walls (OMG) by chloridization and self-organization, and simultaneously the Cl-doping of OMG (OMG-Cl) by modulating chloridization and annealing processes is fulfilled. Benefiting from the improvement of electroconductivity induced by Cl-doping, together with large specific surface area (1882 cm² g^-1) and homogeneous pore structures, as anode of lithium ion batteries, OMG-Cl shows remarkable charge capacity of 1305 mA h g^-1 at current rate of 50 mA g^-1 and fast charge-discharge rate within dozens of seconds (a charge time of 46 s), as well as retains a charge capacity of 733 mA h g^-1 at a current rate of 0.5 mA g^-1 after 100 cycles. Furthermore, as a promising electrode material for supercapacitors, OMG-Cl holds the specific capacitances of 250 F g^-1 in 1 M H₂SO₄ solution and 220 F g^-1 at a current density of 0.5 A g^-1 in 6 M KOH solution, which are ∼40% and 20% higher than those of undoped OMG electrode, respectively. The high capacitive performance of OMG-Cl material can be due to the additional fast Faradaic reactions induced from Cl-doping species.

New Insight into the Synthesis of Large-Pore Ordered Mesoporous Materials

Ordered mesoporous materials (OMMs) have received increasing interest due to their uniform pore size, high surface area, various compositions and wide applications in energy conversion and storage, biomedicine and environmental remediation, etc. The soft templating synthesis using surfactants or amphiphilic block copolymers is the most efficient method to produce OMMs with tailorable pore structure and surface property. However, due to the limited choice of commercially available soft templates, the common OMMs usually show small pore size and amorphous (or semicrystalline) frameworks. Tailor-made amphiphilic block copolymers with controllable molecular weights and compositions have recently emerged as alternative soft templates for synthesis of new OMMs with many unique features including adjustable mesostructures and framework compositions, ultralarge pores, thick pore walls, high thermal stability and crystalline frameworks. In this Perspective, recent progresses and some new insights into the coassembly process about the synthesis of OMMs based on these tailor-made copolymers as templates are summarized, and typical newly developed synthesis methods and strategies are discussed in depth, including solvent evaporation induced aggregation, ligand-assisted coassembly, solvent evaporation induced micelle fusion-aggregation assembly, homopolymer assisted pore expanding and carbon-supported crystallization strategy. Then, the applications of the obtained large-pore OMMs in catalysis, sensor, energy conversion and storage, and biomedicine by loading large-size guest molecules (e.g., protein and RNA), precious metal nanoparticles and quantum dots, are discussed. At last, the outlook on the prospects and challenges of future research about the synthesis of large-pore OMMs by using tailor-made amphiphilic block copolymers are included.

Aptamer-anchored di-polymer shell-capped mesoporous carbon as a drug carrier for bi-trigger targeted drug delivery

Mesoporous carbon nanomaterials have found applications in drug delivery and cancer therapy.