Large-pore ordered mesoporous materials templated from non-Pluronic amphiphilic block copolymers

The self-assembly of small surfactants and Pluronic® amphiphilic copolymers has enabled the synthesis of a range of ordered mesoporous materials with high surface area, diverse compositions, variable pore structures and tunable pore sizes. It has recently been realized that non-Pluronic block copolymers can be used as robust templates for the synthesis of novel and high-performance mesoporous materials with crystalline frameworks, ultra-large pores, and abundant pore symmetries, which are not accessible using the Pluronic counterparts. In this review, we introduce the principle of self-assembly of block copolymers and their phase separations, and summarize recently developed synthetic methods and strategies for ordered mesoporous silicas, metal oxides, carbons and metals which have shown superior performances for applications in various fields, including solar cells, batteries, fuel cells, and sensors.

Highly ordered cubic mesoporous materials with the same symmetry but tunable pore structures

In this article, two highly ordered mesoporous silica materials with the same face-centered cubic (fcc) symmetry but distinctly different pore structures have been synthesized by simply changing the amount of silica source. Their structures have been extensively studied by Synchrotron small-angle X-ray scattering, N(2) sorption analysis, scanning and transmission electron microscopy observations, and electron tomography. One mesoporous material formed by a hard sphere packing (HSP) pathway exhibits a bimodal pore distribution, while the other has a conventional FDU-12-type mesostructure with a single-sized pore. By increasing the amount of the silica source, the cavities formed by the packing of composite spherical micelles in the HSP mesostructure are gradually filled by the excess of siliceous species, leading to the conventional FDU-12-type mesostructure with the disappearance of bimodal pores. The pore connectivity of the HSP mesoporous material hydrothermally treated at 150 °C has been further investigated. Taking advantage of the ultrathin tomographic slices, the sizes of cage, cavity, and connectivity are measured to be 14.5, 10.5, and 6.4 nm, respectively. More importantly, the pore connection between the cage and cavity is directly observed to occur along the ⟨100⟩ direction, different from the FDU-12-type mesostructure in which the connection appears between two adjacent cages along the ⟨110⟩ direction. This work represents an unusual example where two ordered cage-type mesoporous materials with the same symmetry can be synthesized by slightly changing the synthesis condition, but their pore structures and pore connections are significantly different. Our finding is important for understanding the formation mechanism and for the rational design and controllable synthesis of novel mesoporous materials.

The use of PEEK nanorod arrays for the fabrication of nanoporous surfaces under high temperature: SiNx example

Large area silicon nitride (SiN(x)) nanoporous surfaces are fabricated using poly(ether-ether-ketone) (PEEK) nanorod arrays as a template. The procedure involves manipulation of nanoporous anodic aluminum oxide (AAO) templates in order to form an ordered array of PEEK nanopillars with high temperature resistant characteristics. In this context, self-ordered AAO templates are infiltrated with PEEK melts via the "precursor film" method. Once the melts have been crystallized in the porous structure of AAO, the basis alumina layer is removed, yielding an ordered array of PEEK nanopillars. The resulting structure is a high temperature and chemical resistant polymeric nanomold, which can be utilized in the synthesis of nanoporous materials under aggressive conditions. Such conditions are high temperatures (up to 320 °C), vacuum, or extreme pH. For example, SiN(x) nanopore arrays have been grown by plasma enhanced chemical vapor deposition at 300 °C, which can be of interest as mold for nanoimprint lithography, due to its hardness and low surface energy. The SiN(x) nanopore array portrays the same characteristics as the original AAO template: 120 nm diameter pores and an interpore distance of 430 nm. Furthermore, the aspect ratio of the SiN(x) nanopores can be tuned by selecting an AAO template with appropriate conditions. The use of PEEK as a nanotemplate extends the applicability of polymeric nanopatterns into a temperature regime up to now not accessible and opens up the simple fabrication of novel nanoporous inorganic surfaces.

Synthesis, properties and applications of nanoscale nitrides, borides and carbides

Nanoscale nitrides, borides and carbides are a fascinating type of materials, which have aroused tremendous and continuous research interest for decades owing to their special mechanical, electrical, optical, photoelectronic, catalytic properties and widespread uses. In this feature article, recent developments and breakthroughs in the synthesis, properties and applications of nanometre scale nitrides (BN, Si(3)N(4), GaN, noble nitrides), borides (LnB(6), LnB(2), Fe(3)BO(5), LiMBO(3)) and carbides (carbon, SiC, TiC, NbC, WC) were briefly reviewed in sequence of their different dimensions (1D, 2D and 3D). In particular, our latest advances in the "autoclave route" fabrication of nanoscale nitrides, borides, and carbides were highlighted. The challenges, issues and perspectives of the synthetic methodologies and potential applications concerning the above-mentioned materials were also briefly discussed.

Polymer/Ordered mesoporous carbon nanocomposite platelets as superior sensing materials for gas detection with surface acoustic wave devices

We have prepared nanocomposites of polymers and platelet CMK-5-like carbon and have demonstrated their superior performance for gravimetric gas detection. The zirconium-containing platelet SBA-15 was used as hard template to prepare CMK-5-like carbon, which was then applied as a lightweight and high-surface-area scaffold for the growth of polymers by radical polymerization. Mesoporous nanocomposites composed of four different polymers were used as sensing materials for surface acoustic wave devices to detect ppm-level ammonia gas. The sensors showed much better sensitivity and reversibility than those coated with dense polymer films, and the sensor array could still generate a characteristic pattern for the analyte with a concentration of 16 ppm. The results show that the nanocomposite sensing materials are promising for highly sensitive gravimetric-type electronic nose applications.

Tailored design of architecturally controlled Pt nanoparticles with huge surface areas toward superior unsupported Pt electrocatalysts

Herein, we report a very simple and rapid method to synthesize two types of Pt nanoparticles with open porous structures (i.e., Pt nanodendrites and multiarmed Pt nanostars) in high yield. The present synthesis is performed by a simple sonication treatment of an aqueous solution containing K2PtCl4 and a nonionic block copolymer with branched alkyl chains in the presence of ascorbic acid (AA) at room temperature. Nanodendrites and multiarmed nanostars with different Pt nanostructures are selectively synthesized by simply controlling the dissolved block copolymer amounts in the reactive system. As-prepared 3D Pt nanodendrites and multiarmed Pt nanostars with well-defined morphologies are highly porous and self-supported structures assembled by staggered nanoarms as building blocks, thereby realizing extremely high surface areas (around 80 m(2) g(-1)). The present synthesis has a remarkable advantage in its simplicity for the synthesis of Pt nanocatalysts, in comparison with other previous approaches. Our Pt nanodendrites and Pt nanostars not only improve the active Pt surface area but also show superior electrochemical performance, which make them promising electrocatalysts for future.

Ordered mesoporous metal oxides: synthesis and applications

Great progress has been made in the preparation and application of ordered mesoporous metal oxides during the past decade. However, the applications of these novel and interesting materials have not been reviewed comprehensively in the literature. In the current review we first describe different methods for the preparation of ordered mesoporous metal oxides; we then review their applications in energy conversion and storage, catalysis, sensing, adsorption and separation. The correlations between the textural properties of ordered mesoporous metal oxides and their specific performance are highlighted in different examples, including the rate of Li intercalation, sensing, and the magnetic properties. These results demonstrate that the mesoporosity has a direct impact on the properties and potential applications of such materials. Although the scope of the current review is limited to ordered mesoporous metal oxides, we believe that the information may be useful for those working in a number of fields.

Synthesis of nitrogen-rich mesoporous carbon nitride with tunable pores, band gaps and nitrogen content from a single aminoguanidine precursor

Highly ordered mesoporous carbon nitride (CN) with an extremely high nitrogen content and tunable pore diameters was synthesized by using a new precursor with a high nitrogen content, aminoguanidine hydrochloride and mesoporous silica SBA-15 with different pore diameters as hard templates. Surprisingly, the N/C ratio of the prepared mesoporous CN (MCN-4: 1.80) was considerably higher than that of the theoretically predicted C(3)N(4) nanostructures (1.33). This is mainly due to the fact that the CN precursor easily undergoes polymerization at high temperature and affords a highly stable polymer composed of a diamino-s-tetrazine moiety with a six-membered aromatic ring containing six nitrogen atoms that are linked trigonally with the nitrogen atoms. The obtained materials were thoroughly characterized by means of XRD, nitrogen adsorption, high resolution TEM, electron energy loss spectra, high resolution SEM, X-ray photoelectron spectroscopy, FTIR, and C, N, O, and S analysis. The results show that the MCN-4 materials possess a well-ordered mesoporous structure similar to SBA-15 with a high specific surface area and tunable band gap in the range of 2.25-2.49 eV. Interestingly, the pore diameter of the materials can be finely tuned from 3.1-5.8 nm by increasing the pore diameter of the hard-template SBA-15. The reaction temperature plays a critical role for the formation of MCN, and we found that 400 °C is the best condition to obtain MCN-4 with a high nitrogen content. We have further investigated the catalytic application of the MCN-4 materials towards Friedel-Crafts hexanoylation of benzene and compared the results with the mesoporous CN with less nitrogen content (MCN-1) and nonporous CN. Among the materials studied, MCN-4 showed the highest activity, affording a high yield of hexanophenone within a few hours, which is mainly due to the presence of free amine groups on the wall structure of MCN-4.