Maillard Reaction Inspired Microexplosion toward Fast Synthesis of Two-Dimensional Mesoporous Tin Oxides for Efficient Chemiresistive Gas Sensing.

Two-dimensional (2D) mesoporous transition metal oxides are highly desired in various applications, but their fast and low-cost synthesis remains a great challenge. Herein, a Maillard reaction inspired microexplosion approach is applied to rapidly synthesize ultrathin 2D mesoporous tin oxide (mSnO2). During the microexplosion between granular ammonia nitrate with melanoidin at high temperature, the organic species can be carbonized and expanded rapidly due to the instantaneous release of gases, thus producing ultrathin carbonaceous templates with rich functional groups to effectively anchor SnO2 nanoparticles on the surface. The subsequent removal of carbonaceous templates via calcination in air results in the formation of 2D mSnO2 due to the confinement effect of the templates. Pd nanoparticles are controllably deposited on the surface of 2D mSnO2 via in situ reduction, forming ultrathin 2D Pd/mSnO2 nanocomposites with thicknesses of 6-8 nm. Owing to the unique 2D mesoporous structure with rich oxygen defects and highly exposed metal-metal oxide interfaces, 2D Pd/mSnO2 exhibits excellent sensing performance toward acetone with high sensitivity, a short response time, and good selectivity under low working temperature (100 °C). This fast and convenient microexplosion synthesis strategy opens up the possibility of constructing 2D porous functional materials for various applications including high-performance gas sensors.

A Versatile Synthesis Platform Based on Polymer Cubosomes for a Library of Highly Ordered Nanoporous Metal Oxides Particles.

Polymer cubosomes (PCs) have well-defined inverse bicontinuous cubic mesophases formed by amphiphilic block copolymer bilayers. The open hydrophilic channels, large periods, and robust physical properties of PCs are advantageous to many host-guest interactions and yet not fully exploited, especially in the fields of functional nanomaterials. Here, the self-assembly of poly(ethylene oxide)-block-polystyrene block copolymers is systematically investigated and a series of robust PCs is developed via a cosolvent method. Ordered nanoporous metal oxide particles are obtained by selectively filling the hydrophilic channels of PCs via an impregnation strategy, followed by a two-step thermal treatment. Based on this versatile PC platform, the general synthesis of a library of ordered porous particles with different pore structures 3 ¯ $\bar{3}$ 3 ¯ $\bar{3}$ , tunable large pore size (18-78 nm), high specific surface areas (up to 123.3 m2 g-1 for WO3) and diverse framework compositions, such as transition and non-transition metal oxides, rare earth chloride oxides, perovskite, pyrochlore, and high-entropy metal oxides is demonstrated. As typical materials obtained via this method, ordered porous WO3 particles have the advantages of open continuous structure and semiconducting properties, thus showing superior gas sensing performances toward hydrogen sulfide.

Solvent-pair surfactants enabled assembly of clusters and copolymers towards programmed mesoporous metal oxides.

Organic-inorganic molecular assembly has led to numerous nano/mesostructured materials with fantastic properties, but it is dependent on and limited to the direct interaction between host organic structure-directing molecules and guest inorganic species. Here, we report a "solvent-pair surfactants" enabled assembly (SPEA) method to achieve a general synthesis of mesostructured materials requiring no direct host-guest interaction. Taking the synthesis of mesoporous metal oxides as an example, the dimethylformamide/water solvent pairs behave as surfactants and induce the formation of mesostructured polyoxometalates/copolymers nanocomposites, which can be converted into metal oxides. This SPEA method enables the synthesis of functional ordered mesoporous metal oxides with different pore sizes, structures, compositions and tailored pore-wall microenvironments that are difficult to access via conventional direct organic-inorganic assembly. Typically, nitrogen-doped mesoporous ε-WO3 with high specific surface area, uniform mesopores and stable framework is obtained and exhibits great application potentials such as gas sensing.

Solution-Liquid-Solid Growth and Catalytic Applications of Silica Nanorod Arrays.

As an analogue to the vapor-liquid-solid process, the solution-liquid-solid (SLS) method offers a mild solution-phase route to colloidal 1D nanostructures with controlled sizes, compositions, and properties. However, direct growth of 1D nanostructure arrays through SLS processes remains in its infancy. Herein, this study shows that SLS processes are also suitable for the growth of nanorod arrays on the substrate. As a proof of concept, seedless growth of silica nanorod arrays on a variety of hydrophilic substrates such as pristine and oxide-modified glass, metal sheets, Si wafers, and biaxially oriented polypropylene film are demonstrated. Also, the silica nanorod arrays can be used as a new platform for the fabrication of catalysts for photothermal CO2 hydrogenation and the reduction of 4-nitrophenol reactions. This work offers some fundamental insight into the SLS growth process and opens a new avenue for the mild preparation of functional 1D nanostructure arrays for various applications.