Jianwei Fan

Radially oriented mesoporous TiO2 microspheres with single-crystal–like anatase walls for high-efficiency optoelectronic devices

Uniform mesoporous single-crystal TiO2 spheres with radial channels from driving orientation assembly can be used for energy storage. Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m2/g), a large pore volume (0.164 cm3/g), and highly single-crystal–like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.

Rapid and Efficient Removal of Microcystins by Ordered Mesoporous Silica

To alleviate the environmental and health threats from water resources polluted by large-sized microcystins (MCs), we demonstrate for the first time that ordered mesoporous silica materials with large pore sizes of 2-12 nm can be used as adsorbents for rapid and efficient removal of MCs. The obvious correlations between adsorption performance of MCs and physicochemical properties of adsorbents including pore mesostructure, texture and size, and surface chemistry have been well established. Accordingly, an excellent candidate, mesoporous silica SBA-15 templated from Pluronic P123 has been sorted out, exhibiting extremely rapid rate (one minute) as well as high capacities of 5.99 and 13 mg g(-1) for removing high-concentration MC-LR and MC-RR, respectively, which are much higher than that of other silica-based adsorbents reported previously. The adsorption performance can be further improved from 50 to 95% at around pH 4 by grafting positively charged and/or hydrophobic groups onto pore surface of SBA-15. Furthermore, thermodynamic and kinetic evaluations provide additional valuable information for a better understanding of the adsorption process. Given the excellent adsorption performance, it is expected that mesoporous silica materials with unique characteristics are attractive for actual applications in removal of MCs from wastewater.

Ordered mesoporous carbons and their corresponding column for highly efficient removal of microcystin-LR

Highly effective removal of toxic pollutant microcystins from water sources is achieved by employing ordered mesoporous carbons prepared from the surfactant-templating method as adsorbents. For the first time, a systematic study into the static and dynamic adsorption behaviours of ordered mesoporous carbons towards microcystin-LR (MC-LR) is demonstrated. Firstly, by adopting different mesoporous carbons with various mesostructures, textures and surface chemical properties for batch adsorption, definite relationships between the adsorption performance of MC-LR and properties of adsorbents are established. Among all the samples, the mesoporous carbon (MCS/C) obtained from a mesoporous silica–carbon composite after removing the silica component exhibits an unprecedented adsorption capacity of ∼526 mg g−1, due to its unique bimodal mesopores of ∼2.8 and 5.8 nm, a high surface area of 1680 m2 g−1, a large pore volume of 1.67 cm3 g−1 and two-dimensional (2D) straight mesopore channels. A comprehensive understanding of dynamic adsorption behaviour shows that this mesoporous carbon possesses a 30-fold higher adsorption capacity compared with powdery activated carbon at a high flux of 120 L m−2 h−1. Finally, two pollutants, Rhodamine B and phenol, are mixed with MC-LR for competitive adsorption onto the mesoporous carbon MCS/C. It is found that the total amount of removal pollutants increases sharply to ∼700 mg g−1. Considering all the advantages, the ordered mesoporous carbon MCS/C shows a promising potential for practical waste water treatment, especially for large toxin microcystin removal.

Ordered Macro/Mesoporous TiO2 Hollow Microspheres with Highly Crystalline Thin Shells for High-Efficiency Photoconversion

Well ordered, uniform 3D open macro/mesoporous TiO2 hollow microspheres with highly crystalline anatase thin shells have been successfully synthesized by a simple solvent evaporation-driven confined self-assembly method. The 3D open macro/mesoporous TiO2 hollow microspheres show high energy-conversion efficiency (up to 9.5%) and remarkable photocatalytic activity (with photodegradation of 100% for methylene blue in 12 min under UV light irradiation).

Monodisperse core-shell structured magnetic mesoporous aluminosilicate nanospheres with large dendritic mesochannels

The rational design and precise synthesis of multifunctional hybrid nanostructures with a tailored active core and a large, dendritic, modified mesoporous structured shell can promote catalysis, energy storage, and biological applications. Here, an oil-water biphase stratification coating strategy has been developed to prepare monodisperse magnetic dendritic mesoporous silica core-shell structured nanospheres. These sophisticated Fe3O4@SiO2@dendritic-mSiO2 nanospheres feature large dendritic open pores (2.7 and 10.3 nm). Significantly, the silica shells can be converted into dendritic mesoporous aluminosilicate frameworks with unchanged porosity, a Si/Al molar ratio of 14, and remarkably strong acidic sites, through a post-synthesis approach. In addition, the resultant magnetic dendritic mesoporous aluminosilicate nanospheres exhibit outstanding properties and promising application in phosphate removal from wastewater.

Mesoporous Silica-Coated Plasmonic Nanostructures for Surface-Enhanced Raman Scattering Detection and Photothermal Therapy

The design and fabrication of core-shell and yolk-shell nanostructures with surface plasmon resonance (SPR)-active center protected by permeable mesoporous channels can raise the new vitality into the catalysis and biological applications. Hybrid plasmonic-mesoporous silica nanocarriers consisting of Ag and Au-Ag alloy nanoparticles are fabricated through spatially confined galvanic replacement approach. The plasmonic absorption peaks can be finely controlled to the near-infrared (NIR) region (500-790 nm) that is beneficial for tissue transmittance. The mesoporous silica shell facilitates also protection of Au-Ag cores and affords the channels between the exterior and interior capsule environments, thereby endowing the multiple applications. In the present work, it is successfully demonstrated that mesoporous silica-coated Au-Ag alloy core-shell and yolk-shell nanocarriers can serve as good substrates for surface-enhanced Raman scattering (SERS) detection. The SERS signal intensities of nanocarriers are highly dependent on the SPR peaks and the contents of gold. Simultaneously, the synthesized Au-Ag@mSiO2 nanocarriers with SPR peak at ≈790 nm can be applied in NIR-sensitive SERS detection and photothermal therapy.

Mesoporous TiO2 Mesocrystals: Remarkable Defects-Induced Crystallite-Interface Reactivity and Their in Situ Conversion to Single Crystals.

Oriented self-assembly between inorganic nanocrystals and surfactants is emerging as a route for obtaining new mesocrystalline semiconductors. However, the actual synthesis of mesoporous semiconductor mesocrystals with abundant surface sites is extremely difficult, and the corresponding new physical and chemical properties arising from such an intrinsic porous mesocrystalline nature, which is of fundamental importance for designing high-efficiency nanostructured devices, have been rarely explored and poorly understood. Herein, we report a simple evaporation-driven oriented assembly method to grow unprecedented olive-shaped mesoporous TiO2 mesocrystals (FDU-19) self-organized by ultrathin flake-like anatase nanocrystals (∼8 nm in thickness). The mesoporous mesocrystals FDU-19 exhibit an ultrahigh surface area (∼189 m2/g), large internal pore volume (0.56 cm3/g), and abundant defects (oxygen vacancies or unsaturated Ti3+ sites), inducing remarkable crystallite-interface reactivity. It is found that the mesocrystals FDU-19 can be easily fused in situ into mesoporous anatase single crystals (SC-FDU-19) by annealing in air. More significantly, by annealing in a vacuum (∼4.0 × 10–5 Pa), the mesocrystals experience an abrupt three-dimensional to two-dimensional structural transformation to form ultrathin anatase single-crystal nanosheets (NS-FDU-19, ∼8 nm in thickness) dominated by nearly 90% exposed reactive (001) facets. The balance between attraction and electrostatic repulsion is proposed to determine the resulting geometry and dimensionality. Dye-sensitized solar cells based on FDU-19 and SC-FDU-19 samples show ultrahigh photoconversion efficiencies of up to 11.6% and 11.3%, respectively, which are largely attributed to their intrinsic single-crystal nature as well as high porosity. This work gives new understanding of physical and chemical properties of mesoporous semiconductor mesocrystals and opens up a new pathway for designing various single-crystal semiconductors with desired mesostructures for applications in catalysis, sensors, drug delivery, optical devices, etc.

One-pot synthesis of Aluminum-containing ordered mesoporous silica MCM-41 using coal fly ash for phosphate adsorption

The present study offers an economic one-pot synthesis of Al-containing ordered mesoporous silica MCM-41 from the coal fly ash. The samples were characterized by small-angle XRD, N2 adsorption, TEM, mapping, (27)Al MAS NMR, EDX, and NH3-TPD. The effects of pH values to the final mesostructures have also been investigated. The results show that the material prepared at the pH value of 10 displays the largest pore volume of 0.98 cm(3)/g, the highest BET surface area of 1020 m(2)/g, and the lowest Si/Al molar ratio of 2. Using this material as adsorbent for phosphates, the adsorption capacity reaches 64.2mg/g at 298 K, which is much higher than that of large pore mesoporous silica SBA-15 (53.5mg/g), diatomite (62.7 mg/g), and MCM-41 (31.1 mg/g). In addition, the thermodynamics and kinetics for the phosphate adsorption were also investigated. Our present study shows an economic way to treat phosphates using the industrial solid waste of coal fly ash.

Facile preparation of Cu–Mn/CeO2/SBA-15 catalysts using ceria as an auxiliary for advanced oxidation processes

A facile synthetic method was adopted to prepare heterogeneous catalysts using ordered mesoporous silica SBA-15 as matrix, ceria as auxiliary and Cu–Mn as the catalytic active sites, denoted as Cu–Mn/CeO2/SBA-15. Characterization results demonstrate that the metal oxide nanoparticles are well-dispersed inside the mesopores rather than aggregated outside the surface. The particle sizes range from 4.1 to 11.2 nm with an increase in calcination temperature from 300 to 500 °C. The presence of ceria plays a significant role in the formation of well-dispersed metal oxide nanoparticles, and a possible mechanism for the preparation of this heterogeneous catalyst is proposed based on comparable experimental results. Catalytic degradation studies for advanced oxidation processes (AOPs) show that Cu–Mn/CeO2/SBA-15 catalysts can efficiently degrade (>99%) high-concentration dye pollutants (C = 2 g L−1) within 210 min at 70 °C and can retain a good degradation efficiency even at a pH value of 7 when using Rhodamine B as the model pollutant. The excellent AOP catalytic performance could be ascribed to the well-dispersed catalytic nanoparticles inside the mesopores and the catalytic synergic effect of CeO2. Our work here displays a simple method to synthesize heterogeneous catalyst with well-dispersed nano-sized catalytic active sites for AOPs by using CeO2 as the auxiliary agent.

Ordered mesoporous silica/polyvinylidene fluoride composite membranes for effective removal of water contaminants

A facile one-step immersion co-precipitation method has been developed to fabricate an inorganic–organic composite membrane with three-dimensionally (3D) interpenetrating porous structures via incorporating ordered mesoporous silica (OMS) into polyvinylidene fluoride (PVDF). The composite membranes possess high surface area, excellent hydrophilicity and ultrahigh water fluxing capability (224.5 L m−2 h−1). It shows an excellent dynamic adsorption capacity (14.5 mg g−1) for methylene blue, which is ∼9.7 times higher than that of the pure PVDF membranes. Moreover, the composite membrane containing amino-functionalized OMS exhibits good adsorption capacity (1.5 mg g−1) for Cu(II) ions, thanks to the numerous amino groups in the mesopore walls. Importantly, the composite membranes can be easily regenerated, retaining their adsorption performance. Our findings open up the possibility for the mass fabrication of functional porous membranes for continuous and scalable water treatment.