Evaporation-induced Self-assembly Route Research Articles

Self-Assembly of Chiral Nematic-Like Films with Chiral Nanorods Directed by Chiral Molecules

Chiral superstructures are ubiquitous in nature and display intriguing and elegant performances, which inspired us to realize multiscale chiral mesostructured inorganics. Here, we report cholic acid-induced anisotropic epitaxial growth of chiral CdSe/CdS nanorods (CCCNs) and their self-assembly into chiral nematic-like films (CNFs) via an evaporation-induced self-assembly route. Three levels of chirality exist in the CNFs assembled with CCCNs: a primary chiral distortion of the nanorod, a secondary chiral nematic-like phase in which layered nanobelts are stacked to form with a side-by-side arrangement of the CCCNs, and tertiary helical planks with stacking of the layered chiral nematic-like phase creating a banded spherulite structure. The CNFs exhibited excitonic absorption- and scattering-based optical activities and circularly polarized luminescence due to their hierarchical chirality.

Highly Ordered Hierarchically Macroporous MIL-125 with High Specific Surface Area for Photocatalytic CO2 Fixation

Highly ordered hierarchical macroporous metal–organic framework (MOF) materials (macroporous MIL-125) have been successfully synthesized through a solvent evaporation-induced self-assembly route in...

Impact of Fe deposition on microwave absorption properties of ordered mesoporous carbon flakes

Lightweight ordered mesoporous carbon (OMC) flakes have been successfully synthesized by an evaporation-induced self-assembly route. The highest specific surface area and pore volume of the OMC flakes reach 1727 m2 g−1 and 2.05 cm3 g−1, respectively. The results of the complex permittivity show the OMC/paraffin composites have high dielectric loss in the frequency range of 2–18 GHz. In order to enhance the microwave absorption properties of the OMC materials, an electroless plating method is exploited to deposit Fe particles on the OMC flakes. Benefiting from the magnetic loss and improved impedance characteristic, the OMC/Fe composites display excellent microwave absorption properties. The minimum reflection loss of the OMC-700-Fe composite reaches − 65.3 dB at 10.1 GHz and the absorption bandwidth < − 10 dB is up to 4.7 GHz (8.7–12.4 GHz) with the absorbing thickness of 2.5 mm. When the thickness is from 1.8 to 5.5 mm, all of the peak values of reflection loss are < − 20 dB. This work provides a new opportunity for the fabrication and design of lightweight microwave absorbers.

Low-cost fabrication of highly sensitive room temperature hydrogen sensor based on ordered mesoporous Co-doped TiO2 structure

The development of cost-effective gas sensors with improved sensing properties and minimum power consumption for room temperature hydrogen leakage monitoring is in increasing demand. In this context, this report focus on the facile fabrication of ordered mesoporous TiO2 via evaporation-induced self-assembly route. With the controlled doping threshold (3%Co-TiO2), the output resistance change to 1000 ppm H2 is ∼4.1 × 103 with the response time of 66 s. The sensor response exhibits power law dependence with an increase in the hydrogen concentration, where the power law coefficient was found not only specific to the kind of target gas but also related to temperature. Further, the effect of structure integrity with doping level and humidity on sensing characteristics is interpreted in terms of variation in surface potential eVS and depletion region w caused by the adsorption of molecular oxygen O2−.

Nitrogen-doped MoS2/carbon as highly oxygen-permeable and stable catalysts for oxygen reduction reaction in microbial fuel cells

Abstract Developing non-noble metal catalysts with high oxygen-permeability and activity for oxygen reduction reaction (ORR) is crucial for microbial fuel cells (MFCs). In this study, nitrogen-doped molybdenum disulfide/carbon (N-MoS2/C) is prepared using melamine as nitrogen and carbon sources. Ammonium molybdate, thiourea and Pluronic F127 are used as Mo source, S source and surfactant, respectively. Mo-S-melamine complex precursor is obtained through the evaporation-induced self-assembly route, which is then carbonized at 800, 900 and 1000 °C to fabricate N-MoS2/C. Defect-rich N-MoS2/C has a large number of exposed active sites and a high oxygen permeability. N-MoS2/C (900 °C) with regular honeycomb structure shows the maximum power density of 0.815 W m-2, which is far higher than that of Pt/C (0.520 W m-2) and only has a decline of 1.23% after 1800 h operation in MFCs. Four-electron (4e−) reduction of O2 is the main ORR pathway for N-MoS2/C (900 °C), attributing to the efficient permeation, adsorption, activation and reduction of O2 on the active sites. The synergy among abundant defects, N-species (pyridinic N, graphitic N and Mo−Nx) and high conductivity contributes to the promising ORR activity. This simple synthetic route of N-doped metal sulfides/carbon composites displays a new prospect for preparation of ORR catalyst.

A pure aqueous route to mesoporous silica thin films via dip-coating of prefabricated hybrid micelles

Mesoporous thin films were prepared by dip-coating with a purely aqueous method, as a substitute for the alcohol-based evaporation-induced self-assembly route. Unlike other aqueous routes that require a very slow pulling rate possible only using high performance dip-coaters, as a result of the high surface tension of water, this new process works with standard dip-coaters and at similar pulling rates as are used for the evaporation-induced self-assembly route. This unique asset is the result of the synthesis of prefabricated self-assembled silicate/organic hybrid micelles. These building blocks are concentrated before use, which provides a gelling edge after moderate evaporation. As a result, defect-free continuous mesoporous films with well-organized hexagonally packed pores were prepared after optimization of both the evaporation rate of the solution of hybrid micelles and the dip-coater pulling rate. The transmission electron microscopy observation reveals the hexagonally packed structure of mesoporous silica film. This nanostructure has already been observed on films prepared with the evaporation-induced self-assembly process, but it is the first time it is obtained with a pure aqueous method, based on prefabricated hybrid micelles, not on controlled evaporation of mesophases.

TiO2/carbon paper composite materials with hierarchically porous structure for photocatalysis

TiO2/carbon paper composite materials with a hierarchically porous structure were synthesized by employing a filter paper as the support material and carbon source. The resorcinol–formaldehyde–block copolymer nanocomposite formed by the self-assembly of phenolic resin and F127 under acidic condition was selected as modifier of the microstructure of carbon paper. Results show that the as-adjusted carbon paper preserved the nanostructure of a pure carbonized filter paper. An ordered mesostructure was also formed. This micromorphology resulted in the increased specific surface area, as well as micropore and mesopore volumes, compared with the pure carbonized filter paper. When mesoporous TiO2 was deposited on the carbon paper with ordered mesopore by the evaporation-induced self-assembly route, the TiO2/carbon paper composite materials displayed excellent adsorption property and enhanced photocatalytic activity of methylene blue.

Synergetic effect of VOx and TeOx species in mesoporous SiO2 on selective oxidation of propane to acrolein

A mesoporous silica with incorporated vanadium (V) and tellurium (Te) (3%VTezOx-MS; z=0–0.33), synthesized by an evaporation-induced self-assembly route, was used as a model catalyst to investigate the synergetic effect of VOx and TeOx species on propane oxidation to acrolein. It was found that V in the catalyst was predominantly present as a highly dispersed VO4 species, while Te existed as a highly dispersed TeOx species when the Te/V atomic ratio was below 0.2. Acrolein formation rate was positively correlated with TeOx content when both VOx and TeOx in the catalysts were in a highly dispersed state. Study of the propane oxidation pathways further indicated that highly dispersed VO4 in close contact with highly dispersed TeOx constituted the active sites for direct oxidation of propane to acrolein. These binary sites satisfied all the required functions for the reactions, including consecutive sequence of activation of propane and propylene intermediate followed by inserting oxygen into the as-formed allylic species.

Synthesis, characterization, and catalytic performance of copper-containing SBA-15 in the phenol hydroxylation

A series of copper-containing SBA-15 samples were successfully synthesized via evaporation-induced self-assembly route. The resulting materials were characterized by X-ray diffraction (XRD), 29Si MAS NMR spectroscopy, transmission electron microscopy (TEM), N2 sorption, inductively coupling plasma-atomic emission spectrometer (ICP-AES), thermogravimetry, and differential thermal analysis (TG–DTA), Fourier-transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectra (UV–vis) and X-ray photoelectron spectroscopy (XPS). The results indicated that: (1) all the samples exhibited typical hexagonal arrangement of mesoporous structure; (2) copper ions could be incorporated into the framework of SBA-15; (3) the addition of urea in the hydrothermal stage efficiently reduced the leaching of copper and improved the thermal stability of the mesoporous materials. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H2O2. The catalytic tests showed that the synthesized materials exhibited high activity for this reaction and copper ions in the framework were more active than copper species in the extra-framework position. The nitric acid treatment on the samples removed the bulk CuO species, which resulted in a dramatic increase in the catalytic activity.

Grating induced micelle alignment of mesostructured silica films

A two-dimensional hexagonal film was produced by the evaporation-induced self-assembly route using the triblock copolymer (EO20PO70EO20) as the structure directing agent. The film was deposited between the walls of a grating of 450nm period and 55nm average line depths by dip coating the substrate in the direction perpendicular to the lines of the grating. In the case where film thicknesses were less than the height of grating walls, the orientation of the micelles was directed by the walls of the grating. Observation of the mesostructured film using atomic force microscopy after chemical etching revealed the internal structure.