Large area polystyrene (PS)/WO3 opal composite monolayers were successfully fabricated via a modified “dynamic-hard-template” infiltration strategy. These composite monolayers were then used as building blocks for the synthesis of three-dimensional (3D) WO3 inverse opal (IO) films in a bottom-up approach. To achieve this, a PS/WO3 opal composite monolayer serves as a support upon which another PS/WO3 opal composite monolayer is added, and so on, one over the other, rendering possible, after removal of the PS spheres template, the fabrication of large area 3D WO3 IO films. Similarly, bilayer, and trilayer WO3 IOs with large area, having the same pore sizes from layer to layer, can be obtained by repeatedly applying this strategy. This approach also allows control over hierarchical porosity and film thickness by simply changing the diameter of the sacrificial colloidal template and/or the inorganic precursor used in each layer. 3D WO3 IO films fabricated with this technique exhibit good electrochemical reversibility, cycling stability, and increased coloration efficiency (CE) as the number of WO3 IO layers is increased.

A hierarchical meso-/microporous aluminosilicate has been synthesized through kinetic control over the competition balance between mesoporous self-assembly and microporous zeolite crystallization by using hexadecyl trimethyl ammonium bromide (CTAB) and tetrabutylammonium hydroxide (TBAOH) as meso- and micro-porogens, respectively. A very small pH value range of 11.10–11.30, which can be well tuned by added ethanol volume fraction and/or NaOH addition, was found to be suitable for the formation of mesoporous zeolite without phase separation. Balanced inorganic species adsorptions onto the meso- and microtemplates, and the subsequent electrostatic interaction between such adsorption-formed meso- and micro-colloids are discussed and proposed to be the two key underlined mechanisms in the successful synthesis. The material shows perfect crystallization of zeolite frameworks and relatively high surface area and meso-/micropore volumes. The prepared mesoporous zeolite showed much higher catalytic activity in the reaction between lauric acid and ethanol than those when using both amorphous mesoporous materials and conventional ZSM-5 zeolite as catalysts.Graphical abstractA pH value range of 11.10–11.30 was found to be suitable for the formation of mesoporous zeolite without phase separation. Balanced inorganic species adsorptions onto the meso- and microtemplates, and the subsequent electrostatic interaction between such adsorption-formed meso- and micro-colloids are discussed and proposed to be the two key underlined mechanisms in the successful synthesis.Highlights► A mesoporous zeolite has been synthesized. ► The competition balance between mesoporous and zeolite phases was the key. ► A narrow pH value range of 11.10–11.30 was suitable for the synthesis. ► The material shows perfect crystallization of zeolite and high surface area. ► The mesoporous zeolite showed excellent catalytic activity.

Nickel ferrite nanoparticles were prepared by a hydrothermal method. The effects of synthetic conditions on particle sizes and magnetic properties were investigated by TEM, XRD, and VSM. The results show that the concentrations of metal ions were the key factors not only on the particle size of NiFe2O4 but also on their magnetic properties. The pH value influenced greatly the magnetic properties through the reacted impurities. Once the reactions were given high enough temperature and long enough time, the particles would reach their ‘mature’ size and relative stable magnetic properties due to more perfect structure and more relaxed structural stress, therefore they showed much lower Hc and higher Ms than that of “immatured” particles. During the growing period of the particles, however, the temperature and the time play predominant roles on the particle size and on the diminishment of impurity. In the growing period of these nanoparticles, the magnetic properties have been demonstrated to follow some size-dependent law.The magnetic properties were found not only related to particle size but also affected by the processing such as the pH value, concentration of precursors, and temperature. The particles become ‘mature’ when conditions are available. Before particles ‘mature’, the magnetic properties are demonstrated to follow some size-dependent law.Download full-size image