•Hollow silica nanospheres were fabricated in O/W microemulsion.•Morphological transformation can be realized by regulating hydrothermal temperature.•Mechanism for morphological transformation was proposed.•CRL was immobilized in HSN and served as catalyst for esterification.Hollow silica nanospheres with wrinkled or smooth surfaces were successfully fabricated through a hydrothermal method. In this method, oil-in-water microemulsion (composed of cyclohexane, water, ethanol, and cetyltrimethylammonium bromide), and polyvinylpyrrolidone were utilized as template and capping agent, respectively. In such a facile synthesis, we can well realize the morphological transformation of spheres with radially oriented mesochannels to hollow structures of silica nanoparticle only by regulating the hydrothermal temperature from 100 °C to 200 °C. Synthesized samples with different mesostructures were then used as supports to immobilize Candida rugosa lipase (CRL). The immobilized CRL was employed as a new biocatalyst for biodiesel production through the esterification of heptanoic acid with ethanol. The conversion ratio of heptanoic acid with ethanol catalyzed by the immobilized CRL was also evaluated. Results of this study suggest that the prepared samples have potential applications in biocatalysis.

•Anatase TiO2 nanorods enclosed by {100}, {001} and {101} facets were prepared.•The size and morphology were tuned by regulating the hydrothermal temperature.•The addition of CTAB, DDAB and ammonia affect the exposed facets of nanorods.•TiO2 nanorods obtained at 150 °C produced high amounts of H2 evolution.In this study, anatase TiO2 nanorods with exposed high-energy {100} and {001} facets and low-energy {101} facets were fabricated in the presence of surfactants cetyltrimethylammonium bromide, didecyldimethylammonium bromide, and ammonia via a facile hydrothermal method without the erosive reagent hydrofluoric acid. The particle size and morphology were mainly tuned by regulating the hydrothermal temperature. When the temperature was increased from 150 °C to 180 °C and 200 °C, the length of the nanorods decreased from 700-1000 nm to 400–500 nm and 100–200 nm, respectively. Concurrently, the edges and tops of the truncated tetragonal pyramid of the TiO2 nanorods became blurry and flattened. The synthesized typical TiO2 nanorods were then used as photocatalysts, and their performance during the direct generation of H2 from water was evaluated. The TiO2 nanorods obtained at 150 °C successfully produced high amounts of H2 evolution (281.36 μmol) in the presence of methanol as a sacrificial agent under ultraviolet light irradiation for 4 h. The outstanding photocatalytic activity of the nanorods was mainly ascribed to the formation of surface heterojunctions in the edges and corners between adjacent high-energy {001} or {100} facets and low-energy {101} facets. The formed heterojunctions could facilitate charge separation through preferential carrier flow toward the specific facets.Download high-res image (195KB)Download full-size image

Vesicular polyaniline (VPANI) has been fabricated for the first time via a facile two-step method, which uses high-quality multilamellar vesicular SiO2 as hard templates. The graphene-wrapped VPANI (VPANI@RGO) composites were prepared by self-assembling graphene oxide onto VPANI and subsequently conducting the hydrothermal reduction process. The morphological characterization of the composites confirms the uniform wrapping of the graphene sheets on the VPANI. The structural characterization of the composites reveals a strong π–π electron and hydrogen bond interaction in the composites. The VPANI@RGO composites exhibit an excellent supercapacitor performance with an enhanced specific capacitance (573 F g−1) and a good cycling stability, which maintains its capacity of up to 85.7 % over 1000 cycles at 1 A g−1.

Morphology-controllable silica-based nanostructures (MC SiO2Ns) have been comprehensively studied because of their potential practical applications in various fields, such as biological chemistry. The superior properties of these nanostructures, including low density, biocompatibility, thermal stability, and high mechanical strength, have been the focus of research to improve their current performance. In this review, experimental parameters, morphology, and formation mechanism of MC SiO2Ns (including vesicle-like mesoporous silica, rod-like mesoporous silica, and silica mesoporous nanospheres) are discussed. Moreover, current progress in functionalization and performance improvement of MC SiO2Ns is presented. Applications of MC SiO2Ns in immobilization techniques, biological catalysis, and drug delivery are also provided.

This paper presents an improved strategy for synthesizing short rod-shaped mesoporous SiO2@TiO2 composites containing a TiO2 shell by using short rod-shaped mesoporous SiO2–polyglycidyl methacrylate (PGMA)–polyoligo(ethylene glycol)methyl ether methacrylate (PEGMA) as a template and tetrabutyl titanate (TBT) as a titanium source. SiO2–PGMA-b-PEGMA rods were initially fabricated through grafting GMA and EGMA onto the surface of the halogen functional group of mesoporous SiO2 using activators regenerated by electron transfer-atom transfer radical polymerization. TBT was hydrolyzed with the PEGMA chain through hydrogen bonding. The rod-shaped mesoporous SiO2@TiO2 structure was finally acquired through calcination. Characterization results indicated that the amphiphilic block copolymer was grafted onto the mesoporous SiO2 surface. Moreover, the TiO2 samples existed only in the anatase phase, and the prepared SiO2@TiO2 exhibited bimodal nanoporous structures. The synthesized short rod-shaped mesoporous SiO2@TiO2 materials demonstrated higher specific surface area and absorption rate than samples prepared from non-mesoporous or unmodified rod-shaped SiO2. These characteristics effectively enhanced the photocatalytic activity of the composite. The photocatalytic activity of the fabricated composite was then tested on rhodamine B photodegradation.

Changes in the morphology of mesoporous silica from vesicular to worm-like to vesicular multilamellar were controlled by adding appropriate amounts of β-cyclodextrin to mixed cetyltrimethylammonium bromide/didodecyldimethylammonium bromide surfactant aggregates.

•WSNs having radially oriented mesochannels were synthesized by a solvothermal method.•Pore structures of WSNs were varied using different molar ratios of CTAB to PVP.•WSNs were applied as carriers to immobilize CRL.•Esterification of oleic acid with methanol was catalyzed by WSNs-CRL.•WSNs-CRL were used as an efficient biocatalyst in the synthesis of biodiesel.Mesoporous silica nanoparticles with a wrinkled structure (wrinkled silica nanoparticles, WSNs) having highly ordered, radially oriented mesochannels were synthesized by a solvothermal method. The method used a mixture of cyclohexane, ethanol, and water as solvent, tetraethoxysilane (TEOS) as source of inorganic silica, ammonium hydroxide as hydrolysis additive, cetyltrimethylammonium bromide (CTAB) as surfactant, and polyvinylpyrrolidone (PVP) as stabilizing agent of particle growth. Particle size (240 nm to 540 nm), specific surface areas (490 m2 g− 1 to 634 m2 g− 1), surface morphology (radial wrinkled structures), and pore structure (radially oriented mesochannels) of WSN samples were varied using different molar ratios of CTAB to PVP. Using synthesized WSN samples with radially oriented mesochannels as support, we prepared immobilized Candida rugosa lipase (CRL) as a new biocatalyst for biodiesel production through the esterification of oleic acid with methanol. These results suggest that WSNs with highly ordered, radially oriented mesochannels have promising applications in biocatalysis, with the highest oleic acid conversion rate of about 86.4% under the optimum conditions.