α-Sulfonyloxylation of 1,3-dicarbonyl compounds utilizing hypervalent iodine(iii) reagent: Construction of quaternary carbon center

<p>An efficient method for direct α-sulfonyloxylation of various sterically hindered 1,3-dicarbonyl compounds has been developed under mild reaction conditions. The yields of desired products is up to 90% and a plausible mechanism was accordingly proposed.</p

Arginine-Assisted Hydrothermal Synthesis of Urchin-like Nb₂O₅ Nanostructures Composed of Nanowires and Their Application in Cyclohexanone Ammoximation

Urchin-like Nb₂O₅ nanostructures have been successfully synthesized by a novel and simple l-arginine-assisted hydrothermal method. They are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption–desorption isotherms, thermogravimetric and differential thermal analysis (TG-DTA), and Fourier transform infrared spectroscopy (FT-IR). The results show that the urchin-like nanostructures are composed of nanowires with diameter less than 15 nm and possess a high specific surface area of 249.9 m²·g^–1. Urchin-like Nb₂O₅ nanostructures have been used for the first time as a novel catalyst instead of conventional titanosilicate in the liquid-phase ammoximation of cyclohexanone. The as-prepared urchin-like Nb₂O₅ nanostructures exhibit high catalytic activity in cyclohexanone ammoximation. Under the optimal reaction conditions, the conversion of cyclohexanone and selectivity of oxime are as high as 98.0% and 88.9%, respectively. Finally, a possible formation mechanism of urchin-like Nb₂O₅ nanostructures is proposed

Nanoparticle Vesicles with Controllable Surface Topographies through Block Copolymer-Mediated Self-Assembly of Silica Nanospheres

Silica nanoparticle vesicles (NPVs) with encapsulating capability and surface permeability are highly attractive in nanocatalysis, biosensing, and drug delivery systems. Herein, we report the facile fabrication of silica NPVs composed of a monolayer of silica nanospheres (SNSs, ca. 15 nm in diameter) through the block copolymer-mediated self-assembly of SNSs. The silica NPVs gain different surface topographies, such as raspberry- and brain coral-like topographies, under controlled heat treatment conditions. The vesicular assembly of SNSs is successful with a series of poly­(propylene oxide)-poly­(ethylene oxide)-poly­(propylene oxide) block copolymers, and the size of NPVs can be tuned by changing their molecular weight. The polymer is easily extracted from the NPVs with their colloidal dispersibility and structural integrity intact. The polymer-free silica NPVs further serve as a reaction vessel and host for functional materials such as tin oxide nanoparticles

One-Dimensional Assembly of Silica Nanospheres: Effects of Nonionic Block Copolymers

The effects of polymers on the one-dimensional assembly of silica nanospheres (SNSs) in the liquid phase are systematically investigated using nonionic poly­(ethylene oxide)-<i>b</i>-poly­(propylene oxide)-<i>b</i>-poly­(ethylene oxide) (abbreviated as PEO-PPO-PEO) triblock copolymers with varying hydrophilic–lipophilic balance (HLB) values. Scanning electron microscopy is employed for morphological observations of the polymer-mediated assemblies of SNSs on the basis of which the optimal pH for 1D assembly (pH_1D) is determined. To clarify the polymers’ effects on the 1D assembly of SNSs, the relationships between pH_1D and polymers’ HLB values, the numbers of hydrophilic EO and hydrophobic PO units, and the relative ratio of <i>N</i>_PO/<i>N</i>_EO are examined. Zeta potential measurements are conducted to investigate the electrostatic repulsion among the SNSs in the presence of block copolymers. It is found that the relative hydrophilicity of the block copolymers greatly affects the balance of interactions in the 1D assembly of SNSs. Block copolymers with large HLB values promote the 1D assembly of SNSs under near-neutral pH conditions, whereas the block copolymers with small HLB values promote 1D assembly under basic pH conditions. Therefore, the 1D assembly of SNSs is achieved over an extensive pH range (7.5–9.5) through the employment of block copolymers of different hydrophilic and hydrophobic block lengths

Block Copolymer as a Surface Modifier to Monodisperse Patchy Silica Nanoparticles for Superhydrophobic Surfaces

Monodisperse patchy silica nanoparticles (PSNPs) less than 100 nm are prepared based on the seed-regrowth method using a poly­(ethylene oxide) (PEO)–poly­(propylene oxide) (PPO)–PEO-type block copolymer as a surface modifier. Well-defined patches are controllably synthesized through area-selective deposition of silica onto the surface of seeds. After colloidal PSNPs are further modified with trimethylchlorosilane, the advancing and receding contact angles of water for PSNPs are 168 ± 2° and 167 ± 2°, respectively. The superhydrophobic and transparent coatings on the various types of substrates are obtained by a simple drop-casting procedure. Additionally, almost the same superhydrophobicity can be achieved by using colloidal PSNPs via redispersing the powder of superhydrophobic PSNPs in ethanol

Block Copolymer as a Surface Modifier to Monodisperse Patchy Silica Nanoparticles for Superhydrophobic Surfaces

Monodisperse patchy silica nanoparticles (PSNPs) less than 100 nm are prepared based on the seed-regrowth method using a poly­(ethylene oxide) (PEO)–poly­(propylene oxide) (PPO)–PEO-type block copolymer as a surface modifier. Well-defined patches are controllably synthesized through area-selective deposition of silica onto the surface of seeds. After colloidal PSNPs are further modified with trimethylchlorosilane, the advancing and receding contact angles of water for PSNPs are 168 ± 2° and 167 ± 2°, respectively. The superhydrophobic and transparent coatings on the various types of substrates are obtained by a simple drop-casting procedure. Additionally, almost the same superhydrophobicity can be achieved by using colloidal PSNPs via redispersing the powder of superhydrophobic PSNPs in ethanol