Zhongbin Ni

Chelating template-induced encapsulation of NiO cluster in mesoporous silica via anionic surfactant-templated route.

In this study, we develop a novel one-step method for synthesis of nickel oxide/silicon dioxide (NiO/SiO(2)) mesoporous composites by using N-hexadecyl ethylenediamine triacetate (HED3A) as structure-directing agent. Besides playing a role in directing the mesophase formation, the anionic surfactant also functions as a chelating agent that binds nickel ions. Ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopic analyses were undertaken to determine the chelating ability between HED3A and nickel ions. By adjusting the molar ratio of Ni(2+)/HED3A in the template solution, a series of mesoporous composites with various NiO contents were obtained after calcination. These composites were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and nitrogen adsorption/desorption. The results showed that the generated NiO nanoparticles were aggregated into clusters with the size less than 20 nm, and the composites retained mesoporous characteristics even with high NiO contents. HRTEM images also revealed the migration and aggregation for NiO nanoparticles during the sintering process. Moreover, the energy-dispersive X-ray spectrum (EDX) results showed a close linear relationship between Ni/Si in the composites and Ni(2+)/HED3A in the templates. This chelating surfactant-assistant encapsulation route has the potential to synthesize diversiform metal oxide/silica mesoporous composites with designated compositions.

pH-Sensitive Micelles Based on Double-Hydrophilic Poly(methylacrylic acid)-Poly(ethylene glycol)-Poly(methylacrylic acid) Triblock Copolymer

AbstractpH-sensitive micelles with hydrophilic core and hydrophilic corona were fabricated by self-assembling of triblock copolymer of poly(methylacrylic acid)-poly(ethylene glycol)-poly(methylacrylic acid) at lower solution pH. Transmission electron microscopy and laser light scattering studies showed micelles were in nano-scale with narrow size distribution. Solution pH value and the micelles concentration strongly influenced the hydrodynamic radius of the spherical micelles (48–310 nm). A possible mechanism for the formation of micelles was proposed. The obtained polymeric micelle should be useful for biomedical materials such as carrier of hydrophilic drug.

Synthesis and Characterization of NiO/Mesoporous Silica Nanocomposite

NiO/mesoporous silica nanocomposite was synthesized through anionic-surfactant-templated route by using N-hexadecyl ethylenediamine triacetate (HED3A) as structure directing agent. A temperature of 600°C was chosen to remove the template after an initial thermogravimetric (TG) analysis. Based on the metal sequestration of the template, Ni2+ was introduced into silica matrix and NiO was finally embedded into mesopores after calcination. The composition of NiO/mesoporous silica composite was qualitatively characterized and quantitatively expressed by Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) pattern and Energy-dispersive X-ray (EDX) spectroscopy. The composite with high nickel content has a BET surface area reached 676 m2g−1 and a pore diameter centered at 3-4 nm. Small-angle X-ray diffraction (SAXRD) pattern indicates that the material possesses ordered two-dimensional (2-D) p6mm hexagonal mesostructure. High resolution transmission electron microscopy (HRTEM) investigation on the structural characteristics confirms the mesostructure and shows that NiO clusters with a uniform size of 15 nm are encapsulated in mesoporous silica.

Studies on syntheses and dynamic swelling of pH-sensitive macroporous poly(N-isopropylacrylamide-co-acrylic acid) hydrogels

A series of macroporous poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-AA) hydrogels with different composition were synthesized by free-radical copolymerization in the presence of silica particles as a pore generating agent. The equilibrium swelling ratio, half swelling time and dynamic swelling kinetics of the copolymers previously soaked in different acidic buffer solutions were investigated at pH 7 at 25°C. Experimental results revealed that the swelling rate of the macroporous hydrogels was greatly increased compared to conventional hydrogels due to existence of the macroporous structures. It was found that the swelling history of previously putting in acidic solutions copolymers had strong influence on their dynamic swelling kinetics especially for the samples ranging in composition between 30 and 70 mol % of NIPAAm, whereas the swelling history had little influence on the equilibrium swelling ratio of copolymers. The swelling pattern exhibits sigmoid swelling curves. This is explained by an autocatalytic mechanism. The hydrogen bonding dissociation plays an important role in the dynamic swelling behavior.

Preparation and properties of micelle nanoparticles by P4VP-b-PMAA copolymer

Poly(4-vinylpyridine) with a chlorine end group (P4VP-Cl) was first prepared via atom transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP) initiated by ethyl-2-chloropropionate (ECP). The effect of polymerization time on the number-average molecular weight (Mn) of the P4VP-Cl was studied based on gel permeation chromatography (GPC). The Mn of P4VP-Cl can be controlled from 1500 to 5610 by adjusting. Poly(4-vinylpyridine)-b-poly( tert-butylmethacrylate) (P4VP-b-PtBMA) was then prepared by ATRP using P4VP-Cl as macroinitiator. In the case, the conversion of tBMA can reach 60%. Furthermore, the P4VP-b-PtBMA was then hydrolyzed under room temperature to form P4VP-b-PMAA in the presence of CF3COOH. The self-assembly of P4VP-b-PMAA in selective solvents was also studied by scanning electron microscopy (SEM).

A novel chelating surfactant templating pathway for preparation of Co 3 O 4 /silica mesoporous composite

A metal-containing surfactant [Co(HED3A)⁻N⁺ formed by trisodium N-hexadecyl ethylenediamine triacetate (3NaHED3A) and CoCl<inf>2</inf> was first used as template for synthesizing Co<inf>3</inf>O<inf>4</inf>/SiO<inf>2</inf> mesoporous composite. TG showed that the proper temperature for removal of template is 600°C. Nitrogen adsorption-desorption isotherms data confirmed that the composite has a high specific surface area and uniform pore size distribution. The morphology and structure of mesoporous composite were characterized by X-ray diffraction and HRTEM. Results show that the complex has regular cubic shape morphology with particle size in the range of 1–1.5µm. The material has a highly ordered cubic (pm3n) mesostructure and long-ranged ordered porous channel. Co<inf>3</inf>O<inf>4</inf> was uniformly distributed in the well-defined channel as a result of the guiding role of the template.