Fei Geng

Synthesis and Characterization of Mesoporous Silica Templated by Amphiphilic RTILs

This article reports a novel preparation of mesoporous silica with series of 1-alky-3-methylimidazolium bromide (CnMIM)Br (n = 12, 14, 16), a kind of amphiphilic room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The pore morphology and structures of these mesoporous silica were characterized by Transmission electron microscopy (TEM). The results show that the RTIL bearing longer alkyl chain is preferred to form the mesoporous silica material with bigger pores. (C16MIM)Br has been chosen to study how the various influencing factors affect the synthesis and structure of the mesoporous silica material, such as the acid concentration, the solling time, the gelling time and the calcination time. N2 adsorption-desorption isotherms measurement was used to characterize the pore size distribution and BET surface area. The results indicate that all of the factors can make an influence on the preparation of the mesoporous silica, which is more sensitive to the concentration of the acid.

Studies on the Effects of Additional Components on Micellization of CTAB via Surface Tension Measurements

The effects of Tris-HCl buffer solution on the cmc of cetyltrimethylammonium bromide (CTAB) were studied by surface tension measurement. The result shows that the effect of the buffer solution depends on the interaction between CTAB and NaCl and the structure accelerants of water, Tris. A series of parameters, including the critical micelle concentration (cmc), the surface tension at cmc (γcmc), the adsorption efficiency (pC20), and the effectiveness of surface tension reduction (∏cmc) were obtained from the surface tension measurements in the presence of glycine with different concentration in the Tris-HCl buffer solution at 27°C. In addition, maximum surface excess concentration (Γ max) and minimum surface area per molecule (Amin) at the air-water interface were estimated according to the Gibbs adsorption isotherm. The thermodynamic parameters (Δ C p,m , Δ H m,tr , Δ C p,m,tr ) of micellization for CTAB in the absence and presence of glycine at different temperature were also been obtained.

Effects of Chloramphenicol on the Characterization of Solid Lipid Nanoparticles and Nanostructured Lipid Carriers

The effects of chloramphenicol on the characterization of solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) have been studied in this work. Microemulsion technique of solid lipid above the melting point with or without liquid lipid was used to prepare NLC and SLN dispersions, respectively. The physicochemical properties of the carriers were investigated, such as the morphological, the crystalline structures of the particles by wide x-ray diffraction (WXRD), the crystal order by differential scanning calorimetry (DSC). The results indicate that the average diameters and zeta potentials of SLN and NLC with chloramphenicol were larger than those without chloramphenicol. DSC and WXRD analysis show that chloramphenicol in the lipid matrix of SLN and NLC is in an amorphous state. In vitro release studies were carried out to indicate that the liquid oil in the solid lipid leads to the low degree of crystallinity. It displays higher cumulative release rate. The release mechanism has been discussed.

Rheological Properties of Wormlike Micelles Formed by Cetyltrimethylammonium Bromide and Sodium Laurate

Aqueous solutions of mixed cationic and anionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium laurate (SL), have been studied by steady-state rheology and dynamic oscillatory technique. Wormlike micelles can form due to attractive interactions between the oppositely charged headgroups of CTAB and SL. The wormlike micelles formed by CTAB/SL have been compared with that of cetylpyridinium bromide (CPB)/SL by steady-state rheology method. Effects of additional components such as NaBr, 1-propanol, 1-butanol, polyvinylpyrrolidone (PVP) on the micelles formation process have also been investigated. Cole-Cole plot has been applied to study the dynamic viscoelasticity of the wormlike micelles.