Transparent 'solution' of ultrathin magnesium hydroxide nanocrystals for flexible and transparent nanocomposite films.

Transparent solutions of nanocrystals exhibit many unique properties, and are thus attractive materials for numerous applications. However, the synthesis of transparent nanocrystal solutions of magnesium hydroxide (MH) with wide applications is yet to be realized. Here, we report a facile two-step process, which includes a direct reactive precipitation in alcohol phase instead of aqueous phase combined with a successive surface modification, to prepare transparent alcohol solutions containing lamellar MH nanocrystals with an average size of 52 nm and an ultrathin thickness of 1-2 nm, which is the thinnest MH nanoplatelet reported in the literatures. Further, highly flexible and transparent nanocomposite films are fabricated with a solution mixing method by adding the transparent MH nanocrystal solutions into PVB solution. Considering the simplicity of the fabrication process, high transparency and good flexibility, this MH/polymer nanocomposite film is promising for flame-resistant applications in plastic electronics and optical devices with high transparency, such as flexible displays, optical filters, and flexible solar cells.

Preparation of azithromycin nanosuspensions by reactive precipitation method.

PURPOSE: The aim of this work was to prepare azithromycin (AZI) nanosuspensions to increase the solubility and dissolution rate. METHOD: AZI nanosuspensions were prepared by the combination of reactive precipitation and freeze-drying in presence of biocompatible stabilizer. Formulation and process variables affecting the characteristics of nanosuspensions were optimized. Various tests were carried out to study the physicochemical characteristics of AZI nanosuspensions. RESULTS: The nanosuspensions were parenterally acceptable and autoclavable, because soybean lecithin was the stabilizer of choice and no organic solvents were used during the preparation. The mean particle size and zeta potential of the AZI nanosuspensions were about 200 nm (±20 nm) and -36.7 mV (±7.6 mV), respectively. Solid nanoparticles were obtained by lyophilization of the nanosuspensions and nanosuspensions rapidly reconstituted when the nanoparticles were dispersed in water. X-ray diffraction and differential scanning calorimetry analysis showed that the crystal state of nanoparticles was amorphous. Solubility and in vitro release studies indicated that the saturated solubility and dissolution rate increased obviously in comparison of raw AZI. The nanoparticles were physically stable over a period of 5 months as demonstrated by unchanged crystallinity and stable particle size when stored at room temperature and protected from humidity. CONCLUSION: The results suggested that reactive precipitation is an effective way to prepare AZI nanosuspensions with increased solubility and dissolution rate.

Controlled release of avermectin from porous hollow silica nanoparticles.

Porous hollow silica nanoparticles (PHSNs) with a diameter of ca 100 nm and a pore size of ca 4.5 nm were synthesized via a sol-gel route using inorganic calcium carbonate nanoparticles as templates. The synthesized PHSNs were subsequently employed as pesticide carriers to study the controlled release behaviour of avermectin. The avermectin-loaded PHSN (Av-PHSN) samples were characterized by BET, thermogravimetric analysis and IR, showing that the amount of avermectin encapsulated in the PHSN carrier could reach 58.3% w/w by a simple immersion loading method, and that most of the adsorption of avermectin on the Av-PHSN carrier might be physical. Avermectin may be loaded on the external surface, the pore channels in the wall and the inner core of the PHSN carriers, thus leading to a multi-stage sustained-release pattern from the Av-PHSN samples. Increasing pH or temperature intensified the avermectin release.

Dispersion of nanosized aqueous suspensions of barium titanate with ammonium polyacrylate.

The colloidal stability of nanosized barium titanate (BaTiO3) aqueous suspensions with ammonium polyacrylate (PAA-NH4) at different pH values has been investigated by means of zeta potential, adsorption isotherm, sedimentation, and rheology characterization. The isoelectric point of BaTiO3 powders is at pH 2.5 and the value of zeta potential is at its maximum near pH 10. The amount of leached barium ion decreases with increasing pH, but the change decreases with increasing initial pH. Adsorption of PAA-NH4 onto the surface of BaTiO3 decreases its zeta potential. Results show that PAA-NH4 adsorption follows Langmuir monolayer adsorption isotherms and the amount of PAA-NH4 required to stabilize nanosized BaTiO3 suspensions decreases as the pH increases. The mechanism of stabilization of BaTiO3 is shown to be electrosteric under the experimental conditions. Good agreement between zeta potential, sedimentation, and rheological tests is found, which identifies an optimum pH value of about 10 and an optimum dispersant concentration of about 2.0 wt%, independent of the solids volume fraction of suspensions.