Chunfang Li

Facile synthesis of concentrated gold nanoparticles with low size-distribution in water: temperature and pH controls

The citrate reduction method for the synthesis of gold nanoparticles (GNPs) has known advantages but usually provides the products with low nanoparticle concentration and limits its application. Herein, we report a facile method to synthesize GNPs from concentrated chloroauric acid (2.5 mM) via adding sodium hydroxide and controlling the temperature. It was found that adding a proper amount of sodium hydroxide can produce uniform concentrated GNPs with low size distribution; otherwise, the largely distributed nanoparticles or instable colloids were obtained. The low reaction temperature is helpful to control the nanoparticle formation rate, and uniform GNPs can be obtained in presence of optimized NaOH concentrations. The pH values of the obtained uniform GNPs were found to be very near to neutral, and the pH influence on the particle size distribution may reveal the different formation mechanism of GNPs at high or low pH condition. Moreover, this modified synthesis method can save more than 90% energy in the heating step. Such environmental-friendly synthesis method for gold nanoparticles may have a great potential in large-scale manufacturing for commercial and industrial demand.

Ionic liquid microemulsions of 1-butyl-3-methylimidazolium hexafluorophosphate, N,N-dimethylformamide, and water

The phase behavior of a ternary system consisting of the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), N,N-dimethylformamide, and water was investigated. Single-phase microemulsion and multiphase regions were observed in the ternary phase diagram. To the best of our knowledge, this is the first report of aqueous IL microemulsions prepared in the absence of traditional surfactants, i.e., surfactant-free microemulsions (SFMEs) containing IL. The microstructures and structural transitions of the aqueous IL SFMEs were investigated using cyclic voltammetry, electrical conductivity, and dynamic laser light scattering techniques. The results showed that the aqueous IL SFMEs exhibit IL-in-water, bicontinuous, and water-in-IL microstructures, similar to the case of traditional surfactant-based microemulsions. The three kinds of microstructures were confirmed from freeze-fracture electron microscopy observations. Ultraviolet-visible and fluorescence spectroscopies were used to examine the polarities of microdomains in the microemulsions, using methyl orange and pyrene, respectively, as probes. It was found that these two techniques can be used to identify the microstructures and microstructural transitions of the aqueous IL microemulsions.

Dendritic amphiphiles of carbosilane dendrimers with peripheral PEG for drug encapsulation

Amphiphilic dendritic macromolecules are suitable for the noncovalent encapsulation of guest molecules and could potentially be applied in drug-delivery systems. In this work, amphiphilic carbosilane dendrimers with peripheral poly(ethylene glycol) (PEG) units were synthesized using a hydrosilylation reaction, and their encapsulation properties were studied by fluorescence spectroscopy, using pyrene as the probe molecule. The results showed that the encapsulating capacity of the dendrimers increased as the number of PEG units increased, and that it also depended to some degree on the dendrimer generation.