The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) can form nonaqueous microemulsions with benzene by the aid of nonionic surfactant TX-100. The effect of water on ionic liquid-in-oil (IL/O) microemulsions was studied, and it was shown that the addition of small amount of water to the IL microemulsion contributed to the stability of microemulsion and thus increased the amount of solubilized bmimBF4 in the microemulsion. The conductivity measurements also showed that the attractive interactions between IL microdroplets were weakened, that is, the IL/O microemulsion becomes more stable in the present of some water. Fourier transform IR was carried out to analyze the states of the added water, and the result showed that these water molecules mainly behaved as bound water and trapped water, indicating that the water molecules are located in the palisade layers of the IL/O microemulsion. Furthermore, 1H NMR and 19F NMR spectra suggested that the added water molecules built the hydrogen binding network of imidazolium cations and H2O, BF4- anion and H2O, and at the same time the electronegative oxygen atoms of the oxyethylene units of TX-100 and water in the palisade layers, which made the palisade layers more firm and thus increased the stability of the microemulsion. The study can help in further understanding the formation mechanism of microemulsions. In addition, the characteristic solubilization behavior of the added water can provide an aqueous interface film for hydrolysis reactions and therefore may be used as an ideal medium to prepare porous or hollow nanomaterials.

Uniform gold nanorods were prepared via a three-step seed-mediated growth method using a long-chain ionic liquid (IL), 1-dodecyl-3-methylimidazolium bromide (C 12 mimBr), as a capping agent. Both AgNO 3 and HNO 3 were used in the synthesis process. The aspect ratio, R, of the nanorods was increased when AgNO 3 was replaced by HNO 3 . HRTEM revealed that these well-crystallized nanorods are all enclosed by five {100} facets and their cross section is pentagon. The interaction energies between the individual surfactants and different gold crystalline planes were calculated using a molecular dynamics simulation. The results showed that the interaction energies between the C 12 mimBr and different gold crystalline planes were smaller than those of CTAB based system. The catalytic experiments showed that the short gold nanorods had excellent catalytic efficiency for the reduction of nitro compounds.

Three-dimensional dendritic gold nanostructures were prepared via an ultrafast one-step homogeneous solution method. Cationic surfactants, decane-1,10-bis(methylpyrrolidinium bromide) ([mpy-C 10 -mpy]Br 2 ), were used as the capping agent and L-ascorbic acid (AA) was used as the reducing agent. The as-prepared gold dendrites present a [111] plane and grow along the AE211ae direction. The AA plays an important role in the formation of the dendritic nanostructures. The methylpyrrolidinium quaternary ammonium headgroups and bolaform nanostructures of the surfactants are the key factors for the formation of dendritic structures. Further investigation revealed that the reaction time and concentration of HAuCl 4 weakly affect the formation of the dendrites. Moreover, the obtained gold dendrites exhibit excellent activity toward the catalytic reduction of p-nitraniline and higher enhancement of surface-enhanced Raman scattering when using Rhodamine 6G as the model molecules. ' INTRODUCTIONShape controlling of nanostructures became the third major topic coordinated with elemental composition and size control in the chemistry of nanostructures 1 since the morphology of nanostructures considerably influences their intrinsic properties and relevant applications. 2 Noble metal nanostructures, especially gold nanomaterials have attracted tremendous interest due to their fascinating physical and chemical properties and promising application in catalysis, nanoelectronics, sensors, photonics, imaging, and biomedicine. 1À3 Great effort has been devoted to synthesize shape-controlled gold nanostructures. 4 Among a variety of gold architectures, such as rods, 5 wires, 6 belts, 7 cubes, 8 polyhedra, 9 plates, 10 stars 11 and dendrites, 12 which have been widely achieved by certain methods, dendritic surpermolecular nanostructures attracted our attention with their unique morphology and properties. Dendritic nanostructures have special texture nanostructures, such as sharp edges or tips, nanoscale junctions and high surface areas, which brought the potential applications in biosensor, electronics, catalysis, and surface-enhanced Raman scattering (SERS) based analysis. 13 However, Au crystals usually exhibit a highly symmetric facecentered cubic (fcc) structure, and the dominant facets possess similar surface free energies. These features lead to the difficulties in forming dendritic nanostructures with complicated morphologies in homogeneous aqueous solution. The good news is that various methods, such as electrochemical, metal-deposition, and the solution-phase method, have been developed to fabricate dendritic noble metal nanostructures in recent years.The electrochemical method is a traditional way to obtain noble metal dendrites or thorn nanostructures. For example, Pt, Ag, and Au branched or dendritic nanostructures were all obtained by this method. 14 The metal deposition method is another way to obtain dendrite nanostructures. Weak reductive metal zinc plate has been used as deposing metal and reducing agent in the fabrica...

The phase behavior of an aqueous catanionic surfactant system, composed of a long-chain imidazolium ionic liquid 1-dodecyl-3-methylimidazolium bromide (C(12)mimBr) and sodium dodecyl sulfate (SDS), is described. The phase diagram of the catanionic system was determined by electrical conductivity measurements and the formation of vesicles in a birefringent L(alpha) phase characterized by transmission electron microscopy (TEM) and freeze-fracture transmission electron microscopy (FF-TEM). Rheological measurements were used to characterize the macroscopic properties of the birefringent L(alpha) phase. Both electrostatic and hydrophobic interactions contribute to the vesicle formation in the catanionic system. Compared to the DTAB/SDS aqueous solution, differences between the imidazolium and trimethylammonium headgroups geometric packing and charge density induce the different phase behavior in each system. Silica hollow spheres, with diameters 30-60 nm and a wall thickness of 8-10 nm, were prepared by using the vesicles as the templates. The hollow silica spheres were characterized by TEM, scanning electron microscopy (SEM), and nitrogen adsorption-desorption. The results suggest additional application for ionic liquid based vesicles to be used as templates for the synthesis of hollow inorganic materials.

Triangular, hexagonal, and truncated triangular single-crystal gold nanoplates are successfully synthesized under Langmuir monolayers of long-chain ionic liquid molecules 1-hexadecyl-3-methylimidazolium bromide (C 16 mimBr) through interfacial reduction of AuCl 4 -by formaldehyde gas. The Au nanoparticles are characterized using transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and UV-vis spectroscopy. It is found that the size of the Au plates varies from several hundred nanometers to several micrometers, up to 20 µm, and the thickness is ca. 35 nanometers. The atomically flat planar surfaces of the Au nanoplates correspond to {111} planes and the lateral surfaces are {110} planes. The concentration of HAuCl 4 aqueous solution strongly influences the formation of the Au nanoplates. The formation of the nanoplates should be attributed to the preferential adsorption of 1-hexadecyl-3-methylimidazolium cations onto the {111} planes of Au nuclei and the connection of small, triangular nanoplates.