Colloidally Confined Crystallization of Highly Efficient Ammonium Phosphomolybdate Catalysts.

Nanodroplets in inverse miniemulsions provide a colloidal confinement for the crystallization of ammonium phosphomolybdate (APM), influencing the resulting particle size. The effects of the space confinement are investigated by comparing the crystallization of analogous materials both in miniemulsion and in bulk solution. Both routes result in particles with a rhombododecahedral morphology, but the ones produced in miniemulsion have sizes between 40 and 90 nm, 3 orders of magnitude smaller than the ones obtained in bulk solution. The catalytic activity of the materials is studied by taking the epoxidation of cis-cyclooctene as a model reaction. The miniemulsion route yields APM particles catalytically much more active than analogous samples produced in bulk solution, which can be explained by their higher dispersibility in organic solvents, their higher surface area, and their higher porosity. Inorganic phosphate salt precursors are compared with organic phosphate sources. APM nanoparticles prepared in miniemulsion from d-glucose-6-phosphate and O-phospho-dl-serine yield a conversion in the epoxidation reaction of more than 90% after only 1 h, compared to 30% for materials prepared in bulk solution. In addition, the catalysts prepared in miniemulsion display a promising recyclability.

Amino-acid-based chiral nanoparticles for enantioselective crystallization.

Chiral polymer nanoparticles based on amino acids are prepared by miniemulsion polymerization and are demonstrated to serve as nucleating agents for the enantioselective crystallization of racemic mixtures of amino acids. The synthesized chiral nanoparticles are suited for the development of enantioselective processes and also contribute to a better understanding of chiral recognition on polymer surfaces.

Molecularly Controlled Coagulation of Carboxyl-Functionalized Nanoparticles Prepared by Surfactant-Free Miniemulsion Polymerization.

We present the synthesis of molecularly controlled "CO2-switchable" polystyrene nanoparticles by surfactant-free miniemulsion polymerization using a carboxyl-functionalized surface-active monomer, which acts as comonomer and stabilizer at the same time. The obtained nanoparticles are about 100 nm in size and show a small size distribution, confirmed by dynamic light scattering (DLS) and electron microscopy. Under ambient conditions, the latex particles form a stable suspension that can be coagulated by bubbling CO2. The redispersion of the coagulated particles can be easily achieved by ultrasonication. The reversibility of the coagulation is confirmed after several coagulation/redispersion cycles (CO2 bubbling and ultrasonification) from DLS and zeta potential measurements.

Conjugated oligothienyl dendrimers based on a pyrazino[2,3-g]quinoxaline core.

The synthesis of a new series of conjugated dendrimers based on an electron-accepting core is introduced. The compounds showed broad absorption bands over 300-700 nm and have reduced HOMO-LUMO gaps of 1.7-1.9 eV. Incorporation of these compounds in bulk heterojunction solar cells as electron-donating material along with PC61BM as electron acceptor gave power conversion efficiencies of up to 1.3% for the second-generation dendrimer.