Thermo-responsive and aqueous dispersible ZnO/PNIPAM core/shell nanoparticles.

In this work, we developed a new process to covalently graft a thermoresponsive polymer on the surface of fluorescent nanocrystals in order to synthesize materials that combine both responsive and fluorescent properties. For the first time, poly(N-isopropylacrylamide) (PNIPAM) was grown by activator regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) from ZnO quantum dots (QDs) by surface-initiated polymerization. This process allowed the formation of fluorescent and responsive ZnO/PNIPAM core/shell QDs while only requiring the use of a ppm amount of copper for the synthesis. The influence of the nature of the silanized layer and the polymerization time on the properties of the final nanomaterials were investigated. Results clearly evidence that both the PNIPAM layer thickness and the temperature affected the luminescence properties of the core/shell nanoparticles, but also that the PNIPAM layer, when it is thick enough, could stabilize the QDs' optical properties.

Size-controlled synthesis of ZnO quantum dots in microreactors.

In this paper, we report on a continuous-flow microreactor process to prepare ZnO quantum dots (QDs) with widely tunable particle size and photoluminescence emission wavelengths. X-ray diffraction, electron diffraction, UV-vis, photoluminescence and transmission electron microscopy measurements were used to characterize the synthesized ZnO QDs. By varying operating conditions (temperature, flow rate) or the capping ligand, ZnO QDs with diameters ranging from 3.6 to 5.2 nm and fluorescence maxima from 500 to 560 nm were prepared. Results obtained show that low reaction temperatures (20 or 35 °C), high flow rates and the use of propionic acid as a stabilizing agent are favorable for the production of ZnO QDs with high photoluminescence quantum yields (up to 30%).

Fe3O4@ZIF-8: magnetically recoverable catalysts by loading Fe3O4 nanoparticles inside a zinc imidazolate framework.

A simple methodology for encapsulating ca. 10 nm-sized superparamagnetic Fe3O4 nanoparticles in zeolitic imidazolate frameworks (ZIF-8) crystals was developed. The corresponding Fe3O4@ZIF-8 heterostructured material exhibits bifunctional properties with both high magnetization (Fe3O4) and high thermal stability, large specific surface, and catalytic properties (ZIF-8). The Fe3O4@ZIF-8 catalyst exhibits fair separation ability and reusability, which can be repeatedly applied for Knoevenagel condensations and Huisgen cycloadditions for at least ten successive cycles.