Synthesis Of Nanomaterials With Special Wettability And Their Applications In Transportation Of Droplet Underwater

Manipulation of microdroplet was attracted much attention in the fields of miniaturized chemical reaction, biological analysis, controlled release of drug, no-loss droplet transportation and synthesis of nanomaterials due to the advantages of high accuracy in manipulation and low contamination for environment. However, the problems, such as the evaporation of liquid, high cost for the sophisticated equipment and cumbersome manipulation method still impeded the development of the manipulation of microdroplets. In order to avoid these problems, we reported transportation of droplet in water by using superhydrophobic and superoleophobic nanomaterials, respectively. Driven by magnetic field, thermal or light, the microdroplet could move in a controlled way. In additon, we also have realized the mixture of different kinds of organic reagents in water by these superhydrophobic or superoleophobic nanomaterials. The results in this dissertation will have application prospect in miniaturized chemical reaction and analysis.Firstly, we synthesized three-dimensionally porous magnetic Fe（Co or Ni）/C nanocomposites by sintering the mixture of polystyrene（PS） microspheres and Fe（NO3）3, Co（NO3）2 or Ni（NO3）2 precursors, respectively. Owing to the superhydrophobic and superoleophilic properties, the as-prepared nanocomposites could absorb the oil on the water surface quickly. Then the absorbed oil began to move in water under the auction of magnetic field. With the assistance of magnetic field, this oil could not only transport in the water freely, but also contact with the other kinds of oil droplets that were stable on the bottom of water. In addition, the oil-absorbed nanomaterials also could be removed from the water by the magnet. Owing to the high corrosion resistance capacity of porous magnetic Fe（Co or Ni）/C nanocomposites, this oil transportation method could be applied in harsh aqueous solutions.In order to transport an oil droplet from the bottom to the surface of water, the thermal responsive SiO₂（Fe₃O₄ or PS）-Poly（N-Isopropylacrylamide）（PNIPAm） nanocomposites were used. The as-prepared nanocomposites were first coated on the surface of oil droplet at room temperature. Since the encapsulated nanocomposites isolated the contacting of oil droplet with substance, this droplet could move easily without liquid contamination and loss. In addition, the encapsulated layer also prevented the escaping of bubbles which generated from the nanocomposites and droplet by tuning the water temperatur e. Owing to the bubble, the oil droplet could transport and shutle in water. Under the driven of magnetic field, the movement direction of Fe₃O₄-PNIPAm encapsulated droplet also could be controlled freely. In this section, by tuning the temperature, the as-prepared thermal responsive nanoparticals were good candidates to transport oil droplet（e.g. CHCl₃, CH₂Cl₂ or CCl₄） in the water.Besides, the photothermal nanocomposites, which were synthesized by the polymerization of dopamine on the surface of Fe₃O₄ nanocomposites, were used to encapsulate and transport the oil droplet（e.g. CHCl₃, CH₂Cl₂ or CCl₄） in a more presice and controlled way. By controlling the irradiation conditions of the near-infrared（NIR） laser, a bubble with tunable volume was generated in oil droplet so as to transport this encapsulated droplet controllably. The suspending and shuttling of oil droplet during the transportation were completed by the laser. In addition, the encapsulated layer could be opened and closed reversibil ity. Therefore, the compent in the droplet could be changed. The manipulation of the microdroplet by the NIR laser could provide a new way for the operation of intelligent miniature reactors.