Inorganic Nanomaterials And Inorganic/Polymer Nanocomposites Obtained By Emulsion Method

Emulsion is a common method for the preparation of nanomaterials. Microemulsion whichemploys the use of nanscale microreactor in particular, due to its advantages of simple process aswell as control of particle size and morphology, has become a research hotspot in recent decades.Simultaneous ultrasound and microwave radiation is a recently developed green, efficient synthesistechnology, which overcomes the disadvantage of the separate ultrasound and microwave radiation,and combines the advantages of both ultrasonic and microwave radiation, so it is receivingincreasing attention. In this paper, we introduced ultrasound and microwave radiation to prepareCdS spherical nanocrystal clusters and one-dimensional （1D） Fe₃O₄/polystyrene （PS） in themicroemulsion, and also adopted a one-step, wild reverse emulsion to obtain hollow Fe₃O₄/SiO₂magnetic microcapsules. On the basis of preparation, we characterized the size and morphology ofnanomaterials, measured the properties and also investigated the formation mechanism. Thedetailed works are as follows:（1） Synthesis of spherical CdS nanonanocrystal clusters by simultaneous ultrasound andmicrowave radiation in the reverse microemulsionCdmium sulfate（CdSO₄·8H₂O）and sodium sulfate（NaS₂O₃·5H₂O） were used as precursors toprepare diameter controlled spherical CdS nanocrystal clusters through one-step reversemicroemulsion with simultaneous ultrasound and microwave radiation. The spherical CdSnanocrystal clusters were characterized by transmission electron microscope （TEM） and selectedarea electron diffraction （SAED）, the results indicated that the spherical nanocrystal clusters werecubic close packing with diameter between35nm to75nm contained sphalerite as the main phase.UV-Vis and PL spectra analysis showed that spherical CdS nanocrystal clusters exhibited blue-shift compared with massive CdS, which confirmed the quantum-confined effect. Meanwhile, theeffect of water-oil volume ratio on the morphology of nano spherical nanocrystal clusters wasexamined, the results showed that with the increase of water-oil volume ratio, namely, water andsurfactant mass ratio increases, the diameter and dispersion of spherical CdS nanocrystal clustersincrease; In the=0.4microemulsion, the contributions of ultrasound and microwave have been studied, the results indicated that the spherical nanocrystal clusters synthesized by combinedultrasound and microwave radiation were well dispersed and had a narrow size distribution. Inaddition, this experiment also showed that microwave radiation played a lead role, while ultrasonicassisted microwave radiation in the whole process.（2） Synthesis of Fe₃O₄/PS nanorods by simultaneous ultrasound and microwave radiation inthe microemulsionThe Fe₃O₄/PS nanorods were synthesized through two steps, that is, preparation of Fe₃O₄nanoparticles in the microemulsion, then polymerization of styrene under the simultaneousultrasound and microwave radiation. The morphology of Fe₃O₄nanoparticles and Fe₃O₄/PSnanorods were characterized by TEM, SAED, FTIR and XRD. The results indicated that the Fe₃O₄nanoparticles were face-centered cubic structure with the average diameter in8nm. The magneticperformance was tested by vibrating-sample magnetometry （VSM）, the result showed that Fe₃O₄nanoparticles were superparamagnetic; the saturation magnetization reached75.023emu/g. Afterpolymerization of styrene under the simultaneous ultrasound and microwave radiation, the novelFe₃O₄/PS nanorods were synthesized and characterized by TEM, SAED, FTIR and XRD, theresults indicated that the Fe₃O₄/PS nanorods were well dispersed with average diameter between150nm to250nm. The VSM showed that saturation magnetization reached46.449emu/g. TGAexperiment showed that the content of Fe₃O₄reached58.4%, which was in accordance with VSMexamination.（3） Synthesis of Fe₃O₄/SiO₂magnetic microcapsules in reverse emulsionFe₃O₄/SiO₂magnetic microcapsules were synthesized through preparation of oleic acidmodified Fe₃O₄nanoparticles using coprecipitation, and then reacted with TEOS in the emulsion.The size and morphology of oleic acid modified Fe₃O₄nanoparticles and Fe₃O₄/SiO₂magneticmicrocapsules were characterized by TEM, SAED, FTIR and XRD, the magnetic properties weremeasured by VSM. The results indicated that Fe₃O₄nanoparticles were well dispersed withaverage diameter in13nm. This oleic acid modified Fe₃O₄nanoparticles were alsosuperparamagnetic. The saturation magnetization reached69.402emu/g. Fe₃O₄/SiO₂magneticmicrocapsules were hollow near-spherical morphology and possessed magnetic response withaverage diameter in5μm, average wall thickness of about2μm. In addition, to study the formingmechanism, PVP modified Fe₃O₄nanoparticles were employed as the raw material in stead ofoleic acid modified Fe₃O₄nanoparticles. With the same synthetic condition, magnetic solidmicrospheres were obtained with the diameter in4μm. According to the TEM, magnetic particlesas nuclear, heterogeneous nucleation and growth of SiO₂were occurred on the surface of thenuclear phase. This phenomenon further explained that the oleic acid modified Fe₃O₄magnetic particles and the SiO₂produced by the hydrolysis of TESO combined in the oil-water interface insitu synthesis of composite hollow microspheres.