| Low-dimensional nanomaterials have attracted much attention in research due to their unique properties in optics,electricity and mechanics.It is a major challenge for scientists to effectively control the morphology and size of nanomaterials.The same kind of nanomaterials will demonstrate distinct properties which are directly caused by their differences in morphology and size.Thus,for different nanomaterials,seeking an appropriate mass production synthesis method which could be easily implemented has been one of the focus in nanotechnology research.Hydrothermal method has been a general synthesis method of nanomaterials because of its low operational difficulty,simple reaction equipment,mild synthesis conditions and stable preparation system.In this paper,several kinds of carbon quantum dots with different sizes and Zn Se nanomaterials with different morphologies have been synthesized successfully via hydrothermal method under different reaction conditions.The morphologies and sizes of these two kinds of nanomaterials were effectively controlled.The nanostructures and properties of samples were characterized by X-ray diffraction?XRD?,Raman spectrometer,transmission electron microscopy?TEM?,X-ray energy dispersive spectrometer?EDS?,scanning electron microscope?SEM?,field emission tester and fluorescence spectrometer.The major findings are as follows.?1?Glucose and PEG-200 were used as carbon source and surface modifier respectively.Carbon quantum dots of different sizes were obtained with different PH conditions and different reaction time.In the experiment,the amount of surface modifier,reaction time and PH condition had a great impact on the size of carbon quantum dots.First when the amount of the surface modifier was too small,the carbon quantum dots were easy to polymerize.When the concentration of the modifier reached the critical micelle concentration,quantum dots of 2.5-3 nm are synthesized with wide excitation band and well fluorescence property.While when the concentration of the modifier is too high,the quantum dot is difficult to synthesize.Furthermore,the increase in reaction time led to the direct increase in the size of carbon dots.Finally,under the reaction condition of strong acid or alkali,the synthesized carbon dots were of moderate size and stable fluorescence.In contrast,the size of quantum dots synthesized in the reaction solution of PH = 7 was 10 nm,and the fluorescent property was not ideal.?2?Three kinds of Zn Se nanomaterials with different morphologies were synthesized by changing the dosage of diethanolamine.Grass-like Zn Se nanostructures were formed with 3ml diethanolamine solution.The average length of grass is about 4?m.By increasing the amounts of diethanolamine to 5ml,we synthesized the needle-like Zn Se nanostructures,and the average length of the needle is about 6.5?m.After increasing the amounts of diethanolamine to 7ml,the chrysanthemum-like Zn Se nanostructures were prepared.All the as-synthesized samples are of cubic Zn Se structure.Through the field emission test,we found that these three samples all showed good field emission properties.Specifically,the chrysanthemum-like Zn Se nanostructures had the lowest turn-on field(3.4V?m-1)and the highest field enhancement factor?4328?compared to the other as-synthesized samples,indicating that chrysanthemum-like Zn Se nanomaterials are the promising materials in FE application.The findings showed that the sizes and morphologies of carbon quantum dots and Zn Se nanomaterials can be controlled effectively by changing the reaction conditions during the hydrothermal preparation process,and the as-synthesized samples exhibited excellent performance in field of optics and field emission. |
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