【作者】 周建华；

【导师】 郑蓓蓉； 钟蓉；

【作者基本信息】 温州大学 ， 机械工程（专业学位）， 2020， 硕士

【摘要】 量子点（QDs）又被称为纳米晶（nanocarystal）,是近年来非常热门的新型半导体材料。量子点具有宽而连续的激发光谱、窄并对称的发射光谱、抗光漂白能力强象等一系列荧光特性,被广泛应用于发光二极管（LED）、量子点敏化太阳能电池（QDSSC）等领域。目前量子点领域研究的最多的材料有Cd Se、Cd Te、In P等,虽然对于这些材料的工艺开发已经较为成熟,应用也最为广泛。但是这类材料本身是含有剧毒的,限制了这类量子点的进一步的应用。ZnO量子点具有无毒无害、活体排斥性低等优点,可以有效规避传统量子点的缺陷。本论文采用液相中超声波辅助的化学方法合成了核壳结构的ZnO量子点,并对其结构和光学性能进行了表征分析。本文主要工作包括以下内容:（1）开发了一种溶质非完全溶解形式的量子点合成方法。在乙醇体系中以醋酸锌为锌源,在室温下合成ZnO量子点。详细研究了在不同条件下（反应时间、反应温度、反应物比例、稳定剂等）合成ZnO量子点的结构及其荧光特性。实验结果显示:当反应物摩尔比为1.2:1、温度在40℃、反应经历30min时制备的ZnO量子点性质最好。此时的量子点粒径均匀（平均粒径为4.8nm）、单分散程度高、结晶度好,同时荧光强度和量子产率也最高。在通过365nm紫外灯照射和CIE色度图对比发现,所制备的ZnO量子点发出柔和的荧光,具备应用于生物检测、照明等领域的应用潜力。由于尺寸和表面效应等综合影响,合成的量子点稳定性不好,放置一段时间后会发生团聚现象。（2）为了克服量子效应等带来的不良影响,开发一种超声辅助化学合成方法进行了核壳包覆实验。我们通过3-氨丙基三乙氧基硅烷（APTES）对ZnO实现表面修饰及硅烷化包覆,制备出核壳结构的ZnO/SiO₂量子点。通过改变反应条件,得到最优的数据。实验结果显示,得到的样品具有核壳结构,其整体的粒径为6nm左右。相对于纯ZnO量子点,核壳结构的量子点分散性得到较大提高。通过吸收光谱表征可知包覆后的ZnO量子点由于受到保护没有发生团聚长大,样品具有良好的稳定性。通过相转移将核壳量子点转移至水相中发现仍有强烈的荧光发射,无明显团聚现象。说明样品具有较好的水稳定性。根据荧光光谱表征可知核壳结构的ZnO量子点荧光强度获得了很大提高,同时绝对量子产率也增加了约17%。样品具有优异的光学特性。更多还原

【Abstract】 Quantum dots（QDs）,also known as nanocrystals,are very popular new semiconductor materials in recent years.QDs have a wide and continuous excitation spectrum,narrow and symmetric emission spectra,strong photoresistance and other fluorescent characteristics,and are widely used in light-emitting diodes（LEDs）and QD-sensitized solar cells（QDSSC）.At present,the most studied materials in the field of QDs are Cd Se,Cd Te,In P,etc.Although the process development for these materials is relatively mature,the most widely used.However,such materials themselves are highly toxic,which limits the further application of such QDs.ZnO QDs have the advantages of being non-toxic and harmless,and low living body rejection,which can effectively avoid the defects of traditional quantum dots.In this thesis,ZnO QDs with core-shell structure were synthesized by ultrasonic-assisted chemical method in liquid phase,and their structure and optical properties were characterized and analyzed.The main work of this article includes the following:（1）A quantum dot synthesis method with incompletely dissolved solutes was developed.ZnO QDs were synthesized at room temperature using zinc acetate as the zinc source in the ethanol system.The structure and fluorescence properties of ZnO QDs synthesized under different conditions（reaction time,reaction temperature,reactant ratio,stabilizer,etc.）were studied in detail.The experimental results show that the ZnO QDs prepared have the best properties when the molar ratio of the reactants is 1.2:1,the temperature is at 40°C,and the reaction takes 30minutes.At this time,the QDs have a uniform particle size（average particle size of 4.8 nm）,a high degree of monodispersity,and good crystallinity,and also have the highest fluorescence intensity and quantum yield.The comparison between 365nm UV lamp irradiation and CIE chromaticity diagram found that the prepared ZnO QDs emit soft fluorescence,which has the potential for application in the fields of biological detection and lighting.Due to the combined effects of size and surface effects,the stability of the synthesized quantum dots is not good,and agglomeration will occur after a period of time.（2）In order to overcome the adverse effects caused by quantum effects.an ultrasound-assisted chemical synthesis method was developed to carry out the core-shell coating experiment.We used3-aminopropyltriethoxysilane（APTES）to modify the surface of ZnO and coat it with silanization to prepare core-shell structured ZnO/SiO₂QDs.By changing the reaction conditions,the best data can be obtained.The experimental results show that the obtained sample has a core-shell structure,and the overall particle size is about 6 nm.Compared with pure ZnO QDs,the dispersion of quantum dots in the core-shell structure has been greatly improved.The absorption spectroscopy characterization shows that the coated ZnO QDs are protected from agglomeration and growth,and the sample has good stability.The core-shell quantum dots were transferred to the aqueous phase through phase transfer and it was found that there was still strong fluorescence emission without obvious agglomeration.It shows that the sample has good water stability.According to the fluorescence spectrum characterization,it can be seen that the fluorescence intensity of the core-shell structured ZnO QDs has been greatly improved,and the absolute quantum yield has also increased by about 17%.The sample has excellent optical properties.更多还原