以谷胱甘肽和柠檬酸钠为配体, 通过水热法制备了水溶性AgInS2量子点.采用X射线衍射、透射电子显微镜、紫外-可见吸收光谱和光致发光光谱研究了阳离子浓度、配体添加量和pH值对AgInS2量子点物相、形貌以及荧光性能的影响.结果表明, 随着阳离子浓度的提高, AgInS2量子点的粒径逐渐增大, 导致其发光峰位由614.7 nm红移至675.6 nm.同时伴随发生了少量In3+取代Ag+反应, 造成量子点中Ag+含量略微下降, 形成的InAg缺陷作为量子点中激子的辐射复合通道, 有利于提高其荧光发射效率, 当阳离子浓度为0.7 mmol/L时, AgInS2量子点的荧光强度达到最大值.配体的添加可有效地钝化量子点的表面态, 有利于提高量子点的荧光性能, 在谷胱甘肽/Ag+=20、柠檬酸钠/In3+=7的条件下, AgInS2量子点的荧光强度达到最大值.当溶液的pH值调节为9时, 配体对量子点表面缺陷的钝化效果最佳, 最大量子产率达到10.1%, 而过高的pH值干扰了配体和量子点间的结合, 造成量子点表面形成大量的非辐射复合缺陷, 导致其量子产率出现下降.红外光谱分析结果表明谷胱甘肽和柠檬酸钠主要通过-SH、-NHR和-COO-与量子点配位.此外, 量子点表面带有大量的负电荷, 说明AgInS2量子点具有很好的分散性和优异的化学稳定性, 显示其在生物成像领域具有广阔的应用前景.

Water-soluble AgInS2 quantum dots were synthesized via hydrothermal method using L-glutathione and sodium citrate as ligands. The effects of cation concentration, addition amount of ligands and pH values on the phase, morphology and fluorescence properties of AgInS2 quantum dots were systematically studied by X-ray diffraction, transmission electron microscopy, UV-Vis absorption spectra and photoluminescence spectra, respectively. The results showed that the particle size of AgInS2 quantum dots increased with the increase of cation concentration, which caused a systematic red shift from 614.7 nm to 675.6 nm in the photoluminescence spectra. Meanwhile, the Ag+ content in quantum dots decreased slightly due to the substitution of Ag+ by In3+, and the resulted defect of InAg could be served as the radiation recombination channel of excitons in AgInS2 quantum dots, which was propitious to improve its fluorescence emission efficiency. The fluorescence intensity of AgInS2 quantum dots reached to the maximum with the cation concentration of 0.7 mmol/L. Moreover, the ligands can effectively passivate the surface states and improve fluorescence properties of quantum dots. The AgInS2 quantum dots showed the strongest emission with the glutathione/Ag+ ratio at 20, and the sodium citrate/In3+ ratio at 7. The maximum quantum yields of AgInS2 quantum dots reached 10.1% due to the pronounced passivating effect on surface defects by ligands when the pH value of the solution was adjusted to 9, however the high pH values interfered with the combination between ligands and quantum dots, which induced a large number of surface non-radiative recombination defects, leading to the decrease of quantum yields. The infrared spectrometry results showed that glutathione and sodium citrate were mainly coordinated with AgInS2 quantum dots by the -SH, -NHR and -COO- groups. In addition, the surface of quantum dots was negatively charged, which demonstrates that the AgInS2 quantum dots possess good dispersibility and excellent chemical stability, showing wide application prospects in the biological imaging fields.