摘要/Abstract

具有近红外II区荧光的Ag₂S量子点(QDs)因具有带隙窄、Stokes位移大及光稳定性好等优点而在生物成像领域具有广阔应用前景. 然而, 传统有机相合成的Ag₂S量子点水溶性与生物相容性较差, 而水相合成Ag₂S量子点的荧光又很难到近红外II区, 这严重制约了Ag₂S量子点的生物医学应用推广. 因此, 优化探究具有近红外II区荧光发射的Ag₂S基量子点的水相合成方法具有重要意义. 采用核掺杂ZnS、表面阳离子(Zn²⁺)改性以及调控表面配体制备出一系列Ag₂S基量子点, 发现核掺杂和表面阳离子改性均使Ag₂S基量子点的荧光呈现剂量依赖性蓝移; 而将表面配体由树枝状短链(Captopril)更换为长直链(11-巯基十一烷酸, MUA)时, Ag₂S基量子点的发射峰红移至1105 nm(近红外II区)且半峰宽更窄. 本研究发现, 相比核掺杂和表面阳离子改性, 优化表面配体更容易在水相中制备出具有近红外II区荧光的Ag₂S基量子点. 本工作为近红外荧光量子点的水相合成及优化提供了基础研究数据.
关键词: 近红外II区荧光, Ag₂S基量子点, 水相合成, 核掺杂, 表面阳离子改性, 优化表面配体
Growing numbers of quantum dots (QDs) have been applied in biological fluorescence imaging, especially those QDs with near-infrared-II fluorescence emission, avoiding the interference of autofluorescence of biological tissues, have broad application prospects in the field of fluorescence imaging. In particularly, Ag₂S quantum dots (Ag₂S QDs) have drew great attention of researchers in biological fluorescence imaging due to the near-infrared fluorescence emission, large Stokes shift, good light and chemical stability. However, the Ag₂S QDs synthesized in organic phase usually experienced poor water solubility and biocompatibility, while the fluorescence of the Ag₂S QDs synthesized in aqueous phase is difficult to reach the near-infrared-II region, which severely restricts the promotion of Ag₂S QDs in biological fluorescence imaging. Therefore, it is of great significance to optimize and explore the water-phase synthesis method of Ag₂S based quantum dots with near-infrared-II fluorescence emission. The goal of this work is to synthesize Ag₂S QDs with near-infrared-II region fluorescence emission by aqueous phase method. First, captopril modified Ag₂S QDs (Ag₂S@Cap QDs) were prepared in water, and its fluorescence emission peak lied in the near-infrared-II region at 1005 nm. Then a series of Zn:Ag₂S@Cap QDs were prepared in aqueous by introducing ZnS to the Ag₂S core. The results showed that the fluorescence emission peaks of Zn:Ag₂S@Cap QDs blue shifted in a core-doping ZnS-dose dependent manner. Next, a series of Ag₂S@Cap-Zn QDs were prepared in aqueous by introducing Zn²⁺ to the ligand-shell of Ag₂S QDs. The fluorescence emission peaks of these Ag₂S@Cap-Zn QDs also blue shifted in a Zn²⁺-dose dependent manner. Finally, Ag₂S@MUA QDs were prepared by replacing the shell ligand from Cap to 11-mercaptoundecanoic acid (MUA). The fluorescence emission peak of these Ag₂S@MUA QDs red shifted to 1105 nm, locating in the near-infrared-II region, and the width of the fluorescence curve at half-maximum height became narrower, implying better application prospect in biological fluorescence imaging. This work not only successfully prepared a kind of Ag₂S QDs with near-infrared-II fluorescence emission in aqueous phase, but also opened an avenue for the preparation and optimization of semiconductor QDs with near-infrared fluorescence.
Key words: near-infrared-Ⅱ fluorescence, Ag₂S QDs, aqueous synthesis, core-doping, cationic-modification, optimizing surface ligand


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