量子点的近场激发荧光特性研究

A Study on the Fluorescence Characteristic of Quantum Dots by Near-field Laser Excitation

近场光学显微镜具有nm量级的空间分辨率,量子点(quantum dots,QDs)荧光探针具有激发谱宽、发射谱线窄、荧光强度高、抗光漂白和稳定性高等优点,两者结合用于生物大分子的成像探测和识别具有广泛的应用前景。用近场光学显微镜对链霉亲和素偶联的QDs进行近场荧光激发,并对其荧光发射特性和光稳定性进行研究,结果表明:近场光学显微镜nm量级的空间分辨率,可以同时观察到了QDs的单体、二聚体和三聚体;QDs的荧光发射强度高,近场荧光像对比度好,单量子点的荧光半高宽达到25nm;对一定入射波长的单色激发光,QDs的近场荧光强度随着激发功率密度的增加线性增加,并很快趋于稳定。与传统的荧光染料如异硫氰酸荧光素相比,QDs的稳定性非常好,在激发功率密度为300W/cm2的近场辐射下,量子点的荧光强度超过6h基本保持不变,其抗光漂白能力远远高于普通荧光染料。

The near-field exeitation fluorescence characteristic of quantum dots （QDs） streptavidin conjugate is studied by use of scanning near-field optical microscopy （SNOM）. Owing to the high imaging resolution of SNOM, as well as the high intensity and narrow emission spectra of QDs, the high contrast near-field fluorescence images were obtained, and the full width at half maximum（FWHM） of the single QDs is approximately 25 nm, meanwhile the single and assemble quantum dots were observed. For another, the photostablity and fluorescence intensity of QDs and that of a conventional organic fluorescence dye fluorescein isthiocyanate（FITC） were compared, it is founded ,fluorescence intensity of QDs were higher and than that of FITC. If the excitation intensity is 300 W/cm^2 , there isn＇t obvious fluorescence intensity change in QDs for more than 6 hours illumination, but fluorescence intensity of FITC rapidly faded for less than 1 hours illumination, it indicates that QD605 has higher photostablity than conventional organic fluorescence probe, and the combination of NSOM and QDs will have great potential in the imaging and detecting single biomolecule.