Surface plasma enhanced fluorescence of CdSe quantum dots induced by laser on a grating surface
Li Xianji1, Bai Zhongchen2, Peng Man1, Shang Ye1, Qin Shuijie2     
1. College of Big Data and Information Engineering, Guizhou University, Guiyang, Guizhou 550025, China;
2. Guizhou Provincial Key Lab for Photoelectron Technology and Application, Guizhou University, Guiyang, Guizhou 550025, China

Overview: In recent years, the fluorescence technology has been greatly developed, but in practical applications, the sensitivity of the existing fluorescence detection technology is not satisfactory. Semiconductor quantum dots can exhibit higher luminous efficiency and stronger brightness compared to conventional fluorescent dyes, and their emitted light wavelengths can cover almost the entire visible light region, thus, it has been widely used in bio-detection, biomarker and optoelectronic device development. However, the commonly used quantum dots tend to have low fluorescence emission intensity, and the fluorescence stability needs to be further improved, which greatly limits its application. Therefore, the technology based on surface plasmon enhanced quantum dots fluorescence has become a new method for reducing fluorescence noise and improving sensitivity, and it has developed rapidly for this reason.

In the 1970s, Drexhage discovered the phenomenon of surface-enhanced fluorescence, but until the end of the 20th century, Lakowicz and his colleagues experimentally studied the effect of metal nanostructures on enhancing fluorescence, and made great contributions to the mechanism and application of surface-enhanced fluorescence, it begun to attract people's attention. And today, surface-enhanced fluorescence technology based on nanostructures has been widely used in the fields of DNA nondestructive testing, biosensing analysis, and single molecule detection. In recent years, research on the use of various metal nanostructures to enhance quantum dot fluorescence has also made a great progress. However, the mechanism of interaction between metal nanostructures and quantum dots is still not unified, and the control of coupling ligands between quantum dots and nanostructures is still one of the hot issues in current scientific research. In this paper, a nanograting structure was prepared on gold film surface of silicon fund by AFM force etching method, and CdSe quantum dots with organic molecular ligands were attached to the surface of nanograting by self-assembly technique. A multilayers film structure of nanograting/CdSe quantum dots were prepared. The fluorescence spectrum of the CdSe quantum dots was measured by adjusting the picosecond laser (with 532 nm excitation wavelengths) power on a micro-Raman measuring platform. The results showed that the structure of the gold nanograting and CdSe QDs could greatly enhance the far-field fluorescence of CdSe QDs, the maximum fluorescence intensity was up to 7.80 times, and it had been saturated rapidly at the point of reaching the maximum intensity. The results of this study could be widely used in fields of the optoelectronic devices, biomedical detection.

Supported National Natural Science Foundation of China (61741505), Science and Technology Support Project by Guizhou Province (QKHZ[2017]2887), Central Guidance for Local Science and Technology Development Projects (QKZYD[2017]4004), and Talent Team Project of Guizhou Province ([2018]5616)