银纳米颗粒对纳米金刚石的拉曼及荧光增强特性研究

Effects of silver nanoparticles on Raman spectrum and fluorescence enhancement of nano-diamond

纳米金刚石因其优异的光学特性成为当今纳米科学研究中的一个热点.利用等离激元效应提高nitrogenvacancy(NV)色心的荧光和拉曼散射强度,进而可以提高这类传感器的灵敏度.本文主要将纳米金刚石与Ag纳米颗粒结合,利用金属纳米颗粒表面的等离子体共振效应,使NV色心的荧光和拉曼强度得到增强.同时研究了Ag纳米颗粒的质量浓度对拉曼与荧光光谱强度的影响,并进一步研究了相应的荧光辐射跃迁速率与量子效率,对荧光的增强机制进行了探究.

The nano-diamond has been a hot topic in the field of nano-science and nanotechnology for its optical properties.Much effort has been devoted to improving the fluorescence and Raman scattering intensity of nitrogen-vacancy（NV）center in nano-diamond by using plasmon resonance effect in sensing area. A combination of Ag nanoparticle and diamond can not only take advantage of the stability and biocompatibility of diamond, but also enhance the local electric field around NV center through the Ag nanoparticles, thereby speeding up the radiation of the fluorescent near the surface of the substrate, improving the strength and stability of the fluorescence, and greatly broadening the application areas of Raman spectroscopy. In this paper, we mix the nano-diamonds with Ag nanoparticles to improve the fluorescence and Raman scattering intensity on the basis of the localized surface plasmon resonance effect. The influences of Ag mass concentration on the Raman spectrum and fluorescence intensity are investigated. The results show that when the concentration of nano-Ag nanoparticles reaches up to 5 wt%, the light intensity becomes saturated,but the concentration further increases up to a value more than 7 wt% the light intensity begins to decline. Then the corresponding radiative transition rate and the fluorescence quantum efficiency are investigated, and based on these researches, influences and mechanism of surface plasmon resonance（SPR） enhancement are discussed thoroughly. We deduced that the fluorescence enhancement is mainly due to the enhanced surface plasmon field caused by transfer of surface plasmon resonance energy and the energy transfer between surface plasmon and excited state of NV centers.When the concentration of Ag nanoparticles reaches an appropriate value, a suitable distance between metal nanoparticles and diamond is obtained, thereby ensuring the strong local electric field forming on the metal surface, accelerating the emitting photons of diamond in the excited state, and also suppressing the transfer of non-radiative energy, eventually leading to the increase of diamond fluorescence emission intensity.