Wang Yan, Zhang Feng, Du Zaifa, Fan Xinmin, Huang Xiaodong, Zhang Lujun, Li Sensen, Liu Zhaohong, Wang Chunyan
School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
Weifang Key Laboratory of Laser Technology and Application, Weifang University, Weifang 261061, China.
Nanomaterials (Basel). 2024 Sep 6;14(17):1451. doi: 10.3390/nano14171451.
Surface enhanced fluorescence (SEF) based on noble metal nanoparticles is an effective means to achieve high sensitivity in fluorescence detection. Currently, the physical mechanism behind enhanced fluorescence is not fully understood. This paper measures the fluorescence signals of Dihydroporphyrin f methyl ether (CPD4) under both single-photon and two-photon excitation based on submicrometer silver particles with rough morphologies, achieving enhancement factors of 34 and 45 times, respectively. On this basis, by combining the radiative field characteristics produced by the silver particles, a stimulated radiation model of molecules is established to elucidate the changes in the molecular photophysical process when influenced by silver particles. Moreover, the fluorescence lifetime of the molecules was measured, showing that the presence of silver particles induces an increase in the molecular radiative decay rate, causing the fluorescence lifetime to decay from 3.8 ns to 3 ns. The results indicate that the fluorescence enhancement primarily originates from the submicrometer silver particles' enhancement effect on the excitation light. Additionally, the fluorescence signal emitted by the molecules couples with the silver particles, causing the local surface plasmon resonances generated by the silver particles to also emit light signals of the same frequency. Under the combined effect, the fluorescence of the molecules is significantly enhanced. The findings provide a theoretical foundation for understanding the fluorescence enhancement mechanism of silver particles, adjusting the enhancement effect, and developing enhanced fluorescence detection devices based on submicrometer silver particles, holding significant practical importance.
基于贵金属纳米粒子的表面增强荧光（SEF）是在荧光检测中实现高灵敏度的有效手段。目前，增强荧光背后的物理机制尚未完全理解。本文基于具有粗糙形貌的亚微米银颗粒，测量了二氢卟吩f甲醚（CPD4）在单光子和双光子激发下的荧光信号，分别实现了34倍和45倍的增强因子。在此基础上，结合银颗粒产生的辐射场特性，建立了分子的受激辐射模型，以阐明分子光物理过程在受到银颗粒影响时的变化。此外，还测量了分子的荧光寿命，结果表明银颗粒的存在导致分子辐射衰变率增加，使荧光寿命从3.8 ns衰减到3 ns。结果表明，荧光增强主要源于亚微米银颗粒对激发光的增强作用。此外，分子发射的荧光信号与银颗粒耦合，导致银颗粒产生的局部表面等离子体共振也发射相同频率的光信号。在这种综合作用下，分子的荧光得到显著增强。这些发现为理解银颗粒的荧光增强机制、调节增强效果以及开发基于亚微米银颗粒的增强荧光检测装置提供了理论基础，具有重要的实际意义。
