Bagra Bhawna, Zhang Wendi, Zeng Zheng, Mabe Taylor, Wei Jianjun
Department of Nanoscience, Joint School of Nanoscience and Nanoengineering , University of North Carolina at Greensboro , Greensboro , North Carolina 27401 , United States.
Langmuir. 2019 Jul 9;35(27):8903-8909. doi: 10.1021/acs.langmuir.9b00448. Epub 2019 Jun 27.
Carbon nanodots (CNDs) are featured with a wide range of light absorption and excitation-dependent fluorescence. The emission enhancement of CNDs is of great interest for the development of nanophotonics. Although the phenomenon of plasmon-enhanced fluorescence for quantum dots and molecular dyes has been well investigated, rarely has it been reported for CNDs. In this work, a series of plasmonic nanoslit designs were fabricated and utilized for immobilization of CNDs in nanoslits and examination of the best match for plasmonic fluorescence enhancement of CNDs. In concert, to better understand the plasmonic effect on the enhancement, the surface optical field is measured with or without CND immobilization using a hyperspectral imaging system as a comparison, and a semianalytical model is conducted for a quantitative analysis of surface plasmon generation under the plane-wave illumination. Both the fluorescence and surface reflection light intensity enhancement are demonstrated as a function of nanoslit width and are maximized at the 100 nm nanoslit width. The analysis of surface plasmon-exciton coupling of CNDs in the nanoslit area suggests that the enhancement is primarily due to plasmonic light trapping for increased electromagnetic field and plasmon-induced resonance energy transfer. This study suggests that incorporating CNDs in the plasmonic nanoslits may provide a largely enhanced CND-based photoemission system for optical applications.
碳纳米点（CNDs）具有广泛的光吸收和激发依赖型荧光特性。碳纳米点的发射增强对于纳米光子学的发展具有重要意义。尽管量子点和分子染料的等离子体增强荧光现象已得到充分研究，但关于碳纳米点的此类报道却很少。在这项工作中，制备了一系列等离子体纳米狭缝结构，并用于将碳纳米点固定在纳米狭缝中，以及研究碳纳米点等离子体荧光增强的最佳匹配情况。同时，为了更好地理解等离子体对增强效果的影响，使用高光谱成像系统测量有无碳纳米点固定时的表面光场进行比较，并建立了一个半解析模型，用于定量分析平面波照明下表面等离子体的产生。荧光和表面反射光强度增强均表现为纳米狭缝宽度的函数，并在100 nm的纳米狭缝宽度处达到最大值。对纳米狭缝区域内碳纳米点的表面等离子体 - 激子耦合分析表明，增强主要归因于等离子体光捕获导致的电磁场增加以及等离子体诱导的共振能量转移。这项研究表明，将碳纳米点纳入等离子体纳米狭缝中，可能为光学应用提供一个大幅增强的基于碳纳米点的光发射系统。
