Thomas Elizabeth Mariam, Cortes Cristian L, Paul Livin, Gray Stephen K, Thomas K George
School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Vithura, Thiruvananthapuram, 695 551, India.
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Phys Chem Chem Phys. 2022 Jul 21;24(28):17250-17262. doi: 10.1039/d2cp01681h.
The brightness of an emitter can be enhanced by metal-enhanced fluorescence, wherein the excitonic dipole couples with the electromagnetic field of the surface plasmon. Herein, we experimentally map the landscape of photoluminescence enhancement (EF) of emitters in a plasmonic field as a function of the emitter-emitter separation, , and the emitter-plasmon distance, . We use Au nanoparticles overcoated with inert spacers as plasmonic systems and CdSe/ZnS quantum dots (QDs) as an emitter bearing opposite surface charges. The and are varied by changing the spacer thickness and number density of QDs on the plasmonic surface, respectively. The electrostatic binding of emitters on the plasmonic surface and their number density are established by following the variation of zeta-potential. EF is high, when is short and is large; nevertheless, it decreases when the emitter-emitter interaction dominates due to plasmon assisted nonradiative processes. In the absence of a plasmonic field, the enhancement observed is attributed to environmental effects and is independent of , confirming the role of the electric field. Indeed, the distance dependence of EF closely follows the decay of the plasmonic field upon dilution of the emitter concentration on nanoparticles' surface ( = 18 nm). The QD-plasmon system is visualized in the framework of the Thomson problem, and classical electrodynamics calculations give the trends in and dependence of the photoluminescence. Being the first report on the simultaneous dependence of and on plasmon-enhanced photoluminescence, the results presented herein will open newer opportunities in the design of hybrid systems with a high brightness.
发射体的亮度可通过金属增强荧光来提高，其中激子偶极子与表面等离子体的电磁场耦合。在此，我们通过实验绘制了等离子体场中发射体的光致发光增强（EF）情况，它是发射体 - 发射体间距(r_{ee})和发射体 - 等离子体距离(r_{ep})的函数。我们使用涂覆有惰性间隔层的金纳米颗粒作为等离子体系统，以及CdSe/ZnS量子点（QD）作为带有相反表面电荷的发射体。通过分别改变间隔层厚度和等离子体表面上量子点的数密度来改变(r_{ee})和(r_{ep})。通过跟踪zeta电位的变化来确定发射体在等离子体表面上的静电结合及其数密度。当(r_{ee})短而(r_{ep})大时，EF较高；然而，当由于等离子体辅助的非辐射过程导致发射体 - 发射体相互作用占主导时，EF会降低。在没有等离子体场的情况下，观察到的增强归因于环境效应，并且与(r_{ee})无关，这证实了电场的作用。实际上，EF的距离依赖性紧密跟随纳米颗粒表面发射体浓度稀释时等离子体场的衰减（(r_{ep}=18)nm）。量子点 - 等离子体系统在汤姆逊问题的框架内可视化，经典电动力学计算给出了光致发光的(r_{ee})和(r_{ep})依赖性趋势。作为关于(r_{ee})和(r_{ep})对等离子体增强光致发光的同时依赖性的首次报道，本文给出的结果将为具有高亮度的混合系统设计带来新的机遇。
