Article pubs.acs.org/JPCC
Amplification of Surface Plasmon Coupled Emission from Graphene− Ag Hybrid Films Pradyumna Mulpur,† Ramakrishna Podila,§ Kiran Lingam,§ Sai Krishna Vemula,† Sai Sathish Ramamurthy,‡ Venkataramaniah Kamisetti,† and Apparao M. Rao*,§,∥ †
Department of Physics, Nanoscience Division, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam 515134, India Department of Chemistry, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam 515134, India § Department of Physics and Astronomy and ∥COMSET, Clemson University, Clemson, South Carolina 29634, United States ‡
S Supporting Information *
ABSTRACT: Surface plasmon coupled emission (SPCE) is a novel analytical technique in which the isotropic emission of a fluorophore is combined with the surface plasmon resonance of a Ag (or Au) thin film to yield highly directional emission from the so-called plasmaphore and thus greatly increased sensitivity. Here we report a 40-fold amplification of rhodamine B (RhB) fluorophore when graphene is used as the spacer layer in a conventional Ag-based SPCE setup. In addition to protecting the Ag thin film from oxidation, the highly impermeable graphene facilitated π−π stacking interactions with the RhB molecules that resulted in an efficient radiated emission from the plasmaphore. In addition, we found that the plasmaphore emission was more sensitively dependent on the in-plane crystallinity (measured by coherence length La) of the graphene spacer layer than its thickness. This study describes the unique features of graphene as a spacer layer for SPCE-based analytical platforms and its potential applications in chem-bio sensing and detection.
1. INTRODUCTION An isotropic fluorescence emission from fluorophores in the vicinity of thin metal films can strongly interact with the surface plasmon modes of the metal leading to the generation of highly directional p-polarized and wavelength-resolved emission known as surface plasmon coupled emission (SPCE) or surface plasmon coupled luminescence (SPCL).1−3 Such a directed emission in SPCE has been widely utilized in producing sensitive SPCE-based sensors3−10 with an increased signal collection efficiency (which can exceed 50%) in comparison to fluorescence (which is an isotropic phenomenon with
