Fluorescence and Raman Enhancement Effect Caused by a Chemical Mechanism in Metal-Tetraphenylporphyrin on 2D Layered Materials

Two-dimensional (2D) layered materials exhibiting a flat surface have been strong candidates for studies investigating both the fundamental Raman enhancement in these materials and their practical applications. Here, we explore the Raman and the fluorescence enhancement effects of metal-tetraphenylporphyrin (TPP) molecules on graphene and MoSe2. We attribute the enhancement behaviors to the charge transfer interaction between the 2D materials and the adsorbates. The enhancement factors for the two flat substrates are dissimilar due to the charge transfer ability resulting from the electronic structures. The charge transfer interaction can be explained by the adsorption probability based on Langmuir's model.