Fluorescence Detection\nof Tetraphenylporphyrin Isolated\non the Au(111) Electrode Enabled by Tripodal Molecules

Fluorescence\nof molecules on metal substrates has attracted much\nattention because of its relevance to various optical devices, such\nas light-emitting diodes, sensors, and solar cells. However, the fluorescence\nmeasurement near the metal substrates is challenging due to the rapid\nquenching of the excited state of the molecules. In this study, fluorescence\nof tetraphenylporphyrin (TPP) on Au(111) substrates was successfully\nmeasured by fabricating a mixed self-assembled monolayer (SAM) of\nthe tripodal molecules with and without TPP dye. The rigid tripodal\nmolecules suppressed quenching, prevented structural changes, and\nreduced interactions between TPP moieties. These features made it\npossible to measure the fluorescence of TPP molecules isolated and\ndispersed on Au(111) in a uniform and well-defined structure. Through\nexcitation spectra acquired by sweeping the excitation wavelength,\ninformation about TPP absorption was also obtained. In addition, these\nmeasurements were possible under potential control in an electrochemical\nenvironment due to the stability of the SAMs. Thus, we demonstrated\nthat the system based on tripodal molecules can serve as a platform\nfor measuring the fluorescence and absorption of molecules on metal\nsubstrates in the atmospheric and electrochemical environments in\nwhich various optical devices operate.