Single-molecule studies of proton transfer in guest-host materials

Abstract

Although the promise of organic materials for a variety of photonic applications has been recognized for some time, the wide-spread use of these materials is limited by photochemical processes that result in irreversible material decomposition. In this talk, the use of single-molecule microscopy to investigate the photochemistry of organic molecules in guest-host systems is described. A new method for analyzing the photoluminescence intermittency (PI) or “blinking” exhibited by single emitters is presented. This method allows for a statistically robust method for analyzing PI data, and for determining if an external perturbation results in a significant modification of the blinking statistcs. This method is applied to the blinking exhibited by CdSe/CdS quantum dots (QDs) in poly(methyl methacrylate) and the rhodamine derivative violamine R (VR) isolated in single crystals of potassium acid phthalate (KAP). For the QDs our analysis demonstrates that the blinking statistics are not power-law distributed. For VR in KAP we find that deuterium substitution significantly alters the PI exhibited by VR consistent with proton-transfer contributing to PI.