Other origins for the fluorescence modulation of single dye molecules in open-circuit and short-circuit devices

Abstract

Fluorescence intensity modulation of single Atto647N dye molecules in a short-circuit device and a defective device, caused by damaging an open-circuit device, is due to a variation in the excitation light focus as a result of the formation of an alternating electric current.

Field-Controlled Charge Separation in a Conductive Matrix at the Single-Molecule Level: Toward Controlling Single-Molecule Fluorescence Intermittency

“…In contrast, the fluorescence intensity of individual molecules with time is nearly always fluctuating, a phenomenon called blinking or fluorescence intermittency. 1 − 6 Hence, the fluorescence intensity of an individual molecule measured as a function of time alternates between the so-called on and off states over a wide range of time scales (from microseconds to milliseconds and longer). This blinking can be attributed to diverse processes like intersystem crossing to a nonemissive triplet state, 3 , 7 , 8 spectral diffusion, 9 , 10 conformational changes, 11 − 13 molecular reorientation, 14 , 15 and inter- or intra-molecular charge transfer.…”

“…The fluorescence of a bulk sample containing many fluorophores shows, in the absence of bleaching, a constant fluorescence intensity upon continuous illumination. In contrast, the fluorescence intensity of individual molecules with time is nearly always fluctuating, a phenomenon called blinking or fluorescence intermittency. − Hence, the fluorescence intensity of an individual molecule measured as a function of time alternates between the so-called on and off states over a wide range of time scales (from microseconds to milliseconds and longer). This blinking can be attributed to diverse processes like intersystem crossing to a nonemissive triplet state, ,, spectral diffusion, , conformational changes, − molecular reorientation, , and inter- or intra-molecular charge transfer. − Blinking has been observed for virtually any emitting material, including quantum dots, ,, conjugated polymers, − organic dyes, ,,, fluorescent proteins, − and recently also perovskite nanocrystals. − Whereas the shorter off times in the micro- and milli-second ranges are usually attributed to intersystem crossing to the triplet manifold, the longer off times are attributed to charge transfer (usually electrons, but eventually also proton transfer in the case of fluorescent proteins) from or to the surroundings. ,, It was noticed, first for quantum dots and later also for dyes, that the distribution of these on and off times for a single particle/molecule (or the average distributions of several single emitters) follows so-called inversed power laws, p τ ∼ τ –μ , that span time scales of several orders of magnitude. ,,, For the exponents, μ values between 1.5 and 2.2 are generally found, although larger values have also been reported .…”