Dielectric Dependence of Single-Molecule Photoluminescence Intermittency: Nile Red in Poly(vinylidene fluoride)

Abstract

The dependence of single-molecule photoluminescence intermittency (PI) or “blinking” on the local dielectric constant (ε) is examined for nile red (NR) in thin films of poly(vinylidene fluoride) (PVDF). In previous studies, variation of the local dielectric constant was accomplished by studying luminophores in chemically and structurally different hosts. In contrast, the NR/PVDF guest–host pair allows for the investigation of PI as a function of ε while keeping the chemical composition of both the luminophore and host unchanged. The solvatochromic properties of NR are used to measure the local ε, while fluctuations in NR emission intensity over time provide a measure of the PI. PVDF is an ideal host for this study because it provides submicron-sized dielectric domains that vary from nonpolar (ε ≈ 2) to very polar (ε ≈ 70). The results presented here demonstrate that the local dielectric environment can have a pronounced effect on PI. We find that the NR emissive events increase 5-fold with an increase in ε from 2.2 to 74. A complex dependence on ε is also observed for NR nonemissive event durations, initially increasing as ε increases from 2.2 to 3.4 but decreasing in duration with further increase in ε. The variation in emissive event durations with ε is reproduced using a photoinduced electron-transfer model involving electron transfer from NR to PVDF. In addition, an increase in NR photostability with an increase in ε is observed, suggesting that the dielectric environment plays an important role in defining the photostability of NR in PVDF.

Single-Particle Photoluminescence Spectra, Blinking, and Delayed Luminescence of Colloidal CuInS2 Nanocrystals

“…The blinking data were binned at 1.6 ms for determination of "off" statistics by a Bayesian detection method. 42 The dashed line is a guide to the eye. All data were collected at room temperature.…”

Photoluminescence Blinking and Reversible Electron Trapping in Copper-Doped CdSe Nanocrystals

“…28 This method involves computing a cumulative distribution function (CDF) for each data set and then using the Komlogorov−Smirnov (KS) test to determine the "goodness of fit" between the two functions. CDFs are computed directly from the blinking data using eq 1, 29 where N is the number of events, and t i is an event duration smaller than time t, with no additional manipulation of the data:…”

Effect of molecular side groups and local nanoenvironment on photodegradation and its reversibility

“…3 However, understanding of energy and charge transfer processes between the photoexcited molecule and other molecules in the surrounding environment during the molecule degradation and recovery is difficult due to complexity of the nanoscale environment. [8][9][10][11] To aid in the interpretation of the data, Monte Carlo simulations have been utilized to model fluorescence time trajectories that are affected by these processes. [12][13][14][15] In particular, we seek to further refine the model and to determine the accuracy of the single molecule analysis used in experimental data processing.…”