Distortion of power law blinking with binning and thresholding

Abstract

Fluorescence intermittency is a random switching between emitting (on) and non-emitting (off) periods found for many single chromophores such as semiconductor quantum dots and organic molecules. The statistics of the duration of on- and off-periods are commonly determined by thresholding the emission time trace of a single chromophore and appear to be power law distributed. Here we test with the help of simulations if the experimentally determined power law distributions can actually reflect the underlying statistics. We find that with the experimentally limited time resolution real power law statistics with exponents α(on/off) ≳ 1.6, especially if α(on) ≠ α(off) would not be observed as such in the experimental data after binning and thresholding. Instead, a power law appearance could simply be obtained from the continuous distribution of intermediate intensity levels. This challenges much of the obtained data and the models describing the so-called power law blinking.

CdSe/CdS Dot‐in‐Rods Nanocrystals Fast Blinking Dynamics.

“…For Dt = 150 ms, we obtain power law exponents of 0.46 and 0.42 for the grey and bright states respectively with exponential cutoffs of 1.5 and 6.1 ms for the cumulative distributions. [26,27] In Figure 2b we present the same analysis with a larger bin time than in Figure 2a, Dt = 1 ms, and the same thresholds. Hence the values close to 0.5 [8] corresponds to 1 + m'1.5 often reported in the literature for the non-cumulative distributions.…”

Models of semiconductor quantum dots blinking based on the spectral diffusion

“…Nonetheless there are a number of the experimental observations which are not explained by the model: 1. The exponent value m of the ON and OFF time distribution functions is reported in the range from 1.2 to 2.0 [2], and it strongly depends on the threshold value [41][42][43]. Meanwhile, in the model, m is always equal to 3/2 regardless of the threshold.…”

Two-state theory of binned photon statistics for a large class of waiting time distributions and its application to quantum dot blinking

“…During the review process of the present paper a study was published along these lines using simulated trajectories with power law waiting times. 44 …”