Development and Application of New Tools for Analyzing Single Molecule Photoluminescence Intermittency

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With this award, the Chemical Measurements and Imaging Program is supporting the research of Phillip J. Reid of the University of Washington to develop new computational analysis techniques to more fully understand how light is emitted by molecules in electronic optical devices. These systems are technologically important and find many uses in the telecommunications industry, but it is still not understood why, when they are continuously illuminated by light, the molecules in the device respond by giving off bursts of light, rather than a steady stream of emitted light. This blinking, also known as photoluminescence intermittency (PI), also appears to be strongly affected by the environment surrounding these molecules. The investigators are using mathematical methods to analyze the blinking patterns in order to understand both the origin of the blinking itself as well as how the environment around the molecules affects the blinking pattern. The new tools being developed for this analysis will be able to quantify changes in blinking induced by changes in the molecule's environment and will also be easier to implement. The work is producing analysis methods that are much faster than existing techniques. Thus, the research is having a broad impact on technology as well as science through the development of new tools that will be applicable to a wide range of measurements in many fields including photonics, materials science, electronics, and biology. The work is having a further broad impact on the training of the future generation of scientists by giving students involved in this research hands-on experience with advanced techniques.In this project, robust statistical tools for analyzing photoluminescence intermittency (PI, or more commonly "blinking") are being developed to more fully understand the variation between emissive and non-emissive states observed in single luminophores under continuous illumination. The work involves the study of light emitted by single molecules in complex systems, including polymer composites and organic photonic materials. The investigators are using these newly developed methods to measure the photostability of nonlinear optical materials and the impact of dielectric environment on the PI of chromophores in complex condensed phases. PI data collected from such systems often exhibit significant deviations from power law distributions, complicating the analysis of emissive event kinetics. The new tools are using advanced Bayesian statistical models to extend approaches for parsing PI traces into emissive and non-emissive events at rates roughly an order of magnitude faster than Change Point Detection, the current state of the art, via a code set that is easily implemented. The new tools also use cumulative distribution functionals and kernel density estimation to expand analysis of PI to allow for a variety of distribution functions (parametric and non-parametric) to be quantitatively compared to experimental data. This approach allows for a statistically robust evaluation of the effect of perturbation (temperature, isotopic substitution, etc.) on PI, advancing studies of photonic materials and providing an important tool for other researchers trying to connect photophysical processes to PI.