A new class of fluorophores has been identified that can be imaged at the single-molecule level and offer additional beneficial properties such as a significant ground state dipole moment, moderate hyperpolarizability, and sensitivity to local rigidity. These molecules contain an amine donor and a dicyanodihydrofuran (DCDHF) acceptor linked by a conjugated unit (benzene, thiophene, alkene, styrene, etc.) and were originally designed to deliver both high polarizability anisotropy and dipole moment as nonlinear optical chromophores for photorefractive applications. Surprisingly, we have found that these molecules are also well-suited for single-molecule fluorescence imaging in polymers and other reasonably rigid environments. We report the bulk (ensemble) and single-molecule photophysical properties measured for six dyes in this new class of single-molecule reporters, with absorption maxima ranging from 486 to 614 nm.
Since the first observation of the photorefractive (PR) effect in polymers, extensive efforts have been directed toward understanding the physics of the PR process in these systems, as well as optimizing polymer composites and glasses for various applications. Despite remarkable progress both in elucidating the mechanisms and processes contributing to the PR effect and in designing organic materials with high gain and diffraction efficiency, simultaneously attaining high refractive index modulation, fast dynamics, and good thermal properties in one material remains a challenge. Monolithic glasses represent an attractive class of PR organic materials since they possess large nonlinearities and minimal inert volume, which enhances the performance without stability problems. In this paper, we present a complete study of monolithic glasses based on a promising new class of chromophores (containing 2-dicyanomethylen-3-cyano-5,5-dimethyl-2,5-dihydrofuran, abbreviated as DCDHF-derivatives). We describe thermal, photoconductive, orientational, and photorefractive properties of these materials in both red and near infrared wavelength regions. By studying the temperature dependence of various parameters, we analyze the factors that affect photorefractivity in DCDHF-based materials.
Derivatives of 2-dicyanomethylen-3-cyano-2,5-dihydrofuran (DCDHF) have been synthesized by different methods to be used as photorefractive (PR) chromophores. Structure modifications were performed on the donor, acceptor and conjugated π-system for improving properties such as glass formation. Structure-property relationships important for PR applications are discussed from the results of studies including UV-Vis, electrochemistry and DSC.
We seek to improve the performance of organic photorefractive (OPR) systems by implementing two different design philosophies. In one strategy polysiloxane-based charge transport polymers are used to explore the requirement of a low glass transition temperature. These polymers allow construction of low Tg composites without plasticizcer and additionally may have higher charge mobility than poly(n-vinyl carbazole).The other strategy entails the use of small-molecule organic glasses composed of covalently attached charge transport and non-linrar optical chromophore moieties. Both classes of materials are characterized by holographic, photoconductive, and ellipsometric methods.
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