The electrogenerated chemiluminescence of highly fluorescent organic chromophores and nanoparticles
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Electrogenerated chemiluminescence (ECL) of new, highly fluorescent molecules was studied. Six novel, highly fluorescent, green emitters were synthesized by incorporating an acceptor group like 2,1,3-Benzothiadiazole between different donor groups. The structural effects on the electrochemical, spectroscopic, and ECL behavior are shown in detail. Stable electrochemistry and high PL quantum yield were observed. Most of the ECL was visible by the naked eye. Well-known, fluorescent, polyaromatic hydrocarbons (PAH), like 9,10-diphenylanthracene derivatives, pyrene, and anthracene were incorporated between two bulky fluorene derivative groups. The fluorene substitutions block the active positions of the PAH cores, permitting the formation of stable radical ions upon electrochemical oxidation or reduction. Such a tailoring led to increase electrochemical reversibility and tuning of the ECL wavelength. Fluorene-based DPA (FDF) is characterized by a highly efficient and stable blue-cyan color. Another interesting type of molecules was star-shaped structures. The effects of structure on the electrochemistry and spectroscopy of a series of star-shaped, rigid molecules was examined. T1-T4 is composed of oligofluorene arms with truxene as a central core basically there were weak donor and weak acceptors. The ECL quantum efficiency was near 80% for the long-arm T4. One of the interesting goals in ECL is to find ECL emitters in aqueous media. Organic nanoparticles (ONPs) were chosen to achieve this goal. An organic nanoparticle (ONPs) is still challenging area in nanoscience. The key factor of such a challenge comes from the difficulty to control the size and shape of the prepared nanoparticles. ONPs of common hydrocarbon ECL emitters like rubrene and 9,10-diphenylanthracene (DPA) were prepared in aqueous solution using a reprecipitation method. ECL of rubrene NPs was observed when tripropylamine (TPrA) was used as a coreactant, and weaker ECL of DPA NPs was observed when the oxalate ion was used as a coreactant. The ECL of ONPs in aqueous media may open a new field in ECL, allowing the exploration of more phenomena in organic nanoscience. Organic nanoparticle ECL (especially if one able to make small size to be diffused easily) has potential application as a tag for the analysis of biologically interesting molecules.