Colorful Organic Nanocolloids

Nanosized organic colloidal particles can fluoresce in a wide range of wavelengths in a manner reminiscent of inorganic quantum dots by controlling the aggregation of dye molecules inside the colloids, according to scientists at the Naval Research Laboratory, in Washington, D.C. (ACS Nano, DOI: 10.1021/nn9007498). These novel fluorescent nanoparticles and the wealth of functionalized derivatives that potentially can be made from them may find use in a host of fluorescence imaging and biological-labeling applications. Christopher M. Spillmann, Jawad Naciri, Banahalli R. Ratna, and coworkers formed the colloidal particles by reacting a polymerizable organic compound that exhibits a liquid-crystalline phase with a diimide perylene chromophore. By adjusting the ratio of the organic components, the research team controlled the number of dye molecules confined in the liquid crystals. In that way, the researchers caused the dye molecules to assemble into dimers, trimers, and larger aggregations, which led to increasingly larger red shifts in the colloids’ emission spectra. The colloidal particles, which have a long shelf life, can be prepared from other perylene derivatives, thereby extending the range of colors available from organic colloids, the researchers say.