Customized multiphotonics nanotools for bioapplications: soft organic nanodots as an eco-friendly alternative to quantum dots

Quantum dots have been shown to provide a particularly effective approach to bright nano-objects for bioimaging due to their unique optical properties, including their robust and size-dependent fluorescence. However these "hard" nanoparticles raised a number of questions related to toxicity, biocompatibility and/or environmental issues. In that context, we have developed a new class of "soft" fully organic alternative nanoparticles (i.e. organic nanodots). Our approach relies on the confinement of a large number of organic chromophores within spherical nano-objects of controlled size and structure, by embedding them within non-toxic and biocompatible dendrimeric architectures. This highly modular strategy yielded organic nanodots of different sizes, colors and nature (lipophilic and hydrophilic). In contrast with quantum dots (QDs), their emission color does not depend on their size, but only on the nature of their constituting chromophoric subunits and their relative arrangement. Several series of nanodots of few nanometers in diameter have been studied, exhibiting exceptional one and two-photon brightness and often outperforming the best quantum dots. Nanodots offer major promises for bio and nanophotonics.