Diketopyrrolopyrroles (DPPs) have recently attracted much interest as very bright and photostable red�emitting molecules. However, their tendency to form nonfluorescent aggregates in water through the aggregation�caused quenching (ACQ) effect is a major issue that limits their application under the microscope. Herein, two DPP molecules have been incorporated into the membrane of highly stable and water�soluble quatsomes (QS; nanovesicles composed of surfactants and sterols), which allow their nanostructuration in water and, at the same time, limits the ACQ effect. The obtained fluorescent organic nanoparticles showed superior structural homogeneity, along with long�term colloidal and optical stability. A thorough one� (1P) and two�photon (2P) fluorescence characterization revealed the promising photophysical features of these fluorescent nanovesicles, which showed a high 1P and 2P brightness. Finally, the fluorescent QSs were used for the in vitro bioimaging of Saos�2 osteosarcoma cell lines; this demonstrates their potential as nanomaterials for bioimaging applications.

We report a comprehensive THz, infrared and optical study of Nb-doped SrTiO₃ as well as dc conductivity and Hall effect measurements. Our THz spectra at 7 K show the presence of an unusually narrow (<2  meV) Drude peak. For all carrier concentrations the Drude spectral weight shows a factor of three mass enhancement relative to the effective mass in the local density approximation, whereas the spectral weight contained in the incoherent midinfrared response indicates that the mass enhancement is at least a factor two. We find no evidence of a particularly large electron-phonon coupling that would result in small polaron formation.