Homogenous, far-reaching tuning and highly emissive QD–silica core–shell nanocomposite synthesized via a delay photoactive procedure; their applications in two-photon imaging of human mesenchymal stem cells

In this article, we present the exploration of a facile synthetic tactic incorporating delay-photo-oxidation to recover the loss in emission frequently encountered after encapsulating quantum dots (QDs) inside a silica shell. This facile synthesis procedure reproducibly increases emissive intensity of QDs (core)–SiO₂ (shell) (60 nm) nanomaterials by >5 fold (QY from 3% to >15%). The resulting QDs (core)–SiO₂ proved to be a single quantum dot in single SiO₂, homogeneous and highly monodispered; their emissions have been successfully fine-tuned from visible to the near infrared region. We then demonstrate their power in biological imaging by labeling human mesenchymal stem cells under two-photon confocal microscopy. The results of low cytotoxicity, efficient labeling, and specific location nearby the nucleus characters of these nanoparticles should spark an intensive relevant research within a living system.