Due to the high demand for near infrared (NIR) optical nanoprobes, with emissions which are absorbed to a lesser extent by biological tissues, for diagnosing diseases (e.g. cancer) which occur under deep tissue, we present a one-pot synthesis of highly monodispersed (full width at half maximum: 70 nm) NIR core–shell type II CdTe–CdS quantum dots (QDs), encapsulated in a highly biocompatible polymer, for in vivo sentinel lymph node and tumour imaging.