Water soluble carbon nanoparticles: Hydrothermal synthesis and excellent photoluminescence properties

► Water soluble carbon nanoparticles (CNPs) were prepared from carbohydrates. ► Water soluble CNPs possess visible, up-conversion and NIR PL properties. ► NIR PL of the CNPs can also be observed by NIR excitation. ► Water soluble CNPs have potential applications in bio-imaging.