The photophysical and nonlinear optical properties of water soluble chromophore-functionalised tris-dipicolinate complexes [LnL3]3- (Ln = Yb and Nd) were thoroughly studied and reveals that only the Yb(III) luminescence could be sensitized by a two-photon excitation process. The stability of the complex in water has been strongly enhanced by embedding in dispersible organosilicate nanoparticles. Finally, the spectroscopic properties of the [NBu4]3[YbL3] have been studied in solution and in the solid state. The high brightness of the NPs allowed to image them as single objects using our modified two-photon microscopy set-up in a NIR-to-NIR configuration.