Synthesis, surface modification, and photophysical studies of Ln sub(2)O sub(2)S:Ln super(') super(3+) (Ln=Gd, Tb, Eu; Ln'=Tb and/ or Eu) nanoparticles for luminescence bioimaging

It has been demonstrated that by using doping and co-doping strategies the lifetimes as well as luminescence intensities of the doping species in the lanthanide oxysulfide nanoparticles (NPs) Ln sub(2)O sub(2)S:Ln' super(3+) (Ln=Gd, Tb, Eu; Ln'=Tb, Eu, 1% and 5%) could be tuned. The lanthanide oxysulfide NPs, i.e., Gd sub(2)O sub(2)S, Tb sub(2)O sub(2)S and Gd sub(2)O sub(2)S:Tb super(3+)(5%) were synthesized as matrices and doped with Eu super(3+)(1% or 5%), by the thermal decomposition method and characterized by TEM, XRD, photoluminescence, cellular and in vivo animal imaging studies for potential luminescence bioimaging applications. Of these materials, Gd sub(2)O sub(2)S:Eu super(3+)(5%) NPs possess the highest photo-stability and strongest luminescent intensity at 625 nm with a lifetime 853 mu s in hexane. Surface modification of the Gd sub(2)O sub(2)S:Eu super(3+)(5%) NPs with mPEG-APTES to increase its aqueous solubility resulted in almost complete luminescence quenching. Calcination of the host Gd sub(2)O sub(2)S:Eu super(3+)(5%) NPs at 400 degree C to increase their crystallinity and maintained some of their luminescence properties in aqueous solution. Further surface modification of the Gd sub(2)O sub(2)S:Eu super(3+)(5%)-APTES NPs with mPEG and Alexa Fluor 660 allowed their effective cellular and in vivo animal luminescence imaging with low bio-toxicity. These novel imaging materials with tunable lifetimes would be potentially useful for luminescence bioimaging applications, particularly in the time-resolved, up-conversion, and/or multiplex modes.