title: Synthesis of ZnS:Ag,Co water-soluble blue afterglow nanoparticles and application in photodynamic activation.
abstract: Silver and cobalt co-doped ZnS (ZnS:Ag,Co) water-soluble afterglow nanoparticles were synthesized using a wet chemistry method followed by aging at room temperature. The nanoparticles had a cubic zinc blende structure with average sizes of approximately 4 nm and emitted a blue fluorescence emission centered at 441 nm due to radiative transitions from surface defects to Ag(+) luminescent centers. Intense afterglow emission peaking at 475 nm from the obtained nanoparticles was observed and was red-shifted compared to the fluorescence emission peak. X-ray photoelectron spectroscopy revealed a large increase of O/S ratio, indicating a surface oxidation process during aging. The S vacancies produced accordingly may contribute to form more electron traps and enhance afterglow. The ZnS:Ag,Co afterglow nanoparticles have a very low dark-toxicity and are applied as a light source for photodynamic therapy activation by conjugating with protoporphyrin together. Our preliminary study has shown that the ZnS:Ag,Co afterglow nanoparticles can significantly reduce the x-ray dosage used in activation and thus may be a very promising candidate for future x-ray excited photodynamic therapy in deep cancer treatment.
authors.affiliation: Department of Physics, The University of Texas at Arlington, Arlington, TX 76019-0059, USA.
authors.forename: Lun
authors.initials: L
authors.lastname: Ma
authors.forename: Xiaoju
authors.initials: X
authors.lastname: Zou
authors.forename: Marius
authors.initials: M
authors.lastname: Hossu
authors.forename: Wei
authors.initials: W
authors.lastname: Chen