This paper describes the synthesis of new upconverting luminescent nanoparticles that consist of YF_(3):Yb^(3+)/Er^(3+)functionalized with poly(acrylic acid)(PAA).Unlike the upconverting nanocrystals previously reported in the literature that emit visible(blue-green-red)upconversion fluorescence,these as-prepared nanoparticles emit strong near-infrared(NIR,831 nm)upconversion luminescence under 980 nm excitation.Scanning electron microscopy,transmission electron microscopy,and powder X-ray diffraction were used to characterize the size and composition of the luminescent nanocrystals.Their average diameter was about 50 nm.The presence of the PAA coating was confirmed by infrared spectroscopy.The particles are highly dispersible in aqueous solution due to the presence of carboxylate groups in the PAA coating.By carrying out the synthesis in the absence of PAA,YF_(3):Yb^(3+)/Er^(3+)nanorice materials were obtained.These nanorice particles are larger(~700 nm in length)than the PAA-functionalized nanoparticles and show strong typical visible red(668 nm),rather than NIR(831 nm),upconversion fluorescence.The new PAA-coated luminescent nanoparticles have the pottential be used in a variety of bioanalytical and medical assays involving luminescence detection and fluorescence imaging,especially in vivo fluorescence imaging,due to the deep penetration of NIR radiation.
A facile strategy using cheap and readily available precursors has been successfully developed for the synthesis of rare-earth doped hexagonal phase NaYF4 nanocrystals with uniform shape and small particle size as well as strong photoluminescence. Due to their optical properties and good biocornpatibility, these multicolor nanocrystals were successfully used as a bio-tag for cancer cell imaging. This novel synthetic method should also be capable of extension to the synthesis of other fluoride nanocrystals such as YF3 and LaF3.
Mingliang Deng Yingxin Ma Sheng Huang Gaofei Hu Leyu Wang
