Ao Xia,Yuan Gao,Jing Zhou,Chunyan Li,Tianshe Yang,Dongmei Wu,Limin Wu,Fuyou Li
New core–shell structured NaYF 4 :Yb 3+ ,Tm 3+ @Fe x O y nanocrystals , with 20 nm Yb 3+ ,Tm 3+ -co-doped NaYF 4 nanocrystals as a core and 5 nm Fe x O y nanocrystals as a shell, have been synthesized and characterized by TEM and XRD analysis . These core–shell nanocrystals exhibit excellent near-infrared upconversion luminescence (UCL) emission at 800 nm under excitation by a continuous-wave 980 nm laser and superparamagnetic properties with a saturation magnetization (Ms) of ∼12 emu/g. Water-soluble nanocrystals were obtained by surface ligand exchange of oleic acid-coated precursor nanocrystals, and their internalization within living cells has been investigated by laser scanning UCL microscopy. Furthermore, the obtained core–shell nanocrystals have been applied in dual-modality T 2 -enhanced magnetic resonance (MR) and UCL imaging in vivo of the lymphatic system. Moreover, the toxicity of NaYF 4 :Yb 3+ ,Tm 3+ @Fe x O y nanocrystals has also been evaluated by MTT assay, IC50 values, and histological analysis of lymphatic node sections.
A series of NaYF4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+ nanoparticles doped with Tm3+ and Er3+ were successfully prepared by the solvothermal method. Under 980 nm laser excitation, intense upconversion emission peaks of Tm3+ and Er3+ were observed for all samples. By doping Tm3+ and Er3+ with core–shell partitioning, not only a significant increase in fluorescence intensity could be achieved, but also simultaneous temperature measurements on multiple thermocouple energy levels could be realised. In addition, the temperature sensing performance of different thermocouple energy levels was also investigated, and it was found that the 3F3 → 3H6 and 1G4 → 3F4 thermocouple energy level pairs of Tm3+ were the best, with maximum absolute sensitivity and maximum relative sensitivity of up to 0.0250 K−1 and 2.155% K−1 respectively, higher than the sensitivity of other thermocouple energy levels. It has a temperature resolution of less than 0.0139 K, which is lower than that of most materials available today. By using this material as a probe to build a fiber optic temperature sensor platform, it was found to have reliable temperature measurement performance.
Hong-Qi Chen,Fei Yuan,Shao-Zhen Wang,Juan Xu,Yi-Yan Zhang,Lun Wang
A new luminescence resonant energy transfer (LRET) system has been designed that utilizes near-infrared (NIR)-to-NIR upconversion lanthanide nanophosphors (UCNPs) as the donor, and Au nanorods (Au NRs) as the acceptor. The UCNPs were excited by a near-infrared (980 nm) wavelength and also emitted at a near-infrared wavelength (804 nm) using an inexpensive infrared continuous wave laser diode. The Au NRs showed a high absorption band around 806 nm, which provided large spectral overlap between the donor and the acceptor. Hg2+ ions were added to an aqueous solution containing the UCNPs and Au NRs that were modified with a Hg2+ aptamer. Then, a sandwich-type LRET system was developed for the detection of Hg2+ ions that had high sensitivity and selectivity in the NIR region. The method was successfully applied to the sensing of Hg2+ ions in water and human serum samples.
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