NIR fluorescence quenching by OH acceptors in the Nd3+ doped KY3F10 nanoparticles synthesized by microwave-hydrothermal treatment

• Published in: Journal of alloys and compounds 2016-03, Vol.661, p.312-321
• Main Authors: Orlovskii, Yu.V., Vanetsev, A.S., Keevend, K., Kaldvee, K., Samsonova, E.V., Puust, L., del Rosal, B., Jaque, D., Ryabova, A.V., Baranchikov, A.E., Lange, S., Sildos, I., Kikas, J., Loschenov, V.B.
• Format: Article
• Language: English
• Subjects: Fluctuation kinetics; Fluorescence quenching; Microwave-hydrothermal synthesis; Nd3+: KY3F10 nanoparticles; Near IR fluorescence; OH acceptors
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2015.11.156

We performed site-selective spectroscopy and analyzed static (Direct Energy Transfer, DET) Förster kinetics of impurity quenching N(t) in the water-dispersible 0.1% Nd3+: KY3F10 nanoparticles (NPs) synthesized by microwave-hydrothermal treatment (MWHT) to determine the acceptor space dimension D and estimate the concentration of –OH acceptors. As a result we found two types of optical sites for Nd3+ ions and revealed that a moderate amount of –OH quenching acceptors is distributed in the volume of the nanoparticles, rather than on their surface. The result is similar to the one obtained for the previously studied water-dispersible the Nd3+: KYF4 and Nd3+: YPO4 NPs, and thus may be extended to all nanoparticles synthesized by water-based techniques. Therefore, all of the previously obtained results concerning the fluorescence quenching of such NPs should be reviewed in the light of the new data on the actual source of the quenching. Also, we compared quantitatively the near IR fluorescence quenching in the Nd3+: KY3F10 NPs with that in the Nd3+ doped KYF4 and YPO4 nanoparticles with close sizes and size distribution (all the nanoparticles were synthesized by MWHT). We found minimum fluorescence quenching and accordingly maximum fluorescence quantum yield for the Nd3+: KY3F10 nanocrystals, which is in agreement with the relative amount of –OH molecular groups in the volume of the NPs estimated from Förster kinetics and with the results of TG/DTG-DTA data analysis. The analysis of the fluorescence kinetics of the 1% Nd3+: KY3F10 NPs revealed the realization of the late fluctuation stage. The formation of the fluctuation stage confirmed the high concentration of the –OH acceptors in the volume of the NPs compared to the optically active Nd3+ ions. Furthermore, the analysis of the fluctuation stage confirmed the reduced –OH concentration in the Nd3+ doped KY3F10 NPs in comparison with the KYF4 and YPO4 NPs. This makes the Nd3+: KY3F10 NPs especially promising material for near IR imaging. •We prepared water-dispersible fluorescent Nd3+: KY3F10 nanoparticles (NPs) by MWHT.•We discovered the fluorescence quenching by –OH acceptors distributed in the NP volume.•We proposed the model describing the fluorescence quenching by –OH acceptors.•We compared fluorescence quantum yield in Nd3+ doped KY3F10, KYF4, and YPO4 NPs.•We found that the Nd3+: KY3F10 NPs has the highest fluorescence quantum yield.