(Invited) Lanthanides Fluorides Doped Nanocrystals for Biomedical Applications

Introducing to medicine and biology concept of optical markers in tremendous way has changed the recent status of these two important disciplines. This was mainly due to strong development in imaging techniques which recently allow us to investigate both static as well dynamic properties of living cells, their components and their interactions with external factors. Recently used molecular markers including organic dyes, fluorescent proteins or chelates containing lanthanide ions have several significant limitations. One of the alternatives for molecular markers are inorganic quantum dots (ie. CdSe, CdS) which are recently commonly used in many academic works. However, even if they are much better from physico-chemical point of view, from the application point of view at this moment they use is still questionable mainly because of their high risk of toxicity and difficulties in obtaining infrared excitation/emission. One of the solutions, combining advantages of both concepts, is to make nontoxic inorganic nanocrystals doped with lanthanide ions (RENCs).

In this work, we will present optical (photoluminescence (PL), PL excitation, PL decay, FTIR, Raman) and structural (XRD, HR-TEM) results obtained for NaYF₄ and NaGdF₄ nanocrystals doped with Eu, Er, Tm and Yb ions. Based on obtained results, we will discuss examples of ion-ion interaction like: cross-relaxation, energy migration or up-conversion [1, 2] and influence of these interactions on resultant emission properties of RENCs. Additionally, we will discuss the effect of the nanocrystals surface and their core-shell geometry on the excitation and emission properties of lanthanides in RENCs [1, 3]. Finally, we will discuss a few examples of potential application of RENCs in bio-medicine.

Acknowledgements

The authors would like to thank the Polish National Centre for Research and Development for their financial support under the LIDER project No. 014/L-2/10.

References

[1] A. Podhorodecki, M.Banski, A. Noculak, B. Sojka, G. Pawlik, J. Misiewicz, On the nature of carriers relaxation and ion-ion interactions in ultrasmall b-NaYF₄ nanocrystals-effect of the surface, Nanoscale 5 (2013) 429.

[2] A. Podhorodecki, M.Banski, J.Misiewicz, M. Afzaal, P. O Brien, D. Cha, X. Wang, The Multicolor light emitters based on energy exchange between Tb and Eu ions co-doped into ultrasmall b-NaYF₄ nanocrystals, J.Materials Chemistry 22 (2012) 5356.

[3] M. Banski, M. Afzaal, A. Podhorodecki, Jan Misiewicz, Paul O'Brien, Passivation of lanthanide surface sites in ultrasmall NaYF₄:Eu³⁺ nanocrystals, J. Nanoparticles Research 14 (2012) 1228.