Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals

Luminescent nanocrystals (NCs) activated by lanthanide ions (Ln 3+ ) have been the object of intense research in recent years as a direct consequence of their unique properties (Grzyb and Lis 2011 ; Grzyb et al. 2012a , b ; Wang et al. 2006a , 2010 , 2011a ; Wiglusz et al. 2009 ; Yan and Yan 2008 ; Yang et al. 2011 ). Taking advantage of phenomenon such as energy transfer (ET) and the characteristic features of f -electronic transitions, it is possible to obtain efficient luminescence from Ln 3+ -doped materials even when the materials are prepared at nanodimensions. This property is necessary for their potential applications in many areas. The current development of high technologies is one example of domains requiring appropriately designed systems (Bedekar et al. 2009 ; Boulon 2012 ). Furthermore, advanced fields of science, such as medicine and biology, use characteristic properties of Ln 3+ -doped NCs for bioimaging or cancer therapy (Bao et al. 2011 ; Di et al. 2011a ; Diamente et al. 2006 ; Kang et al. 2011 ; Ren et al. 2012 ). Lanthanide-doped nanomaterials are attractive in connection with their exceptional optical and chemical properties, i.e. large effective Stokes shifts, high resistance to photobleaching, blinking and photochemical degradation. These excellent luminescent properties of the lanthanide ions, long luminescence lifetimes and the ability of ET processes occurring between dopants, make it possible to obtain an intense, visible emission under UV or IR (up-conversion) irradiation. In addition, the emission (luminescence lifetime) from Ln 3+ is usually longer than the fluorescence of tissue (background) and differs in the spectral region, which allows for time-resolved fluorescence lifetime imaging (TRFI) (Cubeddu et al. 2002 ; Väisänen et al. 2000 ). This avoids disadvantages of UV excitation resulting in auto-fluorescence of cells. Hence, they present interesting alternatives for dye-based markers. Functionalization and coating of Ln 3+ -doped materials could increase their impact on fundamental biomedical research and clinical practice. Also receiving nanoparticles with mesoporous structure allows for designing multifunctional systems for simultaneous drug delivery and cell imaging (Di et al. 2011b ; Janowski et al. 2012 ; Park et al. 2012 ).