Lanthanide doped active-core@active-shell nanoparticles: properties, applications and challanges
Artur Bednarkiewicz a
a Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, Wroclaw, 50, Poland
Invited Speaker, Artur Bednarkiewicz, presentation 012
Publication date: 10th April 2014

Lanthanide doped nanoparticles (Ln:NPs) have gained a tremendous interest in the view of their excellent luminescent properties for bio-medical detection and in-vivo / in-vitro imaging. Since most of biological constituents exhibit their spontaneous (auto)fluorescence under photoexcitation typically suitable to excite the fluorescent labels, it is of critical importance to distinguish the useful signals from background. In order to provide sufficient sensitivity of detection, new, long wavelength (i.e. far red or near infrared) absorbing and emitting dyes and semiconductor quantum dots are sought. Lanthanide doped dielectric nanoparticles (Ln:NPs) and especially up-converting nanoparticles (UCNPs) have become interesting alternative to conventional labels due to their perfect photo stability, spectrally narrowband absorption and emission, blinking-free luminescence and most importantly due to efficient anti-Stokes Vis/NIR emission under NIR photoexcitation. Numerous applications have shown the need for luminescent biolabels with intentionally designed properties. In opposite to bulk materials, such optimised materials can be designed with unprecedented precision by using core-(multi)shell approach. The core and shell parts of the nanoparticles can be independent and heterogenously doped with either optically active lanthanides ions or passive ions.

Because it is extremely difficult to compare different materials aiming at studying the impact of synthesis protocols, presence and type of surface ligands, active and passive dopants, morphology, core-shell architecture and structure of nanoparticles onto the suitability of these up-converting nanoparticles for biological applications, we made efforts to quantitatively compare the luminescent properties of different lanthanide doped up-converting nanoparticles. With the presented system, the time resolved spectra as well as absolute quantum efficiency can be measured versus excitation density (from W/cm2 to MW/cm2), which is very important for the understanding of energy transfer up-conversion processes in nano-colloidal particles in confocal microscopy regimes.

This lecture will summarise the:(a) properties of lanthanide doped nanomaterials and their bio-medical applications : main focus will be devoted to the contruction of spectral codes, bio-sensors and bio-imaging luminescent probes(b) state-of-the-art in core-shell designs and properties of such engineered nanoparticles : main focus will be devoted to active-core@active-shell nanoparticles and Energy Migration Up-conversion(c) the methods to compare properties of luminescent colloidal nanoparticles (time-resolved techniques, power depenedence, quantum efficiency)(d) basic concepts and technical specification of a home-made instrument suitable to study time resolved luminescence and quantum efficiency. (e) properties of active-core@active-shell nanoparticles such as Yb:Ho@Yb:Nd or Yb:Tb@Yb:Nd co-doped NaYF4@NaYF4 core-shell nanoparticles.

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