Lanthanide-based nanoparticles as potential versatile bioprobes

Eva Hemmer, Department of Chemistry and Biomolecular Sciences
Université d'Ottawa

Abstract :
Lanthanide (Ln3+)-based nanoparticles (Ln-NPs) are outstanding candidates for a whole gamut of applications ranging from biomedicine to telecommunication, phosphors, and more recently energy conversion technologies. Those applications are based on the optical properties of the Ln3+ ions. When doped in appropriate host materials, narrow optical absorption and emission bands as well as long lifetimes of the excited electronic states of the Ln3+ are obtained. Following a stepwise excitation with near-infrared (NIR) light, Ln-NPs show upconversion emission spanning the range from UV to visible and NIR. In addition, NIR light of longer wavelengths (> 1000 nm) can be emitted when appropriate Ln3+ dopants are chosen.

The use of NIR light is of particular interest for biomedical applications since these emission wavelengths perfectly match the biological transparency windows. This sets the basis for deeper penetration depth into biological tissues due to less absorption, higher resolution as a result of reduced scattering, and improved imaging contrast due to tissue autofluorescence minimization; all being inevitable requirements for optical in-vivo bioimaging. Moreover, the emission profile of Ln-NPs is sensitive to their thermal environment, thus allowing for application as optical temperature sensors, while upconverting nanoparticles have also been suggested as remote controlled photodynamic agents. Consequently, efficient upconverters and NIR emitters are highly sought after to push current limitations in penetration depth, spatial resolution, and upconversion efficiency. Besides oxides including Gd2O3 or Y2O3, fluorides, such as NaGdF4, are commonly considered as suitable host materials and their preparation via the thermal decomposition process has been widely studied. Seeking better control over reaction conditions allowing for a more precise size, morphology and crystalline phase control, their microwave- assisted synthesis provides an attractive alternative.

Besides shining a light on the potential of Ln-NPs for various applications, some synthetic strategies towards multifunctional Ln-NPs followed by our lab will be presented.

To find out more about Prof. Hemmer's research, you can consult her web page: 

www.hemmerlab.com

Cette conférence est présentée par le RQMP Versant Nord du Département de physique de l'Université de Montréal et de Génie physique de la Polytechnique.