Optical nanothermometry properties of Er3+ ions in Y3Ga5O12 nanogarnet
Ulises Ruymán Rodríguez-Mendoza a b, Víctor Lavín a b, Sergio Fabián León-Luis a b, Virginia Monteseguro a b, Jesús González b d, Rafael Valiente b e, Mónica L. Fanarraga c, Inés Temiño e, Vemula Venkatramu f
a Universidad de La Laguna, Departamento de Física, San Cristóbal de La Laguna, 38207, Spain
b MALTA Consolider Team, Spain
c Universidad de Cantabria-IDIVAL, Departamento de Biología Molecular, Santander, 39011, Spain
d Universidad de Cantabria, CITIMAC, 39005 Santander, Spain
e Universidad de Cantabria, CITIMAC, 39005 Santander, Spain
f Yogi Vemana University, Department of Physics, 516003 Kadapa, India
Invited Speaker, Víctor Lavín, presentation 011
Publication date: 10th April 2014

High efficient fluorescent Er3+-doped Y3Ga5O12 (YGG) nanogarnets, with crystalline sizes ranging from 40 to 60 nm, have been synthetized by a sol-gel method and their optical properties have been characterized in order to explore their potential bioimaging applications as temperature nano-sensor. Nanothermometry is especially important in biomedicine and can help extracting knowledge of the local dynamics and performance of the majority of biological microorganism (cell, bacteria,…) that are strongly determined by temperature, and whose sizes are larger than the nanoparticles.  Moreover, they can be used in in vivo and in vitro biomedical applications, where the rare earth doped nanoparticles are used as nanothermometers, playing a key role in the control of hyperthermia processes induced either by alternated magnetic fields or by light. In this sense, the rare earth doped inorganic nanoparticles have the advantages of better biologic compatibility and smaller cytotoxicity compared with quantum dots, and they do not need further functionalization to enter into the cells.  Optical nanothermometers are calibrated using different parameters (lifetime, polarization, bandwidth, etc.); however, the most widely used is the relative intensities of the emissions from two thermalized states. In this work, we analyze the temperature dependence of green emissions of Er3+ ions in a YGG nanogarnet for its use as optical temperature nanosensors. The green luminescence can be obtained either by de-excitation processes from high energy levels, excited by a blue laser, to the 2H11/2,4S3/2 thermalizing levels or by upconversion processes induced by infrared laser excitation, through the therapeutic window. The photoluminescence and thermal sensitivity together with their application in cells assays are also analyzed in detail.

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