Demonstration of Temperature Dependent Energy Migration in Dual-Mode YVO4: Ho3+/Yb3+Nanocrystals for Low Temperature Thermometry.
A dual mode rare-earth based vanadate material (YVO4: Ho3+/Yb3+), prepared through ethylene glycol assisted hydrothermal method, demonstrating both downconversion and upconversion, along with systematic investigation of the luminescence spectroscopy within 12-300 K is presented herein. The energy transfer processes have been explored via steady-state and time-resolved spectroscopic measurements and explained in terms of rate equation description and temporal evolution below room temperature. The maximum time for energy migration from host to rare earth (Ho3+) increases (0.157 μs to 0.514 μs) with the material's temperature decreasing from 300 K to 12 K. The mechanism responsible for variation of the transients' character is discussed through thermalization and non-radiative transitions in the system. More significantly, the temperature of the nanocrystals was determined using not only the thermally equilibrated radiative intra-4f transitions of Ho3+but also the decay time and rise time of vanadate and Ho3+energy levels. Our studies show that the material is highly suitable for temperature sensing below room temperature. The maximum relative sensor sensitivity using the rise time of Ho3+energy level (5F4/5S2) is 1.35% K-1, which is the highest among the known sensitivities for luminescence based thermal probes.
Second Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Manoj
M
Kumar Mahata
Second Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Tristan
T
Koppe
Optical Materials &Bio-imaging Research Laboratory, Department of Applied Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, India.
Kaushal
K
Kumar
Second Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Hans
H
Hofsäss
Second Institute of Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Ulrich
U
Vetter