Seminar of the Division of Biomedical Physicochemistry
Sala audytoryjna
From bulk to nano – studies of size-dependent photon avalanche
Dr Marcin Szalkowski
Oddział Fizykochemii Biomedycznej, INTiBS PAN
Lanthanides trivalent ions (Ln3+), due to their unique properties, such as high photostability, complex structure of energy levels, long lifetimes of excited states and relatively efficient anti-Stokes multicolor emissions, in particular in ranges corresponding to transmission windows of biological tissues, have found broad applications in optoelectronics, sensorics and biomedical research. Moreover, Ln3+ ions can be incorporated into crystal matrices characterized by various sizes, tailored for particular needs of given utilization. However, a list of Ln3+ applications can be successfully extended by using highly non-linear pumping scheme known as photon avalanche (PA), where slight changes of illumination power lead to rapid growth of the luminescence intensity by even 2 or 3 orders of magnitude. Although PA has been known and studied in single crystals from 1979, just recently a full demonstration of photon avalanche emission was presented in colloidal Tm3+-doped NaYF4 nanocrystals in room temperature with high non-linearity (power law order exceeding 30) what enabled to confirm previous predictions of suitability of PA nanomaterials for a new type of single excitation beam super-resolution imaging.
We continue this work and present systematic studies comparing PA performance of the LiYF4: Tm3+ structures of varying scale, from bulk monocrystal, through microcrystals of c.a. 40-60 µm, to nanocrystals with various architectures. Each of the structures, even composed of the same host doped with the same concentration of Tm3+, exhibited PA emission, however its characteristics significantly varied between them. We show size dependencies of essential PA parameters, such as order of the nonlinearity of power dependence and power dependent luminescence rise time slowing down. The presented results confirm high potential of such structures for applications in bioimaging and sensorics.
