Triplet-Triplet Annihilation Upconversion in Water Environment: Biocompatible and Non-invasive All-optical Temperature Sensing for Living Objects

D. Busko, R. Dimitrova, A. Turshatov, Y. Avlasevich, K. Landfester, S. Baluschev
Max Planck Institute for Polymer Research, DE

Keywords: temperature sensing, all-optical, non-invasive


A realistic temperature sensing alternative for life-science objects could be the process of triplet-triplet annihilation upconversion in water environment (TTA – UC): It is inherently micro-scale sensing techniques – the sensing function is carried out by ensembles of organic macromolecules. The TTA–sensing function is performed in all-optical regime. The sensing properties and the efficiency of the process of TTA–UC do not depend on the coherence characteristics of the used light. Excitation sources emitting light with extremely low spectral power density (~125µWnm-1) can generate efficient TTA−emission. The sensing molecules have broad absorption spectra, in some cases even up to 80nm (FWHM). For bio-applications it is important to ensure, that the sensing light does not interact with the sample. The process of TTA–UC in water environment demonstrates well expressed ratiometric response on the sample temperature: instead a single material response on the acting parameter (temperature) a ratiometric material response is obtained, ensuring inherent compensation on the local changes of the sample parameters: the ratio of integral delayed fluorescence to the residual phosphorescence is changed more than 11 times for the temperature interval of 24 K, centered at 30°Celsius and temperature sensitivity better than 0.05 K.