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Fluorescence lifetime of Rhodamine B in aqueous solutions of polysaccharides and proteins as a function of viscosity and temperature

Abstract

Rhodamine B (RhB) is a well known dye extensively used in thermometric studies, either considering the decrease of the fluorescence intensity or the lifetime (τ) with temperature. Lifetime measurements are preferred over intensity one as they are more robust. In order to expand microscopy thermometry to complex food fluids, the effect of solutes on the τ of RhB was studied using fluorescence lifetime imaging microscopy (FLIM) in a two-photon microscope. Polysaccharides of different molecular weight (glucose, lactose, dextran, maltodextrin, and sodium alginate), as well as whey proteins, were considered as typical model food ingredients. A linear increase of τ with the concentration is observed in most polysaccharides, highlighting that it is not due to an increase of the macroscopic viscosity, but in maltodextrins a Langmuir-like concentration dependence is observed. There are extensive interactions between RhB and whey proteins at small concentrations that increase quickly τ up to saturation at >10 wt% proteins, with τ modelled well using an adsorption Langmuir model. Therefore, the effect of solutes on RhB τ is not related to changes on the macroscopic viscosity. The temperature sensitivity of τ, quantified using apparent activation energies, decreases at high solute contents.

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Publication details

The article was accepted on 12 Oct 2017 and first published on 13 Oct 2017


Article type: Paper
DOI: 10.1039/C7PP00330G
Citation: Photochem. Photobiol. Sci., 2017, Accepted Manuscript
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    Fluorescence lifetime of Rhodamine B in aqueous solutions of polysaccharides and proteins as a function of viscosity and temperature

    R. Mercade-Prieto, L. Rodriguez Rivera and X. D. Chen, Photochem. Photobiol. Sci., 2017, Accepted Manuscript , DOI: 10.1039/C7PP00330G

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