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Issue 11, 2017
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Fluorescence lifetime of Rhodamine B in aqueous solutions of polysaccharides and proteins as a function of viscosity and temperature

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Abstract

Rhodamine B (RhB) is a well known dye extensively used in thermometric studies, either considering the decrease in the fluorescence intensity or the lifetime (τ) with temperature. Lifetime measurements are preferred over intensity ones 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 weights (glucose, lactose, dextran, maltodextrin, and sodium alginate), as well as whey proteins, were considered as typical model food ingredients. A linear increase in τ with the concentration is observed in most polysaccharides, highlighting that it is not due to an increase in 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 quickly increase 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 in the macroscopic viscosity. The temperature sensitivity of τ, quantified using apparent activation energies, decreases at high solute contents.

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

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Publication details

The article was received on 31 Aug 2017, accepted on 12 Oct 2017 and first published on 13 Oct 2017


Article type: Paper
DOI: 10.1039/C7PP00330G
Citation: Photochem. Photobiol. Sci., 2017,16, 1727-1734
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    Fluorescence lifetime of Rhodamine B in aqueous solutions of polysaccharides and proteins as a function of viscosity and temperature

    R. Mercadé-Prieto, L. Rodriguez-Rivera and X. D. Chen, Photochem. Photobiol. Sci., 2017, 16, 1727
    DOI: 10.1039/C7PP00330G

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