A first approach to the use of upconversion nanoparticles to measure luminescent tracers in water: A proof of concept

M. ILLESCAS; J. BUJJAMER; M.C. MARCHI; H. GRECCO; B.C. BARJA.

Lima

Workshop; Workshop Internacional de Nanociencias para el medio ambiente y la salud 2020; 2020

Red NanoAndes

Fluorescent tracers are dyes widely used in hydrology for dispersion and transport studies in surface water and groundwater systems. To overcome the detrimental effects caused by the natural fluorescence background we propose a new detection methodology based on the upconversion luminescent process using UCNP1 (upconversion nanoparticles) excited in the NIR to monitor a target tracer dye RB (Rhodamine B) through an energy transfer (ET) mechanism. Synthesis: core β-NaYF4:Yb3+,Er3+and core/shell β-NaYF4:Yb3+,Er3+@NaYF4 UCNP were synthetized by thermal decomposition methods. The Figure 1 shows four UCNP synthetized from chloride ?Cl? or trifluoroacetate ?TFA? precursors which were characterized by stationary and time dependent emission spectroscopy as well as DRX and SEM techniques. Emission studies: The green emission of these UCNP (Donor) under 980 nm excitation overlaps the broad absorption band of RB at ca. 550 nm (Acceptor). This fact enables the detection of the tracer through its fluorescence at 580 nm by NIR excitation. The surface of these particles were modified by PVP (polyvinylpirrolidone) to provide stable transparent dispersions in water.The addition of incremental volumes of RB to an aqueous dispersion of UCNP showed the consequent deactivation of the green emission of the UCNP with the corresponding enhancement in the fluorescence of the dye at 580 nm demonstrating that an energy transfer process was taking place. Plotting the area of the green band emission of the UCNP as a function of the concentration of the dye, a linear relationship was obtained from which a detection limit could be calculated. LD (ppm): 3SD/slope= 0,3ppm.