Application of Upconversion Nanoparticles to monitor luminescent tracers in water

MARCOS ILLESCAS; JUAN M. BUJJAMER; MARÍA C. MARCHI; HERNÁN E. GRECCO; BEATRIZ C. BARJA

Compiègne

Conferencia; 3rd Conference on Properties, Design, and Applications of Upconversion Nanomaterials; 2021

Université Paris-Sud / Université de Rouen

Fluorescent tracers are dyes widely used in hydrology for dispersion and transport studies in surface water and groundwater systems1. To overcome the detrimental effects caused by the natural fluorescence background we propose the use of β-NaYF4:Yb3+,Er3+ UCNP (upconversion nanoparticles2) excited in the NIR to monitor a model tracer dye RB (Rhodamine B) through an energy transfer (ET) mechanism. One key property in tracer applications is to ensure homogeneity in the test volume, which we address by a surface modification by PVP (polyvinylpirrolidone) to provide stable transparent dispersions in water.The addition of RB to aqueous dispersions of PVP modified UCNP deactivates the green emission of the UCNP with the corresponding enhancement of the fluorescence of the dye at 580 nm indicating that an ET process is taking place. From the Stern Volmer plots, a linear calibration curve was obtained from which the detection limits could be calculated being the Limit of Detection (LOD): 3SD/slope 340 ppb for the UCNP of the Figure. The ET efficiency computed from the lifetimes of the UCNP without (τ0) and with RB (τ0) as % E=1-_0/ is only 7% indicating that the quenching is mostly static in nature. The LOD could be improved by an optimisation of parameters not explored yet, such as incident power, and PVP content. It is worth mentioning that the UCNP were intentionally not functionalised in order to keep the synthesis inexpensive for large volumes needed in tracer applications.