Fluorescence sensing mechanism of contaminant Cu2+ in water by up-converting nanoparticles

Puga R.; López-Peña G.; Ortiz E.; Pinto A.; Troya G.; Loro H.; Solé J.G.; Lifante-Pedrola G.; Ortgies D.H.; de Cárdenas L.F.; Cantelar E. · Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy (2026) · DOI: 10.1016/j.saa.2025.127105

Resumen

The detection of Cu2+ trace ions in water is significant due to their environmental implications and potential consequences for human health. Recent methods utilized up-converting nanoparticles, which emit visible light under near-infrared (NIR) radiation and offer the advantages of simplicity and high sensitivity in detection. Most of these studies are based on monitoring the decrease in the up-conversion emission intensity of suitable bands due to the adhesion affinity of Cu2+ ions to specific coating molecules of such nanoparticles. In this work, we systematically investigated the evolution of excitation and emission spectra of NaYF4: Yb3+/Ho3+ up-converting nanoparticles functionalized with branched polyethyleneimine (BPEI) as a function of Cu2+ concentration in water. Hence, the most suitable fluorescence parameters (i.e., emission bands, excitation intensity and excitation wavelength) for Cu2+ sensing have been determined. The most sensitive emission band (green emission of Ho3+) and the ratiometric sensitivity (ratio between the green and red Ho3+ emissions) are explained through internal reabsorption of the Ho3+ ion emitted bands by the Cu2+ ions located in the BPEI coating of the nanoparticles. The detection range (up to 200 μM) is discussed in terms of the limited number of Cu2+ ions that can be chelated by the PEI molecules at the nanoparticle surface. Thus, this work offers a novel overview to explain the Cu2+ sensing mechanism by other fluorescent nanoparticles.

Instituciones: Universidad Nacional de Ingeniería