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

Le résumé fourni par la source

The detection of Cu 2+ 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 Cu 2+ ions to specific coating molecules of such nanoparticles. In this work, we systematically investigated the evolution of excitation and emission spectra of NaYF 4 : Yb 3+ /Ho 3+ up-converting nanoparticles functionalized with branched polyethyleneimine (BPEI) as a function of Cu 2+ concentration in water. Hence, the most suitable fluorescence parameters (i.e., emission bands, excitation intensity and excitation wavelength) for Cu 2+ sensing have been determined. The most sensitive emission band (green emission of Ho 3+ ) and the ratiometric sensitivity (ratio between the green and red Ho 3+ emissions) are explained through internal reabsorption of the Ho 3+ ion emitted bands by the Cu 2+ 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 Cu 2+ ions that can be chelated by the PEI molecules at the nanoparticle surface. Thus, this work offers a novel overview to explain the Cu 2+ sensing mechanism by other fluorescent nanoparticles. • NaYF 4 :Yb 3+ /Ho 3+ upconverting nanoparticles as ratiometric fluorescence sensor of Cu 2+ ions. • Influence of spectroscopic parameters in the Cu 2+ sensitivity of UCNPs. • Cu 2+ sensing mechanism of BPEI coated fluorescent nanoparticles by the inner filtering effect. • [Cu 2+ ] as function of the maximum number of Cu 2+ ions that can be chelated by BPEI:UCNPs.

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