PAA Modified Upconversion Nanoparticles for Highly Selective and Sensitive Detection of Cu2+ Ions

Shaoshan Su; Zhurong Mo; Guizhen Tan; Hongli Wen; Xiang Chen; Deshmukh A Hakeem

doi:10.3389/fchem.2020.619764

PAA Modified Upconversion Nanoparticles for Highly Selective and Sensitive Detection of Cu²⁺ Ions

Front Chem. 2021 Jan 8:8:619764. doi: 10.3389/fchem.2020.619764. eCollection 2020.

Authors

Shaoshan Su¹, Zhurong Mo¹, Guizhen Tan¹, Hongli Wen¹, Xiang Chen¹, Deshmukh A Hakeem¹

Affiliation

¹ Key Laboratory of Clean Chemistry Technology of Guangdong Regular Higher Education Institutions, School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, China.

Abstract

Detection of the Cu²⁺ ions is crucial because of its environmental and biological implications. The fluorescent-based organic sensors are not suitable for Cu²⁺ detection due to their short penetration depth caused by the UV/visible excitation source. Therefore, we have demonstrated a highly sensitive and selective near-infrared (NIR) excitable poly(acrylic acid) (PAA) coated upconversion nanoparticles (UCNPs) based sensor for Cu²⁺ detection. We construct the PAA modified Na(Yb, Nd)F₄@Na(Yb, Gd)F₄:Tm@NaGdF₄ core-shell-shell structured UCNPs based sensor via a co-precipitation route. The upconversion emission intensity of the PAA-UCNPs decreases linearly with the increase in the Cu²⁺ concentration from 0.125 to 3.125 μM due to the copper carboxylate complex formation between Cu²⁺ and PAA-UCNPs. The calculated detection limit of the PAA-UCNPs based sensor is 0.1 μM. The PAA-UCNPs based sensor is very sensitive and selective toward detecting the Cu²⁺ ions, even when the Cu²⁺ co-exist with other metal ions. The EDTA addition has significantly reversed the upconversion emission quenching by forming the EDTA-Cu²⁺ complex based on their greater affinity toward the Cu²⁺. Therefore, the PAA-UCNPs based sensor can be a promising candidate for Cu²⁺ detection because of their higher sensitivity and selectivity under 980 nm NIR excitation.

Keywords: copper ions; energy transfer; fluorescent probe; poly(acrylic acid) (PAA); upconversion nanoparticles (UCNPs).