Lanthanide‐Based Single‐Chain Nanoparticles as “Visual” Pass/Fail Sensors of Maximum Permissible Concentration of Cu2+ Ions in Drinking Water

Abstract

AbstractThe maximum permissible concentration (m.p.c.) of Cu2+ ions in drinking water, as set by the World Health Organization (WHO) is m.p.c. (Cu2+)WHO = 30 × 10−6 m, whereas the US Environmental Protection Agency (EPA) establishes a more restrictive value of m.p.c. (Cu2+)EPA = 20 × 10−6 m. Herein, for the first time ever, a family of m.p.c. (Cu2+) “visual” pass/fail sensors is developed based on water‐soluble lanthanide‐containing single‐chain nanoparticles (SCNPs) exhibiting an average hydrodynamic diameter less than 10 nm. Both europium (Eu)‐ and terbium (Tb)‐based SCNPs allow excessive Cu2+ to be readily detected in water, as indicated by the red‐to‐transparent and green‐to‐transparent changes, respectively, under UV light irradiation, occurring at 30 × 10−6 m Cu2+ in both cases. Complementary, dysprosium (Dy)‐based SCNPs show a yellow color‐to‐transparent transition under UV light irradiation at ≈15 × 10−6 m Cu2+. Eu‐, Tb‐, and Dy‐containing SCNPs prove to be selective for Cu2+ ions as they do not respond against other metal ions, such as Fe2+, Ag+, Co2+, Ba2+, Ni2+, Hg2+, Pb2+, Zn2+, Fe3+, Ca2+, Mn2+, Mg2+, or Cr3+. These new m.p.c. (Cu2+) “visual” pass/fail sensors are thoroughly characterized by a combination of techniques, including size exclusion chromatography, dynamic light scattering, inductively coupled plasma‐mass spectrometry, as well as infrared, UV, and fluorescence spectroscopy.