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

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Copper ion (Cu²⁺) detection is critical due to environmental and biological significance.
• Traditional fluorescent sensors are limited by shallow penetration depth of UV/visible excitation.
• Need for sensitive and selective sensors with deeper tissue penetration is evident.

Purpose of the Study:

• To develop a highly sensitive and selective near-infrared (NIR) excitable sensor for Cu²⁺ detection.
• To utilize poly(acrylic acid) (PAA) coated upconversion nanoparticles (UCNPs) for enhanced sensing capabilities.
• To overcome limitations of existing Cu²⁺ detection methods.

Main Methods:

• Fabrication of core-shell-shell structured UCNPs (Na(Yb, Nd)F₄@Na(Yb, Gd)F₄:Tm@NaGdF₄) via co-precipitation.
• Modification of UCNPs with poly(acrylic acid) (PAA) to create the sensor.
• Measurement of upconversion emission intensity changes in response to varying Cu²⁺ concentrations.

Main Results:

• The PAA-UCNPs sensor exhibited a linear decrease in upconversion emission intensity with increasing Cu²⁺ concentration (0.125–3.125 μM).
• A low detection limit of 0.1 μM for Cu²⁺ was achieved.
• The sensor demonstrated high sensitivity and selectivity, even in the presence of other metal ions.
• EDTA addition effectively reversed the emission quenching, confirming the sensing mechanism.

Conclusions:

• PAA-coated UCNPs provide a sensitive and selective platform for Cu²⁺ detection.
• The NIR excitation capability offers advantages over traditional UV/visible sensors.
• This sensor shows promise for practical applications in environmental and biological monitoring of Cu²⁺.