Colorimetric Detection of UO₂ Using Gold Nanoparticles Immobilized with Pillar[5]arene Complexes with Nitrophenyldiacetic Acids as a Chemoprobe.

Uranium is a crucial raw material in the nuclear energy industry; however, its radioactive nature makes it a critically damaging component to both the atmosphere and human health. In this study, we report a simple and cost-effective selective colorimetric detection technique for UO₂ using nitrophenyldiacetic acids (NPD)-functionalized gold nanoparticles (Au NPs ). The hybrid Au NPs can be induced to aggregate in the presence of UO₂ ions. UO₂ can be recognized by the colorimetric response of hybrid Au NPs , which can be observed by a UV-Vis spectrophotometer and it is easily detectable by the naked eye. The hybrid Au NPs bound by UO₂ possess a good selective response compared to other metal ions (Li, Na, K, Rb, Cs, Ca, Mg, Ba, Ni, Zn, and Co), which can be observed by a prominent color change. The color of the hybrid Au NPs changed from red to dark red upon addition of UO₂ in the presence of other metal ions. Job's plot demonstrates that one NPD moiety attached onto the surface of Au NPs forms 1:1 stoichiometry with UO₂, hence providing a simple and effective colorimetric sensor for the real-time detection of UO₂.