Colorimetric Detection of UO2+₂ Using Gold Nanoparticles Immobilized with Pillar[5]arene Complexes with Nitrophenyldiacetic Acids as a Chemoprobe

Colorimetric detection for uranyl ions in water using vinylphosphonic acid functionalized gold nanoparticles based on smartphone

A simple and portable colorimetric sensor for colorimetric detection of UO₂²⁺ in aqueous solution based on vinylphosphonic acid functionalized gold nanoparticles (VPA-AuNPs) has been developed. The VPA-AuNPs solution was prepared by sodium borohydride reduction in the presence of vinylphosphonic acid. The addition of UO₂²⁺ would induce aggregation of VPA-AuNPs, resulting in the color change from wine-red to blue, and red-shift of the ultraviolet-visible (UV-vis) spectra. The UO₂²⁺ assay based on VPA-AuNPs showed good selectivity and sensitivity, with a limit of detection to be approximately 2.0 μM by naked eyes and 1.07 μM by UV-vis (S/N = 3) respectively. Additionally, a smartphone with a free application named "PhotoMetrix" was employed to estimate the color intensities (red, green, blue value) of VPA-AuNPs in the presence of UO₂²⁺ with different concentrations, and the concentration of UO₂²⁺ samples could be conveniently exported by the calculated univariate calibration curves. This method shows good feasibility for on-site UO₂²⁺ detection in an aqueous solution.

Ultrasensitive detection of UO2 2+ based on dopamine-functionalized MoOx quantum dots

Uranium is an important nuclear fuel and the risk of human exposure to uranium increases as increasing amounts of uranium-containing waste enter the environment due to the rapid growth of nuclear power. Therefore, rapid, sensitive, and portable uranium detection is a promising approach to effectively control and monitor uranium contamination. To achieve this goal, abundant oxygen- and nitrogen-containing groups were introduced to molybdenum oxide quantum dot (MoO_x QDs) surfaces with dopamine (DA) modification. Due to the excellent coordination ability of oxygen- and nitrogen-containing groups with uranium, the obtained DA-functionalized MoO_x QDs (DA-MoOx QDs) showed a strong binding affinity for uranium and sensitivity was increased nearly 1000-fold compared with MoO_x QDs alone. The limit of detection was 3.85 nM, which is higher than most of the reported nanomaterials. Moreover, the DA-MoOx QD-based method showed high selectivity and uranium could be clearly detected under masking with ethylenediaminetetraacetic acid even when the concentration of other metal ions was 100-fold higher than that of uranium, showing a very promising method for uranium contamination control and monitoring.

A responsive photonic crystal film sensor for the ultrasensitive detection of uranyl ions

As an effective nuclear energy resource, uranium plays an important role in industry and energy but the wastes of uranium also cause radioactive contamination, which is harmful to the environment and the human body. Herein, a responsive photonic crystal (PC) film sensor for the ultrasensitive and label-free detection of uranyl ions (UO₂²⁺) has been proposed, which is easy to construct and does not need to be combined with a hydrogel. The PC film is not pH-sensitive because it is obtained by the self-assembly of methyl methacrylate-acrylonitrile co-polymeric nanospheres (PMMA-AN). These nanospheres were modified with amidoxime groups, which have a good coordination ability with UO₂²⁺. The bindings between nanospheres and UO₂²⁺ change the refractive index and disturb the face-centered cubic structure of the film, which leads to a decrease in the diffraction peak intensity of the PC film. The sensor works in the concentration range of 10 pM to 100 μM for UO₂²⁺ determination and the decreased intensities of the diffraction peaks are linearly correlated with the logarithm of UO₂²⁺ concentration in the range from 1 nM to 100 μM. Moreover, the sensor shows good selectivity for UO₂²⁺ and can also perform the determination of UO₂²⁺ in a real sample. The responsive PC film sensor shows great potential in the label-free and ultrasensitive detection of UO₂²⁺.