Integration of quantum dots with Zn2GeO4 nanoellipsoids to expand the dynamic detection range of uranyl ions in fluorescent test strips

Fluorescent colorimetric test strips normally have a narrow dynamic detection-range due to the limited responsive range from single responsive materials, which cannot meet the wide detection requirement in practical applications. Herein, we developed an approach to detect uranyl ions (UO22+) with a broad detection range using the synthesized ZnS:Mn quantum dots (QDs) modified Zn2GeO4 nanoellipsoids (Zn2GeO4 @ZnS:Mn NEs), containing two responsive materials with the opposite signal responses at different UO22+ concentrations. Specifically, a red to chocolate color change was observed at low analyte concentrations (0.01-100 μM) resulting from the photoinduced electron transfer effect from ZnS:Mn QDs to UO22+. A sequentially olive drab to green color change has been observed when further increasing the UO22+ concentration (100-1000 μM) as a result of the antenna effect between Zn2GeO4 nanoellipsoids and UO22+. In addition, a low-cost and portable fluorescent test strip has been further fabricated through embedding Zn2GeO4 @ZnS:Mn NEs on a microporous structure membrane, demonstrating a facile yet effective colorimetric response to UO22+ in lab water, lake water, and seawater with a wide dynamic range. Therefore, it is potentially attractive for real-time and on-site detection of UO22+ in sudden-onset situations.