Ratiometric fluorescence sensor for Cu²⁺ detection based on opposite responses of two fluorescence reagents to SBA-15...

One of the many environmental contamination issues around the world is the safer detection or sensing of heavy metal ions. Between all metal ions, it is of critical importance to detect Cu²⁺ ions in a highly sensitive and specific way owing to their wide distribution in many physiological processes. Herein, an interesting fluorescence sensing platform was designed for the specific detection of copper ions (Cu²⁺) with excellent photobleaching resistance. In this matter, a dual-emission ratiometric fluorescence sensor was fabricated based on SBA-15-grafted 2-naphthalenemethanol group (2-NM) as a signal reference and zinc sulfide quantum dots (ZnS QDs) as a response, greatly improving experiment accuracy. After adding various metal ions, the fluorescence intensity of 2-NM almost remained unchanged. In contrast, the fluorescence intensity of ZnS QDs indicated the highest response toward Cu²⁺ among metal cations. Upon the addition of Cu²⁺ ions, the sensor presented a 5-fold fluorescence intensity change (I₃₂₀/I₄₃₀), suggesting that the sensor can be used to detect Cu²⁺ with high sensitivity. The level of Cu²⁺ can be measured within a wide linear range from 1.0 to 10.0 µmol L^- 1 with a sensitive detection limit of 37.5 nM and a quick sample-to-answer monitoring time of 3 min, which is quite certified for regularly monitoring Cu²⁺. Additionally, the developed method could be applied to the efficient quantification of Cu²⁺ in practical samples. The presented strategy provides a convenient system for detecting various metal ions in biological activity with high selectivity and good bio-compatibility.