Intracellular pH is an important regulator of cell function, and its subtle changes may greatly affect cell activities and cause diseases. Reliable imaging of intracellular pH remains a huge challenge. Dual-emitting Mn2+-doped quantum dots (QDs) can be directly used as a ratiometric fluorescent probe without further modification, but they displayed low performance in terms of photoluminescence, stability, and intensity ratio regulation. Here, we report intrinsic dual-emitting CdZnSe/Mn:ZnS QDs with high photoluminescence efficiency, good stability, and biocompatibility. The emission intensity ratio was selectively regulated by Mn2+ doping. Because of aggregation-induced quenching of QDs, the exciton emission of CdZnSe/Mn:ZnS QDs (471 nm) was sensitive to pH, while the Mn2+-doped emission (606 nm) was passive to pH, which was probably due to little self-quenching in Mn2+-doped emission caused by weak Mn–Mn coupling interaction. Dual-emitting CdZnSe/Mn:ZnS QDs exhibited excellent pH-responsiveness in the range of pH 4.0 to 12.0 and were used for pH imaging in live HeLa cells. When the pH value of HeLa cells changed from 5.0 to 9.0, the emission changed from red to blue. Furthermore, these dual-emitting CdZnSe/Mn:ZnS QDs can provide a versatile platform for biosensors and biological imaging.
Ning Li,Tiantian Wu,Yuzheng Cai,Tiange Li,Lianjun Song,Xianqing Huang,Jiansheng Zhao,Erkigul Bukyei,Tianlin Wang
Lead ion (Pb 2+ ) pollution seriously threatens the quality of aquatic products. In this study, a ratiometric fluorescence sensor consisting of tangerine fluorescent Mn:ZnS QDs (T-QDs) and blue fluorescent Fe-MOF (B-MOF) was developed for selective recognition of Pb 2+ . Upon exposure to Pb 2+ , the fluorescence of T-QDs was quenched while the fluorescence of B-QDs was slightly changed, causing the changes of fluorescence colors from tangerine to blue with a detection limit (LOD) of 3.79 nmol/L. The sensor also had the strengths of low cost, easy to operate, excellent sensitivity and selectivity. Significantly, a portable detection platform integrated with the sensor was constructed to achieve on-site visual detection. As expected, the detection platform was successfully applied for testing Pb 2+ with the LOD of 7.78 nmol/L. The strategy may not only provide a great capacity for on-site monitoring of Pb 2+ in aquatic products but also expand application in environmental pollution detection.
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