A simple fluorescence-scattering ratiometric sensor for biothiols based on CdTe quantum dots

Developing the ratiometric fluorescence probes for biothiols is significant. However, numerous ratiometric fluorescence probes were established based on a hybrid system or complex material. Herein, a simple ratiometric sensor for biothiols was developed by coupling fluorescence (FL) and second-order scattering (SOS) signals based on CdTe quantum dots (CdTe QDs). Under incident light, CdTe QDs with numerous surface traps possessed weak fluorescence but strong SOS due to the occurrence of resonance-enhanced Rayleigh scattering (RRS). With addition of biothiols, FL was enhanced, while SOS was quenched. Mechanistic studies indicated that fluorescence enhancement could result from surface passivation and a static quenching process of RRS could be responsible for the quench of SOS. The probe was employed for the quantification of glutathione (a typical biothiol) with a wide linear range (0.2–80.0 μmol L −1 ) and a low detection limit (0.05 μmol L −1 ). The sensor for biothiols exhibited outstanding merits, including fast response (1 min), simplicity, strong specificity and high sensitivity. Furthermore, the sensor showed a good performance in detecting the total biothiols in real samples. Overall, a new strategy was proposed for designing the simple ratiometric sensor based on quantum dots.