Quantum dot-Eu3+ conjugate as a luminescence turn-on sensor for ultrasensitive detection of nucleoside triphosphates

We report a conjugate of thioglycolic acid (TGA) capped CdTe quantum dot and Eu3+ ion (TGA-CdTe QD-Eu3+) that can be used as an ultrasensitive luminescence turn-on sensor for nucleoside triphosphates (NTPs). The TGA-CdTe QD-Eu3+ conjugate is a weakly luminescent species as a result of the strong quenching effect of Eu3+ ion on the luminescence of TGA-CdTe QDs. The conjugateʹs luminescence can be readily restored by its reaction with adenosine triphosphate (ATP) and other NTPs, and thus gives an ultrasensitive detection of NTPs, with a detection limit of 2 nM. The sensing mechanism has also been explored, and the effective quenching of TGA-CdTe QDs emission by Eu3+ ions has been attributed to photoinduced electron transfer (PET). ATP, as the representative of NTPs, can remove Eu3+ from the surface of TGA-CdTe QDs, leading to restoration of the TGA-CdTe QDs luminescence.