Highly Selective Photoelectrochemical Sensing Platform Based on Upconversion Nanoparticles and Quantum Dots for Sensitive Detection of Cu2+

The Photoelectrochemical (PEC) detection methodology has piqued considerable interest, positioning itself as a pioneering strategy in the evolution of Cu2+ sensors. In this paper, we propose a PEC sensing platform for detecting Cu2+ in solution using upconversion nanoparticles (UCNPs) as the converter light source and CdTe quantum dots (QDs) as the photoactive materials. When irradiated with a 980 nm light source, the UCNPs will effectively absorb this laser wavelength and subsequently emit fluorescence around 550 nm, while the CdTe QDs will absorb the 550 nm fluorescence emitted by the UCNPs and undergo an electron-hole separation, where the electrons will be transferred into the indium tin oxide (ITO) electrode via the multi-walled carbon nanotubes (MWCNTs). When Cu2+ is present, Cu2+ will be reduced to Cu+ by the electrons generated by the CdTe QDs, which hinders the transfer of electrons from the CdTe QDs to the ITO electrodes, leading to a decrease in current. The photocurrent decreases with the increase of Cu2+ concentration and shows a good linear relationship with Cu2+ concentration in the range of 1 μM to 25 μM, and its lowest detection limit is 0.5 μM.