Highly selective photoelectrochemical sensing platform based on upconversion nanoparticles and quantum dots for sensitive detection of Cu2+

The photoelectrochemical (PEC) detection method, as a potential strategy for Cu2+ detection, has garnered widespread attention. In this paper, we present a PEC sensing platform using upconversion nanoparticles (UCNPs) as the conversion light source and CdTe quantum dots (QDs) as the photoactive material for the detection of Cu2+ in solution. When irradiated with a 980 nm light source, the UCNPs will absorb the 980 nm laser and emit fluorescence around 550 nm, which is then absorbed by the CdTe QDs. This absorption leads to electron-hole separation, with electrons transferring through the multi-walled carbon nanotubes (MWCNTs) into the indium tin oxide (ITO) electrode. In the presence of Cu2+, the Cu2+ will be reduced to Cu+ by the electrons generated by the CdTe QDs, thereby hindering the transfer of electrons from the CdTe QDs to the ITO electrode and resulting in a reduction in current. The photocurrent continuously decreases with increasing Cu2+ concentration and shows a good linear relationship with Cu2+ concentration in the range of 1 µM to 25 µM. The lowest detection limit is 0.5 µM.