A ratiometric fluorescent sensor based on molecularly imprinted multilevel mesoporous silica for highly sensitive detection of imidacloprid

Herein, A ratiometric fluorescent sensor based on molecularly imprinted multilevel mesoporous silica (MIFP-SiCQDs@CdTe QDs) was designed for highly sensitive detection of imidacloprid (IDP) pesticide with long half-life in soil, plants, and water environments. In this sensor, CdTe QDs were anchored onto the multilevel mesoporous of MIFP-SiCQDs by post-imprinting modification as the analytical signal to improve the detection sensitivity of the conventional doping method (d-MIFP). The results showed that the synthesized MIFP-SiCQDs@CdTe QDs possessed both small mesopore (2-3 nm) and large mesopore (5-50 nm), which is favorable for the anchoring of CdTe QDs (about 2-3 nm in diameter) and the mass transfer of IDP into them. Due to the multilevel mesoporous structure and low background, the sensor responded well to the addition of IDP in the range of 5 ng mL-1-0.5 mu g mL-1 with a detection limit of 3.55 ng mL-1. The MIFP-SiCQDs@CdTe QDs sensor was successfully applied to determine IDP levels in real samples with the average recovery ranging from 97.64 to 109.88% and RSD values ranging from 1.00 to 4.65%. Furthermore, the quenching mechanism of MIFP-SiCQDs@CdTe QDs by IDP was considered to be the dynamic quenching. These results proved that the construction of multilevel mesoporous and post-imprinting modification of the analytical signal is an effective method to improve the sensitivity of d-MIP.