Heavy metal-free MnInPSeS alloyed quantum dots-molecularly imprinted polymer as an electrochemical nanosensor for the detection of the synthetic cathinone, 3,4-methylenedioxypyrovalerone

The unique photophysical and optoelectronic properties of semiconductor quantum dot (QD) nanocrystals have paved the way for their diverse use in several application fields within the chemical, physical, and biology domains. In this work, we report for the first time on the synthesis of alloyed heavy metal-free MnInPSeS QDs via the hot-injection organometallic pyrolysis of metal precursors, organic surfactants, and ligands. To make the QDs biocompatible, stable in aqueous media, and solution-processable, the QDs were capped with 3-mercaptopropionic acid via a ligand exchange reaction. The QDs emitted in the UV/vis region and had a fluorescence quantum yield of 41 %. The QDs were drop-casted on screen-printed carbon electrodes (SPCEs) and from the cyclic voltammetry (CV) analysis, the QDs exhibited efficient electron transfer and enhanced electroactive surface area whilst from the electrochemical impedance spectroscopy (EIS) analysis, the QDs exhibited lower charge transfer resistance which was indicative of enhanced charge transport process. A novel electrochemical nanosensor was thereafter developed for the synthetic cathinone, 3,4-methylenedioxypyrovalerone (MDPV) by electropolymerizing the drug in the presence of dopamine on the QDs/SPCE surface. Under optimized experimental conditions, the developed molecularly imprinted polymer (MIP)@MnInPSeS QDs/SPCE detected MDPV ultrasensitively within the concentration range of 6 nM–600 μM with buffered K3[Fe(CN)6]/K4[Fe(CN)6] redox probe. The limit of detection and limit of quantification obtained were 0.28 nM and 1.39 nM, respectively. An MDPV fingerprint was also obtained electrocatalytically with the MIP@QDs/SPCE nanosensor using differential pulse voltammetry (DPV). Electrochemical profiling analysis showed that MDPV can be selectively detected in drug mixtures containing either known illicit drugs or known cutting agents.