Preparation of molecularly imprinted polymer nanoparticles for selective adsorption of caffeine using dual-functionalized Ag2S quantum dots

Abstract

Caffeine is the most abundant and widely consumed active medicinal compound, making it the most representative pollutant in the environment. This research involved synthesizing high-performance fluorescent HOOC-CC-functionalized Ag2S quantum dots (HOOC-QDs) measuring approximately 4.35 nm in size using the hydrothermal method. These QDs were then used to produce fluorescent molecularly imprinted polymer nanoparticles (MIP-Ag2S NPs) measuring 20.31 nm. The MIP-Ag2S NPs were created through a graft suspension copolymerization process involving methacrylic acid monomer, ethylene glycol dimethacrylate cross-linker, and caffeine template molecules. The polar carboxylic acid groups enhance the interaction with the template molecules, which is crucial for selectivity, and the -CC- groups aid in network formation. The MIP-Ag2S NPs emitted fluorescence at around 500 nm, which was significantly reduced after caffeine adsorption. The pH-sensitive MIP-Ag2S NPs had a maximum caffeine adsorption capacity of 488 mg/g at pH 6 and a maximum release of approximately 96% at pH 2.2. Additionally, repeated cycles of adsorption and desorption did not result in a significant loss of adsorption capacity. The HOOC-QDs can be used to prepare MIPs for extracting and recognizing pollutants and medicine in water and for controlled drug delivery systems.