Controllable in situ fabrication of portable AuNP/mussel-inspired polydopamine molecularly imprinted SERS substrate for selective enrichment and recognition of phthalate plasticizers

Abstract

A bio-inspired polydopamine (PDA) molecularly imprinted substrate is fabricated by one-step oxidative self-polymerization of dopamine and template molecules in weakly alkaline medium on screen-printed electrode (SPE). Through the catechol and amine groups on PDA surface, Au nanoparticles (AuNPs) can be easily anchored and growth on PDA-MIP coating, thereby forming a three-dimensional (3D) architecture. By adjusting the reaction conditions, the particle size and distribution of PDA and AuNPs can be well controlled. Benefiting from the “hot spots” generated by AuNPs and recognition sites produced by MIP, the AuNP/PDA-MIP nanocomposite can serve as excellent SERS substrate enabling selective enrichment and identification of phthalate plasticizers (PAEs). Using this substrate, an enhancement factor (EF) up to 1.70 × 107 for dimethyl phthalate (DMP) is achieved with a detection limit as low as 1.0 × 10−10 M. Furthermore, the rebinding kinetics study demonstrates that the portable MIP-based SERS substrate can promptly reach the adsorption equilibrium within 10 min. Thanks to its highly selectivity, the substrate exhibits low SERS interference for structural analogues benzyl butyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP). Besides, the straightforward SERS recognition of DMP in surface water, commercial bottled water and liquor samples are successfully realized using this substrate. This green and environmental-friendly fabrication method is promising for synthesis of highly performance sensing substrate, adsorbent or catalysts. Combining with portable Raman spectrometer, the fabricated MIP-based SERS substrate has exhibited a great potential as on-site device for environmental monitoring, food safety and homeland security.