Pretreatment-free selective and reproducible SERS-based detection of heavy metal ions on DTPA functionalized plasmonic platform

Abstract

Here we report a surface plasmon-polariton based functionalized SERS platform for the detection of heavy metal ions. Homogenous distribution of the plasmon intensity on the ordered plasmon structure and high affinity of diethylenetriaminepentaacetic acid (DTPA) to heavy metal ions allows the efficient entrapping of heavy metal ions as well as their selective and sensitive detection (LOD was found 10−14M). Periodical gold structure was created using the excimer laser beam treatment of polymer surface and further coating by gold. DTPA molecules were covalently attached to the gold surface through the two step procedure: (i) grafting of 4-aminophenylene groups via diazonium chemistry and (ii) their acylation by DTPA-anhydride. Grafted DTPA molecules showed high SERS response, due to the SPP excitation and propagation on the gold grafting. Efficient chelating of heavy metal ions by DTPA molecules from solution results in pronounced changes of their SERS response. The shift of carbonyl Raman peak position was found to be dependent on the atomic number of heavy metal ions, enabling the selective detection even in the mixture of few metals. Applied SERS platform can be realized using the portable SERS spectrophotometer and requires the minimal equipment cost as well as the experimental time.