Beta-cyclodextrin decorated nanostructured SERS substrates facilitate selective detection of endocrine disruptor chemicals

Abstract

We demonstrate the selective detection of endocrine disruptor chemicals (EDCs) from river water using surface enhanced Raman scattering (SERS). By means of nanosphere lithography, the SERS substrate was prepared via the initial deposition of a monolayer of silica nanospheres (with diameter of ∼330 nm) on a silicon substrate as the template. Subsequently, a 180 nm thick layer of silver followed by a 20 nm layer of gold was deposited. This surface was modified with mono-6-deoxy-6-((2-mercaptoethyl)amino)-beta-cyclodextrin (β-CD) in order to produce a selective capture surface suitable for EDC capture and their detection by means of SERS. We show that EDC model compounds, including 3-amino-2-naphthoic acid (NAPH), potassium hydrogen phthalate (PHTH) and the EDC β-estradiol (ESTR), were captured by the β-CD decorated surface. This surface facilitated SERS detection with limits of detection of 3.0 μM (NAPH), 10 μM (PHTH) and 300 nM (ESTR), all 10-100 times lower than that without the surface modification with β-CD. Individual and simultaneous detection of NAPH and PHTH from their mixture was achieved as evidenced using the bianalyte Raman technique.