Abstract
In this study, highly active Fe3O4@PDA@Au@GO surface-enhanced Raman spectroscopy (SERS) active substrate was synthesized for application in the enrichment and detection of trace polycyclic aromatic hydrocarbons (PAHs) in the environment. The morphology and structure were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and UV–visible absorption spectrum (UV–vis spectra). The effect of each component of Fe3O4@PDA@Au@GO nanocomposites on SERS was explored, and it was found that gold nanoparticles (Au NPs) are crucial to enhance the Raman signal based on the electromagnetic enhancement mechanism, and apart from enriching the PAHs through π–π interaction, graphene oxide (GO) also generates strong chemical enhancement of Raman signals, and polydopamine (PDA) can prevent Au from shedding and agglomeration. The existence of Fe3O4 aided the quick separation of substrate from the solutions, which greatly simplified the detection procedure and facilitated the reuse of the substrate. The SERS active substrate was used to detect phenanthrene in aqueous solution with a detection limit of 10−7 g/L (5.6 × 10−10 mol/L), which is much lower than that of ordinary Raman, it is promising for application in the enrichment and detection of trace PAHs.
Highlights
Containing a group of organic molecules comprised of two or more aromatic rings, polycyclic aromatic hydrocarbons (PAHs) are stable in structure and not degraded, they belong to the persistent hydrocarbons [1,2,3]
PAHs are highly toxic with strong carcinogenicity, teratogenicity and mutagenicity, and 16 types of them appear in the environmental priority control list by the United States Environmental Protection Agency (EPA) according to their toxicity to human health [3,4,5]
The UV–vis spectra in Figure 1 demonstrate the maximum absorption of Au NPs synthesized by various masses of sodium citrate, which are located at the range of 350 nm–600 nm
Summary
Containing a group of organic molecules comprised of two or more aromatic rings, polycyclic aromatic hydrocarbons (PAHs) are stable in structure and not degraded, they belong to the persistent hydrocarbons [1,2,3]. One of the most commonly used method is to modify the plasmonic metal surface with different functional groups (e.g., cyclodextrin [21], alginate gel [22], viologen dications [23] and calixarene [24]), which can bring PAHs molecules close to the surface of nanostructured plasmonic metal This method could achieve SERS detection of PAHs, the organic molecules used for modification are usually difficult to synthesize or expensive, which limits the practical application of SERS. Being an important derivative of graphene, graphene oxide (GO), known as functional graphene, has a two-dimensional spatial structure and is a carbon-based nanomaterial with abundant hydroxyl, epoxy, carboxyl and other oxygen-containing energy groups It has high specific surface energy, good hydrophilic and mechanical properties, and good adsorption to many chemicals. This method was used to study the enrichment and detection effect of phenanthrene solution in aqueous solution and to obtain the detection limit, which provides new research methods and ideas for the synthesis of new composite SERS substrate and detection of trace PAHs in water
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