A Method to Improve the Performance of Gold Nanoparticle Suspensions for Trace Detection of 16 EPA Priority PAHs

Abstract

The growing demand for fast, simple and inexpensive analytical techniques to investigate environmental pollution has resulted in a large number of studies where surface enhanced Raman spectroscopy is used to detect environmental contaminants. However, extraction of weak Raman spectra from complex background signals remains challenging. In this current work, the author has presented a method to improve the performance of gold nanoparticles suspensions for trace detection of the 16 EPA priority PAHs. The gold nanoparticles in suspension are first mixed with the analyte in the liquid phase and then transferred to a solid state by drying (as opposed to liquid sample + dry substrate or liquid sample + liquid substrate). This method allows for a complete background signal removal (including fluorescence and signal from the substrate), strong Raman signal enhancement from the analyte and a reduction in substrate preparation time. Performance of a developed substrate (CNP-Au) was compared with a commercially available 3D substrate (Ram-SERS-Au) by measuring of all 16 EPA priority PAHs. The developed CNP-Au substrate exhibited experimentally obtained LODs three orders of magnitude lower than Ram-SERS-Au, down to the range of 1 ppb. The standard deviation of signal reproducibility for CNP-Au is 14%. Ram-SERS-Au and CNP-Au were characterized using SEM imaging.

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“…Data was analyzed using LabSpec 6 software. According to previous studies, CNP-Au substrate is capable of detecting 16 EPA priority PAHs in concentrations between 1 ppb and 10 ppm.…”

“…Before each measurement, 100 μl of CNP-Au was mixed with 100 μl of the sample on top of a glass slide or glass Petri dish and placed in an oven under 45 °C for 1 h to allow liquid evaporation and crystal formation. The full description of this method, as well as PAH reference measurements, is presented elsewhere . All SERS measurements were recorded at room temperature with a Raman microscope (Xplora Plus from HORIBA France SAS).…”

“…The full description of this method, as well as PAH reference measurements, is presented elsewhere. 39 All SERS measurements were recorded at room temperature with a Raman microscope (Xplora Plus from HORIBA France SAS). The laser beam was focused through a standard 50× objective with a 1.9 μm laser spot size.…”