C18-Modified Metal-Colloid Substrates for Surface-Enhanced Raman Detection of Trace-Level Polycyclic Aromatic Hydrocarbons in Aqueous Solution

Abstract

Metal colloids immobilized on a glass support substrate are modified with a self-assembled alkylsilane (C18) layer to promote adsorption of polycyclic aromatic hydrocarbons from aqueous solutions. Detection of these compounds from low concentration solutions is accomplished by using surface-enhanced Raman scattering (SERS). SERS spectra of pyrene adsorbed to C18-modified immobilized silver colloids are dominated by Raman bands that are not consistent with pyrene and indicate that pyrene undergoes a chemical reaction at the surface. The origins of this surface product are investigated, and it is determined that silver and oxygen are required to form the product, whose Raman spectrum is consistent with oxidation to a quinone. When a C18-modified gold-colloid substrate is used, Raman scattering consistent with unreacted pyrene is observed. The adsorption and detection of pyrene adsorbed from low (2 ppb) concentration aqueous solutions onto C18-modified gold-colloid substrates is reported; naphthalene and phenanthrene are detected at approximately 5 ppb. Adsorption kinetics are rapid (<5 min), and the concentration-dependent SERS response is consistent with a Langmuir isotherm.

Activation of Nanoparticles by Biosorption for E. coli Detection in Milk and Apple Juice

“…The higher intensity of the SERS spectrum of bacteria was attributed to surface enhancement due to the presence of the silver colloid [27]. Such behavior has been reported in the literature for many other molecules and biomolecules [19,20,28,29].…”

Electrochemical and photocatalytic reactions of polycyclic aromatic hydrocarbons investigated by raman spectroscopy

“…Recently it has been demonstrated that PAH adsorption on nanostructured gold surfaces may cause their oxidative degradation. 16,17 When the applied potential is made more positive than + 0.9 V, Raman spectral changes indicate the electrochemical oxidation of adsorbed anthracene.…”

“…Recently it has been demonstrated that PAH adsorption on nanostructured gold surfaces may cause their oxidative degradation. 16,17 When the applied potential is made more positive than + 0.9 V, Raman spectral changes indicate the electrochemical oxidation of adsorbed anthracene.New Raman bands, characteristic of oxidized species, are observed at 1032, 1600 and 1665 cm -1 . Changes are also seen in the high frequency region of the spectra, where characteristic vibrational modes of aromatic and aliphatic CH stretching appear.…”

Self‐Assembled Au Nanoparticles as Substrates for Surface‐Enhanced Vibrational Spectroscopy: Optimization and Electrochemical Stability

“…The frequency of the LSP resonance is tunable by the surface morphology. [10][11][12][13][14][15][16][17][18] A variety of substrates that support SERS are being explored by various groups. [1,4,19] Typically, an ideal SERS substrate for analytical applications should be robust, easy to prepare and use, provide a large enhancement of the interference-free Raman signal of the analyte, and present a high degree of reproducibility.…”

“…[15,28] This kind of approach for SERS-substrate preparation has recently attracted much attention. [11,[28][29][30][31][32][33][34] The self-assembled structures are fabricated by alternately dipping the initially flat surface into solutions containing a bifunctional cross-linker and the NPs. The resultant morphology can be tuned by the desired number of NP depositions, which tailors the substrate performance for SERS.…”