Use of Graphene and Gold Nanorods as Substrates for the Detection of Pesticides by Surface Enhanced Raman Spectroscopy

Abstract

This study aimed to use gold nanorods and graphene as key materials to fabricate high-performance substrates for the detection of pesticides by surface enhanced Raman spectroscopy (SERS). Three types of pesticides (azinphos-methyl, carbaryl, and phosmet) were selected. Gold nanorods have great potential to be used as a SERS substrate because it is easy to tune the surface plasmon resonance of the nanorods to the laser excitation wavelength of Raman spectroscopy. Graphene is a promising nanoscale material that can be used for supporting metal nanostructures. Three types of novel SERS substrates were fabricated, including graphene-gold film-gold nanorod (G-Au-AuNR) substrate, gold film-gold nanorod (Au-AuNR) substrate, and graphene coupled with gold nanorods (G-AuNR). The results demonstrate that G-Au-AuNR substrates exhibited the strongest Raman signals of the selected pesticides, followed by the Au-AuNR substrates. G-AuNR exhibited the weakest Raman signals, and no characteristic spectral features of the analytes were obtained. A partial least-squares method was used to develop quantitative models for the analysis of spectral data (R = 0.94, 0.87, and 0.86 for azinphos-methyl, carbaryl, and phosmet, respectively). The G-Au-AuNRs substrate was able to detect all three types of pesticides at the parts per million level with limits of detection at around 5, 5, and 9 ppm for azinphos-methyl, carbaryl, and phosmet, respectively. These results indicate that combining gold nanorods and graphene has great potential in the fabrication of sensitive, lightweight, and flexible substrates for SERS applications to improve food safety.

Lighting Up the Raman Signal of Molecules in the Vicinity of Graphene Related Materials

“…41−43 This effect depends on several factors, such as the type of metal, the metal surface morphology, graphene thickness, 42,44 etc. Graphene has been integrated with various shapes of gold nanoparticles for SERS enhancement, such as arrays of gold nanodisks, 41 photonic-crystal nanocavities, 45 gold nanorods, 46 and silver, copper, or gold nanospheres 47 The effectiveness of graphene in stabilizing the SERS system of thermally grown Au and Ag nanoparticles and achieving strong enhancement has been proven, 32,47 as shown in Figure 6a,b. These studies showed that the detection limit is ∼100-fold larger with graphene coupled with the SERS system.…”

Graphene–Gold Nanoparticles Hybrid—Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor

“…An experiment by Wang et al [197] proved that ~7 nm thick Au films are the perfect SERS substrates among the different thickness of Au films, decorated on the monolayer graphene for the characterization of low concentration rhodamine molecules, providing the strongest Raman signals for molecules with the weakest photoluminescence background. All of these extraordinary advantageous properties make graphene–Au nanocomposites the perfect substrate for SERS measurements, as it has been extensively instigated in versatile applications, including sensing and molecular diagnostics, biomedical applications, agriculture, food adulteration [202], and so on. This hybrid has also been verified for the detection of single molecule interactions [184], identification of pathogenic microorganisms [203] and biomolecules [204,205], nucleic acids [206], and cancer cells [207], and even in the detection of explosives and chemical warfare agents [208].…”

“…Nguyen et al [202] have fabricated a high performance SERS substrate by using graphene–Au films–AuNRs for the detection of three pesticides namely azinphos-methyl, carbaryl, and phosmet by SERS with LODs of approximately 5, 5, and 9 ppm, respectively. The LODs of carbaryl and phosmet meet the FAO/WHO- and EU-defined maximum residue limits, which make it a potential method in food safety applications.…”

A new SERS substrate based on silver nanoparticle functionalized polymethacrylate monoliths in a capillary, and it application to the trace determination of pesticides

“…The comparisons of the SERS column for quantitative detection of phosmet in current work with the results in literature using other SERS substrates are listed in Table 1. It is summarized the present reported other techniques for phosmet detection, including surface plasmon resonance sensor [33], gas chromatography with flame photometric detection [34], gas chromatography-tandem mass spectrometry [1], enhanced chemiluminescence enzyme linked immunosorbent assay [35] and SERS substrates, including Klarite substrates [31], Q-SERS substrates ™ [36], graphene-gold film-gold nanorod [37], solid-phase extraction-SERS [20], gold nanoparticles functionalized glycidyl methacrylate-ethylene dimethacrylate [21] substrates. It is clearly observed that the SERS column we reported has a best position among the SERS substrates, and is as good as other techniques.…”