A Simple SERS-Based Trace Sensing Platform Enabled by AuNPs-Analyte/AuNPs Double-Decker Structure on Wax-Coated Hydrophobic Surface

Abstract

In this work, a simple and versatile SERS sensing platform enabled by AuNPs-analyte/AuNPs double-decker structure on wax-coated hydrophobic surface was developed using a portable Raman spectrometer. Wax-coated silicon wafer served as a hydrophobic surface to induce both aggregation and concentration of aqueous phase AuNPs mixed with analyte of interest. After drying, another layer of AuNPs was drop-cast onto the layer of AuNPs-analyte on the substrate to form double-decker structure, thus introducing more “hot spots” to further enhance the Raman signal. To validate the sensing platform, methyl parathion (pesticide), and melamine (a nitrogen-enrich compound illegally added to food products to increase their apparent protein content) were employed as two model compounds for trace sensing demonstration. The as-fabricated sensor showed high reproducibility and sensitivity toward both methyl parathion and melamine detection with the limit of detection at the nanomolar and sub-nanomolar concentration level, respectively. In addition, remarkable recoveries for methyl parathion spiked into lake water samples were obtained, while reasonably good recoveries for melamine spiked into milk samples were achieved. These results demonstrate that the as-developed SERS sensing platform holds great promise in detecting trace amount of hazardous chemicals for food safety and environment protection.

PVP‐mediated galvanic replacement growth of AgNPs on copper foil for SERS sensing

“…Surface‐enhanced Raman scattering (SERS) derives from tremendous electromagnetic enhancement of noble nanostructured materials (Au, Ag etc.) in the excited photoelectric field, which enables a sharp increase in Raman signals of organic molecules near the nanostructured region [1–3]. In addition, the specific finger‐prints (SERS spectra) of the given molecules offer it an excellent anti‐disturbance capacity towards the analytes of interests [4].…”

“…For SERS sensors, it is of paramount significance for the fabrication of SERS substrate in effective detection of targets. In the past, there were intensive reports on the preparation of colloidal noble nanoparticles (CNNPs) with various shapes and sizes for the SERS detection of targets in solutions [3, 8]. Many SERS ‘hot spots’ can be formed by the assembly of CNNPs, further giving it good sensitivity.…”

Nanotechnology in food and water security: on-site detection of agricultural pollutants through surface-enhanced Raman spectroscopy

“…For the detection of melamine, SERS is also used as a portable method with simple or no sample preparation methods. Wu et al [ 94 ] determined the melamine and methyl parathion (MP) from the lake water and milk samples via SERS using a portable Raman spectrometer. AuNPs were used as SERS substrate and a wax-coated silicon wafer as a hydrophobic surface to enhance the aggregation of the AuNPs.…”

Trace analysis of organic compounds in foods with surface‐enhanced Raman spectroscopy: Methodology, progress, and challenges

“…Since most of the commercially available portable Raman spectrometers are designed for the analysis of bulk samples, it is unlikely that these instruments would have adequate sensitivity for detecting hazardous compounds at ppb levels in complex food systems without purification and concentration. However, there have been an increasing number of publications indicating the feasibility of applying portable Raman spectrometers for rapid analysis of trace compounds in foods, such as the detection of as low as 1 mg/L of pigments in foods using Au nanoparticles as SERS substrate (Chen et al., ), 22.5 μg/kg of triazophos on apple peels using adhesive tape incorporating Ag nanoparticles (Gong et al., ), and 2.5 ppm of melamine in milk with a double‐layer structure of Au nanoparticles (Wu et al., ) and quantification of 10 to 100 μg/L sulfapyridine (an antibiotic) in milk using carbon nanotubes incorporating Ag nanoparticles (Moreno, Adnane, Salghi, Zougagh, & Ríos, ). In addition, the combination of sample separation and/or concentration techniques with SERS shows potential for rapid in situ analysis of hazardous compounds in foods with portable Raman spectrometers.…”