Graphene Oxide-Coated Metal–Insulator–Metal SERS Substrates for Trace Melamine Detection

Abstract

Surface-enhanced Raman spectroscopy (SERS) has long been an ultrasensitive technique for trace molecule detection. However, the development of a sensitive, stable, and reproducible SERS substrate is still a challenge for practical applications. Here, we demonstrate a cost-effective, centimeter-sized, and highly reproducible SERS substrate using the nanosphere lithography technique. It consists of a hexagonally packed Ag metasurface on a SiO2/Au/Si substrate. A seconds-lasting etching process of a self-assembled nanosphere mask manipulates the geometry of the deposited Ag metasurface on the SiO2/Au/Si substrate, which attains the wavelength matching between the optical absorbance of the Ag/SiO2/Au/Si substrate and the excitation laser wavelength as well as the enhancement of Raman signals. By spin-coating a thin layer of graphene oxide on the substrate, a SERS performance with 1.1 × 105 analytical enhancement factor and a limit of detection of 10−9 M for melamine is achieved. Experimental results reveal that our proposed strategy could provide a promising platform for SERS-based rapid trace detection in food safety control and environmental monitoring.

Extremely Sensitive SERS Sensors Based on a Femtosecond Laser-Fabricated Superhydrophobic/-philic Microporous Platform

“…7,8 Considering the advantages of noninvasive, fastdetection, and label-free means, 9 this technology is one of the most promising candidates for detecting highly low-concentration analytes. 10−12 It has been extensively applied in explosive detection, 13,14 precancer diagnosis, 15 food safety, 16−18 forensic analysis, 19 etc. In these cases, the target molecules are usually randomly dispersed in highly diluted solutions with concentrations as low as the pico/femtomolar level.…”

“…Surface-enhanced Raman scattering (SERS) is a phenomenon in which Raman signals can be significantly enhanced on well-designed plasmonic materials or structures. − Two main primary mechanisms, electromagnetic (EM) enhancement and chemical (CM) enhancement, are believed to be responsible for Raman signal enhancement. − The latter mechanism induced by the localized surface plasmon resonance is universally accepted. , Considering the advantages of noninvasive, fast-detection, and label-free means, this technology is one of the most promising candidates for detecting highly low-concentration analytes. − It has been extensively applied in explosive detection, , precancer diagnosis, food safety, − forensic analysis, etc. In these cases, the target molecules are usually randomly dispersed in highly diluted solutions with concentrations as low as the pico/femtomolar level.…”

Nanosphere Lithography-Enabled Hybrid Ag-Cu Surface-Enhanced Raman Spectroscopy Substrates with Enhanced Absorption of Excitation Light

“…However, excessively low surface tension would compromise the stability of the self-assembled structure. Therefore, achieving the proper surface tension of water is crucial in preparing high-quality PS monolayer masks [ 43 , 45 ]. In our experiments, we rigorously regulate the temperature to ensure precise control of the surface tension.…”

“…Therefore, the above process can only be realized by adding the appropriate amount of DI water to the Si substrate. Following the self-assembly process, the templated PS monolayer masks were transferred onto a glass substrate using the method described in our previous reports [ 40 , 43 ]. After the successful transfer of the templated mask onto glass substrates, the inductively coupled plasma (ICP) (GSE200Plus, Northern Microelectronics, Gateshead, UK) etching technique was employed to etch the PS nanospheres using O 2 plasma.…”

“…Various periodic nanostructures based on a polystyrene (PS) monolayer mask, such as nanosteps [ 40 ], nanohole arrays [ 41 ], and nanotriangle arrays [ 42 ], have been utilized to significantly enhance Raman signals. In our previous work, we successfully prepared SERS substrates with strong electromagnetic field enhancement at multiple wavelengths via NSL [ 40 , 43 , 44 ].…”