Surface Enhance Raman Spectroscopy (SERS) is a well-known technique used to analyze solutions of various substances that are at very low concentration levels. To create plasmonic resonance, many researchers have used Au nanoparticles decorated on SERS. Although Au nanoparticles offer high efficiency and high stability, they are expensive. An inexpensive noble metal with high numbers of free electrons, Ag nanoparticles has become an interesting alternative. However, Ag has a major drawback because it is easily oxidized. Therefore, this research aims to combine the good properties between Au and Ag nanoparticles for Raman signal enhancement. A low-cost laser marking technique was used to engrave aluminum surface. The Au/Ag nanoparticles were co-sputtered on the aluminum template with decorating times ranging from 30-360 s. FE-SEM was used to characterize the nanostructure of the nanoparticles on SERS. Hydrophobic properties of the SERS surface were identified by contact angle measurement. A Raman spectrometer was used to measure the intensity of the enhanced Raman signal. From the results, the decorating time that provided the highest contact angle and highest Raman intensity enhancement was 270 s for both Ag and Au/Ag nanoparticles. The limit of detection of Ag and Au/Ag aluminum SERS was 10-8 M for Rhodamine-6 G. The enhancement factor for Ag aluminum SERS was slightly greater than that for Au/Ag aluminum SERS, as expected. After 60 days of shelf-life testing, Ag aluminum SERS presented the highest Raman enhancement. However, the Raman signal from Ag aluminum SERS dramatically decreased, afterwards. On the other hand, Au/Ag aluminum SERS showed a constant ability to enhance the Raman signal for as long as 150 days.
Keywords: Raman scattering; laser-engrave; Au/Ag nanoparticle SERS; 3D hybrid SERS; sputtering
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E-mail: saksorn.limwichean@nectec.or.th
