Rhodamine 6G (R6G) is one of the most widely used dyes for application in dye lasers and as a fluorescence tracer. R6G also serves as a model dye to investigate the nature of the surface-enhanced Raman scattering (SERS) effect.
Study: Nanogol-coated poly(DEGDMA) microparticles as surface-enhanced Raman scattering substrates for DNA detection. Image credit: Leigh Prather/Shutterstock.com
In a paper published in the Journal of Physics D: Applied Physics, a novel platform based on poly(diethylene glycol dimethacrylate) (DEGDMA) microparticles decorated with gold nanoparticles (AuNPs) was used as an enhanced Raman scattering (SERS) substrate on the surface The AuNPs-decorated microparticles showed significant SERS enhancement in the R6G Raman signal compared to their bare counterparts.
For excitations at 532, 633, and 785 nm, the near-infrared showed the highest substrate enhancement and exceptional spatial uniformity and temporal stability. The practical application of the fabricated SERS substrate was demonstrated by the detection of DNA in the parasite Giardia lamblia
SERS substrates for Raman spectroscopy
Raman spectroscopy uses the interaction of light with matter and helps detect the characteristic vibrations and molecular composition of matter. SERS enhances the Raman intensity as a function of the interaction of the excitation light with the plasmons of the nanostructure.
SERS serves as a sensitive analytical method to detect chemically and biologically important species. Despite the essential role of SERS in clinical diagnosis, biochemistry, and toxin detection, active SERS materials that offer good Raman enhancement with high stability and reproducibility remain a challenge.
Although copper (Cu), silver (Ag), and Au were earlier as suitable metals, Au-based SERS substrates were widely used in previous studies to enhance the Raman signal. The wavelength region for SERS depends on the material. However, modifying the shape, size and morphology of the substrate helps to tune the wavelength requirement.
Metal-coated, SERS-active nanostructures based on non-metallic substrates have recently been explored for various sensing methods. The main advantage of using non-metallic materials is to obtain large surface area SERS substrates. To this end, polymerization is advantageous to prepare the SERS surface template.
R6G is widely used as a laser medium and fluorescence tracer. Previous reports mentioned that poly(glycidyl methacrylate-ethylene dimethacrylate) monolithic rods immobilized with AgNPs served as a SERS substrate to detect R6G. Similarly, the same monolithic polymer decorated with AuNPs showed high sensitivity in SERS measurements.
Poly nanogold-capped (DEGDMA) microparticles as SERS substrates
The present work fabricated and characterized a novel SERS-active substrate based on AuNP-capped poly(diethylene glycol dimethacrylate) (DEGDMA) microparticles. These microparticles were prepared by gamma radiation-initiated polymerization without using an initiator or stabilizer.
The SERS enhancement properties of the AuNP-decorated polymeric microparticles were demonstrated using an aqueous solution of R6G that served as an active Raman target. The performance of the SERS substrate was analyzed, including SERS enhancement factor, Raman excitation wavelength, spatial uniformity, temporal stability, and laser power dependence.
The Raman spectrum of R6G showed Raman bands at 611, 770, and 1182 inverse cm corresponding to the C–C–C ring vibration mode (in-plane), the C–H bending mode (out-of-plane), and the C. – Bending in H (in the plane), respectively. In addition, the inverse band at 1311 cm corroborated the NH bending mode, and the inverse Raman bands at 1362, 1511, and 1648 cm were related to the CC stretching mode in the R6G molecule.
The compatibility of the AuNP-capped poly(DEGDMA) composite substrate for SERS was analyzed by DNA detection using probe and target DNA molecules of the β-giardin gene in the parasite Giardia lamblia. The results revealed that the detected peaks followed native Raman bands of adenine (A), guanine (G), cytosine (C) and thymine (T) bases, previously reported in the literature.
conclusion
In summary, a novel SERS substrate based on AuNP-decorated poly(DEGDMA) microspheres was fabricated by polymerization, initiated by gamma radiation. Study of the SERS enhancement and plasmonic properties of the AuNP-capped poly (DEGDMA) composite substrate revealed good SERS sensitivity, demonstrated by the detection of 20 micromoles per liter concentration of R6G dye with analytical enhancement factor (AEF) SERS of 4.4 x 103.
Furthermore, the AuNP-decorated poly(DEGDMA) SERS substrate was stable for up to two months. The capability of the prepared SERS substrate for DNA detection was demonstrated using probe and target DNA sequences of the β-giardin gene of the parasite Giardia lamblia.
The results revealed that the AuNP-capped poly(DEGDMA) composite substrate is a promising SERS platform for DNA detection and a potential SERS substrate for biosensing application.
reference
Mahmood, MH, Jaafar, A., Himics, L., Péter, L., Rigó, I., Zangana, S., Bonyár, A., Veres, M. (2022). Nanogold-encapsulated poly (DEGDMA) microparticles as surface-enhanced Raman scattering substrates for DNA detection. Physics Magazine D: Applied Physics. https://iopscience.iop.org/article/10.1088/1361-6463/ac7bba
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