May 23, 2014
Gold nanodisks for highly sensitive SERS substrates
Surface-enhanced Raman scattering (SERS) is an information-rich method that detects analytes at extremely low concentrations. With this advantage, the goal now is to fabricate highly reproducible SERS substrates that are optimized to provide the largest enhancement of the electromagnetic (EM field). Reporting in Nanotechnology, researchers have developed an assembly strategy for practical SERS detection that not only achieves this, but also integrates large-scale production, high sensitivity and reproducibility.
Researchers from Soochow University, China, have fabricated large-scale Au nanodisk arrays on a silicon substrate using X-ray interference lithography (XIL) and electron-beam vapour deposition. The arrays exhibit a uniform and reproducible surface enhancement on the Raman scattering signal. This enables the detection of Rhodamine 6G (R6G) as low as 10–8 M with an enhancement factor of 106.
The diameters of the nanodisks and the inter-disk distance can be simply tuned by varying the exposure time and the development time in the XIL process. The EM field of the Au nanodisk arrays with different diameters is also simulated by the finite difference time domain (FDTD) method to further understand the enhancement of the SERS intensity in this work. The Au nanodisk with a diameter of 160 nm exhibits the highest intensity of the SERS signal for R6G. This is confirmed by the FDTD simulation and is associated with the Raman signal enhancement.
Convenient and reproducible
This convenient nanofabrication technique to fabricate large-scale gold nanodisk arrays for high-performance SERS-active substrates can overcome the uneven radial distribution and generate high reproducibility in the Raman signal. Au/Ag double-layer bimetal nanodisk arrays are also easily fabricated by this method. This can give rise to more significant increases in the enhancement factor for the SERS spectroscopy of R6G than the Au nanodisk arrays themselves under the same experimental conditions.
The XIL nanofabrication method provides a facile strategy to fabricate practical, large-area SERS substrates capable of high sensitivity and excellent reproducibility, which can facilitate routine SERS detection.
More information can be found in the journal Nanotechnology 25 245301.
About the author
Pingping Zhang is a PhD candidate in Xuhui Sun’s Group in the Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, China. The group research interests are focused in the area of nanomaterials and their applications in nanoelectronics, sensors and energy harvesting. The group is also interested in the development and application of synchrotron radiation techniques in nanoscale materials.