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Significance Statement
Surface enhanced Raman spectroscopy (SERS) is one powerful method for trace detections and biochemical applications because of its ultra-sensitivity, and real-time analysis. Recently, nanosphere lithography (NSL) has been used to fabricate array of nanoscale noble metal particles with controlled size, shape and spacing.
Inspired by the NSL technique, one simplified method for fabricating three-dimensional nanofeature arrays for SERS substrates were explored by combining the self-assembly of nanoscale polystyrene (PS) spheres with subsequent Au film ion sputter coating modulation (Xiaotang Hu, Zongwei Xu*, et al., Fabrication of a Au-Polystyrene Sphere Substrate with Three-Dimensional Nanofeatures for Surface-Enhanced Raman Spectroscopy, Applied Surface Science 2015, Vol. 355: 1168-1174, doi:10.1016/j.apsusc.2015.07.215). The substrate’s nanoscale hot-spot features were controlled using the Au coating film thickness regulation and focused ion beam (FIB) nano-patterning regulation methods. Scanning electron microscopy and Raman spectroscopy were employed to analyze the substrate morphology and the enhancement mechanism of the three-dimensional SERS substrate.
Polystyrene microspheres with diameters of 151 nm and 360 nm were coated with Au layers of different thicknesses ranging from 10 nm to 270 nm. The configuration of the Au-Polystyrene spheres can be regulated to hexagonal close packing with nanoscale V-shaped slits with a 10 to 20 nm gap pattern. Nanoscale Au particles and clusters with a clear outline covered the surface of the PS spheres, in which the multiple-scale structures increase the specific surface area of the SERS-active substrate. Nanoscale cracks formed on the smaller Au-Polystyrene spheres with a diameter of 151 nm, which also exhibited strong SERS activity. The substrate surface temperature regularly increased after Au coating, and the thermal expansion coefficient difference and Polystyrene glass transition properties were studied to explain the Au-Polystyrene spheres nanofeature configuration development.
Research results showed that the developed Au-Polystyrene spheres SERS nanofabrication method is inexpensive, three-dimensional and highly ordered array, which can show great Raman scattering enhancement characteristics.
Journal Reference
Applied Surface Science, Volume 355, 2015, Pages 1168–1174.
Xiaotang Hu, Zongwei Xu, Kang Li, Fengzhou Fang, Liyang Wang.
State Key Laboratory of Precision Measuring Technology and Instruments, Centre of MicroNano Manufacturing Technology, Tianjin University, China.
Abstract
Methods for fabricating three-dimensional nanofeature arrays for surface-enhanced Raman spectroscopy (SERS) substrates were explored by combining the self-assembly of nanoscale polystyrene (PS) spheres with subsequent Au film ion sputter coating modulation. The substrate’s nanoscale hot-spot features were controlled using the Au coating film thickness regulation and focused ion beam (FIB) nano-patterning regulation methods. Scanning electron microscopy and Raman spectroscopy were employed to analyze the substrate morphology and the enhancement mechanism of the three-dimensional SERS substrate. Polystyrene microspheres with diameters of 151 nm and 360 nm were coated with Au layers of different thicknesses ranging from 10 nm to 270 nm. The configuration of the Au-Polystyrene spheres can be regulated to hexagonal close packing with nanoscale V-shaped slits with a 10–20 nm gap pattern. Nanoscale Au particles and clusters with a clear outline covered the surface of the PS spheres, in which the multiple-scale structures increase the specific surface area of the SERS-active substrate. Nanoscale cracks formed on the smaller Au–PS spheres with a diameter of 151 nm, which also exhibited strong SERS activity. The substrate surface temperature regularly increased after Au coating, and the thermal expansion coefficient difference and PS glass transition properties were studied to explain the Au-Polystyrene spheres nanofeature configuration development. The fabricated Au-Polystyrene spheres SERS feature is a type of three-dimensional and highly ordered array, which can show Raman scattering characteristics by providing a SERS enhancement factor of greater than 107.
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