Self-patterning of graphene-encapsulated gold nanoparticles for surface-enhanced Raman spectroscopy
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Research Letter
Self-patterning of graphene-encapsulated gold nanoparticles for surfaceenhanced Raman spectroscopy Yuan Li, Metallurgical and Materials Engineering Department (MTE), Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, AL 35487, USA Kelly Burnham, NSF-REH Fellow, Northridge High School, Tuscaloosa, AL 35406, USA John Dykes, Department of Mathematics, NSF-REU Fellow, The University of Alabama, Tuscaloosa, AL 35407, USA Nitin Chopra, Metallurgical and Materials Engineering Department (MTE), Department of Biological Sciences, Department of Chemistry, Center for Materials for Information Technology (MINT), The University of Alabama, Tuscaloosa, AL 35487, USA Address all correspondence to Dr. Nitin Chopra at [email protected] (Received 7 September 2017; accepted 8 January 2018)
Abstract The main challenges of developing advanced surface-enhanced Raman spectroscopy (SERS) sensors lie in the poor reproducibility, low uniformity, and the lack of molecular selectivity. In this paper, we report a facile and cost-effective approach for the large-scale patterning of graphene-encapsulated Au nanoparticles on Si substrate as efficient SERS sensors with highly-improved uniformity, reproducibility, and unique selectivity. The materials production was accomplished via an industry-applicable galvanic deposition—annealing—chemical vapor deposition approach, followed by a final plasma treatment. Our study provides a facile approach to the fabrication of uniform SERS substrate and further prompts the practical progress of SERS-based chemical sensors.
Introduction Surface-enhanced Raman spectroscopy (SERS) has been considered to be one of the promising techniques in trace-level molecular detection.[1] By exciting the surface plasmon resonance on noble metal substrates, the Raman signals for low concentration molecules can be significantly enhanced. It was reported that the enhancement factor (EF) can be as high as 105–109.[2,3] Coinage metals such as Au and Ag were usually used as the preferred SERS substrate in the form of rough surface and nanoscale structures.[4–6] The enhancement of Raman signal is originated from the interaction between the metallic substrate and absorbed/attached target molecules under the electromagnetic field generated by the illumination-excited substrate, attributing to the so-called localized surface plasmon resonance (LSPR) from the surface of Au or Ag nanostructures.[7] The main challenges in practical applications of SERS sensors lie in their low uniformity, poor reproducibility, and limited selectivity. LSPR was found to be tunable by controlling the size, shape, and distribution of nanoparticles,[8,9] as well as using effective supporting substrate.[10,11] Accordingly, besides the development of various new techniques such as selfassembly, nano-pattering, and heterostructure design,[12–14] new 2D materials, such as graphene, was recently employed as a promising substrate for uniformly dispersing the coinage metal nanoparticles to overcome those short
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