Prof. Xie's Group
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Semiconductor Materials Research Lab
Figure 1. a, Schematic illustration of the hybrid system for single molecular SERS. b, x-z view of electric field distribution around the Au nanostructures by FDTD simulation. Incident light wavelength 633nm. Scale 200nm. c, x-y view of electric field distribution at z=100nm. Scale 200nm


  1. Wang, P.; Zhang, W.; Liang, O, et al. Giant Optical Response from Graphene-Plasmonic System. ACS Nano, 6, 6244 (2012);
  2. Wang P, Liang O, Zhang W, et al. Ultra‐Sensitive Graphene‐Plasmonic Hybrid Platform for Label‐Free Detection. Advanced Materials, 25(35), 4918 (2013).

Semiconductor Materials Research Laboratory, Department of Materials Science and Engineering, University of California, Los Angeles

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van der Waals-expressed plasmon-enhanced molecule-scale bio-sensing platform


The Xie Research Group is interested in the biological applications of hybrid platform VPMB (van der Waals-expressed plasmon-enhanced molecule-scale bio-sensing platform). The hybrid platform is composed of a metal nano-structured SERS substrate superimposed of two-dimensional van der Waals materials. The metal nano-structured surface generates very high plasmonic enhancement factor to realize ultra-sensitive detection, while van der Waals materials offer the flexibility to modify surface to extend the application of the platform.

Typical platform well researched in Xie lab is the single layer graphene - gold nano-pyramid (also referred as Au tip) array heterostructure. Such hybrid platform has three unique features compared with traditionally used nano-particle systems.

1) The chemically inert graphene surface protect the underneath metal surface from oxidation and degradation from commonly encountered chemical reactions, which could be refreshed for multiple use.

2) Graphene has Raman features that can be easily identified. Thus in SERS, graphene serves as a built-in hot spot marker to profile the EM field distribution of the underneath plasmonic substrate.

3) Graphene contributes to additional SERS enhancement factor of 10-100 of many bio-molecules due to chemical enhancement (CM) mechanism.

Various bio-species have been tested for the graphene-Au tip platform and single molecule detection capability has been demonstrated for molecules like dye, proteins and neurotransmitters. The platform also shows potentials in cell sensing. Future efforts in integrating the platform to an optical fiber will significantly extend the applications of the hybrid platform in both in vivo and in vitro diagnosis.












Figure 2.SERS of graphene on Au tips.