Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (12): 2335-2341.doi: 10.3866/PKU.WHXB201410131

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Characterization of Mesoporous Silica Film Sensitized SERS Substrates Based on Evanescent-Wave Excitation

ZHAO Qiao1, LU Dan-Feng1, CHEN Chen1, QI Zhi-Mei1,2   

  1. 1. State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, P. R. China;
    2. State Key Laboratory of NBC Protection for Civilian, Beijing 102205, P. R. China
  • Received:2014-07-28 Revised:2014-10-13 Published:2014-11-27
  • Contact: LU Dan-Feng E-mail:dflu@mail.ie.ac.cn
  • Supported by:

    The project was supported by the Major National Scientific Instrument and Equipment Development Project of China (2011YQ0301240802), National Natural Science Foundation of China (61377064), Research Equipment Development Project of Chinese Academy of Sciences (YZ201106), and State Key Laboratory of NBC Protection for Civilian, China (SKLNBC2014-11).

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Abstract:

Sol-gel copolymer templated mesoporous silica (MPS) films of ~40 nm thickness were fabricated on the 50-nm-thick gold films sputtered on glass substrates. A top monolayer of gold nanoparticles (GNPs) was subsequently self-assembled on the MPS film to form an Au/MPS/GNPmultilayer structure for surface-enhanced Raman scattering (SERS) spectroscopy based on evanescent wave excitation. The open-pore structure of the MPS films, which was conducive to the rapid diffusion of small molecules into the film, was observed by scanning electron microscopy. Simulation using finite difference time domain (FDTD) solutions indicates that the evanescent field between the Au film and GNP layer of the Au/MPS/GNP substrate can be significantly enhanced under the surface plasmon resonance (SPR) condition. Owing to the complete spatial overlap, this enhanced field enables to superefficiently excite SERS signals from small molecules adsorbed in the MPS film. Moreover, the MPS film can effectively prevent the direct metal-molecule interaction, making the SERS signal immune to the interference by the metal. The SERS effect of the Au/MPS/GNP substrate loaded with Raman-active Nile blue (NB) molecules was investigated at 785 nm excitation wavelength with the Kretschmann configuration, and the experimental results were compared with those obtained using theAu/GNP substrate.With theAu/MPS/ GNP substrate very strong Raman signals were detected on the prism and air sides, respectively, under the SPR condition. The air-side Raman peak at 586 cm-1 is 40 times as high as that with the Au/GNP substrate. This enhancement is attributed to the open-pore MPS film. The further measurements reveal a positive correlation between the air-side Raman peak intensity and the NB concentration of the solution sample, giving a sign that the Au/MPS/GNP substrate could be used for quasi-quantitative analysis.

Key words: Open-pore mesoporous silica film, Evanescent wave excitation, Prism-side and air-side Raman signals, Quasi-quantitative analysis