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Issue 8, 2017
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Detection of electron tunneling across plasmonic nanoparticle–film junctions using nitrile vibrations

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Abstract

The significant electric field enhancements that occur in plasmonic nanogap junctions are instrumental in boosting the performance of spectroscopy, optoelectronics and catalysis. Electron tunneling, associated with quantum effects in small junctions, is reported to limit the electric field enhancement. However, observing and quantitatively determining how tunneling alters the electric fields within small gaps is challenging due to the nanoscale dimensions and heterogeneity present experimentally. Here, we report the use of a nitrile probe placed in the nanoparticle–film gap junctions to demonstrate that the change in the nitrile stretching band associated with the vibrational Stark effect can be directly correlated with the local electric field environment modulated by gap size variations. The emergence of Stark shifts correlates with plasmon resonance shifts associated with electron tunneling across the gap junction. Time dependent changes in the nitrile band with extended illumination further support a build up of charge associated with optical rectification in the coupled plasmon system. Computational models agree with our experimental observations that the frequency shifts arise from a vibrational Stark effect. Large local electric fields associated with the smallest gap junctions give rise to significant Stark shifts. These results indicate that nitrile Stark probes can measure the local field strengths in plasmonic junctions and monitor the subtle changes in the local electric fields resulting from electron tunneling.

Graphical abstract: Detection of electron tunneling across plasmonic nanoparticle–film junctions using nitrile vibrations

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Publication details

The article was received on 29 Nov 2016, accepted on 20 Jan 2017 and first published on 20 Jan 2017


Article type: Paper
DOI: 10.1039/C6CP08168A
Citation: Phys. Chem. Chem. Phys., 2017,19, 5786-5796

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    Detection of electron tunneling across plasmonic nanoparticle–film junctions using nitrile vibrations

    H. Wang, K. Yao, J. A. Parkhill and Z. D. Schultz, Phys. Chem. Chem. Phys., 2017, 19, 5786
    DOI: 10.1039/C6CP08168A

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