Electric field enhancement in a self-assembled 2D array of silver nanospheres
- Department of Physics and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403 (United States)
- Environ. Molecular Sci. Lab., Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)
We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of 9/3.7 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4{sup ′}-dithiol (BPDT) molecules adsorbed onto different sites of the network. Reproducible, bright, and low-background SERS spectra are recorded and assigned on the basis of density functional theory calculations in which BPDT is chemisorbed onto the vertex of a finite tetrahedral Ag cluster consisting of 20 Ag atoms. A notable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ∼200–2200 cm{sup −1} region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 10{sup 6} are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.
- OSTI ID:
- 22413270
- Journal Information:
- Journal of Chemical Physics, Vol. 141, Issue 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BIPHENYL
CHEMISORPTION
DENSITY FUNCTIONAL METHOD
ELECTRIC FIELDS
EMISSION SPECTROSCOPY
MOLECULES
PARTICLES
PHOTOELECTRON SPECTROSCOPY
PHOTOEMISSION
PHOTONS
RAMAN EFFECT
SIGNALS
SILVER
SIMULATION
SPECTRA
SUBSTRATES
TRANSMISSION ELECTRON MICROSCOPY
VIBRATIONAL STATES