Oxidation effects on the SERS response of silver nanoprism arrays
Roberto pilot
Consorzio INSTM and University of Padova
I graduated and achieved my Ph.D. at the University of Padova, where I carried out a theoretical structure-to-property investigation of the nonlinear optical properties of charge transfer molecules. Afterwards, as a postdoc at the Katholieke Universiteit Leuven, I studied charge/energy transfer processes in multi-chromophoric molecules, by means of femtosecond transient absorption and time resolved fluorescence. Lately, at the Padova University, I have focused on the characterization of SERS substrates in view of their application as sensors for chemical species. Another recent research field explored is the computational investigation of the excited state polarizability of squaraine dyes.
Abstract
Silver nanostructures are widely employed for Surface Enhanced Raman Scattering (SERS) characterizations owing to their excellent properties of field confinement in plasmonic resonances. However, the strong tendency to... [ view full abstract ]
Silver nanostructures are widely employed for Surface Enhanced Raman Scattering (SERS) characterizations owing to their excellent properties of field confinement in plasmonic resonances. However, the strong tendency to oxidation at room temperature of these substrates may represent a major limitation to their performances.[1]
In the present work, we investigated in detail the effects of oxidation on the SERS response of a peculiar kind of Ag nanostructured substrates, i.e., bi-dimensional ordered arrangements of Ag nanoprisms synthesized by nanosphere lithography. Particularly, wavelength-scanned SERS measurements were performed on Ag nanoprism arrays (NPA) oxidized at three different levels (non-oxidized, mildly and strongly oxidized) and thereafter functionalized with benzenethiol, in order to determine the SERS enhancement curves as a function of the excitation wavelength around the dipolar plasmonic resonance of the arrays. The experimental results were compared with those obtained by finite elements method simulations. With this approach, we were able to decouple the effects of spectral shift and decrease of the maximum value of the SERS enhancement observed for the different oxidation conditions.[2] From a practical standpoint we can state that the tendency of silver towards oxidation does not preclude the use
of Ag NPAs as platforms for SERS sensing with thiol- terminated molecules. Benzenethiol was found to effectively bind to the oxidized NPA surface as it does to the metallic NPAs: the SERS enhancement reduction demonstrated in
the oxidized samples amounts only to a factor of 2.5 and therefore does not alter significantly the NPA performances required for applications. As an example, in the Figure below we show the extinction spectrum (blue line), the experimental SERS enhancement profile (dots) and its fit (orange line) for the non-oxidized sample.
Figure. Non-oxidized sample: absorption spectrum (blue line), experimental SERS enhancement profile (dots) and its fit (orange line).
[1] Y. Han et al.; Anal. Chem., (2011), 83, 5873.
[2] N. Michieli, R. Pilot et al.; RSC Adv. (2017), 7, 369.
Authors
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Niccolò Michieli
(University of Padova)
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Roberto pilot
(Consorzio INSTM and University of Padova)
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Valentina Russo
(University of Padova)
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Carlo Scian
(University of Padova)
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Francesco Todescato
(University of Padova)
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Raffaella Signorini
(University of Padova)
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Stefano Agnoli
(University of Padova)
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Tiziana Cesca
(University of Padova)
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Renato Bozio
(University of Padova)
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Giovanni Mattei
(University of Padova)
Topic Area
Enhanced spectroscopy and sensing
Session
OS1a-1 » Enhanced spectroscopy and sensing (15:00 - Monday, 1st October, ROOM 1)
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