Nanoplasmonics and surface enhanced spectroscopy 

Nitrogen-doped graphene oxide nanocomposite with silver nanoparticles as a SERS detector
Menshova E.P.1, Dzhanabekova R.Kh.1, Ibrayev N.Kh.1, Seliverstova E.V.1
1 Institute of Molecular Nanophotonics, Karaganda Buketov University.
St. University, 28, 100024 Karaganda, Kazakhstan
E-mail: menshovayevgeniya@gmail.com

The creation of active substrates for Raman scattering is an urgent task for determining "trace" amounts of analytes. We prepared SERS-active substrates based on nitrogen-doped graphene oxide (NGO) with silver nanoparticles (NPs) and studied the Raman spectra of R6G on the composite surface.
The composite was synthesized by a 2-stage method based on an ammonia complex [1]. In the SEM images, the NGO sheets are covered with spherical Ag NPs, the size of which is 80 – 120 nm. It correlates with the data obtained on the absorption spectrum with a maximum at 490 nm.
Raman spectra (Confotec MR 520) showed that during the synthesis of the nanocomposite, a large number of topological defects are formed in graphene oxide. Also, the spectrum of the nanocomposite differs from the spectrum of NGO by the presence of additional peaks at 600 and 1800 cm–1, which are characteristic of the residual products of ammonia [2] and ascorbic acid [3].
The studied SERS-active substrates are capable of amplifying the R6G signal (10-5 mol) by a factor of 35.92 relative to the dye signal on NGO without Ag NPs. Even at a low dye concentration of 10-9 mol, peaks at 611, 771 and 1125 cm-1 can be identified, associated with in-plane and out-of-plane vibrations of the aromatic ring and C-H vibrations in the plane, as well as bands 1189, 1310, 1360, 1508, and 1649 cm–1 related to the stretching vibrations of aromatic С–С bonds [1]. We believe that the high sensitivity of detection is associated not only with the SERS effect, but also with additional sorption of the analyte.

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