The effects of operating parameters on the morphology, and the SERS of Cu NPs prepared by spark discharge deposition
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The effects of operating parameters on the morphology, and the SERS of Cu NPs prepared by spark discharge deposition Mohamed Abd El‑Aal1,2 · Takafumi Seto2 · Atsushi Matsuki3 Received: 27 April 2020 / Accepted: 24 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Copper nanoparticles were fabricated and deposited on a glass substrate by spark discharge of copper electrode under different atmospheric conditions for SERS application. An interesting dependence of the deposition process and the formation of different particle structures on the deposition atmospheres were observed. Static air atmosphere ensured the deposition of the Cu particles on the glass surface by avoiding the repulsion between charged Cu particles and the surface of the glass through the formation of CuO, which acts as a seed mediated for nanorods formation. The average diameter of the as-deposited Cu rods was measured by the TEM to be 39 nm. Thermal annealing of the film up to 200 °C resulted in a reduction in the diameter of the nanorods as well as an increase in the rod density. A water solution of dye molecule (crystal violet) with a concentration of 1 × 10–6 to 1 × 10–9 M was dropped on the prepared Cu substrate. Raman signals from dye molecule were detected and their intensities changed according to deposition time, post-annealing temperature and dye concentration. A significant increase in the Raman scattering signal of a dye molecule was observed in the film fabricated at 30 min of deposition time and post-annealed temperature of 200 °C for 1 h. This substrate provides a maximum SERS intensity with a detection limit of 1 × 10–8 M, with an enhancement factor of 3.9 × 103. The SERS performance of the substrates was correlated well with the change in their surface morphologies. Keywords Cu nanostructures · Spark discharge · SERS · Crystal violet
1 Introduction Surface-enhanced Raman scattering (SERS) is a powerful analysis technique, which provides rich fingerprint information on molecules with a high sensitivity down to a single molecular level [1]. Therefore, it has been widely employed in several applications such as gas sensing [2], biosensing [3], medical diagnosis [4], environmental monitoring [5], food safety [6], explosives analysis [7], catalysis [8], and other fields [9, 10]. To date, the most widely used SERS substrates were composed of noble metal nanoparticles (NPs) such as Ag and Au. Although, the excellent enhancement in * Mohamed Abd El‑Aal [email protected] 1
Chemistry Department, Faculty of Science, Assiut University, Assiut 71515, Egypt
2
Faculty of Natural System, Kanazawa University, Kakuma, Kanazawa 920‑1192, Japan
3
Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan
the Raman scattering of these metals, however, the price of high-purity Au is too high, and Ag is very easily oxidized [11] owing to its unprecedented advantage of low cost [12], catalytic properties [13, 14], and good optical characteristics [15], Cu NPs can be the desirab
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