Random networks of core-shell-like Cu-Cu2O/CuO nanowires as surface plasmon resonance-enhanced sensors

Abstract

The rapid oxide formation on pristine unprotected copper surfaces limits the direct application of Cu nanomaterials in electronics and sensor assemblies with physical contacts. However, it is not clear whether the growing cuprous (Cu2O) and cupric oxides (CuO) and the formation of core-shell-like Cu-Cu2O/CuO nanowires would cause any compromise for non-contact optical measurements, where light absorption and subsequent charge oscillation and separation take place such as those in surface plasmon-assisted and photocatalytic processes, respectively. Therefore, we analyze how the surface potential of hydrothermally synthetized copper nanowires changes as a function of time in ambient conditions using Kelvin probe force microscopy in dark and under light illumination to reveal charge accumulation on the nanowires and on the supporting gold substrate. Further, we perform finite element modeling of the optical absorption to predict plasmonic behavior of the nanostructures. The results suggest that the core-shell-like Cu-Cu2O/CuO nanowires may be useful both in photocatalytic and in surface plasmon-enhanced processes. Here, by exploiting the latter, we show that regardless of the native surface oxide formation, random networks of the nanowires on gold substrates work as excellent amplification media for surface-enhanced Raman spectroscopy as demonstrated in sensing of Rhodamine 6G dye molecules.

Effect of encapsulation on electronic transport properties of nanoscale Cu(111) films

“…In addition to bare Cu films, we considered Cu films with surface oxide since the surface of nanosized Cu films is susceptible to oxidation and surface oxidation reduces film conductivity 26 . The Cu films get oxidised easily not only when it is in contact with air but also during its growth in a ultra-high vacuum chamber 27,28 . Figure 2b shows the presence of copper oxide (Cu-O) on the surfaces.…”

Cu-Pd Bimetal and CuPt Alloy Nanotubes Derived From Cu Nanowires: Novel Amplification Media for Surface-Enhanced Raman Spectroscopy

“…Cu nanowires were synthesized by a hydrothermal route, [30], [31], [33] whereas their Pd and Pt modified derivatives were obtained by galvanic replacement reactions [34] similar to those as we reported earlier.…”

“…Recently, we have shown that Cu nanowires are suitable for SERS, in particular, when dispersed on Au thin films [30]. Although rapid oxidation of common metals may influence the local field and thus spectral amplification, in the case of Cu, the native surface oxides [31] do not seem to degrade SERS quality [30], [32].…”

“…In this paper, our aim is to extend our SERS studies on Pt and Pd derivatives of Cu nanowires. Our strategy follows the idea of combining highly and less SERS active metals into a synergic system by using very simple and easy-to-scale synthesis routes, which include hydrothermal growth of Cu nanowires [30], [31], [33] followed by a partial exchange of Cu with Pd and Pt in galvanic replacement reactions [34]. We show that the as-made hybrid nanostructures are having superior Raman enhancement as compared to Cu nanowires making them promising new candidates for SERS applications.…”

Template-Free and Surfactant-Free Synthesis of Selective Multi-Oxide-Coated Ag Nanowires Enabling Tunable Surface Plasmon Resonance

“…Core-shell nanowires with a metal core and dual-oxide shells comprising native oxides are the only ones that have been successfully synthesized, e.g., Cu/Cu 2 O/CuO or Cu/Cu 2 O/ZnO [ 9 , 10 ]. Our group successfully synthesized template-free and surfactant-free Ag nanowires with a uniform spontaneous ultra-thin titania shell (~0.5 nm) on TiO 2 coated Si substrate [ 11 ].…”