Hajimammadov Rashad, Bykov Alexander, Popov Alexey, Juhasz Koppany L, Lorite Gabriela S, Mohl Melinda, Kukovecz Akos, Huuhtanen Mika, Kordas Krisztian
Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, P.O. Box 4500, 90570, Oulu, Finland.
Optoelectronics and Measurement Techniques Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, P.O. Box 4500, 90570, Oulu, Finland.
Sci Rep. 2018 Mar 16;8(1):4708. doi: 10.1038/s41598-018-23119-6.
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 (CuO) and cupric oxides (CuO) and the formation of core-shell-like Cu-CuO/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-CuO/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.
原始未保护的铜表面上迅速形成的氧化物限制了铜纳米材料在具有物理接触的电子器件和传感器组件中的直接应用。然而，尚不清楚正在生长的氧化亚铜（Cu₂O）和氧化铜（CuO）以及核壳状Cu-Cu₂O/CuO纳米线的形成是否会对非接触式光学测量造成任何影响，在这种测量中，分别会发生光吸收以及随后的电荷振荡和分离，例如在表面等离子体辅助和光催化过程中。因此，我们使用开尔文探针力显微镜在黑暗和光照条件下分析水热合成的铜纳米线在环境条件下的表面电位如何随时间变化，以揭示纳米线和支撑金基底上的电荷积累。此外，我们对光吸收进行有限元建模，以预测纳米结构的等离子体行为。结果表明，核壳状Cu-Cu₂O/CuO纳米线在光催化和表面等离子体增强过程中可能都有用。在此，通过利用后者，我们表明，无论原生表面氧化物的形成情况如何，金基底上纳米线的随机网络都可作为表面增强拉曼光谱的出色放大介质，如对罗丹明6G染料分子的传感所示。
