Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Nano Lett. 2012 Aug 8;12(8):4090-4. doi: 10.1021/nl301555t. Epub 2012 Jul 17.
Silver is the ideal material for plasmonics because of its low loss at optical frequencies but is often replaced by a more lossy metal, gold. This is because of silver's tendency to tarnish and roughen, forming Ag(2)S on its surface, dramatically diminishing optical properties and rendering it unreliable for applications. By passivating the surface of silver nanostructures with monolayer graphene, atmospheric sulfur containing compounds are unable to penetrate the graphene to degrade the surface of the silver. Preventing this sulfidation eliminates the increased material damping and scattering losses originating from the unintentional Ag(2)S layer. Because it is atomically thin, graphene does not interfere with the ability of localized surface plasmons to interact with the environment in sensing applications. Furthermore, after 30 days graphene-passivated silver (Ag-Gr) nanoantennas exhibit a 2600% higher sensitivity over that of bare Ag nanoantennas and 2 orders of magnitude improvement in peak width endurance. By employing graphene in this manner, the excellent optical properties and large spectral range of silver can be functionally utilized in a variety of nanoscale plasmonic devices and applications.
银由于其在光学频率下的低损耗而成为等离子体的理想材料，但通常被损耗更大的金属金所取代。这是因为银容易变色和变粗糙，在其表面形成 Ag(2)S，从而极大地降低了光学性能，使其在应用中不可靠。通过用单层石墨烯钝化银纳米结构的表面，含硫的大气化合物无法穿透石墨烯来降解银的表面。防止这种硫化作用消除了源自非故意的 Ag(2)S 层的增加的材料阻尼和散射损耗。由于石墨烯原子层很薄，它不会干扰局域表面等离激元与传感应用中环境相互作用的能力。此外，在 30 天后，石墨烯钝化银（Ag-Gr）纳米天线的灵敏度比裸露的 Ag 纳米天线高 2600%，而峰值宽度的耐用性提高了 2 个数量级。通过以这种方式使用石墨烯，可以在各种纳米级等离子体器件和应用中有效地利用银的优异光学性能和大光谱范围。
