Department of Materials and Applied Chemistry, College of Science Technology, Nihon University , Chiyoda, Tokyo 101-8308, Japan.
ACS Nano. 2013 Nov 26;7(11):9997-10010. doi: 10.1021/nn403925d. Epub 2013 Oct 8.
Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.
有序的铜纳米结构阵列被制备并通过卟啉分子进行修饰，以评估由于局域表面等离激元共振而引起的荧光增强。纳米结构通过在二维二氧化硅胶体晶体的上半球热沉积铜来制备。通过控制基底二氧化硅颗粒的直径，将纳米结构的表面等离激元共振的波长调谐到比铜的带间跃迁区域更长的波长（>590nm）。通过十六巯基己酸的自组装将卟啉单层固定在纳米结构上，这也抑制了铜表面的氧化。与平面 Cu 板（CuP）相比，由于产生了表面等离激元共振，卟啉的最大荧光增强倍数达到了 89.2。此外，还发现尽管在带间跃迁区域内荧光被猝灭，但在较长波长处，荧光被有效地增强。结果表明，荧光团与纳米结构的接近所引起的增强足以克服金属的高效猝灭效应。从这些结果可以推测，铜的表面等离激元共振在实际应用中作为高性能等离子体传感器和器件具有巨大的潜力。
