Released Plasmonic Electric Field of Ultrathin Tetrahedral-Amorphous-Carbon Films Coated Ag Nanoparticles for SERS

Abstract

We have demonstrated the plasmonic characteristics of an ultrathin tetrahedral amorphous carbon (ta-C) film coated with Ag nanoparticles. The simulation result shows that, under resonant and non-resonant excitations, the strongest plasmonic electric field of 1 nm ta-C coated Ag nanoparticle is not trapped within the ta-C layer but is released to its outside surface, while leaving the weaker electric field inside ta-C layer. Moreover, this outside plasmonic field shows higher intensity than that of uncoated Ag nanoparticle, which is closely dependent on the excitation wavelength and size of Ag particles. These observations are supported by the SERS measurements. We expect that the ability for ultrathin ta-C coated Ag nanoparticles as the SERS substrates to detect low concentrations of target biomolecules opens the door to the applications where it can be used as a detection tool for integrated, on-chip devices.

Thermal stability of ultrathin and high dielectric ta‐C films coated with Ag nanostructures for SERS

“…In our previous report, we have also demonstrated an ultrathin ta-C film-coated Ag nanostructure as a novel SERS substrate, in which the 1-nm ta-C film can not only protect Ag oxygen-free in air but also redistribute the strongest plasmonic electrical field from the Ag/ta-C interface to ta-C/air interface. [14,15] In addition, the refractive index for ultrathin ta-C film at 1 nm is~2.44 in the broader frequency range from 300 to 1,300 nm, and the measurement with different angles shows that the refractive index is almost unchanged, which indicates that the 1-nm ta-C could be homogeneous. [15] However, the refractive index for Al 2 O 3 and SiO 2 films are 1.6 and 1.45, respectively, and may be more smaller when their thickness further decrease to 1 nm.…”

“…[14,15] In addition, the refractive index for ultrathin ta-C film at 1 nm is~2.44 in the broader frequency range from 300 to 1,300 nm, and the measurement with different angles shows that the refractive index is almost unchanged, which indicates that the 1-nm ta-C could be homogeneous. [15] However, the refractive index for Al 2 O 3 and SiO 2 films are 1.6 and 1.45, respectively, and may be more smaller when their thickness further decrease to 1 nm. [15] Thus, ultrathin ta-C film has a superior confinement for light, and electric field enhancement of ta-C-coated Ag nanostructures is higher than that of Al 2 O 3 or SiO 2 films coated with Ag nanostructures under the same thickness.…”

“…[15] Thus, ultrathin ta-C film has a superior confinement for light, and electric field enhancement of ta-C-coated Ag nanostructures is higher than that of Al 2 O 3 or SiO 2 films coated with Ag nanostructures under the same thickness. [4,15] Due to its dense structure and high refractive index, the ultrathin ta-C film could be a better candidate in the field of dielectric-coated Ag SERS study. [15] At present, catalysis reaction is vitally important in many fields, such as chemical synthesis process and chemical degradation process.…”

“…[15] However, the refractive index for Al 2 O 3 and SiO 2 films are 1.6 and 1.45, respectively, and may be more smaller when their thickness further decrease to 1 nm. [15] Thus, ultrathin ta-C film has a superior confinement for light, and electric field enhancement of ta-C-coated Ag nanostructures is higher than that of Al 2 O 3 or SiO 2 films coated with Ag nanostructures under the same thickness. [4,15] Due to its dense structure and high refractive index, the ultrathin ta-C film could be a better candidate in the field of dielectric-coated Ag SERS study.…”

“…[4,15] Due to its dense structure and high refractive index, the ultrathin ta-C film could be a better candidate in the field of dielectric-coated Ag SERS study. [15] At present, catalysis reaction is vitally important in many fields, such as chemical synthesis process and chemical degradation process. [16][17][18] In these catalysis reactions, how to clarify the catalytic mechanism is very helpful to develop novel catalysts, and SERS can help to understand the details in mechanism by the monitoring of reaction process.…”