title: Plasmonic nanoparticle-film calipers for rapid and ultrasensitive dimensional and refractometric detection.
abstract: In this study, we develop an ultrasensitive nanoparticle (NP)-film caliper that functions with high resolution (angstrom scale) in response to both the dimensions and refractive index of the spacer sandwiched between the NPs and the film. The anisotropy of the plasmonic gap mode in the NP-film caliper can be characterized readily using spectroscopic ellipsometry (SE) without the need for further optical modeling. To the best of our knowledge, this paper is the first to report the use of SE to study the plasmonic gap modes in NP-film calipers and to demonstrate that SE is a robust and convenient method for analyzing NP-film calipers. The high sensitivity of this system originates from the plasmonic gap mode in the NP-film caliper, induced by electromagnetic coupling between the NPs and the film. The refractometric sensitivity of this NP-film caliper reaches up to 314 nm per RIU, which is superior to those of other NP-based sensors. The NP-film caliper also provides high dimensional resolution, down to the angstrom scale. In this study, the shift in wavelength in response to the change in gap spacing is approximately 9 nm Å(-1). Taking advantage of the ultrasensitivity of this NP-film caliper, we develop a platform for discriminating among thiol-containing amino acids.
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617 Taiwan, Republic of China. hsuenlichen@ntu.edu.tw.
authors.forename: Chen-Chieh
authors.initials: CC
authors.lastname: Yu
authors.forename: Keng-Te
authors.initials: KT
authors.lastname: Lin
authors.forename: Yi-Chuan
authors.initials: YC
authors.lastname: Tseng
authors.forename: Sin-Yi
authors.initials: SY
authors.lastname: Chou
authors.forename: Chang-Ching
authors.initials: CC
authors.lastname: Shao
authors.forename: Hsuen-Li
authors.initials: HL
authors.lastname: Chen
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Su
mesh_terms: D015374:Biosensing Techniques; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D003545:Cysteine / Q000737:chemistry; D016002:Discriminant Analysis; D005978:Glutathione / Q000737:chemistry; D006710:Homocysteine / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D012031:Refractometry
chemical_list: D006710:Homocysteine; D005978:Glutathione; D003545:Cysteine