title: Nanofiber near-field light-matter interactions for enhanced detection of molecular level displacements and dynamics.
abstract: We experimentally demonstrate that plasmonic nanoparticles embedded in the evanescent field of subwavelength optical waveguides (WGs) are highly sensitive to distances normal to the propagation of light, showing an ~10× increase in spatial resolution compared to the optical field decay of the WG. The scattering cross-section of the Au nanoparticle is increased by the plasmon-dielectric coupling interaction when the nanoparticle is placed near the dielectric surface of the WG, and the decay of the scattering signal is enhanced, showing angstrom level distance sensitivity within 10 nm from the WG. Numerical studies with the finite-difference time-domain (FDTD) method correlate well with the experimental results. To demonstrate real-time monitoring of a single molecule stretching in the evanescent field, we linked individual single-stranded DNA molecules between the WG and plasmonic nanoparticles and pushed on the nanoparticles with fluidic forces. The simple design and ease of obtaining optical feedback on molecular displacements makes our approach ideal for new in situ force sensing devices, imaging technologies, and high-throughput molecular analysis.
authors.affiliation: Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093, United States.
authors.forename: Ilsun
authors.initials: I
authors.lastname: Yoon
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Baker
authors.forename: Kanguk
authors.initials: K
authors.lastname: Kim
authors.forename: Nicholas O
authors.initials: NO
authors.lastname: Fischer
authors.forename: Daniel
authors.initials: D
authors.lastname: Heineck
authors.forename: Yinmin
authors.initials: Y
authors.lastname: Wang
authors.forename: Sadik C
authors.initials: SC
authors.lastname: Esener
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Sirbuly
mesh_terms: D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000302:isolation & purification; D005336:Fiber Optic Technology; D006046:Gold / Q000737:chemistry; D008027:Light; D057139:Nanofibers / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D012542:Scattering, Radiation
chemical_list: D004277:DNA, Single-Stranded; D006046:Gold