Naibo Chen

Toroidal Dipolar Excitation in Metamaterials Consisting of Metal nanodisks and a Dielectrc Spacer on Metal Substrate

We have investigated numerically toroidal dipolar excitation at optical frequency in metamaterials whose unit cell consists of three identical Ag nanodisks and a SiO2 spacer on Ag substrate. The near-field plasmon hybridization between individual Ag nanodisks and substrate forms three magnetic dipolar resonances, at normal incidence of plane electromagnetic waves. The strong coupling among three magnetic dipolar resonances leads to the toroidal dipolar excitation, when space-inversion symmetry is broke along the polarization direction of incident light. The influences of some geometrical parameters on the resonance frequency and the excitation strength of toroidal dipolar mode are studied in detail. The radiated power from toroidal dipole is also compared with that from conventional electric and magnetic multipoles.

Surface enhanced Raman scattering substrates prepared by thermal evaporation on liquid surfaces

We present an effective surface-enhancement Raman scattering (SERS) substrate enabled by depositing metallic film on a liquid surface at room temperature. Thermal evaporation is used to deposit Au atoms on silicone oil surface and then form quasi-continuous films. Due to the isotropic characteristics of the liquid surface, this film consists of substantial nanoparticles with uniform diameter, which is different from films fabricated on solid substrates and can be served as an applicable substrate for SERS detection. With the assistance of this substrate, SERS signals of rhodamine 6G were significantly enhanced, the dependence between SERS spectra and film thickness was investigated. Analytical simulation results confirm the experimental observations and the superiorities of our proposed method for preparation of SERS substrate. This work provides a potential application of metallic film deposition on free-sustained surface and holds promise as an efficient sensor in rapid trace detection of small molecule analytes.

Nanofluidic behavior at the interface of sectionalized hydrophobic/hydrophilic patterns in nanochannel

ABSTRACT We report a novel method to fabricate sectionalized hydrophobic/hydrophilic nanochannel. Photolithography, dry/wet etching, aligned anodic bonding and selective modification were utilized to fabricate nanochannel with four-sided surface patterns. Nanofluidic behavior was investigated by pressure driven method to study the relationship between pressure and meniscus position. Experimental results showed that evident delay happened to the flow before entering hydrophobic domain, the accumulative pressure required to pass through the hydrophobic section is significantly larger than hydrophilic section. This behavior may be attributed to the influence caused by the underlying wettability variation, especially under large surface-to-volume ratio in nanochannel.

Phase shifting mask modulated laser patterning on graphene

A one-step graphene patterning method is developed in this paper. A phase shifting mask is used to modulate incident laser beam spatially and generate graphene patterns by laser heating. Periodic graphene nanoribbon and nanomesh structures are fabricated by employing 1D and 2D phase shifting masks, respectively. The noncontact, simple procedure, easy handling and economic properties of this method make it promising towards graphene-based device fabrication.