Serhiy Malynych

Coupled planar silver nanoparticle arrays as refractive index sensors

The optical properties of plasmon coupled, planar silver nanoparticle arrays (PSNA) were studied as a function of the refractive index of the surrounding medium. The PSNA samples were fabricated by self-assembling 100 nm silver particles into a single layer on chemically modified glass substrates. The arrays exhibit an intense sharp peak in the extinction spectrum in the UV–vis spectral range originating from near-field interactions between localized surface plasmons in the nanoparticles. The spectral position of the peak appeared to be sensitive to changes in the dielectric function of the local surrounding medium. Because of this dependence, the PSNA can function as a sensor for measuring the refractive index of the host medium.

Vacuum deposition of silver island films on chemically modified surfaces

The silver island films were vacuum deposited at two different evaporation rates on unmodified indium tin oxide substrates and the substrates modified with molecules containing thiol, pyridyl, and fluorocarbon groups. The films were characterized by UV-visible spectroscopy and scanning electron microscopy. Large variations in the structure and thickness of the island films that were observed between substrates were rationalized in terms of different chemical affinity of the surfaces to the silver metal.

Surface Plasmon Modes of Sandwich-Like Metal–Dielectric Nanostructures

We established that metal–dielectric nanostructures (consisting of three stacked monolayers of silver nanoparticles incorporated into polymer cross-linked film) can demonstrate three different surface plasmon collective modes. The modes were detected when the extinction spectra of the nanostructures were studied as a function of the incident angle and polarization of the incident light. Two previously known surface plasmon collective modes, namely T and P, associated with particle dipoles parallel and perpendicular to plane of the layer were identified for the polymer films containing one, two, and three monolayers of the particles. The extinction bands of T and P modes exhibited different intensity and frequency dependences on the angle of incidence. More pronounced angular dependences for P mode band indicated the stronger coupling of dipoles for P mode than for T one. A new N mode was observed for the structures consisting of three nanoparticle layers. This mode originated from surface plasmon coupling between adjacent layers. The additional mode significantly increases amount of information that can be obtained from optical response of the nanostructures.