Nanoscale patterning of metal nanoparticle distribution in glasses

Optical nonlinearities in LiKB4O7-Ag2O and LiKB4O7-Ag2O-Gd2O3 glasses containing Ag nanoparticles

The results on optical studies of LiKB₄O₇-Ag₂O and LiKB₄O₇-Ag₂O-Gd₂O₃ glasses containing Ag nanoparticles formed during annealing in vacuum and air are presented. Strong bands that appear in optical transmission spectra of the samples correspond to plasmon excitations associated with Ag nanoparticles. The average radius of Ag nanoparticles was retrieved from FWHM of the plasmon bands and found to be 1.8-3.8 nm. Nonlinear optical properties of the glasses were studied by the single-beam Z-scan technique. In particular, influence of Ag nanoparticles on nonlinear refraction n₂ and nonlinear absorption β coefficients was investigated.

Investigation on the Effects of the Formation of a Silver "Flower-Like Structure" on Graphene

In this report, we experimentally investigate the formation of "flower-like silver structures" on graphene. Using an electrochemical deposition technique with deposition times of 2.5 and 5 min, agglomerations of silver nanoparticles (AgNPs) were deposited on the graphene surfaces, causing the formation of "flower-like structures" on the graphene substrate. Localized surface plasmon resonance (LSPR) was observed in the interaction between the structures and the graphene substrate. The morphology of the samples was observed using a field-emission scanning electron microscope (FESEM) and Raman spectroscopy. Thereafter, the potential of the flower-like Ag microstructures on graphene for use in Raman spectroscopic applications was examined. The signal showed a highest intensity value after a deposition time of 5 min, as portrayed by the intense local electromagnetic fields. For a better understanding, the CST Microwave Studio software, based on the finite element method (FEM), was applied to simulate the absorption characteristics of the structures on the graphene substrate. The absorption peak was redshifted due to the increment of the nanoparticle size.

Large patternable metal nanoparticle sheets by photo/e-beam lithography

Techniques for micro/nano-scale patterning of large metal nanoparticle sheets can potentially be used to realize high-performance photoelectronic devices because the sheets provide greatly enhanced electrical fields around the nanoparticles due to localized surface plasmon resonances. However, no single metal nanoparticle sheet currently exists with sufficient durability for conventional lithographical processes. Here, we report large photo and/or e-beam lithographic patternable metal nanoparticle sheets with improved durability by incorporating molecular cross-linked structures between nanoparticles. The cross-linked structures were easily formed by a one-step chemical reaction; immersing a single nanoparticle sheet consisting of core metals, to which capping molecules ionically bond, in a dithiol ethanol solution. The ligand exchange reaction processes were discussed in detail, and we demonstrated 20 μm wide line and space patterns, and a 170 nm wide line of the silver nanoparticle sheets.

Formation of silver nanoparticles in Li2B4O7-Ag2O and Li2B4O7-Gd2O3-Ag2O borate glasses

Results of investigations of 98.0Li₂B₄O₇-2.0Ag₂O and 97.0Li₂B₄O₇-2.0Ag₂O-1.0Gd₂O₃ glasses with Ag nanoparticles (Ag NPs), formed by thermal treatment in vacuum and in air, are presented. Intensive plasmon absorption bands, connected with Ag NPs, were observed in their optical transmission spectra. It is ascertained that in volumes of both glasses there is formed a small number of Ag NPs, whereas their main mass is concentrated near the surface of samples. The mechanism of Ag NPs formation is proposed. A conclusion is drawn that annealing in vacuum does not necessarily require the presence of reducing ions, whereas formation of nanoparticles at annealing in air is impossible without reducing agents. Structural defects play a decisive role in the Ag NPs nucleation process. Radii of formed Ag NPs are estimated by the half-width of plasmon bands, and by means of small-angle x-ray scattering.

Strong anisotropic lifetime orientation distributions of a two-level quantum emitter around a plasmonic nanorod

Spontaneous emission lifetime orientation distributions of a two-level quantum emitter in metallic nanorod structures are theoretically investigated by the rigorous electromagnetic Green function method. It was found that spontaneous emission lifetime strongly depended on the transition dipole orientation and the position of the emitter. The anisotropic factor defined as the ratio between the maximum and minimum values of the lifetimes along different dipole orientations can reach up to 10(3). It is much larger than those in dielectric structures which are only several times usually. Our results show that the localized plasmonic resonance effect provides a new degree of freedom to effectively control spontaneous emission by the dipole orientation of the quantum emitters.