Mode-specific directional emission from hybridized particle-on-a-film plasmons

We investigate the electromagnetic interaction between a gold nanoparticle and a thin gold film on a glass substrate. The coupling between the particle plasmons and the surface plasmon polaritons of the film leads to the formation of two localized hybrid modes, one low-energy. film-like. plasmon and one high-energy plasmon dominated by the nanoparticle. We find that the two modes have completely different directional scattering patterns on the glass side of the film. The high-energy mode displays a characteristic dipole emission pattern while the low-energy mode sends out a substantial part of its radiation in directions parallel to the particle dipole moment. The relative strength of the two radiation patterns vary strongly with the distance between the particle and the film, as determined by the degree of particle-film hybridization

Plasmon-Interband Coupling in Nickel Nanoantennas

Plasmonic excitations are usually attributed to the free electron response at visible frequencies in the classic plasmonic metals Au and Ag. However, the vast majority of metals exhibit spectrally localized interband transitions or broad interband transition backgrounds in the energy range of interest for nanoplasmonics. Nevertheless, the interaction of interband transitions with localized plasmons in optical nanoantennas has hitherto received relatively little attention, probably because interband transitions are regarded as highly unwanted due to their strong damping effect on the localized plasmons. However, with an increasing number of metals (beyond Au and Ag) being considered for nanoplasmonic applications such as hydrogen sensing (Pd), UV-SERS (Al), or magnetoplasmonics (Ni, Fe, Co), a deeper conceptual understanding of the interactions between a localized plasmon mode and an interband transition is very important. Here, as a generic example, we examine the interaction of a localized (in energy space) interband transition with spectrally tunable localized plasmonic excitations and unearth the underlying physics in a phenomenological approach for the case of Ni disk nanoantennas. We find that plasmon interband interactions can be understood in the classical picture of two coupled harmonic oscillators, exhibiting the typical energy anticrossing fingerprint of a coupled system approaching the strong-coupling regime

Optical Forces in Plasmonic Nanoparticle Dimers

8 páginas, 9 figuras.-- et al.We present calculations of the optical forces between two metal nanospheres forming a hybridized plasmonic dimer. We consider homo- and heterodimers and investigate different plane wave illumination configurations. The forces between the particles are calculated using full Mie theory combined with the Maxwell stress tensor (MST) formalism, as well as by approximate methods, such as the Lorentz force (LF) approach taken in the dipole limit and calculations based on an optical potential. We show that the simplified calculation schemes can lead to serious errors in the case of strongly interacting particles and low damping. In particular, we find that equilibrium configurations, corresponding to vanishing optical forces, only are possible for homodimers illuminated in the end-fire configuration and for heterodimers, although multipolar effects and damping radically reduce the repulsive interactions in the latter case.This work was financially supported by the Swedish Research Council.Peer reviewe

Aloe emodin decreases the ERK-dependent anticancer activity of cisplatin

The present study describes the ability of an anthraquinone derivative aloe emodin (AE) to reduce the cytotoxic activity of the platinum(II)-based anticancer agent cisplatin toward murine L929 fibrosarcoma and C6 glioma cell lines. The protective effect of AE was demonstrated by MTT and crystal violet assays for cell viability, and involved supression of cisplatin-induced apoptosis and necrosis, as assessed by lactate dehydrogenase release and flow cytometric analysis of DNA fragmentation or phosphatidylserine exposure. Cell-based ELISA and Western blot analysis revealed that AE abolished cisplatin-triggered activation of extracellular signal-regulated kinase (ERK) in tumor cells, while activation of c-Jun N-terminal kinase was not significantly altered. A selective blockade of ERK activation with PD98059 mimicked the protective effect of AE treatment in both tumor cell lines. Moreover, AE failed to protect tumor cells against the ERK-independent toxicity of the Pt(IV)-based complex tetrachloro(O,O-dibutyl-ethylenediamine-N,N'-di-3-propanoate)platinum(IV). Taken together, these data indicate that herbal anthraquinone AE can downregulate the anticancer activity of cisplatin by blocking the activation of ERK in tumor cells

Novel platinum(IV) complexes induce rapid tumor cell death in vitro

The anticancer activity of platinum complexes has been known since the discovery of classical Pt(II)-based drug cisplatin. However, Pt(IV) complexes have greater inertness than corresponding Pt(II) complexes, thus allowing the oral administration and reducing the toxicity associated with platinum-based chemotherapy. Here, we describe the in vitro antitumor activity of some novel Pt(IV)-based agents against mouse fibrosarcoma L929 cells and human astrocytoma U251 cells. The cytotoxicity of 2 Pt(IV) complexes with bidentate ethylenediamine-N,N'-di-3-propanoato esters was found to be markedly higher than that of their Pt(II) counterparts and comparable to the antitumor action of cisplatin. In contrast to cisplatin, which caused oxidative stress-independent apoptotic cell death of tumor cells, these Pt(IV) complexes induced oxygen radical-mediated tumor cell necrosis. Importantly, the cytotoxic action of novel Pt(IV) complexes was markedly more rapid than that of cisplatin, indicating their potential usefulness in anticancer therapy. (C) 2005 Wiley-Liss, Inc

Multiscale conformal pattern transfer

We demonstrate a method for seamless transfer from a parent flat substrate of basically any lithographic top-down or bottom-up pattern onto essentially any kind of surface. The nano-or microscale patterns, spanning macroscopic surface areas, can be transferred with high conformity onto a large variety of surfaces when such patterns are produced on a thin carbon film, grown on top of a sacrificial layer. The latter allows lifting the patterns from the flat parent substrate onto a water-air interface to be picked up by the host surface of choice. We illustrate the power of this technique by functionalizing broad range of materials including glass, plastics, metals, rough semiconductors and polymers, highlighting the potential applications in in situ colorimetry of the chemistry of materials, anti-counterfeit technologies, biomolecular and biomedical studies, light-matter interactions at the nanoscale, conformal photovoltaics and flexible electronics

Broadband absorption enhancement in ultra-thin crystalline Si solar cells by incorporating metallic and dielectric nanostructures in the back reflector

Copyright © 2014 John Wiley & Sons, Ltd. We propose a back reflecting scheme in order to enhance the maximum achievable current in one micron thick crystalline silicon solar cells. We perform 3D numerical investigations of the scattering properties of metallic nanostructures located at the back side and optimize them for enhancing absorption in the silicon layer. We validate our numerical results experimentally and also compare the absorption enhancement in the solar cell structure, both with quasi-periodic and random metallic nanostructures. We have looked at the interplay between the metallic nanostructures and an integrated back reflector. We show that the combination of metallic nanoparticles and a metallic reflector results in significant parasitic absorption. We compared this to another implementation based on titanium dioxide nanoparticles, which act as a Lambertian reflector of light. Our simulation and experimental results show that this proposed configuration results in reduced absorption losses and in broadband enhancement of absorption for ultra-thin solar cells, paving the way to an optimal back reflector for thin film photovoltaics.18 pages double space. 14 figures. Submittedstatus: publishe

Melanoma tumor inhibition by tetrachlorido(O,O '-dibutyl-ethylenediamine-N,N '-di-3-propionate)platinum(IV) complex: in vitro and in vivo investigations

Tetrachlorido(O,O'-dibutyl-ethylenediamine-N,N'-di-3-propionate)-platinum(IV) complex, [PtCl4(n-Bu(2)eddp)], was previously found to be effective against fibrosarcoma and glioma cell lines. Here we presented that [PtCl4(n-Bu(2)eddp)] strongly reduced the growth of B16 melanoma cells in vitro. Inhibition of cell viability was accompanied with induction of both necrotic and apoptotic cell death. In addition, [PtCl4(n-Bu(2)eddp)] concealed the expansion of tumors induced in syngeneic C57BI/6 mice without visible signs of nephrotoxicity

[Pt(HPxSC)Cl-3], a novel platinum(IV) compound with anticancer properties

There has been a continuing effort for the discovery of novel platinum(IV)-based antitumor compounds with better therapeutic performances than cisplatin. In the present work, the anticancer action of recently synthesized Pt(IV)-based complex [Pt(HPxSC)Cl-3] was investigated using rat and human astrocytoma cell lines C6 and U251. [Pt(HPxSC)Cl-3] markedly reduced the number of cultured astrocytoma Cells (IC50, 80 mu M), as determined by crystal violet assay. The Pt(IV) complex induced apoptotic death of tumor cells, as flow cytometry analysis of the propidium iodide-stained cellular DNA revealed approx. 30% of hypodiploid cells in [Pt(HPxSC)Cl-3]-treated astrocytoma cell cultures. On the other hand, [Pt(HPxSC)Cl-3] at 200 mu M did not affect the viability of rat primary astrocytes, unlike the established anticancer drug cisplatin, which displayed high toxicity toward both astrocytoma cells (IC50, 15 mu M) and primary astrocytes (IC50, 20 mu M). Moreover, [Pt(HPxSC)Cl-3] at 100 mu M did not interfere with the ability of rat peritoneal macrophages to produce important antitumor molecules nitric oxide and tumor necrosis factor-a. Finally, we assessed the ability of [Pt(HPxSC)Cl-3] to restrain growth of some bacterial and yeast strains, but it showed rather limited antimicrobial activity. (c) 2005 Elsevier B.V. All rights reserved