Plasmon-Enhanced Photothermal Response In Heterogeneous Metallic Trimers

Heat generation in plasmonic nanostructures has attracted enormous attention due to the ability of these nanostructures to generate high temperatures in nanoscale volumes using far-field irradiation, enabling applications ranging from photothermal therapy to fast (sub-nanosecond) thermal optical switching. Here we investigate the optical and thermal response of a heterogeneous trimer structure composed of a gold nanoparticle surrounded by two larger silver nanoparticles analytically and numerically. We observe that this type of multi-scale multi-material plasmonic oligomer can produce temperature changes over two orders of magnitude higher than possible with isolated gold nanoparticles

Taking Cascaded Plasmonic Field Enhancement To The Ultimate Limit In Silver Nanoparticle Dimers

Cascaded optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of field enhancement factors that dramatically exceed those observed in isolated nanostructures. While previous studies demonstrated the existence of cascaded enhancement, little work has been done to identify the requirements for achieving maximum field enhancement. Here, we investigate cascaded field enhancement in silver nanosphere dimers as a function of volume ratio and center-to-center separation, and show the requirements for achieving the ultimate cascading limit in nanoparticle dimers. We observe field enhancements that are a factor 75 larger than observed in isolated silver nanoparticles. © 2012 SPIE

Plasmon-enhanced photothermal response in heterogeneous metallic trimers

Heat generation in plasmonic nanostructures has attracted enormous attention due to the ability of these nanostructures to generate high temperatures in nanoscale volumes using far-field irradiation, enabling applications ranging from photothermal therapy to fast (sub-nanosecond) thermal optical switching. Here we investigate the optical and thermal response of a heterogeneous trimer structure composed of a gold nanoparticle surrounded by two larger silver nanoparticles analytically and numerically. We observe that this type of multi-scale multi-material plasmonic oligomer can produce temperature changes over two orders of magnitude higher than possible with isolated gold nanoparticles

Design Of Cascaded Plasmon Resonances For Ultrafast Nonlinear Optical Switching

The optical properties of cascaded plasmon resonant metallic nanocomposites are investigated. Plasmon resonances and their related field distributions are numerically evaluated in two-dimensional arrays of spherical silver nanoparticles embedded in a dielectric host. The field distributions in structures with identical particle sizes indicate the presence of a largely dipolar particle response, with a small multipole resonance contribution at high frequency. However, in arrays consisting of particles with dissimilar sizes, an additional coupled mode appears in which the dipole moment in adjacent particles is found to be anti-parallel. For increasing size-dissimilarity a higher electric field enhancement is observed inside the small metal nanospheres, indicative of a cascaded field enhancement effect. This effect may be used to enhance the nonlinear optical response of an effective medium composed of particles with engineered size dispersion and particle placement. © 2011 SPIE

Cascaded Plasmon Resonances Multi-Material Nanoparticle Trimers For Extreme Field Enhancement

Optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of field enhancement factors that significantly exceed those observed in isolated nanostructures. While previous studies demonstrated the existence of such cascaded field enhancement in coupled nanospheres with identical composition, this effect has not yet been studied in systems containing multiple materials. Here, we investigate the polarization-dependent optical response of multi-material trimer nanostructures composed of Au nanoparticles surrounded by two Ag nanoparticles as a function of nanoparticle size and inter-particle spacing. We observe field enhancement factors that are ten times larger than observed in isolated Au nanoparticles. © 2013 SPIE

Cascaded plasmon resonances multi-material nanoparticle trimers for extreme field enhancement

ABSTRACT Optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of field enhancement factors that significantly exceed those observed in isolated nanostructures. While previous studies demonstrated the existence of such cascaded field enhancement in coupled nanospheres with identical composition, this effect has not yet been studied in systems containing multiple materials. Here, we investigate the polarization-dependent optical response of multi-material trimer nanostructures composed of Au nanoparticles surrounded by two Ag nanoparticles as a function of nanoparticle size and inter-particle spacing. We observe field enhancement factors that are ten times larger than observed in isolated Au nanoparticles

Neuraminidase gene sequence analysis of avian influenza H9N2 viruses isolated from Iran (19982001) Arch. Razi Institute

ABSTRACT Influenza A viruses possesses two virion surface glycoproteins including haemagglutinin (HA) and neuraminidase (NA). The NA plays an important role in viral replication and promotes virus release from infected cells and facilitates virus spread throughout the body. To find out any genomic changes that might be occurred on NA gene of avian influenza circulating viruses, we have genetically analyzed the neuraminidase gene of six Avian Influenza (AI) viruses H9N2 subtype isolated from different parts of Iran. A comparison of deduced amino acid sequences, showed some amino acid substitutions among the local AI isolates. However no insertions/deletions or shortening in the stalk region of the genes were observed. Mutation in Glu 119 as a marker for enzyme sensitivity to the antiviral drugs was not observed. Phylogenitic analysis revealed three distinct groups among the isolates of Iran, Hong Kong, and Pakistan/Japan/Saudi Arabia respectively. Based on the results, no significant mutations in NA genes of the viruses isolated during the period of the study occurred and our findings are in agreement with results of previous study of the viruses indicated a low pathogen character for the isolates on the basis of amino acid sequence of HA cleavage site and experimental infection

Immunogenicity of commercial, formaldehyde and binary ethylenimine inactivated Newcastle disease virus vaccines in specific pathogen free chickens

Newcastle disease (ND) is one of the most important diseases that affect birds; the epizootic nature of the disease has caused severe economic losses in the poultry industry worldwide. In this experiment ND virus (NDV) was inactivated by two different chemicals binary ethylenimine (BEI) and formaldehyde. Formaldehyde was used at 0.1%, while BEI was used at concentrations of 1 to 4 mM. NDV inactivation with BEI was done in various incubation temperatures and periods and the best result (30 °C, 4 mM BEI and 21 hrs treatment) used as an experimental vaccine. Prepared inactivated NDV vaccines and a commercial vaccine were tested for their efficiency in generating humoral immune response in different groups of specific pathogen free (SPF) chicks. Test groups received 0.2 ml formaldehyde inactivated NDV (NDVF), BEI inactivated NDV (NDVEI) and Razi institute produced NDV vaccine (NDVR) subcutaneously respectively. HI Log 2 total mean titer of NDVEI group (8.42 ± 0.12) were significantly higher than NDVF (7.64 ± 0.16) and NDVR (7.86 ± 0.11) groups (p<0.05). BEI-inactivated vaccine gave higher antibody titers than formaldehyde-inactivated vaccine and preserves both structural integrity and antigenicity of the virus. Thus, it might be possible to use these compounds as an inactivator agent for commercial NDV inactivated vaccines in future