We have succeeded in aligning gold nanoparticles (Au NPs) in three-dimensions using tobacco mosaic virus (TMV) in
order to realize new optical properties. TMV is a tube-shaped plant virus about 300 nm in length with an outer- and
inner-diameter of 18 nm and 4 nm. We genetically fused material-binding peptides that can promote metal
crystallization, namely a gold-binding peptide (GBP) and a titanium-binding peptide (TBP), to the outer-surface of
TMV. By reducing potassium chloroaurate with sodium borohydride in the presence of the engineered viruses in 5%
acetic acid solution, Au NPs were deposited on the outer-surface of the viruses. Using TBP-fused TMV, NPs of 5 nm
were obtained, with a standard deviation smaller than those deposited on wild-type TMV. The diameter of the NPs on
GBP-fused TMV was 10 nm. These results indicate that genetically-modified TMVs are promising templates for the
construction of optical metamaterials.
Loss is a critical parameter in metamaterials because it determines the resolution of a super-lens made of metamaterials.
The super-lensing effect observed in alternative multi-layer metamaterials consisting of metal and
dielectric layers is derived from the resonant photon tunneling (RPT) via surface plasmon polaritons (SPPs).
Here we demonstrates that the losses in the metamaterials can be estimated by simultaneous measurements of
attenuated total reflection (ATR) and RPT. RPT through silver (Ag)/SiO<sub>2</sub> metamaterials is studied experimentally.
A shift of the RPT peak away from the ATR dip is observed; the shift variation in an Ag/SiO<sub>2</sub> system is
smaller than that in an aluminum/MgF<sub>2</sub> system. This indicates that the shift is caused by the imaginary part
of permittivity, i.e., intrinsic losses, of metamaterials.