Anisotropic optical properties of oriented silver nanorice and nanocarrots in stretched polymer films

Abstract

Stretching-induced orientation of both silver nanorice and silver nanocarrots dispersed in or deposited on the surface of poly(vinyl alcohol) (PVA) films was investigated using polarized UV-visible-near-infrared (NIR) spectroscopy and atomic force microscopy (AFM). The results show that the film stretching not only aligns the long axis of individual nanorice or nanocarrots preferentially along the stretching direction, but also induces assembly of these nanostructures into oriented arrays of random lengths in the deformation process. Consequently, the longitudinal surface plasmon resonance peaked at 820 nm for nanorice and 1050 nm for nanocarrots before stretching can be replaced by continuous extinction over the entire 800-1800 nm NIR spectral range after stretching. Stretched PVA films containing either silver nanorice or nanocarrots thus display polarization-dependent transmission of NIR light.

Dichroic nanocomposites based on polymers and metallic particles: from biology to materials science

“…Notably, in highly viscous liquids subjected to shearing, orientation of gold nanorods (average aspect ratios 2.4–4.2) were oriented only as long as the shear forces were present; orientation was lost almost immediately when the shear rate was decreased to zero . The drawn materials were dichroic already at a draw ratio of 1.5, with UV–visible absorption spectra showing the same characteristics as described above for dichroic nanocomposites with isotropic particles. When films were irradiated with a laser beam of wavelength 350 nm, the irradiated spots lost their dichroic behavior .…”

“…Similar to the above described nanocomposites with isotropic particles, rod‐like silver nanoparticles (widths of the order of 10–40 nm, typical aspect ratios ≤5) were incorporated in poly(vinyl alcohol) after casting of polymer solutions with dispersed particles . After drying, the resulting films were drawn at elevated temperature to draw ratios up to 5 .…”

Theoretical investigation of a plasmonic substrate with multi-resonance for surface enhanced hyper-Raman scattering

“…According to the electromagnetic enhancement mechanism and Equation ( 1 ), to achieve a significant enhancement of HRS signal, the spectral positions of the multi-resonance modes and the exciting and scattering lights should match. We noted that the wavelengths (1210 nm and 670 nm) of the first- and second-longitudinal resonance just match with that of the exciting light and the second-order Stokes light of SEHRS 36 .

Figure 3 Scattering spectra of an individual Ag nanorice under normal (θ = 0°, black) or oblique (θ = 45°, red) incidence.

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Deviating from the nanorod shape: Shape-dependent plasmonic properties of silver nanorice and nanocarrot structures

“…When the incident po-larization is oblique, all resonance modes can be excited efficiently. The polarization-dependent extinction properties of nanorice can be observed in an aligned nanorice array formed by stretching a polymer film with embedded nanorice [43]. After stretching the polymer film, embedded nanorice preferentially orient their long axes parallel with the stretching direction to assemble an aligned array.…”

“…In stretched polymer films, the embedded nanocarrots are aligned with the long axes preferably oriented along the stretched direction. The longitudinal resonances can only be efficiently excited when the incident light is polarized parallel to the long axes [43].…”