Influence of Polarization Setting on Gold Nanorod Signal at Nonplasmonic Wavelengths Under Differential Interference Contrast Microscopy

Abstract

Researchers rely on a variety of microscopic techniques for observing and tracking anisotropic nanoparticles in real time experiments. This technical note focuses on the optical behavior exhibited by gold nanorods at nonplasmonic wavelengths under differential interference contrast microscopy (DIC). Intense diffraction patterns appear at nonplasmonic wavelengths, and the behavior of these patterns can be altered by adjusting the surrounding medium or the polarizer setting. Such patterns are absent when linear and crossed polarizations are utilized. Making polarization adjustments is important in DIC microscopy, because it affects bias retardation and image contrast. The nonplasmonic diffraction bands that were observed could potentially be exploited for rotational tracking, but more importantly, researchers should exhibit care in selecting a nanorod sample and the polarization setting when working with DIC microscopy.

Single Cell Optical Imaging and Spectroscopy

“…408,457,460-461 Non-polarized white light passes through the polarizer and then undergoes shearing into two orthogonal beams at the first prism. Resultantly, two coherent beams with a lateral shear of ~100 – 200 nm pass through the condenser and illuminate the sample plane.…”

“…Adjusting the phase shift alters the optical behavior of gold nanorods at non-plasmonic wavelengths. 460 …”

Simultaneous Single-Particle Superlocalization and Rotational Tracking

“…The relative intensity of the two dark lobes (the ratio of A 1 to A 2 ) is dependent on the orientation of the gold nanorod and the bias retardation, which is intentionally introduced as a phase shift between the two wavefronts passing through the specimen by adjusting the polarizer and quarter-wave plate settings to increase DIC image contrast. 27 Figure S2 shows an example of the DIC and modified bright-field images of the same gold nanorod at three different orientations using the pair of Nomarski prisms with the larger shear distance.…”

“…The two 45°p olarization configurations result in slightly different signal intensities once again due to the intentionally introduced bias retardation. 27 It should be pointed out that the accuracy in the measured distance is mostly independent of the nanorod's orientation; however, the localization precision varies as the nanorod's image contrast changes with its orientation.…”

“…With the second polarizer setting of 45°, the remaining dark spot can be nonlinear least-squares fitted with a 2D Gaussian function to locate the particle (Figure S3B, C), and the intensity changes with respect to the orientation of the nanorod’s short axis, as the observation wavelength corresponds to the transverse SPR mode of the gold nanorod (Figure S4). The two 45° polarization configurations result in slightly different signal intensities once again due to the intentionally introduced bias retardation . It should be pointed out that the accuracy in the measured distance is mostly independent of the nanorod’s orientation; however, the localization precision varies as the nanorod’s image contrast changes with its orientation.…”