The Accurate Imaging of Collective Gold Nanorods with a Polarization-Dependent Dark-Field Light Scattering Microscope

Abstract

Anisotropic nanomaterials, such as gold nanorods (AuNRs), could be employed as an orientation platform due to their polarization-dependent surface plasmon resonance. However, a variety of factors would affect the dark-field light scattering imaging of anisotropic nanomaterials, resulting in an unstable signal, which is not advantageous to its further application. In this work, the localized surface plasmon resonance properties of a few AuNRs at different angles were excited by polarization with a conventional dark-field microscope, in which it was found that the ratio of AuNRs’ light scattering intensity at different polarization angles (I) to that without a polarizer (I 0) reflected the orientation information of AuNRs. Furthermore, the light scattering signal ratio between the parallel polarization (I p) and that without a polarizer (I 0) was closely related with the aspect ratio of AuNRs, which could not be affected by external conditions. To verify this concept, a highly sensitive and selective assay of the alkaline phosphatase activity in human serum was successfully developed based on the chemical etching of AuNRs, resulting in a lower aspect ratio and a lesser I p/I 0. This result holds great promise for polarization-dependent colorimetric nanomaterials and single-particle tracers in living cells.

Emerging Luminescent Materials for Information Encryption and Anti-Counterfeiting: Stimulus-Response AIEgens and Room-Temperature Phosphorescent Materials

“…In addition, numerous functional materials with multimodal emission have also been investigated and used for advanced information encryption and anti-counterfeiting [12]. Attributed to the single particle analysis accuracy of dark-field microscopy (DFM) imaging [13][14][15][16][17], the single particle level data encryption could also be achieved recently [18].…”

High-Throughput All-Optical Determination of Nanorod Size and Orientation

“…By visually comparing the color CLocK e ⊥ ring signature to the Au NR width measured using SEM, we observe that the G intensity along e ⊥ trans becomes more apparent as the Au NR width increases, which is expected as the transverse plasmon mode becomes more intense (Figure and Table S3). Similarly, increases in Au NR AR can be inferred from the R/G intensity ratio observed along e ⊥ long , which should increase as the Au NR AR increases and the longitudinal peak red-shifts to larger wavelengths, although this trend will begin to break down due to limitations of the CCD, as discussed below. − Despite this limitation, color CLocK microscopy captures a unique and diagnostic signal from Au NRs that other forms of microscopy cannot capture (Figure S8). As such, color CLocK is a powerful high-throughput tool for nanoparticle feature screening.…”