Three-Dimensional Orientation Sensors by Defocused Imaging of Gold Nanorods through an Ordinary Wide-Field Microscope

Abstract

Gold (Au) nanoparticles, particularly nanorods, are actively employed as imaging probes because of their special nonblinking and nonbleaching absorption, scattering, and emitting properties that arise from the excitation of surface plasmons. Herein, we report a novel sensing method that detects feature orientation at the nanoscale via the defocused imaging of individual Au nanorods (AuNRs) with an ordinary wide-field optical microscope. By simultaneously recording defocused images and two-photon luminescence intensities for a large number of individual AuNRs, we correlate their defocused images with their three-dimensional spatial orientations. The spatial orientation of many individual AuNRs can be monitored in situ and in real-time within a single frame, enabling its use as a technique for high-throughput sensing. The probe size can be as small as several nanometers, which is highly desirable for minimization of any potential interference from the probe itself. Furthermore, the sensing property is insensitive to the excitation polarization and the distribution of the probe aspect ratio, which allows AuNRs of any length within a proper regime to be used as orientation sensors without changing the laser frequency and polarization. These unique features make the orientation probes proposed here outstanding candidates for optical imaging and sensing in materials science and biological applications.

Super-resolution and super-localization microscopy: A novel tool for imaging chemical and biological processes

“…Therefore it is critical that molecular positions of fluorescent probes are localized with nanometer precision in order to reveal the heterogeneity of inner structures in the porous material. 88,89 has been developed to determine the 3D orientation of a tilted single dipole in a single image frame without angular detergency. The core idea is essentially based on electron transition dipole approximation and the fact that the dipole emission exhibits an angular anisotropy.…”

Platinum-coated Core-Shell Gold Nanorods as Multifunctional Orientation Sensors in Differential Interference Contrast Microscopy

“…Furthermore, characteristic scattering image patterns have been employed to decipher 3D orientation of single AuNRs without angular degeneracy. 4,[18][19][20][21][22] Despite recent advances in single particle rotational tracking techniques, there have been very limited studies on the development of new optical orientation probes that can provide higher sensitivity, multi-functionality, etc.…”

Improving Plasmon Sensing Performance by Exploiting the Spatially Confined Field

“…These novel optical properties of metallic nanoparticles have led to an increasing interest in physics, chemistry, bio-technology, and material science. Within these particular fields, refractometric localized surface plasmon resonance (LSPR) sensing is one of the most employed techniques [3,[5][6][7][8][9][10]. This method is main based on the unique feature of the strong dependence that the plasmonic resonance of the metallic nanostructure has on the local dielectric environment [1], allowing the real-time label-free detection of target analyte or refractive index changing [11][12][13][14][15].…”