Dual-Angle Interferometric Scattering Microscopy for Optical Multiparametric Particle Characterization

Abstract

Traditional single-nanoparticle sizing using optical microscopy techniques assesses size via the diffusion constant, which requires suspended particles to be in a medium of known viscosity. However, these assumptions are typically not fulfilled in complex natural sample environments. Here, we introduce dual-angle interferometric scattering microscopy (DAISY), enabling optical quantification of both size and polarizability of individual nanoparticles (radius <170 nm) without requiring a priori information regarding the surrounding media or super-resolution imaging. DAISY achieves this by combining the information contained in concurrently measured forward and backward scattering images through twilight off-axis holography and interferometric scattering (iSCAT). Going beyond particle size and polarizability, single-particle morphology can be deduced from the fact that the hydrodynamic radius relates to the outer particle radius, while the scattering-based size estimate depends on the internal mass distribution of the particles. We demonstrate this by differentiating biomolecular fractal aggregates from spherical particles in fetal bovine serum at the single-particle level.

Electrophoretic Deposition Interferometric Scattering Mass Photometry

“…We have performed Mie scattering simulations that replicate this behavior (see Supporting Information). Simulations suggest that this trend holds for particle diameters below 190 nm, although system specific differences including the refractive index of the particle and medium and the reflectivity of the coverslip and particle reflector , may alter this range.…”

Enhanced Quantitative Wavefront Imaging for Nano-Object Characterization

“…In this context, quantitative phase imaging (QPI) recently emerged as a powerful method for NP characterization. By giving access not only to the amplitude of the electromagnetic (EM) field but also its phase, QPIoften performed with a digital holographic setupoffers numerous advantages over intensity-only methods including numerical refocusing, , numerical aberration correction, sensor dynamic optimization, , and metrology without a priori knowledge about the sample. − In particular, QPI enables the precise estimation of the complex optical polarizability, thereby providing insights into the absorption and scattering cross sections independently of the NP’s shape or composition . In, e.g., biological applications, this allows us to determine the dry mass of biological objects. , Importantly, this approach bypasses any need for sample calibration, assumptions about sample composition, and any prior knowledge of the optical system.…”