Hypothesis Test of the Photon Count Distribution for Dust Discrimination in Dynamic Light Scattering

Abstract

Users of dynamic light scattering (DLS) are challenged when a sample of nanoparticles (NPs) contains dust. This is a frequently inevitable scenario and a major problem that critically affects the reproducibility and accuracy of DLS measurements. Current methods approach this problem via photon correlation spectroscopy, but remedy exists only for a few special cases. We introduce here a general criterion and a clearly defined measure to discriminate between NPs and dust particles. The experimental results show that, in contrast to photon correlation spectroscopy, hypothesis testing and the statistical moment analysis of the photon count distribution provides an accurate and precise way to characterize NPs and Brownian dynamics in the presence of dust. To demonstrate, analyses of silica, iron oxide, and gold NPs of low polydispersity are presented.

Post-processing noise reduction via all-photon recording in dynamic light scattering

“…The small discrepancy can be attributed to the imperfect removal of the scattered light from the PMMA microparticles, which can be improved by changing the time span as shown later. We would like to emphasize that our DLS system requires no more than a single measurement even for contaminated samples, which is in contrast to the previous noise reduction schemes [28,31] that require measurement runs to be repeated until an uncontaminated data set is obtained.…”

“…However, the efficiency of the noise suppression offered by this approach strongly depends on both pollutant size and laser wavelength, which leads to incomplete removal of the noise under realistic conditions. A more effective approach is to perform measurements multiple times using an autocorrelator and take the average over "uncontaminated" signals that are free from significant noise [27][28][29][30][31][32]. For example, Bossert et al proposed the statistical moment analysis of the photon counting distribution performed by recording the temporal variation of the photon counting rate with the time scale of sub-seconds [31].…”

“…A more effective approach is to perform measurements multiple times using an autocorrelator and take the average over "uncontaminated" signals that are free from significant noise [27][28][29][30][31][32]. For example, Bossert et al proposed the statistical moment analysis of the photon counting distribution performed by recording the temporal variation of the photon counting rate with the time scale of sub-seconds [31]. Malm and Corbett proposed the criterion to judge whether the time correlation function obtained from the autocorrelator-based DLS system is contaminated or not using the deviation of the polydispersity index [32].…”

Preparation of metallosupramolecular single-chain polymeric nanoparticles and their characterization by Taylor dispersion

“…55 Even if the number of multi-chain aggregates is small compared to the SCPNs, their presence contributes unpredictable and anomalous intensity fluctuations to the overall scattering intensity that can be significant enough to distort the correlation function, which may severely bias the results of an analysis by means of DLS measurements. [51][52][53][54]56 Techniques such as viscometry coupled with SEC, small-angle X-ray or neutron scattering measurements, as well as 2D DOSY NMR spectroscopy have been successfully employed in this context, 51,52,54 but a reliable characterization of dispersed SCPNs remains challenging.…”

The Kinetics of β‐Hematin Crystallization Measured by Depolarized Light Scattering

“…Therefore, upon translational and rotational diffusion, the amplitude of depolarized scattering will fluctuate, and the rate and amplitude of the fluctuation of the scattering intensity will carry information about Brownian dynamics and particle size. It has been shown before that the statistical analysis of the photon count distribution of the scattered light describes accurately Brownian dynamics . Therefore, we used this technique to follow the self‐assembly and growth of β‐hematin crystals in the absence and presence of CQ.…”