Dynamic light scattering distributions by any means

Abstract

Dynamic light scattering (DLS) is an essential technique for nanoparticle size analysis and has been employed extensively for decades, but despite its long history and popularity, the choice of weighting and mean of the size distribution often appears to be picked ad hoc to bring the results into agreement with other methods and expectations by any means necessary. Here, we critically discuss the application of DLS for nanoparticle characterization and provide much-needed clarification for ambiguities in the mean-value practice of commercial DLS software and documentary standards. We address the misleading way DLS size distributions are often presented, that is, as a logarithmically scaled histogram of measured relative quantities. Central values obtained incautiously from this representation often lead to significant interpretation errors. Through the measurement of monomodal nanoparticle samples having an extensive range of sizes (5 to 250 nm) and polydispersity, we similarly demonstrate that the default outputs of a frequently used DLS inversion method are ill chosen, as they are regularizer-dependent and significantly deviate from the cumulant z-average size. The resulting discrepancies are typically larger than 15% depending on the polydispersity index of the samples. We explicitly identify and validate the harmonic mean as the central value of the intensity-weighted DLS size distribution that expresses the inversion results consistently with the cumulant results. We also investigate the extent to which the DLS polydispersity descriptors are representative of the distributional quality and find them to be unreliable and misleading, both for monodisperse reference materials and broad-distribution biomedical nanoparticles. These results overall are intended to bring essential improvements and to stimulate reexamination of the metrological capabilities and role of DLS in nanoparticle characterization.

Formation of Oxidation- and Acid-Sensitive Assemblies from Sterols and a Quaternary Ammonium Ferrocene Derivative: Quatsome- and Onion-like Vesicles and Extended Nanoribbons

“…When compared to intensity-weighted distributions, FTDMA/Chol vesicles (Figure S2A,C) display good agreement between DLS and cryo-TEM while DLS size distributions of FTDMA/CHEMS vesicles (Figure S2B,D) overestimate the mean vesicle diameter. These results are consistent with the known limitations of DLS particle size measurements (i.e., number-weighted distributions tend to underestimate and intensity-weighted distributions tend to overestimate the mean particle size − ) and underscore the importance of obtaining “true” size distributions by microscopy for comparison to those obtained by light-scattering methods. Fewer total vesicles were observed in extruded samples, so it will be necessary to further validate these results in larger sample sizes.…”

Telescopic synthesis and encapsulation of anticancer drugs from Ajuga bracteosa Wall. ex Benth. with zeolitic imidazole framework‐8

“…DLS measurements were used to study the particle size distribution of nanoparticles. [ 50 ] We took three measurements to determine the size and stability of nanoparticles, and each measurement was recorded 20 times, as illustrated in (Figure 11a,b). ABE@ZIF‐8 NPs had an average particle size of 237.9 nm and a PDI (Polydispersity Index) of 0.247, making them slightly larger than ZIF‐8 NPs (236.4 nm with a PDI of 0.285).…”

A Polyplex in a Shell: The Effect of Poly(aspartic acid)-Mediated Calcium Carbonate Mineralization on Polyplexes Properties and Transfection Efficiency

“…The drastic difference in size between the two techniques (TEM vs hydrodynamic size by DLS) can be a consequence of the presence of particle motion modes that are non-Brownian (possibly a consequence of agglomeration and sedimentation) not fulfilling the necessary sample characteristics for accurate measurements using DLS 38 as well as the way particle size is estimated depending on the technique (number weighted vs intensity weighted). 61 At higher magnification (Figure 10), the "apparently" uniform particles at lower magnification showed an obvious heterogeneous morphology. Multiple cores embedded in a dense matrix was evident, which is likely the result of a complex interaction between the organic and inorganic components forming the particles during CaCO 3 nucleation and growth.…”