Abstract
Accurate nanoparticle size determination is essential across various research domains, with many functionalities in nanoscience and biomedical research being size-dependent. Although electron microscopy is capable of resolving a single particle down to the sub-nm scale, the reliable representation of entire populations is plagued by challenges in providing statistical significance, suboptimal preparation procedures and operator bias. While alternative techniques exist that provide ensemble information in solution, their implementation is generally challenging for non-monodisperse populations. Herein, we explore the use of small-angle X-ray scattering in combination with form-free Monte Carlo fitting of scattering profiles as an alternative to conventional electron microscopy imaging in providing access to any type of core size distribution. We report on a cross-method comparison for quasi-monodisperse, polydisperse and bimodal gold nanoparticles of 2-7 nm in diameter and discuss advantages and limitations of both techniques.
Highlights
The preparation and accurate characterisation of sub-10 nm nanoparticles (NPs) plays a pivotal role in a multitude of chemical and biomedical applications, where size-dependent efficacy is often observed.[1,2,3] Notably, the cutoff for efficient renal clearance is below 10 nm, and NPs with broad size distributions may impair biocompatibility.[4]
Obtaining an accurate and representative size distribution of the AuNPs by transmission electron microscopy (TEM) is challenged by limited sample counts, preparation procedures and operator bias in image acquisition and analysis.[11,12,13]
We present feasible routes to obtain experimental data from both methods and provide a side-by-side comparison of the size distribution obtained for a variety of samples
Summary
The preparation and accurate characterisation of sub-10 nm nanoparticles (NPs) plays a pivotal role in a multitude of chemical and biomedical applications, where size-dependent efficacy is often observed.[1,2,3] Notably, the cutoff for efficient renal clearance is below 10 nm, and NPs with broad size distributions may impair biocompatibility.[4]. Structure interference and maximum entropy methods.[34,35,36,37] The recent development of the user-friendly software McSAS has further broadened the scope of this approach.[38,39] In a cross-lab collaboration of unimodal AgNPs, the parametric fitting and the MC method led to consistent and similar results, highlighting the validity and reliability of employing the MC approach.[40] The capabilities of the MC method in comparison to fitting to a presupposed model were further confirmed in a study of unimodal PbS nanocrystals.[41] Despite these encouraging results, there remains a lack of comprehensive investigations utilising the MC-SAXS method, especially for characterising non-uniform NPs below 10 nm To this end, we present a systematic study of sizing quasimonodisperse, polydisperse and bimodal thiol-capped AuNPs of 2–7 nm in diameter by conventional TEM and solutionbased SAXS. We aim to shed light on the general applicability of SAXS with MC fitting (MC-SAXS) for accurate NP size determination alongside a critical identification of its limitations
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