Issue 23, 2016

Exploration of MOF nanoparticle sizes using various physical characterization methods – is what you measure what you get?

Abstract

While the size of nanoparticles (NPs) seems to be a concept established in the field of NPs and is commonly used to characterize them, its definition is not that trivial as different “sizes” have to be distinguished depending on the physical characterization technique performed to measure them. Metal–organic frameworks (MOFs) are known for their crystallinity, their large variety of compositions due to a huge number of inorganic building blocks that can be combined with almost endless organic linkers, their tunable pore structure, their ultrahigh porosity, and the different ways their backbones can be functionalised. The combination of these features with the nanoworld offers manifold perspectives for the synthesis of well-defined MOF nanoparticles (NPs), whose size attribute should be accurately determined as it strongly influences their physicochemical properties (at this length scale). In order to elucidate size determination, we synthesised zirconium fumarate metal–organic framework nanoparticles (Zr-fum MOF NPs) and characterized them using various common characterization methods. Herein, we compare the results of different solid-state methods, including powder X-ray diffraction (PXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to data obtained from dispersion-based methods, such as fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). In doing so, we illustrate the challenge of finding the appropriate method for obtaining a MOF NP size that is meaningful in the context of the desired application. Moreover, we demonstrate the importance of applying multiple complementary techniques as soon as the MOF NP size is considered. Throughout this paper, we highlight and define some reasonable recommendations of how the MOF NP size should be explored.

Graphical abstract: Exploration of MOF nanoparticle sizes using various physical characterization methods – is what you measure what you get?

Supplementary files

Article information

Article type
Paper
Submitted
25 jan 2016
Accepted
03 mar 2016
First published
04 mar 2016
This article is Open Access
Creative Commons BY license

CrystEngComm, 2016,18, 4359-4368

Exploration of MOF nanoparticle sizes using various physical characterization methods – is what you measure what you get?

P. Hirschle, T. Preiß, F. Auras, A. Pick, J. Völkner, D. Valdepérez, G. Witte, W. J. Parak, J. O. Rädler and S. Wuttke, CrystEngComm, 2016, 18, 4359 DOI: 10.1039/C6CE00198J

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