(239b) Nanoparticle Chromatography - a Promising Way of Property Classification

For high-quality particulate products, a defined and narrow particle size distribution (PSD) is required, since a small change in PSD can have a large impact on their properties. For instance, the interaction of nanoparticles (NPs) with light is strongly size- and shape-dependent. Most of the techniques to produce NPs lead to size distributions despite the remarkable progress in liquid phase syntheses of well-defined NPs of controlled size and shape. Therefore, a classification step is mandatory to adjust or modify the obtained PSD according to the needs of the later product. Specific targets for the classification are: Separation of a broader feed into two or more fractions, the removal of fine or coarse tail fractions, shape separation as many NP syntheses lead to shape distributions, or the separation of by-products when several phases are formed. For instance, narrowing of the initial PSD or exclusion of an unwanted particle fraction might already significantly improve the NP performance of the later application.

Mass forces strongly decline with decreasing particle size. Therefore alternative routes are needed for nanoparticles. We demonstrate that nanoparticle chromatography is a highly promising and scalable method for property fractionation. The classification of different NPs in the size range from below 1 nm up to 100 nm is applied to several materials. Examples include the separation of C₆₀ from C₇₀ fullerenes [1], carbon nanodots as highly luminescent NPs [2], high precision classification of semiconducting ZnS quantum dots with respect to their bandgap [3], semiconducting gold clusters [4] and plasmonic gold, silver NPs and their alloys [5].

C₆₀ fullerenes are perfectly round, chemically well-defined and of uniform size of around 1 nm. Thus, they are ideal probe molecules to study dispersive particle interactions. We show how to measure Hamaker constants via adsorption equilibria obtained during their chromatographic separation. Gold clusters are separated by “green” anion exchange chromatography. We demonstrate the sharp, high efficiency separation and excellent reproducibility of size-selected classification into two or multiple fractions. Shape-selective separation is also possible for NPs of differing hydrodynamic diameter. The huge potential of NP chromatography will be demonstrated for both for size and exclusion and affinity chromatography.

Funding by DFG of the Collaborative Research Center 1411 “Design of Particulate Products” is greatfully acknowledged (https://www.crc1411.research.fau.eu/).

References

[1] Süß S., Michaud V., Amsharov K., Akhmetov V., Kaspereit M., Damm C., Peukert W., Quantitative evaluation of fullerene separation by liquid chromatography, J. Phys. Chem. C 123 (2019) 16747- 16756

[2] Hinterberger, V., Damm C., Guldi D., Peukert W., Purification and structural elucidation of carbon dots by column chromatography, Nanoscale 11 (2019) 8464-8474

[3] Süß S., Bartsch K., Wasmus C., Damm C., Segets D., Peukert W., Chromatographic property classification of narrowly distributed ZnS quantum dots, Nanoscale 12 (2020) 12114 – 12125

[4] Gromotka L., Lübbert L., Traoré N., Kaspereit M., Peukert W., Green and scalable fractionation of gold nanoclusters by anion exchange chromatography, ACS Applied Nano Materials 6 (2023) 6553-6962

[5] Gromotka L., Uttinger .J., Schlumberger C., Thommes M., Peukert W., Classification and characterization of multimodal nanoparticle size distributions by size-exclusion chromatography, Nanoscale 14 (2022) 17354-17364