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Issue 4, 2019
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Quantification of amine functional groups on silica nanoparticles: a multi-method approach

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Abstract

Surface chemistry is an important factor for quality control during production of nanomaterials and for controlling their behavior in applications and when released into the environment. Here we report a comparison of four methods for quantifying amine functional groups on silica nanoparticles (NPs). Two colorimetric assays are examined, ninhydrin and 4-nitrobenzaldehyde, which are convenient for routine analysis and report on reagent accessible amines. Results from the study of a range of commercial NPs with different sizes and surface loadings show that the assays account for 50–100% of the total amine content, as determined by dissolution of NPs under basic conditions and quantification by solution-state 1H NMR. To validate the surface quantification by the colorimetric assays, the NPs are modified with a trifluoromethylated benzaldehyde probe to enhance sensitivity for quantitative 19F solid state NMR and X-ray photoelectron spectroscopy (XPS). Good agreement between the assays and the determination from solid-state NMR is reinforced by elemental ratios from XPS, which indicate that in most cases the difference between total and accessible amine content reflects amines that are outside the depth probed by XPS. Overall the combined results serve to validate the relatively simple colorimetric assays and indicate that the reactions are efficient at quantifying surface amines, by contrast to some other covalent modifications that have been employed for functional group quantification.

Graphical abstract: Quantification of amine functional groups on silica nanoparticles: a multi-method approach

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Publication details

The article was received on 08 Jan 2019, accepted on 21 Feb 2019 and first published on 22 Feb 2019


Article type: Paper
DOI: 10.1039/C9NA00016J
Nanoscale Adv., 2019,1, 1598-1607
  • Open access: Creative Commons BY-NC license
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    Quantification of amine functional groups on silica nanoparticles: a multi-method approach

    Y. Sun, F. Kunc, V. Balhara, B. Coleman, O. Kodra, M. Raza, M. Chen, A. Brinkmann, G. P. Lopinski and L. J. Johnston, Nanoscale Adv., 2019, 1, 1598
    DOI: 10.1039/C9NA00016J

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