Quantification and Stability Determination of Surface Amine Groups on Silica Nanoparticles Using Solution NMR
| Autor: | Andreas Brinkmann, Donald M. Leek, Filip Kunc, Ying Sun, Linda J. Johnston, Vinod Balhara |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Proton Magnetic Resonance Spectroscopy
Nanoparticle 02 engineering and technology 010402 general chemistry 01 natural sciences Analytical Chemistry Nanomaterials chemistry.chemical_compound Particle Size Dissolution Amination Propylamines Chemistry Hydrolysis Temperature Silicon Dioxide 021001 nanoscience & nanotechnology 0104 chemical sciences Ninhydrin Proton NMR Nanoparticles Amine gas treating Particle size 0210 nano-technology Nuclear chemistry |
| Zdroj: | Analytical Chemistry. 90:13322-13330 |
| ISSN: | 1520-6882 0003-2700 |
| Popis: | Surface chemistry is a critical factor for determining the behavior of a nanomaterial after incorporation in composites, devices, and biomedical products, and is also important for nanotoxicology studies. We have developed an optimized protocol for dissolution of aminated silicas and determination of functional-group contents by quantitative ¹H NMR (qNMR) analysis of the released amines. A number of variables were optimized for the dissolution protocol, including the base concentration, mass of silica, time, temperature, and method of sample agitation, in order to achieve adequate NMR signals for quantification. The protocol was tested using nanoparticles from a single commercial supplier with sizes ranging from 20 to 120 nm that were functionalized with 3-aminopropyl groups. Interestingly the batch-to-batch variability for some sizes of these aminated silicas was as high as 50%. Amine contents measured by a ninhydrin colorimetric assay were typically ∼20% lower than those measured by qNMR, consistent with measurement of only ninhydrin-reagent accessible amines. The dissolution–qNMR protocol was compatible with aminated silicas from other commercial suppliers, and in these cases, an even larger variability in surface coverage was observed. Silica nanoparticles with longer-chain amines and variable amine loadings were synthesized to demonstrate the ability to quantify amines with more complex structures and to assess the limit of quantification for the dissolution–qNMR method. Finally, the stability of the aminated nanoparticles was examined. Loss of 3-aminopropyl groups occurred in water at room temperature and was significantly more rapid at higher temperatures. Amine loss increased with increasing surface coverage and was slower for long-chain amines, consistent with studies of amine stability on planar silica. Overall, this work highlights the importance of developing methods for quantifying surface functionalization, particularly given the variability in surface coverage for commercial samples, and for ensuring that the amine group is stable under its usage conditions. |
| Databáze: | OpenAIRE |
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