Assessing the extent, stability, purity and properties of silanised detonation nanodiamond

The functionalisation of nanodiamond is a key step in furthering its application in areas such as surface coatings, drug delivery, bio imaging and other biomedical avenues. Accordingly, analytical methods for the detailed characterisation of functionalised nano-material are of great importance. This work presents an alternative approach for the elemental analysis of zero-dimensional nanocarbons, specifically detonation nanodiamond (DND) following purification and functionalisation procedures. There is a particular emphasis on the presence of silicon, both for the purified DND and after its functionalisation with silanes. Five different silylation procedures for purified DND were explored and assessed quantitatively using inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of dilute suspensions. A maximum Si loading of 29,300 μg g⁻¹ on the DND was achieved through a combination of silylating reagents. The presence of 28 other elements in the DND materials was also quantified by ICP-MS. The characterisation of Si-bond formation was supported by FTIR and XPS evaluation of relevant functional groups. The thermal stability of the silylated DND was examined by thermogravimetric analysis. Improved particle size distribution and dispersion stability resulted from the silylation procedure, as confirmed by dynamic light scattering and capillary zone electrophoresis.