The material composition of nanoparticles is an important aspect to consider when engineering nanomaterials that should fulfil specific property and performance criteria. Here we list 10 methods that can be used to characterize the nanoparticle chemical composition
The material of the nanoparticle matters
The chemical composition of nanoparticles can range from a single raw material to multiple ones, assembled into multi-layered and composite objects. The composition of the outer surface is important as it interfaces, and will interact with, the surrounding environment. The outer surface can be tailored to achieve a specific performance. For example, in nanomedicines, the nanoparticle surface can be functionalized with molecules to target specific cells in the body. Another example of surface tailoring would be where the nanoparticle is coated with a resistant layer to protect the core material from surrounding harsh conditions.
What are the bulk and surface chemical compositions of the nanoparticles?
The chemical composition of the nanoparticles can be characterized both in terms of surface and bulk chemistry. The surface chemistry refers to the composition of the outer layer of the nanoparticle, i.e. the layer which is exposed to the surrounding environment. The bulk chemistry corresponds to all chemical compounds present in the nanoparticles. Access to the surface or bulk chemical composition depends on the sensing depth of the measuring tool. The chemical composition of nanoparticles is mainly obtained by spectroscopy techniques and can be combined with microscopy to achieve single-particle level.
Below we list a set of techniques that can be used to extract the nanoparticle chemical composition. The information will be either on the ensemble level or at the single nanoparticle level, denoted with (E) and (SP) respectively.
Methods to characterize the surface chemistry
The surface chemistry of nanoparticles can be obtained using:
Auger electron spectroscopy (E)
X-ray photoelectron spectroscopy (E)
Inductively coupled plasma mass spectrometry (E)
Analytical electron microscopy (SP)
Chemical force microscopy (SP)
Methods to characterize the bulk chemical composition
Information about the bulk chemical composition of nanoparticles can be obtained using:
X-ray adsorption spectroscopy (E)
Energy dissipative X-ray (SP)
Electron energy loss spectroscopy (SP)
Time of flight mass spectroscopy (SP)
Single-particle inductively coupled plasma mass spectrometry (SP)
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