I understand that when a material say, Fe is doped in say, ZnS nanoparticles, then there are no extra phases formed and there is only a shift in XRD patterns observed. But when nanocomposite is formed, there will be phases of Fe as well as ZnS in XRD spectrum.
Similarly, what are the kind of changes that can be seen in UV Visible Absorption spectrum that would help in distinguishing between doped nanoparticles and nanocomposites?
As you have said, when materials get doped, there are no additional phases; and the band-structure gets slightly modified. Depending on the nature of the host and dopant, the bandgap might vary accordingly.
But, in case of nanocomposites, there are more than one material (or phase) coexist together in the sample. Naturally they have different band-structures, DOS, bandgaps, absorption and reflectance properties. And all such properties will try to influence each other due to the interactions.
In brief, if you have got certain phases of iron compounds while making nanocomposites with ZnO as the host matrix, you'll get different absorption-peaks for all the components (if present significantly). Similarly in the Tauc's plot, there will be multiple regions, where the slope will change and from the extrapolated tangent, you'll get multiple bandgaps also.
So, this is similar to XRD. For doped materials, there are no new phases. Only some shifts are there. In absorbance spectra also, certain changes will signify change in bandgap. For composites, there are new peaks in XRD and absorbance spectra, which signify the properties of the additional phases.
In case of alloys however, the individual properties hardly remain. And the alloy behaves as a new (single) material with a specific band-structure and bandgap.
R. Priya
I give an example of UV spectra of a core-shell nanoparticle (doped nanoparticle) and a UV spectrum of a nanocomposite.
Synthesis of water-soluble core/shell CdS/ZnS nanoparticles at room temperature under ultrasonic irradiation: Potential for human serum detection Mandal A.R., Ishteev A.R., Volchematev S.A., Mazov V.N., Kuznetsov D.V. Inorganic Materials. 2016. Т. 52. № 3. С. 256-261.
http://journals.ioffe.ru/articles/viewPDF/10854
As you have said, when materials get doped, there are no additional phases; and the band-structure gets slightly modified. Depending on the nature of the host and dopant, the bandgap might vary accordingly.
But, in case of nanocomposites, there are more than one material (or phase) coexist together in the sample. Naturally they have different band-structures, DOS, bandgaps, absorption and reflectance properties. And all such properties will try to influence each other due to the interactions.
In brief, if you have got certain phases of iron compounds while making nanocomposites with ZnO as the host matrix, you'll get different absorption-peaks for all the components (if present significantly). Similarly in the Tauc's plot, there will be multiple regions, where the slope will change and from the extrapolated tangent, you'll get multiple bandgaps also.
So, this is similar to XRD. For doped materials, there are no new phases. Only some shifts are there. In absorbance spectra also, certain changes will signify change in bandgap. For composites, there are new peaks in XRD and absorbance spectra, which signify the properties of the additional phases.
In case of alloys however, the individual properties hardly remain. And the alloy behaves as a new (single) material with a specific band-structure and bandgap.
this paper can help you
http://journals.ioffe.ru/articles/viewPDF/10854
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