The metal ion will deposit on the surface of TiO2 particles or will occupy the free places inside the lattice ? or the two proposed cases are possible during the sol gel prepration of TiO2?
Nice question. You can confirm whether the Cu is only present on the surface or incorporated into the TiO2 lattice with the help of depth-profiling XPS analysis. See the following reference for an example: Sun et al., 2020. Chemical Engineering Journal. 397, 125444 (Article Mo-ion doping evoked visible light response in TiO2 nanocrys...
). In this work, the Mo ions were found to be uniformly distributed into the TiO2 lattice rather than only on the surface. See this quote from this work: "The calculated ratios of Mo:Ti was 2.42%, 2.21%, 2.48% and 2.39% corresponding to the depth of 0 nm, 1 nm, 2.5 nm and 5 nm, respectively, indicating Mo ions were distributed uniformly in the lattice rather than on the surface of TiO2 nanocrystals." See section 3.2 of this paper for more details. I hope my explanation is helpful. Thanks!
Mouhiaddine mohamed El Jamal
Experts correctly write that an analysis needs to be done. However, the following should be analyzed before analysis. In the technology of the sol-gel method, compounds with covalent bonds are usually formed. There will be no ions in the lattice. You need to think about the synthesis path. I doubt that the molybdenum ions were in the lattice of the titanium dioxide nanoparticles. Perhaps they were in the precursor.
In Lebanon we do not have XPS or ESCA, but we have EDX. we work with a molar ration (M/TiO2) which varies b/w 0.1 to 1. So by EDX, we can confirm the presence of the metal or its oxide at the surface, but we can not eliminate the possibility of its presence inside the lattice.
Apparently we can not predict the position of the doping ion, since many factors .....
I do not say EDX determine the ratio metal/metal oxide. I said, I introduce metal ion in small amount which correspond to 0.1%
Hey.
If you have high concentation of the metal íon (something like 5% of metal ion/Ti ions) it will probably separate phase and you'll obtain a composite. If there is the case, you can try to identify the phases by XRD or SAED, and depending on your synthesis, it can lead to a well dispersed composite, or the two materials separated, one on the surface of the other.
If you have small concentration of the metal íon , and the metal íon is not much bigger or much smaller than Ti (IV) ions (I miss the exactly number, but Callister's book on material science and engineer describes it better than me), it will probably be in the lattice, this one will often be responsible to XRD peaks assymetry/displacement of few 2theta (beware of poorly calibrated equipments!), it will also change the band-gap of the material (beware of misusing Tauc's plot for determining optical band-gap). XPS is most sofisticated for determining it, EELS you're probably not finding the signal to solve chemical environment of the dopant, but I'd first check my XRD or band-gap before going to more expensive/sofisticated techniques!
Hi
Thx for yr answer. My molar % are (0, 0.2, 0.4, 0.7 and 1 %) are very low. The radius of Ni(II) ion ~ 0.72 Angstrom is higher than Ti(IV) (~0.61 Angstrom). so it will not be inside the lattice or replace Ti ion. in any case I will check my XR spectra.
When we try to design a nanomaterial( I guess what is you are talking about) first you should synthetize the nanomaterial itself without doping. This step serves to confirm the crystal system you are obtaining, for example: orthorhombic, tetragonal, fcc. Then, with that information insilic calculations can be perform to determine the properties and stability of compound doped.
ı agree with prof. Yuri Mirgorod . Also theTio2 lattice size is very important.if the width is large enough for ions to settle, it can penetrate
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