Hello All;
While characterizing mixed 2D and 3D perovskites, I observed that the absorption characteristics of the 2D perovskites are existed in the optical absorption spectra but not in the XRD. What could be the possible reason to this? Does it mean that absorption spectroscopy is more sensitive than XRD?
The characteristic XRD peak(s) of the 2D perovskites are usually observed between 2theta = 5-10 degrees; while the absorption peak(s) are observed at lower wavelength values, mostly below 500 nm.
I can think of two possible reasons. These are:
(i) XRD pattern highly depends on the degree of crystalline nature. If your sample is semi-crystalline or amorphous in nature, then you might not get all XRD peaks. Some peaks could be really blunt, diffused or less intense. However, absorbance spectroscopy deals with highly dilute solution/dispersion. Here, crystallinity plays no major role; and both crystalline and amorphous samples behave similarly in highly dilute systems.
(ii) Below 10 degrees, many diffractometers fail to give high quality data. Because at this regime, the main beam comes with the scattered beam; and the baseline uplifts. Therefore, small peaks could be lost.
In general, I believe, XRD is a simple, yet elegant crystallographic technique and should not be considered as less sensitive.
This will be because XRD has a different physical nature than spectroscopy. XRD is very sensitive to long-range disorder. In spectral analyzes, this arrangement may not play a significant role. Long-range order/disorder usually means the arrangement of polyheders in a structure.
Otherwise, I agree with what Souvik Bhattacharjee says. I would just like to state that even below 10o 2 theta it is possible to seriously measure, only more depends on the geometry of the measurement and the quality of the sample preparation. Common mistake in measuring at low angles is that the sample has a significantly smaller longitudinal dimension than the irradiated area.
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction