FTIR spectrum of ZnSe nanoparticles shows that its transmission is not flat around 10 micrometer but in the presented spectrum by lens companies its transmission is smartly flat. What can be the reason? doping? bulk form? or ....
The factors other than that described by Askar Ismato, as described above, such as differences in sample preparation, instrumentation, and data processing can affect the transmission spectrum of FTIR analysis. Sample preparation, such as solvent or substrate choice, can influence the appearance of spectral features. Instrumental parameters, such as resolution and sensitivity, can influence the appearance of spectral features. Additionally, data processing can affect the perceived flatness of the spectrum.
The answer depends on sample preparation and the shape of this feature:
- Is that a well-defined band? 10 um is within the fingerprint region, so this is more likely related to contamination.
- Is it a broad band? This could be due to reflection losses. Is this also present in the pure matrix? are you weighing your matrix+analyte spectra against the pure matrix?
- does it look more like a baseline drift? A large one could be related to scattering effects, is the feature independent of sample grinding?
FTIR requires meticulous and reproducible sample preparation, it is common to account for these variations using a baseline correction. This is crucial in quantitative analysis, for example. See the following reference:
https://www.irdg.org/ijvs/ijvs-volume-5-edition-4/quantitative-mineral-analysis-by-ftir-spectroscopy