I am looking for research papers/data regarding above mentioned tests for YAG and reason or mechanism particular for these peaks.
UV VIS result shows single peak at 205 nm.
Fluorescence spectroscopy with excitation wavelength = 205 nm shows two peaks at 308 nm and 412 nm. Thnakyou.
205 nm peak is due to Rayleigh Scattering. 415 nm (which is close to 2nd order of 205) is scattering too. When excited at 205 nm the spectra is generally recorded from 215 nm to 400 nm. (Please take help from someone in your lab/institute. This is very basic.) Otherwise you will get lot of higher order signals. In case you have luminescence signal beyond that use appropriate filter. 308 nm looks like an emission signal.
The peak (?) that you observe around 205 nm is probably an artifact. This is beyond the range of typical UV-vis spectrometer. Have a look at the literature and see where generally people excite this type of samples. Exciting in deep UV (e.g., 205 nm) is generally not advisable as in lot of cases fluorescence impurities show up in the signal.
Mr. Tuhin Khar I appreciate you input.I checked and I got literature for only YAG single crystals not YAG nanocrystals (which I am working on) so I asked here. I am new to this technique , hope you won't mind helping me with few questions :-
1)"205 nm peak is due to Rayleigh Scattering" .Are you commenting on UV VIS spectroscopy results? So it is not absobtion?? . Can you provide me literature to support this statement and other sources that can help in bringing clarity .
2)What could be the cause of scattering?Maybe absoption of atmospheric gases(YAG absorbs CO2) or small particles of YAG in colloid?
3)What should I conclude about fluorescence of YAG in visible region (350-800nm) from these results?Does it shows fluorescence in visible spectra or not(415 nm peak in emission is good) ?
Sharp 205 peak at emission is due to Rayleigh Scattering as you excited the sample at 205 nm. Scattering is a very fundamental process. Solvent, small particles of sample will lead to scattering.
Sharp signal in UV-vis around 205 is probably an artifact. This type of sharp signal is observed when we exceed the cutoff wavelength of the spectrometer. Even it is an real signal it do not have any implication as everything absorbs in the UV (starting from oxygen, water).
Second order signal in fluorescence spectrum will complicate your analysis. Use a filter to cut those signal. Before going into deep analysis change the excitation wavelength and see whether the emission spectra remains same or not. In case of fluorescence the emission peak is independent of your excitation wavelength. This will also help you understand the presence of scattering and higher order signal as these peaks will vary according to the excitation wavelength (not fluorescence peak).
As you asnwered I checked emission spectra at different excitaion values 200, 205, 210, 220, 240 nm and I have attached the results. The peak at 308 nm is observed in all the cases except excitation at 240 nm where peak shifts to about 316 nm. I think this is real emission peak ? The other peak at more tahn 400nm kept changing so I think it is scattering as you mentioned earlier? I think you meant to say that scattering shows peak which is not due to fluorescence (i.e it is type of error).
I also checked cut off wavelength concept .I used Ethanol(cut off wavelenght =205 nm) as solvent. I understand it will give large absorbance at 205 nm .But I made a base line using the solvent first and then performed uv vis on my sample with ethanol as solvent,cutt off wavelength still going to show up in my uv results?
If the emission peak (308 nm) is wavelength independent then it might be from your sample.
What about the absorbance signal around 625 nm. Do you think that is an artifact?
I suggest you take emission across the whole absorption spectra as I can clearly see a peak around 625 nm.
Even if you take a baseline with a solvent, depending on the spectrometer, you might see solvent signal. Importantly a quantitative analysis in that region (beyond solvent cutoff) is not possible. (For example in Varian UV-vis we used to get good quality spectra in the solvent absorption range but not in Jasco V530).
1.from above emission results can i confirm that peak at 415 nm is just scattering not fluorescence?
2.to add more I haven't checked excitation spectra too .Will that be helpful to check whether absorbtion uv vis is correct or not?
1. Yes, you can say with 100% confidence that 415 nm is scattering.
2. Excitation spectra is actually the "gold standard" to check the emission purity. If your excitation spectra matches with your absorption spectra then you can say that the emission is from your sample.
Please have look at this discussion regarding excitation spectra (especially by Friedrich Menges) https://www.researchgate.net/post/Whats_the_difference_between_an_excitation_spectrum_and_an_absorption_spectrum_for_the_same_molecule
- Badges
- Science method
- Similar topics
- Methodology
- Absorption Spectroscopy
- UV-Visible Spectroscopy