I have observed that the absorbance is increasing at long irradiation time during photocatalytic experiment for a perovskite material .Even I completely separate the catalyst particles with the centrifuge.
I have used a porous perovskite as a photocatalyst which has been prepared by a sol-gel combustion method , You can see images of the scanning electron microscope and the absorption curve of rhodamine B in the presence of this catalyst.
Heating of the sample is most likely the reason: by changing the temperature of the sample during observation, the sample is not observed in thermal equilibrium, nor even in a steady state. See what happens if you stabilise the temperature of your sample. Note that absorbance is by definition a linear response of the system (like resistance), implying that the measurement of absorbance is not to remove the system far away from its unperturbed state.
Heating of the sample is most likely the reason: by changing the temperature of the sample during observation, the sample is not observed in thermal equilibrium, nor even in a steady state. See what happens if you stabilise the temperature of your sample. Note that absorbance is by definition a linear response of the system (like resistance), implying that the measurement of absorbance is not to remove the system far away from its unperturbed state.
Absorbance or optical density is logarithmic ratio of intensity of incident to transmitted radiation. If the former is increased absorbance is bound to increase otherwise it can increase with conc. but that possibility is ruled out in your case. Longer irradiation May energize molecules to promote to higher levels to a greater extent.
Thanks for your answer Dr.Behnam Farid , I controlled the temperature as much as possible, but I'll do it more accurately.
Niloofar Mardiha : My pleasure. You could also change the intensity of the radiation you are using (the power transferred to the sample is to leading order proportional to radiation intensity).
- Badges
- Science method
- Similar topics
- Methodology
- Absorption Spectroscopy
- UV-Visible Spectroscopy