Visually I am seeing that the color of the MB die is fading with time. But when I going to do the UV Vis spectrometry test the lambda max value becoming higher than the MB's lambda max. But the sample's lambda max should decrease than MB. What can be the possible reason?
Thanks in advance for your time.
Dear Ahsanul,
What do you mean by term "lambda max"? Lambda max should be a position of peak with the highest absorption measured in nanometers. And the absorption A should decrease. Please, clarify the question.
Best wishes,
Halyna
Halyna Bodnar Yankovych Lambda max is indicating the wavelength where the absorbance is maximum. You are right the absorbance should decrease but in my case it is increasing which is weird. But visibly I am seeing that the methylene blue color is becoming fade. What can be the possible reason?
Have you calibrated your UV-Vis spectrometer? You should check it, probably it is just the technical problem. If no, some additive signal appears. Do you thoroughly wash and dry cuvette after each solution? Sometimes some amount of dye from concentrated solution can adsorb on the cuvette walls.
Halyna
Additionally, do you remove photocatalyst before the measurements?
What do you think should I increase the centrifuging time? Currently I am centrifuging for 10 min in 5000 rpm.
Yes, try to do this improvment. Or filter your solution thought syringe filter. Furthermore, it can be helpful if you measure UV-Vis spectrum of photocatalyst suspension in conditions same as for the experiment. Sometimes the bare photocatalyst’s suspension possesses the peak in the range same to studied substance. In such cases UV-Vis is not suitable for this system.
good luck :)
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