First of all, I would like to say that I am fresh in this field. Currently I am trying to measure degradation of Rhodamine B under UV or VIS radiation (40 mW/cm2). TiO2 thin films are used as catalyst (surface area 1 cm x 2 cm). The concentration of solution is 1e-5M and volume 35mL. The solution is magnetically stirred and O2 is constantly supplied. Unfortunately, I do not observe degradation of RhB. Therefore, I tried to increase light intensity to 100mW/cm2, however RhB did not degrade. I also tried to decrease concentration of the solution to 5e-6M the effect is the same. The last thing which I did was lowering solution volume to 20mL.
I have some suggestions and hope it helps. If you use TiO2 rutile it may result in a negligible degradation. Try to do a benchmark experiment using TiO2 powder and compare with the thin film experiment. Also try to make sure about the wavelength of the UV lamp.
Hi, I am photobiologist. My job is to look fot the light for every research program.I do not know anything about Rhodamine B and the reaction with TiO2.
I have looked for any information about the Rhodamine B absorbance, A Study on the Interaction of Rhodamine B with Methylthioadenosine Phosphorylase Protein Sourced from an Antarctic Soil Metagenomic Library
Figure 3. The UV-VIS absorption spectra of rhodamine B
It would interesting the irradiation with led emission close to 560 nm and/or UVC 200-250 bnm, not "UV or visible light" .It is very important the distance of the light emission and the power. You have to control the irradiation, not the radiation.
Hi Mantis. I have done research previously in the degradation of dyes such as rhodamine-B using TiO2 as the photocatalyst. Could you provide us with a little more information regarding your experimental setup so we could further assist you?
Specifically, what is the emission profile of your light source (i.e. 400-800 nm)?
What type of TiO2 is in the thin film (doped, rutile, anatase, etc.)?
Is the TiO2 embedded in the film or on its surface?
I agree with Hany Fathy Heiba in that a good preliminary test would be using TiO2 from the film as a powder if available.
Thank you all for the answers.
Dear John R. Bertram, I am using osram Halogen light bulb:
https://www.osram.com/ecat/HALOLINE%20PRO-HALOLINE-Halogen%20lamps-Lamps-Digital%20Systems/com/en/GPS01_1027717/PP_EUROPE_Europe_eCat/ZMP_95901/
Thin films are deposited on SiO2 substrates and have anatase phase. After band gap calculations appeared that their band gap are enormously large 3.8 eV. So, I think that is possible answer.
We also tried to investigate TiO2 thin films which surface was modified with Au nanoparticles. However the effect was the same.
Mantas Sriubas thank you for sharing! Yes I think you're right, it is a combination of the band gap and the light source being used. If you take a look at the emission spectrum of your light source (attached, taken from the site you linked) there is hardly any light from the UV range where TiO2 is activated. You will need to use something that gives stronger UV emission with wavelengths less than 320 nm. Hope this helps!
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