When preparing sensitized TiO2 with solaronix SQ2 dye, the films loose their colour completly and irreversibly if left on ambient light and air conditions, or if immersed in a solution of LiClO4 in acetonitrile. Is this normal? Is this dye very reactive to O2? Is the dye being oxidized or what is happening?
No, it is not normal condition. Color is appeared daue to occurence of a specific functional groups (e.g. carboxylic or phenolic or others) in dye. These functional groups in dye are highly sensitive in the presence of light. Functional groups bound in dye must react rapidly to change the color.
What do you mean exactly? I mean the colour is given by the total structure of the dye and high conjugation. The carboxylic groups are mainly there to bind to the TiO2. So if it is not normal what is happening to the dye then?
It must be changed the strctural configuration of the dye that need to check using spectroscopic studies such as GC-MS/NMR/IR etc before and after addition.
In the case of TiO2 , it is known in some photovoltaic devices and other applications of TiO2 as subsrate that it injects electrons into the material that is on its surface .
If the color you see is responsible for an electron hole recombination, it might be quenched by this electrons.
Try to prepare first an isolating layer , lets say a non conductive polymer (PMMA) on top of your TiO2, and then prepare the same sample of your dye on top ... and see what happens
If the color is still lose than we can think in a process due to oxygen in the environment, The easiest way to test this is by keeping the material in inert atmosphere of course you know how , right?
But something very interesting would b=be that the process is reversible right, like turning on and off the dye qith some oxygen , or without oxygen ... interesting
It is catalytic effect of the TiO2 in presence of light and oxigen. The process is also known as Photocatalysis and occours for all the organic dyes on TiO2 layer.
As Daniele said, it's the photocatalysis of Titania. It's a light and oxigen activated process, so if you keep the substrates in dark conditions or at least you use a light filter that removes the high energy light components (lambda
Hi,
I think its a photocatalytic reaction, color degradation of dye could be due to the de-conjugation in dye molecules, whenever electron-hole generation takes place under the presence of light.
You can do one thing, check the time period, How long you are keeping the photoanodes in dye solution and how much it is degraded. I mean, degradation of colour with respect to time, It would be a systematic study.
MAYBE YOU CAN FIND IN THIS PAPER SOME IDEAS, AND REASONS WHY AND WHAT IS AFFECTING YOUR DYE IN THE TiO2
Photocatalytic and Photovoltaic Properties of TiO2 Nanoparticles Investigated by Ab Initio Simulations
Giuseppe Mattioli, Aldo Amore Bonapasta, Daniele Bovi, and Paolo Giannozzi
J. Phys. Chem. C, Articles ASAP (As Soon As Publishable)
Publication Date (Web): December 4, 2014 (Article)
DOI: 10.1021/jp509830w
Hello Valeria,
With our researchers answers, I think correctly the degradation and photocatalytic happened through the adsorption process onto the material surface, so it is essential must be repeat the experiment under the same conditions to judge on the results correct or not.
Regards,
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