Dear Hanggara,

To the contrary, a study entitled " Is Methylene Blue An Appropriate Substrate for A Photocatalytic Activity Test? A Study with Visible-Light Responsive Titania" revealed the following: 

An analysis of decomposition of methylene blue (MB) in an aerated aqueous solution by its action spectrum has shown that sulfur-doped titania (S–TiO₂) has activity under visible-light irradiation and that the decomposition mechanism depends on the excitation wavelength. This suggests that photosensitive materials are not suitable as probe chemicals for photocatalytic activity tests, especially those for evaluation of activity under visible light. It is confirmed using acetic acid instead of MB that S–TiO₂, but not ordinary non-doped titania, leads to the photocatalytic reaction under visible radiation below 600 nm, which corresponds to its absorption spectrum.

4. Conclusion

The results indicate that there are two significant problems in the photocatalytic

activity test. One is the inadequacy of MB as a probe molecule for semiconductor

photocatalysis, since the photoinduced reaction by MB photoabsorption may mislead into  believing that a given semiconductor material has visible-light photocatalytic activity. Dyes other than MB [35] should also be examined for their suitability as a probe molecule. The other problem is the photoirradiation systems for the activity test. As above, action spectrum analyses enable us to discriminate the origin of photoresponse by checking the wavelength

dependence. However, when the samples are irradiated in MB solutions, for example, with a set of optical cut-off filters that transmit light of a wavelength longer than a given wavelength, as customarily employed, the results cannot be a proof of visible-light sensitizing ability, i.e., real photocatalytic activity.

In summary, the use of transparent substrates in the region of working wavelengths is strongly recommended, if at all possible, in a photocatalytic activity test for photocatalysts and for action spectrum analysis. By using the preferred test system, the present S-TiO2 has been proved really photoactive in the visible region, at least for the decomposition of AcOH into CO2. However, the present finding does not guarantee the visible-light activity for other frequently-used substrates such as acetone or toluene, which need careful individual examination.

For more details, see attached paper.

Hoping this will be helpful,

Rafik

Molecules, 2015, 10, 88-110.

Using dyes for evaluating photocatalytic properties. A critical review

Maybe you can find suitable dye for your photocatalytic test under visible light.

Rafik and Shen-Ming Chen: many thanks for your information. 

I agree with the fact that MB, so often tested in the literature, is probably the less suitable dye to measure photocatalytic activity. Some years ago, in J. Chem, Soc. (please refer to my publication list 02) we tried a lot of azo-dyes by separating bleaching (which is the fastest and less suitable test for photocatalysis) from integral mineralization (which is the really important side of the problem). MB can be leached by a variety of methods, not all linked to photocatalyis. So the complete network of mineralization, followed by TOC measurements, is by far the most indicative phenomenon linked to photocatalyis, provided suitable treatment of data is allowed for (please see my modelling on Chemosphere 2007, and other correlated papers).

Dye is not a good candidate for examining the photocatalytic activity under visible light irradiation due to the possible photosensitization. Some colorless pollutants which can not form complex with catalysts are recommended.

Very important findings Ignazio. I will read your works. Adding some information, I also found that MB is recommended by ISO for photocatalytic activity test (ISO published standard: 10678:2010 ‘Determination of photocatalytic activity of surfaces in an aqueous medium by degradation of methylene blue).

Anyway thanks for your info Ignazio !

Yes, Hanggara, I knew about ISO standard. This, however, does not convince me about the quality of this test. I have been widely using phenol as model molecule of aromatics. The only advantage of MB and other dyes, if bleaching only and not photomineralisation is examined, is in the fact that simple spectrophotometry may be employed, and not TOC measurements. In my opinion bleaching only leads to on overestimation of photocatalytic activity.

some researchers said that pharmatucal samples forexample antibiotics can be used to photoactivity test. because most of them are stable and its degradation products can be dedected to HPLC and GC-MS methods.

Some of the dyes which have been used for photocatalytic activity in visible light are

1) azo dyes with the N=N group like Reaction Red, Reaction Black and Direct Green

2) Methyl Orange and Methyl Blue

3) Rhodamine B

there is some effort in identifying standard photocatalysis conditions. So the papers from the IUPAC group (Nick Serpone et al.) should be a good guide

Dear All,

Many thanks for your comments. How about this paper, what do you think ? 

Dye decolorization test for the activity assessment of visible light photocatalysts: Realities and limitations, Catalysis Today, 224, 21–28.

They conclude that when the dye test is the only available option for the activity assessment, methylene blue (MB) should be selected. 

http://www.sciencedirect.com/science/article/pii/S0920586113006810

YOU CAN USE DRUG SOLUTION TO TEST Activity like ibubrofin, amociline. etc

Colorants are no the best option to evaluated the photocatalytic activity of a material. You can use phenol, it is much better to evaluate the activity and easy to follow by spectrophotometry. However if you are interested in a colorant a good option could be methyl orange. 

Dear Hanggara,

I hope this paper will be helpful for you, the paper entitled "Why Dyes Should Not Be Used to Test the Photocatalytic Activity of

Semiconductor Oxides", which was published by Environmental Science & Technology (ACS).

RohdamineB

As already outlined in the answers, one suitable dye is the one recommended in standard procedures; e.g. for evaluating the photocatalytic activity in wastewater treatment the standard is methylene blue. Of course, dye-sensitization is real and should also be considered and this actually would out-rule dyes from the standard pollutants.

In the end it is important what for is designed the photocatalyst. The reference pollutant should be accordingly chosen, untill a better reference is found and accepted....

Anyway, when choosing a reference pollutant for testing please be careful at the degradation mechanism, i.e. the potential intermediates that may occur.

It is advisable to select a pollutant with a simple degradation/oxidation mechanism, that does not lead to many and rather uncontrolled intermediates, as these might overlap in the response in the end analysis. One such example (thus not recommended as reference pollutant) is phenol, which leads to poly-hydroxilic compounds that gives you distorted results in UV-VIS analysis.

Additionally, the first step in photocatalysis - the adsorption should also be considered, as it is rate limiting...

you just try with methyl orange or methylene blue or even with rhodamine .

Try your material with this dye for same composition you will find out which dye show better result with your material. I have tried these dyes.

Methylene blue, Rhodamine 6G or Eosin Y can be considered for the same.

I worked on rhodamine b photodegradation and remazol brillant blue and i found a good result under visible light illumination

Ana Laura Luna Barron i think in the case of phenol its better to use HPLc (GC/MS)

For evaluating the photocatalytic activity in waste water treatment the standard dye used is methylene blue.

I think that almost all dyes should be use. however no colour samples such as phenolic or colourless organics is the best.