There are several ways to improve the photocatalytic activity of TiO2 based catalyst. The most common are doping with transition metals or with N, S, F, etc. Another very common way is the use dyes.

Yes, metal/non metal doping has been widely studied for improvement of photocatalysts in order to use visible light for photocatalytic degradation. sensitization with dyes can be useful in case of solar applications.

Also carbon and transition metals (e.g. W) can lower the band gap of TiO2 semiconductor. Co-doping of metal and non-metal gives interesting results.

You need to reduce the band gap of titania by doping. Otherwise you can think of Z scheme catalyst using some visible light absorbing semiconduct with titania

You can find useful citations in this review article about TiO2 doping:

Photocatalytic purification of volatile organic compounds in indoor air: A literature review (Atmospheric Environment journal)

I recommend the article "Doped-TiO2: A Review " Adriana Zaleska (Recent Patents on Engineering 2008, 2, 157-164) http://www.benthamscience.com/eng/samples/eng2-3/0002ENG.pdf

Holes mediated coupling is very famous method to reduce the band gap, please read the

http://onlinelibrary.wiley.com/doi/10.1002/cphc.201100313/pdf

http://astro1.panet.utoledo.edu/~yyan/PDF/pubs/double_hole_mediated_coupling_y_yan_2011_phys_rev_lett.pdf

Excellent collection of advices thanks every body...

Im was trying to do it with Nitrogen doping ....is any one having idea as to what method gives the best catalytic activity,,,, N, Cds...etc

for beginning I advice You sol-gel method because it's simple and requires moderate conditions, no sophisticated equipment. Can I ask You, what kind of experiments You think to do? Antibacterial, pollutants decompositions, influence on living organisms or others?

Thanks Michal,

I am trying to an antibacterial study...

Visible light activity of TiO2 can be improved by doping with metal or non metals and synthesis of hybrid photocatalyst. Especially carbon doped TiO2 enhances the visible light activity. i am also agreed with Mr. Michal, go for sol-gel methods. Also please go through the following article 1)http://pubs.acs.org/doi/pdf/10.1021/jp204364a ; 2) http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0019982 . the second article is related to your field (antibacterial activity)

Great...they are very relevant to me...

Thanks for sharing

One of the methods would be to form heterojunction with some other binary oxide or sulphide semiconductors so that we can prevent electron hole recombination.

U can dope with non metals , metals to improve the photocatalytic activity or even reduced forms of titania can even work as a visible light materials.

See a recent article soon should be in press, I believe is now as accepted article in Applied Catalysis B by Pelaez et al ; it discusses exactly this topic

I've doped TiO2 with porphyrins and metalloporphyrins and I've obtained good results when used as photocatalysts for aromatics photooxidation with visible light. Didn't used these materials in antibacterial studies though :).

Good point .......So it can be doped it with Blood... (hemoglobin) ):

Im work with a hydrothermal syntesis of TiO2 P25 and transform them in nanowires doped with nitrogen. The results to degradation of phenol in visible light is not so good yet because the variables of the process. Im work now to improve the techique.

What do you all think about this method

Improving the visible light photocatalytic activity of nano-sized titanium dioxide via the synergistic effects between sulfur doping and sulfation Yuxiao Niu et al,

http://www.sciencedirect.com/science/article/pii/S0926337311006096

In my opinion, intensity of absorption in visible range (Fig.2a) is relatively quite small, only slightly differs from the pure TiO2. But maybe it's enough to absorb such amount of light for photocatalysis.

In the following work I have improved photocatalytic efficiency of TiO2 by about 20%, but it needs UV activation.

Is there any photosensitizers or any further doping material available which reduce the band gap of TiO2 or amplifies visible light energy to that of TiO2 ?????

'Comparative study of photocatalytic activity of nano-TiO2 & CNT/TiO2 nano-composite in degradation of organoc dyes'.

Vishal Udmale, Pradeep Mishra, Ajay Patil, Ramesh Yamgar

Journal Article: Advance Materials in Industries 02/2012; 1(1):78.

Sayed, could you give title of article & journal on you research?

I am working in mesoporous TiO2 microsperes. there ia a recent paper "You have full text access to this content

Chemistry - A European Journal Volume 18, Issue 17, Article first published online: 13 MAR 2012" with Au doped Mesoporous TiO2 for visible light activity. I think tis must work for your research...................

Put it on nanostructures, and dope with W:

http://pubs.acs.org/doi/abs/10.1021/ja808426h

Sensitization of TiO2 vith a visble light photosensitizer. Photostability of the sensitizer should be taken in to account..

With respect to above suggestion which is better doping strategies or dye sensitization strategy?

I think using dyes for sensitization is easier and the results are good too :).

Using PLD techniques as we do, I think doping is easy as well. I do not have experience to mix dyes with Ti oxide. Pobably a chemical technique is required.

Doping of metal, non metal will improve your photocatalytic activity up to certain extend, however you will find some leaching of doped material after photocatalytic reaction if you are using this photocatalysts in aqueous conditions.

@Michael: the dyes are adsorbed, it's a very simple process :)

What dyes absorbed the visible light most ? Dyes which are non-toxic to human ?

Ruthenium photosensitizers

http://pubs.acs.org/doi/abs/10.1021/es001245e?journalCode=esthag&quickLinkVolume=35&quickLinkPage=966&selectedTab=citation&volume=35

Ruthenium complexes have suitable biocompatibility

http://pubs.rsc.org/en/Content/ArticleLanding/2011/PP/c0pp00275e

@Kithsiri Senanayake: I am working with porphyrins/metalloporphyrins and phtalocyanines/metallophtalocyanines. They are very good visible light adsorbers

Have you check the hemoglobin?

Not yet, but if time will permit and I'll get my hands on some hemoglobin, maybe I'll try :).

I would add also to Mr. Ali's comment that doping with transition metals also helps to decrease band gap energy, for example tungten (W). Also combination of metal-nonmetal dopants increases activity and photoabsorbtion.

Hi KithSiri,

TiO2 itself is a bit toxic. You can dope TiO2 with Au (non-toxic and absorbs light in visible region when in the form of nanoparticles).

Doping actually improves vis absorption of titianium dioxide as talked times above, however, doping brings combination centers of charge carriers,with other reasons decreasing photoactivities. Dyes have problem of stability. Efforts in improving sustainable vis photoactivities of TiO2 is underway.

Sustainable visible light photo activity of Tio2 nano particles, a good topic to discuss

Does any researches published...

Journal of Hazardous Materials, 2009,170:560–569 tells "Strategies of making TiO2 and ZnO visible light active".

this next one may work for you. http://www.hindawi.com/journals/ijp/2008/258394/

Doping with metals is one way but they will act as recombination centres , doping with dyes leads to the degradation of dye itself .The only simple method is doping with non-metals according to my thought.

http://xa.yimg.com/kq/groups/3004572/2070042273/name/A_review_and_recent_developments_in_photocatalytic_watersplitting_using_TiO2_for_hydrogen_production.pdf

hi just try doping with TiO2 with Au; http://www.hindawi.com/journals/ijp/2012/532843/

Visible light photocatalyst TiO2 is already commercially available. Have you already evaluated these?