Hi Prof. Duttarganvi. The Directory of Open Access Journals provides a great resource for searching journals with no publication charges: http://doaj.org/
If you click on the Search tab, you'll see among the drop-down menus, "Publication charges?". You can further narrow the search through the other drop-down menus and even further through keyword searches.
There are also some open access journals that are currently not charging publication fees, but will in the future. One such journal that may interest you and your students is eLife: http://elife.elifesciences.org/
you can publish here , on the journal called : Journal of Biodiversity ... if you are interested about journals of Geography and all the conexes sciences
The journal with SCI indexed and high impact factor will charges heavy amount if they are open access. I feel that you should check the journal according to your research studies from the JCR list of Thomson. You will get many journals with their impact factor. Most of them are not open access and hence they do not charge any fee for publications.
You can also search your desired SCI indexed journal from the given site by putting abstract of your research in the blank given: