i am scoring around 185-190 in iit-2011,will i be ab;e to get nano tech in iit,and what will be my expected rank

As per what marks you have mentioned above in your message you can expect your rank somewhere around 9000-10000 and with that rank there would be a less chance for you to get into IIT but you can look for other colleges if you specifically want to study Nanotechnology such as-

 Amity University

University of Rajasthan

Institute of Technology (NIT), Rourkela

Jamia Millia Islamia, New Delhi

Indian Institute of Science, Bangalore

University of Madras, Tamil Nadu

Maulana Azad National Institute of Technology, Bhopal 

Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore.