In college, probably not. Nanotechnology is more materials science or mechanical engineering, and professors are usually expected to have a Ph.D. in the field they are teaching, so you wouldn't qualify to be a physics professor.
In community college, possibly, although I don't really know much about teaching here.
In high school, also possibly, although most states have additional teaching credentials that need to be obtained. I'm familiar with CA, where the normal path is a 1 year credentialing program that includes student teaching. "Emergency" credentials are also possible, where a district that wants to hire you can apply for special permission to hire you without a credential. (NCLB makes this a little less likely though, because it makes the teacher statistics for the school look worse.)
At the college level usually there are enough physics PhDs around that it's rare for someone tangential to the field to be teaching physics. That said it's not unheard of for physics departments to hire adjuncts or temporary lecturers on an as-needed basis and in some cases the right person for the job may have a backgroung outside of physics.
Teaching at the high school level normally requires some kind of teaching qualification (depending on your location). So this is possible, but you may have to go throgh a program to get that qualification first.
My physics professor ( at a community college) has a Phd in Mechanical Engineering. He is relatively new as well. He just became head of the physical science division and also teaches Chem. So, from the sample size of 1 I would say yes you can teach at a 2 year college.
But it also depends on what "nanotechnology" means in this context, it can basically mean anything that deals with small things (sometimes "nanoscience" is even used for things like biochemistry). There are lots of physicists who work on nanoscience (I got my PhD in physics from the Department of Microtechnology and Nanoscience at my university, I could have asked for my PhD diploma to say "nanoscience" instead).
Hence, the actual topic of you PhD and also in which journals you publish will also matter (if most people in your field publish in journals with the name " physics" in it, I'd say you could consider yourself working in physics)