Their big areas now. Nanotechnology alone is used in many fields from electrical through to mechanical, automotive, chemical, manufacturing, even cosmetics and food!
Ideally you want to follow your heart and go into an Engineering field you are interested in, chances are Nanotechnology may play a small part (larger as time progresses). Nanotechnology is and will be a specialised area, so if you are really interested in specialising in Nanotechnology you may need to look around for certain jobs in certain engineering fields.