Well the 'counterterrorist' and 'homeland security' bit may be paranoia… but given how some environmental regs work…. toxin sensors like this might be very useful.

I just found an article from the Russian news agency Rosbalt, mentioning research by Moscow State University. Apparently chemists and biotechnologist there have developed similar toxicology sensors. Not too surprisingly paranoia is driving nanotech research both here and abroad.

There is a big difference between macroscale detectors that can detect dozens or hundreds of molecules and nanoscale machinery that hasn't even been designed yet. There are more atoms in a nanoassembler than there are parts in a Boeing 767. The design problem is big and the assembly problem is even bigger.