Nanoparticles can be produced by decomposing solids at high temperature having metal cations, and molecular anions or metal organic compounds. This procedure is termed to as Thermolysis. For instance, small lithium particles can be made by decomposing lithium azide, LiN3. The material is placed in an evacuated quartz tube and heated to 400°C in the equipment shown below. At about 370°C the LiN3 decomposes, releasing N2 gas, which is observed by an increase in the pressure on the vacuum gauge. In a few minutes the pressure drops back to its original low value, indicating that all the N2 has been removed. The remaining lithium atoms coalesce to form small colloidal metal particles. Particles less than 5 nm can be made by this method.
The presence of these nanoparticles can be detected by electron paramagnetic resonance (EPR) of the conduction electrons of the metal particles. Electron paramagnetic resonance, measures the energy absorbed when electromagnetic radiation such as microwave induces a transition between the spin states ms split by a DC magnetic field.
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