Ideal discrete energy levels in synthesized Au nanoparticles(6.2±0.8 nm) for a chemically assembled single-electron transistor (SET) are demonstrated at 300 mK. The spatial structure of the double-gate SET
is determined by two gate and drain voltages dependence of the stability
diagram, and electron transport to the Coulomb box of a single, nearby
Coulomb island of Au nanoparticles is detected by the SET. The SET exhibits
discrete energy levels, and the excited energy level spacing of the Coulomb
island is evaluated as 0.73 meV, which well corresponds to the expected
theoretical value. The discrete energy levels show magnetic field evolution
with the Zeeman effect and dependence on the oddeven electron number of a single Au nanoparticle