Observation of self-polarization in BSA protected Au 20 clusters.

Bovine serum albumin (BSA)-protected gold clusters (atomicity similar to 20), prepared using a wet chemical route, show strong dipolar radiative transition with a gap energy of 1.93 eV due to the high oscillator strength, as confirmed by the emission studies. Self-arrangement of the clusters with fixed atomicity yields a low dispersive dielectric and electric self-polarization nature. The electrical hysteresis loop measurements returned a remanent polarization of 0.05 mu C cm(-2), which can be correlated with the dipolar orientation (activation energy similar to 45.32 meV), originating from the structure-dependent deformation of the charge density.