In the last years the quest for adequate  techniques to study physical systems, where the surface plays a relevant role, has become progressively more important. Among such techniques, the complex permettivity  measurements  provide a powerful method for investigating the surface phenomena due both to the very high sensitivity and the intrinsic direct dependence on the properties of the sample surface. Systems of metallic nanosized particles, where the ratio between the surface to volume atoms is high, are particularly suitable in this respect. As a cosequence in nanometric systems specific effects manifest related either to surface atoms layers or to interface conditions. Futhermore in the phenomena where also in bulk materials the surfaced atoms have a critical role,  the nanometric structure offers preferential  conditions for investigating the effect. Systems of metal nanoparticles, specifically Ga embedded in a glassy SiO_x matrix, are considered as a paradigmatic case. Capacitance and conductance measurements are accomplished as a function of frequency (20-10⁶Hz) temperature (10-300 K) and applied voltage, according to the nature of the investigated phenomenon and performed on samples of different nanoparticles sizes.

The complex melting and premelting  processes can be explored on the basis of the capacitance vs temperature behavior and of the strict relationship of the capacitance with the entropy. A sequence of transitions through metastable crystalline phases, possible in the Ga, were further detected by varying the temperature. The capacitance vs frequency and voltage  behaviour displays, in the considered systems, the phenomenon of negative capacitance, due to the presence of large interfacial surface, in the low-frequency range  4 x  10 ⁵ –  8 x 10 ⁵ Hz.