This contribution deals with the development of a 3D Monte Carlo (MC) entropic sampling algorithm to evaluate the density of states of a SCO nanoparticles using three parameters related to the "magnetization", the "spin-spin correlation"and the number of molecules at the surface. This information is then used to analyze the role of the interaction parameter, L, between the external environment of the nanoparticle and the surface's molecules. We show that increasing "L"shifts downward the system's transition temperature, generating a thermal hysteresis whose width increases linearly with the strength of this parameter "L". These behaviors are also studied as function of the SCO nanoparticle size.