tailieunhanh - Báo cáo hóa học: " Thermodynamic Properties of Supported and Embedded Metallic Nanocrystals: Gold on/in SiO2"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Thermodynamic Properties of Supported and Embedded Metallic Nanocrystals: Gold on/in SiO2 | Nanoscale Res Lett 2008 3 454-460 DOI s11671-008-9180-y NANO EXPRESS Thermodynamic Properties of Supported and Embedded Metallic Nanocrystals Gold on in SiO2 F. Ruffino M. G. Grimaldi F. Giannazzo F. Roccaforte V. Raineri Received 17 July 2008 Accepted 17 September 2008 Published online 9 October 2008 to the authors 2008 Abstract We report on the calculations of the cohesive energy melting temperature and vacancy formation energy for Au nanocrystals with different size supported on and embedded in SiO2. The calculations are performed crossing our previous data on the surface free energy of the supported and embedded nanocrystals with the theoretical surface-area-difference model developed by W. H. Qi for the description of the size-dependent thermodynamics properties of low-dimensional solid-state systems. Such calculations are employed as a function of the nanocrystals size and surface energy. For nanocrystals supported on SiO2 as results of the calculations we obtain for a fixed nanocrystal size an almost constant cohesive energy melting temperature and vacancy formation energy as a function of their surface energy instead for those embedded in SiO2 they decreases when the nanocrystal surface free energy increases. Furthermore the cohesive energy melting temperature and vacancy formation energy increase when the nanocrystal size increases for the nanocrystals on SiO2 they tend to the values of the bulk Au for the nanocrystals in SiO2 in correspondence to sufficiently small values of their surface energy they are greater than the bulk values. In the case of the melting F. Ruffino H M. G. Grimaldi Dipartimento di Fisica e Astronomia Universita di Catania via S. Sofia 64 I-95123 Catania Italy e-mail F. Ruffino M. G. Grimaldi MATIS CNR-INFM Catania Italy F. Giannazzo F. Roccaforte V. Raineri Consiglio Nazionale delle Ricerche Istituto per la Microelettronica e Microsistemi CNR-IMM Stradale Primosole 50 I-95121 Catania Italy .