title: Impact of heat on nanocrystalline silver dressings. Part II: Physical properties.
abstract: This work explores the effects of elevated temperature on the physical and chemical properties of nanocrystalline silver, and relates it to previously observed thermally induced changes in biological activity [Taylor PL et al. Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040]. Microstructural evolution of nanocrystalline silver dressings, heat-treated for 24 h at temperatures from 23 to 110 degrees C, was studied in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These analyses indicated that silver nanocrystalline coatings undergo significant changes in structure when exposed to elevated temperature. XRD analysis showed a rapid increase in crystallite size above 75 degrees C along with decomposition of crystalline silver oxide (Ag2O) at the onset of crystallite growth. SEM imaging showed a loss of fine features and sintering of the structure at elevated temperatures. The XPS data indicated that silver-oxygen bonds disappeared completely, with the initial decomposition occurring between 23 and 37 degrees C, and total oxygen in the coating decreased from 16-17% to 6.5% over the temperature range of 75-110 degrees C. A comparison of these results to the data of Taylor et al. [Biomaterials, in press, doi:10.1016/j.biomaterials.2005.05.040] indicates that the unique biological properties of nanocrystalline silver are related to its nanostructure. This should guide future development of therapeutic nanocrystalline silver delivery systems.
authors: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G6.
authors: P L
authors: PL
authors: Taylor
authors: O
authors: O
authors: Omotoso
authors: J B
authors: JB
authors: Wiskel
authors: D
authors: D
authors: Mitlin
authors: R E
authors: RE
authors: Burrell
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000737:chemistry; D001458:Bandages; D001672:Biocompatible Materials / Q000008:administration & dosage / Q000737:chemistry; D003460:Crystallization / Q000379:methods; D016503:Drug Delivery Systems / Q000379:methods*; D006358:Hot Temperature; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012834:Silver / Q000008:administration & dosage* / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D012834:Silver