INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Fe K-XANES study of FexOy in Ultrathin Nanostructured Melanin Films on Au(111)
F. FERNÁNDEZ-BALDIS; L. ANDRINI; P. DIP; P.C. SCHILARDI; R.C. SALVAREZA; F.G. REQUEJO
Otro; Reunião Anual de Usuários (RAU); 2007
Melanins are complex biopolymers widely distributed in living organisms. The secondary structure of melanins is still under debate. There are strong evidence that melanin is formed by small nanometer-sized particles that aggregate forming a hierarchical structure. Moreover, melanin exhibits interesting properties such as photoactivity, semiconductor behavior, and electrochemical activity; and is interesting from the point of view of material science . In this work we explore by XANES experiments the nature of the sities of of Fe-containing nanostructured ultrathin melanin films electrochemically self-assembled on Au(111). The X-ray absorption spectra were measured at the D04B-XAS beam-line of the LNLS, Laboratorio Nacional do Luz Sincrotron, Campinas, Sao Paulo, Brazil. XANES and EXAFS spectra at the Fe K-edge for pure synthetic melanin (pure melanin) sample were recorded in air at room temperature in transmission mode. X-ray absorption data for supported melanin on Au(111) was obtained by total electron-yield mode, and XANES spectra for melanin in solution was obtained by fluorescence. The analysis of the relative concentration of Fe-species in melanin film on Au(111) by XANES indicates that the main Fe-species in Au-supported melanin corresponds to magnetite like-species (Fe3O4 nanoparticles) (~ 80 %) being Fe-species remaining in melanin nanoparticles just a minor component (~20 %).