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    STUDIA CHEMIA - Ediţia nr.1 din 2007  
         
  Articol:   LYSINE MEDIATED ASSEMBLY OF GOLD NANOPARTICLES.

Autori:  OSSI HOROVITZ, AURORA MOCANU, GHEORGHE TOMOAIA, DIANA DUBERT, TRAIANOS YUPSANIS, MARIA TOMOAIA COTIŞEL.
 
       
         
  Rezumat:  This paper reports the data of an investigation of the gold nanoparticles assembly mediated by organic molecules, such as lysine. Gold nanoparticles were synthesized in citrate aqueous solution and characterized by UV-Vis spectroscopy and a strong absorption band at 528 nm is found for surface plasmon resonance. Transmission electron microscopy (TEM) images indicate a mean gold nanoparticle size of about 14 nm. The aqueous colloidal gold solution is stable in time, indicating a good electrostatic stabilization of gold nanoparticles through the adsorbed monolayer of citrate anions on nanoparticle surface. The interaction between the citrate capped gold nanoparticles in aqueous solution and lysine was investigated monitoring their UV-Vis spectra. At a certain lysine/gold ratio a new, large absorption band appears between 600 and 700 nm, which increases in time, while the color of the colloidal gold solution changes from red to blue. The 528 nm band decreases, as a consequence of the assembly formation of gold nanoparticles mediated by lysine. The nanostructure of the lysine mediated assembly of gold particles is analyzed by TEM and atomic force microscopy (AFM). The TEM and AFM images evidence the assembly of gold nanoparticles, where particles are not in direct physical contact. This effect could be explained primarily through the zwitterion-type electrostatic interactions between the charged amine and acid groups of the lysine molecules adsorbed and bound to different gold nanoparticles. These findings provide new insights into the precise control of interfacial interactions between organic molecules anchored on gold nanoparticles.  
         
     
         
         
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