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    STUDIA CHEMIA - Ediţia nr.3 din 2007  
         
  Articol:   AMINO ACIDS BINDING TO GOLD NANOPARTICLES.

Autori:  OSSI HOROVITZ, AURORA MOCANU, GHEORGHE TOMOAIA, MARIA CRISAN, CSABA RACZ, MARIA TOMOAIA-COTISEL.
 
       
         
  Rezumat:  Gold nanoparticles capped with citrate anions were synthesized and characterized by UV-Vis spectroscopy; a strong absorption is identified at about 528 nm, corresponding to the surface plasmon resonance (SPR). The gold nanoparticles were analyzed by transmission electron microscopy (TEM) and TEM images indicate a mean gold nanoparticle size of 14 nm. The colloidal gold aqueous solution is stable in time, indicating a good electrostatic stabilization of gold nanoparticles through the adsorbed monolayer of citrate anions on gold nanoparticle surface. The interaction between the citrate capped gold nanoparticles in aqueous solution and various amino acids was investigated monitoring their UV-Vis spectra. Some of the tested amino acids, like glycine, isoleucine and asparagine, showed little interaction with gold nanoparticles. However, other amino acids, such as lysine, arginine, glutamic acid, histidine, cysteine and methionine, presented an absorption decrease of the colloidal gold solution at 528 nm and a bathochromic shift of the absorption maximum. At higher amino acid:gold molar ratios a new, large absorption band appears in the range of 600 to 700 nm, which increases in time. As a consequence of the assembly formation of gold nanoparticles, the color of the colloidal gold solution changes from red to blue. Further, TEM and atomic force microscopy (AFM) images evidenced the arrangements of gold nanoparticles mediated by amino acids. The analysis of AFM images indicate a close packed and an almost equidistant arrangement of gold nanoparticles coated by amino acids, especially for cysteine, arginine and lysine. These arrangements indicate a stabilization effect, mediated by these amino acids bonded to gold nanoparticle surface.  
         
     
         
         
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