Assembly of Gold Nanoparticles Mediated by Amino Acids
O. HOROVITZ, A. MOCANU, G. TOMOAIA, C. CRĂCIUN, M. TOMOAIA-COTIŞEL
Abstract. Gold nanoparticles capped with citrate anions were
synthesized and characterized by UV-Vis spectroscopy and transmission
electron microscopy. This aqueous colloidal gold solution is stable in
time, indicating a good electrostatic stabili-zation 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 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 absorp-tion decrease of the
colloidal gold solution at 528 nm. At high amino acid/gold ion mo-lar
ratios a new, large absorption band appears at 600–700 nm, which increases
in time, while the colour of the colloidal gold solution changes from red
to blue, as a conse-quence of the assembly of gold nanoparticles. The
nanostructure of amino acids capped gold nanoparticles assembly is
analyzed by TEM and atomic force microscopy (AFM). The analysis of these
images evidenced the assembly of gold nanoparticles mediated by amino
acids, where some gold nanoparticles appear to be overlapped or slightly
sin-tered and others are not in direct physical contact. |