Adsorption Kinetics of Charged Thiols Onto Gold Nanoparticles

M. G. BELLINO; E. J. CALVO; G. GORDILLO

San Carlos de Bariloche, Argentina

Conferencia; PASI 2003, Pan American Advanced Studies Institute on Physics at the Nanometer Scale; 2003

National Science Fundation, CONEA

Surface funcionalized nanopartlcles is desirable for the construction of well defined functinal nanoarchitectures. In the present work coloidal Au nanparticles have been functionalized with mercapto propanesulfonate (MPS) and mercaptoethylamine (MEA) short alckanothiols in aqueous solutions.   Both short chain alkanothiols, irrespective of their end charge produced blue shift of the av-vi spectrum and s decrease in the plñasmon band intensity of citrate formed Au nanoparticles. Adsorption kinetics of these charger thiols onto gold nanoparticles has been followed by the decrease in the plasmon band at 530 nm due to the blue shift transmission electron microscopy (TEM) . Titration curves resulted from plotting the 530 and 800 nm absorbance versus the added amound of soluble thiol, and yielded the mercaptane coverage on Au. While the adsorption of positively charged colloid is very rapid, slower and more complx adsortion kinetics have been found for the negatively charged MPS. Thus the end charge  determinas the whole derivatisation process kinetics. I.e. adsortion-floculation.. It is assumed that this arises from the electrostatics interactions between the charged thiols and the negatively charged citrate formed Au nanoparticles.             For MPS derivatization our experimental evidence suggest that the kinetics are determined by the adsorption step. Conversly, for MEA the adsorption step under strong electrical attraction would  be fast with the aggregation being rate determining.