Abstract
Department of Chemistry, Seoul National University, Seoul 151-742, KoreaReceived October 10, 2012, Accepted October 28, 2012We have investigated the effects of formalin on the assembly of colloidal gold nanoparticles (AuNPs) preparedby laser ablation of a solid gold target in deionized water. Upon addition of formalin, the surface plasmonresonance (SPR) band at 519 nm for pure AuNPs decreases and shifts to red while a new broad SPR bandappears at ~700 nm. The red-shift is prominent with increase in the incubation time. The average size of theinitial AuNPs is around 12 nm but it increases to 23 nm after addition of formalin. It turns out that formalin actsas a cationic surfactant for AuNPs with negative surface charge in the colloidal solutions. Furthermore, throughanalysis of the Raman spectrum of formalin and the density functional theory calculations, we confirm thatmethanediol is the main species in formalin which is in charge of the aggregation of AuNPs. Key Words : Gold nanoparticles, Formalin, Aggregation, Raman spectroscopy, Surface plasmon resonanceIntroductionGold nanoparticles (AuNPs) have attracted great attentionof researchers since they have extensive technologicalapplications as well as unique properties.
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