Lab Report

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Usually, the clusters produced using thiols are much larger (approx. 25 atoms) than the ones that produced by bottom-up electrochemical and chemical procedures (2 to 20 atoms). The possibility of etching gold nanoparticles by the organic compounds such as thiols and in our case selenols can be assumed taking in consideration the great reactivity of selenol group relative to thiol group and that is the reason of the fast formation of the clusters [28]. These strong binding ligands break the nanoparticles into clusters with 5-9 atoms (top-down clusters-synthesis). TEM images in figure 3 show the etching process of gold nanospheres into gold clusters by using organoselenium compound (1). The compound (1) contains four types of H-bonding, two …show more content…

When the concentration of the gold clusters increased, the aspect ratios of the formed rods increased from 18 to 23 (figure 5 b-d), respectively. The longitudinal plasmonic band that characteristic to gold rods cannot be seen with these high aspect ratios because these bands appear at more than 1200nm as shown in figure 5a. The formed clusters could be adsorbed onto particular surfaces of the gold seeds [6, 7, 31], and can then act as a catalyst enhancing the growth of the GNRs (atomic metal clusters are now recognized as efficient catalysts [30]). The adsorption of these clusters on one of these facets, is leading to break the growth symmetry, and enhancing the growth of one of these facets much more than the others, which leading to the formation of rod shaped particles [7]. Herein, we use a model reaction, i.e. the reduction of p-nitrophenol (PNP) to p-aminophenol (ANP) to evaluate the catalytic activity of the formed clusters in organic reaction. Without the addition of clusters as a catalyst, 4-nitrophenol was mixed with NaBH4 to form a yellow solution that had maximum absorbance at 400 nm. This peak is characterized to 4-nitrophenol anion[32]. Upon the addition of clusters, the peak at 400 nm started to decrease while a new peak

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