Gold aggregation

Gold aggregation test is preliminarily carried out to judge the... 

The antibody concentration which prevents gold aggregation is determined by measuring the difference between the absorbance at 520 and at 580nm and plotting it against the concentration used (reeNote 5). 

Another application of a photochromic reaction involves the reversibile size control of gold aggregates in nanoparticles by using 5-functionalized spiropyran derivatives. In the dark, the merocyanine form associates with each other, which suppresses the thermal rearrangement. Irradiation, on the contraiy, accurately tunes the dimension of the aggregates due to the different electrostatic properties of spiropyran and merocyanine (Fig. 3). In photocatalysis the effect of changing parameters is often limited, because the process of photon absorption photoexcitation of adsorbate -metal bond occur at some distance. It has recently been shown that when sub 5 nm metal particles are used, the hybridized absorbate-metal ions is excited preferentially. This results is an increased proportion of CO oxidation in H2 rich streams (Fig. 4). ... 

Fig. 3 Reversibile size control of gold aggregates in nanoparticles and compounds. Reprinted with permission from Y. Shiraishi, E. Shirakawa, K. Tanaka, H. Sakamoto, S. Ichikawa and T. Hirai, ACS Appl. Mater. Interfaces, 2014, 6, 7554. Copyright 2014, American Chemical Society.

Another application of a photochromic reaction involves the reversible size control of gold aggregates in nanoparticles by using S-functionalized spiropyran derivatives. In the dark, the merocyanine form associates with each other, which suppresses the thermal rearrangement. Irradiation, on the contrary, accurately tunes the dimension due to the different electrostatic properties of spiropyran and merocyanine (Fig. 11.10) [27]. 

Figure 5. SERS spectra of seven bacterial species obtained on gold aggregate coated Si02 chips. An incident laser power of2mW and a data accumulation time of 10 sec were used to obtain these spectra. Spectra are offset vertically for display purposes and top-to-bottom ordered according to their phylogenetic relationship.

R. G. Freeman, R.M. Bright, M.B. Hommer, M.J. Natan, Size selection of colloidal gold aggregates... 

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