Gold, colloidal reactions

The use of tetraoctylammonium salt as phase transfer reagent has been introduced by Brust [199] for the preparation of gold colloids in the size domain of 1-3 nm. This one-step method consists of a two-phase reduction coupled with ion extraction and self-assembly using mono-layers of alkane thiols. The two-phase redox reaction controls the growth of the metallic nuclei via the simultaneous attachment of self-assembled thiol monolayers on the growing clusters. The overall reaction is summarized in Equation (5). 

Dou X., Yamaguchi Y., Yamamoto H., Doi S., Ozaki Y., NIR SERS detection of immune reaction on gold colloid particles without bound/free antigen separation, J. Raman Spectrosc. 1998 29 739-742. 

Gold colloid with smaller diameter is made by reduction of the tetrachloroauric acid with a citrate/tannic acid reaction mixture given in Table 4.4. 

Under different reaction conditions, both thiol-ssDNA and -dsDNA stabilize gold colloids, but possible nonspecific interactions between the hydrophobic DNA bases and the gold surface have been observed. Moreover, interparticle interactions are promoted by the formation of hydrogen bonds between DNA bases causing aggregation within a rather short period of time.194... 

Guo and co-workers have synthesized trioctyl phosphine oxide (TOPO) stabilized iron nanoparticles by the microemulsion method with an average diameter of 3 nm [192]. The amorphous particles are known to effectively catalyze reactions such as the decomposition of H2O2. A specific advantage of this method is that the presence of O2 does not hamper the electrocatalytic currents obtained for H2O2. Gold colloids capped with a mixed monolayer of alkylthiol and amidoferrocenyl-... 

Step 4 Absorption of each tube at 520 and 580 M52()-A580) was determined. As shown in Fig. 5, the minimal antibody to stabilize 1 mL of gold colloidal suspension was approximately 8 Xg anti-carbaryl antibody. The antibody was determined to be 120% of the minimum concentration to ensure complete reaction with the colloidal gold particles. Under gentle stirring in ice bath, anti-carbaryl antibody was added drop by drop to the gold colloidal suspension within 20 min. 

Others authors propose alternative ways to conduct or discuss an experiment that is already commonly used in the teaching of chemical kinetics. For example the presentation of a videotaped clock (iodine-azide) reaction which is suitable for videotaping and which has an easily determined mechanism (Haight Jones, 1987) the determination of a reaction mechanism of the blue bottle reaction (Engerer Cook, 1999). Others may be used to discuss thermodynamics and kinetics simultaneously, e.g., from the study of the surface of nanomaterials (such as a gold colloid monolayer) (Keating, Musick, Keefe Natan, 1999), and from the study of a chemical equihbrium in solution (Leenson, 1986). 

The red-brown silver-gold colloidal solution was formed in toluene and in toluene solution of PEPC as a result of the interphase synthesis. The color of the solutions started to change from yellow to reddish-brown after the reaction had proceeded for 1-2 min. The color of the solutions turned more intensive with the time in all cases. 

N. Nagahori and S.-I. Nishimura, Direct and effieient monitoring of glyeosyl-transferase reactions on gold colloidal nanoparticles by using mass spectrometry, Chem. Eur. J, 12 (2006) 6478-6485. 

Gold nanoparticles (2.5-7.5 nm diameter) were obtained by Martino and others [402] by reduction of AUCI4 via lithium borohydride in tetrahydrofuran in the reverse micelle system DDAB (didodecyldimethylammonium bromide)/toluene. A purple-colored gold colloid was observable. The particles were encapsulated by silica gels formed in the micellar system by hydrolysis-condensation of TEOS or a prehydrolyzed TEOS, already added in the system. Gelation of silica was achieved by the addition of tetrabutylammonium hydroxide (quicker in case of pre-hydrolyzed TEOS). The particle size was found to be independent of reaction stoichiometry, gel precursor type (TEOS/pre-hydrolyzed TEOS) and the washing step after synthesis. 

First, cores of silica nanoparticles are fabricated as described by Stober et alP in which tetraethyl orthosilicate is reduced in NH4OH in ethanol. Next, the silica surface is aminated by reaction with aminopropyltriethoxysilane in ethanol. Gold shells are then grown using the method of Duff et Briefly, small gold colloid (1-3 nm) is adsorbed onto the animated silica nanoparticle... 

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