The Structure Of Colloidal Gold

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Colloidal gold, also called gold sol, is a suspension of gold particles formed by reducing gold salts to original gold. Colloidal gold particles are composed of a basic gold core (atomic gold Au) and a double ion layer surrounding it. The inner layer of negative ions (AuC12-) is attached to the surface of the gold core, and the outer ion layer H+ is dispersed in the intercolloid solution. , In order to maintain the state of suspension of colloidal gold free in the sol.
The basic gold core of the colloidal gold particles is not an ideal spherical core. The smaller colloidal gold particles are basically spherical, and the larger colloidal gold particles (generally larger than 30nm) are mostly elliptical. The particle morphology of colloidal gold can be observed under an electron microscope.
Chloroauric acid (HauC14) is the main reducing material. Gold sol is prepared by various methods of reduction. Common reducing agents include sodium citrate, tannic acid, ascorbic acid, white phosphorus, sodium borohydride, etc. According to the type of reducing agent and the strength of the reducing effect, colloidal gold ranging from 0.8nm to 150nm can be prepared. Common preparation methods:
UV light-induced reduction can prepare gold sol-the reduction process undergoes a free radical mechanism. The changes in the state of the sol at different reaction times were observed by UV-visible spectroscopy. The results showed that gold sol particles appeared obviously after 2 hours of light reaction, and the conversion of chloroauric acid was basically completed after 7 hours. At the same time, the effect of the addition of stabilizer polyvinylpyrrolidone (PVP) on the reduction process was studied, and the results showed that the addition of PVP not only stabilized the sol, but also reduced the reaction rate. The morphology of the sol particle aggregates was observed by SEM. Finally Using 1,4-bis(4-vinylpyridyl)phenylene as a probe molecule, the SERS activity of this sol was studied.