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To learn more about our privacy policy Click hereColloidal gold is a certain-size gold particle synthesized by gold ion reduction and polymerization of chloroauric acid (HAuCl4) under the action of reducing agents such as white phosphorus, ascorbic acid, sodium citrate, tannic acid, and so on. Due to electrostatic action, gold particles repel each other and suspend into a stable colloidal state, forming a negatively charged hydrophobic colloid solution, so it is called colloidal gold. Colloidal gold has high electron density and can conjugated with a variety of biological macromolecules (such as protein, SPA, PHA, and ConA). It has become a commonly used non-radioactive tracer in immunolabeling technology after fluorescein, radioisotope, and enzyme. The particle size of colloidal gold is generally between 1-100nm, which can be uniformly and stably dispersed in the liquid, showing small spherical particles or large oval particles.
Producing Quality Colloidal Gold
Colloidal gold is mainly prepared by chemical reduction method, that is, various reducing agents are added to the aqueous solution of chloroauric acid to polymerize gold ions into colloidal gold. The reduction method can be regarded as a crystallization process, and the particle size depends on the crystal nucleus formation rate and crystal growth rate caused by the reducing agent. The commonly used reducing agents are white phosphorus, ascorbic acid, citric acid, tannic acid, sodium borohydride, hydrogen peraminate, and ethanol.
Colloidal gold has high dynamic stability, and its own condensation is very slow when the stability factors are not changed, and it can be placed for several years without condensation. The main factors affecting stability are electrolyte, sol concentration, temperature, non-electrolyte, and so on. Colloidal gold solution must have a small amount of electrolyte as a stabilizer, but the concentration should not be too high. A high concentration of hydrophilic non-electrolyte can peel off the hydration film outside the colloidal particles and make it agglomerate. A small number of macromolecular substances can promote sol coagulation, but a certain number of macromolecular substances can increase the stability of sol, such as the addition of protein, glucose, PEG20000, etc. have a good stabilizing effect.
How to better characterize and analyze the particle size of micro-nanoparticles and the state in the solution is very important for the use of colloidal gold. Transmission electron microscope is suitable for characterizing gold nanoparticles below 50nm and quantum dots of 2-10nm; scanning electron microscope is suitable for surface morphology characterization of particles from 50nm to micron level; dynamic light scattering can measure and analyze the state of particles from 0.3nm to 10 μ m in solution. The light extinction liquid-borne particle counter can measure the state of particles more than 0.5 μ m in solution, as well as the particle size distribution and the number of particles, etc., and it can also analyze whether particles gather in a specific solution.
Safe Handling and Storage of Colloidal Gold
Colloidal Gold Applications Across Fields
Gold nanoparticles play a wide role in biomedical and chemical industries because of their high catalytic activity, good biocompatibility, excellent electrical conductivity, and a series of nano-effects.
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