The photonic and biocompatible properties of gold nanoparticles have been widely exploited for use in electronic wiring, optics, photonics, and optoelectronics, for analytical separation of organic compounds, catalysis and biomedicine. The intrinsic characteristics of gold nanoparticles are primarily dependent on their size and shape.

Production

In general, gold nanoparticles are produced in an aqueous solution through the reduction of chloroauric acid (HAuCl4). Of various methods, Turkevich water based and organic liquid based method of Brust are the most widespread used approaches. Both the Turkevich and Brust methods require a reducing agent to reduce Au3+ ions to neutral gold atoms, and a suitable stabilizer to prevent the synthesized gold nanoparticles from aggregating.

In the Turkevich method, sodium citrate is usually used as both the reducing agent and the stabilizer, although other reductants, such as amino acids have also been successfully used. Spherical gold nanoparticles of around 10-20 nm in diameter suspended in water can be produced. The particle size can be increased by reducing the amount of sodium citrate.

Turkevich modified method

Gold nanoparticles can be synthesized by chemical reduction method of Turkevich. The synthesis of gold nanoparticles by this method requires the reduction of AuCl−4 ions to gold nanoparticles. The synthesis can be done by a modified Turkevich method. Solutions of HAuCl4.3H2O, L- In this method tryptophane and polyethylene glycol 1000 at concentration of 2.25 mM and 3.3% were prepared respectively. Then 10 mL of HAuCl4.3H2O is heated to its boiling on a magnetite stirrer, to which, 15 mL of reducing agent is injected. Heating is continued till the color of the solution changes from colorless to pink/red. Three milliliter of 3.3% polyethylene glycol 1000 at room temperature is added to the above mentioned solution. Thus AuCl−4 ions are reduced to gold nanoparticles.