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Gold nanoparticles synthesis methods

Gold nanoparticles have photonic and biocompatible properties and hence they are widely used in electronic wiring, optics, photonics, optoelectronics, catalysis and biomedicine. But the intrinsic characteristics of gold nanoparticles are primarily dependent on their size and shape obtained by different synthesis methods. In general, gold nanoparticles are produced in an aqueous solution through the reduction of chloroauric acid (HAuCl4). Of these methods, Turkevich water based and Brust organic liquid based methods are the most widespread used approaches, but both the methods require a reducing agent to reduce Au3+ ions to neutral gold atoms, and a suitable stabilizer to prevent the synthesized gold nanoparticles from aggregation.


Turkevich method

In the Turkevich method, sodium citrate is usually used as both the reducing agent and the stabilizer, although other reductants, such as amino acids can also be used. Using this method spherical gold nanoparticles 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.

Brust method

In the Brust method, sodium borohydride (NaBH4) and tetraoctylammonium (TOAB) are used as the reducing agent and the stabilizer, respectively. The synthesized gold nanoparticles are around 5-6 nm.

Reductant and stabilizer-free approach

A reducing agent and stabilizer free method is based on the electrochemical deposition technique. The barrier layer of an anodic aluminum oxide (AAO) film is used as the template; a gold thin film is deposited on the surface of the barrier layer; gold nanoparticles are then uniformly deposited on the gold thin film by electrochemical deposition. The distribution density and size of the nanoparticles can be well controlled by the applied potential for the electrochemical deposition.

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