Synthesis of monodisperse gold nanoparticles via electrospray-assisted chemical reduction method in cyclohexane

• Gold nanoparticles synthesized via electrospray-assisted chemical reduction method directly in non-polar solvent.
• The mechanism of gold nanoparticles formation discussed.
• Two methods of reagents incorporation to the reaction bath compared.
• Highly monodisperse gold nanoparticles in cyclohexane obtained.

We present a fast and versatile method of monodisperse gold nanoparticles (AuNPs) synthesis, directly in non-polar solvent at room temperature, by electrospray-assisted chemical reduction method. The electrospray technique was used to spray a dispersed aerosol of gold precursor [gold (III) chloride hydrate] into the reaction bath containing reducing agent (octadecylaminomethanol) and non-polar solvent (cyclohexane). To find the best homogeneity in the size and low polydispersity of synthesized AuNPs, two methods of reagent incorporation into the reaction bath were compared: incorporation by continuous stream flow using a capillary, and by continuous fine droplet flow using electrospray technique.The obtained AuNPs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Results confirmed the formation of AuNPs in both cases and showed that the size of NPs synthesized via chemical reduction method in non-polar solvent depends on the method of reagents incorporation. The continuous incorporation of precursor resulted in polydisperse colloid with NPs size of about: 4.4 ± 0.6 nm and 10.9 ± 1.4 nm, whereas incorporation of fine droplets to the reaction bath resulted in a highly monodisperse colloid with the NPs size of about 5.7 ± 0.5 nm.

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