Abstract
Colloidal gold nanoparticles were synthesised in aqueous solution by reaction of chloroauric acid with a range of simple aliphatic cyclic (cyclopentanone, cyclohexanone, cycloheptanone and cyclohexanedione) and linear (acetone and 3-hexanone) ketone reagents, at room temperature. The rate of reaction and particle morphology was found to be controlled by the enol content and solubility of the ketone. Cyclohexanediones produced a variety of small 20 nm particles in under 5 minutes, or larger gold nanostars, depending on the ketone isomer. Cyclopentanone was shown to produce near monodisperse 20 nm particles after 13 hours, and cycloheptanone gave polydisperse particles, but in only 50 minutes. However the linear ketones, 3-hexanone and acetone, did not produce stable colloidal suspensions. The mechanism of gold nanoparticle formation via reaction of ketones with chloroauric acid is discussed.
Highlights
Colloidal suspensions of gold nanoparticles (AuNPs) are a current focus of research within the eld of nanotechnology
In order to further probe the mechanism at work, and investigate practical synthesis of AuNPs using simple binary mixtures at room temperature, we report here an investigation of ve cyclic ketones, including two diketones, and two examples of linear ketones
Cyclohexanone has been previously shown to react with chloroauric acid (HAuCl4) at room temperature in a self initiating reaction, to produce gold nanoparticles (AuNPs) of average dimension ca. 40 nm
Summary
Colloidal suspensions of gold nanoparticles (AuNPs) are a current focus of research within the eld of nanotechnology. They have applications in bio-labelling, drug delivery, and single molecule detection, due to their small size, tuneable morphology, surface plasmon resonance (SPR) bands and ease of surface functionalisation.[1,2,3,4,5] AuNPs are widely incorporated into colorimetric, uorometric, electrochemical and Raman based sensing mechanisms for toxic and dangerous materials such as explosives, heavy metals and nerve agents.[6,7,8] In particular Surface Enhanced Raman Spectroscopy (SERS) has shown great potential for detection of trace amounts of these substances, with gold nanoparticles or nanostars as the enhancement agent.[9,10,11]. The most common synthetic routes for production of gold colloid are the Turkavich/Frens and Brust syntheses.[12,13,14,15] The former employs boiling sodium citrate solution and the latter sodium borohydride with organic solvents. Other morphologies have been formed, such as nanostars, by use of pre-formed Au seed particles.[5,17] In 2004 the rst demonstration of controlled formation of AuNPs by b-diketones was presented.[18]
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