Synthesis of Gold Nanoparticle

Published: Thursday, 17 September 2015

The appearance of normal gold is well-known golden metallic luster. However, after reduced its size to nanoscale, the free electrons were excited by lights, and absorbs certain energy from photons and caused dipole vibration, which is so-called “surface plasmon resonance”. Since the gold nanoparticles are spherical and symmetric , its surface plasmon resonance absorption, is mainly at the wavelength of 520 nm (blue-green light), and therefore the solution will appear red color. When the shapes of gold nanoparticles are changed, for example, cylindrical, so it will absorb the longer wavelength, red light, and the solution showed purple color.

Manufacturing gold nanoparticles, one can restore sodium citrate by tetrachloroauric acid, and obtained. You can use N-1100D Rotary Evaporator, form ACTTR Technology, and quickly generate gold nanoparticle solution. Or use WH220-HT digital magnetic stirrer with the reflux heating device, however,  such a setting is relatively cumbersome.

Finally, use of the economic UV / Vis spectrophotometer,  and electron microscopy to examine the optical characteristics and appearance of gold nanoparticles.

The following is the process of production of gold nanoparticles:

Cleaning Related Equipment

First with aqua regia full immersion cleaning process will be used to experiment containers, such as flasks, stirring, measuring condenser, a pipette (quantitative straw). Subsequently, deionized water rinse. Finally, ultrapure water (resistance values ​​greater than 15 MΩ), these devices rinsed three times and dried after standing aside. Pure water manufacturing equipment, can contact potential Dynamic Technology.

Prepare HAuCl4 Solution

In 100 mL HAuCl 4 solution was added 30 mL, concentration of 1 mol / m3 (1 mM). Concentrated under reduced pressure machine using a sand bath or an oil bath, the solution was heated with stirring to boiling. (If using a reflux apparatus with a magnetic stirrer set, stir into the flask, the release as for sand bath or oil bath container and placed on a whole group of electromagnetic heating stirrer, heated to boiling)

Gold Nanoparticles Solution

Straw obtain quantitative concentration of 38.8 mM aqueous solution of sodium citrate (C6H5O7Na3), 3.5 mL (red Gold nanoparticles) or 1.5 mL (purple Gold nanoparticles), from the upper condenser was quickly added to the flask. After heating and stirring continued until the solution re-boiling, and then heated for 10 minutes, followed by heating was stopped, and stirring was continued until the solution reaches room temperature. Gold nanoparticle solution can be obtained.

Verify the Gold Nanoparticle Solution

By an UV / VIS spectrometer , one can obtain two different gold nanoparticles absorption spectrum of the solution, wherein the red solution with higher amount of sodium citrate (3.5 mL sodium citrate), has surface plasma resonance maximum absorption at the wavelength of 520 nm; with the lower amount of sodium citrate solution, the purple gold nanoparticles solution, the surface plasma resonance has the maximum absorption at thh wavelength of 528 nm. As the figure shows below:

Gold NanoparticlesThe Absorption Spectrum of Gold Nanoparticle