CHE 120 Intro

CHE 120 Intro - One such property we will observe during...

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Introduction One class of nanostructure are the nanocrystals. Most people are familiar with the larger crystals such as diamond composed of carbon atoms. Other types of crystals we utilize everyday that you may not know about are crystals with sizes in the range of 1 to 10 micrometers. These micro crystals can be found in integrated circuit (IC) chips that control all electronic devices we use today. These chips are fabricated from many silicon atoms into small single crystals. Other materials such as the wires connecting the IC chips to the devices are polycrystalline, which are made up of many of these micro crystals. When you start looking at crystals that are even smaller, with dimensions below 100 nm (nanometer), their properties are distinct from the “bulk” properties of the same material. These very small crystals are called nanocrystals. The properties of nanocrystals are unique and dependent on their size. By controlling the size of these crystals, we are able to their properties.
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Unformatted text preview: One such property we will observe during this experiment is the color. Our objective for this experiment is to synthesize gold nanocrystals by chemical means. In order to synthesize the nanocrystals, we reduce Au3+ ions to Au0 with the use of Sodium Citrate. In this solution, the gold ions are dissolved into individual entities and merge together to form larger structures, or crystals. The kinetics of the reaction controls the size of the crystals, maintaining the crystals in nanoscale dimensions. From this, we will have obtained the colloidal gold nanocrystal solution. Because we know gold nanoparticles are gold in color, we can verify that gold nanocrystals are in the solution by observing the change in color to dark red. The nanocrystals are kept from coagulating to larger particles by a layer of citrate anions on its surface. With the use of a laser beam, we can also detect the presence of this colloidal suspension by the reflection of the laser from the particles....
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