Fetilar Pour 20 mL of 1. If substances other than salt and sugar are added to the nanoparticle solution, dispose of the nanoparticle nanowor,d using methods appropriate for solutions containing those substances. Are there components in either solution that are charged? After the solution begins to boil, add 2 mL of How did your observations compare with your predictions? The sodium citrate reduces the Au ions to nanoparticles of Au metal.

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You are on page 1of 2 Search inside document Sample Student Activity Color My Nanoworld One nanometer is 10, times smaller than the diameter of a human hair. Can you imagine producing and using nanometer-sized materials? Nanoscience investigates the properties of these materials. By understanding these properties and learning how to utilize them, scientists and engineers can develop new types of sensors and devices.

This technology could have a huge impact on diagnosing diseases, processing and storing information, and other areas.

Physical and chemical properties are size-dependent over a certain size range specific to the material and property. When a particle of gold metal is similar in size to wavelengths of visible light nm , it interacts with light in interesting ways. The color of a gold nanoparticle solution depends on the size and shape of the nanoparticles. Consider this analogy: tapping a spoon on a glass bottle partly filled with water generates a sound.

Vary the volume of water in the bottle and the tone of the sound changes. The tone is dependent on the volume of water. Similarly, the volume and shape of a nanoparticle determines how it interacts with light. Accordingly, this determines the color of a nanoparticle solution. For example, while a large sample of gold, such as in jewelry, appears yellow, a solution of nano-sized particles of gold can appear to be a wide variety of colors, depending on the size of the nanoparticles.

In this Activity, you will work with a type of suspension called a colloid. As a suspension, a colloid is one phase of matter in this case, a solidgold dispersed in another phase in this case, a liquid. A colloid is distinguished from other types of suspensions by the smallness of the particles so small that they do not separate from the continuous phase due to gravity.

In other words, they do not settle to the bottom or rise to the top. If they were smaller, they would not be a separate phase; they would be part of a solution. Thus they are nanoparticles. The gold nanoparticles are covered with citrate anions. This prevents them from aggregating, i. You will explore how the size of the gold nanoparticles can be changed and how changing their size Left:Atransmissionelectronmicrograph TEM of13nmdiameter affects their color.

Right:AnillustrationofanAunanoparticle Try This surface. Eachnanoparticleismadeofmany morethan, Auatoms. You will need: 1. Pour 20 mL of 1. Add a magnetic stir bar. After the solution begins to boil, add 2 mL of Continue to boil and stir the solution until it is a deep red color about 10 min.

As the solution boils, add distilled water as needed to keep the total solution volume near 22 mL. How does the solution visibly change? The sodium citrate reduces the Au ions to nanoparticles of Au metal.

Excess citrate anions in solution stick to the Au metal surface, giving an overall negative charge to each Au nanoparticle. When the solution is a deep red color, turn off the hot plate and stirrer. Glovesshouldbeworn whenworkingwiththenanoparticle solution.

Rinseusedsolutionsdownthe sink. Ifsubstancesotherthansaltand sugarareaddedtothenanoparticle solution,disposeofthenanoparticle solutionusingmethodsappropriatefor solutionscontainingthosesubstances. Make a predication: read over the procedure. Think about the composition of each solution that will be added to the gold colloid: table salt sodium chloride, NaCl and table sugar sucrose, C12H22O Recall that the gold nanoparticles in the colloid are negatively charged.

Are there components in either solution that are charged? Predict whether the addition of each solution to the colloid will affect the size of the gold nanoparticles. Predict whether the color of the colloid will change. Think back to the DNA-coated gold nanoparticles described in the Introduction. Give reasons for your predictions. Make a datatable. In a small container, dissolve 0. Label the four glass vials or clear, colorless plastic cups: control, salt, sugar, and test, respectively.

Into each vial, place 3 mL of the gold nanoparticle solution you prepared in Part A. Add 3 mL distilled water to each vial. With a dropper, add drops, one at a time, of the salt solution from part B, step 3 to the salt-labeled vials. Record your observations. Refer to the control solution for comparison.

What is happening to the nanoparticles in solution? Using a clean dropper, add drops, one at a time, of the sugar solution from part B, step 4 to the sugar-labeled vial. Choose another substance to add to the fourth vial.

One suggestion is a household liquid such as vinegar. Check with your instructor about your choice. Before adding the substance, predict whether or not a color change will occur. Questions 1. Based on the fact that the citrate anions cover the surface of each nanoparticle, explain what keeps the nanoparticles from sticking together aggregating in the original solution. Why does adding the salt solution produce a different result from adding the sugar solution? How does the color of gold colloid you worked with compare to that of a gold coin?

Why is there a difference? How did your observations compare with your predictions? Give possible reasons for any differences. The system you worked with in this activity involves huge numbers of nanoparticles. How might scientists be able to detect individual nanoparticles?

How could the effect in part B be used to detect the binding of biomolecules, such as DNA or antibodies, that stick to one another or to other molecules? How could these molecules be used to cause aggregation of the nanoparticles? Information from the World Wide Web 1.





Color My Nanoworld




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