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Putting it all together

  • Page ID
    243112
  • The goal of this module was to explore how experimental parameters may affect the size, size distribution and related optical properties of gold nanoparticles with the goal of producing nanoparticles of consistent size with a well characterized molar extinction coefficient.

    It is time to put all the information together to draw some conclusions.  Complete the data in Table 6 by filling in the nanoparticle concentration and λmax as reported in Table 5 and estimating the molar extinction coefficient from the Absorbance vs. concentration plots for each experimental combination.

    Table 6. Final summary of experimental results

    Citrate/Au

    pH

    Particle
    Feret’s Diameter

    Nanoparticle concentration (M)

    λmax (nm)

    Molar extinction coefficient

    2.0:1

    4.2

    20.00 ± 0.50

     

     

     

     

    5.4

    21.73 ± 0.40

    3.16 x 10-9

     

     

     

    7.0

    21.22 ± 1.00

     

     

     

    4.0:1

    4.2

    23.30 ± 0.78

     

     

     

     

    5.4

    26.52 ± 1.57

     

     

     

     

    7.0

    26.76 ± 0.99

     

     

     

    7.0:1

    4.2

    31.87 ± 2.45

     

     

     

     

    5.4

    33.91 ± 4.25

     

     

     

     

    7.0

    No particles formed

     

     

     

    Q37. Based on the analysis of the data you summarized in Table 6, how does particle size affect the molar extinction coefficient?

    Q38. How does the citrate to tetracholoroauric acid ratio affect the molar extinction coefficient?

    Q39. Does pH play a role in the value of the molar extinction coefficient? Justify your answer.

    Q40.  If you were to develop a colorimetric sensor, what experimental conditions would you choose to synthesize nanoparticles of consistent size with a large molar extinction coefficient?

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