User:Elaine Marie Robbins/Notebook/CHEM-496/2012/03/21

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BDLlogo notext lr.png Determining Au+3 Concentration II <html><img src="/images/9/94/Report.png" border="0" /></html> Main project page
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Objective

To determine the concentration of Au+3 left unreacted in solution in the fiber solution synthesized on 02/29/12 using electrochemistry.

Description

  1. Make the following dilutions of chloroauric acid:
    • 5.00 mM
    • 1.00 mM
    • 500 μM
    • 100 μM
    • 50.0 μM
    • 10.0 μM
    • 5.00 μM
    • 1.00 μM
    • 500 nM
    • 100 nM
  2. Add 0.5 mL of 0.5 M KNO3 to each solution.
  3. Run cyclic voltammetry using platinum electrodes as both working and reference electrodes.
  4. Run cyclic voltammetry on fiber solution synthesized on 02/29/12.
  5. Run cyclic voltammetry on AuNP solution synthesized on 02/09/12.

Data

  • Graph of current vs. applied potential for Pt electrodes:
Current vs applied potential 3-21-12.png


  • Graph of peak current vs. concentration of Au+3:
Peak current vs concentration 3-21-12.png


The peak current values for AuNP solution and fibers were as follows:

  • AuNP solution: -1.48*10-6
  • AuNP fiber solution: -1.78*10-6

Both values are lower than the lowest detection limit (100 μM). Thus, AuNP concentration cannot be determined with accuracy. However, it can be extrapolated that more AuNP are formed in the AuNP solution than in the fiber solution.

Notes

Setting the trend line of the Peak current vs. concentration graph to 0 gives an equation I = -9.0*10-9 [Au+3] and an R2 value of 0.9902. Using this equation to extrapolate the concentration of Au+3 and AuNP in AuNP solution and AuNP fibers gives the following:

Solution [Au+3] [AuNP]
AuNP solution 1.64*10-4 M 3.25*10-4 M
AuNP fibers 1.98*10-4 M 2.67*10-4 M