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Chemistry LibreTexts

6. Visible Spectroscopy

  • Page ID
    247093
  • (Note - The following procedure was developed using a Varian CARY 50 Bio Spectrophotometer).

    1. Use a UV-VIS spectrophotometer to measure the absorbance spectrum between 300 and 700 nm.
      1. In order to collect a UV-VIS spectrum, you will need a blank. What can be readily used to serve as your blank? (Check with instructor!)
      2. Double click on the Cary WinUV shortcut key.
      3. Double click on the "Scan" shortcut key

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      4. Click on "Setup" and under X Mode change the start to 650 nm and the stop to 400 nm and then click "OK".

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      5. Insert your blank, and then click "Zero".

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      6. Click "OK" on the popup screen.
      7. Fill the cuvette with your nanoparticle solution and place it in the spectrophotometer.
      8. Click "Start" to collect the scan

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      9. Navigate to an appropriate file folder, assign a filename and click "Save". Note that this saved file will contain all of the scans you make until you close the program or start a new file.  You will next have the opportunity to assign a Sample ID.  Once again, choose a descriptive name.  Be sure to record both the filename and the Sample ID in your lab notebook.
      10. Look at the absorbance spectrum to make sure that the maximum absorbance does not exceed 1. If the absorbance does exceed 1, think of ways you could fix this.
      11. Once a suitable spectrum is collected, right click on the background of the graph and select "peak labels".
      12. Select the box “X label”.

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      13. Print the graph and include it in your lab notebook.
      14. We will now export the spectrum so that we can share the raw data with others and plot it together with the spectra from other groups. To do this, go to “File” and select “Save Data As”.
      15. From the “Files of Type” pull down menu, select “Spreadsheet Ascii(*.CSV)”. CSV stands for comma separated value, which simply means that the data will be stored as a text file, with columns of data separated by commas.  Save this file to one of the provided flash drive with a name that describes your synthesis parameters.

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      16. Dispose of the sample in the appropriate waste container.
      17. Upload your spectrum file to a shared file folder.
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