User:Melissa Novy/Notebook/CHEM-572/2013/02/20

Objectives

• Calculate the amount of AgNO₃ to add to LB media solutions for desired final [Ag⁺].
• Remove PLA films, made on 2013/02/19, from glass molds.
• Soak PLA films in pure H₂O to test for Ag⁺ leaching with a silver ion selective electrode.
• Run X-ray on 100Ag-LMT.
• Harvest DH5α-T1 cells for Ag⁺ cell growth inhibition studies.

DH5α-T1 Cell Harvesting

• Five cell starter cultures, made on 2013/02/19 were obtained and their absorbance at 600 nm was recorded.
• Please refer to Keyun Wang's entry for the absorbance data and the protocol to pellet the cells.

X-Ray Diffraction on 100Ag-LMT

• The protocol from 2013/02/05 was used.

• Peaks at values of 2θ were observed as follows: 19°, 21°, and 35°. These peaks correspond to d-spacing values of 4.491 nm, 4.277 nm, and 2.547 nm. When compared to the XRD spectrum of Laponite, there was a decrease in the d-spacing from 4.544 nm in Laponite to 4.491 nm in 100AgLMT. According to literature, this decrease in d-spacing indicates that Ag⁺ was successfully exchanged into the clay galleries, as the structure of the clay has changed. Note that the peak at 21° may be attributed to background noise.
• The peak at around 35° represents a d-spacing of 2.547, similar to the same peak in the Laponite XRD spectrum that displays a d-spacing of 2.550. The similarities between these peaks indicate that the peak at 35° is due to the structure of Laponite.

Calculations

• Two sample calculations are given as examples. The final [Ag⁺] in 50-mL solutions of LB media was calculated as follows:

  1 μM Ag+ in 50 mL of LB media
  (0.0105 M Ag+) × V1 = (1×10-6 M) × (50 mL)
  V1 = 0.00476 mL of 0.0105 M AgNO3

  10 μM Ag+ in 50 mL of LB media
  (0.1 M Ag+) × V1 = (10×10-6 M) × (50 mL)
  V1 = 0.005 mL of 0.1 M AgNO3

• AgNO₃ solutions made on 2013/02/05 and 2013/02/13 will be added to the LB media solutions in the following amounts:

• Note that for each volume of AgNO₃ added to the LB media, the same volume of LB media will first be removed from the flask to maintain the final concentration of Ag⁺.

ISE Study of PLA2002D + 5 wt% 100Ag-LMT

• Calculations
  • To determine maximum [Ag⁺] possible, assume that all Ag⁺ leaches out of the film.
  • The solution contained 50 mL pure H₂O and 1 mL ionic strength adjuster. The recommended ratio of solution to ionic strength adjuster is 50 mL to 1 mL. Then, 0.50 g of film was added to the solution.

  (4.47 × 10-8 mol Ag+) ÷ 0.051 L = 8.76 × 10-7 M or 0.876 μM

• Protocol
  1. Pour 50 mL pure H₂O into a clean, dry 250-mL Erlenmeyer flask and add 1 mL of 5 M KNO₃.
  2. Measure the conductivity of the solution with the ISE.
  3. Place a single 0.5 g piece of film into the flask, swirl, and measure the conductivity.
  4. Wait 30 min, then measure the conductivity again.
  5. Repeat the above step 5 more times.