User:M Jaffe/Notebook/Au Nanofibers with Rhodamine/2016/03/23

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Objective

  • Synthesize new AuNP fibers, this time using HCl to increase acidity of the fibers so that they are more likely to form fibers than nanoparticles
  • Make a standard curve for concentration of Rhodamine B in solution as a function of UV-Vis absorbance
  • Measure UV-Vis absorbance of samples that had been synthesized on March 16 and then incubated in Rhodamine B overnight
  • Get HPLC to work

Observations

  • Fiber synthesis was unsuccessful, so another batch of fiber synthesis samples was created by Maxi and Nicole. See Nicole's notebook for information on preparation of new fibers.

Analysis of 24 hour Incubation Samples

  • Fiber samples that were incubated with Rhodamine B for 24 hours were analyzed using UV-Vis today.
  • UV-Vis was performed from 190 nm to 800 nm using a 700 μL quartz cuvette.
  • Samples were carefully pipetted out of the glass test tubes and into the cuvette. Transference was done such that only supernatant was transferred and fibers were all left behind.
  • Data was analyzed by subtracting a water blank spectrum from all spectra and subtracting the average value of 700nm-800nm from each respective spectrum. Data are presented as percent change in concentration

Data

Figure 1: The image above shows the raw spectra for Rhodamine B absorption by AuNP fibers over 24 hours.

Figure 2: The image above shows the percent change in concentration of Rhodamine B in AuNP fiber solutions that were incubated for 24 hours.

Protocol

Making New AuNP Fibers

The fibers that were synthesized yesterday all formed AuNP. Today, we will add HCl to our samples to increase the acidity. We've found that increasing acidity generally tends to increase fiber formation.

The ingredients we used were as follows:

We added the following to each sample:

We did not label the samples because they were all the same. We will label the samples once we determine whether the synthesis worked.

We then put the samples in the oven at 80 degrees Celsius for 4 hours (cycle P1).

UV-Vis Absorbance: Standard Curve

We had been finding that measuring the absorbance of Rhodamine B dissolved in DI water was not yielding a linear calibration curve. After multiple trials, we found that measuring the absorbance of Rhodamine B dissolved in a solution of the ingredients used for the AuNP fiber sample gave a much more accurate calibration curve.

We did the following to make our calibration curve:

  1. We used 3 AuNP fiber samples from last Wednesday that had formed fibers.
  1. We added varying concentrations of Rhodamine B to each of the three samples to make the final concentration in each 2µM, 5µM, and 10µM. We did this by gently pipetting the rhodamine into the sample and then gently rotating the test tubes until the Rhodamine was evenly dispersed in solution.
  1. We pipetted 1mL of the solution into a 1.5mL Eppindorff tube.
  1. For the 2 and 5µM samples, we measured the absorbance of 700µL of this 1mL aliquot using a small-volume cuvette. For the 10µM sample, we found that the absorbance was too high to be recorded by the spectrophotometer. Thus, we made a 2:3 dilution of the 10µM sample in AuNP fiber solution and measured the absorbance of that.
  1. We also measured the absorbance of a DI water blank.
  1. We then created a calibration curve.

We washed the cuvette out with DI water and then methanol between each run.

UV-Vis Absorbance of Samples Synthesized on 20160316 and Incubated in Rhodamine for 24 Hours

We measured the absorbance of the samples that had been synthesized on March 16 and then incubated in 24 hours in Rhodamine B (from March 22 to March 23):

  1. We pipetted 1mL of the supernatant from each sample into separate 1.5mL eppindorff tubes
  1. We measured the UV-Vis absorbance of 700µL of the 1mL aliquots
  1. We plotted the results
  1. We also used the standard curve to determine the concentration of Rhodamine in solution.

We washed the cuvette out with DI water and then methanol between each run.

HPLC

Dr. Fox got the HPLC to work. We will use HPLC to measure acetylsalicylic acid and salicylic acid in solution.



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