User:Tamra L. Fisher/Notebook/Experimental Biological Chem/2011/08/31

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Objective

To determine how pH effects the biomineralization of gold nanoparticles using the biomineralization procedure by Bakshi, et al (doi:10.1021/jp110296y).

Description

  1. Mix 0.0015-0.015 mM BSA and 0.25-1.0 mM of HAuCl4 at room temperature.
    • This mixture will be at a certain pH and will be made to final volume of 10mL. (Each group in the class will be assigned a different pH)
  2. Heat for six hours at 80°C.
    • Take a spectrum of the mixture (200nm-900nm) every half hour.
  3. The mixture if then cooled to room temperature and stored at room temperature overnight.
  4. The samples are washed with pure water and then centrifuged at 10000-14000 rpm for 5 min to collect the gold nanoparticles; this is repeated a second time.

Data

A spectrum of just the buffer was taken, and the absorbance of that spectrum was subtracted from the spectrums of the mixtures taken approximately every half hour:

I'd like to see this graph zoomed in to center around what's going on at 550. What I want to know is the following: Is the baseline just increasing, or is there actually a new peak growing in at 550? Matt Hartings 08:39, 6 September 2011 (EDT)

This graph shows that the absorbance at 550nm was increasing, so gold nanoparticles were being formed in the reaction mixture as the gold was reduced:

A zoomed in version of the spectrum shows that a peak was beginning to form at 550nm instead of just the baseline increasing:

Notes

  • Actual HAuCl4 measured out was 0.001g. (MW=339.79 g/mol)
  • Actual Concentration= 0.2943mM
  • Actual BSA measured out was 0.001g. (MW=66776 g/mol)
  • Actual Concentration=.001498mM
  • 50mM Acetate Buffer at pH 3.6 was used
  • Spectrum of just the Acetate Buffer was taken and a spectrum of the mixture was taken from 200-800nm in a 1mL quartz cuvette.
  • Oven was heated to 78°C at 0min, sample was placed in for a half hour.
  • Sample was removed and a spectrum from 200nm-800nm is taken in the 1mL quartz cuvette.
  • Oven was heated to 69°C when the sample was put back in; sample was then left in the oven for another 30 min.
  • Sample was removed and a spectrum from 200nm-800nm is taken in the 1mL quartz cuvette.
  • Oven was heated to 78°C when the sample was put back in; sample was then left in the oven for another 30 min.
  • Sample was removed and a spectrum from 200nm-800nm is taken in the 1mL quartz cuvette.
  • Oven was heated to 70°C when the sample was put back in; sample was then left in the oven for 37 min.
  • Sample was removed and a spectrum from 200nm-800nm is taken in the 1mL quartz cuvette.
  • Oven was heated to 74°C when the sample was put back in; sample was then left in the oven for another 30 min.
  • Sample was removed and a spectrum from 200nm-800nm is taken in the 1mL quartz cuvette.
  • Oven was heated to 70°C when the sample was put back in; sample was then left in the oven for another 30 min.

The color of the mixture remained clear the whole time, but the absorbance of the mixture at 550nm did increase over the 187 minutes the mixture was incubated at approximately 80°C.

Update 9/7/11: When the mixture was viewed a week later (after being wrapped in aluminum foil and stored at room temperature all week) the color of it was light purple.



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