User:Elizabeth Schott/Notebook/Nanoparticles/2015/05/27
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May 27 2015: Determining Size and Concentration of Au Nanoparticles from UV-Vis SpectraProcedure 1) Spectrometer was set up to laptop, where a blank cuvette filled with water was used to calibrate the system. 2) The cuvette was filled with 1 mL of solution from the sample being tested and 1 mL of water. This was done because the absorbancy level of an undiluted solution exceeded one, so this measure was done in accordance to beers law concentrations. This procedure was followed for each of the 20 samples, which in turn created 20 diluted samples, which were marked and sealed separately. 3) Raw data was recorded into excel for each of the 20 samples, where size and concentrations of the gold nanoparticles were calculated (see results). 4) The average absorbancy of each raw sample was then base lined using the Gaussian equation on excel, and recalculated to determine size and concentration of the gold nanoparticles (see results)
The first table contains original calculations.Average size of nanoparticle was approximately 12.75 nm with a standard deviation of 3.5075 nm. The average concentration (nm/M^-1 cm^–1) was approximately 2.46E-08 with a standard deviation of 6.32E-08. The second table contains calculations corrected by baseline data. Recalculated average size of nanoparticle was 13.65 nm with a standard deviation of 3.43779 nm. The recalculated average concentration (nm/M^-1 cm^–1) was approximately 1.22E-08 with a standard deviation of 8.08E-09. The last column in table represents the concentration of the undiluted sample. This is due to the sample being diluted in half with water in accordance to beers law concentrations. Discussion It is important to note the differences between the results of the raw data in comparison to those of the baselined data. It is interesting that the average size and standard deviation from the raw and baselined data were strikingly similar. The average concentration from the raw data only slightly differed from that of the baselined data, however the standard deviations for concentration were larger in the baselined data than in that of the raw data. The
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