I am doing some simulations with the dyes dispersed in a PMMA and I want to test the device with different dye concentration (ppm). In order to do so, I need the molar absorptivity/molar extinction coefficient so that I can relate it to the transmittance and absorbance. I have the absorption and emission spectra of these Dyes, but I do not know their molar absorptivity/molar extinction coefficient, thus I can not compute the concentration (ppm) that I am using in the sample for the simulations. Does anyone know where can I found this data? I tried searching on the internet, but I did not find anything.
Dear Marcello,
The molar extinction coefficient can be derived from plotting the absorbance of samples as a function of the added dye concentration. So what you need to do is prepare a set of samples with varying dye concentration. Next measure their absorbance against a blank (sample without the dye) and plot the absorbance you found against the added concentration. This should give a straight line in which the slope is the absorption coefficient expressed formally as liter/mole*cm but if you use ppm it will be 1/ppm*sample thickness.
Two important pieces of advice:
1. Make sure all samples are the same thickness (and if not measure their thickness and correct for this) as the absorbance is path length dependent.
2. When performing a wave-length scan, make sure you start from highest wavelength and move to lower wavelength during the scan. These dyes are known to show fluorescence and when starting at the lowest wavelength you may excite them and the fluorescence resulting from that will create additional signal which is not absorbance.
Hope this helps, kind regards, Leo
Hi,
The molar attenuation coefficient is a measurement of how strongly a chemical species ... Different disciplines have different conventions as to whether absorbance is decadic (10-based) or Napierian (e-based).. is a measure of how well a chemical species absorbs a given wavelength of light. It allows you to make comparisons about the probability of electrons transition between levels for different compounds without taking into account differences in concentration or solution length during measurements..
Kindly refer this link: https://www.wikihow.com/Calculate-Molar-Absorptivity
Best Wishes..
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