Best way to calculate UV-Vis absorption onset?

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SUMMARY

The best method to calculate the UV-Vis absorption onset for determining the optical band gap involves plotting wavelength against (wavelength * Absorbance)^2. Fitting a linear regression through the linear portion of this graph allows for the intercept to be identified as the onset. Additionally, calculating the first derivative of the absorbance spectrum and locating the zero point after the last saddle point can also effectively determine the onset. Tauc plots are commonly utilized in this analysis.

PREREQUISITES
  • Understanding of UV-Vis spectroscopy
  • Familiarity with Tauc plots for optical band gap calculations
  • Knowledge of linear regression analysis
  • Ability to compute derivatives of functions
NEXT STEPS
  • Research how to construct and interpret Tauc plots for optical band gap determination
  • Learn about linear regression techniques in data analysis
  • Explore methods for calculating derivatives in spectral data
  • Investigate software tools for UV-Vis spectral analysis, such as OriginLab or MATLAB
USEFUL FOR

Researchers, chemists, and materials scientists involved in optical properties analysis, particularly those working with UV-Vis spectroscopy and optical band gap calculations.

Dan Zar
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Homework Statement


Hello,
I have a bunch of UV-Vis spectra to analyze and I am having a hard time choosing what the "onset" of each spectrum is, which I will use to calculate the optical band gap of each spectrum.

Homework Equations

The Attempt at a Solution


I read somewhere that plotting wavelength vs. (wavelength*Absorbance)^2 and then fitting through the linear portion of the graph, where the intercept corresponds to the onset.
By calculating the first derivative and checking the zero point after the last saddle point could also yield the onset? thanks
 
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Dan Zar said:

Homework Statement


Hello,
I have a bunch of UV-Vis spectra to analyze and I am having a hard time choosing what the "onset" of each spectrum is, which I will use to calculate the optical band gap of each spectrum.

Homework Equations

The Attempt at a Solution


I read somewhere that plotting wavelength vs. (wavelength*Absorbance)^2 and then fitting through the linear portion of the graph, where the intercept corresponds to the onset.
By calculating the first derivative and checking the zero point after the last saddle point could also yield the onset? thanks
Tauc plots are typically used.
 

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