Absorption coefficient α calculation from UV-Vis absorbance data in origin

[@elhammohammadi5644]

No one explain this theory like you. Great. Thank you

[@SAYPhysics]

Thanks for the appreciation dear. Please share it with others too as an acknowledgement.

[@todesschatten-]

Your videos are VERY helpful for beginners entry level to Absorbance theory applied into Origin. Thank you!

[@SAYPhysics]

Thanks for the appreciation dear 😊

[@indrashispowali]

Thank you for the easy explanation, Sir!

[@SAYPhysics]

You're welcome dear

[@jeanfrancesegbuhuzor7063]

Thanks for the video. How do one ascertain the thickness for for a solid state analysis.

[@SAYPhysics]

Thank you for watching the video, and I'm glad you found it helpful! In solid-state analysis, determining the thickness is crucial for accurate results. For the material's thickness, you can measure it directly if it's a standalone sample. If you're working with doped material, subtracting the thickness of the actual matrix from the doped material provides a reference point. This ensures that your analysis focuses on the properties of the doped material specifically.

[@javadrahmannezhad9908]

Thank you for this great explanation. Could you please provide any book or paper as a reference for this demonstration?

[@SAYPhysics]

Please check the video description for the references. Thanks

[@riariya5510]

Great explanation. But I have a question my sample is in solid form .then how to find absorption coefficient. Pls help.

[@youneselhandouz6588]

Thank you sir, i have a question. For thin films how do we calculate alpha? In this cas (thin films) we can put 1cm if no how do can estimate the thickness?

[@SAYPhysics]

Calculating the absorption coefficient (α) for thin films requires a slightly different approach compared to bulk materials. In thin films, the light travels through both the film and the underlying substrate, leading to a complex optical interaction. However, it is still possible to estimate α for thin films using appropriate methods. Here's how you can approach it: 1. Transmission measurement: Measure the transmission spectrum of the thin film on the substrate using UV-Vis spectroscopy. This will provide information about the amount of light transmitted through the film. 2. Substrate measurement: Measure the transmission spectrum of the bare substrate without the thin film. This will serve as a reference for the substrate's contribution to the overall absorption. 3. Calculation: To calculate α for the thin film, you need to account for the substrate's absorption and the film's contribution. The Beer-Lambert law can be applied using the following equation: α_film = (1/t_sub) * ln(T_substrate/T_film) where: α_film = absorption coefficient of the thin film t_sub = thickness of the substrate T_substrate = transmission of the bare substrate T_film = transmission of the thin film on the substrate In this equation, the term (1/t_sub) accounts for the substrate's thickness. By taking the logarithm of the transmission ratios, you can determine the absorption coefficient of the thin film. 4. Estimating thickness: If the thickness of the thin film is unknown, you can estimate it using additional methods such as ellipsometry, profilometry, or atomic force microscopy (AFM). These techniques provide precise measurements of the film's thickness. Remember that calculating α for thin films is more challenging due to the combined effect of the film and substrate. Additionally, the assumptions of the Beer-Lambert law might not fully apply in these cases. Therefore, it's important to consider the limitations and potential complexities involved in the analysis of thin films. Thanks

[@shah-xw6ik]

thank you Sir, how one can find the value of refractive index from UVvis absorption data

[@SAYPhysics]

In UV-Vis absorption data, you can't directly determine refractive index. Absorption coefficients relate to how much light is absorbed by a material, not its refractive index. However, you can indirectly estimate refractive index by analyzing other optical properties like reflectance or transmittance at different wavelengths alongside absorption data. Alternatively, you might need additional measurements or techniques specifically designed for refractive index determination. Thanks

[@shah-xw6ik]

@@SAYPhysics I appreciate your thoughtful response and your recommendation regarding this video. kzbin.info/www/bejne/aJ_MdqKirr9-aLs

[@SAYPhysics]

I don't agree with the content of the video mentioned. There are numerous other factors to consider, as I previously explained. When determining the refractive index of a material, ellipsometry is a more appropriate technique than UV-Vis spectroscopy. Thank you.

[@shah-xw6ik]

@@SAYPhysics thank you Sir.

[@SAYPhysics]

@shah-xw6ik You're welcome dear

[@muhammadimrankhan3181]

Assalam o alaikum sir...can I use it for nanoparticle to calculate the absorbtion coefficient?

[@SAYPhysics]

Yes dear. Thanks

[@AmitKumar-cd3nq]

nice video. Is needed to normalize the uv vis absorption data to get linear absorption?

[@SAYPhysics]

Thanks dear. There's no requirement to normalize the data for such calculations.

[@priyamathiviswanathan9341]

Sir, I have a doubt that I took UV visible characterization for powdered crystal Now for absorption coefficient what formula should I apply?

[@SAYPhysics]

Did you perform DRS of these powder sample or in reflection mode of the powder converted into pellet form? Thanks

[@priyamathiviswanathan9341]

@@SAYPhysics DRS performed powder sample sir?

[@SAYPhysics]

Although there's a way to convert it into a transmission data, however, not accurate, due to reference subtraction issues. You will have to retake your measurements in transmission mode again. If the sample isn't available you may do some approximation with the available data. Thanks

[@SAYPhysics]

Here's the step by step solution. To calculate the absorption coefficient, you can use the following equation: α = 2.303 × (A/t) × (1/d) where: α = absorption coefficient (in cm^-1) A = absorbance measured from DRS t = thickness of the sample (in cm) d = density of the sample (in g/cm^3) Here's how you can calculate the absorption coefficient alpha from your DRS data: Measure the thickness of your sample using a micrometer or a similar tool. Determine the density of your sample using a density meter or by referring to literature values. Convert the absorbance measured from DRS to an extinction coefficient (ε) using the Beer-Lambert law: A = ε × l × c where: A = absorbance measured from DRS l = path length of the sample (in cm) c = concentration of the sample (in mol/L) Note: If you don't know the concentration of your sample, assume a concentration of 1 mol/L. Calculate the absorption coefficient (α) using the equation mentioned above. α = 2.303 × (ε/t) × (1/d) where: ε = extinction coefficient (in cm^-1M^-1) t = thickness of the sample (in cm) d = density of the sample (in g/cm^3) Note: If your extinction coefficient is in units other than cm^-1M^-1, convert it to cm^-1M^-1. By following these steps, you can calculate the absorption coefficient alpha from your DRS data.

[@priyamathiviswanathan9341]

@@SAYPhysics Thank you so much sir 😇

[@mydogisnotyourdog]

if the units of absorption coefficient are cm-1 then how come there is no mention of length of thin film in your calculations

[@SAYPhysics]

Thank you for your question. The length of the solution is implicitly considered in the calculations through the assumption of a standard cuvette length of 1 cm. This assumption ensures that the correct units and dimensions are maintained when calculating the absorption coefficient in units of cm-1. I hope this clarifies the matter. If you have any further inquiries, please let me know.

[@TheDarkNight97]

I have a Q for ya, sir. Is it possible to calculate the absorption coefficient without thickness? See, my sample is Co3O4 nanoparticles and I have to calculate the optical conductivity from uv-visible data.

[@SAYPhysics]

While calculating the absorption coefficient without knowing the thickness of your Co3O4 nanoparticles can be challenging, you can still gain insights into their optical properties by analyzing the UV-Vis spectrum and considering theoretical models designed for nanoparticle systems. Thanks

[@TheDarkNight97]

@@SAYPhysics So, is there any equation for that?

[@SAYPhysics]

It is possible to calculate the optical conductivity of nanoparticles from UV-Vis absorbance data, it requires the determination of the frequency-dependent dielectric function through methods such as the Kramers-Kronig relation, and careful consideration of various nanoparticle-specific factors. Once you have the complex dielectric function, you can calculate the optical conductivity using the relation: σ(ω) = (ωε₂(ω)) / (4π), where σ(ω) is the optical conductivity at frequency ω, and ε₂(ω) is the imaginary part of the dielectric function. Thanks

[@TheDarkNight97]

@@SAYPhysics thank you, sir. Very helpful.

[@SAYPhysics]

@alimohandes5651 thanks dear 😊

[@anasjaved6647]

Sir electrodynamics Ki next vedio kab aye GI??

[@SAYPhysics]

After Ramadan, IA. Thanks