I am wondering in min 15:30, if I am conducting the measurement on thin films, then instead of 2.303 x A/1cm, I should divide Absorbance by my actual thin film thickness (.0002 cm in my case), right? So my absorption coefficient would look like: a= 2.303 x A / .0002
In my undergraduate thesis, in the UV-Vis experiment, we were give wavelength (nm) and Transmittance (in percentage) (in your case, it was absorbance). Then I got the absorbance by using Beer's law, A=2-Log(10)[%Transmitance]. Then I continued with the other steps. I hop this is right
If you are just curious about the Energy itself, you can use every value instead of 2.303, because it does not matter. The value of ν, where (αhν)² is zero is only dependent on the spectrum itself.
For the thin film, we need to measure the thickness of film where the L may not be 1. The thickness could be measured by ellipsometry or some optical instrument~
Thank you so much for the video. but I have a question. 'L' is for the thickness of the cuvvette. what if my sample is a film and there's nothing between my sample and light. (the incident light directly hit my sample because i didint use cuvvette or sample holder)
Thank you so much, please can you explain how to know when a = 2 or 1/2 how to know the nature of transmission. indirect transmission or indirect transmission. Thank you
very informative . thanks alot for sharing such a beautiful video . how can we find band gap of an unknown material . i mean we have no idea either it have direct/ indirect bandgap. secondly can you recommend any book to study band gap analysis.????
Thank you, Sikander. I'm going to upload soon a video on "How to know the transition nature in the bandgap of any unknown material" within a few days. Secondly, If you are beginning to the optical properties of material, then you should study "optical properties of solid by Mark fox".
thank you for calculate the energy gap, I need videos that show how calculate the Refractive index, Extinction factor, real and imaginary of Dielectric constant and Urbach tail energy, with my appreciate.
thank you so much for the video....Really useful.....I have a doubt.. Could you write the formulas that you have wrote in the origin. becos, It was not clearly visible to me.
Thanks for your helpful video. I have some question. I think you assumed that there is no reflection at the surface of sample because reflection at surface of solution is negligible. But in case of thin film, there must be reflection at the surface. So Io must be changed into Io-Ir (Ir is intensity of reflected light), because UV-vis only detect the intensity of transmitted light to calculate absorbance. In this case, should I measure the reflectance in reflection mode and recalculate the absorbance to obtain alpha?
I have a question, if I use UV-VIS measurement for solid samples without cuvette, do I need to multiply 2.303 factor for values of the Oy axis? Or I just need (Absorpbance x energy)^m ??? Many thanks!
hello, thank you for the video..it really helps me to calculate the band gap of my nanoparticle. mai I ask the pdf /word version of this file? thank youu
Thank you so much for this wonderful video. But I have a question. If I understood it correctly we can use this formula only for solutions. Because you mention about quartz cuvette and "cm-1" is depend on length of the cuvette. If I will use thin film, how can i use alpha value? In this case, is it related to film thickness?
This equation is used to convert wavelength to energy. In Wavelength Vs Transmittance data, you have wavelength, which means can use this equation to convert wavelength to energy.
Hello Harish! The range of value on Y-axis depends upon the absorption coefficient. Which means a material with a higher absorption coefficient will have a higher value on Y-axis and vice versa. Therefore don't be confused.
Hi, My sample is a thin film of thickness 1.5nm deposited on a quartz substrate of 0.025cm, which thickness should I put according to your video it should be the path length of the sample i.e. 1.5nm, am I correct? Also, the unit should be cm?
Hello, If you used Kubelka Munk to convert reflectance to absorbance, you cannot use Lambert Beer's law to convert Abs to Coefficient. How would you make Tauc plot then?
@@ajendravats946 The path length.L in video would not be 1, so you'll need to get the thin film thickness. The thicker film, the absorbance, A, would be larger, so, the UV and thickness data should from the same sample you made, and use the formula a=2.303A/L may get the right coefficient.
@@nanoworld6122 ok got it. I just noticed that the value alpha=2.303 *A/1cm is used in calculation if we use liquid right?If i use solid (rectangle shape) , i need to use its thickness right?..Another question is , the value of n is only either 2 and 1/2?
@@mariamramlan9704! Yes, you are right, if we use solid (rectangle shape) , then we will need to use its thickness. in Tauc equation (ahv)^n the exponent "n" may have any of these value. n= 2 direct allowed transition n=0.5 indirect allowed transition n=2/3 direct forbidden transition n=1/3 indirect forbidden transition
@@nanoworld6122 so if my sample's thickness is 3.7 mm, then i substitute it, (2.303×(A/0.37cm)×hv)^m =2.303×(2.703A)×hv)^m Does my understanding correct?
you must plot Tauc plot for both type of transition i.e Direct and Indirect, then check what type of transition give you best fit of the curve (tangent). If you are confused about UV data then send it to me, i'll check it and let you know. Thank you. fascinatingnanoworld@gmail.com
@@nanoworld6122 i have plotted it for both n=2 and n=1/2 both give me same value 3.5. and i am also confused about n value n=1/2 for direct transition but every paper i studied have use (ahv)^2 instead of (ahv)^1/2 for ZnS although ZnS is direct transition
@@aishaaziz9248 I think you are doing something wrong. Because, if someone calculate both type of bandgap (i.e direct and indirect) for the same material, direct bandgap value will be greater than indirect bandgap value.
I would like to thank you for taking your invaluable time out of your schedule to record this priceless video. I really appreciate it.
I would like to thank you for explained this clearly.
You are a genius and helped me so much!!!!!
Thank you very much for this video,
You help all researchers of world to move forward, Your video is excellent :)
Good continuation
Thank you so much, this is really helping my theses. U explained it so well
very nice ...get more information from your video thanks ..may you live long
Thanks
I am wondering in min 15:30, if I am conducting the measurement on thin films, then instead of 2.303 x A/1cm, I should divide Absorbance by my actual thin film thickness (.0002 cm in my case), right? So my absorption coefficient would look like: a= 2.303 x A / .0002
Thanks for the video btw, really helpful.
Yes, you understood it correctly.
@@nanoworld6122 Thanks for the confirmation!
thank you so much, helpful for my work in the laboratory.
Thanks...
very professional presentation and hopefully, to see more in the future
Thanks a lot for the timely sharing
Can I use the constant=2,303 for UV-vis in thin film mode?
Very good description
In my undergraduate thesis, in the UV-Vis experiment, we were give wavelength (nm) and Transmittance (in percentage) (in your case, it was absorbance).
Then I got the absorbance by using Beer's law, A=2-Log(10)[%Transmitance]. Then I continued with the other steps.
I hop this is right
Best explanation. Thank you so much!!!
Kudos!
Excellent video
If you are just curious about the Energy itself, you can use every value instead of 2.303, because it does not matter. The value of ν, where (αhν)² is zero is only dependent on the spectrum itself.
very good explanation ..hats off
Glad you liked it
What about concentration of Beer Lambert's Law, as A=ecl, where e = molar absorption coefficient, c= concentration,mol lit-1 and l=path length
really good video sir please make a video of cut off wave length and band tail parameter graphs also those are very useful
for more
Very nice video ,
Thank you so much, this is really helpful.
Thanks
Thank you so much, this is really helpful.
really help me to learn.. thanks to youu !
I wish you had a video about Urbach energy 😅
Incase of Solid samples, how to take L value? Still we have to take path length (1 cm) ?
excellent and precise video. Thank you
Your video is excellent.
Thanks
Hi, does thickness of material matter while calculating the absorption coefficient?
For the thin film, we need to measure the thickness of film where the L may not be 1.
The thickness could be measured by ellipsometry or some optical instrument~
Excellent video! Any book or paper where I can find this explanation? to reference it in my thesis. Thanks
had you get it??
i alsi need a book for explanation
Well explanation Anna.. we can use this for both disperse sample and direct powders??
Thank you! It's so useful material. Where can I download a word file?
Thank you so much for the video. but I have a question. 'L' is for the thickness of the cuvvette. what if my sample is a film and there's nothing between my sample and light. (the incident light directly hit my sample because i didint use cuvvette or sample holder)
Have you got an answer to this question yet?
Thank you so much, please can you explain how to know when a = 2 or 1/2
how to know the nature of transmission. indirect transmission or indirect transmission.
Thank you
you plot both and you check which one gives linear relationship
You are great. Thank you very much
You are welcome
very informative . thanks alot for sharing such a beautiful video . how can we find band gap of an unknown material . i mean we have no idea either it have direct/ indirect bandgap. secondly can you recommend any book to study band gap analysis.????
Thank you, Sikander.
I'm going to upload soon a video on "How to know the transition nature in the bandgap of any unknown material" within a few days.
Secondly, If you are beginning to the optical properties of material, then you should study "optical properties of solid by Mark fox".
thank you for calculate the energy gap, I need videos that show how calculate the Refractive index, Extinction factor, real and imaginary of Dielectric constant and Urbach tail energy, with my appreciate.
Very valuable video.
Glad it was helpful!
correction plz
n=2 for indirct band gap while n=1/2 for direct band gap
Your statement will be valid, if the exponent "n" was on the other side of equation. Anyway, Thanks for the comment.
So nice video. thanks a lot.......
Thank you So Much for detail explanation... God bless u all ...
Thank you.
thank you so much for the video....Really useful.....I have a doubt.. Could you write the formulas that you have wrote in the origin. becos, It was not clearly visible to me.
Thanks for your helpful video. I have some question.
I think you assumed that there is no reflection at the surface of sample because reflection at surface of solution is negligible. But in case of thin film, there must be reflection at the surface. So Io must be changed into Io-Ir (Ir is intensity of reflected light), because UV-vis only detect the intensity of transmitted light to calculate absorbance. In this case, should I measure the reflectance in reflection mode and recalculate the absorbance to obtain alpha?
Thank you so much 💓💓
Very nice presentation 👍
Alpha is linear absorption coefficient?
Pathlength shouldn’t be the sample thickness??? What if our sample has a thickness???
Great👍🏼👍🏼👍🏼Thanks a lot.
Nice video. But what if we dont know if our material is direct or indirect band gap? which value of n should we use?
Please watch this video.
ruclips.net/video/dc2EHBMlyBA/видео.html
there is any reference for the citation?
How can we get to know that whether it is direct or indirect
thank you so much, it good work... regards
Thanks...
I have a question, if I use UV-VIS measurement for solid samples without cuvette, do I need to multiply 2.303 factor for values of the Oy axis? Or I just need (Absorpbance x energy)^m ???
Many thanks!
No need to multiply 2.303. It is just a constant and did not effect the energy bandgap value.
@@nanoworld6122 Thank you! Your video is really helpful.
What about concentration in Lambert beers law?
hello, thank you for the video..it really helps me to calculate the band gap of my nanoparticle. mai I ask the pdf /word version of this file? thank youu
Thank you so much for this wonderful video. But I have a question. If I understood it correctly we can use this formula only for solutions. Because you mention about quartz cuvette and "cm-1" is depend on length of the cuvette.
If I will use thin film, how can i use alpha value? In this case, is it related to film thickness?
Have you got an answer to this question yet?
thanks a lot, very love this video.
Glad you enjoyed it!
please share the word or pdf file u have made ...
Can equation eg= 1240/waveleth be used for transmittance spectra data obtained from uv vis?
This equation is used to convert wavelength to energy. In Wavelength Vs Transmittance data, you have wavelength, which means can use this equation to convert wavelength to energy.
I have a Question, How we look for a correct value rang in Y axis?. In many papers took different rang B/w 0 to 0.1 or 0 to 1 or 0 to 80etc.
Hello Harish! The range of value on Y-axis depends upon the absorption coefficient. Which means a material with a higher absorption coefficient will have a higher value on Y-axis and vice versa. Therefore don't be confused.
@@nanoworld6122 thank you
Hi, My sample is a thin film of thickness 1.5nm deposited on a quartz substrate of 0.025cm, which thickness should I put according to your video it should be the path length of the sample i.e. 1.5nm, am I correct? Also, the unit should be cm?
Have you got an answer to this question yet?
Hello, If you used Kubelka Munk to convert reflectance to absorbance, you cannot use Lambert Beer's law to convert Abs to Coefficient. How would you make Tauc plot then?
Hello Simon,
You will find your answer in this video,
ruclips.net/video/Ry9Jdjeh2-Q/видео.html
First of all Thank you very much for the valuable video. I wanted to ask can we draw Tauc plot for film absorption spectra?
Yes we can
@@nanoworld6122 Ok. But I wanted to ask what is the effect of thickness of the thin film.
@@ajendravats946 The path length.L in video would not be 1, so you'll need to get the thin film thickness.
The thicker film, the absorbance, A, would be larger, so, the UV and thickness data should from the same sample you made, and use the formula
a=2.303A/L may get the right coefficient.
for liquid same ok but for powder sample the cuvettes setup is not present so is their calculation will be change
could you please share the calculation?
What is the concentration of the solvent by "alpha"?
sorry, i did't got your question. can you little bit more explain question.
what about solid state uv-vis
But what if your sample is solid? What should be “l”??
@@nanoworld6122 It's not film, it's powder. What the value of alpha in case nanoparticles?
@@Hadba_h I would like to know, your data is wavelength vs absorption or Wavelength Vs Reflectance?
@@nanoworld6122 wavelength vs absorption
This method is only useful for nanomateriales, I mean if I want to calculate the band gag for example a solution of porphyrin. Could I ?
yes
Very interesting. Some bibliographical reference that you can recommend me
@@nanoworld6122 can i get this document?
ok subscribed!
Thank you soo much for this helpful video. can you send me this video as a word file, please?
Sure, send me your email address.
thank you so much!
Very useful video for beginners.Can you give the word file??
email me
is the same method used if i use transmittance (%T)? does the equation become ---> (lambda*hv)^n = (2.303*%T*hv)^n ?
No, first you need to convert Transmittance (%T) to Absorbance (A) and then apply this formula.
@@nanoworld6122 ok got it. I just noticed that the value alpha=2.303 *A/1cm is used in calculation if we use liquid right?If i use solid (rectangle shape) , i need to use its thickness right?..Another question is , the value of n is only either 2 and 1/2?
@@mariamramlan9704! Yes, you are right, if we use solid (rectangle shape) , then we will need to use its thickness.
in Tauc equation (ahv)^n
the exponent "n" may have any of these value.
n= 2 direct allowed
transition
n=0.5 indirect allowed
transition
n=2/3 direct forbidden transition
n=1/3 indirect forbidden transition
@@nanoworld6122 so if my sample's thickness is 3.7 mm,
then i substitute it,
(2.303×(A/0.37cm)×hv)^m
=2.303×(2.703A)×hv)^m
Does my understanding correct?
Sorry for late reply. Your comment was automatically moved to spam. i Just seen it today.
Yes, your understanding is correct.
how would we know if our material is in direct transition or indirect
you must plot Tauc plot for both type of transition i.e Direct and Indirect, then check what type of transition give you best fit of the curve (tangent).
If you are confused about UV data then send it to me, i'll check it and let you know. Thank you.
fascinatingnanoworld@gmail.com
@@nanoworld6122 i have plotted it for both n=2 and n=1/2 both give me same value 3.5. and i am also confused about n value n=1/2 for direct transition but every paper i studied have use (ahv)^2 instead of (ahv)^1/2 for ZnS although ZnS is direct transition
@@aishaaziz9248 I think you are doing something wrong. Because, if someone calculate both type of bandgap (i.e direct and indirect) for the same material, direct bandgap value will be greater than indirect bandgap value.
Thanks a lot sir
Could you please share the word file
email me
from graph where i take slope
JazakAllah..
thanku sir....can i get this document (word file which make in video)? please.☺
Yes, Sure.
Your email address?
@@nanoworld6122 i also need this fil
Some biblical reference to quote it in my thesis, please.
Thank you very much
No worries
Great!!! Congratulations for the video, can you send me this video as a word file, please? I'd like to use with my coleagues. Thank u
Sure, just send me your email address.
Thanks a lot for timely sharing
@@nanoworld6122 can you give me as a word file to?
How do we know the value of n??I mean to say can we find if we have direct band gap or indirect band from uv spectroscopy?
I suppose to make a video on it. Because, you will not got it through comment.
@@nanoworld6122 okk.. We will be waiting for it.. Thanku so much😇
dude, n = 2 for indirect and n = 0.5 for direct
This is when the exponent is on the other side of the equation.
Thankyou sir
Good
Plz check your email
I m very confused about my UV data
thanks~讓我受益良多
Welcome