Mrs/Miss/Mr Astuti,

Along with above stated comments about the material type (incl. dimensions, is it bulk, layer, nano-composite material?!), you have not specified as well as temperature (T) range, and the method too. So, I think that you have reflected in mind typical PL spectra, where energy position is really related to the band-gap energy (Eg). However the profile of those spectra is broad and thus a precise determination of band-gap energy inaccurate, especially at low Ts. In this context you can use PL excitation spectroscopy, where the resonance is observed when excitation energy coincides with so-called inter-band critical point energy in the JDoS. It is given by Ec in Eq.(1) (attachment), but this is band-gap. The relationship Ec=f(T) is given by two-oscillator model (Eq. 2); the model of Bose-Einstein (Eq. (3)); or Varshni equation (Eg. (4)). Its application assumes that you should conduct PLS at various temperature range in order to determine Ec (or Eg). You can use PLS data to obtain the corresponding absorption spectra using Eq. (5). It is applicable if you have both thin and thick layer material. Once when you have calculated absorption spectrum from corresponding PLS one, than you can obtain Eg by Tauc's relationship (Eq. (6) n = 1/2 direct band-dap semiconductor). If your material has gradient Eg, for example, that you can use Eq. (7) and PLS measurements at graded band-gap thickness (d), where using lastly mentioned dimensional characteristics of your material it becomes applicable Eq.(6), too. And s.o....

its easy...its Intensity (a.u) Vs energy already....may be wavelength. You can find the peak position and that's it...

Look for the first non-zero value, coming up from 0 eV, J or Hz (or down from your maximum wavelength). The energy/frequency/wavelength at which you first have a non-zero value is your band gap. You can convert between all of these units easily - there are plenty of websites with calculators if you can't be bothered figuring out the maths from the units. http://halas.rice.edu/conversions is one.

Hi All, thank you for the answer. I attached one PL spectrum of my sample i.e. nanodiamond functionalised with alkyl. nanodiamond well known has 5.5.-6 eV bandgap. however, after functionalisation the band gap may change. Could you please help me to determine the band gap of this sample in attached PL data below?

@Pankaj and @Aurangzeb which peak position we should take? (suppose in UV range I have 2 peaks; 380 & 366 nm)

The band gap is the peak on the left in ur case.

Mr. Aurangzeb Khan, how did you select the left peak ? then what is the use of the second peak.

Band Gap Energy (E)= (h*c)/λ

1eV = 1.6 x 10-19 Joules

Mrs/Miss/Mr Astuti,

Along with above stated comments about the material type (incl. dimensions, is it bulk, layer, nano-composite material?!), you have not specified as well as temperature (T) range, and the method too. So, I think that you have reflected in mind typical PL spectra, where energy position is really related to the band-gap energy (Eg). However the profile of those spectra is broad and thus a precise determination of band-gap energy inaccurate, especially at low Ts. In this context you can use PL excitation spectroscopy, where the resonance is observed when excitation energy coincides with so-called inter-band critical point energy in the JDoS. It is given by Ec in Eq.(1) (attachment), but this is band-gap. The relationship Ec=f(T) is given by two-oscillator model (Eq. 2); the model of Bose-Einstein (Eq. (3)); or Varshni equation (Eg. (4)). Its application assumes that you should conduct PLS at various temperature range in order to determine Ec (or Eg). You can use PLS data to obtain the corresponding absorption spectra using Eq. (5). It is applicable if you have both thin and thick layer material. Once when you have calculated absorption spectrum from corresponding PLS one, than you can obtain Eg by Tauc's relationship (Eq. (6) n = 1/2 direct band-dap semiconductor). If your material has gradient Eg, for example, that you can use Eq. (7) and PLS measurements at graded band-gap thickness (d), where using lastly mentioned dimensional characteristics of your material it becomes applicable Eq.(6), too. And s.o....

 Please try to normalize your data first, then flow the Bojidarka B. Ivanova way