2D Mos2 shows three distinct absorption peaks which are related to A, B, C excitons and are almost fixed for different flakes of different sizes of small variations. According to theory, when the length and width of the flake increases abruptly, peak position should remain fixed, but there is a increase in strength. Can anyone tell, whether there is any possibility of shifting of the peaks?
Dear Dr. Durga Prasad Khatua,
I suggest you to have a look at the following, interesting paper:
- Energy Transfer from Quantum Dots to Graphene and MoS2: The Role of Absorption and Screening in Two-Dimensional Materials
Archana Raja, Andrés Montoya−Castillo, Johanna Zultak, Xiao-Xiao Zhang, Ziliang Ye, Cyrielle Roquelet, Daniel A. Chenet, Arend M. van der Zande, Pinshane Huang, Steffen Jockusch, James Hone, David R. Reichman, Louis E. Brus, and Tony F. Heinz
Nano Lett, 16, 4, 2328–2333 (2016)
Available at: https://pubs.acs.org/doi/10.1021/acs.nanolett.5b05012
Best regards. Pierluigi Traverso
Yes, in general. Absorption spectra carries important signatures regarding the dimensionality and size/thickness of nanomaterials. For MoS2, you can observe important changes in both UV-Vis-NIR absorption and Raman spectra.
Basically, you need a series of samples synthesized in a similar technique for such experiments. In case of MoS2, absorption properties significantly vary with synthesis technique as well.
The absorption peak of MoS2 varies due to a change in quantum confinement. A, B, C, D are characteristic peaks which are generally observed in exfoliated MoS2 system which falls in the visible region but can vary slightly depending upon the dimension of flake. But besides this, there are flakes of certain dimension which absorbs in IR and UV region too.
Please see this: Article Quantum confinement effects across two-dimensional planes in...
Thanks Dear Souvik Bhattacharjee for responding this question. Yes, you are right, the absorption spectra of MoS2 will change depending upon the synthesis technique, environment and also the no of layers present in the sample which I have encountered still now in different reported articles. But, What I want to know, if the spectra will change for a single layer MoS2(2D) but by varrying its length and width which I encounter in computational analysis. If you can help, please???
Dear Durga Prasad Khatua in low dimensional materials the lowest dimension controls nanoscopic properties principally. Hence, I think, for a small and a large monolayer MoS2 flake, absorption peaks should be at the same position. Only, the intensity may vary a bit depending on the length and width.
Dear Souvik Bhattacharjee, yes, you are right. That's what, we have concluded(peak position will remain same, but intensity will varry depending upon the length and width). Since, we have encountered the above mentioned problem from a theoretical calculation, now I am confused, why this happen? Is it a special property of the material or calculation error?
Thank you for your valuable inputs.
Thanks Dear Gagandeep Singh for your response. Yes, you are right, due to quantum confinement, A,B,C,D excitonic peaks positions will varry dependening upon the dimension of the flake mainly thickness. The article which you have referred is based on MoS2 quantum dots of sizes between 2 nm to 9 nm. But, I want to know whether a monolayer of MoS2 whose thickness in 0.65 nm but varrying length and breadth show peak shift in absorption spectra.
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