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Updated: Jan 24, 2026
Compact Quantum Dots for Single-molecule Imaging
Published on: October 9, 2012
Tuning of nonlinear absorption in highly luminescent CdSe based quantum dots with core-shell and core/multi-shell
Sneha Bhagyaraj1, Sreekanth Perumbilavil2, R Udayabashkar3
1Department of Applied Chemistry, University of Johannesburg, P.O. Box 17011, Doornfontein, 2028 Johannesburg, South Africa. oluwafemi.oluwatobi@gmail.com and Centre for Nanomaterials Science Research, University of Johannesburg, Johannesburg, South Africa and International and Interuniversity Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala - 686560, India. nkkalarikkal@mgu.ac.in and Center for Advanced Materials, Qatar University, P.O. Box 2713, Doha, Qatar.
Abstract:
We present our effort on an efficient way of tuning the nonlinear absorption mechanisms in ultra-small CdSe based quantum dots by implementing core-shell and core/multi-shell architectures. Depending on the size, architecture and composition of the QDs, these materials exhibited resonant and near-resonant nonlinear optical absorption properties such as saturable (SA) and reverse saturable (RSA) absorption for 5 ns pulses of 532 nm. These QDs exhibited a non-monotonic dependence of the effective two-photon absorption coefficient (β) under nanosecond excitation with a maximum value for a thinner shell. We obtained a nonlinear absorption enhancement of an order of magnitude by adopting the core-shell architecture compared to their individual counterparts. Interestingly, CdSe QDs exhibit SA and/or RSA depending on their size and show a switching over from SA to RSA as the input intensity increases. We explained the enhanced nonlinear absorption in core-shell QDs compared to their individual counterparts in view of enhanced local fields associated with the core-shell structure. Thus, the present nanostructured materials are excellent candidates as saturable absorbers and optical limiters.
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