Ph. D. THESIS COLLOQUIUM
Name: Ms. Parna Roy
Research Supervisor: Prof. Anshu Pandey
Title: “Engineering Photon Emission Statistics of Single Nanocrystal: From Quantum to Classical”
Date & Time: Monday, 16th June 2025 at 11:00 a.m.
Venue: Rajarshi Bhattacharya Memorial Lecture Hall, Chemical Sciences Building
Abstract:
The development of stable and bright colloidal nanocrystals has long held promise for quantum photonics,1 optoelectronics,2 and bioimaging 3. Although isolated colloidal nanoparticle can be used for single-photon emission,4,5 these often suffer from blinking and reduced performance under high excitation fluences.6 To overcome these challenges, I designed a novel quantum dot architecture that achieves high-fidelity single-photon emission even in the absence of spectral filtering7 at a high excitation fluence by successfully rejecting the extra multiexcitons in the nanocrystal with the help of Auger recombination.8
However, persistent blinking behaviour in these dots necessitated further investigation.9 To address this, I developed the non-blinking variety of the engineered quantum dots by achieving exquisite control over the surface chemistry. The strain profiles of these nanocrystals were determined and found to be exhibiting minimal surface strain. These new variants of the engineered nanocrystals show absence of fluorescence OFF state at both conditions of rapid re-excitation and variable power along with retaining its single-photon emission behaviour.
Furthermore, I have explored photon statistics in the case of conventional fluorescent markers used in laser microscopy. Because of the presence of exciton-exciton interactions, the luminosity is reduced by a substantial amount at high excitation fluences. To address this, I synthesized a distinct set of emitters capable of efficiently decreasing the interaction by achieving a net zero coulombic interaction between them.10 Optical studies on these emitters indicate significantly reduced excitonic interactions, favouring multiphoton emission events. Increase in luminosity and stability is observed in single particles and ensembles for this new class of nanocrystals. Together, these studies highlight the pathway toward high-performance, application-specific colloidal nanocrystals.
References:
(1) Roy, P.; Gogoi, P.; Pandey, A. Solution Grown Quantum Dots for Quantum Science. J. Phys. Condens. Matter 2024, 37 (9), 93001.
(2) Roy, P.; Mukherjee, A.; Mondal, P.; Bhattacharyya, B.; Narayan, A.; Pandey, A. Electronic Structure and Spectroscopy of I-III-VI2 Nanocrystals: A Perspective. J. Phys. Chem. C 2022, 126 (17), 7364–7373.
(3) Zhang, B.; Hu, R.; Wang, Y.; Yang, C.; Liu, X.; Yong, K.-T. Revisiting the Principles of Preparing Aqueous Quantum Dots for Biological Applications: The Effects of Surface Ligands on the Physicochemical Properties of Quantum Dots. RSC Adv. 2014, 4 (27), 13805–13816.
(4) Park, Y.-S.; Guo, S.; Makarov, N. S.; Klimov, V. I. Room Temperature Single-Photon Emission from Individual Perovskite Quantum Dots. ACS Nano 2015, 9 (10), 10386–10393.
(5) Lounis, B.; Moerner, W. E. Single Photons on Demand from a Single Molecule at Room Temperature. Nature 2000, 407 (6803), 491–493.
(6) Nair, G.; Zhao, J.; Bawendi, M. G. Biexciton Quantum Yield of Single Semiconductor Nanocrystals from Photon Statistics. NANO Lett. 2011, 11 (3), 1136–1140.
(7) Morozov, S.; Vezzoli, S.; Myslovska, A.; Di Giacomo, A.; Mortensen, N. A.; Moreels, I.; Sapienza, R. Purifying Single Photon Emission from Giant Shell CdSe/CdS Quantum Dots at Room Temperature. Nanoscale 2023, 15 (4), 1645–1651.
(8) Roy, P.; Pandey, A. Engineering Quantum Dots for Improved Single Photon Emission Statistics. J. Chem. Phys. 2024, 160 (20).
(9) Chen, O.; Zhao, J.; Chauhan, V. P.; Cui, J.; Wong, C.; Harris, D. K.; Wei, H.; Han, H. S.; Fukumura, D.; Jain, R. K.; Bawendi, M. G. Compact High-Quality CdSe-CdS Core-Shell Nanocrystals with Narrow Emission Linewidths and Suppressed Blinking. Nat. Mater. 2013, 12 (5), 445–451.
(10) Roy, P.; Pandey, A. Enhanced Multiexciton Emission Quantum Yields in Nonblinking Interlinked Nanocrystals. J. Phys. Chem. C 2024, 128 (7), 2948–2952.