Nano-engineering Core/Shell Quantum Dots for Ultimate Utility in Light-emission Applications

H. Htoon, J.A. Hollingsworth
Los Alamos National Laboratory,
United States

Keywords: quantum dots, non-blinking, solid-state lighting, bioimaging, particle tracking, biomedicine, single-photon source


Quantum-confinement effects have been used for decades to tune semiconductor opto-electronic properties. More recently, particle-size control as the primary means for properties control has been succeeded by nanoscale hetero-structuring. In this case, the nanosized particle is modified to include internal, nanoscale interfaces that induce additional changes to semiconductor properties. These changes entail enhancements to the well-known size-induced properties as well as development of unexpected ‘emergent’ behaviors. A common structural motif involves enveloping a spherical semiconductor nanocrystal, i.e., a quantum dot (QD), within a shell(s) of different composition. Greater structural and properties complexity can be achieved by extending the dimension of the shell material(s) to create asymmetric seeded nanorods or "multipods,” adding shape effects to the mechanisms for tuning fundamental nanoscale photonic processes. This talk will focus on our use of solution-phase colloidal synthesis to fabricate nano-engineered semiconductor nanostructures with novel functionality for light-emission applications from solid-state lighting to biomedicine, emphasizing ‘giant’ core/shell QDs (gQDs)1. Due to their internal nanoscale structure (thick shell, type II band alignment, potentially alloyed interface), gQDs exhibit a range of fundamentally interesting and useful behaviors, including being non-blinking and non-photobleaching,2-6 and remarkably efficient emitters of multiexcitons due to extreme suppression of Auger recombination.7,8 Recent work using multiple-shell constructs to achieve dual-color excitonic emission and shape-tuning to realize dual-color multiexcitonic emission9 – both with strong blinking suppression and enhanced single-nanostructure photostability – will be discussed. Finally, new synthesis (automated) and characterization (correlated optical/structural10) tools will be shown that facilitate the intelligent design of next-gen functional photonic-nanostructures. 1.Hollingsworth, J.A. et al. U.S. Patent 7,935,419 (2011): Thick-shell Nanocrystal Quantum Dots. 2.Chen, Y. et al. J. Am. Chem. Soc. 2008, 130, 5026-5027. 3.Vela, J. et al. Biophotonics 2010, 3, 706-717. 4.Dennis, A.M. et al. Nano Lett. 2012 12, 5545-5551. 5.Ghosh, Y. et al. J. Am. Chem. Soc. 2015, 137, 3755-3758. 7.Mangum, B.D. et al. Nanoscale 2014, 6, 3712. 8.Gao, Y. et al. Adv. Optical Mater. 2015, 3, 39-43. 9.Mishra, N.,* Orfield, N.J.* et al. Nat. Commun. Accepted, 2017. 10.Orfield, N.J. et al. ACS Nano 2016, 10, 1960-1968.