Designing Highly Luminescent Molecular Aggregates via Bottom-Up Nanoscale Engineering.

Ulugbek Barotov et al. Journal of Physical Chemistry C 2021, 126 (1), 754-763.

Coupling of excitations between organic fluorophores in J-aggregates leads to coherent delocalization of excitons across multiple molecules, resulting in materials with high extinction coefficients, long-range exciton transport, and, in particular, short radiative lifetimes. Despite these favorable optical properties, uses of J-aggregates as high-speed light sources have been hindered by their low photoluminescence (PL) quantum yields (QYs). Here, we take a bottom-up approach to design a novel J-aggregate system with a large extinction coefficient, a high QY, and a short lifetime. Our results have implications for the development of a new generation of organic fluorophores that combine high speed, high QY, and solution processing

Blue Light Emitting Defective Nanocrystals Composed of Earth‐Abundant Elements.

Eric C. Hansen et al. Angewandte Chemie 2019, 58, 2-10.

Copper‐based ternary (I–III–VI) chalcogenide nanocrystals (NCs) are compositionally‐flexible semiconductors that do not contain lead (Pb) or cadmium (Cd). Cu‐In‐S NCs are the dominantly studied member of this important materials class and have been reported to contain optically‐active defect states. However, there are minimal reports of In‐free compositions that exhibit efficient photoluminescence (PL). Here, we report a novel solution‐phase synthesis of ≈4 nm defective nanocrystals (DNCs) composed of copper, aluminum, zinc, and sulfur with ≈20 % quantum yield and an attractive PL maximum of 450 nm.

Near-Infrared Quantum Dot Emission Enhanced by Stabilized Self-Assembled J-Aggregate Antennas. 

Francesca S. Freyria et al. Nano Letters 2017, 17, 7665-7674.

Enhancing photoluminescent emission (PL) in the near-infrared–infrared (NIR–IR) spectral region has broad applications from solar energy conversion to biological imaging. We show that self-assembled molecular dye J-aggregates (light-harvesting nanotubes, LHNs) can increase the PL emission of NIR PbS quantum dots (QDs) in both liquid and solid media more than 8-fold, promoted primarily by a long-range antenna effect and efficient Förster resonance energy transfer (FRET) from donor to acceptor.

Scalable Synthesis of InAs Quantum Dots Mediated through Indium Redox Chemistry.

Matthias Ginterseder et al. J. Am. Chem. Soc. 2020, 142 (9), 4088-4092.

Next-generation optoelectronic applications centered in the near-infrared (NIR) and short-wave infrared (SWIR) wavelength regimes require high-quality materials. Among these materials, colloidal InAs quantum dots (QDs) stand out as an infrared-active candidate material for biological imaging, lighting, and sensing applications. Despite significant development of their optical properties, the synthesis of InAs QDs still routinely relies on hazardous, commercially unavailable precursors. Herein, we describe a straightforward single hot injection procedure revolving around In(I)Cl as the key precursor.

Zinc Thiolate Enables Bright Cu-Defficient Cu-In-S/ZnS Quantum Dots.

Eric C. Hansen et al. Small 2019, 15 (27), 1901462.

Copper indium sulfide (CIS) colloidal quantum dots (QDs) are a promising candidate for commercially viable QD‐based optical applications, for example as colloidal photocatalysts or in luminescent solar concentrators (LSCs). eveloping an understanding and control over the growth of electronically passivating inorganic shells would enable further improvements of the photophysical properties of CIS QDs. To improve the optical properties of CIS QDs, the focus is on the growth of inorganic shells via the popular metal‐carboxylate/alkane thiol decomposition reaction.

Colloidal atomic layer deposition growth of PbS/CdS core/shell quantum dots. 

Michel Nasilowski et al. Chem. Comm. 2017, 53, 869-872.

Traditionally, PbS/CdS quantum dots (QDs) have been synthesized via a cation exchange method, making fine control over shell growth challenging. We show here that colloidal atomic layer deposition (c-ALD) allows for the sequential growth of single monolayers of the shell, thus creating a ‘true’ CdS shell on PbS QDs.

Seedless Continuous Injection Synthesis of Indium Phosphide Quantum Dots as a Route to Large Size and Low Size Dispersity.

Odin B. Achorn et al. Chem. Mater. 2020, 32 (15), 6532–6539.

In this article, we describe a new method to synthesize large InP QDs with low size dispersity that does not require a hot-injection or heat-up step. Instead, nucleation, growth, and size focusing all take place continuously during a slow syringe-pump-mediated continuous injection of precursors into the reaction mixture. We then developed a growth model that is consistent with our observations, and we used it to improve our method with a variable-rate injection that controls the concentration of intermediates to extend growth and prevent secondary nucleation. This work demonstrates a new method to synthesize large InP QDs that may be attractive to large-scale industrial processes because of its simplicity and potential scalability.

A Ligand System for the Flexible Functionalization of Quantum Dots via Click Chemistry.

Yue Chen et al. Angewandte Chemie 2018, 57, 4652-4656.

We present a novel ligand, 5‐norbornene‐2‐nonanoic acid, which can be directly added during established quantum dot (QD) syntheses in organic solvents to generate “clickable” QDs at a few hundred nmol scale. This ligand has a carboxyl group at one terminus to bind to the surface of QDs and a norbornene group at the opposite end that enables straightforward phase transfer of QDs into aqueous solutions via efficient norbornene/tetrazine click chemistry. The QDs exhibit high targeting efficiency and minimal nonspecific binding.