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1. Versatile Dehydration‐Assisted Functionalization of Quantum Dots and Rods

   https://doi.org/10.1002/anie.202410247  

   Chen, Chi; Luo, Xin; Bathe, Mark (September 2024, Angewandte Chemie International Edition)

   Abstract Functionalization of quantum dots (QDs) and quantum rods (QRs) with ligands is essential for their further practical application across various domains. Dehydration‐assisted functionalization (DAF) is a versatile method applicable to a wide range of hydrophilic ligands with an affinity to the surface of QDs and QRs. This approach facilitates rapid one‐pot ligand exchange and dense modification by efficiently transferring these ligands onto the surface of QDs and QRs. This study demonstrates the efficacy of DAF in preparing chiral QRs, engineering the surface charge of QDs, utilizing QR aggregates, and conjugating dense DNA onto cadmium‐free InP/ZnS QDs. DAF therefore offers a versatile solution for hydrophilic ligand functionalization of QDs and QRs applicable to diverse applications. 

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2. Dopant vs free carrier concentrations in InAs/GaAs semiconductor quantum dots

   https://doi.org/10.1063/5.0244331  

   Brubach, J; Huang, T-Y; Borrely, T; Greenhill, C; Walrath, J; Fedele, G; Yang, Y-C; Zimmerman, A; Goldman, R S (March 2025, Applied Physics Letters)

   Semiconductor quantum dots (QDs) are nanostructures that can enhance the performance of electronic devices due to their 3D quantization. Typically, heterovalent impurities, or dopants, are added to semiconducting QDs to provide extra electrons and improve conductivity. Since each QD is expected to contain a few dopants, the extra electrons and their parent dopants have been difficult to locate. In this work, we investigate the spatial distribution of the extra electrons and their parent donors in epitaxial InAs/GaAs QDs using local-electrode atom-probe tomography and self-consistent Schrödinger–Poisson simulations in the effective mass approximation. Although dopants are provided in both layers, the ionized donors primarily reside outside of the QDs, providing extra electrons that are contained within the QDs. Indeed, due to the quantum confinement-induced enhancement of the donor ionization energy within the QDs, a lower fraction of dopants within the QDs are ionized. These findings suggest a pathway toward the development of 3D modulation-doped nanostructures. 

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3. Near-infrared electroluminescence of AlGaN capped InGaN quantum dots formed by controlled growth on photoelectrochemical etched quantum dot templates

   https://doi.org/10.1364/PRJ.441122  

   Wei, Xiongliang; Al Muyeed, Syed Ahmed; Xue, Haotian; Palmese, Elia; Song, Renbo; Tansu, Nelson; Wierer, Jonathan J. (December 2021, Photonics Research)

   Near-infrared electroluminescence of InGaN quantum dots (QDs) formed by controlled growth on photoelectrochemical (PEC) etched QD templates is demonstrated. The QD template consists of PEC InGaN QDs with high density and controlled sizes, an AlGaN capping layer to protect the QDs, and a GaN barrier layer to planarize the surface. Scanning transmission electron microscopy (STEM) of Stranski–Krastanov (SK) growth on the QD template shows high-In-content InGaN QDs that align vertically to the PEC QDs due to localized strain. A high-Al-content ${\mathrm{Al}}_{0.9}{\mathrm{Ga}}_{0.1}\mathrm{N}$capping layer prevents the collapse of the SK QDs due to intermixing or decomposition during higher temperature GaN growth as verified by STEM. Growth of low-temperature (830°C) p-type layers is used to complete the p-n junction and further ensure QD integrity. Finally, electroluminescence shows a significant wavelength shift (800 nm to 500 nm), caused by the SK QDs’ tall height, high In content, and strong polarization-induced electric fields. 

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4. Enabling Tailorable Optical Properties and Markedly Enhanced Stability of Perovskite Quantum Dots by Permanently Ligating with Polymer Hairs

   https://doi.org/10.1002/adma.201901602  

   Yoon, Young_Jun; Chang, Yajing; Zhang, Shuguang; Zhang, Meng; Pan, Shuang; He, Yanjie; Lin, Chun_Hao; Yu, Shengtao; Chen, Yihuang; Wang, Zewei; et al (June 2019, Advanced Materials)

   Abstract Instability of perovskite quantum dots (QDs) toward humidity remains one of the major obstacles for their long‐term use in optoelectronic devices. Herein, a general amphiphilic star‐like block copolymer nanoreactor strategy for in situ crafting a set of hairy perovskite QDs with precisely tunable size and exceptionally high water and colloidal stabilities is presented. The selective partition of precursors within the compartment occupied by inner hydrophilic blocks of star‐like diblock copolymers imparts in situ formation of robust hairy perovskite QDs permanently ligated by outer hydrophobic blocks via coprecipitation in nonpolar solvent. These size‐ and composition‐tunable perovskite QDs reveal impressive water and colloidal stabilities as the surface of QDs is intimately and permanently ligated by a layer of outer hydrophobic polymer hairs. More intriguingly, the readily alterable length of outer hydrophobic polymers renders the remarkable control over the stability enhancement of hairy perovskite QDs. 

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5. π–π Interactions Mediated Pyrene Based Ligand Enhanced Photoresponse in Hybrid Graphene/PbS Quantum Dots Photodetectors

   https://doi.org/10.1002/aelm.202100672  

   Ahn, Seungbae; Ingrosso, Chiara; Panniello, Annamaria; Striccoli, Marinella; Bianco, Giuseppe_Valerio; Agostiano, Angela; Bruno, Giovanni; Curri, Maria_Lucia; Vazquez‐Mena, Oscar (October 2021, Advanced Electronic Materials)

   Abstract Hybrid graphene and quantum dots (QDs) photodetectors merge the excellent conductivity and ambipolar electric field sensitivity of graphene, with the unique properties of QDs. The photoresponsivity of these devices depends strongly on the charge transfer at the graphene/QDs interface. Here 1‐pyrene butyric acid (PBA)‐coated PbS QDs with single layer graphene (SLG) are used to investigate the effect of pyrene as a π–π mediator to enhance charge transfer at the SLG/QDs junction under illumination. The surface chemistry at the QD–QD and SLG/QD interface is studied with the conventional tetrabutylammonium iodide (TBAI) QD linker. The hybrid SLG/QD photodetectors with PBA as a SLG‐QD linker demonstrate a photoresponse up to 30% higher than that recorded for devices where only TBAI is used, due to the strong electron coupling between SLG and QDs. Transconductance measurements show that PBA provokes electron depletion in SLG ascribed to the tendency to delocalize the QDs holes, favoring their transfer to SLG. This surface ligand is found to improve the interaction between the QDs light absorbers and the SLG charge collector, leading to an increased photodetection response. This demonstrates that ligand engineering can enhance charge dynamics and boost the performance of the hybrid device. 

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