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Abstract Structural deformation modifies the bandgap, exciton fine structure and phonon energy of semiconductors, providing an additional knob to control their optical properties. The impact can be exploited in colloidal semiconductor quantum dots (QDs), wherein structural stresses can be imposed in three dimensions while defect formation is suppressed by controlling surface growth kinetics. Yet, the control over the structural deformation of QDs free from optically active defects has not been reached. Here, we demonstrate strain-graded CdSe-ZnSe core-shell QDs with compositionally abrupt interface by the coherent pseudomorphic heteroepitaxy. Resulting QDs tolerate mutual elastic deformation of varying magnitudes at the interface with high structural fidelity, allowing for spectrally stable and pure emission of photons at accelerated rates with near unity luminescence efficiency. We capitalize on the asymmetric strain effect together with the quantum confinement effect to expand emission envelope of QDs spanning the entire visible region and exemplify their use in photonic applications.

Abstract Colloidal Ag(In,Ga)S2 nanocrystals (AIGS NCs) with the band gap tunability by their size and composition within visible range have garnered surging interest. High absorption cross-section and narrow emission linewidth of AIGS NCs make them ideally suited to address the challenges of Cd-free NCs in wide-ranging photonic applications. However, AIGS NCs have shown relatively underwhelming photoluminescence quantum yield (PL QY) to date, primarily because coherent heteroepitaxy has not been realized. Here, we report the heteroepitaxy for AIGS-AgGaS2 (AIGS-AGS) core-shell NCs bearing near-unity PL QYs in almost full visible range (460 to 620 nm) and enhanced photochemical stability. Key to the successful growth of AIGS-AGS NCs is the use of the Ag-S-Ga(OA)2 complex, which complements the reactivities among cations for both homogeneous AIGS cores in various compositions and uniform AGS shell growth. The heteroepitaxy between AIGS and AGS results in the Type I heterojunction that effectively confines charge carriers within the emissive core without optically active interfacial defects. AIGS-AGS NCs show higher extinction coefficient and narrower spectral linewidth compared to state-of-the-art heavy metal-free NCs, prompting their immediate use in practicable applications including displays and luminescent solar concentrators (LSCs).

Heteroepitaxy on colloidal nanocrystals often yields defective heterostructures due to intricate reaction pathways. Here, the authors decode the surface chemistry at the molecular level to realise defect-free interfaces with atomic uniformity.

Hybrid quantum dot light-emitting diodes exhibit barrier-less carrier injection despite a seemingly unfavourable energy landscape. Here, Lee et al. unravel the origin of this barrier-less carrier injection, showing the critical role of surface states of quantum dots.

Designing high-resolution displays based on colloidal quantum dots remains a challenge. Here, the authors demonstrate a photo-patterning method to develop CdSe-based core-shell quantum dots patterns of red, green and blue colours with diameters ranging from 7 to 20 nm and resolution of 1400 pixels per inch.

Colloidal semiconductor nanocrystals, referred to as quantum dots (QDs), have unique and superb photophysical properties, promising a variety of applications ranging from optoelectronics and energy harvesting to agriculture. The last decade witnessed a tremendous advance in QDs and their successful debut in displays, and now, QDs are equipped with environmental benignity to expand their territory to everyday life. From this perspective, the current research status and future perspective of environmentally benign QDs as building blocks for light-generating and light-harvesting applications are provided. Also provided is an overview of the progress made in the chemistry (colloidal synthesis, surface chemistry, and heterostructuring) and in their photophysical and electrical properties from the viewpoint of their use in light-emitting or light-harvesting applications. Grounded on the current status of heavy-metal-free QDs compared with cutting-edge technologies, the perspective of environmentally benign QDs for practical use and future research directions is discussed.

Biofuel cells offer biocompatibility and operation at mild conditions, but application is limited by relatively low output power. Here the authors use layer-by-layer assembly for glucose oxidase-coated metallic cotton fibers for use as electrodes in a hybrid biofuel cell to achieve high output power.

Quasi-type II heterostructured nanocrystals (NCs) have been of particular interest due to their great potential for controlling the interplay of charge carriers. However, the lack of material choices for quasi-type II NCs restricts the accessible emission wavelength from red to near-infrared (NIR), which hinders their use in light-emitting applications that demand a wide range of visible colors. Herein, we demonstrate a new class of quasi-type II nanoemitters formulated in ZnSe/ZnSe1-XTeX/ZnSe seed/spherical quantum well/shell heterostructures (SQWs) whose emission wavelength ranges from blue to orange. In a given geometry, ZnSe1-XTeX emissive layers grown between the ZnSe seed and the shell layer are strained to fit into the surrounding media, and thus, the lattice mismatch between ZnSe1-XTeX and ZnSe is effectively alleviated. In addition, composition of the ZnSe1-XTeX emissive layer and the dimension of the ZnSe shell layer are engineered to tailor the distribution and energy of electron and hole wave functions. Benefitting from the capabilities to tune the charge carriers on demand and to form defect-free heterojunctions, ZnSe/ZnSe1-XTeX/ZnSe/ZnS NCs show near-unity photoluminescence quantum yield (PL QY>90%) in a broad range of emission wavelengths (peak PL from 450 nm to 600 nm). Finally, we exemplify dichromatic white NC-based light-emitting diodes (NC-LEDs) employing the mixed layer of blue- and yellow-emitting ZnSe/ZnSe1-XTeX/ZnSe/ZnS SQW NCs.

With ligand-mediated layer-by-layer assembly between metal nanoparticles and small organic molecules, the authors prepare metallic paper electrodes for supercapacitors with high power and energy densities. This approach could be extended to various electrodes for portable/wearable electronics.

Gallium ion incorporation into silver indium gallium sulfide nanocrystals is investigated by various methods, including photoluminescence (PL) and X-ray photoelectron spectroscopy. The ZnS shell-growth enhances a PL quantum yield of up to 16%, with which the quantum dot light-emitting diode was successfully fabricated. [ABSTRACT FROM AUTHOR]

Quantum dot light-emitting diodes (QLEDs) are intensively developed in the display industry owing to their outstanding optoelectronic properties. However, their limited stability significantly limits broader display applications. Recently, a few studies have highlighted a phenomenon known as positive aging, in which post-treatment with a UV-curable acidic resin enhances both the lifetime and efficiency of QLEDs, thus offering a promising approach for overcoming limited lifetimes. Nonetheless, these treatments involve high-viscosity acidic resins, necessitating simpler processes for practical commercialization. In this study, a comparable performance-enhancing effect was verified by simply premixing the most abundant component of acidic resin, 2-hydroxyethyl methacrylate (HEMA), with ZnMgO (ZMO) to create an electron transporting layer. The QLED developed in this study, which incorporates HEMA-premixed ZMO, demonstrated 1.4- and 2.1-fold improvements in external quantum efficiency and half-lifetime, respectively. Comprehensive analyses of both the thin films and devices were conducted to elucidate the reasons behind these enhancements. [ABSTRACT FROM AUTHOR]

An innovative and robust method is described for the preparation of nanocomposite multilayers, which has allowed accurate control over the placement of functional groups as well as the composition and dimensions of individual layers/internal structure. This new method has opened a new way for designing functional film devices based on nanocomposite multilayers.

Nanocrystalquantum dots (QDs) are attractive materials for applications as lasermedia because of their bright, size-tunable emission and the flexibilityafforded by colloidal synthesis. Nonradiative Auger recombination,however, hampers optical amplification in QDs by rapidly depletingthe population of gain-active multiexciton states. In order to elucidatethe role of Auger recombination in QD lasing and isolate its influencefrom other factors that might affect optical gain, we study two typesof CdSe/CdS core/shell QDs with the same core radii and the same totalsizes but different properties of the core/shell interface (“sharp”vs “smooth”). These samples exhibit distinctly differentbiexciton Auger lifetimes but are otherwise virtually identical. Thesuppression of Auger recombination in the sample with a smooth (alloyed)interface results in a notable improvement in the optical gain performancemanifested in the reduction of the threshold for amplified spontaneousemission and the ability to produce dual-color lasing involving boththe band-edge (1S) and the higher-energy (1P) electronic states. Wedevelop a model, which explicitly accounts for the multiexciton natureof optical gain in QDs, and use it to analyze the competition betweenstimulated emission from multiexcitons and their decay via Auger recombination.These studies re-emphasize the importance of Auger recombination controlfor the realization of real-life QD-based lasing technologies andoffer practical strategies for suppression of Auger recombinationvia “interface engineering” in core/shell structures. [ABSTRACT FROM AUTHOR]

Purpose: The traumatic transection is located in the normal sized aortic isthmus where the angle is curved. We found a reversal of upper and lower blood pressure differences among patients who underwent thoracic endovascular aortic repair (TEVAR) for transection of the thoracic aorta. We investigated the isthmus stenosis in patients who underwent TEVAR for aortic injury using computed tomography. Materials and Methods: Sixteen patients who underwent TEVAR for transection were divided in two groups: the aortic narrowing (AN) group and the non-aortic narrowing (NAN) group. AN was defined as stent graft folding more than 5 mm at the isthmus confirmed by computed tomography. The length of aorta at isthmus, pseudoaneurysm, and angle of isthmus were measured. Results: AN was noted in five patients (31.3%). The area index in the NAN group (2.16±0.35 cm2/m2) was larger than that in the AN group (1.74±0.77 cm2/m2). The size of the pseudoaneurysm in the NAN group (31.9±4.2 mm) was smaller than that in the AN group (37.4±7.5 mm). The distance from the subclavian artery in the NAN group (15.7±9.3 mm) was longer than that in the AN group (8.4±3.2 mm) but not statistically significant. The angle of the isthmus in the NAN group (131±6 degrees) was larger than that in the AN group (107±3 degrees), and this was the only statistically significant difference (P=0.002). Conclusion :AN by stent graft folding should be considered when performing TE-VAR in aortic injury with an acute angle of the isthmus less than 110 degrees.

Critical illness neuromyopathy (CINM) is a sporadically reported disease in the setting of an intensive care unit developing in the process of managing a critical illness. The disease primarily affects the motor and sensory axons and results in severe limb weakness rendering ventilator weaning extremely difficult. We report a case of CINM after cardiac valve surgery. Quadriplegia developed after the operation and resolved slowly over the following 2 months. The patient was discharged home free of neurologic symptoms.

We report scalable controlled synthesis of CdSe tetrapodswithhigh morphological uniformity based on the continuous precursor injection(CPI) approach with halide ligands. The CPI approach involves thesuccessive injection of precursors into the seed solution at a controlledrate so that the reaction condition remains in the kinetic growthregime. To initiate the successful development of tetrapod structure,the controlled amount of halide ligands are added during the reaction,which triggered the formation of wurtzite arms on {111}-facets ofthe zincblende seeds. The formation of the wurtzite phase is responsiblefor the halide-mediated displacement of oleate ligands, destabilizingthe embryonic CdSe phase on the zincblende seeds enabling the phasetransformation to more stable wurtzite phase on the hexagonal {111}-facets.On the basis of these halide-mediated phase transformation of CdSenanocrystals and the persistent kinetic growth induced by the CPIapproach, well-defined CdSe tetrapods with controlled arm length anddiameter have been produced in large quantity. [ABSTRACT FROM AUTHOR]

PbSe nanocrystal quantum dots (NQDs) are a promising active material for a range of optoelectronic devices, including solar cells, high-sensitivity infrared (IR) photodetectors, and IR-emitting diodes and lasers. However, device realization has been constrained by these NQDs' chemical instability toward oxidation, which leads to uncontrollable changes in optical and electronic properties. Here, we present a simple method to enhance the stability of PbSe NQDs against oxidation and to improve their optical properties through reaction with molecular chlorine. The chlorine molecules preferentially etch out surface Se ions and react with Pb ions to form a thin (1-2 monolayers) PbClx passivation layer which effectively prevents oxidation during long-term air exposure while passivating surface trap states to increase photoluminescence efficiency and decrease photocharging. Our method is simple, widely applicable to PbSe and PbS NQDs of a range of sizes, compatible with solution-based processes for fabricating NQD-based devices, and effective both in solution and in solid NQD films; thus, it is a practical protocol for facilitating advances over the full range of optoelectronic applications. [ABSTRACT FROM AUTHOR]

Utilizing the reactivity difference between TOPSe and TOPS, we synthesized InP@ZnSeS QDs with the composition gradient in a radial direction where ZnSe alleviated lattice strain and ZnS protected QDs from degradation so that we achieved QDs with high QE and photo/chemical stability. In terms of systematic investigation on the relationship between the shell nanostructure and QD stability, we demonstrated that QDs with thick gradient shells exhibited high QE and much enhanced stability against the shell degradation under UV irradiation, ligand exchange, or rigorous purification. This enhanced stability of InP@ZnSeS QDs is attributed to the improved uniformity of composition gradient shells, the efficient confinement of exciton wavefunctions, and the minimized surface oxidation and non-radiative decay via surface states generated by photo-oxidation or ligand exchange. Using InP@ZnSeS QDs with enhanced stability, we were able to demonstrate InP-based colloidal green-emitting QD-LEDs. Although the current status of InP@ZnSeS QDs is not fully optimized to realize practical optoelectronic devices, the approach taken in the present study (i.e., the composition gradient shell structure naturally made from reactivity difference in precursors) will give clues to facilitate the synthesis of InP QDs with advanced nanostructures. [ABSTRACT FROM AUTHOR]

A systematic analysis of the exciton-recombination zone within all-quantum dot (QD) multilayer films prepared by a layer-by-layer assembly method was made, using sensing QD layers in QD-based light-emitting diodes (QLEDs). Large area practical multicolored colloidal QLEDs were also demonstrated by patterning and placing variously colored QDs (red, orange, yellow-green, and green) in the exciton-recombination zone. [ABSTRACT FROM AUTHOR]

We demonstrated a facile synthesis of highly luminescent blue emitting Cd 1− xZn xS/ZnS core/shell structured nanocrystals (NCs) in straightforward and reproducible manner. The alloyed Cd 1− xZn xS cores with homogeneity in both size and composition were prepared by introducing S precursors (S dissolved in the noncoordinating solvent (1-octadecene)) into the mixed solution of Cd−Oleate (Cd(OA) 2) and Zn−Oleate (Zn(OA) 2) at elevated temperature (300 °C). ZnS shells were successively overcoated on the prepared cores by the second injection of S precursors (S powder dissolved in tributylphosphine, TBPS) directly into the reactor with existing alloyed Cd 1− xZn xS NC cores without any purification steps. The prepared NCs exhibit strong band edge emission with high photoluminescent quantum yield (PL QY, up to 80%) and narrow spectral bandwidth (fwhm < 25 nm), which is believed to originate from the successful growth of ZnS shell layers on the Cd 1− xZn xS cores and the interfacial compatibility between Cd 1− xZn xS cores and the ZnS shell layers through the intradiffusion of Zn atoms from the ZnS shells into the Cd 1− xZn xS cores during the shell formation reaction. The emission wavelength (PL λ max.) of Cd 1− xZn xS/ZnS core/shell NCs was finely tuned from violet (415 nm) to blue (461 nm) by adjusting the amount of S precursors in the first injection (S in 1-octadecene) and thus changing actual Cd content ratio in the alloyed Cd 1− xZn xS cores (0.49 ≤ x≤ 0.76). Furthermore, multigram (3 g) scale production of Cd 1− xZn xS/ZnS core/shell NCs with narrow size distribution and spectral bandwidth was also demonstrated. [ABSTRACT FROM AUTHOR]

We demonstrate a single-step synthetic method for highly luminescent (i.e., quantum yield up to 80%) and stable quantum dots (QDs) by using the reactivity difference between Cd and Zn precursors and that between Se and S precursors. A wide range of emission wavelengths (500−610 nm) with a narrow fwhm (<35 nm) is obtained by changing the ratios of the precursors. Under the reaction conditions selected, Cd- and Se (with a bit of S)-based cores are formed first and Zn- and S-based shells are formed successively; therefore, the QDs have a core/shell structure with composition gradients, which relieve the lattice mismatch between core and shells. The QDs are characterized using the combined techniques of HR-TEM, UV–vis, PL spectroscopy, and ICP-AES. The QDs also have energy gradients depending on their compositions in a radial direction, which energetically confine carriers (electrons and holes) to the cores. This leads to the stability of QDs during their surface passivation from oleic acid to mercaptopropionic acid and ensures their processibility for further purposes such as optoelectronic and biological applications. [ABSTRACT FROM AUTHOR]

This report describes the case of a 57-year-old man with an anterior mediastinal tumor. Four years previously, he underwent laparoscopic anterior resection for sigmoid colon cancer. Thirty months after that procedure, bilateral pulmonary metastasectomy was performed. Twelve months later, follow-up computed tomography revealed a 1-cm pulmonary nodule on the upper lobe of the right lung and a solid mass on the anterior mediastinum, and the patient was also observed to have an elevated serum carcinoembryonic antigen (CEA) level. Repeated pulmonary nodule resection and total thymectomy were performed. Immunohistochemical staining of the anterior mediastinal tumor revealed adenocarcinoma, and his serum CEA level returned to normal after the operation. These findings strongly suggested metastatic thymic adenocarcinoma from a colorectal cancer.

We present facile synthesis of bright CdS/CdSe/CdS@SiO2 nanoparticles with 72% of quantum yields (QYs) retaining ca 80% of the original QYs. The main innovative point is the utilization of the highly luminescent CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) as silica coating seeds. The significance of inorganic semiconductor shell passivation and structure design of quantum dots (QDs) for obtaining bright QD@SiO2 is demonstrated by applying silica encapsulation via reverse microemulsion method to three kinds of QDs with different structure: CdSe core and 2 nm CdS shell (CdSe/CdS-thin); CdSe core and 6 nm CdS shell (CdSe/CdS-thick); and CdS core, CdSe intermediate shell and 5 nm CdS outer shell (CdS/CdSe/CdS-SQW). Silica encapsulation inevitably results in lower photoluminescence quantum yield (PL QY) than pristine QDs due to formation of surface defects. However, the retaining ratio of pristine QY is different in the three silica coated samples; for example, CdSe/CdS-thin/SiO2 shows the lowest retaining ratio (36%) while the retaining ratio of pristine PL QY in CdSe/CdS-thick/SiO2 and SQW/SiO2 is over 80% and SQW/SiO2 shows the highest resulting PL QY. Thick outermost CdS shell isolates the excitons from the defects at surface, making PL QY relatively insensitive to silica encapsulation. The bright SiO2-coated SQW sample shows robustness against harsh conditions, such as acid etching and thermal annealing. The high luminescence and long-term stability highlights the potential of using the SQW/SiO2 nanoparticles in bio-labeling or display applications. [ABSTRACT FROM AUTHOR]

We demonstrate deep blue light-emitting diodes based on chemically synthesized Cd1[?]xZnxS@ZnS quantum dots (QDs). Composite films of poly-(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD) and 4,4',N,N'-diphenylcarbazole (CBP) are employed for facilitated hole injection into Cd1[?]xZnxS@ZnS QDs and uniform QD deposition. The fabricated devices possess moderate turn-on voltage (6 V) and external quantum efficiency (0.1-0.3%), and exhibit color-saturated blue emission with a narrow spectral bandwidth of full width at half maximum <25 nm (Commission Internationale de l'Eclairage (CIE) coordinates of (0.169, 0.024) and (0.156, 0.028) for devices with electroluminescence (EL) lmax at 434 and 454 nm, respectively). Most of the emission originates from the Cd1[?]xZnxS@ZnS QD layers (99% of the total EL emission). [ABSTRACT FROM AUTHOR]