Quantum Dots Research Articles

Improving Internal Exciton Confinement for Efficient CdZnSeS-Based Blue Quantum Dot Light-Emitting Diodes.

Quantum-dot light-emitting diodes (QLEDs) are thought to be the base for next-generation display technology. However, the performance of blue-emitting QLEDs still falls behind those of green and red ones, which can be attributed to the energy loss from Auger recombination and the strong coupling of excitons with surface states. Blue quantum dots (QDs) with giant CdZnSeS alloy cores are expected to improve the internal confinement of excitons due to the nonmonotonical energy landscape of their conduction band, while they haven't shown high performance in QLEDs due to insufficient optimization of their shell structures. In this work, giant CdZnSeS alloy cores were synthesized by diffusing Zn atoms into CdSeS cores, so that the core/shell lattice stress was released due to the optimized gradient compositions. As a result, exciton transfer and Auger recombination are both suppressed, leading to a breakthrough external quantum efficiency (EQE) of 24% in blue QLEDs with giant CdZnSeS alloy cores. Compared to the more extensively studied blue quantum dots with CdSeZn alloy cores, blue QLEDs with giant CdZnSeS alloy cores also benefit from the suppressed Fermi level and nonmonotonical energy landscape of the conduction band minimum (CBM), which are crucial for confining the wavefunctions of the excitons. The improved exciton confinement explained the superior performances of giant CdZnSeS alloy cores over CdSeZn cores in blue QLEDs.

Eliminating the confined dark-exciton qubit precession using an externally applied magnetic field

We investigate experimentally and theoretically the behavior of the confined dark exciton in an InAs/GaAs semiconductor quantum dot, under the application of an external magnetic field in a Voigt configuration. We show that by varying the magnitude and direction of the external field one can accurately control the dark-exciton fine-structure splitting. In addition, we show that the dark-exciton spin state is approximately polarized along the cubic crystallographic directions [100] or equivalents. By comparing our experimental results with a model for the exchange and Zeeman interactions, we find the conditions for nullifying the fine-structure splitting between the two eigenstates of the dark exciton, thereby stopping its qubit precession. Published by the American Physical Society 2025

Ratiometric Dual-Response Quantum Dot Spherical Nucleic Acid for Monitoring Viral Secondary Bacterial Infections.

Viral-bacterial coinfections present intricate pathologies that exacerbate disease progression and elevate mortality rates. Understanding the dynamic interplay between viruses and bacteria during coinfection is critical for developing effective therapeutic interventions. However, current diagnostic tools primarily rely on static detection methods, limiting their ability to monitor real-time infection dynamics. Here, we introduce a ratiometric, dual-responsive quantum dot spherical nucleic acid (QD-SNA) probe capable of simultaneously detecting viral- and bacterial-specific markers in vivo. This probe enables real-time monitoring of coinfections, as demonstrated in a mouse model of influenza virus (H1N1) and methicillin-resistant Staphylococcus aureus infection. By providing dynamic, visual insights into the coinfection process, the QD-SNA probe holds significant potential for preclinical drug screening and the diagnosis of respiratory pathogen infections.

The mechanism between solar cell efficiency and geometry of truncated quantum dots: implications for practical application

The mechanism between solar cell efficiency and geometry of truncated quantum dots: implications for practical application

Controllable Er-Doped Mode-Locked Fiber Laser Based on MoP Nanosheets and Quantum Dots

Controllable Er-Doped Mode-Locked Fiber Laser Based on MoP Nanosheets and Quantum Dots

Effect of Quantum Dot-Based Remote Lenses on the Emission Properties of White LED Lighting Studied by Optical Simulation and Experiment

The introduction of side-emitting lenses into white light-emitting diodes (LEDs) has enabled thin panel lighting technology based on LED technology, but also presents the disadvantage of low color rendering due to insufficient red components in the spectra of typical white LEDs. Additional application of remote quantum dot (QD) components such as QD films or caps presents the issues of increased numbers of components and higher costs. In this study, we incorporated red QDs directly into a lens placed on white LEDs and analyzed the effects of QD lenses on the optical characteristics of a lighting device through experiments and simulations. By incorporating red CdSe/ZnS QDs into UV-curable resin to fabricate QD lenses and applying them to white LEDs, we significantly improved the color rendering index and were able to adjust the correlated color temperature over a wide range between 2700 and 9900 K. However, as the concentration of QDs in the lens increased, scattering by the QD particles was enhanced, strengthening the Lambertian distribution in the intensity plot. Following the development of optical models for QD lenses under experimental conditions, comprehensive optical simulations of white LED lighting systems revealed that increasing the device height proved more effective than modifying TiO2 scattering particle concentration in the diffuser plate for mitigating QD-induced bright spots and enhancing illumination uniformity.

Coherent phonon source based on electron spin resonance in a quantum-dot qubit

One of the key requirements for quantum phononics, especially for scenarios involving quantum communication and quantum-state transduction, is the implementation of a controlled phonon source, ultimately with the capacity to source single phonons at some desired generation rate. In this article, we describe a scheme for the controlled sourcing of phonons that exploits an electron-spin resonance between the Zeeman-split levels of a gated quantum dot. This on-chip scheme allows for broad tunability of the energy of the generated phonons, with convenient electrical control. By providing a compact and coherent source, this scheme is also well suited to the construction of more-extended phononic circuits, involving the sourcing, transmission and detection of phononic signals.

Calculation of refractive index changes and intersubband optical absorption coefficients in a pyramidal quantum dot

In this work, the energy levels and wave functions of the pyramidal quantum dot (PQD) are numerically calculated using the finite element method. Then, the refractive index changes (RICs) and absorption coefficients (ACs) are determined. To this goal, we have used the compact-density matrix method. Numerical results have been presented for the GaAs/Al[Formula: see text]Ga[Formula: see text]As pyramid quantum dot. It is found that the change of structural parameters like quantum dot sizes has an important influence on energy levels, wave functions, and optical properties of PQD. With increasing the height of PQD, the Acs, and RICs increase and shift toward higher energies.

Atomic-scale passivation strategy for stabilizing tricolor perovskite quantum dots with enhanced photoluminescence

Perovskite quantum dots (QDs) are promising light-emitting materials for next-generation displays. Nevertheless, their practical applications are hindered by poor stability. In this study, we present a mild atomic layer deposition (ALD) method using dimethylaluminum isopropoxide (DMAI) precursor at a lower temperature (50 °C) to enable simultaneous stabilization of the RGB QDs while enhancing their photoluminescence (PL) intensity. The DMAI precursors react with the –COOH groups of oleic acid, passivating surface defects by forming Al–O bonds between the ligands and perovskite QDs, thereby improving optical performance. This is followed by the formation of a nanoscale AlOx thin film coating that protects the octahedral structure of the ODs. The passivated perovskite RGB QDs exhibit significantly enhanced PL intensity and prolonged fluorescence lifetime, retaining over 80% of their PL after exposure to water, intense light, and temperatures up to 150 °C. Furthermore, when used in tri-color micro-LEDs, the modified RGB perovskite QDs demonstrates 8 times longer operational stability compared to the original QDs. White LEDs have been also fabricated, exhibiting narrow spectra and stable PL intensity. These results highlight the potential of the mild ALD method with DMAI precursor in enhancing the stability and efficiency of optoelectronic devices under manufacturing and operating conditions.

Electric-Field Control of Photon Indistinguishability in Cascaded Decays in Quantum Dots.

Photon indistinguishability, entanglement, and antibunching are key ingredients in quantum optics and photonics. Decay cascades in quantum emitters offer a simple method to create entangled-photon-pairs with negligible multipair generation probability. However, the degree of indistinguishability of the photons emitted in a cascade is intrinsically limited by the lifetime ratio of the involved transitions. Here we show that, for the biexciton-exciton cascade in a quantum dot, this ratio can be widely tuned by an applied electric field. Hong-Ou-Mandel interference measurements of two subsequently emitted biexciton photons show that their indistinguishability increases with increasing field, following the theoretically predicted behavior. At the same time, the emission line width stays close to the transform-limit, favoring applications relying on the interference among photons emitted by different sources.

Black Phosphorus: Paving the Way for Flexible Supercapacitors in Wearable Electronics.

The utilization of flexible supercapacitors (FSCs) is gaining momentum in the realm of wearable electronics, owing to their multifarious advantages and immense potential for future applications. Black phosphorus (BP) is rapidly emerging as an auspicious material in the field of FSCs. The exceptional features of this material, including its remarkable surface area, excellent carrier mobility, anisotropic characteristics, impressive electrical conductivity, and rapid ion diffusion properties, render it highly suitable for practical applications. Some specifications, such as design, development, and safety concerns of emerging electrode materials for FSCs in wearable electronics, are highlighted here. This review briefly explains the various synthesis methods for bulk BP, single-layer and few-layer BP (FL-BP) fabrication methods, and black phosphorus quantum dots (BPQDs). Both top-down and bottom-up approaches are addressed for producing single/FL-BP. Also, this review discusses the interaction of BP with other 2D materials to make a synergistic effect and compares the electrochemical performance. Discover the latest breakthrough in wearable electronics with the first-ever review of BP-based FSC applications. From technical specifications to real-world applications, this review covers everything to know to stay ahead of the curve. So buckle up and get ready to explore the exciting world of BP-based FSC devices.

Electrochemical Immunosensor of Escherichia coli O157:H7 in Food based on PPY-PANI and Quantum Dot Microsphere Conjugates

Electrochemical Immunosensor of Escherichia coli O157:H7 in Food based on PPY-PANI and Quantum Dot Microsphere Conjugates

Broadband photodetectors based on PbS quantum dots synthesized using the multiple injection growth method

Abstract PbS colloidal quantum dot (CQD) photodiodes are becoming increasingly significant for their utility in short-wave infrared detection and imaging. Despite their promise, challenges persist in synthesizing large PbS quantum dots that extend their response wavelength beyond 1500 nm. The usual hot-injection method has problems because of changes in temperature, solution ratios, and the Ostwald ripening process, all of which make it harder to make large PbS quantum dots that are all the same size as the temperature rises. In this study, we introduced small-sized PbS quantum dots, which absorb light at approximately 600 nm, into a reaction system containing seed quantum dots that absorb light at approximately 1050 nm. This process was repeated on multiple occasions to facilitate the growth of the quantum dots, resulting in larger PbS quantum dots with an absorption peak at 1550 nm. By meticulously regulating parameters such as dosage, reaction time, and the number of injections, we successfully synthesized PbS quantum dots of varying sizes. This approach not only enables the production of PbS quantum dots with specific size requirements but also introduces novel insights into the synthesis mechanism of PbS. Furthermore, PbS CQD photodiodes were fabricated with reduced dark current densities by employing SnO2 synthesized via the sol–gel method as an electron transport layer, which better matches the energy bands of the larger PbS quantum dots. At ambient temperature, the photodiode demonstrated a responsivity of 290 mA W−1 with a normalized detectivity of 1.16 × 1011 Jones, thereby underscoring its promising potential for practical applications.

One-pot synthesis of photonic microparticles doped with light-emitting quantum dots.

Colloidal quantum dots (QDs) exhibit size-dependent, tuneable optical properties that render them useful in a wide range of technological applications. However, integration of QDs into structured materials remains a significant challenge due to their susceptibility to degradation under chemical or physical perturbations. Here, we present a facile, scalable one-pot co-assembly strategy to embed commercially available CdSe/ZnS core-shell quantum dots into photonic microparticles via the confined self-assembly of a poly(styrene)-b-poly(2-vinylpyridine) block copolymer in emulsion droplets. The resulting hybrid particles exhibit a well-defined concentric lamellar structure and the quantum dots are selectively incorporated into the domains formed by the poly(2-vinylpyridine) blocks. This design enables two different optical responses, i.e., vivid, non-iridescent structural colouration from photonic bandgap effects and stable engineered photoluminescence from the embedded QDs. The use of swelling agents provides an effective means to tune the photonic bandgap spectral position, extending the optical range to the entire visible region. Optical experiments reveal a subtle interplay between the photonic structure and QD emission, and the emission properties remain intact despite variations in the structural periodicity and matrix refractive index. This work highlights a robust platform for the integration of functional nanomaterials into photonic architectures, offering significant potential for applications in advanced light sources, displays, and sensing technologies. The simplicity of the approach, combined with its scalability, sets the stage for future exploration into hybrid photonic materials with tailored optical properties.

Optical refrigeration on cadmium selenide/cadmium sulfide quantum dots

Critical progress in perfecting semiconducting quantum dots’ photoluminescence quantum yield has been made in the past few years. The production of quantum dots with nearly unitary quantum yield has significantly expanded their possible applications, as it is the case of optical refrigeration. We report for the first time optical refrigeration achieved in cadmium selenide/cadmium sulfide (core/shell) structure nanocrystals. Experiments were carried out in colloidal quantum dots suspension, where the excitonic non-radiative decay paths of the quantum dots are effectively suppressed by applying sub-band excitation, eliminating the possible states for energy down-conversion. The cooling effect comes from the significant energy up-conversion observed in the photoluminescence spectra of the samples under sub-band excitation. These results highlight the possibility of realizing temperature control on semiconducting quantum dots through optical approaches, which could provide power cooling mechanism for nano devices and cryogenic systems.

Spin-exchange induced spillover on poor man's majoranas in minimal Kitaev chains.

The ``Poor Man's Majoranas'' (PMMs) [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection can ``spill over'' from one edge into another of the minimal Kitaev chain when perturbed electrostatically. As aftermath, this leads to a delocalized Majorana fermion (MF) at both the edges. Additionally, according to recent differential conductance measurements in a pair of superconducting and spinless quantum dots (QDs), such a PMM picture was brought to reality [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. Based on this scenario, we propose the spillover of the PMM when its QD is exchange coupled to a quantum spin $S$. We show that if this QD is perturbed by the exchange coupling $J$, solely the half $2S+1$ $(2S+2)$ of the fine structure stays explicit for a fermionic (bosonic) $S.$ Concurrently, the other half squeezes itself as the delocalized MF zero-mode. Particularly, turning-off the superconductivity the multiplicity $2S+1$ holds regardless the spin statistics. Meanwhile, the PMM spillover induced by $J$ becomes a statistics dependent effect. Hence, our findings contribute to the comprehension of spin-phenomena interplay with superconductivity in minimal Kitaev chains, offering insights
for future quantum computing devices hosting PMMs.

Thermoelectric performance of quantum dots embedded in an Aharonov-Bohm ring: a Pauli master equation approach

Within linear response theory using the Pauli master equation approach, we have investigated the thermoelectric properties of quantum dots (QDs) embedded in an Aharonov-Bohm (AB) ring weakly coupled to two metallic electrodes. This study explores the impact of magnetic flux on thermoelectric transport, emphasizing the role of quantum interference induced by the flux. When the magnetic flux is varied from 0 to one quantum of flux , both the electrical conductance and the thermoelectric figure of merit () significantly increase by two orders of magnitude. Moreover, our investigation into the effects of onsite and inter-site Coulomb interactions in this nanojunction indicates that an optimal ZT is attained with moderate onsite Coulomb interaction and minimal inter-site Coulomb interaction. We briefly discussed the effects of asymmetric arrangements of triple QDs within an AB ring. However, within our parameter regime, a symmetric arrangement offers superior thermoelectric performance compared to asymmetric configurations. Furthermore, we explored how increasing the number of QDs in the ring enhances the thermoelectric properties, resulting in a potential ZT value of around 0.43. This study shows that arranging multiple QDs symmetrically in an AB ring can result in significant thermoelectric performance in a nanostructured system at low temperatures.

Responsive carbon dot-embedded hybrid microgels for dual sensing of iron(III) and ciprofloxacin.

A novel hybrid material was synthesized through the integration of nitrogen-doped carbon quantum dots (NCQDs) within a cationic poly(N-isopropylacrylamide-co-N-3-aminopropyl methacrylamide) (PNIPAM-co-APMH) microgel to create a highly sensitive, selective and multi-responsive system (NCQDs@PNIPAM-co-APMH) with an impressive quantum yield of 42%. The resultant hybrid microgel was shown to be an exceptional dual-functional sensor for detecting ferric ions (Fe3+) and ciprofloxacin (CIP). The detection of Fe3+ was marked by a "turn-off" fluorescence response, facilitated by dynamic quenching mechanisms. In contrast, upon the introduction of CIP into the Fe3+-quenched system (Fe3+-NCQDs@PNIPAM-co-APMH), a "turn-on" fluorescence response was observed, with a corresponding LOD of 0.41 μM. A logic gate framework was employed to achieve sequential sensing of Fe3+ and CIP in an "off-on" manner. Furthermore, the material exhibited excellent recovery rates, ranging from 86% to 108%, when applied to the analysis of real samples containing CIP. In addition to its sensing capabilities, the hybrid system was effectively utilized as a fluorescent ink, offering advanced anti-counterfeiting solutions and bolstering information security. This study highlights the substantial potential of NCQD-based hybrid materials in diverse sensing applications and their implications for practical innovations.

Investigation of the usability of Ce- and N-doped hybrid carbon quantum dots for the removal of neodymium ions

Investigation of the usability of Ce- and N-doped hybrid carbon quantum dots for the removal of neodymium ions

Polarized Superradiance from CsPbBr3 Quantum Dot Superlattice with Controlled Interdot Electronic Coupling.

Cooperative emission of photons from an ensemble of quantum dots (QDs) as superradiance can arise from the electronically coupled QDs with a coherent emitting excited state. This contrasts with superfluorescence (Dicke superradiance), where the cooperative photon emission requires a buildup of coherence in an ensemble of incoherently excited QDs via their coupling to a common radiation mode. In perovskite QDs, superradiance has been rarely observed, unlike superfluorescence, due to the challenge in QD electronic coupling. Here, we report superradiance with a very narrow linewidth (<5 meV) and a large redshift (∼200 meV) from the strongly coupled CsPbBr3 QD superlattice achieved through the combination of quantum confinement and ligand engineering. The superradiance is polarized in contrast to the uncoupled exciton emission from the same superlattice, indicating anisotropic electronic coupling in superlattices. This finding suggests the potential of a perovskite QD superlattice with structurally controllable interdot coupling as the polarized cooperative photon emitters.