Quantum Dot Hybrid Research Articles

Charge carrier analysis via impedance spectroscopy and the achievement of high performance in CdSe/ZnS:di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane hybrid quantum dot light-emitting diodes

Despite the importance of charge carrier injection balance for achieving high performance with quantum dot light-emitting diodes (QLEDs), there have been comparatively few relevant studies. Thus, we extensively analyzed charge carrier behaviors of QLEDs using an impedance spectroscopy (IS) method and a QLED-equivalent circuit. This yielded both the capacitive and resistive values of each of the emission layer (EML) and the charge transport layer (CTL), revealing the relationships between these values and device performance. Using this analysis method, we examined the effects of the combination of hybrid quantum dot (QD) EMLs and CTLs on QLED performance. The CdSe/ZnS QD and di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane blended hybrid QD EML, in combination with the di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane hole transport layer, produced electron–hole balance in EMLs and resulted in a remarkable improvement in device performance. The maximum current efficiency of a green QLED using this combination was 43.7 cd/A, which was approximately two-fold greater than the maximum current efficiency of a QLED with a conventional CdSe/ZnS QD EML and much better than previously reported values for green QLEDs with CdSe/ZnS-based EMLs. In summary, we have greatly improved QLED performance via charge balance optimization. Herein, we present the methods for this improvement, along with an analysis of carrier behavior. • A CdSe/ZnS and TAPC hybrid layer improved light emission efficiency 1.9 times. • Hybrid emission layer and TAPC hole transport layer combination was the most efficient. • Energy band levels of the hybrid light emission layer could be controlled. • Capacitance and resistance of each layer were extracted by Impedance spectroscopy. • The device operation mechanism was well explained by the impedance spectroscopy.

Dual-Emission ZAISe/ZnS quantum dots for Multi-level Bio-Imaging: Foam cells and atherosclerotic plaque imaging

In vitro or in vivo fluorescence imaging based on quantum dots (QDs) has shown promise for the noninvasive diagnosis of atherosclerosis. However, simultaneous in vitro and in vivo imaging remains challenging due to the limitation of the current synthesis method of dual-emission QDs (dual-emitting hybrid QDs, and broad-spectrum emitting QDs). Herein, we fabricate a dual-emission (visible region and near-infrared region emission) QDs (ZAISe/ZnS) via the “bottom to up” method of a quaternary inorganic compound for the foam cells and atherosclerosis plaque imaging simultaneously without the intricate size modulation and the strict optical filter requirements. The oil-soluble ZAISe/ZnS is further encapsulated with bovine serum albumin (BSA) to realize phase transfer and ultimately possess the inflammation-targeting properties via biomimetic treatment with MMV (macrophage-derived micro-vesicle). The results first indicate that the as-constructed ZAISe/ZnS@BSA@MMV could accurately locate the foam cells and conduct long-term imaging of the atherosclerotic plaque, which provides a new strategy for the early and noninvasive diagnosis of atherosclerosis.

Smart epoxy/polyurethane/carbon quantum dots hybrid coatings: Synthesis and study of UV-shielding, viscoelastic, and anti-corrosive properties

ABSTRACT This project was performed to synthesize and investigate the properties of the smart hybrid coatings based on epoxy/polyurethane (EP/PU) reinforced with carbon quantum dots (CQDs) with multipurpose applications. To do this, flexible and transparent polymer coatings were prepared by mixing epoxy resin and PU pre-polymer. Strengthening of hybrid coatings by CQDs (1–3 wt%) led to preparing fluorescent coatings with high protection against UV rays (85–98%), and improved tensile strength, flexibility (10–35%), and viscoelastic properties such as storage modulus and Tg. Findings of salt spray test approved that increased CQDs concentration in the coatings resulted in improved anti-corrosive behavior.

Unified formulations for RKKY interaction, side Kondo behavior, and Fano antiresonance in a hybrid tripartite quantum dot device with filtered density of states

Hybrid quantum dot structures are potential building blocks for spintronic devices and quantum logic gates, within which the understanding of many-body correlations is a prerequisite for implementing quantum information processing and generating controlled entanglement. Herein, we consider a hybrid tripartite quantum dot device, one of which is embedded directly between the source and drain electrodes, while the other two dots are side coupled to the first one. Modeling the system using the three-impurity Anderson model, we concentrate on the Ruderman-Kittel-Kasuya-Yosida interaction, the suppression of the Kondo behavior in the side dots, the destructive quantum interference, the gate-controlled quantum phase transitions, the Dicke effect, the ferromagnetic Kondo effect, and the thermodynamical properties in various parameter regimes using the numerical renormalization group method. Unified formulations are established, which are associated with the effective width of the zero-energy peak of the central dot without side dots, the central-side exchange coupling, as well the on-site electron-electron repulsion. We demonstrate that these formulas are well suitable for the non-, weak-, and strong-interacting cases.

Brominated Polythiophene Reduces the Efficiency‐Stability‐Cost Gap of Organic and Quantum Dot Hybrid Solar Cells

AbstractThe emerging solution‐processed solar cells have attracted worldwide effort in the last decade. Developing efficient, stable, and cost‐effective solar cells is strongly desirable in countering the growing global warming. Nevertheless, the photovoltaic performance and stability of hybrid solar cells based on low‐cost polythiophenes are far from satisfactory, due to their high‐lying energy levels and excessive aggregation. Herein, it is shown that brominated polythiophene (P3HT‐Br), prepared via a facile two‐step approach can effectively facilitate charge transport and suppress recombination in quantum dot (QD)/organic heterojunctions. Accordingly, the power conversion efficiency of the optimized hybrid polythiophene/QD cell is boosted from 8.7% to 11% (a 26% increase) with markedly reduced energy loss. More strikingly, the device achieves record‐high thermal stability with a lifetime of over 400 h maintaining 80% of the initial performance. Both device efficiency and stability are the best reported for polythiophene/QD hybrid solar cells. Moving forward, brominated polythiophenes hold great application in perovskite solar cells with significantly improved performance and offer new opportunities for other emerging solar cells.

Fabrication of nitrogen-doped graphene quantum dots hybrid membranes and its sorption for Cu(II), Co(II) and Pb(II) in mixed polymetallic solution

With the rapid development of new–energy batteries, heavy-metals pollution from spent batteries has drawn much attention. Various techniques are recently proposed to delete or eliminate such pollution. Among which, membrane sorption exhibits exceptional advantages for the separation of multi-metal solution. For such a purpose, nitrogen-doped graphene quantum dots (N-GQDs) hybrid membranes were fabricated via sol–gel technique and hydrothermal synthesis, in which the precursor powder of N-GQDs was obtained by the combination of urea (used as a nitrogen source) and citric acid (used as a carbon source). Subsequently, the N-GQDs precursor was mixed with silane and PVA to generate N-GQDs hybrid membranes (NHMs). Competitive sorption of Cu(II), Co(II) and Pb(II) in the mixed polymetallic solution, such as a mixed Cu(II), Co(II) and Pb(II) ternary solution, a mixed Cu(II), Pb(II), Ca(II), Co(II) and Cr(III) quintuple solution, was investigated. It indicated that Cu(II) sorption on NHMs had better selectivity in these mixed polymetallic solutions. Moreover, sorption mechanism of Cu(II), Co(II) and Pb(II) demonstrates that the sorption of NHMs for Cu(II) and Pb(II) abided by Elovich model, indicating the properties of heterogeneous chemisorption. Such a trend shows that the sorption via chemical process between the active sites on the top-layer of NHMs, and Cu(II) and Pb(II) is one of the dominant interfering factors. Desorption testing demonstrated that EDTA-2Na is a best de-sorbent for Cu(II) sorption on NHMs and the number of cycles of these membranes can reach up to 10 times. These findings suggest that NHMs can be used to adsorb Cu(II), Co(II) and Pb(II) from mixed polymetallic solution, indicating promising applications in the successive separation of wastewater containing multiple mixed toxic metals from spent new-energy batteries and other metal-containing wastewater.

Blue Light Emitting Diodes based on Bright Quasi‐Type‐II ZnO@1‐Aminopyrene Hybrid Quantum Dots with a Long Operation Life

AbstractNon‐toxic heavy metal, low‐cost indium‐free blue emissive quantum dots (QDs) are critical for the realization of self‐emissive electroluminescent quantum dot (ELQD) light‐emitting diode (LED) displays. A facile and effective hybridization of ZnO QDs with functionalized polyaromatic hydrocarbons (f‐PAHs) to synthesize a very bright and stable blue‐light emissive quantum‐dot LED (QLED) using non‐toxic quasi‐type‐II ZnO@1‐Aminopyrene hybrid QDs is reported. The optimized QLEDs of ITO/PEDOT:PSS/TFB/ZnO@1‐Aminopyrene/TPBi/LiF/Al demonstrate very bright deep blue‐light electroluminescence of 3379 cd m−2 centered at λ = 441 nm with a full‐width‐at‐half maximum of 41.7 nm and CIE 1931 color coordinates of 0.17 and 0.09, a luminous efficacy of 3.32 cd A−1, power efficiency of 2.45 lm W−1, external quantum efficiency of 2.35%, and a remarkably long lifetime T50 of >17 830 h at 100 cd m−2.

Nanodiamond islands confined between two graphene sheets as perspective 2D quantum materials

Based on direct space DFT PBE0/6-31G* electronic structure calculations, the structure and properties of nanodiamond islands confined between two finite graphene fragments (NDI-c2G) was proposed and theoretically explored. DFT simulations revealed that fusion of planar aromatic molecules with two parent graphene fragments may form either cubic or hexagonal allotropes of NDI-c2Gs lattices accompanied with formation of local corrugated sp3 sites with substituted dangling bonds embedded into graphene sublattices. It was shown that at the DFT level of theory, low distortion energies of NDI-c2Gs lattices are comparable or smaller than the energy of van-der-Waals interactions, which allows the NDI-c2G lattices to be stabilized by a support and finally synthesized. The Nuclear Independent Chemical Shift calculations, shows that in the vicinity of NDI regions, graphene lattices are estimated to be either low-, or anti-aromatic. Furthermore, the formation of NDI-c2Gs leads to localization of HOMO and LUMO states at different sites of the NDI-c2Gs lattices. The NDI-c2G regions with confined frontier orbitals can be considered as arrays of quantum dots isolated from each other by NDI scattering centres of 3.82 Å dimension. The results demonstrates that NDI-c2G should be considered as strongly-correlated entangled hybrid quantum dots which may form extended quantum ensembles with great potential for advanced quantum applications.

Photothermal/NO combination therapy from plasmonic hybrid nanotherapeutics against breast cancer.

In this study, a plasmon-semiconductor nanotheranostic system comprising Au nanostars/graphene quantum dots (AuS/QD) hybrid nanoparticles loaded with BNN6 and surface modified with PEG-pyrene was developed for the photo-triggered hyperthermia effect and NO production as the dual modality treatment against orthotopic triple-negative breast cancer. The structure and morphology of the hybrid nanodevice was characterized and the NIR-II induced thermal response and NO production was determined. The hybrid nanodevice has shown enhanced plasmonic energy transfer from localized surface plasmonic resonance of Au nanostars to QD semiconductor that activates the BNN6 species loaded on QD surfaces, leading to the effective NO production and the gas therapy in addition to the photothermal response. The increased accumulation of the NIR-II-responsive hybrid nanotheranostic in tumor via the enhanced permeation and retention effects was confirmed by both in vivo fluorescence and photoacoustic imaging. The prominent therapeutic efficacy of the photothermal/NO combination therapy from the BNN6-loaded AuS@QD nanodevice with the NIR-II laser irradiation at 1064nm against 4T1 breast cancer was observed both in vitro and in vivo. The NO therapy for the cancer treatment was evidenced with the increased cellular nitrosative and oxidative stress, nitration of tyrosine residues of mitochondrial proteins, vessel eradication and cell apoptosis. The efficacy of the photothermal treatment was corroborated directly by severe tissue thermal ablation and tumor growth inhibition. The NIR-II triggered thermal/NO combination therapy along with the photoacoustic imaging-guided therapeutic accumulation in tumor shows prominent effect to fully inhibit tumor growth and validates the promising strategy developed in this study.

One-step ultrafast laser induced synthesis of strongly coupled 1T-2H MoS2/N-rGO quantum-dot heterostructures for enhanced hydrogen evolution

Strongly coupled transition-metal dichalcogenides/carbon hybrids are cost-effective and robust electrocatalysts for hydrogen evolution reaction, and further designing quantum-dot structures of hybrid catalysts often maximizes the accessible active sites and facilitates charge transfer and consequently their catalytic performance. However, the rational design and facile synthesis of such quantum-dot hybrid still remains a central challenge. Herein, an effective and controllable strategy is presented for one-step synthesis of strongly coupled 1T-2H MoS2/N-rGO quantum-dot heterostructures using spatially shaped laser ablation in liquid (LAL). The yield of QDs reaches 75.16 wt%, indicating that the mass production of such QDs is feasible using LAL method. Moreover, both characterizations and density functional theory calculations reveal that the much enhanced electrochemical HER performance arises from the optimized chemical composition, improved conductivity, and strongly coupled structural/electronic features. Correspondingly, the as-formed quantum-dot heterostructures exhibit remarkably low overpotential of 97 mV at 10 mA c2, a small Tafel slope of 39 mV dec-1 and high durability, outperformed most previously reported QDs-based electrocatalysts. This versatile strategy overcomes the current limitations of strong-coupled quantum-dot heterostructures materials preparing and offers a synergistic modulation approach for designing highly active HER catalysts viable for practical application.

Novel Dual-Signal Electrochemiluminescence Aptasensor Involving the Resonance Energy Transform System for Kanamycin Detection.

Based on luminol-capped Pt-tipped Au bimetallic nanorods (NRs) (L-Au-Pt NRs) as the anode emitter and SnS2 quantum dots (QDs) hybrid Eu metal organic frameworks (MOFs) (SnS2 QDs@Eu MOFs) as the cathode emitter, a dual-signal electrochemiluminescence (ECL) platform was designed for the ultrasensitive and highly selective detection of kanamycin (KAN). Using a dual-signal output mode, the ratiometric ECL aptasensor largely eliminates false-positives or false-negatives by self-calibration in the KAN assay process. To stimulate the resonance energy transform (RET) system, the KAN aptamer and complementary DNA are introduced for conjugation between the donor and acceptor. With the specific recognition of target KAN by its aptamer, L-Au-Pt NRs-apt partially peels off from the electrode surface. Eventually, the RET system is removed, leading to an increasing cathode signal and a decreasing anode signal. In view of this phenomenon, the ratiometric aptasensor can quantify KAN from 1 pM to 10 nM with a low detection limit of 0.32 pM. This dual-signal ECL aptasensor exhibits great practical potential in environmental monitoring and food safety.

Novel Electrochemical Sensor for the Determination of Bisphenol A Using a Molybdenum(IV) Sulfide Quantum Dots Polysodium Styrene Sulfonate Functionalized Reduced Graphene Oxide Modified Glassy Carbon Electrode (GCE) by Differential Pulse Voltammetry (DPV)

A sensitive electrochemical platform for the determination of bisphenol A (BPA) was constructed. A hybrid of MoS2 quantum dots decorated poly sodium styrene sulfonate functionalized reduced graphene oxide (MoS2 QDS@PSS-rGO) was prepared by a simple method. The hybrid was cast on a bare glassy carbon electrode (GCE) to form the MoS2 QDs@PSS-rGO/GCE. The electrochemical response of BPA on the MoS2 QDs@PSS-rGO/GCE was significantly enhanced compared to the unmodified electrode, indicating that the nanocomposite possessed an electrocatalytic effect. A novel method was established to determine BPA with a detection limit of 0.008 μM. The applicability of the prepared sensor was demonstrated to determine BPA in real samples with high recoveries.

An Aggregation-Suppressed Polymer Blending Strategy Enables High-Performance Organic and Quantum Dot Hybrid Solar Cells.

Solution-processing hybrid solar cells with organics and colloidal quantum dots (CQDs) have drawn substantial attention in the past decade. Nevertheless, hybrid solar cells based on the recently developed directly synthesized CQD inks are still unexplored. Herein, a facile polymer blending strategy is put forward to enable directly synthesized CQD/polymer hybrid solar cells with a champion efficiency of 13%, taking advantage of the conjugated polymer blends with finely optimized aggregation behaviors. The spectroscopic and electrical investigations on carrier transport and recombination indicate that polymer blends can endow fast carrier transport and less recombination over the single counterparts. Moreover, the blending strategy offers a "dilution effect" for top-notch photovoltaic polymers with excessively strong aggregation tendency, resulting in moderate feature domain size and surface roughness, which afford fast hole transport and therefore high photovoltaic performance. The effectiveness of this strategy is successfully validated using two pairs of photovoltaic polymers. Accordingly, the relationships between polymer morphology, carrier transport, and photovoltaic performance are established to advance the progress of CQD/polymer hybrid solar cells. Such progress stresses that the utilization of aggregation-suppressed polymer blends is a facile approach toward the fabrication of high-efficiency organic-inorganic hybrid solar cells.

Spin-thermoelectric effects in a quantum dot hybrid system with magnetic insulator

We investigate spin thermoelectric properties of a hybrid system consisting of a single-level quantum dot attached to magnetic insulator and metal electrodes. Magnetic insulator is assumed to be of ferromagnetic type and is a source of magnons, whereas metallic lead is reservoir of electrons. The temperature gradient set between the magnetic insulator and metallic electrodes induces the spin current flowing through the system. The generated spin current of magnonic (electric) type is converted to electric (magnonic) spin current by means of quantum dot. Expanding spin and heat currents flowing through the system, up to linear order, we introduce basic spin thermoelectric coefficients including spin conductance, spin Seebeck and spin Peltier coefficients and heat conductance. We analyse the spin thermoelectric properties of the system in two cases: in the large ondot Coulomb repulsion limit and when these interactions are finite.

Fluorescent sensitized irradiation sensing and recording hybrid quantum dot embedded polymer nanocomposites

This paper presents the preparation and characterisation studies of UV sensing films with a simple mathematical model for quantifying the lower UV irradiation duration/doses. To observe any appreciable changes in any properties of Poly-vinyl alcohol (PVA) films with UV irradiation, it has to be treated for few hours/days together. However, the technique presented here is an ultrasensitive method in which, the quantum dots (QDs) reinforced PVA film has become sensitive to UV radiations even for few seconds of exposure. To achieve this, Mercaptopropionic acid (MPA) capped CdTe QDs with superior fluorescence spectral properties grown in water medium were dispersed in PVA matrix to prepare QD-Polymer nanocomposites. Such fluorescence enriched films were stored in room temperature in ordinary environmental conditions for four years to check the degradability and viability. The stability of fluorescence and electrical properties of QDs inside PVA matrix was remarkable in this test period and were retained by the films even after such long duration. After that they were treated with UV radiation with the interval of few seconds to check the exposure recording ability of such films. The results are very promising in terms of sensitivity and the recording ability. Using the least square linear fit method a mathematical model was developed which would be useful in UV exposure sensing for smaller duration. This study also helps the concerned industries who would prepare film sensors for UV exposure quantification (like Litmus paper for pH sensing).

Near-infrared switching between slow and fast light in the metal nanoparticles-graphene nanodisks-quantum dots hybrid systems

Graphene-based nanocomposites have recently attracted much interest due to the unique properties of graphene plasmons paving the way to promising potential applications. We study the near-infrared linear optical properties of the metal nanoparticle-graphene nanodisk- quantum dot hybrid system by numerically solving the equation of motion for the density matrix elements that describe the dynamics of the system where the quantum dot is modeled as a three-level atomic system of Λ configuration interacting with a weak probe field and strong control field. We obtain a strong switching between slow and fast light near resonance can be controlled by the distances between the components of the system, the size of metal nanoparticle as well as the Rabi frequency of the control field. Moreover, the proposed hybrid plasmonic system shows a significant amplification without population inversion can be effectively monitored by strength of the control field. Thus, we think that the metal nanoparticle-graphene nanodisk- quantum dot hybrid system has potential applications in communication, sensing, imaging, signal processing and optoelectronics devices.

0D/3D direct Z-scheme heterojunctions hybridizing by MoS2 quantum dots and honeycomb conjugated triazine polymers (CTPs) for enhanced photocatalytic performance

Herein, a novel direct Z-scheme photocatalyst was accomplished by hybridization of 0D MoS2 quantum dots (MSQDs) and 3D honeycomb-like conjugated triazine polymers (CTP) (namely, CTP-MSQD). The unique 0D/3D hierarchical structure significantly enhanced the exposure of active sites and light harvesting property, while the formed p-n junction enabled the direct strong interface coupling without the necessity of any mediators. The optimized CTP-MSQD3 exhibited continuously increased visible-light-driven photocatalytic activity and strong durability both in Cr(VI) reduction and H2 evolution, featured a rate of 0.069 min−1 and 1070 µmol/(hr∙g), respectively, which were 8 times than those of pure 3D-CTP (0.009 min−1 and 129 µmol/(hr∙g)). We believe that this work provides a promising photocatalyst system that combines a 0D/3D hierarchical structure and a Z-scheme charge flow for efficient and stable photocatalytic conversion.

Mn3O4/graphene quantum dots hybrid nanoparticles for enhanced oxygen reduction reaction in alkaline media

Mn3O4/graphene quantum dots hybrid nanoparticles for enhanced oxygen reduction reaction in alkaline media

Efficient narrowband red electroluminescence from a thermally activated delayed fluorescence polymer and quantum dot hybrid

Multiresonant effect is believed to be a promising molecular design rule to solve the bottleneck of wideband electroluminescence (EL) for thermally activated delayed fluorescence (TADF) materials. However, the realization of narrowband red EL still remains a big challenge due to the limited intramolecular charge transfer. Here, a hybrid emitting layer (EML) composed of a TADF polymer and red quantum dots (R-QDs) has been proposed for narrowband EL in red region. Such a hybrid EML can ensure efficient Förster resonance energy transfer and charge trapping to some degree, improve photoluminescent quantum yields, harvest the generated triplet excitons, and favor hole injection/transporting to simply device structure free of hole-transporting layer. As a consequence, the wideband TADF with a full-width at half-maximum (FWHM) of 87 nm is successfully converted to a narrowband red emission with a FWHM of 29 nm. Also, the corresponding device achieves a state-of-art external quantum efficiency as high as 14.9% (16.7 cd A-1, 16.3 lm W-1) together with Commission Internationale de l’Eclairage coordinates of (0.67, 0.32). The results clearly indicate the great potential of the hybrid EML for narrowband red EL.

Assessing the electrocatalytic activity of a localized push-pull system in cobalt phthalocyanine/graphene quantum dot hybrids

In this study, two cobalt phthalocyanines (asymmetric complex 1) and symmetric (complex 2) were synthesized and conjugated to nitrogen-doped graphene quantum dots (NGQDs) through covalent and non-covalent means to create Co phthalocyanine (CoPc)-NGQDs hybrid systems. The CoPcs and conjugates were applied as electrode modifiers on a glassy carbon electrode in the electrochemical sensing of nitrite. Of the CoPcs alone, complex 1 performed better than complex 2 regarding the limits of detection (LoD) recorded (5.74 μM for 1 and 15.1 μM for 2). Regarding the conjugates/nanocomposites, the π-π stacked conjugate derived from complex 2 (2πNGQDs) demonstrated highly favourable electrochemical potential with an LoD value of 0.70 μM. The nanocomposites fashioned from complex 1 were marred by a reduced loading which rendered the conjugates poor electrochemical sensors. These observations however do not disqualify GQDs as complementary nanomaterials to phthalocyanines but rather shed light on seeking alternative routes to increasing the Pc loading in conjugates (more so in π-π stacked conjugates).