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Environmentally friendly approach to the synthesis of monodisperse and bright blue emitting Cd0.15Zn0.85S quantum dots
摘要： Nucleation and growth of quantum dots (QDs) in solution are mainly controlled by the kinetic and thermal modes of the reaction process. By influencing any of them, the properties of the final nanocrystals can be tuned. The influences of temperature and chemical nature of starting materials on nucleation and, as a consequence, on the structure and optical properties of Cd0.15Zn0.85S QDs have been systematically investigated by one-pot and hot-injection methods. All reactions were performed in organic disperse medium using N,N′-disubstituted and N,N′,N′-trisubstituted thioureas (TU) as a new sources of sulfur. In addition to environmental friendliness, each of them has a number of unique chemical properties. The effect of the substituents’ nature in thioureas on the morphology, size and optical properties of synthesized QDs has been studied. The strong correlation between the metal ratios taken to the reaction and elemental analysis (EDS) results for all obtained Cd0.15Zn0.85S QDs was found. However, prepared nanomaterials have different size (2.9 – 4.6 nm) and morphology. The optical features have also changed under the various thermal conditions. Especially, the changes in the photoluminescence spectra of QDs synthesized with different thioureas are noticeable. Highly photoluminescent (photoluminescence quantum yield PL QY up to 67 %), morphologically and structurally homogeneous blue-emitting Cd0.15Zn0.85S QDs were obtained.
关键词： semiconductors,quantum dots,substituted thioureas
更新于2025-09-11 14:15:04
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Fabrication of a Tyrosine Responsive Liquid Quantum dots based Biosensor Through Host-Guest Chemistry
摘要： Design and fabrication of a smart liquid quantum dots (LQDs) with high biomolecules selectivity and specificity remains a challenge. Herein, a multifunctional calix[4]arene derivatives (PCAD) was rationally designed and applied to fabricate a Tyr-responsive CdSe-LQDs system through host-guest chemistry. Such this biosensor displays an outstanding fluorescence/macroscopic response for Tyr and reversible fluidic features due to the hydrogen interaction between the PCAD of CdSe-LQDs and Tyr. These excellent results highlighted CdSe-LQDs as a promising platform for biological molecules recognition and separation in the future.
关键词： Calix[4]arene,Liquid Quantum dots,Biosensor,Host-Guest Chemistry,Tyrosine detection
更新于2025-09-11 14:15:04
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Photoluminescence Decay of Colloidal Quantum Dots: Reversible Trapping and the Nature of the Relevant Trap States
摘要： Interfaces are crucial factors in shaping the properties of colloidal quantum dots (QDs), in particular the size-dependent optical properties that are a hallmark of these materials. However, the role played by the interfaces associated with QDs on the kinetics of photoluminescence (PL) decay of these nanocrystals is not fully understood even for the most extensively investigated II-VI QDs. In particular, interfaces are a hotbed of trapping sites over which control is essential for efficient performance of QD-based devices, because traps condition PL lifetimes and may be related to PL intermittency. In this work, we analyze the room-temperature PL decay of drop-cast films of CdSe/ZnS QDs varying a number of factors (casting solvent, capping ligands, core/shell interface character). We show how the use of a function that accounts for reversible trapping of photogenerated charge carriers with physically meaningful parameters (time constant, trapping and detrapping rate constants, and average number of traps per QD) can provide valuable information concerning the relevant interfaces, and therefore the nature of the trap states, involved in the recombination of those charge carriers. This approach should be applicable to QDs of a variety of compositions as well as materials beyond inorganic semiconductors.
关键词： photoluminescence decay,trap states,reversible trapping,CdSe/ZnS QDs,colloidal quantum dots
更新于2025-09-11 14:15:04
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An efficient cadmium free inverted red quantum dot light emitting diodes
摘要： Here, we report an efficient inverted red indium phosphide (InP) comprised QD (InP/ZnSe/ZnS, core/shell structure) light-emitting diode (QLED) by modulating an interfacial contact between the electron transport layer and emissive InP-QDs and applying self-aging approach. The red InP-QLED with optimized interfacial contact exhibits a significant improvement in maximum external quantum efficiency and current efficiency from 4.42% to 10.2% and 4.70 cd/A to 10.8 cd/A, respectively, after 69 days of self-aging, which is an almost 2.3-fold improvement compared with the fresh device. The analysis indicates the consecutive reduction in electron injection and accumulation in the emissive QD due to changes in the conduction band minimum of ZnMgO (0.1 eV after 10 days of storage times) through a downward vacuum level shift according to the aging times. During the device aging periods, the oxygen vacancies of ZnMgO reduces, which leads to lower the conductivity of ZnMgO. As a result, the improvement of charge balance in the device with the suppression of exciton quenching at the interface of ZnMgO and InP-QD.
关键词： Cadmium-free quantum dots,charge balance,charge carrier injection layers,inverted structure,light emitting diode
更新于2025-09-11 14:15:04
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Photodetecting Heterostructures from Graphene and Encapsulated Colloidal Quantum Dot Films
摘要： Heterostructure devices consisting of graphene and colloidal quantum dots (QDs) have been remarkably successful as photodetectors and have opened the door to technological applications based on the combination of these low-dimensional materials. This work explores the photodetection properties of a heterostructure consisting of a graphene field effect transistor covered by a film of silica-encapsulated colloidal QDs. Defects at the surface of the silica shell trap optically excited charge carriers, which simultaneously enables photodetection via two mechanisms: photogating, resulting in a net p-doping of the device, and Coulombic scattering of charge carriers in the graphene, producing an overall decrease in the current magnitude.
关键词： heterostructures,photogating,graphene,Coulombic scattering,colloidal quantum dots,photodetectors
更新于2025-09-11 14:15:04
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Graphene quantum dot vertical cavity surface emitting lasers
摘要： Nonzero-bandgap graphene quantum dots (GQDs) are novel optical gain materials promising for solution-processed light sources with high cost efficiency and device performance. To date, there have only been a few reports on the realization of GQDs-based lasers. Herein, we demonstrate for the first time room-temperature lasing emission with green gamut from GQDs in a vertical optical cavity composed of Ta2O5/SiO2 dielectric distributed Bragg reflectors (DBRs). The lasing is enabled by the unique design of the DBR which not only provides a wide stopband spectrally overlapping with the emission of the GQDs but also allows high transmittance of optical excitation in the UV-light region. This demonstration is a clear evidence of the use of GQDs as optical gain materials and represents an important step forward toward their potential applications in wide-gamut laser displays and projectors.
关键词： Vertical Cavity Surface Emitting Laser,Graphene Quantum Dots,Green Gap,Microwave-Assisted Hydrothermal Method,Distributed Bragg Reflectors (DBRs)
更新于2025-09-11 14:15:04
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Manufacturing of Volumetric Glass <b>-</b> Based Composites with Single- and Double-QD Doping
摘要： Quantum dot (QD)-based light-emitting materials are gaining increased attention because of their easily tunable optical properties desired for various applications in biology, optoelectronics, and photonics. However, few methods can be used to manufacture volumetric materials doped with more than one type of QD other than QD-polymer hybrids, and they often require complicated preparation processes and are prone to luminescence quenching by QD aggregation and separation from the matrix. Here, simultaneous doping of a volumetric glass-based nanocomposite with two types of QDs is demonstrated for the first time in a single-step process using the nanoparticle direct doping method. Glass rods doped with CdTe, CdSe/ZnS, or co-doped with both QDs, are obtained. Photoluminescence and lifetime experiments confirm temperature-dependent double emission with maxima at 596 and 720 nm with mean lifetimes up to 16 ns, as well as radiative energy transfer from the short wavelength–emitting QDs to the long wavelength–emitting QDs. This approach may enable the simple and cost-efficient manufacturing of bulk materials that produce multicolor luminescence with cascade excitation pumping. Applications that could benefit from this include broadband optical fiber amplifiers, backlight systems in LCD screens, high-power LEDs, or down-converting solar concentrators used to increase the efficiency of solar panels.
关键词： energy transfer,nanoparticle direct doping,quantum dots,volumetric material with embedded quantum dots,double wavelength luminescence
更新于2025-09-10 09:29:36
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Highly enhanced solar conversion efficiency of novel layer-by-layer PbS:Hg and CdS quantum dots-sensitized ZnO thin films prepared by sol–gel spin coating
摘要： Owing to superior optical properties, ZnO thin ?lms have immense potential in solar cell preparation. ZnO thin ?lms were prepared by sol–gel technology. However, this is prolonged technique and it necessitates a complex precursor solution. In the present work, ZnO thin ?lms are prepared by sol–gel spin coating with simple precursor, zinc acetate. A very remarkable feature of the method is that polycrystalline, non-abrasive and translucent ?lms were obtained. Additionally, novel PbS:Hg quantum dots (QDs) and CdS QDs are successfully synthesized. Moreover, both types of QDs are deposited layer-by-layer over pure ZnO and Ag:ZnO thin ?lms. The ?lms are characterized by X-ray diffraction, and crystallinity continuation is observed even after the addition of QDs layer. Presence of synthesized QDs over thin ?lms is also con?rmed. The ?lms were also characterized by scanning electron microscopy (SEM) and UV–Vis spectroscopy. Uniform, dense and porous surface morphology is clearly revealed. Sensitized thin ?lms show a huge decline in band gap and large enhancement in ef?ciency. Superior current density (10.87 mA cm?2) is achieved with PbS:Hg/CdS/Ag:ZnO, which leads to enhancement in overall solar conversion ef?ciency by 6.34 times.
关键词： PbS:Hg quantum dots,sol–gel,Ag:ZnO ?lm,CdS quantum dots
更新于2025-09-10 09:29:36
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A fast quantum interface between different spin qubit encodings
摘要： Single-spin qubits in semiconductor quantum dots hold promise for universal quantum computation with demonstrations of a high single-qubit gate fidelity above 99.9% and two-qubit gates in conjunction with a long coherence time. However, initialization and readout of a qubit is orders of magnitude slower than control, which is detrimental for implementing measurement-based protocols such as error-correcting codes. In contrast, a singlet-triplet qubit, encoded in a two-spin subspace, has the virtue of fast readout with high fidelity. Here, we present a hybrid system which benefits from the different advantages of these two distinct spin-qubit implementations. A quantum interface between the two codes is realized by electrically tunable inter-qubit exchange coupling. We demonstrate a controlled-phase gate that acts within 5.5 ns, much faster than the measured dephasing time of 211 ns. The presented hybrid architecture will be useful to settle remaining key problems with building scalable spin-based quantum computers.
关键词： spin qubits,quantum computation,controlled-phase gate,semiconductor quantum dots,singlet-triplet qubit
更新于2025-09-10 09:29:36
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Multidimensional Coherent Spectroscopy of Semiconductors
摘要： Optical multidimensional coherent spectroscopy (MDCS) is a nonlinear spectroscopy technique where a material is excited by a series of laser pulses to produce a spectrum as a function of multiple frequencies. The technique’s ability to elucidate excited-state structure and interactions has made MDCS a valuable tool in the study of excitons in semiconductors. This review introduces the method and describes progress it has fostered establishing a better understanding of dephasing rates, coherent coupling mechanisms, and many-body interactions pertaining to optically generated electronic excitations in a variety of semiconductor material systems. Emphasis is placed on nanostructured gallium arsenide quantum wells and quantum dots, on quantum dots in other III–V and II–VI semiconductors, and on atomically thin transition metal dichalcogenides. Recent technical advances and potential future directions in the ?eld are also discussed.
关键词： quantum dots,excitons,quantum wells,Fourier-transform spectroscopy,transition metal dichalcogenides
更新于2025-09-10 09:29:36