- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- 2016
- minimum time
- quantum evolution
- un‐ certainty relations
- quantum control
- merit figures
- negative voltage current differential resistance
- characteristics
- heterojunction
- quantum well
- resonant tunneling border
- Optoelectronic Information Science and Engineering
- Quantum Information Science
- V.N. Karazin Kharkiv National University
- ShanghaiTech University
- S?o Paulo University
- Universidad Veracruzana
-
From colloidal CdSe quantum dots to microscale optically anisotropic supercrystals through bottom-up self-assembly
摘要： The development of fabrication techniques for novel nanostructured materials is one of the key tasks of modern materials science. One pathway to successfully complete this task is the bottom-up assembly of colloidal nanoparticles into ordered superstructures, possessing both the properties of individual nanoparticles and further novel properties resulting from their interactions. However, nanoparticle self-assembly depends on a variety of parameters, which makes the precise control of this process a complicated problem. Here, the time course of quantum dot (QD) self-assembly into ordered superstructures has been analyzed, along with the evolution of their morphological and optical properties. QD self-assembly occurs through two distinct stages (homo- and hetero-geneous), leading to the formation of supercrystals with a layered morphology. Analysis of the optical properties throughout the superstructures’ growth has shown that the absorption and photoluminescence (PL) bands are blue shifted, retaining almost the same PL lifetimes as in the initial QD solution. The supercrystals formed possess a further unique optical property caused by their layered morphology; namely, a four-fold symmetry characterized by strong birefringence. Such supercrystals may be used for the fabrication of microscale optical paths with high extinction coefficients and specific polarization properties for novel optoelectronic devices.
关键词： optical anisotropy,nanostructured materials,birefringence,self-assembly,quantum dots,supercrystals
更新于2025-11-21 11:08:12
-
Hydrophilic Quantum Dots Functionalized with Gd(III)-DO3A Monoamide Chelates as Bright and Effective T1-weighted Bimodal Nanoprobes
摘要： Magnetic resonance imaging (MRI) is a powerful non-invasive diagnostic tool that enables distinguishing healthy from pathological tissues, with high anatomical detail. Nevertheless, MRI is quite limited in the investigation of molecular/cellular biochemical events, which can be reached by fluorescence-based techniques. Thus, we developed bimodal nanosystems consisting in hydrophilic quantum dots (QDs) directly conjugated to Gd(III)-DO3A monoamide chelates, a Gd(III)-DOTA derivative, allowing for the combination of the advantages of both MRI and fluorescence-based tools. These nanoparticulate systems can also improve MRI contrast, by increasing the local concentration of paramagnetic chelates. transmetallation assays, optical characterization, and relaxometric analyses, showed that the developed bimodal nanoprobes have great chemical stability, bright fluorescence, and high relaxivities. Moreover, fluorescence correlation spectroscopy (FCS) analysis allowed us to distinguish nanosystems containing different amounts of chelates/QD. Also, inductively coupled plasma optical emission spectrometry (ICP – OES) indicated a conjugation yield higher than 75%. Our nanosystems showed effective longitudinal relaxivities per QD and per paramagnetic ion, at least 5 times [per Gd(III)] and 100 times (per QD) higher than the r1 for Gd(III)-DOTA chelates, suitable for T1-weighted imaging. Additionally, the bimodal nanoparticles presented negligible cytotoxicity, and efficiently labeled HeLa cells as shown by fluorescence. Thus, the developed nanosystems show potential as strategic probes for fluorescence analyses and MRI, being useful for investigating a variety of biological processes.
关键词： Quantum Dots,Gd(III)-DO3A monoamide chelates,Fluorescence,MRI,Bimodal nanoprobes
更新于2025-11-21 11:08:12
-
Green Preparation of Fluorescent Carbon Quantum Dots from Cyanobacteria for Biological Imaging
摘要： Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. In this study, the low-cost biomass of cyanobacteria was used as the sole carbon source to synthesize water-soluble CQDs by a simple hydrothermal method. The synthesized CQDs were mono-dispersed with an average diameter of 2.48 nm and exhibited excitation-dependent emission performance with a quantum yield of 9.24%. Furthermore, the cyanobacteria-derived CQDs had almost no photobleaching under long-time UV irradiation, and exhibited high photostability in the solutions with a wide range of pH and salinity. Since no chemical reagent was involved in the synthesis of CQDs, the as-prepared CQDs were confirmed to have low cytotoxicity for PC12 cells even at a high concentration. Additionally, the CQDs could be efficiently taken up by cells to illuminate the whole cell and create a clear distinction between cytoplasm and nucleus. The combined advantages of green synthesis, cost-effectiveness and low cytotoxicity make synthesized CQDs a significant carbon source and broaden the application of cyanobacteria and provide an economical route to fabricate CQDs on a large scale.
关键词： bioimaging,cyanobacteria,carbon quantum dots,hydrothermal method
更新于2025-11-21 11:08:12
-
Facile Synthesis of Luffa Sponge Activated Carbon Fiber Based Carbon Quantum Dots with Green Fluorescence and Their Application in Cr(VI) Determination
摘要： Carbon quantum dots (CQDs) were prepared by a chemical oxidation method using lu?a sponge based activated carbon ?ber as the raw material. The obtained CQDs were well characterized. The ?uorescence quenching e?ect of Cr(VI) ion on CQDs was investigated. The results show that the addition of Cr(VI) changes the intensity of the ultraviolet characteristic absorption peak of CQDs, and causes static quenching of the ?uorescence of CQDs. With the increase in the Cr(VI) concentration, the ?uorescence of CQDs was gradually extinguished linearly.
关键词： Activated carbon ?ber,Lu?a sponge,Cr(VI) determination,Fluorescence quenching,Carbon quantum dots
更新于2025-11-21 11:01:37
-
Dual Management of Electrons and Photons to Get High-Performance Light Emitting Devices Based on Si Nanowires and Si Quantum Dots with Al <sub/>2</sub> O <sub/>3</sub> -Ag Hybrid Nanostructures
摘要： Silicon quantum dot (Si QD)-based light emitting devices are fabricated on Si nanowire (Si NW) arrays. Through inserting Al2O3-Ag hybrid nanostructures (Al2O3-Ag HNs) between Si NWs and Si QDs, both photoluminescence (PL) and electroluminescence (EL) are remarkably enhanced compared to the control sample. The PL enhancement can be mainly attributed to passivation effect of Al2O3 to p-type Si NWs and enlarged absorption cross-section due to the local surface plasmon resonance effect of Ag nanoparticles. The EL intensity is enhanced by 14.9-fold at the same injection current under a lower applied voltage, which may result from the high injection efficiency of electrons and the promoted waveguide effect of nanowire structures with Al2O3-Ag HNs. It is demonstrated that light emitting device performances can be well improved by careful management of both electrons and photons via controlling the interface conditions of Si NWs/Si QDs.
关键词： hybrid nanostructures,silicon nanowires,light emitting devices,silicon quantum dots
更新于2025-11-21 11:01:37
-
Low Power Consumption Red Light-Emitting Diodes Based on Inorganic Perovskite Quantum Dots under an Alternating Current Driving Mode
摘要： Inorganic perovskites have emerged as a promising candidate for light-emitting devices due to their high stability and tunable band gap. However, the power consumption and brightness have always been an issue for perovskite light-emitting diodes (PeLEDs). Here, we improved the luminescence intensity and decreased the current density of the PeLEDs based on CsPbI3 quantum dots (QDs) and p-type Si substrate through an alternating current (AC) driving mode. For the different driving voltage modes (under a sine pulsed bias or square pulsed bias), a frequency-dependent electroluminescent (EL) behavior was observed. The devices under a square pulsed bias present a stronger EL intensity under the same voltage due to less thermal degradation at the interface. The red PeLEDs under a square pulsed bias driving demonstrate that the EL intensity drop-off phenomenon was further improved, and the integrated EL intensity shows the almost linear increase with the increasing driving voltage above 8.5 V. Additionally, compared to the direct current (DC) driving mode, the red PeLEDs under the AC condition exhibit higher operating stability, which is mainly due to the reducing accumulated charges in the devices. Our work provides an effective approach for obtaining strong brightness, low power consumption, and high stability light-emitting devices, which will exert a profound in?uence on coupling LEDs with household power supplies directly.
关键词： low power consumption,perovskite quantum dots,silicon,light emitting diodes,alternating current driving
更新于2025-11-21 11:01:37
-
Carbon quantum dots/TiO2 nanosheets with dominant (001) facets for enhanced photocatalytic hydrogen evolution
摘要： Carbon quantum dots/TiO2 nanosheets with a majority of (001) facet (CQDs/TiO2-001) samples are successfully prepared via a facile method. Compared to TiO2-001 and CQDs/P25, the synthesized CQDs/TiO2-001 presents a remarkably higher photocatalytic activity for H2 evolution with a considerable stability. XRD, XPS, HRTEM, FESEM, FTIR, Photoluminescence (PL) spectroscopy, Fluorescence spectroscopy and UV–visible reflectance spectroscopy are adopted to investigate the morphology, structure and properties of synthesized CQDs/TiO2-001. The mechanism of the improved photocatalytic activity over CQDs/TiO2-001 is also investigated. The results show that the improved photocatalytic activity over CQDs/TiO2-001 can be attributed to the synergistic effects of TiO2-001 and CQDs: the highly exposed (001) facets of TiO2-001 promote the transportation of photogenerated electrons and the loading of CQDs restrains the recombination of electrons-holes on (001) facets. Meanwhile, the visible-light absorption is extended because the CQDs serve as a photosensitizer and sensitize TiO2-001 through the newly formed TieOeC bond between the CQDs and TiO2-001.
关键词： Carbon quantum dots,TiO2,Photocatalytic H2 evolution,(001) facet
更新于2025-11-21 11:01:37
-
Highly sensitive and selective label-free detection of dopamine in human serum based on nitrogen-doped graphene quantum dots decorated on Au nanoparticles: Mechanistic insights through microscopic and spectroscopic studies
摘要： A rapid, facile and label-free sensing strategy is developed for the detection of dopamine (DA) in the real samples by exploiting nitrogen-doped graphene quantum dots (N-GQDs) decorated on Au nanoparticles (Au@N-GQD). The as-grown Au@N-GQD exhibits strong blue fluorescence at room temperature and the fluorescence intensity is drastically quenched in presence of DA in neutral medium. The mechanistic insight into the DA sensing by Au@N-GQDs is explored here by careful monitoring of the evolution of the interaction of Au NPs and N-GQDs with DA under different conditions through electron microscopic and spectroscopic studies. The highly sensitive and selective detection of DA over a wide range is attributed to the unique core-shell structure formation with Au@N-GQD hybrids. The quenching mechanism involves the ground state complex formation as well as electron transfer from N-GQDs. The presence of Au NPs in Au@N-GQD hybrids accelerates the quenching process (~14 fold higher than bare N-GQDs) by the formation of stable dopamine-o-quinone (DQ) in this present detection scheme. The fluorescence quenching follows the linear Stern-Volmer plot in the range 0-100 μM, establishing its efficacy as a fluorescence-based DA sensor with a limit of detection (LOD) 590 nM, which is ~27 fold lower than the lowest abnormal concentration of DA in serum (16 μM). This sensing scheme is also successively applied to trace DA in Brahmaputra river water sample with LOD 480 nM including its satisfactory recovery (95-112%). Our studies reveal a novel sensing pathway for DA through the core-shell structure formation and it is highly promising for the design of efficient biological and environmental sensor.
关键词： Dopamine,Fluorescence quenching,Nitrogen-doped graphene quantum dots,Colorimetric sensing,Core-shell structure,Gold nanoparticles
更新于2025-11-21 11:01:37
-
P‐type Sb‐doped Cu <sub/>2</sub> O Hole Injection Layer Integrated on Transparent ITO Electrode for Acidic PEDOT:PSS‐Free Quantum Dot Light Emitting Diodes
摘要： It is developed that transparent p-type Sb-doped cuprous oxide (ACO) integrated Sn-doped In2O3 (ITO) film as hole injection layer (HIL) and anode combined electrodes for quantum dot light emitting diodes (QD-LEDs) to substitute acidic PEDOT:PSS HIL based electrode. By graded co-sputtering of ACO and ITO targets, the graded p-type ACO buffer layer can be integrated on the surface region of the ITO electrodes. P-type conductivity of the ACO film for acting as effective HIL in QD-LEDs is confirmed by a positive Hall coefficient (1.74 (cid:1) 10 (cid:3)1). Due to the well-matched work function of p-type ACO on the ITO electrodes, the acidic PEDOT:PSS-free QD-LEDs exhibited typical current-voltage-luminescence of QD-LEDs. The successful operation of PEDOT:PSS-free QD-LED with p-type ACO integrated ITO electrode indicates that ACO and ITO anode graded sputtering is simpler fabrication steps for cost-effective QD-LEDs and elimination of interfacial reactions caused by the acidic PEDOT:PSS layer for reliable QD-LEDs.
关键词： Sn-doped In2O3,acidic PEDOT:PSS,hole injection layer,p-type conductivity,Sb-doped Cu2O,quantum dots light emitting diodes
更新于2025-11-21 10:59:37
-
Tunable Emission of Bluish Zn-Cu-Ga-S Quantum Dots by Mn Doping and their Electroluminescence
摘要： Based on bluish-emitting double-shelled quantum dots (QDs) of Zn?Cu?Ga?S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS:Mn) QDs exhibit a distinct Mn2+ 4T1?6A1 emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor-acceptor pair (DAP) recombinations. The relative contribution of Mn emission in the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration all QDs possess high PL quantum yield (QY) levels of 74?79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. When compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn2+ EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.
关键词： Tunable emission,Electroluminescence,Emission quenching,Zn?Cu?Ga?S quantum dots,Mn doping
更新于2025-11-20 15:33:11