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Temperature-dependent photoluminescence of pure and Mn-doped CsPbCl3 nanocrystals
摘要： Temperature-dependent photoluminescence (PL) properties of Mn-doped CsPbCl3 nanocrystals (NCs) are studied and compared with pure CsPbCl3 NCs by use of steady-state and time-resolved PL spectroscopies. The intrinsic exciton PL of the CsPbCl3 NCs locates at the wavelength range from 405 to 410 nm. The PL intensity in this range decreases rapidly, and the bandgap and linewidth become wider with rising temperature from 78 to 350 K. It is found that the exciton PL shows biexponential kinetics. The short-lived emission is ascribed to the surface trapping state recombination in NCs that has a photoinduced trapped pathway and a temporally resolved peak shift. The long-lived component is due to the band-edge excitonic recombination. Mn dopant open a new emission window at the wavelength range from 560 to 680 nm, of which intensity increases from 140 to 270 K, and then decreases with rising temperature up to 350 K. This unusual temperature dependence is ascribed to the thermal-assisted transition from the excitonic state of NCs to the 4T1 energy level of Mn2+. This work shows the potential of transition metal element doped perovskite NCs that can take advantage of the coupling between excitons and the d electrons of the dopants for expanded functionalities, such as temperature sensor and light-emitting diode.
关键词： Photoluminescence,Band-edge exciton,CsPbCl3,Mn-doped,Nanocrystals
更新于2025-11-25 10:30:42
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Structural characterization of tin nanocrystals embedded in silicon by atomic probe tomography
摘要： Tin nanocrystals embedded in silicon are studied by atom probe tomography and by photoluminescence spectroscopy in the 0.76–1.07 eV region of emission energies. The nanocrystals have been fabricated by molecular beam epitaxy followed by a post-growth annealing step at various temperatures. One particular sample, annealed at a temperature of 725 ?C, shows a distinctly higher optical activity. It is found, however, that the distinct behavior cannot be explained by variations in the nanocrystal composition or in the properties of Sn atoms dissolved in the surrounding Si matrix, which can be investigated by atom probe tomography.
关键词： Sn-nanocrystals,Photoluminescence,Atom probe tomography
更新于2025-11-21 11:20:42
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Microwave-Assisted Synthesis of Quasi-Pyramidal CuInS <sub/>2</sub> -ZnS Nanocrystals for Enhanced Near-Infrared Targeted Fluorescent Imaging of Subcutaneous Melanoma
摘要： Near-infrared (NIR) fluorescent CuInS2–ZnS nanocrystals (CIZS NCs) are synthesized via an ultra-fast, non-injection microwave (MW)-assisted nanoalloying process at 230 oC within 5 min using 1-dodecanethiol (DDT) as both the sulfur source and solvent under solvothermal (ST) condition. The structural and surface analyses reveal that DDT-functionalized CIZS NCs exhibit quasi-pyramids of tetragonal-phase with well-defined facets. The DDT-functionalized CIZS NCs present a photoluminescence quantum yield (PLQY) of 76% and a long-lived fluorescence lifetime of ≈0.6 μs in organic-phase. Subsequently, DDT-functionalized CIZS NCs are phase-transferred via ligand-exchange using 11-mercaptoundecanoic acid (MUA) into water-soluble MUA–CIZS NCs that exhibit a substantial PLQY of 55%. In addition, the NIR-fluorescent MUA-functionalized CIZS NCs in conjugation with folic acid (FA), as a tumor-targeting ligand, demonstrates enhanced tumor-targeted imaging ability. The FA–MUA–CIZS NC conjugates exhibit a cell viability of ≈75% even at the highest concentration of 1 mg mL–1 and a labeling efficiency of 95.4%. The in vivo imaging results corroborate that FA–MUA–CIZS NCs conjugates are actively targeted to folate receptor-positive B16F10 tumor-bearing C57BL/6 mice in 2 h. The histopathological and hematological studies confirm no significant changes in tissue architecture and blood biochemical parameters. The confocal microscopy studies reveal deep penetration and uniform distribution of FA–MUA–CIZS NCs conjugates in subcutaneous melanoma.
关键词： CuInS2–ZnS nanocrystals,nano-bioprobe,nanoalloying approach,targeted bioimaging,microwave-solvothermal method
更新于2025-11-21 11:08:12
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Kinetic stabilization of cellulose nanocrystals in a photocurable prepolymer for application as an adhesion promoter in UV-curable coatings
摘要： Cellulose nanocrystals (CNC) at low loading levels were shown to reinforce a photocurable coating resulting in improved adhesion. A polyether polyol containing CNC at loading levels of up to 1.8 wt% was grafted with 3-isopropenyl-α,α-dimethylbenzyl isocyanate to functionalize it with a photocurable group. The nanoparticles were kinetically stabilized in the rapidly forming prepolymer of high viscosity. Photoinitiators and a difunctional reactive diluent were added to produce optically transparent coatings and free films upon irradiation by ultraviolet (UV) light. This allowed evaluation of the effects of CNC at low loading levels in a glassy polymer matrix obtained through a rapid cure system. Incorporation of CNC nanoparticles in the polymer matrix resulted in an average improvement in adhesive strength of 154% while enhancing tensile strength by an average of 16%. The technique described could be used as a new approach to reduce adhesive failure in UV-curable coatings without sacrificing their mechanical strength.
关键词： Coatings,Nanoreinforcement,UV curing,Nanocomposite,Adhesion promoter,Cellulose nanocrystals
更新于2025-11-21 11:01:37
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Tessellation of Chiral-Nematic Cellulose Nanocrystal Films by Microtemplating
摘要： In biological architectures, material properties are optimized by the hierarchical structuring of components with a multiscaled order, from the nano- to the macroscales. Such designs enable, for instance, programmed yield points that maximize toughness. However, research efforts in biomimetic materials have focused on the assembly of nano- or macrostructures individually. In this study, high strength cellulose nanocrystals (CNCs), assembled into chiral-nematically ordered structures, are tiled into a higher level, macro-sized, architecture by topographical templating. As templates, two meshed architectures with distinct feature sizes are evaluated, and the optomechanical properties of the resulting films are compared to featureless, flat, CNC films. Controlling capillary stresses arising during CNC assembly is shown to enable control over the orientation of the chiral-nematic director across the topography of the template. Tuning the specific reflections and multiscaled fracture propagation is demonstrated for the microtemplated CNC films. The latter phenomenon contributed to enhancing the toughness of the material through a high tortuosity of fracture propagation in all (x, y, z) directions. The presented findings are expected to pave the way towards the incorporation of current research in cellular metamaterials with the research focusing on the generation of nanoscaled biomimetic constructs.
关键词： tessellation,conformability,biomimetic,hierarchical,cellulose nanocrystals
更新于2025-11-21 11:01:37
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Post-synthesis phase and shape evolution of CsPbBr3 colloidal nanocrystals: The role of ligands
摘要： The surface chemistry of colloidal cesium lead bromide (CsPbBr3) nanocrystals is decisive in determining the stability and the final morphology of this class of materials, characterized by ionic structure and a high defect tolerance factor. Here, the high sensitivity of purified colloidal nanocubes of CsPbBr3 to diverse environmental condition (solvent dilution, ageing, ligands post synthetic treatment) in ambient atmosphere is investigated by means of a comprehensive morphological (electron microscopy), structural (θ/2θ X-ray diffraction (XRD) and grazing incidence wide angle scattering (GIWAXS)), and spectroscopic chemical (1H nuclear magnetic resonance (NMR), nuclear Overhauser effect spectroscopy (NOESY), absorption and emission spectroscopy) characterization. The aging and solvent dilution contribute to modify the nanocrystal morphology, due to a modification of the ligand dynamic. Moreover, we establish the ability of aliphatic carboxylic acids and alkyl amines ligands to induce, even in a post preparative process at room temperature, structural, morphological and spectroscopic variations. Upon post synthesis alkyl amine addition, in particular of oleyl amine and octyl amine, the highly green emitting CsPbBr3 nanocubes effectively turn into one-dimensional (1D) thin tetragonal nanowires or lead halide deficient rhombohedral zero-dimensional (0D) Cs4PbBr6 structures with a complete loss of fluorescence. The addition of an alkyl carboxylic acid, as oleic and nonanoic acid, produces the transformation of nanocubes into still emitting orthorombic two-dimensional (2D) nanoplates. The acid/base equilibrium between the native and added ligands, the adsorbed/free ligands dynamic in solution and the ligand solubility in non-polar solvent contribute to render CsPbBr3 particularly sensitive to environmental and processing conditions and, therefore prone to undergo to structural, morphological and, hence spectroscopic, transformations.
关键词： lead halide perovskite nanocrystals,surface chemistry,ligands equilibria,long term stability
更新于2025-11-21 11:01:37
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Fusing Nanowires into Thin Films: Fabrication of Graded‐Heterojunction Perovskite Solar Cells with Enhanced Performance
摘要： Perovskite solar cells (PSCs) have recently experienced a rapid rise in power conversion efficiency (PCE), but the prevailing PSCs with conventional mesoscopic or planar device architectures still contain nonideal perovskite/hole-transporting-layer (HTL) interfaces, limiting further enhancement in PCE and device stability. In this work, CsPbBr3 perovskite nanowires are employed for modifying the surface electronic states of bulk perovskite thin films, forming compositionally-graded heterojunction at the perovskite/HTL interface of PSCs. The nanowire morphology is found to be key to achieving lateral homogeneity in the perovskite film surface states resulting in a near-ideal graded heterojunction. The hidden role of such lateral homogeneity on the performance of graded-heterojunction PSCs is revealed for the first time. The resulting PSCs show high PCE up to 21.4%, as well as high operational stability, which is superior to control PSCs fabricated without CsPbBr3-nanocrystals modification and with CsPbBr3-nanocubes modification. This study demonstrates the promise of controlled hybridization of perovskite nanowires and bulk thin films for more efficient and stable PSCs.
关键词： nanocrystals,morphology control,heterojunction,solar cells,halide perovskites
更新于2025-11-20 15:33:11
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Increase of photoluminescence blinking frequency of 3C–SiC nanocrystals with excitation power
摘要： Super-resolution optical fluctuation imaging is dependent on the blinking frequency of fluorophores. Consequently, improvement of the photoluminescence (PL) blink frequency is important. This is achieved for 3C–SiC nanocrystals (NCs) by simply increasing the excitation power. Using an excitation of 488 nm with powers of 5 μW to 50 μW, individual 3C–SiC NC always exhibits PL blinking with a short on-state sojourn time (< 0.1 s). A fast Fourier transform method is exploited to determine the PL switching frequency. It is found that the frequency of the bright state increases from 2 Hz to 20 Hz as the excitation power increases from 5 μW to 50 μW, which is explained by the Auger photonionization model.
关键词： photoluminescence,nanocrystals,Auger photonionization,blinking
更新于2025-11-20 15:33:11
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Au@Cu Core-Shell Nanocubes with Controllable Sizes in the Range of 20-30 nm for Applications in Catalysis and Plasmonics
摘要： Predominantly covered by a single type of {100} facets, Cu nanocubes are attractive catalytic material toward reactions such as electrochemical reduction of CO2. Here we report a seed-mediated approach to the facile synthesis of Au@Cu core-shell nanocubes with hexadecylamine and Cl- serving as capping agents toward the {100} facets of Cu and glucose as a reducing agent. The large (12%) lattice mismatch between Cu and Au led to the localized epitaxial growth of Cu shells on the Au seeds and the formation of nanocubes with randomly distributed Au cores. Compared to the same synthesis in the absence of Au seeds, the reduction of Cu(II) ions was greatly accelerated in the presence of Au seeds because of the autocatalytic surface reduction. It was also found that the structure and morphology of the products were highly dependent on the concentration of Cu(II) precursor in the reaction solution. Nanoplates rather than nanocubes were obtained when the concentration of Cu(II) precursor was reduced down to a certain level. By varying the reaction time and/or the amount of Au seeds, the size of the Au@Cu nanocubes could be tuned in a range of 20–30 nm. The as-synthesized core-shell nanocubes exhibited a strong localized surface plasmon resonance peak at 581 nm and the resonance was dominated by absorption rather than scattering. It is expected that the Au@Cu nanocubes with uniform and controllable sizes will find use in a variety of applications such as plasmonics and catalysis.
关键词： lattice mismatch,Copper nanocubes,core-shell nanocrystals,plasmonics,seed-mediated growth
更新于2025-11-19 16:56:35
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Saponification Precipitation Method of CsPbBr3 Nanocrystals with Blue-Green Tunable Emission
摘要： We report on a new synthesis process for halide perovskite nanoplatelets and nanoplates that switches the production process of the cesium precursor from a fatty acid/cesium salt reaction to a cesium base/fatty acid ester reaction, thus enabling the reaction to occur in ambient conditions in minutes instead of hours. The saponification precipitation process reported here, as a result, does not require a vacuum oven or inert reaction environment in obtaining the cesium precursor, or any part of the reaction. Furthermore, the process creates a hygroscopic byproduct that results in a self-drying synthesis. The obtained perovskite nanocrystals exhibit a blue-green tunable emission that occurs via quantum confinement effect, phase, and morphology change. The consequence of these physical processes is that the band gap is highly tunable with temperature and the resulting nanocrystals show remarkable optical properties, while greatly simplifying the production of halide perovskite nanoplatelets and nanoplates.
关键词： Blue-Green Tunable Emission,Saponification Precipitation Method,Hybrid Materials,Magnetic,CsPbBr3 Nanocrystals,Plasmonics,Optical
更新于2025-11-19 16:46:39