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Large-scale uniform fabrication and morphology control of ultrafine perovskite nanocrystals
摘要： Nanomaterials are playing more and more important roles in modern industry, while the large-scale fabrication and dispersibility still need to be addressed. This report explores the uniform fabrication and morphology control of ultrafine BaTiO3 (BT) nanocrystals using a "TEG-sol" method. By varying the reactant concentration, the obtained product sols, Ba/Ti ratios, structure and morphology of the nanocrystals are investigated. The results reveal that under low concentrations (0.4 - 0.8 mol/L), transparent sols with uniform BT nanocrystals are obtained. Increasing the concentration to higher than 1.0 mol/L, BT precipitates with abnormal large crystals are obtained. Moreover, the Ba/Ti ratio variation further reveals that the surface organics are critical to the control of crystal size and morphology. This investigation is potential to be extended to the synthesis of various perovskite nanocrystals.
关键词： morphology control,Nanomaterials,BaTiO3,TEG-sol method,perovskite nanocrystals
更新于2025-09-10 09:29:36
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Synthesis of All-Inorganic Cd-Doped CsPbCl <sub/>3</sub> Perovskite Nanocrystals with Dual-Wavelength Emission
摘要： Doped lead halide perovskite nanocrystals (NCs) have garnered significant attention due to their superior optoelectronic properties. Here, we report a synthesis of Cd-doped CsPbCl3 NCs by decoupling Pb- and Cl-precursors in a hot injection method. The resulting Cd-doped perovskite NCs manifest a dual-wavelength emission profile with the first reported example of Cd-dopant emission. By controlling Cd-dopant concentration, the emission profile can be tuned with a dopant emission quantum yield up to 8%. A new secondary emission (~610 nm) is induced by an energy transfer process from photo-excited hosts to Cd-dopants, and a subsequent electronic transition from excited state (3Eg) to ground state (1A1g) of [CdCl6]4- units. This electronic transition matches well with a first-principles density functional theory calculation. Further, the optical behavior of Cd-doped CsPbCl3 NCs can be altered through post-synthetic anion-exchange reactions. Our studies present a new model system for doping chemistry studies in semiconductors for various optoelectronic applications.
关键词： Energy transfer,Doping,Perovskite,Anion exchange,Nanocrystals
更新于2025-09-10 09:29:36
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Wavelength-Tunable Band-Edge Photoluminescence of Nonstoichiometric Ag–In–S Nanoparticles via Ga <sup>3+</sup> Doping
摘要： The nonstoichiometry of I?III?VI semiconductor nanoparticles, especially the ratio of group I to group III elements, has been utilized to control their physicochemical properties. We report the solution-phase synthesis of non-stoichiometric Ag?In?S and Ag?In?Ga?S nanoparticles and results of the investigation of their photoluminescence (PL) properties in relation to their chemical compositions. While stoichiometric AgInS2 nanoparticles simply exhibited only a broad PL band originating from defect sites in the particles, a narrow band edge PL peak newly appeared with a decrease in the Ag fraction in the nonstoichiometric Ag?In?S nanoparticles. The relative PL intensity of this band edge emission with respect to the defect-site emission was optimal at a Ag/(Ag + In) value of ca. 0.4. The peak wavelength of the band edge emission was tunable from 610 to 500 nm by increased doping with Ga3+ into Ag?In?S nanoparticles due to an increase of the energy gap. Furthermore, surface coating of Ga3+-doped Ag?In?S nanoparticles, that is, Ag?In?Ga?S nanoparticles, with a GaSx shell drastically and selectively suppressed the broad defect-site PL peak and, at the same time, led to an increase in the PL quantum yield (QY) of the band edge emission peak. The optimal PL QY was 28% for Ag?In?Ga?S@GaSx core?shell particles, with green band-edge emission at 530 nm and a full width at half-maximum of 181 meV (41 nm). The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic-element-free I?III?VI-based nanoparticles in a wide area of applications.
关键词： band-edge photoluminescence,multinary semiconductor,quantum dots,nonstoichiometry,I?III?VI2 semiconductor,visible photoluminescence,wavelength tunability,semiconductor nanocrystals
更新于2025-09-10 09:29:36
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Optically-Active Nanocrystals for Inner Filter Effect-Based Fluorescence Sensing: Achieving Better Spectral Overlap
摘要： Among various photophysical processes for fluorescence modulation, inner filter effect (IFE) is well-known for its simplicity and no requirement of the distances between the fluorophores and the corresponding modulators. Theoretically, the key to maximize the sensitivity of IFE-based fluorescent assays is to enlarge the overlap between the absorption of the absorber and the excitation/emission of the fluorophores. However, it is difficult to achieve perfect spectral overlap for IFE in conventional organic fluorophores with constant excitation/emission. The emergence of various optically-active nanocrystals greatly revolutionize the IFE-based fluorescent sensing. Therefore in this critical review, we first made an introduction to IFE from the viewpoint of its photophysical process. Particularly, the similarities and differences of IFE and FRET for better understanding of IFE are discussed, and the general rules for verification of IFE are proposed. The use of various optically-active nanocrystals for enhanced IFE-based sensing is especially concerned in this review.
关键词： fluorescence resonance energy transfer,Inner filter effect,spectral overlap,fluorescent sensors,optically-active nanocrystals,tunable spectra
更新于2025-09-10 09:29:36
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Fluorescent Metal-Semiconductor Hybrid Structures by Ultrasound-Assisted In-Situ Growth of Gold Nanoparticles on Silica-Coated CdSe-Dot/CdS-Rod Nanocrystals
摘要： Gold nanocrystals (AuNCs) were grown on the surface of silica coated CdSe-dot/CdS-rod core/shell nanocrystals by reduction of Au3+ ions in polyethylene glycol under ultrasonic irradiation. The polyethylene glycol not only prevents the penetration of gold ions or precursor molecules into the silica shell, but it also acts as the reducing agent for Au3+ ions. The silica shell’s surface promotes the heterogeneous nucleation of gold nanocrystals, while the ultrasonic irradiation accelerates and enhances the gold nucleation on the silica surface, and ensures the formation of AuNCs with a relatively narrow size distribution. The plasmon-exciton interaction in these metal-semiconductor hybrid systems leads to decreased fluorescence lifetimes and strongly reduced fluorescence blinking of individual hybrid structures.
关键词： ultrasonic irradiation,Gold nanocrystals,CdSe-dot/CdS-rod nanocrystals,plasmon-exciton interaction,polyethylene glycol
更新于2025-09-09 09:28:46
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Bragg coherent diffraction imaging of iron diffusion into gold nanocrystals
摘要： Understanding how diffusion takes place within nanocrystals is of great importance for their stability and for controlling their synthesis. In this study, we used the strain sensitivity of Bragg coherent diffraction imaging (BCDI) to study the diffusion of iron into individual gold nanocrystals in situ at elevated temperatures. The BCDI experiments were performed at the I-07 beamline at Diamond Light Source, UK. The diffraction pattern of individual gold nanocrystals was measured around the (11-1) Bragg peak of gold before and after iron deposition as a function of temperature and time. Phase retrieval algorithms were used to obtain real space reconstructions of the nanocrystals from their measured diffraction patterns. Alloying of iron with gold at sample temperatures of 300 °C–500 °C and dealloying of iron from gold at 600 °C were observed. The volume of the alloyed region in the nanocrystals was found to increase with the dose of iron. However, no significant time dependence was observed for the structure following each iron deposition, suggesting that the samples reached equilibrium relatively quickly. The resulting phase distribution within the gold nanocrystals after the iron depositions suggests a contraction due to diffusion of iron. Our results show that BCDI is a useful technique for studying diffusion in three dimensions and alloying behaviour in individual crystalline grains.
关键词： gold iron,nanocrystals,diffusion,Bragg coherent diffraction imaging
更新于2025-09-09 09:28:46
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Blue-Emitting CsPbCl <sub/>3</sub> Nanocrystals: Impact of Surface Passivation for Unprecedented Enhancement and Loss of Optical Emission
摘要： High-energy-emitting CsPbCl3 nanocrystals have shown significant loss and enhancement of their emission intensity (～40?50 folds) during purification and surface treatments, respectively. This confirms that the surfaces of these nanocrystals are very sensitive. In this Letter, physical insights of the interface bindings on the surface of these blue-emitting CsPbCl3 nanocrystals with different passivating agents and their impact on purification are investigated. Using various metal chlorides consequential irrespective of the charge and size of the metal ions, metal acetates, and nonmetal chloride, the predominant influence of chloride ions in helping retrieve/intensify the blue emission is established. The purification processes are observed to be very delicate, and successive purifications with introduction of polar nonsolvents led to the transformation of an emitting cubic CsPbCl3 phase to nonemitting tetragonal CsPb2Cl5 phase nanocrystals irreversibly. The impact of various salt additions only temporarily helped in enhancing the emission, but the phase change remained inevitable upon successive purification. However, as a remedy, by in situ use of alkylammonium chloride salt in high-temperature reactions, the surface binding was improved, and significant emission as well as the phase could be retained with successive purifications.
关键词： surface passivation,purification,optical emission,CsPbCl3 nanocrystals,blue-emitting
更新于2025-09-09 09:28:46
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Long-range hierarchical nanocrystal assembly driven by molecular structural transformation
摘要： The hierarchical control in biogenic minerals, from precise nanomorphology control to subsequent macroscopic assembly, remains a formidable challenge in artificial synthesis. Studies in biomineralization, however, are largely limited to atomic/molecular scale crystallization, devoting little attention to biomolecular higher order structures (HOSs) which impact critically on long-range assembly of biominerals. Here we demonstrate a biomimetic route that explores peptide HOSs on guiding nanocrystal formation and anisotropic assembly into hierarchical structures. It is found that Pt{100} specific peptide T7 (Ac-TLTTLTN-CONH2) adopts ST-turn, promoting cubic Pt nanocrystal formation at low concentration, and spontaneously transforms into β-sheet with increased concentration. The β-sheet T7-Pt{100} specificity drives cubic Pt nanocrystals to self-assemble into large-area, long-range, [100] linear assemblies. This study provides a robust demonstration for bio/non-biogenic material specificity, nanoscale synthesis, and long-range self-organization with biomolecular HOSs, and opens vast opportunities for multiscale programmable structures.
关键词： hierarchical nanocrystal assembly,peptide HOSs,Pt nanocrystals,biomimetic route,molecular structural transformation
更新于2025-09-09 09:28:46
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Room-temperature synthesis of Mn2+-doped cesium lead halide perovskite nanocrystals via a transformation doping method
摘要： Currently, Mn2+-doped cesium lead halide perovskite nanocrystals have attracted research interests. Here, we report a novel room-temperature transformation doping method for the synthesis of Mn2+-doped CsPbCl3 and CsPb(Br/Cl)3 nanocrystals. Innovatively, the transformation of Cs4PbX6 (X=Cl, Br) phase which has no excitation emission to CsPbX3 phase which has strong luminescence was used in this mechanism. Simply injecting MnCl2 precursor into Cs4PbX6 solution could result in the full transformation of Cs4PbX6 phase to CsPbX3 phase and Mn2+-doped CsPbCl3 or CsPb(Br/Cl)3 were obtained. The basic idea for the transformation doping method is that MnCl2 can not only drive the transformation of the two structures but also Mn2+ can substitute Pb2+. In this reaction, the concentration of Mn precursor is a key influence factor. Moreover, instead of the ligand of OA, the acetic acid was used in our method. Through the adjustment of the ligand in precursor, not just the photoluminescence quantum yields of as-prepared Mn2+-doped CsPbCl3 nanocrystals were improved from 7.8 to 32.6% (Mn2+-doped CsPb(Br/Cl)3 nanocrystals even could reach to 42.7%), the nanocrystals also retained outstanding stability. We propose a combination of structure transformation and ion doping as a perovskite doping mechanism. Our doping method is a novel strategy for lead halide perovskite nanocrystals doping project and it could provide more possibilities in the future.
关键词： photoluminescence quantum yields,Cs4PbX6,Mn2+-doped cesium lead halide perovskite nanocrystals,CsPbX3,room-temperature transformation doping method
更新于2025-09-09 09:28:46
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Formation of Nd1–xBixFeO3 Nanocrystals under Conditions of Glycine-Nitrate Synthesis
摘要： Nd1–xBixFeO3 nanocrystals with crystallite size 30?60 nm have been prepared under conditions of glycine–nitrate burning. Single-phase Nd1–xBixFeO3 nanocrystals are formed over the entire studied concentrations range if the glycine–nitrate synthesis is performed in excess of the oxidizer. Under these conditions, a continuous range of the Nd1–xBixFeO3 solid solutions (0 ≤ х ≤ 0.75) crystallized in the rhombic system (space group Pbnm) are formed without crystallization of the burning intermediates. The Nd1–xBixFeO3 solid solutions (х = 0.775, 0.8) crystallize in the rhombic system (space group Pbаm).
关键词： solid solutions,nucleation,solution burning,BiFeO3,nanocrystals,NdFeO3,phase formation
更新于2025-09-09 09:28:46