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Highly Selective Optical Detection of Fe <sup>3+</sup> Ions in Aqueous Solution Using Label-Free Silicon Nanocrystals
摘要： Highly brightness amine-terminated silicon nanocrystals (Si NCs) have been utilized in a simple and rapid assay for the highly selective and sensitive detection of Fe3+ via quenching of their strong blue luminescence, without the need for analyte-specific labeling groups. Sensitive detection of Fe3+ is successfully demonstrated, with a linear relationship observed between luminescence quenching and Fe3+ concentration from 5 × 10?6 to 900 × 10?6 m and a limit of detection of 1.3 × 10?6 m. The Si NCs show excellent selectivity toward Fe3+ ions, with no quenching of the luminescence signal induced by the presence of Fe2+ ions, allowing for solution phase discrimination between the ionic species in different charge states.
关键词： nanocrystal,sensor,iron,optical detection
更新于2025-11-14 15:32:45
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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52
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Mechanism of photoluminescence intermittency in organic-inorganic perovskite nanocrystals
摘要： Lead halide perovskite nanocrystals have demonstrated their potential as active materials for optoelectronic applications over the past few years. Nevertheless one issue which hampers their applicability has to do with the observation of photoluminescence intermittency, commonly referred to as blinking, as in their inorganic counterparts. Such behavior, reported for structures well above the quantum confinement regime, has been discussed to be strongly related with the presence of charge carrier traps. In this work we analyze the characteristics of this intermittency and explore the dependence with the surrounding atmosphere, showing evidence for the critical role played by the presence of oxygen. We discuss a possible mechanism in which a constant creation/annihilation of halide-related carrier traps takes place under light irradiation, the dominant rate being determined by the atmosphere.
关键词： photoluminescence,Hybrid organic inorganic perovskites,spectroscopy,nanocrystal,blinking
更新于2025-09-23 15:23:52
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Copper’s Role in the Photoluminescence of Ag1?xCuxInS2 Nanocrystals, from Copper-Doped AgInS2 (x ~ 0) to CuInS2 (x = 1)
摘要： A series of Ag1?xCuxInS2 nanocrystals (NCs) spanning from 0 ≤ x ≤ ~1 was synthesized by partial cation exchange to identify copper’s contributions to the electronic structure and spectroscopic properties of these NCs. Discrete mid-gap states appear above the valence band (VB) upon doping AgInS2 NCs with Cu+ (small x). Density functional theory (DFT) calculations confirm that these mid-gap states are associated with the 3d valence orbitals of the Cu+ impurities. With increasing x, these impurity d levels gradually evolve to become the VB edge of CuInS2 NCs, but the highest-occupied orbital's description does not change significantly across the entire range of x. In contrast with this gradual evolution, Ag1?xCuxInS2 NC photoluminescence shifts rapidly with initial additions of Cu+ (small x) but then becomes independent of x beyond x > ~0.20, all the way to CuInS2 (x = 1.00). Data analysis suggests small but detectable hole delocalization in the luminescent excited state of CuInS2 NCs, estimated by Monte Carlo simulations to involve at most about four copper ions. These results provide unique insights into the luminescent excited states of these materials and they reinforce the description of CuInS2 NCs as “heavily copper-doped NCs” in which photogenerated holes are rapidly localized in copper 3d-based orbitals.
关键词： silver indium sulfide,nanocrystal,cation exchange,Copper indium sulfide,copper-doped,photoluminescence
更新于2025-09-23 15:23:52
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Efficient optical gain in CdSe/CdS Dot-in-Rod nanocrystals
摘要： Excitonic state-resolved pump/probe spectroscopy is performed on semiconductor dot-in-rod nanocrystals. Using excitonic state-resolved pumping we are able to resolve effects of the rod upon exciton dynamics of the core. The shell has the effect of lowering gain threshold, increasing absorption cross-section, and increasing the Auger lifetime, hence nanorods are shown to be an effective means of enhancing gain performance of nanomaterials.
关键词： nanocrystal,excitons,Auger processes,Quantum dot,optical gain,multiexcitons.
更新于2025-09-23 15:23:52
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Photocatalytic overall water splitting on isolated semiconductor photocatalyst sites in an ordered mesoporous silica matrix: A multiscale strategy
摘要： Photocatalytic overall water splitting (OWS) in a stoichiometric ratio has attracted increasing attention for the realization of a sustainable, environmentally friendly future. However, this reaction exhibits sluggish kinetics due to efficiency limitations of the involved steps, including photon absorption, electron transfer, and the reactions that occur at triple-phase boundary regions. Herein, we report a general multiscale strategy to address this challenge by designing a model composite catalyst with a high loading density of isolated Bi0.5Y0.5VO4 nanocrystals, as building blocks, dispersed in a hexagonally ordered mesoporous silica matrix. In contrast to the well-recognized heterojunction formed between different semiconductors, we show that confined growth favours the formation of isolated quaternary solid-solution photocatalysts (Bi0.5Y0.5VO4), which can further interface with the insulating silica to overcome temperature limitations and exhibit enhanced photon absorption and electrochemical and mass transfer properties due to the transparent periodic porous structure of silica and the as-formed small nanocrystals with high crystallinity and a passivated surface. When the semiconductor photocatalyst is incorporated with the inert silica insulator, this nanoarchitecture does not inhibit the OWS activity but actually delivers a 10-fold higher OWS activity than bulk Bi0.5Y0.5VO4 prepared by the conventional solid-state method.
关键词： Multiscale strategy,Photocatalysis,Isolated solid-solution nanocrystal,Overall water splitting,Mesoporous composite
更新于2025-09-23 15:23:52
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Nanocrystal-engineered thin CuO film photocatalyst for visible-light-driven photocatalytic degradation of organic pollutant in aqueous solution
摘要： We design a thin CuO film photocatalyst for visible-light-driven photocatalytic degradation of methylene blue (MB). Nanocrystal engineering of the photocatalyst is performed by sputtering with concurrent in-situ thermal treatment. The impacts of the in-situ thermal treatment temperature and sputtering conditions on the material properties of the thin CuO film photocatalyst are investigated in detail. Systematic characterization using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) indicates that deposition at elevated temperature and higher sputtering power significantly improves the surface structure and crystallinity of thin CuO film, which promotes charge transfer and ultimately results in better performance for MB photocatalytic degradation. The best-performing sample is the one sputtered at an elevated temperature of 300 °C and a sputtering power of 300 W. The photodegradation efficiency and physical durability of the samples were also analyzed after using for 5 cycles. The results indicate that in-situ thermal treatment and nanocrystal engineering of the thin CuO film significantly improve the physical durability.
关键词： Thin CuO film photocatalyst,Visible-light-driven photocatalytic degradation,Nanocrystal engineering
更新于2025-09-23 15:23:52
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Enhanced near-infrared emission in Yb3+-Cr3+ codoped KZnF3 glass ceramics excited by a solar simulator
摘要： Cr3+-Yb3+ codoped bulk glass-ceramics containing KZnF3 nanocrystals are fabricated by thermal treatment of cast glass samples and characterized by X-ray diffraction and transmission electron microscopy. The luminescent properties of the glass and glass ceramic are investigated from the measured photoluminescence spectra and fluorescent lifetime. The measurement results demonstrate that Cr3+ and Yb3+ ions are both predominantly hosted in the KZnF3 nanocrystals, and the energy absorbed by Cr3+ ions is efficiently transferred to Yb3+ ions when excited at 450 nm. Compared to the glass, the near-infrared emission in the Cr3+-Yb3+ codoped glass ceramics is significantly enhanced when the excitation wavelength lies in the range λ~400–800 nm of a solar simulator. Results indicate that the Cr3+-Yb3+ codoped KZnF3 glass ceramic provides a promising material for spectral conversion from visible sunlight to near-infrared emission and a novel gain material for solar pumped fiber laser.
关键词： Nanocrystal,Solar pumped,Glass ceramics,Near-infrared
更新于2025-09-23 15:23:52
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Suppression of Electrochemically Driven Phase Transition in Nanostructured MoS2 Pseudocapacitors Probed Using Operando X-ray Diffraction
摘要： Pseudocapacitors with non-diffusion-limited charge storage mechanisms allow for fast kinetics that exceed conventional battery materials. It has been demonstrated that nanostructuring conventional battery materials can induce pseudocapacitive behavior. In our previous study, we found that assemblies of metallic 1T MoS2 nanocrystals show faster charge storage compared to the bulk material. Quantitative electrochemistry demonstrated that the current response is capacitive. In this work, we perform a series of operando X-ray diffraction studies upon electrochemical cycling to show that the high capacitive response of metallic 1T MoS2 nanocrystals is due to suppression of the standard first-order phase transition. In bulk MoS2, a phase transition between 1T and triclinic phases (LixMoS2) is observed during lithiation and delithiation in both the galvanostatic traces (as distinctive plateaus) and the X-ray diffraction patterns with the appearance of the additional peaks. MoS2 nanocrystal assemblies, on the other hand, show none of these features. We hypothesize that the reduced MoS2 crystallite size suppresses the first-order phase transition and gives rise to solid solution-like behavior, potentially due to the unfavorable formation of nucleation sites in confined space. Overall, we find that nanostructuring MoS2 suppresses the 1T-Triclinc phase transition and shortens Li-ion diffusion path lengths, allowing MoS2 nanocrystal assemblies to behave as nearly ideal pseudocapacitors.
关键词： intercalation pseudocapacitor,pseudocapacitance,MoS2,phase transition suppression,porous electrodes,nanocrystal assemblies,fast charging
更新于2025-09-23 15:23:52
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Growth of perovskite nanocrystals in poly-tetra fluoroethylene based microsystem: On-line and off-line measurements
摘要： Cesium lead halide perovskite nanocrystals are photoelectric nanomaterials that have potential applications in a variety of areas due to their excellent photoelectric and tunable photo luminescent properties. In this work, we investigate the synergetic effects of reaction temperature, reaction-capillary length and flow rate on the growth kinetics of perovskite nanocrystals in PTFE-based microsystem and the photoluminescence characteristics of the synthesized nanocrystals both online and offline. The on-line measurement finds that increasing the reaction temperature leads to the increase of the wavelength of the PL emission peak of the nanocrystals synthesized at different reaction temperatures decreases with the increase of the flow rate. The off-line measurement reveals that increasing the flow rate generally leads to the blueshift of the PL emission peaks and the decrease of the average size of the perovskite nanocrystals synthesized at the reaction temperature of 160 oC in the capillary length of 60 cm. Increasing temperature leads to the increase of the emission wavelength of the perovskite nanocrystals from 560 nm to 608 nm. The temperature dependence of the average size of the synthesized nanocrystals with the same synthesis conditions at different temperatures can be described by the Arrhenius relationship with an activation energy of 8.54 kJ/mol. Five different cross-sections of the synthesized perovskite nanocrystals are observed, including rhombus, hexagon, rectangle, square and quadrangle with three of them being observed for the first time.
关键词： microreaction system,morphologies,growth kinetics,reaction parameters,perovskite nanocrystal
更新于2025-09-23 15:23:52