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Yb <sup>3+</sup> /Ln <sup>3+</sup> /Mn <sup>4+</sup> (Ln = Er, Ho, and Tm) doped Na <sub/>3</sub> ZrF <sub/>7</sub> phosphors: oil–water interface cation exchange synthesis, dual-modal luminescence and anti-counterfeiting
摘要： Efficient dual-modal luminescence is highly desired for applications in high security anti-counterfeiting. In the present work, Yb3+/Ln3+/Mn4+ (Ln = Er, Ho, and Tm) tri-doped Na3ZrF7 phosphors were fabricated via oil–water interface cation exchange using Yb3+/Ln3+:Na3ZrF7 as the exchanging hosts. The as-prepared products exhibited typical Mn4+ red down-shifting luminescence under UV light excitation and Er3+ red, Ho3+ yellow and Tm3+ near-infrared multi-color upconversion emissions under 980 nm laser excitation. The Mn4+ dopants in the Na3ZrF7 host experienced strong crystal-field strength Dq of 3.63 and showed superior thermal stability with up to 90% of the initial emission intensity retained at 448 K. Steady-state and time-resolved emission spectra verified that there was no detrimental energy transfer interaction between Mn4+ and Ln3+, enabling bright and eye-visible bi-functional emissions for the present products. As a consequence, the as-prepared phosphors were demonstrated to be applicable in anti-counterfeiting by a proof of concept experiment of fluorescent labeling for specially designed patterns.
关键词： phosphors,upconversion,anti-counterfeiting,cation exchange,dual-modal luminescence
更新于2025-11-20 15:33:11
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Ultra-small colloidal heavy-metal-free nanoplatelets for efficient hydrogen generation
摘要： Metal chalcogenide semiconducting nanoplatelets exhibit a broad absorption spectrum, as well as thickness-dependent optical and electronic properties. As such, they may be used as building blocks in a variety of optoelectronic devices. The direct synthesis of heavy-metal-free ultra-small sized nanoplatelets is still challenging, due to the inherent limits in existing synthetic approaches. Here, we report an efficient template-assisted cation-exchange route to synthesize heavy metal free metal chalcogenide nanoplatelets that are optically active in the near infrared. The SnSe nanoplatelets, whose lateral dimension is 6-10 nm, exhibit a quantum yield of 20%. The nanoplatelets are applied as light absorbers in a photoelectrochemical (PEC) system for hydrogen generation, leading to a saturated photocurrent density of 7.4 mA/cm2, which is a record for PEC devices using heavy metal-free colloidal quantum dots or nanoplatelets under identical measurement conditions. Our results indicate that quasi-zero-dimensional SnSe nanoplatelets hold great potential as efficient light absorbers for emerging optoelectronic technologies.
关键词： nanoplatelets,cation exchange,optoelectronic technologies,SnSe,hydrogen generation
更新于2025-11-19 16:51:07
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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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Adsorption and Cation Exchange Behavior of Zinc Sulfide (ZnS) on Mesoporous TiO2 Film and Its Applications to Solar Cells
摘要： Zinc sulfide (ZnS) was deposited onto the surface of mesoporous TiO2 film by a typical successive ionic layer adsorption and reaction (SILAR) process. By inducing a spontaneous cation exchange between ZnS and a target cation (Pb2+, Cu2+, Ag+, or Bi3+) dissolved in chemical bath when they are in contact, it was demonstrated successfully that white translucent ZnS on the substrate could be changed to brown-colored new metal chalcogenides and the amount of ZnS deposited originally by different conditions could be compared in a qualitative way with the degree of the color change. By utilizing this simple but effective process, the evolution of well-known ZnS passivation layer prepared from different chemical baths in quantum dot (QD)-sensitized solar cells could be tracked visually via checking the degree of color change of TiO2/ZnS electrodes after the induced specific cation exchange. When applied to representative CdS QD-sensitized solar cells, it was revealed clearly how the different degree and rate of ZnS deposition could affect the overall power conversion efficiency while finding an optimized passivation layer over TiO2/CdS electrode. Acetate anion-coupled Zn2+ source was observed to give a much faster deposition of ZnS passivation layer than nitrate anion one due to its higher pH-induced more favorable adsorption of Zn2+ on the surface of TiO2. As another useful application of the ZnS-based cation exchange, as-deposited ZnS was used as a template for preparing a more complex metal chalcogenide onto mesoporous TiO2 film. The ZnS-derived Sb2S3-sensitized electrode showed a promising initial result of over 1.0 % overall power conversion efficiency with a very thin ZrO2 passivation layer between TiO2 and Sb2S3.
关键词： passivation,Quantum dot-sensitizer,SILAR deposition,zinc sulfide,solar cell,cation exchange
更新于2025-09-23 15:21:01
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Potential Application of Lasera??Induced Breakdown Spectroscopy (LIBS) Data for the Determination of Cation Exchange Capacity (CEC) of Agricultural Soils
摘要： The potential for Laser Induced Breakdown Spectroscopy (LIBS) technique to predict cation exchange capacity (CEC) values in agricultural soils, based on a partial least square (PLS) regression model, was investigated by analysing soils (N = 225) using a portable LIBS system. The prediction from the validation set was 0.75 and the RMSE was 5.4 cmol + /kg. Analysis of the PLS loading weights showed that emission lines that correlate with the exchangeable cations (Ca, Mg, K and Na) and clay (Al and Si) are significant. Good quality predictions could be obtained from the model as described by the ratio of performance to deviation (RPD) values calculated for calibration (RPDc = 1.99) and validation (RPDv = 2.02). The ratio of performance to interquartile distance (RPIQ) for calibration (RPIQc = 3.20) and validation (RPIQv = 3.32) indicated excellent prediction capability. It has been demonstrated that LIBS spectra coupled with multivariate data analysis could be used to predict CEC of agricultural soils which is considered fast and a chemical-free technique.
关键词： cation exchange capacity,agricultural soil,analytical chemistry,spectroscopic method,laser induced-breakdown spectroscopy
更新于2025-09-23 15:21:01
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Surface passivation enabled-structural engineering of I-III-VI <sub/>2</sub> nanocrystal photocatalysts
摘要： Cation exchange has evolved into a powerful tactic for synthesis of semiconductor nanocrystals (NCs) that are not readily accessible otherwise. Here we have investigated the In3+-for-Cu+ cation exchange in the dodecahedral-shaped Cu7S4 NCs and found that surface passivation, either caused by excess guest cations or ligand molecules, can be exploited to engineer the structural properties of the NCs. By monitoring the parallel reactions carried out under systematically varied conditions, together with the positron annihilation spectroscopy investigation, we have demonstrated that the key element accounting for the observed surface passivation is associated with the copper vacant sites on the surface of Cu7S4 NCs. The reduction in In3+/Cu+ ratio and the presence of strong-binding ligands could enhance the density of surface copper vacancies and boost cation exchange reaction, which therefore alters the competition between the in-di?usion of In3+ and out-di?usion of Cu+ ions. Such capability to control the inter-di?usion balance in cation exchange (and the accompanying Kirkendall e?ect) enables the creation of a series of CuInS2 (and Cu7S4@CuInS2) NCs with various exotic structures, which show di?erent photocatalytic abilities in singlet oxygen generation. This study can not only add more structural complexity and diversity to the semiconductor NCs achievable by cation exchange, but also presents an important guideline for establishing a unifying mechanistic understanding of the reaction kinetics in cation exchange process.
关键词： cation exchange,Kirkendall effect,semiconductor nanocrystals,photocatalysis,surface passivation
更新于2025-09-23 15:21:01
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Cation Exchange as a Mechanism to Engineer Polarity in Layered Perovskites.
摘要： Cation exchange reactions performed on the n = 2 Dion-Jacobson phases RbNdNb2O7 and RbNdTa2O7, using LiNO3 and NaNO3, yield the corresponding LiNdM2O7 and NaNdM2O7 (M = Nb, Ta) phases. Synchrotron X-ray and neutron powder diffraction data, in combination with second-harmonic generation data and supported by first-principles DFT calculations, reveal that the LiNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉaˉc+/-(aˉaˉc+) distortion described in the polar space group B2cm. In contrast, the NaNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉb0c0/b0aˉc0 distortion, described in the centrosymmetric space group P42/mnm. The differing structures adopted by the LiNdM2O7 and NaNdM2O7 phases are rationalized on the basis of a competition between i) optimizing the size of the Li/Na coordination site via octahedral tilting and ii) ordering the Na/Li cations within the (Li/Na)O2 sheets to minimize cation-cation repulsion – the former appears to be the dominant factor for the Li phases and the latter factor dominates for the Na phases. The strong A’-cation dependence of the tilting distortions adopted by the A’NdM2O7 phases suggests that by careful selection of the substituting cation the tilting distortions of layered perovskite phases can be rationally tuned to adopt polar configurations, and thus new ferroelectric phases can be synthesized.
关键词： Layered perovskites,Cation exchange,Structural distortion,Ferroelectric materials,Polarity engineering
更新于2025-09-23 15:21:01
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From core-shell to yolk-shell: Keeping the intimately contacted interface for plasmonic metal@semiconductor nanorods toward enhanced near-infrared photoelectrochemical performance
摘要： Here we report a synthetic strategy for controllable construction of yolk-shell and core-shell plasmonic metal@semiconductor hybrid nanocrystals through modulating the kinetics of sulfurization reaction followed by cation exchange. The yielded yolk-shell structured products feature exceptional crystallinity and more importantly, the intimately adjoined and sharp interface between plasmonic metal and semiconductor which facilitates efficient charge carrier communications between them. By exploiting the system composed of Au nanorods and p-type PbS as a demonstration, we show that the Au@PbS yolk-shell nanorods manifest notable improvement in visible and near infrared light absorption compared to the Au@PbS core-shell nanorods as well as hollow PbS nanorods. Moreover, the photocathode constituted by Au@PbS yolk-shell nanorods affords the highest photoelectrochemical activities both under simulated sunlight and λ > 700 nm light irradiation. The superior performance of Au@PbS yolk-shell nanorods is considered arising from the combination of the favorable structural advantages of yolk-shell configuration and the surface plasmon resonance enhancement effect. We envision that the reported synthetic strategy can offer a valuable means to create hybrid nanocrystals with desirable structures and functions that enable to harness the photogenerated charge carriers, including the plasmonic hot holes, in wide-range solar-to-fuel conversion.
关键词： solar-to-fuel conversion,cation exchange,surface plasmon resonance,core-shell,yolk-shell
更新于2025-09-23 15:19:57
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CuInS <sub/>2</sub> -Doped ZnS Quantum Dots Obtained via Non-Injection Cation Exchange Show Reduced but Heterogeneous Blinking and Provide Insights into Their Structurea??Optical Property Relationships
摘要： Cadmium-free CuInS2-doped ZnS quantum dots (QDs) are synthesized through a 2-step non-injection synthetic method. The resulting QDs are small (8 nm or less) and relatively isotropic with photoluminescence quantum yields (PL QY) up to almost 70% and emission peaks in the 560-600 nm window, depending on the amount of Zn precursor added. The results indicate small CuInS2 ‘clusters’ within a zinc-blende ZnS lattice are the radiative recombination centers in the nanoparticle. Interestingly, higher ensemble photoluminescence quantum yields (PL QY) result when cation exchange is less extensive (~80 % ZnS composition), while a reduction in blinking is observed when ZnS composition exceeds 99%. A wide heterogeneity in blinking behavior from QD-to-QD is evident and a subpopulation statistical analysis shows that the on-state dwell times change from multiexponential (or inverse power law) behavior towards more mono-exponential behavior for particles that spend more of their time in the on-state. These results indicate that, as the number of CuInS2 emitting centers is reduced, the number of pathways leading to the off-state decreases, and a model is proposed to relate this behavior to the QD structure. These results provide a novel route towards CuInS2-doped visible-light emitting ZnS QDs with high quantum yield and reduced blinking and provides insight into how the composition of dopant and host matrix affects the radiative recombination mechanisms in single particles.
关键词： non-injection cation exchange,CuInS2-doped ZnS,blinking,structure-optical property relationships,quantum dots
更新于2025-09-23 15:19:57
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Morphology Transformation of Chalcogenide Nanoparticles Triggered by Cation Exchange Reactions
摘要： Plenty of chalcogenide families with tremendous potential for functional applications remain unexplored due to the limitations of conventional synthesis methods. However, cation exchange reactions in colloidal synthesis offer an alternative way to overcome these limitations and provide a route to synthesize pure phases and morphologies that otherwise are challenging to achieve. In this work, we demonstrate the possibility of Sb3+ to undergo cation exchange reactions with Cu+ in Cu2-xSe nanoparticles and study an uncommon morphology transformation from Cu2-xSe nanoparticles to Cu3SbSe3 nanoplates. The morphology transformation is dictated by a growth process of assembly and merging of primary nanoparticles triggered by the incorporation of Sb cations into the Cu2-xSe lattice and the rearrangement of the anion framework. By studying this unprecedented phenomenon in cation exchange reactions and adding Sb to the list of available elements for exchange, this work provides an insight of the unexplored potential of cation exchange reactions and opens the possibility to synthesize complex Cu-based chalcogenide materials.
关键词： nanoparticles,chalcogenide,morphology transformation,cation exchange,Cu3SbSe3 nanoplates
更新于2025-09-23 15:19:57