Semiconductor Nanoclusters Research Articles

Atomically precise Cu32 nanoclusters with selenide doping: Synthesis, bonding, and catalysis

AbstractCopper nanoclusters with stable compositions and precise structures have long been sought after, as they possess properties that are absent in gold and silver counterparts. However, the creation of copper nanoclusters with novel compositions, structures, and functionalities remains largely unexplored in the literature. In this study, we demonstrate that selenide doping is an effective method for fabricating stable copper nanostructures through controlled synthesis and structure determination of a copper–selenide nanocluster. The nanocluster of [Cu32Se7(BnSe)18(PPh3)6]+ (denoted as Cu32Se7, Bn is benzyl) has been prepared by reducing copper salts in the presence of organic diselenides. The atomic structure of the Cu32Se7 cluster, accurately determined through single‐crystal X‐ray diffraction, reveals a core–shell arrangement of Cu20Se7@Cu12(BnSe)18(PPh3)6, where Se2− anions are well dispersed in the Cu20 framework. Notably, this cluster represents a rare example of copper–selenide semiconductor nanoclusters. Experimental and theoretical analysis shows strong interactions between Se ligands and metal atoms, resulting in high stability of the Cu32Se7 cluster. Furthermore, the cluster exhibits excellent catalytic performance in the hydroboration reaction of alkynes, producing a range of vinylboron compounds with adjustable structures and functions. Importantly, the cluster undergoes no structural or nuclearity changes during the reaction, as confirmed by extended X‐ray absorption fine structure and X‐ray photoelectron spectroscopy studies. This study not only presents a molecular cluster model highlighting the effectiveness of selenide dopants in fabricating new copper nanostructures but also paves the way for utilizing stable copper nanoclusters in diverse and exciting areas beyond catalysis.

Synthesis and Single Crystal X-ray Diffraction Structure of an Indium Arsenide Nanocluster.

The discovery of magic-sized clusters as intermediates in the synthesis of colloidal quantum dots has allowed for insight into formation pathways and provided atomically precise molecular platforms for studying the structure and surface chemistry of those materials. The synthesis of monodisperse InAs quantum dots has been developed through the use of indium carboxylate and As(SiMe3)3 as precursors and documented to proceed through the formation of magic-sized intermediates. Herein, we report the synthesis, isolation, and single-crystal X-ray diffraction structure of an InAs nanocluster that is ubiquitous across reports of InAs quantum dot synthesis. The structure, In26As18(O2CR)24(PR'3)3, differs substantially from previously reported semiconductor nanocluster structures even within the III-V family. However, it can be structurally linked to III-V and II-VI cluster structures through the anion sublattice. Further analysis using variable temperature absorbance spectroscopy and support from computation deepen our understanding of the reported structure and InAs nanomaterials as a whole.

A High-Nuclearity Copper Sulfide Nanocluster [S-Cu50] Featuring a Double-Shell Structure Configuration with Cu(II)/Cu(I) Valences.

This work represents an important step in the quest for creating atomically precise binary semiconductor nanoclusters (BS-NCs). Compared with coinage metal NCs, the preparation of BS-NCs requires strict control of the reaction kinetics to guarantee the formation of an atomically precise single phase under mild conditions, which otherwise could lead to the generation of multiple phases. Herein, we developed an acid-assisted thiolate dissociation approach that employs suitable acid to induce cleavage of the S-C bonds in the Cu-S-R (R = alkyl) precursor, spontaneously fostering the formation of the [Cu-S-Cu] skeleton upon the addition of extra Cu sources. Through this method, a high-nuclearity copper sulfide nanocluster, Cu50S12(SC(CH3)3)20(CF3COO)12 (abbreviated as [S-Cu50] hereafter), has been successfully prepared in high yield, and its atomic structure was accurately modeled through single-crystal X-ray diffraction. It was revealed that [S-Cu50] exhibits a unique double-shell structural configuration of [Cu14S12]@[Cu36S20], and the innermost [Cu14] moiety displays a rhombic dodecahedron geometry, which has never been observed in previously synthesized Cu metal, hydride, or chalcogenide NCs. Importantly, [S-Cu50] represents the first example incorporating mixed Cu(II)/Cu(I) valences in reported atomically precise copper sulfide NCs, which was unambiguously confirmed by XPS, EPR, and XANES. In addition, the electronic structure of [S-Cu50] was established by a variety of optical investigations, including absorption, photoluminescence, and ultrafast transient absorption spectroscopies, as well as theoretical calculations. Moreover, [S-Cu50] is air-stable and demonstrates electrocatalytic activity in ORR with a four-electron pathway.

Periplasmic biomineralization for semi-artificial photosynthesis.

Semiconductor-based biointerfaces are typically established either on the surface of the plasma membrane or within the cytoplasm. In Gram-negative bacteria, the periplasmic space, characterized by its confinement and the presence of numerous enzymes and peptidoglycans, offers additional opportunities for biomineralization, allowing for nongenetic modulation interfaces. We demonstrate semiconductor nanocluster precipitation containing single- and multiple-metal elements within the periplasm, as observed through various electron- and x-ray-based imaging techniques. The periplasmic semiconductors are metastable and display defect-dominant fluorescent properties. Unexpectedly, the defect-rich (i.e., the low-grade) semiconductor nanoclusters produced in situ can still increase adenosine triphosphate levels and malate production when coupled with photosensitization. We expand the sustainability levels of the biohybrid system to include reducing heavy metals at the primary level, building living bioreactors at the secondary level, and creating semi-artificial photosynthesis at the tertiary level. The biomineralization-enabled periplasmic biohybrids have the potential to serve as defect-tolerant platforms for diverse sustainable applications.

Deciphering the electrochemical sensing capability of novel Ga12As12 nanocluster towards chemical warfare phosgene gas: insights from DFT.

The applications of 3D inorganic nanomaterials in environmental and agriculture monitoring have been exploited continuously; however, the utilization of semiconductor nanoclusters, especially for detecting warfare agents, has not been fully investigated yet. To fill this gap, the molecular modelling of novel inorganic semiconductor nanocluster Ga12As12 as a sensor for phosgene gas (highly toxic for living things and the environment) is accomplished employing benchmark DFT and TD-DFT investigations. Computational tools have been applied to explore different adsorption sites and the potential sensing capability of the Ga12As12 nanoclusters. The calculated adsorption energy (-21.34 ± 2.7 kcal mol-1) for ten selected complexes, namely, Pgn-Cl@4m-ring (MS1), Pgn-Cl@6m-ring (MS2), Pgn-Cl@XY66 (MS3), Pgn-O@4m-ring (MS4), Pgn-O@XY66 (MS5), Pgn-O@XY64 (MS6), Pgn-O@Y (MS7), Pgn-planar@Y (MS8), Pgn-planar@X (MS9), and Pgn-planar@4m-ring (MS10), manifest the remarkable and excessive adsorption response of the studied nanoclusters. The explored molecular electronic properties, such as interaction distance (3.05 ± 0.5 Å), energy gap (∼2.17 eV), softness (∼0.46 eV), hardness (1.10 ± 0.01 eV), electrophilicity index (10.27 ± 0.45 eV), electrical conductivity (∼1.98 × 109), and recovery time (∼3 × 10-12 s-1) values, ascertain the elevated reactivity and an imperishable sensitivity of the Ga12As12 nanocluster, particularly for its complex MS8. QTAIM analysis exhibits the presence of a strong electrostatic bond (positive ∇2ρ(r) values), electron delocalization (ELF < 0.5), and a strong chemical bond (because of high all-electron density values). In addition, NBO analysis explores the lone pair electron delocalization of phosgene to the nanocluster stabilized by intermolecular charge transfer (ICT) and different kinds of non-covalent interactions. Also, the green region existence expressed by NCI analysis (between the nanocluster and adsorbate) stipulate the energetic and dominant interactions. Furthermore, the UV-Vis, thermodynamic analysis, and density of state (DOS) demonstrate the maximum absorbance (562.11 nm) and least excitation energy (2.21 eV) by the complex MS8, the spontaneity of the interaction process, and the significant changes in HOMO and LUMO energies, respectively. Thus, the Ga12As12 nanocluster has proven to be a promising influential sensing material to monitor phosgene gas in the real world, and this study will emphasize the informative knowledge for experimental researchers to use Ga12As12 as a sensor for the warfare agent (phosgene).

The interface microenvironment mediates the emission of a semiconductor nanocluster via surface-dopant-involving direct charge transfer.

The interface microenvironment of doped quantum dots (QDs) is crucial in optimizing the properties associated with the photogenerated excitons. However, the imprecision of QDs' surface structures and compositions impedes a thorough understanding of the modulation mechanism caused by the complex interface microenvironment, particularly distinguishing the contribution of surface dopants from inner ones. Herein, we investigated interface-mediated emission using a unique model of an atomically precise chalcogenide semiconductor nanocluster containing uniform near-surface Mn2+ dopants. Significantly, we discovered that Mn2+ ions can directly transfer charges with hydrogen-bonding-bound electron-rich alkylamines with matched molecular configurations and electronic structures at the interface. This work provides a new pathway, the use of atomically precise nanoclusters, for analyzing and enhancing the interface-dependent properties of various doped QDs, including chalcogenides and perovskites.

A review of II–VI semiconductor nanoclusters for photocatalytic CO2 conversion: synthesis, characterization, and mechanisms

In this review, we briefly overview the syntheses, compositions, growth mechanisms, and performance improvement strategies of typical II–VI MSCs. Recent advances on the application of II–VI MSCs in photocatalytic CO2 reduction are introduced.

Theoretical studies on the two-photon absorption of II\u2013VI semiconductor nano clusters

Semiconductor clusters, ZnnOn, ZnnSn, and CdnSn (n = 2–8), were optimized and the corresponding stable structures were acquired. The symmetry, bond length, bond angle, and energy gap between HOMO and LUMO were analyzed. According to reasonable calculation and comparative analysis for small clusters Zn2O2, Zn2S2, and Cd2S2, an effective method based on density function theory (DFT) and basis set which lay the foundation for the calculation of the large clusters have been obtained. The two-photon absorption (TPA) results show that for the nano clusters with planar configuration, sizes play important role on the TPA cross section, while symmetries determine the TPA cross section under circumstance of 3D stable structures. All our conclusions provide theoretical support for the development of related experiments.

Nanoconfinement‐Controlled Synthesis of Highly Active, Multinary Nanoplatelet Catalysts from Lamellar Magic‐Sized Nanocluster Templates

AbstractMagic‐sized semiconductor nanoclusters (MSCs) possessing intermediate stability are promising precursors for synthesizing low‐dimensional nanostructures that cannot be achieved by direct methods. However, uncontrolled diffusion of MSCs in their colloidal‐state poses challenges in utilizing them as precursors and/or templates for the controlled synthesis of nanomaterials. Herein, a nanoconfined diffusion‐limited strategy to synthesize large CdSe nanoplatelets through the solid‐state transformation of (CdSe)13 MSCs is designed, wherein MSCs serve as both precursors and lamellar bilayer templates. In sharp contrast, in the colloidal‐state, these MSCs are grown to CdSe nanoribbons or nanorods. Furthermore, the nanoconfined route is used not only to transform (CdSe)13, Mn2+:(CdSe)13, and Mn2+:(Cd1−xZnxSe)13 MSCs but also to dope Cu+, producing Cu+:CdSe, Mn2+/Cu+:CdSe, Mn2+/Cu+:Cd1−xZnxSe nanoplatelets, respectively. The resulting multinary nanoplatelets with controlled compositions exhibit unique optical and magneto‐optical properties through characteristic exciton transfer mechanisms. Furthermore, synergistic effects have made quinary Mn2+/Cu+:Cd0.5Zn0.5Se nanoplatelets efficient and reusable catalysts for chemical fixation of CO2 with epoxide (turnover frequency: ≈200/h) under mild conditions. This nanoconfined synthetic strategy paves the way to synthesize diverse shape‐controlled multi‐component nanostructures for optoelectronic and other catalytic applications.

Computational approach to (ZnS)_{i} nanoclusters in ionic liquids.

Unique and attractive properties have been predicted for II-VI-type semiconductor nanoclusters within the field of nanotechnology. However, the low reaction kinetics within the usual solvents gives only thermodynamic control during their production process, making the obtention of different metastable polymorphs extremely difficult. The use of ionic liquids as solvents has been proposed to overcome this problem. Identifying how these nanoclusters are solvated within ionic liquids is fundamental if this strategy is to be pursued. While computational chemistry tools are best suited for this task, the complexity and size of the system requires a careful design of the simulation protocol, which is put forward in this work. Taking as reference the (ZnS)_{12} nanocluster and the [EMIM][EtSO_{4}] ionic liquid, we characterize the interactions between the nanoparticle and first solvation shell by density functional theory calculations, considering most of the solvent implicitly. The DFT results are consistent through different theory levels showing a strong interaction between the Zn atoms of the nanocluster and the [EtSO_{4}^{-}] anion of the ionic liquid. A more realistic representation of the system is obtained by classical MD calculations, for which various classical force fields were considered and several atomic interactions parameterized. This new set of parameters correctly describes the interaction of different (ZnS) nanoclusters, supporting its transferability. The resulting MD simulation shows the formation of a structured ionic liquid solvation shell around the nanocluster with no exchange of ions for at least 5ns, in agreement with the strong interactions observed in the density functional theory calculations.

Magic clusters are better together.

Hybrid materials constructed from the assembly of inorganic building blocks and organic linkers have shown unique properties and applications. Superstructures of semiconductor magic-sized nanoclusters linked by diamines now join this class of materials.

Highly luminescent and catalytically active suprastructures of magic-sized semiconductor nanoclusters.

Metal chalcogenide magic-sized nanoclusters have shown intriguing photophysical and chemical properties, yet ambient instability has hampered their extensive applications. Here we explore the periodic assembly of these nanoscale building blocks through organic linkers to overcome such limitations and further boost their properties. We designed a diamine-based heat-up self-assembly process to assemble Mn2+:(CdSe)13 and Mn2+:(ZnSe)13 magic-sized nanoclusters into three- and two-dimensional suprastructures, respectively, obtaining enhanced stability and solid-state photoluminescence quantum yields (from <1% for monoamine-based systems to ~72% for diamine-based suprastructures). We also exploited the atomic-level miscibility of Cd and Zn to synthesize Mn2+:(Cd1-xZnxSe)13 alloy suprastructures with tunable metal synergy: Mn2+:(Cd0.5Zn0.5Se)13 suprastructures demonstrated high catalytic activity (turnover number, 17,964 per cluster in 6 h; turnover frequency, 2,994 per cluster per hour) for converting CO2 to organic cyclic carbonates under mild reaction conditions. The enhanced stability, photoluminescence and catalytic activity through combined cluster-assembly and metal synergy advance the usability of inorganic semiconductor nanoclusters.

Fluorescent Cadmium Chalcogenide Nanoclusters in Ubiquitin

Fluorescent semiconductor nanoclusters (FNCs) have received much attention by many scientists due to their attractive functions and features. However, the traditional organometallic chemical synthesis routes for such FNCs require harsh reaction conditions in organic solvents, which limit their use in biological applications. Therefore, developing synthesis strategies for the fabrication of FNCs by association with proteins under mild reaction conditions is pivotal to improve their functionalities. In addition, understanding the effect of structural and chemical properties of proteins on the synthesis mechanism of FNCs is one of the key points, which eventually enables to control and tune the photophysical properties of FNCs. The purpose of this study is to introduce the syntheses of cadmium selenide nanocluster (CdSeNC) and cadmium sulfide nanocluster (CdSNC) by using ubiquitin, a small cysteine‐free protein, and investigating their properties via spectroscopic and microscopic methods. It is shown that significant changes in the protein structure as well as in its oligomerization occur upon the formation of the highly hydrated FNCs.

Influence of fast neutron irradiation on the phase composition and optical properties of homogeneous SiOx and composite Si–SiOx thin films

Layers and devices utilizing semiconductor nanocrystals have been the subjects of intensive research due to applications in opto- and microelectronic devices, solar cells, detectors, memories and in many more fields. We have shown previously that those nanocrystals in dielectric matrices undergo a substantial reformation during electron irradiation. The research of the interaction between semiconductor nanoclusters and irradiation is important for both the intentional modification of the structures and for understanding the stability of those devices under harsh, radiative conditions (e.g. space, nuclear, medical diagnosis, or similar applications). In the present research, we investigated the influence of neutron irradiation on substoichiometric silicon oxide. We investigated both homogeneous case and inhomogeneous case of matrices with silicon nanoclusters. We found that a fast neutron flux of 5.5 × 1013 neutrons/cm2 s and a fluence of 3.96 × 1017 neutrons/cm2 induce phase separation in the homogeneous films, whereas it decreases the volume fraction of the amorphous silicon phase caused by the reducing size of amorphous nanoclusters in the inhomogeneous films.

Enhanced Water Dispersibility of Discrete Chalcogenide Nanoclusters with a Sodalite-Net Loose-Packing Pattern in a Crystal Lattice

Good aqueous dispersibility of metal chalcogenide nanoclusters with an atomically precise structure is desirable to achieve tiny and uniform cluster-based "quantum dots". However, there are big challenges toward this goal, especially for the large-sized nanoclusters without covalently bonded organic ligands, because the strong electrostatic interactions between closely packed negatively charged nanoclusters and protonated organic amine templates in the crystal lattice impede the dispersion of cluster-based bulk crystalline samples. Here, we report two iso-structured crystalline metal chalcogenides composed of discrete supertetrahedral T4-MInS nanoclusters with the formulas of [M4In16S35]14- (denoted ISC-16-MInS, M = Zn and Fe), which adopt a sodalite-net loose-packing pattern in the crystal lattice and display superior dispersibility in water and some organic solvents as compared to other cases composed of the same type of nanoclusters with close-packing pattern. The dispersed T4-MInS nanoclusters were unexpectedly stabilized by adsorbing a certain number of H+ ions on surface S sites and simultaneously dropping partial surface S2- ions, instead of being surrounded by protonated organic amines, which was clearly verified by electrospray ionization mass spectrometry analysis. Notably, ISC-16-ZnInS behaves with superior performance on photodegradation of rhodamine B dye to ISC-16-FeInS. This is attributed to their difference in divalent-metal-directed separation efficiency of the photogenerated electrons and holes. This work holds great promise for the potential functional applications of uniformly dispersed semiconductor nanoclusters, such as cluster-based thin film devices, photoelectrodes, and photocatalysis.

On the Formation of Amorphous Ge Nanoclusters and Ge Nanocrystals in GeSixOy Films on Quartz Substrates by Furnace and Pulsed Laser Annealing

Nonstoichiometric GeO0.5[SiO2]0.5 and GeO0.5[SiO]0.5 germanosilicate glassy films are produced by the high-vacuum coevaporation of GeO2 and either SiO or SiO2 powders with deposition onto a cold fused silica substrate. Then the films are subjected to furnace or laser annealing (a XeCl laser, λ = 308 nm, pulse duration of 15 ns). The properties of the samples are studied by transmittance and reflectance spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. As shown by analysis of the Raman spectra, the GeO[SiO] film deposited at a substrate temperature of 100°C contains amorphous Ge clusters, whereas no signal from Ge–Ge bond vibrations is observed in the Raman spectra of the GeO[SiO2] film deposited at the same temperature. The optical absorption edge of the as-deposited GeO[SiO2] film corresponds to ~400 nm; at the same time, in the GeO[SiO] film, absorption is observed right up to the near-infrared region, which is apparently due to absorption in Ge clusters. Annealing induces a shift of the absorption edge to longer wavelengths. After annealing of the GeO[SiO2] film at 450°C, amorphous germanium clusters are detected in the film, and after annealing at 550°C as well as after pulsed laser annealing, germanium nanocrystals are detected. The crystallization of amorphous Ge nanoclusters in the GeO[SiO] film requires annealing at a temperature of 680°C. In this case, the size of Ge nanoclusters in this film are smaller than that in the GeO[SiO2] film. It is not possible to crystallize Ge clusters in the GeO[SiO] film. It seems obvious that the smaller the semiconductor nanoclusters in an insulating matrix, the more difficult it is to crystallize them. In the low-temperature photoluminescence spectra of the annealed films, signals caused by either defects or Ge clusters are detected.

Chemiresistive trimethylamine sensor using monolayer SnO2 inverse opals decorated with Cr2O3 nanoclusters

Two-dimensional SnO2 inverse opal (2D IO) structures with uniform surface decoration of Cr2O3 nanoclusters were prepared using a Sn-solution-dipped sacrificial polystyrene monolayer template method and were employed for chemiresistive gas-sensor applications. The responses (resistance ratio) of the pure SnO2 2D IO sensor to 5 ppm trimethylamine (TMA) and ethanol were as high as 209.5 and 242.3, representing improvements of two orders of magnitude compared with that of a dense SnO2 thin film sensor. The high gas response of the porous SnO2 IO sensor is attributed to the superior gas accessibility as well as the large chemiresistive variation at the thinnest neck region of the 2D IO structures. Further enhancements of the TMA selectivity and response were achieved by decorating the surface of the SnO2 IO structure with Cr2O3 nanoclusters. The control of the TMA-sensing characteristics of the SnO2 2D IO sensor through the decoration with Cr2O3 nanoclusters was explained by the change of the electron-depletion layer in the SnO2 particles due to the formation of the p(Cr2O3)-n(SnO2) junction, as well as the catalytic promotion of the gas-sensing reaction by Cr2O3. The oxide 2D IO films with high gas accessibility and chemiresistive neck structures are promising nanoarchitectures for gas-sensor applications, and the formation of hetero-nanostructures via decoration with different oxide semiconductor nanoclusters having dissimilar work functions and catalytic activity allows the enhancement of the selectivity toward a specific gas, as well as the gas response.

Photoluminescent Property and Regulation Mechanism of Atomically-Precise Manganese-Doped Semiconductor Nanoclusters

Photoluminescent Property and Regulation Mechanism of Atomically-Precise Manganese-Doped Semiconductor Nanoclusters

Формирование аморфных нанокластеров и нанокристаллов германия в пленках GeSi-=SUB=-x-=/SUB=-O-=SUB=-y-=/SUB=- на кварцевой подложке с использованием печных и импульсных лазерных отжигов

Abstract Nonstoichiometric GeO_0.5[SiO_2]_0.5 and GeO_0.5[SiO]_0.5 germanosilicate glassy films are produced by the high-vacuum coevaporation of GeO_2 and either SiO or SiO_2 powders with deposition onto a cold fused silica substrate. Then the films are subjected to furnace or laser annealing (a XeCl laser, λ = 308 nm, pulse duration of 15 ns). The properties of the samples are studied by transmittance and reflectance spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. As shown by analysis of the Raman spectra, the GeO[SiO] film deposited at a substrate temperature of 100°C contains amorphous Ge clusters, whereas no signal from Ge–Ge bond vibrations is observed in the Raman spectra of the GeO[SiO_2] film deposited at the same temperature. The optical absorption edge of the as-deposited GeO[SiO_2] film corresponds to ~400 nm; at the same time, in the GeO[SiO] film, absorption is observed right up to the near-infrared region, which is apparently due to absorption in Ge clusters. Annealing induces a shift of the absorption edge to longer wavelengths. After annealing of the GeO[SiO_2] film at 450°C, amorphous germanium clusters are detected in the film, and after annealing at 550°C as well as after pulsed laser annealing, germanium nanocrystals are detected. The crystallization of amorphous Ge nanoclusters in the GeO[SiO] film requires annealing at a temperature of 680°C. In this case, the size of Ge nanoclusters in this film are smaller than that in the GeO[SiO_2] film. It is not possible to crystallize Ge clusters in the GeO[SiO] film. It seems obvious that the smaller the semiconductor nanoclusters in an insulating matrix, the more difficult it is to crystallize them. In the low-temperature photoluminescence spectra of the annealed films, signals caused by either defects or Ge clusters are detected.

Energy Spotlight: New Inroads in Metal Halide Perovskite Research

As metal halide solar cells reach photoconversion efficiencies over 25%, one question that is often being asked is, “What is next?” Interestingly, there are plenty of new opportunities to explore in the perovskite world. The four articles selected for the Energy Spotlight in this issue are just a few examples to show the dynamic nature of metal halide perovskite research. New inroads are being made to explore new heterostructures and luminescent semiconductor nanoclusters, understand phase stability, and offer new insights into excited state processes. Such advances provide new avenues to further expand the scope of perovskite research, offering new areas to explore.