On the Precise and Continuous Regulation of the Superatomic and Spectroscopic Behaviors of the Quasi-Cubic W₄C₄ Cluster by the Oriented External Electric Field

Designing and realizing novel superatoms with controllable and tunable electronic properties is vital for their potential applications in cluster-assembly nanomaterials. Here, we investigated the effect of the oriented external electric field (OEEF) on the geometric and electronic structures as well as the spectroscopic properties of the quasi-cubic W4C4 cluster by utilizing the density functional theory (DFT) calculations. Compared with traditional models, the OEEF was observed to hold the special capability in continuously and precisely modulating the electronic properties of W4C4, that is, remarkably increasing its electron affinity (EA) (1.58 eV) to 5.61 eV under the 0.040 au OEEF (larger than any halogen atoms in the periodic table), which possesses the superhalogen behavior. Furthermore, the downward movement of the lowest unoccupied molecular orbital level of the cluster accompanied by the enhancement of the OEEF intensity was demonstrated to be the origin of the EA increment. Additionally, the photoelectron spectra (PES) of W4C4– were also simulated under different OEEF intensities, where the PES peaks move to a higher energy area following the enhancement of the OEEF strength, exhibiting the blue-shift behavior. These findings observed here open a new avenue in conveniently and precisely adjusting the electronic properties of clusters, which will be beneficial for the rational design of superatoms or superatom-assembled nanomaterials under the external field

S‑P Coupling Induced Unusual Open-Shell Metal Clusters

Metal clusters featuring closed supershells or aromatic character usually exhibit remarkably enhanced stability in their cluster series. However, not all stable clusters are subject to these fundamental constraints. Here, by employing photoelectron imaging spectroscopy and ab initio calculations, we present experimental and theoretical evidence on the existence of unexpectedly stable open-shell clusters, which are more stable than their closed-shell and aromatic counterparts. The stabilization of these open-shell Al-Mg clusters is proposed to originate from the S-P molecular orbital coupling, leading to highly stable species with increased HOMO–LUMO gaps, akin to s-p hybridization in an organic carbon atom that is beneficial to form stable species. Introduction of the coupling effect highlighted here not only shows the limitations of the conventional closed-shell model and aromaticity but also provides the possibility to design valuable building blocks

Dual External Field-Engineered Hyperhalogen

Hyperhalogens, a superatom featuring the highest known electron affinity (EA), have promising applications in the synthesis of superoxidizers. Contributions regarding the identified numbers and corresponding design strategies of hyperhalogens, however, are scarce. Herein, a novel and noninvasive dual external field (DEF) strategy, including the ligand field and oriented external electric field (OEEF), is proposed to construct hyperhalogens. The DEF strategy was shown to possess the power to increase Au8’s EA, forming the hyperhalogen. Strikingly, the ligation process can increase the cluster’s stability, while OEEF can realize the precise and continuous regulation of the cluster’s EA. Moreover, besides the model Au8 system, an experimentally synthesized Ag17 nanocluster was also investigated, further demonstrating the reliability of the proposed strategy. Considering the crucial role of ligands in the liquid synthesis of clusters and the convenient source of OEEF, such a DEF strategy may greatly increase the synthesis and applications of hyperhalogens in the condensed phase

Ladder Oxygenation of Group VIII Metal Clusters and the Formation of Metalloxocubes M₁₃O₈⁺

The diversity of valence and bonding of transition metals makes their oxidation processes perplexing at reduced sizes. Here we report a comprehensive study on the oxidation reactions of rhodium clusters Rhn± (n = 3–30) and find that Rh3,4O4+, Rh5–7O6+, and Rh8–13O8+ always dominate the mass distributions showing size-dependent ladder oxygenation which is closely associated with the O-binding modes. While the Rh8–13O8+ clusters display a μ3-O binding mode (hollow site adsorption), Rh3–4O4+ and Rh5–7O6+ favor the μ2-O binding mode (edge-site adsorption) or a mixture of the two modes. The μ3-O binding mode is inclined to yield a cubic Rh13O8, while the μ2-O binding mode gives rise to oxygen-bridge protection for the metal clusters. Such ladder oxidation was also observed for Ptn+, Fen+, Con+, and Nin+ clusters. We propose a three-dimensional diagram for the oxidation states and O-binding modes of metals, and highlight the metalloxocubes M13O8+ for cluster-genetic materials

Ladder Oxygenation of Group VIII Metal Clusters and the Formation of Metalloxocubes M₁₃O₈⁺

The diversity of valence and bonding of transition metals makes their oxidation processes perplexing at reduced sizes. Here we report a comprehensive study on the oxidation reactions of rhodium clusters Rhn± (n = 3–30) and find that Rh3,4O4+, Rh5–7O6+, and Rh8–13O8+ always dominate the mass distributions showing size-dependent ladder oxygenation which is closely associated with the O-binding modes. While the Rh8–13O8+ clusters display a μ3-O binding mode (hollow site adsorption), Rh3–4O4+ and Rh5–7O6+ favor the μ2-O binding mode (edge-site adsorption) or a mixture of the two modes. The μ3-O binding mode is inclined to yield a cubic Rh13O8, while the μ2-O binding mode gives rise to oxygen-bridge protection for the metal clusters. Such ladder oxidation was also observed for Ptn+, Fen+, Con+, and Nin+ clusters. We propose a three-dimensional diagram for the oxidation states and O-binding modes of metals, and highlight the metalloxocubes M13O8+ for cluster-genetic materials

Dynamics of OH Formation in the Photodissociation of <i>o</i>-Nitrobenzoic Acid at 295 and 355 nm

Photodissociation dynamics of o-nitrobenzoic acid at 295 and 355 nm is studied by probing the nascent OH photoproduct employing the single-photon laser-induced fluorescence technique. At both of the photolysis wavelengths, the OH fragments are found to be vibrationally cold but have different rotational state distributions. Upon photolysis at 295 nm, the relative population of OH in different rotational states does not follow the Boltzmann equilibrium distribution, whereas upon photolysis at 355 nm, a Boltzmann distribution is observed with a rotational temperature of 1010 ± 100 K. Between the two spin−orbit states, 2Π3/2 and 2Π1/2, the former is found to be preferentially populated, and the distribution of the Π(A′) state for the Λ-doublet is dominant at both of the wavelengths studied. Several possible dissociation pathways of o-nitrobenzoic acid leading to formation of the OH fragment are investigated computationally. On the basis of the theoretical and experimental studies, a possible mechanism of OH formation from the photodissociation of o-nitrobenzoic acid at 295 and 355 nm is proposed

Tuning the Electronic Properties and Performance of Low-Temperature CO Oxidation of the Gold Cluster by Oriented External Electronic Field

Conventional electronic rules, including Jellium and Wade–Mingos rules and so on, have long been successfully dedicated to design superatoms. These rules, however, rely on altering the intrinsic properties, for example, the compositions or the number of valence electrons, of clusters, which is relatively complicated and inconvenient to manipulate, especially in experiments. Herein, by employing density functional theory calculations, the oriented external electric field (OEEF) was demonstrated to possess the capability of precisely and continuously regulating the electronic properties of clusters at will, representing a novel and noninvasive methodology in constructing stable superatoms because it hardly changes the geometries of clusters. More interestingly, the active sites formed by the charge redistribution upon the introduction of an OEEF could significantly promote the catalytic performance of the low-temperature CO oxidation over clusters. Considering the convenient source of the OEEF, the findings highlighted here may boost the potential applications of superatom-assembly nanomaterials in catalysis and materials science

Filling Mesopores of Conductive Metal–Organic Frameworks with Cu Clusters for Selective Nitrate Reduction to Ammonia

The electrocatalytic nitrate reduction reaction (NO3–RR) to ammonia (NH3) under ambient conditions not only has the benefit of lowering energy consumption, but also helps remove nitrate contamination. Inspired by the unique structure of nitrate/nitrite reductase with the active spheroproteins encapsulated by larger enzymes, herein, we develop an in situ synthetic strategy for the construction of metal cluster–conductive metal–organic framework (MOF) composite electrocatalysts. The metallic Cu clusters are filled into the mesopores of a conductive copper-based MOF (i.e., CuHHTP); meanwhile, CuHHTP with a porous structure provides an internal environment to limit the growth of metallic Cu clusters with an ultrasmall size (i.e., 1.5 ± 0.2 nm) and restrains their aggregation. The obtained Cu@CuHHTP exhibits superb performance for NO3–RR. In a neutral electrolyte with 500 ppm NO3–, Cu@CuHHTP shows a high NO3– conversion of 85.81% and a selectivity for NH3 of 96.84%. 15N isotope labeling experiments confirm that the formation of NH3 originates from the process of NO3–RR. Theoretical calculations confirm that Cu clusters are the active sites in the composite electrocatalysts, in which the proper d-band center and the “accept–donate” mechanism in charge transfer are the key factors for the improvement of the electrocatalytic performance

Construction of Highly Efficient Resonance Energy Transfer Platform Inside a Nanosphere for Ultrasensitive Electrochemiluminescence Detection

Electrochemiluminescence (ECL) detection has attracted increasing attention as a promising analytical approach. A considerable number of studies showed that ECL intensity can be definitely improved by resonance energy transfer (RET), while the RET efficiency is strongly dependent on the distance between exited donors and acceptors. Herein we disclose for the first time a highly enhanced RET strategy to promote the energy transfer efficiency by coencapsulating the donor ([Ru­(bpy)₃]²⁺)/acceptor (CdTe quantum dots, CdTe QDs) pairs into a silica nanosphere. Plenty of [Ru­(bpy)₃]²⁺ and CdTe QDs closely packed inside a single nanosphere greatly shortens the electron-transfer path and increases the RET probability, therefore significantly enhancing the luminous efficiency. Further combining with molecularly imprinting technique, we develop a novel ECL sensor for ultrasensitive and highly selective detection of target molecules. Proof of concept experiments showed that extremely low detection limits of subfg/mL (S/N = 3) with broad linear ranges (fg/mL to ng/mL) could be obtained for detection of two kinds of mycotoxins (α-ergocryptine and ochratoxin A) that are recognized as potential health hazards at very low concentrations. This strategy combining enhanced RET system and molecularly imprinting technique, represents a versatile ECL platform toward low-cost, rapid, ultrasensitive, and highly selective detection of target molecules in diverse applications