Metal Core Structure Research Articles

Atomically precise (AgPd)27 nanoclusters for nitrate electroreduction to NH3: Modulating the metal core by a ligand induced strategy

Electrochemical nitrate reduction reaction (eNO3–RR) to synthesize NH3 is a sustainable method to convert environmental contaminants into valuables. Pd based bimetallic nanocatalysts have demonstrated great promise as efficient catalysts, yet modulating the composition and configuration to improve the catalytic performance and achieve comprehensive mechanistic understanding remains challenging. Herein, by employing two ligands with different electron functional groups, we successfully prepared two atomically precise (AgPd)27 bimetallic clusters of Ag18Pd9(C8H4F)24 (Ag18Pd9) and Ag22Pd5(C9H10O2)26 (Ag22Pd5). The two clusters possess markedly different metal core composition and configuration, where Ag18Pd9 has a sandwich metal core structure with 9 Pd atoms located in the middle layer and Ag22Pd5 has a rod-shaped metal core structure composed of the M13 configuration with 5 Pd atoms located at the center and vertices of the M13 configuration. Unexpectedly, Ag22Pd5 exhibited remarkably superior eNO−3RR performance than Ag18Pd9. Specifically, the highest Faradaic efficiency of NH3 (FENH3) and its yield rate can reach 94.42 ​% and 1.41 ​mmol ​h−1 ​mg−1 ​at −0.6 ​V vs. RHE for Ag22Pd5, but the largest FENH3 and NH3 yield rate is only 43.86 ​% and 0.41 ​mmol ​h−1 ​mg−1 ​at −0.5 ​V vs. RHE for Ag18Pd9. The in situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) test provides the experimental evidence of the reaction intermediates hence revealing the reaction pathway, also shows that Ag22Pd5 has stronger capability for NO−3 adsorption and NH3 desorption than that of Ag18Pd9. Theoretical calculations indicate that the de-ligated clusters can expose the available AgPd bimetallic sites, synergistically serving as effective active sites and the different configurations result in significantly different catalytic activities, where the active sites in Ag22Pd5 are more favorable for NO−3 adsorption and NH3 desorption to accelerate the catalytic process.

Expanding the Toolbox of Oxidants: Controllable Etching of Ultrasmall Au Nanoparticles toward Tailorable NIR-II Luminescence and Ligand-Mediated Biodistribution and Clearance.

Oxidant-driven and controllable etching of small-sized nanoparticles (NPs, d < 3 nm) and tailorable modulation of their optical properties are challenging due to the high reactivity and complicated surface chemistry. Herein, we present a facile strategy for highly controllable oxidative etching of ultrasmall AuNPs and tailorable modulation of luminescence. The proper choice of a moderate oxidant, ClO-, could not only selectively etch the Au(I)-thiolate motifs from the nanoparticle surface at the subnanometer scale but also retained a stable metallic core structure without aggregation, which impressively prompted the wide-range luminescent switching from the visible to second near-infrared (NIR-II) region. The resultant oxidized AuNPs displayed highly luminescent NIR-II emission with a quantum yield of 3.0%, excellent monodispersed stability, ideal biocompatibility, and tunable shielding effects against protein adsorption. With those outstanding features, oxidized AuNPs could be utilized as nanoprobes for long-lasting and in vivo bioimaging of associated metabolic behaviors with distinguishable organ-specific targeting capabilities and ligand-mediated kinetics in nanoparticle clearance. These findings expand the toolbox of oxidants for the controllable synthesis of NIR-II nanoprobes and open up a path for exploring diverse ligand interactions on ultrasmall AuNPs with organs or tissues that might advance their monitoring applications for a wide range of clinically important diseases.

Structure–performance relationship of Au nanoclusters in electrocatalysis: Metal core and ligand structure

AbstractRemarkable progress has characterized the field of electrocatalysis in recent decades, driven in part by an enhanced comprehension of catalyst structures and mechanisms at the nanoscale. Atomically precise metal nanoclusters, serving as exemplary models, significantly expand the range of accessible structures through diverse cores and ligands, creating an exceptional platform for the investigation of catalytic reactions. Notably, ligand‐protected Au nanoclusters (NCs) with precisely defined core numbers offer a distinct advantage in elucidating the correlation between their specific structures and the reaction mechanisms in electrocatalysis. The strategic modulation of the fine microstructures of Au NCs presents crucial opportunities for tailoring their electrocatalytic performance across various reactions. This review delves into the profound structural effects of Au NC cores and ligands in electrocatalysis, elucidating their underlying mechanisms. A detailed exploration of the fundamentals of Au NCs, considering core and ligand structures, follows. Subsequently, the interaction between the core and ligand structures of Au NCs and their impact on electrocatalytic performance in diverse reactions are examined. Concluding the discourse, challenges and personal prospects are presented to guide the rational design of efficient electrocatalysts and advance electrocatalytic reactions.

Bimetallic Ag125Cu8 Nanocluster, Structure Determination, and Nonlinear Optical Properties.

The atomic precision of the subnanometer nanoclusters has provided sound proof on the structural correlation of metal complexes and larger-sized metal nanoparticles. Herein, we report the synthesis, crystallography, structural characterization, electrochemistry, and optical properties of a 133-atom intermetallic nanocluster protected by 57 thiolates (3-methylbenzenethiol, abbreviated as m-MBTH) and 3 chlorides, with the formula of Ag125Cu8(m-MBT)57Cl3. This is the largest Ag-Cu bimetallic cluster ever reported. Crystallographic analysis revealed that the nanocluster has a three-layer concentric core-shell structure, Ag7@Ag47@Ag71Cu8S57Cl3, and the Ag54 metal kernel adopts a D5h symmetry. The nuclei number is between that of the previously reported large silver cluster [Ag136(SR)64Cl3Ag0.45]- and the large silver-rich cluster Au130-xAgx(SR)55 (x = 98). All these three clusters bear a similar metallic core structure, while the main structural difference lies in the shell motif structures. Electron counting revealed an open electron shell with 73 delocalized electrons, which was verified by the electron paramagnetic resonance analysis. The DPV electrochemical measurement indicates a multielectron state quantization double-layer charging shape and single-electron sequential charging and discharging characteristic of the AgCu alloy cluster. In addition, the open-hole Z-scan test reveals the nonlinear optical absorption (2-3 optical absorption in the NIR-II/III region) of Ag125Cu8 nanoclusters.

Revisiting ultrasmall phosphine-stabilized rhodium-doped gold clusters AunRh (n = 5, 6, 7, 8): geometric, electronic, and vibrational properties.

Incorporation of other transition metals in Au nanoclusters has been thriving recently due to its effect on their electronic and photophysical properties. Here, the ultrasmall phosphine-stabilized Rh-doped gold clusters AunRh (n = 5, 6, 7, 8), with metal core structures represented as fragments of a rhodium-centered icosahedron, are considered. The geometric and electronic properties of these nanoclusters are revisited and analyzed using density functional theory (DFT). Moreover, infrared spectra are simulated to identify the effects of Rh doping on the clusters through vibrational properties. Peaks are assigned to breathing-like normal modes for all AuRh clusters except for Au8Rh, likely due to the presence of bound Cl ligands. Unlike their pure gold core counterparts, the % motions of both Au and Rh atoms are lower in the mixed metal clusters, suggesting more restrained metal cores by rhodium, which could result in other novel physical and chemical properties not hitherto discovered.

Influencing factor and cost optimization for service life of KR impeller

The service life of KR impeller for one steel plant in Southern China is investigated in this paper. It is shown by site investigation and comparison analysis that there is still improving potential for the service life of KR impeller, whose influencing factor includes hot water temperature, rotating speed, stirring duration, refractory of working lining, internal metal core structure, fabricating process, blade structure, hot repairing process and material, desulfurizer composition, interval time between stirrings. If technical optimization is conducted based on the influencing factor, it is predicted that the service life of KR impeller in this plant can be enhanced from 230 heats to 300 or 400 heats, saving 0.4~0.6 RMB/t hot metal.

ZIF-67 derived Co-N/C loaded graphite particles as three-dimensional electrodes to promote the efficient degradation of tetracycline in the electrocatalytic oxidation-peroxymonosulfate system: Synergistic effect of reactive oxygen species

In this study, ZIF-GP is synthesized using ZIF-67 in situ loaded GP. Co-N/C-GP is synthesized as a three-dimensional particle electrode by pyrolysis of ZIF-GP in a nitrogen atmosphere. A 3D electrocatalytic synergistic system (EO-Co-N/C-GP-PMS) is developed in combination with electrochemical oxidation (EO) and peroxymonosulfate activation (PMS). Continuous and efficient degradation of tetracycline (TC) is achieved through advanced oxidation processes (AOPs). The synthesis of ZIF-GP gives three-dimensional particle electrodes a controllable shape. Co-N/C-GP derived from pyrolysis has excellent stability and electrochemical catalytic properties due to its metal core structure encased in surface carbon and nitrogen layer. It is noteworthy that two cobalt species, Co NPs (Co0) and Co-N (Co3+/Co2+ in the N coordination), are identified on Co-N/C-GP, which is essential for stimulating PMS to generate ROS. Furthermore, the synergistic system (EO-Co-N/C-GP-PMS) promotes the conversion of N-coordinated Co3+/Co2+, promotes cobalt cycling, and enables continuous use of 3D particle electrodes. Removal of pollutants is primarily achieved through the collaborative action of reactive oxygen species (ROS) in EO-Co-N/C-GP-PMS. ROS generation pathways are investigated. The superiority of collaborative systems is proved. It also provides a new perspective for combining different AOPs methods.

Atomically precise Au15Ag23 nanoclusters co-protected by alkynyl and bromine: Structure analysis and electrocatalytic application toward overall water splitting

We report the structure analysis and electrocatalytic application toward overall water splitting of atomically precise Au15Ag23(tBuC ≡ C)18Br6 nanoclusters (Au15Ag23 in short). Au15Ag23 possesses a triple-layered core-shell-shell metal core structure of Au6@Au6Ag23@Au3, with the core centre being a tetragonal bipyramidal Au6 structure unit, and the outer layer of one Ag atom linked with two alkynyl ligands to form a linear structural motif covering the surface of the metal nucleus. Au15Ag23 is a superatom with 14 free electrons and it displays a unique absorption profile. Remarkably, the Au15Ag23 catalyst exhibits excellent electrocatalytic properties in hydrogen evolution reaction (HER), manifested by a low overpotential of 125 mV at 10 mA cm−2 and a negligible current decrease for 16 h in 0.5 M H2SO4, while the Au15Ag23/NiFe-LDH catalyst demonstrates outstanding electrocatalytic performance in oxygen evolution reaction (OER), evidenced by an ultralow overpotential of 250 mV at 10 mA cm−2 and a ∼5% current decrease for 30 h in 1.0 M KOH. Such promoting effect is ascribed by the electron transfer from NiFe-LDH to the Au15Ag23 clusters, which results in generating high valent Fe species as active sites. When using the two catalysts for overall water splitting (OWS), only 1.51 V was required to achieve a current density of 10 mA cm−2, and it performed well in the 50 h's stability test. This study enriches the family member of alkynyl-protected AuAg bimetallic nanoclusters, and further highlights the dual functionalities (catalyzing HER and promoting OER) that metal nanoclusters can make contribution for electrochemical energy conversion and beyond.

Kernel Regulation of Ultra‐stable Cu12 Nanoclusters by Triple Collaborative Ligands

AbstractCu clusters are generally unstable and their cluster nuclei are difficult to be controlled. Even minor adjustments in the synthesis of Cu clusters can easily lead to great changes in their cluster nuclei. In this work, we have successfully utilized triple collaborative ligands to obtain a pair of infinitely extended Cu12 cluster‐based chains (Cu12‐1 and Cu12‐2). They have identical Cu12 metal core structures but slightly different coordinated ligands. Both Cu12‐1 and Cu12‐2 show excellent thermal and ambient stability. However, they exhibit diverse room‐temperature photoluminescence phenomena. Crystalline Cu12‐2 displays red‐shifted photoluminescence (637 nm) compared with Cu12‐1 (624 nm) due to the relatively smaller LUMO‐HOMO gap caused by the substituent effect of electro‐withdrawing F atoms. Meanwhile, the substituent effect has influences on electronic structures and electrostatic potentials, thus leading to differences in photoluminescence intensity, PLQY, and lifetime. Crystalline Cu12‐1 displays more intense room‐temperature photoluminescence, higher PLQY and longer lifetime. This work provides a valuable approach for how to prepare highly stable Cu clusters and precisely control their structures to regulate their properties.

Dynamic tracking of exsolved PdPt alloy/perovskite catalyst for efficient lean methane oxidation

Supported Pd based catalysts are considered as the efficient candidates for low-carbon alkane oxidation for their outstanding capability to break C-H bond. Whereas, the irreversible deactivation of Pd based catalysts was still frequently observed. Herein, we reinforced the extruded Pd nanoparticles with quantitive Pt to assemble the evenly distributed PdPt nanoalloy onto ferrite perovskite (PdPt-LCF) matrix with strengthened robustness of metal/oxide support interface. We further co-achieved the enhanced performance, anti-overoxidation as well as resistance of vapor-poisoning in durability measurement. The operando X-ray photoelectron spectroscopy (O-XPS) combined with various morphology characterizations confirms that the accumulation of surface deep-oxidation species of Pd4+ is the culprit for fast activity loss in exsolved Pd system, especially at high temperature of 400 °C. Conversely, it could be completely suppressed by in-situ alloying Pd with equal amount of Pt, which helps maintain the metastable Pd2+/Pd shell and metallic solid-solution core structure. The density function theory (DFT) calculations further buttress that the dissociation of CH was facilitated on alloy/perovskite interface which is, on the contrary, resistant toward O–H bond cleavage, as compared to Pd/perovskite. Our work suggests that the modification of exsolved metal/oxide catalytic interface could further enrich the toolkit of heterogeneous catalyst design.

N-Doped Carbon Nanotube Shell Encapsulating the NiFe Metal Core for Enhanced Catalytic Stability in Methanol Oxidation Reaction by the Structural Cooperation Mechanism.

Exploitation of high-efficiency catalysts toward methanol oxidation is a pivotal step to promote the commercialization of direct methanol fuel cells. Herein, a strategy is demonstrated to prepare nitrogen-doped carbon nanotubes with NiFe metal particles (NiFe@N-CNT) as the carrier material of Pt nanoparticles. Combining SEM and TEM, NiFe metal particles are fully encapsulated in N-CNTs, and they form the metal core and carbon nanotube shell structure based on the structural cooperation mechanism. Surprisingly, the as-prepared Pt/NiFe@N-CNT catalyst shows superior catalytic activity (1023 mA mg-1Pt) compared to commercial Pt/C (392 mA mg-1Pt), Pt/Ni@N-CNT (331 mA mg-1Pt), and Pt/Fe@N-CNT (592 mA mg-1Pt). After 1000 cycles, Pt/NiFe@N-CNT maintains the optimal catalytic activity (588 mA mg-1Pt), and its mass activity loss is 42.5%, which is better than those of commercial Pt/C (64.0%), Pt/Ni@N-CNT (67.7%), and Pt/Fe@N-CNT (59.6%) catalysts, indicating that the Pt/NiFe@N-CNT catalyst achieves excellent catalytic activity and stability, which stems chiefly from the homodispersed Pt nanoparticles and the generation of the metal core-carbon nanotube shell based on the structural cooperation mechanism. This study reports the facile construction of a metal core-carbon nanotube shell structure, which intrinsically ameliorates structural collapse of carrier material, thereby improving the catalytic stability of the Pt-based catalyst and broadening the view for design of other desire catalysts in methanol oxidation.

Structural Isomerization in Cu(I) Clusters: Tracing the Cu Thermal Migration Paths and Unveiling the Structure-Dependent Photoluminescence

Structural Isomerization in Cu(I) Clusters: Tracing the Cu Thermal Migration Paths and Unveiling the Structure-Dependent Photoluminescence

Anodic coulometry of zero-valent iron nanoparticles

Nanoscale zero-valent iron (nZVI) particles are currently used for environmental remediation due to their ion sequester ability. This trait plus their magnetic behavior, and biocompatibility, makes them a promising alternative for heavy metal poisoning treatment, development of MRI dye, and drug delivery loads, among others. Their rapid passivation in aqueous media inhibit their differentiation from magnetite (Fe 3 O 4 ) by electrochemical methods, due to its surface oxide. Herein, this work is focused on applying the electrochemical method known as anodic particle coulometry (APC) to detect and characterize nZVI. During the experiments, current blips are observed as a result of a current increase when the electroactive nZVI particle reaches the Au working ultra-microelectrode surface. The integration of current blips resulted in a charge distribution between 4 pC and 5 pC, which correlates with nanoparticles in a size range between 70 nm and 100 nm. The size distribution obtained were compared to the size distribution found using scanning transmission electron microscopy (STEM) and nanoparticle tracking analysis (NTA). The results were compatible with the results obtained by the other two techniques. Characterization of nZVI particles using x-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) validate the presence of elemental iron which differentiates the material from magnetite. A chemical shift of ca. 1 eV from metallic iron to iron oxide (L 3 : 708 eV and L 2 : 721.2 eV versus L 3 : 709 eV and L 2 : 722.2 eV) is observed from EELS at nZVI particle center and edge, respectively. This suggests the presence of a passivated surface and a metallic core, a metallic core and oxide shell structure.

Quantifying and dispensing of magnetic particles in a self-assembled magnetic particle array

We develop a low-cost, mass-production process for creating rod-shaped glass-coated magnetic particles consisting of a magnetic metal core and glass shell structure. We investigate their magnetic properties by analyzing their optical absorbance in suspension as a function of the orientation of a 1 mT magnetic field. From the response we derive that the magnetization of the particles is 0.1 MA/m. We demonstrate an automated system that quantifies and dispenses a large amount of RGMPs by magnetic self-assembly on a high-volume plate patterned with an array of holes. This automatic dispenser can provide packaging forms with the smallest unit of RGMPs for in-vitro diagnostics and is expected to reduce the time and effort required for the assembly and packaging process.

Synthesis, Structure, and Surface Adsorption Characteristics of a Polynuclear MnII,IV-YbIII Complex.

The controlled adsorption of polynuclear coordination compounds with specific structural and electronic characteristics on surfaces is crucial for the prospective implementation of molecule-surface interfaces into practical electronic devices. From this perspective, a neutral 3d,4f-coordination cluster [MnII3MnIVYb3O3(OH)(L·SMe)3(OOCMe)9]·2MeCN·3EtOH (1·2MeCN·3EtOH), where L·SMe- is a Schiff base, has been synthesized and fully characterized and its adsorption on two different solid substrates, gold and graphite, has been studied. The mixed-valence compound with a bilayered metal core structure and the structurally exposed thioether groups exhibits a substantially different surface bonding to metallic gold and semimetallic graphite substrates. While on graphite the adsorption takes place only on distinguished attraction points with a locally increased number of potential bonding sites such as terrace edges and other surface defects, on gold the molecules were found to adsorb rather weakly on randomly distributed adsorption sites of the surface terraces. This entirely different behavior provides important information for the development of advanced surface materials that may enable well-distributed ordered molecular assemblies.

Ultrahigh areal capacity of self-combusted nanoporous NiCuMn/Cu flexible anode for Li-ion battery

Nanostructured transition metal oxides (TMOs) have shown extraordinary promise as anode materials for Lithium ion battery but still been challenging for practical applications due to their low conductivity and activity with high loading mass. Herein, we prepare an integrated high-loading-mass TMOs based anode with 3D nanoporous structure and metallurgical bonding interface between oxide and current collector by self-combustion and subsequently mild annealing of the nanoporous NiCuMn (np-NiCuMn). Self-combustion, caused by the high surface energy of np-NiCuMn, induces ligament coarsening and deep surface oxidation of the alloy, which consumes all the energy quickly and form metal core and oxide shell structure with loading mass up to 7.3 mg cm−2. Mild annealing in H2 at 250 °C creates robust vacancies in oxide layers (6.9 mg cm−2 of oxide retention) with some precipitated Cu doping, which not only provides more Li+ storage sites but also further enhance the electron/ion transportation in the anode. Consequently, the flexible integrated electrode demonstrates an ultrahigh area capacity of up to 9.48 mAh cm−2 at a current density of 0.5 mA cm−2, as well as excellent rate performance and cycle stability. This work is expected to open a cost-effective and large-scale route to prepare high-capacity electrodes for next-generation energy storage devices.

Double-walled iron oxide nanotubes via selective chemical etching and Kirkendall process

Double-walled oxide nanotube structures are interesting for a wide range of applications, from photocatalysis to drug delivery. In this work, a progressive oxidation method to fabricate double-walled nanotube structures is reported in detail. The approach is based on the electrodeposition of metallic iron nanowires, in porous alumina templates, followed by a selective chemical etching, nanoscale Kirkendall effect, a fast oxidation and out-diffusion of the metallic core structure during thermal annealing. To validate the formation mechanism of such core-shell structure, chemical composition and atomic structure were assessed. The resulting hematite nanotubes have a high degree of uniformity, along several microns, and a nanoscopic double-walled structure.

Thermal Behavior of Auxetic Honeycomb Structure: An Experimental and Modeling Investigation

Recently, engineers and researchers reconsider honeycomb sandwich structures due to their vast application in industries and aviation arenas. In this study, a new honeycomb sandwich material was developed and tested. The purpose of the present work is to investigate numerically and experimentally with a comparative study on the effects of heat transfer on design parameters and geometry for different types of exotic honeycomb structures taking in account radiation within the cell and conduction in the cell walls. The numerical solution for temperature profiles for different types of exotic honeycomb structures and solid disk are performed in order to inspect the variation of heat transfer. The modeling results show a good agreement with the experimental results. The present work demonstrates that the temperature profile for reentrant is the highest one compared to splined and stiffened which reaches around 10% at temperature of the front surface Tin = 100 °C. It was found that the rib length enhances significantly heat transfer. Results showed also that stiffened honeycomb has a good insulation and metallic honeycomb core structure has a good thermal insulation characteristic for the highest instantaneous temperature, whereas reentrant honeycomb has a good heat transmission.

Syntheses, structures, and magnetic properties of cubane-based cobalt and nickel complexes with ONO-tridentate ligands

Three types of cubane-based complexes, [Co4(L1-H)4Cl2(MeOH)2] (1) [H2L1-H=N-(2-hydroxymethylphenyl)salicylideneimine], [Ni4(L1-Bz)4(EtOH)4] (2) [H2L1-Bz=N-(2-hydroxymethylphenyl)-5,6-benzosalicylideneimine], and [Co2Ni(L1-H)2(HL1-H)(CH3COO)2] (3), have been characterized by X-ray crystal structure analyses and magnetic measurements. Homo-metal complexes 1 and 2 are tetranuclear complexes. Complex 1 has a defective double-cubane metal core. The valence state of cobalt ions is assigned to mixed valence Co(II)2Co(III)2. On the contrary, 2 takes a simple cubane core comprised of four [Ni(II)(L1-Bz)] monomer units. Complex 3 has a novel hetero-metal and mixed-valence trinuclear metal core structure. Cryomagnetic studies for 1–3 indicate that ferromagnetic interactions are dominate due to the cubane-based metal core structures.

On Shock Response of Marine Sandwich Structures Subjected to UNDEX Loading

Survivability at sea in a hostile environment is the last line of hope for naval platforms. Research today has seen advancement of underwater explosion science along with the delivery systems such as torpedoes and underwater missiles. The evaluation of the structural response to such explosive loading and designing structures to attenuate the loading effects is of prime concern. The structural response to various impulsive loads specifically to blast loads in the elasto-plastic region will be in the form of large deformation, crack initiation and tensile tearing. The above failure modes can be predicted reasonably accurately at the design stage based on finite element modelling employing nonlinear shock analysis. In the prediction of structural response beyond elastic limit, both material and geometric nonlinearity are to be considered. The material non-linearity is generally modeled by Von Mises yield criteria and associated flow rules with isotropic hardening. The material models such as rigid plastic, elastic perfectly plastic and elasto-plastic can be used to represent the material behaviour. The geometric non-linearity is based on total or updated Lagrangian formulation. Cole [1] established useful empirical relations to model the underwater explosion (UNDEX) loading, which were the outcome of numerous experimental investigations done by the military agencies. In the present study the UNDEX load profile has been modeled as an exponentially decaying shock wave which varies spatially and transiently. An elasto-plastic model with isotropic hardening, strain rate effects and fracture criterion has been developed was used to predict and establish the failure modes in high strength (HS) and WELDOX Steel rectangular plates sandwiched with a metallic core structure, under clamped edge conditions. These models were implemented in the non-linear finite element code ABAQUS/Explicit. The present study establishes empirical relationships derived from numerical analysis of stiffened and un-stiffened plates subjected to UNDEX.