Stability Of Nanoclusters Research Articles

Synergetic storage of ammonia over Al quantum dots embedded graphene sheets: A first principles perspective

In view of the increasing energy demand and global warming, it is imperative to search for a renewable and environmental friendly fuel in lieu of non-renewable energy resources. Hydrogen stands out to be the best fuel as both, renewable and clean. Concerning the use of hydrogen as a fuel, its production as well as storage are current global challenges being worked on. In this article, a density functional theory based study is performed to identify the potential of supported Al cluster cages for ammonia storage. In this context, initially, stability of pristine and doped aluminum nanoclusters anchored on graphene sheet is evaluated following which thus supported stable nanoclusters are studied for the adsorption of NH3 to identify their storage capacity. For both, complexes and NH3 adsorbed complexes, Density of States (DOS), Charge Density Difference (CDD) and Bader charge analysis is done to understand their electronic properties.

N-Doped Carbon as a Promoted Substrate for Ir Nanoclusters toward Hydrogen Oxidation in Alkaline Electrolytes.

Development of effective electrocatalysts toward hydrogen oxidation with a low content of noble metals has attracted the attention of the catalytic community. In this work, a novel catalyst composed of nitrogen-doped carbon acting as the substrate and Ir nanoclusters as active species was prepared, which was then employed as an effective catalyst for the hydrogen oxidation reaction (HOR) in an alkaline electrolyte. In 0.1 M KOH, the optimized catalyst provides an exchange current density of 0.144 mA cmIr-2 for HOR that outperforms the catalytic activity of the commercial Pt/C catalyst with a Pt content of 20 wt %. The substrate induces highly active Ir sites that markedly boosted the electrocatalytic activity for HOR. The nitrogen-doped carbon substrate increases the stability of Ir nanoclusters and decreases the absorption energy of hydrogen on Ir sites; at the same time, the higher electrostatic potential around the adsorbed hydrogen on Ir/N-doped carbon also enables them to be easily attracted by OH- species, both of which enhanced the catalytic activity. The excellent catalytic activity and the understanding shown here will give some hints for the development of HOR catalysts used in alkaline electrolytes.

Yolk-shell nanoparticles with different cores: A molecular dynamics study

In this work, M@void@Pd (M=Ag, Ni, Pt) yolk-shell nanoparticles are studied by classical molecular dynamics simulation. The aim of simulations was to get more information about the relation between thermodynamic stability of the simulated nanoclusters with their core composition. For this purpose, the simulation data was analyzed by various methods including interatomic distance evolution, stability parameter, surface energy, coordination number analysis, conformational changes, and radial distribution function. The results indicated that the interatomic distance evolution and coordination number of the core atoms play the important role in these phenomena, in such a way that the structures with unique physical and chemical properties can be created.

A two-step optimization approach for structures investigation of Pd-Ir bimetallic nanoclusters

The structures of nanoalloys are crucial for understanding their catalytic performance because the stable structures can affect the activity and selectivity of nanocatalysts. Therefore, investigating the stable structures of nanoalloys is important to understand their catalytic activities. In this article, a two-step optimization approach by combining a basin hoping genetic algorithm (BHGA) and DFT calculation is employed to investigate the structural stability of Pd-Ir alloy nanoclusters. Different compositions (Pd and Ir atoms proportion) and different initial configurations of 38-atom Pd-Ir alloys are considered. The combination of BHGA and DFT method can effectively find the stable structures of truncated octahedral (TO) configurations for 38-atom Pd-Ir alloys with high accuracy and low time complexity. Furthermore, the formation energy and bond energy of Pd-Ir clusters are calculated and analyzed, the results show the bond strength follows Pd-Pd > Pd-Ir > Ir-Ir. The most stable configuration is Pd6Ir32 with all the core sites are occupied by Pd, which shows better electrochemical performance.

High Fructose Concentration Increases the Fluorescence Stability of DNA-Templated Copper Nanoclusters by Several Thousand Times.

DNA-templated copper nanoclusters (CuNCs) have limited applications because of their low fluorescence stability (several tens of minutes). In this study, we prepared CuNCs with improved temporal fluorescence stability by introducing fructose into the CuNC synthesis process and optimizing the reaction conditions. The inclusion of fructose increased the operating lifetime of CuNCs by approximately 5200-fold from 30 min to 108 days and improved their stability against heat, acids, and bases compared to CuNCs synthesized under original conditions. In addition, the fluorescence signal of CuNCs was maintained for a significantly longer time when stored at refrigeration (4 °C) and freezing (-20 °C) temperatures. Importantly, this method did not require the addition of substances other than fructose or any additional physicochemical treatment to maintain the fluorescence of DNA-templated CuNCs for more than several tens of days. As such, this study could serve as a basis to improve the stability of CuNCs for various applications.

Effect of Ligands on the Stability of Gold Nanoclusters.

Gold nanoclusters (AuNCs) are atomic architectures that can be precisely tailored for catalytic applications. In this work, we studied two benchmark AuNCs, Au25(SR)18 and Au144(SR)60, covered by aromatic and aliphatic ligands to envision how the 3D structure of the ligand impacts the stability of the nanomaterial. Surprisingly, we found that increasing the alkanethiol length has a poor or null effect on the stability of the AuNCs, a trend opposite to that on Au(111) surfaces. When considering the aromatic or aliphatic nature, the AuNC stability follows the same trend as on Au(111): the thermodynamical stability is dictated by the ligand density rather than its chemical nature, where the aliphatic ligand imparts more stability than the aromatic one. Our findings provide a tool to predict how an ultrasmall gold core can interact with the environment, substrate, and themselves according to the stability of its protecting ligand shell.

Study of Cu, Co and Ru Nanoclusters on MoS2 to Predict Thin Film Morphology

Interfaces of 2D materials with metals are of interest for a large variety of applications, including sensors, batteries, catalysis, electronics, and semi-conductor devices. Transition metal dichalcogenides (TMDs) and specifically MoS2 are some of the most widely studied 2D materials. A detailed understanding of the interactions of metals with 2D TMDs can give useful insights into possible applications for metal-TMD systems. However, the literature focuses mainly on comparing trends in single atom adsorption and studying nanoparticles on MoS2 monolayers.In this work we aim to increase the understanding of metal-MoS2 interactions and metal nucleation on TMDs. We use density functional theory (DFT) to study the adsorption of small metal clusters with up to four atoms on MoS2 monolayers. Insights gained from this work allow us to understand the initial nucleation of metal thin films on TMDs as well as predict the likely morphology of the thin film as it grows.The metals studied are Cu, Co and Ru, which are chosen for their range of applications, particularly in electronics. Metal-substrate interactions, preferred adsorption modes and stable nanocluster geometries are presented on pristine MoS2 and in the presence of the readily formed sulfur vacancy. The strength of interaction between the metals and MoS2 is in the order Co > Ru > Cu. Metal-substrate interactions are localised to the adsorption site; however we find that both Ru and Co can induce formation of sulfur vacancies through the formation of the corresponding metal sulfide.

Copper Clusters on h-BN-Covered Pt(110): Nucleation, Stability, and Local Surface Potential

Copper-based nanocatalysts are essential for efficient electroreduction of CO2 toward hydrocarbon fuels. Nucleation, growth, and stability of copper nanoclusters on hexagonal boron nitride (h-BN) films on a Pt(110) substrate were studied by scanning tunneling microscopy and spectroscopy. We find that the h-BN/Pt(110) Moiré superstructure has a relatively weak templating effect, visible only at very low coverages of copper. Upon postannealing cluster ripening is observed─with increasing temperature the spherical-cap-like clusters grow in both width and height, preserving a constant aspect ratio. Intercalated islands were never observed, not even after annealing to 970 K. Small copper clusters are found to exhibit a local work function lower than that of low-index single-crystalline copper surfaces.

Designing of robust and sensitive assay via encapsulation of highly emissive and stable blue copper nanocluster into zeolitic imidazole framework (ZIF-8) with quantitative detection of tetracycline

Metal–organic frameworks (MOFs) with high stability and porosity have gained great attention in bioanalysis due to their potential in improving sensitivity and robustness of assays. Herein, to improve both the stability and the emission intensity of Cu nanoclusters (CuNCs), in situ entrapment strategy of CuNCs into zeolitic imidazolate framework-8 (ZIF-8) is described. Blue emissive and stable CuNCs was prepared, for the first time, using thiamine hydrochloride as capping agents, and showed strong and stable emission at 440 nm when excited at 375 nm with fluorescence quantum yields 12%. Encapsulation of CuNC into ZIF-8 showed dramatic enhancement of the fluorescence intensity up to 53% fluorescence quantum yield. Furthermore, the CuNCs@ZIF-8 possesses better stability (more than three months) due to protective and confinement effect of MOFs. Upon the addition of tetracycline to CuNCs@ZIF-8 solution, the blue emission intensity was significantly decreased. The fluorescence ratio (Fo/F) against the concentration of tetracycline exhibited a satisfactory linear relationship from 1.0 to 10.0 µM with a detection limit (LOD) of 0.30 µM. The current probe was applied for quantification of tetracycline in drug sample with satisfactory accuracy and precision.Graphical abstract

Bulky Thiolate-Protected Silver Nanocluster Ag 213 (Adm-S) 44 Cl 33 with Excellent Electrocatalytic Performance toward Oxygen Reduction

Bulky Thiolate-Protected Silver Nanocluster Ag ₂₁₃ (Adm-S) ₄₄ Cl ₃₃ with Excellent Electrocatalytic Performance toward Oxygen Reduction

Geometric, electronic and spectral properties of germanium and Eu-doped germanium clusters

This study explored the geometric, electronic, and spectral properties of germanium and Eu-doped germanium clusters and compared their simulated PES spectra. The stability of Gen and EuGen nanoclusters was examined with density functional theory using FHI-aims as a software package. Symmetry-adapted cluster-configuration interaction general-R (SAC-CI-General-R) method and the SDD basis set were adopted to determine ionization energies and calculate their intensities. Natural bond orbital (NBO) calculations were performed to determine the effective molecular orbitals in the ionization and study the electron density on the nanoclusters. The shape of molecular orbitals (MO) involved in the ionization process for each structure was displayed and interpreted. The analyses of binding energies showed that increasing the size of nanoclusters leads to more stability for nanoclusters. Ionization energy and the photoelectron spectrum of these clusters indicated that Eu as an impurity reduces ionization energy and shifts the ionization processes towards infrared wavelengths. Interestingly, pure and doped clusters followed a similar pattern in terms of an increase/decrease in the first ionization energy compared to n-1 and n + 1 clusters.

A set point in the selection of the αβTCR T cell repertoire imposed by pre-TCR signaling strength

Signaling via the T cell receptor (TCR) is critical during the development, maintenance, and activation of T cells. Quantitative aspects of TCR signaling have an important role during positive and negative selection, lineage choice, and ability to respond to small amounts of antigen. By using a mutant mouse line expressing a hypomorphic allele of the CD3ζ chain, we show here that the strength of pre-TCR–mediated signaling during T cell development determines the diversity of the TCRβ repertoire available for positive and negative selection, and hence of the final αβTCR repertoire. This finding uncovers an unexpected, pre-TCR signaling–dependent and repertoire–shaping role for β-selection beyond selection of in-frame rearranged TCRβ chains. Our data furthermore support a model of pre-TCR signaling in which the arrangement of this receptor in stable nanoclusters determines its quantitative signaling capacity.

Quantum chemical design and prediction that complements understanding: How do the transition metals enhance the CO2 sensing ability of inorganic Mg12O12 nanoclusters?

Nanoscale magnesium oxide (Mg12O12) clusters have enormous applications like toxic gases sensing and removal, high temperature semiconductors, and as drug delivery systems. Mg12O12 nanoclusters gained a massive interest of all the researchers due to their efficient electronic behavior, easy and smart sensing of toxic gases and their removal from environment. In this study, density functional theory (DFT) calculations are employed to examine the change in electronic behavior of Mg12O12 upon copper (Cu) and nickel (Ni) decoration. Additionally, the adsorption of CO2 on Cu and Ni doped Mg12O12 nanoclusters is also estimated through various geometric parameters like adsorption energy, energy band gap, Fermi level, frontier molecular orbitals (FMOs), and natural bond orbital charges (QNBO). The charge separation upon metal decoration and CO2 adsorption are also estimated through molecular electrostatic potential (MEP), and dipole moment analysis. Global indicators of reactivity recommend that M-Mg12O12 (M = Cu and Ni), and CO2-M-Mg12O12 nanoclusters are naturally stable and effective nanoclusters for the development of future CO2 sensing materials.

Thermodynamic Descriptors for Structural Stability and Ligand Compatibility of Thiolate-Protected Gold Nanoclusters

Thermodynamic Descriptors for Structural Stability and Ligand Compatibility of Thiolate-Protected Gold Nanoclusters

Stability and electronic properties of V-doped ruthenium nanoclusters and their adsorptive properties towards hydrogen sulphide and serine molecules

The stability and electronic properties of the RunV (n = 2–10) nanoclusters and their interaction with hydrogen sulphide and serine molecules were conducted using DFT calculations at the PBE/LanL2DZ/6-311G(d,p) level of theory. The results indicate that the Ru3V, Ru5V and Ru7V clusters were found to be more stable than their neighbouring clusters, and the V atom in the binary clusters has been viewed as the most favourable adsorption site for a nucleophilic attack. The interaction of H2S with the clusters easily leads to its dissociation into *SH and *H moieties, indicating that the dissociative adsorption was found to be more favourable than the molecular adsorption. This finding suggest that these clusters could be employed as nanocatalysts for the H2S decomposition reaction. In contrast, the serine adsorption over the surface of the RunV clusters was carried out without dissociation with adsorption energies which vary from - 29.3 to - 58.7 kcal mol−1, suggesting a chemisorption process. The adsorption of the serine molecule on the RunV (n = 3, 7 and 10) clusters causes a significant change in their energy gaps, indicating a high electronic sensitivity of these clusters towards the serine molecule.

Crystalline Modulation Engineering of Ru Nanoclusters for Boosting Ammonia Electrosynthesis from Dinitrogen or Nitrate.

Developing highly efficient nitrogen reduction reaction (NRR) and nitrate reduction reaction (NITRR) electrocatalysts is an ongoing challenge. Herein, we report the in situ growth of ultrafine amorphous Ru nanoclusters with a uniform diameter of ∼1.2 nm on carbon nanotubes as a highly efficient electrocatalyst for both the NRR and the NITRR. The amorphous Ru nanoclusters were prepared via a convenient ambient chelated co-reduction method, in which trisodium citrate as a chelating agent played a key role to form amorphous Ru instead of crystalline Ru. The strong d-π interaction between Ru metal and carbon nanotubes led to the homogeneous distribution and good long-term stability of ultrafine Ru nanoclusters. Compared with crystalline Ru, amorphous Ru nanoclusters with abundant low-coordinate atoms can provide more catalytic sites. The amorphous Ru nanoclusters exhibited an NH3 yield of 10.49 μg·h-1·mgcat.-1 and a FENH3 of 17.48% at -0.2 V vs reversible hydrogen electrode (RHE) for NRR. For the NITRR, an NH3 yield of 145.1 μg·h-1·mgcat.-1 and a FENH3 of 80.62% were also achieved at -0.2 V vs RHE. This work provides new insights into crystalline modulation engineering of metal nanoclusters for electrocatalytic ammonia synthesis.

Silicon Cluster Arrays on the Monolayer of Hexagonal Boron Nitride on Ir(111)

Periodic structures of silicon are of interest in quantum-dot-based applications because of their unique optical and electronic properties. We report on the fabrication of stable quasi-ordered Si nanocluster arrays on the moiré of a hexagonal boron nitride (h-BN) monolayer on Ir(111). The h-BN monolayer promotes the growth of regular Si nanoclusters at 130 K and electronically decouples the clusters from the underlying metallic substrate. Using scanning tunneling microscopy and spectroscopy, we have investigated the cluster binding sites, their electronic structure, and their thermal stability. We find that the clusters display a size-dependent bandgap and that they are stable up to 577 K, after which cluster coalescence degrades the arrays.

Synthesis of highly stable luminescent silver nanoclusters in metal–organic framework for heightened antibacterial activity

Synthesis of highly stable luminescent silver nanoclusters in metal–organic framework for heightened antibacterial activity

Engineering stable Pt nanoclusters on defective two-dimensional TiO2 nanosheets by introducing SMSI for efficient ambient formaldehyde oxidation

The strong metal-support interaction (SMSI) has received wide attention in heterogeneous catalysis for the room-temperature oxidation of formaldehyde. An interaction between Pt nanoclusters and oxygen vacancy defects will lead to SMSI over the Pt-based catalysts. In this study, defective two-dimensional (2D) TiO2 nanosheets were synthesized and successfully anchored Pt nanoclusters with a size of 1.3 nm (0.1Pt/TiO2-NS). The 0.1Pt/TiO2-NS catalyst displayed a superior activity of > 95% HCHO conversion at room temperature, which was ∼ 50% higher than that obtained for a counterpart having the commercial TiO2 (Degussa P25) support. The abundant oxygen vacancies and stable Pt nanoclusters on 0.1Pt/TiO2-NS by introducing SMSI boosted the excellent activity and stability of HCHO oxidation. By exploring electron transfer, suppression of small-molecule adsorption and encapsulation, SMSI was well demonstrated. Furthermore, electron transfer from Pt to TiO2-NS led to the electron-deficient Pt surface. The electron-deficient Pt caused by SMSI will enhance the adsorptions of HCHO and H2O/O2, subsequently improving the catalytic performance. SMSI between Pt nanoclusters and oxygen vacancies endowed the 0.1Pt/TiO2-NS catalyst excellent activity and stability to HCHO elimination. In addition, the mechanism for the high HCHO oxidation performance were examined through analysis of in situ HCHO-diffuse reflectance infrared Fourier transform spectra (DRIFTS).

Formation of Unconventional Stoichiometric Na-Cl Magic-Number Nanoclusters and 2D Assembly on Ir(111).

Sodium chlorides in non-1:1 stoichiometry are counterintuitive but recently their existence has been found under the high pressure condition or in the confined space between graphene sheets. Here the direct observation of the formation of Na3 Cl nanoclusters, a stable magic-number structure, is reported on an Ir(111) surface using scanning tunneling microscopy and noncontact atomic force microscopy. The stability of Na3 Cl nanoclusters in the free and adsorbed state is corroborated by density functional theory calculations. It is also found that a density of nanoclusters together with Cl adatoms may further aggregate and self-assemble into a Na3 Cl4 monolayer, forming a novel metastable phase of NaCl(111) with a honeycomb lattice. Further calculations suggest that charge transfer between the polar nanoclusters and the metal substrate stabilizes NaCl of non-1:1 stoichiometry. The work exhibits the possibility of exploring unconventional ionic crystals on the surface with atomically precise control of structure and composition.