Dry Reforming of Methane to Syngas Mediated by Rhodium-Cobalt Oxide Cluster Anions RhCoO.

Dry reforming of methane (DRM) to syngas is an important route to co-convert CH and CO. However, the highly endothermic nature of DRM induces the thermocatalysis to commonly operate at high temperatures that inevitably causes coke deposition through pyrolysis of methane. Herein, benefiting from the mass spectrometric experiments complemented with quantum chemical calculations, we have discovered that the bimetallic oxide cluster RhCoO can mediate the co-conversion of CH and CO at room temperature giving rise to two free H molecules and two adsorbed CO molecules (CO).

Experimental Reactivity of (MoO)O ( = 1-21) Cluster Anions with C-C Alkanes: A Simple Model to Predict the Reactivity with Methane.

Metal oxide clusters with atomic oxygen radical anions are important model systems to study the mechanisms of activating and transforming very stable alkane molecules under ambient conditions. It is extremely challenging to characterize the activation and conversion of methane, the most stable alkane molecule, by metal oxide cluster anions due to the low reactivity of the anionic species. In this study, using a ship-lock type reactor that could be run at relatively high pressure conditions to provide a high number of collisions in ion-molecule reactions, the rate constants of the reactions between (MoO)O ( = 1-21) cluster anions and the light alkanes (C-C) were measured under thermal collision conditions.

Conversion of Methane at Room Temperature Mediated by the Ta-Ta σ-Bond.

Metal-metal bonds constitute an important type of reactive centers for chemical transformation; however, the availability of active metal-metal bonds being capable of converting methane under mild conditions, the holy grail in catalysis, remains a serious challenge. Herein, benefiting from the systematic investigation of 36 metal clusters of tantalum by using mass spectrometric experiments complemented with quantum chemical calculations, the dehydrogenation of methane at room temperature was successfully achieved by 18 cluster species featuring σ-bonding electrons localized in single naked Ta-Ta centers. In sharp contrast, the other 18 remaining clusters, either without naked Ta-Ta σ-bond or with σ-bonding electrons delocalized over multiple Ta-Ta centers only exhibit molecular CH-adsorption reactivity or inertness.

Size-dependent reactivity of VO ( = 1-9) clusters with ethane.

Cost-effective and readily accessible 3d transition metals (TMs) have been considered as promising candidates for alkane activation while 3d TMs especially the early TMs are usually not very reactive with light alkanes. In this study, the reactivity of V and VO ( = 1-9) cluster cations towards ethane under thermal collision conditions has been investigated using mass spectrometry and density functional theory calculations. Among V ( = 1-9) clusters, only V can react with CH to generate dehydrogenation products and the reaction rate constants are below 10 cm molecule s.

Reverse water-gas shift catalyzed by RhVO ( = 3-7) cluster anions under variable temperatures.

A fundamental understanding of the exact structural characteristics and reaction mechanisms of interface active sites is vital to engineering an energetic metal-support boundary in heterogeneous catalysis. Herein, benefiting from a newly developed high-temperature ion trap reactor, the reverse water-gas shift (RWGS) (CO + H → CO + HO) catalyzed by a series of compositionally and structurally well-defined RhVO ( = 3-7) clusters were identified under variable temperatures (298-773 K). It is discovered that the RhVO clusters can function more effectively to drive RWGS at relatively low temperatures.

Machine Learning for Experimental Reactivity of a Set of Metal Clusters toward C-H Activation.

Understanding the mechanisms of C-H activation of alkanes is a very important research topic. The reactions of metal clusters with alkanes have been extensively studied to reveal the electronic features governing C-H activation, while the experimental cluster reactivity was qualitatively interpreted case by case in the literature. Herein, we prepared and mass-selected over 100 rhodium-based clusters (RhVO and RhCoO) to react with light alkanes, enabling the determination of reaction rate constants spanning six orders of magnitude.

Difference of carrier dynamics in a semiconductor saturable absorber mirror with and without B ion-implantation.

Three samples whose growth temperatures were 450°C, 500°C, and 560°C for , , and , respectively, were tested by femto-second time-resolved transient absorption spectroscopy. The results indicate that the carrier dynamics of excited state absorption were dominant, and the lifetimes of carriers trapped by defect levels were about tens of pico-seconds. To further study the influence of carrier dynamics and recovery time of samples by ion-implantation, ions of 80 and 130 KeV were implanted into the samples with dose of 10/ .

Spectroscopic Characterization of Thermal Methane Activation by Lewis-Acid-Base Pair in a Gas-Phase Metal Nitride Anion TaN.

Activation and transformation of methane is one of the "holy grails" in catalysis. Understanding the nature of active sites and mechanistic details via spectroscopic characterization of the reactive sites and key intermediates is of great challenge but crucial for the development of novel strategies for methane transformation. Herein, by employing photoelectron velocity-map imaging (PEVMI) spectroscopy in conjunction with quantum chemistry calculations, the Lewis acid-base pair (LABP) of [Ta-N] unit in TaN acting as an active center to accomplish the heterolytic cleavage of C-H bond in CH has been confirmed by direct characterization of the reactant ion TaN and the CH-adduct intermediate TaNCH .

Regulating Lewis Acidic Sites of 1T-2H MoS Catalysts for Solar-Driven Photothermal Catalytic H Production from Lignocellulosic Biomass.

Solar-driven photothermal catalytic H production from lignocellulosic biomass was achieved by using 1T-2H MoS with tunable Lewis acidic sites as catalysts in an alkaline aqueous solution, in which the number of Lewis acidic sites derived from the exposed Mo edges of MoS was successfully regulated by both the formation of an edge-terminated 1T-2H phase structure and tunable layer number. Owing to the abundant Lewis acidic sites for the oxygenolysis of lignocellulosic biomass, the 1T-2H MoS catalyst shows high photothermal catalytic lignocellulosic biomass-to-H transformation performance in polar wood chips, bamboo, rice straw corncobs, and rice hull aqueous solutions, and the highest H generation rate and solar-to-H (STH) efficiency respectively achieves 3661 μmol·h·g and 0.18% in the polar wood chip system under 300 W Xe lamp illumination.

Solar-Driven Photothermal Catalytic Lignocellulosic Biomass-to-H Conversion.

The conversion of lignocellulosic biomass to chemical fuel can achieve the sustainable use of lignocellulosic biomass, but it was limited by the lack of an effective conversion strategy. Here, we reported a unique approach of photothermal catalysis by using MoS-reduced graphene oxide (MoS/RGO) as the catalyst to convert lignocellulosic biomass into H fuel in alkaline solution. The RGO acting as a support for the growth of MoS results in the high exposed Mo edges, which act as efficient Lewis acidic sites for the oxygenolysis of lignocellulosic biomass dissolved in alkaline solution.

Volatile and semi-volatile organic compounds in landfill leachate: Concurrence, removal and the influencing factors.

Volatile and semi-volatile organic compounds (VOCs and SVOCs) carried by landfilled wastes may enter leachate, and require appropriate treatment before discharge. However, the driving factors of the entry of VOCs and SOVCs into leachate, their removal characteristics during leachate treatment and the dominant factors remain unclear. A global survey of the VOCs and SOVCs in leachate from 103 landfill sites combined with 27 articles on leachate treatment was conducted to clarify the abovementioned question.

Multimorphological Remoldable Silver Nanomaterials from Multimode and Multianalyte Colorimetric Sensing to Molecular Information Technology.

Inspired by life's interaction networks, ongoing efforts are to increase complexity and responsiveness of multicomponent interactions in the system for sensing, programmable control, or information processing. Although exquisite preparation of single uniform-morphology nanomaterials has been extremely explored, the potential value of facile and one-pot preparation of multimorphology nanomaterials has been seriously ignored. Here, multimorphological silver nanomaterials (M-AgN) prepared by one pot can form interaction networks with various analytes, which can be successfully realized from multimode and multianalyte colorimetric sensing to molecular information technology (logic computing and security).

Activation of Dinitrogen Promoted by Adsorption of CH on FeVC Cluster Anions.

The introduction of organic ligands is one of the effective strategies to improve the stability and reactivity of metal clusters. Herein, the enhanced reactivity of benzene-ligated cluster anions FeVC(CH) with respect to naked FeVC is identified. Structural characterization suggests that CH is molecularly bound to the dual metal site in FeVC(CH).

MoS@N-doped graphitic carbon/TiO photocatalysts for photocatalytic H production from lignocellulosic biomass.

TiO nanoparticles grown on MoS/N-doped graphitic carbon were demonstrated to be efficient noble-metal-free photocatalysts for H production from lignocellulosic biomass, and the H generation rate from wheat straw, corncob, polar wood chip, bamboo, rice hull, corn straw and rice straw aqueous solution respectively reaches 4.9, 6.7, 11.

Sequential-Dependent Synthesis of Bimetallic Silver-Chromium Nanoparticles for Multichannel Sensing, Logic Computing, and 3 in 1 Information Protection.

Bimetallic nanomaterials (BNMs) have been used in sensing, biomedicine, and environmental remediation, but their multipurpose and comprehensive applications in molecular logic computing and information security protection have received little attention. Herein, This synthesis method is achieved by sequentially adding reactants under ice bath conditions. Interestingly, Ag-Cr NPs can dynamically selectively sense anions and reductants in multiple channels.

Volatile and semi-volatile organic compounds in landfill gas: Composition characteristics and health risks.

Gas emitted from landfills contains a large quantity of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), some of which are carcinogenic, teratogenic, and mutagenic, thereby posing a serious threat to the health of landfill workers and nearby residents. However, the global hazards of VOCs and SVOCs in landfill gas to human health remain unclear. To quantify the global risk distributions of these pollutants, we collected the composition and concentration data of VOCs and SVOCs from 72 landfills in 20 countries from the core database of Web of Science and assessed their human health risks as well as analyzed their influencing factors.

Sub-differentiation of PI-RADS 3 lesions in TZ by advanced diffusion-weighted imaging to aid the biopsy decision process.

Background: Performing biopsy for intermediate lesions with PI-RADS 3 has always been controversial. Moreover, it is difficult to differentiate prostate cancer (PCa) and benign prostatic hyperplasia (BPH) nodules in PI-RADS 3 lesions by conventional scans, especially for transition zone (TZ) lesions. The purpose of this study is sub-differentiation of transition zone (TZ) PI-RADS 3 lesions using intravoxel incoherent motion (IVIM), stretched exponential model, and diffusion kurtosis imaging (DKI) to aid the biopsy decision process.

C-H Activation by Iron-Vanadium Bimetallic Oxide Cluster Anions FeV O and FeV O : A Comparison with Scandium-Vanadium Oxide Clusters.

Late transition metal-bonded atomic oxygen radicals (LTM-O⋅ ) have been frequently proposed as important active sites to selectively activate and transform inert alkane molecules. However, it is extremely challenging to characterize the LTM-O⋅ -mediated elementary reactions for clarifying the underlying mechanisms limited by the low activity of LTM-O⋅ radicals that is inaccessible by the traditional experimental methods. Herein, benefiting from our newly-designed ship-lock type reactor, the reactivity of iron-vanadium bimetallic oxide cluster anions FeV O and FeV O featuring with Fe-O⋅ radicals to abstract a hydrogen atom from C -C alkanes has been experimentally characterized at 298 K, and the rate constants are determined in the orders of magnitude of 10 to 10  cm molecule  s , which are four orders of magnitude slower than the values of counterpart ScV O and ScV O clusters bearing Sc-O⋅ radicals.

Colorimetric multi-channel sensing of metal ions and advanced molecular information protection based on fish scale-derived carbon nanoparticles.

Some nanosystems based on carbon nanomaterials have been used for fluorescent chemical/biosensing, elementary information processing, and textual coding. However, little attention has been paid to utilizing biowaste-derived carbon nanomaterials for colorimetric multi-channel sensing and advanced molecular information protection (including text and pattern information). Herein, fish scale-derived carbon nanoparticles (FSCN) were prepared and used for colorimetric detection of metal ions, encoding, encrypting and hiding text- and pattern-based information.

Catalytic NO Reduction by NO Pre-Adsorbed RhCeO NO Clusters.

A fundamental understanding on the dynamically structural evolution of catalysts induced by reactant gases under working conditions is challenging but pivotal in catalyst design. Herein, in combination with state-of-the-art mass spectrometry for cluster reactions, cryogenic photoelectron imaging spectroscopy, and quantum-chemical calculations, we identified that NO adsorption on rhodium-cerium bimetallic oxide cluster RhCeO can create a Ce ion in product RhCeO NO that serves as the starting point to trigger the catalysis of NO reduction by CO. Theoretical calculations substantiated that the reduction of another two NO molecules into N O takes place exclusively on the Ce ion while Rh behaves like a promoter to buffer electrons and cooperates with Ce to drive NO reduction.

A comparative study on the reactivity of ditantalum deuteride cluster anions TaD and TaD toward N.

The activation and transformation of molecular nitrogen (N) by metal hydride species has attracted widespread attention due to its critical role in nitrogen fixation. Herein, the reactions between tantalum deuteride cluster anions TaD and N were investigated experimentally and theoretically. An unprecedented reaction channel of the liberation of a single D atom was observed and much superior reactivity was identified for TaD.

Pyrolysis of mass-selected (VO)O (N = 1-6) clusters in a high-temperature linear ion trap reactor.

A high-temperature linear ion trap that can stably run up to 873 K was newly designed and installed into a homemade reflectron time-of-flight mass spectrometer coupled with a laser ablation cluster source and a quadrupole mass filter. The instrument was used to study the pyrolysis behavior of mass-selected (VO)O (N = 1-6) cluster anions and the dissociation channels were clarified with atomistic precision. Similar to the dissociation behavior of the heated metal oxide cluster cations reported in literature, the desorption of either atomic oxygen atom or molecular O prevailed for the (VO)O clusters with N = 2-5 at 873 K.

Development and evaluation of a predictive nomogram for survival in heat stroke patients: a retrospective cohort study.

Background: This study aimed to establish an effective nomogram to predict the survival of heat stroke (HS) based on risk factors.

Methods: This was a retrospective, observational multicenter cohort study. We analyzed patients diagnosed with HS, who were treated between May 1 and September 30, 2018 at 15 tertiary hospitals from 11 cities in Northern China.

Mutual functionalization of dinitrogen and methane mediated by heteronuclear metal cluster anions CoTaC.

The direct coupling of dinitrogen (N) and methane (CH) to construct the N-C bond is a fascinating but challenging approach for the energy-saving synthesis of N-containing organic compounds. Herein we identified a likely reaction pathway for N-C coupling from N and CH mediated by heteronuclear metal cluster anions CoTaC , which starts with the dissociative adsorption of N on CoTaC to generate a Ta -N (terminal-nitrogen) Lewis acid-base pair (LABP), followed by the further activation of CH by CoTaCN to construct the N-C bond. The N[triple bond, length as m-dash]N cleavage by CoTaC affording two N atoms with strong charge buffering ability plays a key part, which facilitates the HC-H cleavage the LABP mechanism and the N-C formation a CH migration mechanism.