Deep Insight of Design,Mechanism,and Cancer Theranostic Strategy of Nanozymes

Since the discovery of enzyme-like activity of Fe3O4 nanoparticles in 2007,nanozymes are becoming the promising substitutes for natural enzymes due to their advantages of high catalytic activity,low cost,mild reaction conditions,good stability,and suitable for large-scale production.Recently,with the cross fusion of nanomedicine and nanocatalysis,nanozyme-based theranostic strategies attract great attention,since the enzymatic reactions can be triggered in the tumor microenvironment to achieve good curative effect with substrate specificity and low side effects.Thus,various nanozymes have been developed and used for tumor therapy.In this review,more than 270 research articles are discussed systematically to present progress in the past five years.First,the discovery and development of nanozymes are summarized.Second,classification and catalytic mechanism of nanozymes are discussed.Third,activity prediction and rational design of nanozymes are focused by highlighting the methods of density functional theory,machine learning,biomimetic and chemical design.Then,synergistic theranostic strategy of nanozymes are introduced.Finally,current challenges and future prospects of nanozymes used for tumor theranostic are outlined,including selectivity,biosafety,repeatability and stability,in-depth catalytic mechanism,predicting and evaluating activities.

Recent advances in cobalt phosphide-based materials for electrocatalytic water splitting:From catalytic mechanism and synthesis method to optimization design

Electrochemical water splitting has long been considered an effective energy conversion technology for trans-ferring intermittent renewable electricity into hydrogen fuel,and the exploration of cost-effective and high-performance electrocatalysts is crucial in making electrolyzed water technology commercially viable.Cobalt phosphide(Co-P)has emerged as a catalyst of high potential owing to its high catalytic activity and durability in water splitting.This paper systematically reviews the latest advances in the development of Co-P-based materials for use in water splitting.The essential effects of P in enhancing the catalytic performance of the hydrogen evolution reaction and oxygen evolution reaction are first outlined.Then,versatile synthesis techniques for Co-P electrocatalysts are summarized,followed by advanced strategies to enhance the electrocatalytic performance of Co-P materials,including heteroatom doping,composite construction,integration with well-conductive sub-strates,and structure control from the viewpoint of experiment.Along with these optimization strategies,the understanding of the inherent mechanism of enhanced catalytic performance is also discussed.Finally,some existing challenges in the development of highly active and stable Co-P-based materials are clarified,and pro-spective directions for prompting the wide commercialization of water electrolysis technology are proposed.

The hydrogen storage performance and catalytic mechanism of theMgH_(2)-MoS_(2)composite

In this work,we synthesized MoS_(2)catalyst via one-step hydrothermal method,and systematically investigated the catalytic effect of MoS_(2)on the hydrogen storage properties of MgH_(2).The MgH_(2)-5MoS_(2)composite milled for 5 h starts to release hydrogen at 259℃.Furthermore,it can desorb 4.0 wt.%hydrogen within 20 min at 280℃,and absorb 4.5 wt.%hydrogen within 5 min at 200℃.Mo and MoS_(2)coexistedin the ball milled sample,whereas only Mo was kept in the sample after dehydrogenation and rehydrogenation,which greatly weakens theMg-H bonds and facilitates the dissociation of MgH_(2)on the surface of Mo(110).The comparative study show that the formed MgS has nocatalytic effect for MgH_(2).We believed that the evolution and the catalytic mechanism of MoS_(2)will provide the theoretical guidance for theapplication of metal sulfide in hydrogen storage materials.

The newly-assisted catalytic mechanism of surface hydroxyl species performed as the promoter in syngas-to-C2 species on the Cu-based bimetallic catalysts

In the conversion process of syngas-to-C_(2)species,the OH species are inevitably produced accompanying the production of key intermediates CH_(x)(x=1-3),traditionally,the function of surface OH species is generally accepted as the hydrogenating reactive species.This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C_(2)species on Cu-based catalysts.DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CH_(x)production on the MCu(M=Co,Fe,Rh)catalysts can stably exist to form OH/MCu catalysts,on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CH_(x)(x=1-3)compared to MCu catalysts,but also significantly suppressed CH_(3)OH production,providing enough CH_(x)sources to favor the production of C_(2)hydrocarbons and oxygenates.Correspondingly,the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance,attributing to the unique electronic micro-environment of the catalysts under the interaction of surface OH species.This new mechanism is called as OH-assisted catalytic mechanism,which may be applied in the reaction systems related to the generation of OH species.

Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

This study explores how the chemical interaction between magnesium hydride(MgH_(2))and the additive CrO_(3) influences the hydrogen/lithium storage characteristics of MgH_(2).We have observed that a 5 wt.%CrO_(3) additive reduces the dehydrogenation activation energy of MgH_(2) by 68 kJ/mol and lowers the required dehydrogenation temperature by 80℃.CrO_(3) added MgH_(2) was also tested as an anode in an Li ion battery,and it is possible to deliver over 90%of the total theoretical capacity(2038 mAh/g).Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH_(2).In depth characterization study by X-ray diffraction(XRD)technique provides convincing evidence that the CrO_(3) additive interacts with MgH_(2) and produces Cr/MgO byproducts.Gibbs free energy analyses confirm the thermodynamic feasibility of conversion from MgH_(2)/CrO_(3) to MgO/Cr,which is well supported by the identification of Cr(0)in the powder by X ray photoelectron spectroscopy(XPS)technique.Through high resolution transmission electron microscopy(HRTEM)and energy dispersive spectroscopy(EDS)we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt nanoparticles.There is also convincing ground to consider that MgO rock salt accommodates Cr in the lattice.These observations support the argument that creation of active metal–metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH_(2),both for the improved storage of hydrogen and lithium.

A Review on Metal-and Metal Oxide-Based Nanozymes:Properties,Mechanisms,and Applications

Since the ferromagnetic(Fe_(3)O_(4))nanoparticles were firstly reported to exert enzyme-like activity in 2007,extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies.As promising alterna-tives for natural enzymes,nanozymes have broadened the way toward clinical medicine,food safety,environmental monitoring,and chemical production.The past decade has witnessed the rapid development of metal-and metal oxide-based nanozymes owing to their remarkable physicochemical proper-ties in parallel with low cost,high stability,and easy storage.It is widely known that the deep study of catalytic activities and mechanism sheds sig-nificant influence on the applications of nanozymes.This review digs into the characteristics and intrinsic properties of metal-and metal oxide-based nanozymes,especially emphasizing their catalytic mechanism and recent applications in biological analysis,relieving inflammation,antibacterial,and cancer therapy.We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

Revealing the catalytic mechanism of an ionic liquid with an isotope exchange method

The alkylation mechanism catalyzed by an ionic liquid （as a Lewis acid） may be different from the traditional alkylation mechanism catalyzed by Br nsted acid,especially as their initiation steps are still not clear.In this paper,an isotope exchange method is used to investigate the catalytic mechanism of AlCl 3 /butyl-methyl-imidazolium chloride ionic liquid in the alkylation of benzene with 1-dodecene.The proposed catalytic mechanism was confirmed by analysis of ionic liquid before and after reaction and of the alkylation products of deuterated benzene （C 6 D 6） with 1-dodecene.The proposed mechanism consists of the equilibrium reaction between [Al 2 Cl 7 ] ＋H ＋ and [AlHCl 3 ] ＋ ＋[AlCl 4 ],in which the Br nsted acid [AlHCl 3 ] ＋ is supplied by the reaction of 2-H on the imidazolium ring and [Al 2 Cl 7 ].The alkylation reaction is initiated by the Br nsted acid [AlHCl 3 ] ＋ which reacts with 1-dodecene to form a carbonium ion,then the carbonium ion reacts with benzene to form an unstable σ complex,leading to the formation of 2-phenyldodecane.

Catalysts for the hydrogen evolution reaction in alkaline medium:Configuring a cooperative mechanism at the Ag-Ag_(2)S-MoS_(2) interface

Designing electrocatalysts for HER in alkaline conditions to overcome the sluggish kinetics associated with the additional water dissociation step is a recognized challenge in promoting the hydrogen economy.To this end,delicately tuning the atomic-scale structure and surface composition of nanoparticles is a common strategy and,specifically,making use of hybrid structures,can produce synergistic effects that lead to highly active catalysts.Here,we present a core-shell catalyst of Ag@MoS_(2)that shows promising results towards the hydrogen evolution reaction(HER)in both 0.5 M H_(2)SO_(4)and 0.5 M KOH.In this hybrid structure,the MoS_(2)shell is strained and defective,and charge transfer occurs between the conductive core and the shell,contributing to the electrocatalytic activity.The shelling process results in a large fraction of Ag_(2)S in the cores,and adjusting the relative fractions of Ag,Ag_(2)S,and MoS_(2)leads to improved catalytic activity and fast charge-transfer kinetics.We suggest that the enhancement of alkaline HER is associated with a cooperative effect of the interfaces,where the Ag(Ⅰ)sites in Ag_(2)S drive the water dissociation step,and the formed hydrogen subsequently recombines on the defective MoS_(2)shell.This study demonstrates the benefits of hybrid structures as functional nanomaterials and provides a scheme to activate MoS_(2)for HER in alkaline conditions.

Recent Advances in Constructing Interfacial Active Catalysts Based on Layered Double Hydroxides and Their Catalytic Mechanisms

The interaction between the metal and the support of supported metal catalysts, which are widely used in industry, is the primary focus of the study of such catalysts. With the developing understanding of the metal–support interaction, the intrinsic factor that influences the catalytic performance has been determined to be the structure of interfacial sites. Layered double hydroxides(LDHs, a class of two-dimensional layered anion clay) possess several unique characteristics, such as the following:(1) tunable elemental component, homogeneous distribution of metal cations.(2) anchoring eff ect.(3) multiple layered structure for exfoliation or intercalation and special memory eff ect;and(4) internal/external confinement eff ects during topological transformation. Taking LDHs and their derivatives as precursors or supports shows superior advantages in designing interfacial active catalysts with tunable properties. Therefore, this review is mainly focused on constructing interfacial active catalysts by LDHs and revealing the interfacial eff ects(including electronic, geometric, and bifunctional eff ects) on the catalytic performance that will provide new perspectives and approaches for the development of heterogeneous catalysis.

A first-principles study of the catalytic mechanism of the dehydriding reaction of LiNH_2 through adding Ti catalysts

Experiments on a ball milled mixture with a 1：1 molar ratio of LiNH2 and LiH with a small amount （1 mol %） of Ti^nano, TICl3 and TiO2^nano have revealed a superior catalytic effect on Li N H hydrogen storage materials. In the x-ray diffraction profiles, no trace of Ti^nano, TICl3 and TiO2^nano was found in these doped composites, by which we deduced that Ti atoms enter LiNH2 by partial element substitution. A first-principles plane-wave pseudopotential method based on density functional theory has been used to investigate the catalytic effects of Ti catalysts on the dehydrogenating properties of LiNH2 system. The results show that Ti substitution can reduce the dehydrogenation reaction activation energy of LiNH2 and improve the dehydrogenating properties of LiNH2. Based on the analysis of the density of states and overlap populations for LiNH2 before and after Ti substitution, it was found that the stability of the system of LiNH2 is reduced, which originates from the increase of the valence electrons at the Fermi level （EF） and the decrease of the highest occupied molecular orbital （HOMO） lowest unoccupied molecular orbital （LUMO） gap （△EH-L） near EF. The catalytic effect of Ti on the dehydrogenating kinetics of LiNH2 may be attributed to the reduction of average populations between N-H per unit bond length （nm-1）, which leads to the reduction of the chemical bond strength of NH.

A Review on the Mechanism of NO Selective Catalytic Oxidation

In this paper,the research status and catalytic mechanism of activated carbon catalysts,molecular sieve catalysts,noble metal catalysts and transition metal oxide catalysts used for NO catalytic oxidation were studied to provide reference for future research.

Bullet-like vanadium-based MOFs as a highly active catalyst for promoting the hydrogen storage property in MgH_(2)

The practical application of magnesium hydride(MgH_(2))was seriously limited by its high desorption temperature and slow desorp-tion kinetics.In this study,a bullet-like catalyst based on vanadium related MOFs(MOFs-V)was successfully synthesized and doped with MgH_(2) by ball milling to improve its hydrogen storage performance.Microstructure analysis demonstrated that the as-synthesized MOFs was consisted of V_(2)O_(3) with a bullet-like structure.After adding 7wt%MOFs-V,the initial desorption temperature of MgH_(2) was reduced from 340.0 to 190.6℃.Besides,the MgH_(2)+7wt%MOFs-V composite released 6.4wt%H_(2) within 5 min at 300℃.Hydrogen uptake was started at 60℃under 3200 kPa hydrogen pressure for the 7wt%MOFs-V containing sample.The desorption and absorption apparent activity energies of the MgH_(2)+7wt%MOFs-V composite were calculated to be(98.4±2.9)and(30.3±2.1)kJ·mol^(-1),much lower than(157.5±3.3)and(78.2±3.4)kJ·mol^(−1) for the as-prepared MgH_(2).The MgH_(2)+7wt%MOFs-V composite exhibited superior cyclic property.During the 20 cycles isothermal dehydrogenation and hydrogenation experiments,the hydrogen storage capacity stayed almost unchanged.X-ray diffraction(XRD)and X-ray photoelectron spectrometer(XPS)measurements confirmed the presence of metallic vanadium in the MgH_(2)+7wt%MOFs-V composite,which served as catalytic unit to markedly improve the hydrogen storage properties of Mg/MgH_(2) system.

Metal organic framework supported niobium pentoxide nanoparticles with exceptional catalytic effect on hydrogen storage behavior of MgH_(2)

Nb_(2)O_(5)nanoparticles with an average particle size of 10 nm supported on a rhombic dodecahedral metal organic framework(MOF)were successfully synthesized by a facile one-pot hydrothermal reaction and subsequent calcination process.Experimental results demonstrated that the prepared catalyst drastically improved the hydrogen storage behavior of MgH_(2).7 wt%Nb_(2)O_(5)@MOF doped MgH_(2)started to desorb hydrogen at 181.9℃and 6.2 wt%hydrogen could be released within 2.6 min and 6.3 min at 275℃and 250℃,respectively.The fully dehydrogenated composite also displayed excellent hydrogenation by decreasing the onset absorption temperature to 25℃and taking up4.9 wt%and 6.5 wt%hydrogen within 6 min at 1750C and 1500C,respectively.Moreover,the corresponding activation energy was calculated to be 75.57±4.16 kJ mol^(-1)for desorption reaction and 51.38±1.09 kJ mol^(-1)for absorption reaction.After 20 cycles,0.5 wt%hydrogen capacity was lost for the MgH_(2)+7 wt%Nb_(2)O_(5)@MOF composite,much lower than 1.5 wt%of the MgH_(2)+7 wt%Nb_(2)O_(5)composite.However,the addition of Nb_(2)O_(5)@MOF had limited effect on reducing the dehydrogenation enthalpy of MgH_(2).Microstructure analysis revealed that Nb_(2)O_(5)particles were uniformly distributed on surface of the MgH_(2)matrix and synergistically improved the hydrogen storage property of MgH_(2)with MOF.

Recent progress and challenges in structural construction strategy of metal-based catalysts for nitrate electroreduction to ammonia

Ammonia plays an essential role in human production and life as a raw material for chemical fertilizers.The nitrate electroreduction to ammonia reaction(NO_(3)RR)has garnered attention due to its advantages over the Haber-Bosch process and electrochemical nitrogen reduction reaction.Therefore,it represents a promising approach to safeguard the ecological environment by enabling the cycling of nitrogen species.This review begins by discussing the theoretical insights of the NO_(3)RR.It then summarizes recent advances in catalyst design and construction strategies,including alloying,structure engineering,surface engineering,and heterostructure engineering.Finally,the challenges and prospects in this field are presented.This review aims to guide for enhancing the efficiency of electrocatalysts in the NO_(3)RR,and offers insights for converting NO_(3)-to NH_(3).

The age of vanadium-based nanozymes: Synthesis, catalytic mechanisms, regulation and biomedical applications

Nanomaterials with enzyme-mimic(nanozyme) activity have garnered considerable attention as a potential alternative to natural enzymes, thanks to their low preparation cost, high activity, ease of preservation, and unique physicochemical properties. Vanadium(V) is a transition metal that integrates the benefits of valence-richness, low cost, and non-toxicity, making it a desirable candidate for developing a range of emerging nanozymes. In this review, we provide the first systematic summary of recent research progress on V-based nanozymes. First, we summarize the preparation of V-based nanozymes using both top-down and bottom-up synthesis methods. Next, we review the mechanism of V-based nanozymes that mimic the activity of various enzymes. We then discuss methods for regulating V-based nanozyme activity, including morphology, size, valence engineering, defect engineering, external triggering, and surface engineering. Afterward, we outline various biomedical applications, including therapeutic, anti-inflammatory, antibacterial, and biosensing. Finally, we prospect the challenges and countermeasures for V-based nanozymes based on their development. By summarizing recent research progress on V-based nanozymes, we hope to provide useful insights for researchers to further explore their potential applications and overcome their existing challenges.

Progress and key challenges in catalytic combustion of lean methane

As a primary type of clean energy,methane is also the second most important greenhouse gas after CO_(2)due to the high global warming potential.Large quantities of lean methane(0.1–1.0 vol%)are emitted into the atmosphere without any treatment during coal mine,oil,and natural gas production,thus leading to energy loss and greenhouse effect.In general,it is challenging to utilize lean methane due to its low concentration and flow instability,while catalytic combustion is a vital pathway to realize an efficient utilization of lean methane owing to the reduced emissions of polluting gases(e.g.,NOxand CO)during the reaction.In particular,to efficiently convert lean methane,it necessitates both the designs of highly active and stable heterogeneous catalysts that accelerate lean methane combustion at low temperatures and smart reactors that enable autothermal operation by optimizing heat management.In this review,we discuss the in-depth development,challenges,and prospects of catalytic lean methane combustion technology in various configurations,with particular emphasis on heat management from the point of view of material design combined with reactor configuration.The target is to describe a framework that can correlate the guiding principles among catalyst design,device innovation and system optimization,inspiring the development of groundbreaking combustion technology for the efficient utilization of lean methane.

Catalytic effect of Ni@rGO on the hydrogen storage properties of MgH2

Uniform-uispersed Ni nanoparticics(NPs)anchored on reduced graphene oxide(Ni@rGO)catalyzed MgH2(MH-Ni@rGO)has been fabricated by mechanical milling.The effects of milling time and Ni loading amount on the hydrogen storage properties of MgH2 have been investigated.The initial hydrogen desorption temperature of MgH2 catalyzed by 10 wt.%Ni4@rGO6 for milling 5 h is significantly decreased from 251℃ to 190℃.The composite can absorb 5.0 wt.%hydrogen in 20 min at 100℃,while it can desorb 6.1 wt.%within 15 min at 300℃.Through the investigation of the phase transformation and dehydrogenation kinetics during hydrogen ab/desorption cycles,we found that the in-situ formed Mg2Ni/Mg2NiH4 exhibited better catalytic effect than Ni.When Ni loading amount is 45 wt.%,the rGO in Ni@rGO catalysts can prevent the reaction of Ni and Mg due to the strong interaction between rGO and Ni NPs.

In situ catalytic upgrading of heavy crude oil through low-temperature oxidation

The low-temperature catalytic oxidation of heavy crude oil（Xinjiang Oilfield,China） was studied using three types of catalysts including oil-soluble,watersoluble,and dispersed catalysts.According to primary screening,oil-soluble catalysts,copper naphthenate and manganese naphthenate,are more attractive,and were selected to further investigate their catalytic performance in in situ upgrading of heavy oil.The heavy oil compositions and molecular structures were characterized by column chromatography,elemental analysis,and Fourier transform infrared spectrometry before and after reaction.An Arrhenius kinetics model was introduced to calculate the rheological activation energy of heavy oil from the viscosity-temperature characteristics.Results show that the two oil-soluble catalysts can crack part of heavy components into light components,decrease the heteroatom content,and achieve the transition of reaction mode from oxygen addition to bond scission.The calculated rheological activation energy of heavy oil from the fitted Arrhenius model is consistent with physical properties of heavy oil（oil viscosity and contents of heavy fractions）.It is found that the temperature,oil composition,and internal molecular structures are the main factors affecting its flow ability.Oil-soluble catalyst-assisted air injection or air huff-n-puff injection is a promising in situ catalytic upgrading method for improving heavy oil recovery.

Activation of hydrogen peroxide by molybdenum disulfide as Fenton-like catalyst and cocatalyst:Phase-dependent catalytic performance and degradation mechanism

Molybdenum disulfide(Mo S_(2))has attracted great attention in hydrogen peroxide(H_(2)O_(2))activation as a Fenton-like catalyst and cocatalyst,but the distinct mechanism of generating^(·)OH remains unclear.In this paper,the metallic 1T phase and semiconducting 2H phase of Mo S_(2)nanosheets were prepared and applied in MoS_(2)/H_(2)O_(2)and MoS_(2)/Fe^(2+)/H_(2)O_(2)systems with and without light irradiation.Compared with2H-MoS_(2),1T-MoS_(2)exhibited superior removal rates in degrading organic pollutants in the two systems under light irradiation.However,the phase had little effect on activating H_(2)O_(2)in the Mo S_(2)/H_(2)O_(2)system under dark conditions.This is because it was difficult for the surface^(·)OH_(ads)generated in the Mo S_(2)/H_(2)O_(2)system to diffuse into solution,while the^(·)OH_(free)radicals were mainly responsible for degrading organic pollutants.When introducing light irradiation,external energy may accelerate the desorption of^(·)OH_(ads)into^(·)OH_(free.)Interestingly,the conversion between Mo^(4+)and Mo^(5+)triggered the decomposition of H_(2)O_(2)in the Fenton-like reaction,while the cycle of Mo^(4+)/Mo^(6+)promoted the regeneration of Fe^(3+)when employing 1T-MoS_(2)as a cocatalyst.Meanwhile,the 1T-MoS_(2)catalysts exhibited excellent stability and ability to degrade various organics in the two systems.This work offers deeper insight into the Mo S_(2)-based Fenton-like and cocatalytic mechanisms.

A highly selective C-rhamnosyltransferase from Viola tricolor and insights into its mechanisms

C-Glycosides are important natural products with various bioactivities.In plant biosynthetic pathways,the C-glycosylation step is usually catalyzed by C-glycosyltransferases(CGTs),and most of them prefer to accept uridine 5’-diphosphate glucose(UDP-Glc)as sugar donor.No CGTs favoring UDP-rhamnose(UDP-Rha)as sugar donor has been reported,thus far.Herein,we report the first selective C-rhamnosyltransferase VtCGTc from the medicinal plant Viola tricolor.VtCGTc could efficiently catalyze C-rhamnosylation of 2-hydroxynaringenin 3-C-glucoside,and exhibited high selectivity towards UDP-Rha.Mechanisms for the sugar donor selectivity of VtCGTc were investigated by molecular dynamics(MD)simulations and molecular mechanics with generalized Born and surface area solvation(MM/GBSA)binding free energy calculations.Val144 played a vital role in recognizing UDP-Rha,and the V144T mutant could efficiently utilize UDP-Glc.This work provides a new and efficient approach to prepare flavonoid C-rhamnosides such as violanthin and iso-violanthin.