Catalytic Site Research Articles

Boosting low-temperature NH3-SCR performance via mixed-valence cobalt dual active sites

Nitrogen oxides (NOx) have become a critical environmental concern, necessitating the development of highly efficient catalysts for temperature which is lower than 300 °C. Selective catalytic reduction with NH3 (NH3-SCR) is a process where ammonia is the reducing agent for selective catalytic reduction of nitrogen oxides in exhaust gases. The mechanism-property relationship between catalytic active sites and low-temperature denitrification efficiency, however, remains unclear. In this study, we synthesized a series of cobalt-modified nanoparticle catalysts using a scalable citric acid sol-gel method and conducted comprehensive characterizations. Our findings indicate that an optimal cobalt doping rate significantly enhances catalytic activity due to the synergistic effects of reduced nanoparticle size and the dual active sites of Co0/Co2+. Specifically, at a cobalt doping ratio of 1.0, the catalyst demonstrates peak SCR activity, achieving 85.5% NOₓ conversion at 120 °C and complete conversion at 150 °C. These cobalt-modified nanoparticle catalysts feature high deposition of doped Co ions on their surfaces, predominantly as metallic cobalt and CoOx nanoclusters. Compared to undoped samples, the cobalt-doped nanoparticle catalysts exhibit a greater specific surface area, increased acidity, enhanced chemisorbed oxygen, and improved redox properties, all contributing to superior denitrification efficacy. Additionally, Density Functional Theory (DFT) calculations provide assertive evidence into the reaction mechanism, showing that Co2+ sites effectively adsorb and activate NH₃, while Co0 sites are crucial for NO adsorption and activation. The synergistic interaction between Co2+ and Co0 facilitates NN coupling, enhancing overall reaction efficiency. These findings underscore the potential of cobalt-modified catalysts for practical industrial applications, offering robust performance over a wide temperature range and meeting stringent environmental regulations.

Integrated CO2 Capture and Utilization: Selection, Matching, and Interactions between Adsorption and Catalytic Sites

Integrated CO₂ Capture and Utilization: Selection, Matching, and Interactions between Adsorption and Catalytic Sites

Comparison between endogenous and exogenous nitrogen of nitrogen-doped carbon catalyst in the process of activating PMS

BackgroundAdvanced oxidation processes (AOPs) based on sulfate radicals (SO4•–) have proven to be highly effective in degrading organics in wastewater. Carbon-based materials have emerged as promising catalysts for activating persulfate, which generates environmentally friendly sulfate radicals (SO4•–), for remediation purposes. The nitrogen doping technique is an effective method for site-specific regulation and can significantly enhance the performance of carbon-based catalysts, which could promote the application of carbon-based catalysts in the future. Endogenous and exogenous nitrogen sources can provide nitrogen sources for N doping. However, there are few reports on the comparison of the structure and catalytic mechanism of these two types of N-doped biochar. It is also of great significance to reveal the mechanisms of constructing catalytic sites using endogenous and exogenous nitrogen. MethodsHerein, the preparation of endogenous nitrogen-doped biochar (BC) was achieved by using soybean as the precursor material, which is rich in natural nitrogen-containing components of proteins. Subsequently, the BC was doped by mixing it with urea and pyrolysis, resulting in the preparation of exogenous nitrogen-doped biochar (NBC). Significant findingsThe characterization of XRD and HRTEM showed that g-C3N4 formed in NBC. The results of catalytic degradation and quenching experiments demonstrate that the exogenous nitrogen-doped catalysts have a better performance than endogenous nitrogen-doped catalysts. The OFL removal rate in BC/PMS was higher than that in the BC/PMS system (71.68% vs. 61.83 %). The kobs in NBC/PMS are also higher than that in BC/PMS (0.00943 min−1vs. 0.01369 min−1). The NBC could be a promising catalyst for PMS activation in practical application. DFT results showed that the g-C3N4 generated from exogenous nitrogen can improve PMS activation performance in the g-C3N4/graphene bilayer structure. The influence on the charge distribution of surrounding carbon materials makes endogenous nitrogen doping a good choice for optimizing the local performance of the material in the absence of natural nitrogen components.

Unveiling the degradation mechanism of cathodic MoS2/C electrocatalysts for PEMWE applications

Molybdenum dichalcogenides (MoS2) are promising non-noble alternatives to replace platinum (Pt) for Hydrogen Evolution Reaction (HER) electrocatalysis in Proton Exchange Membrane Water Electrolyzers (PEMWE). The knowledge acquired on this class of catalyst for hydrodesulfurization (HDS) reactions has enabled significant advances in designing active MoS2 for HER. However, the stability of MoS2 in the dynamic operating conditions of a PEMWE coupled to renewable energy sources is often overlooked in the literature and is the focus of the present work. Herein, using nano slabs of 2H MoS2 supported on high surface area carbon, we dynamically monitored Mo dissolution trends both under HER conditions and at more anodic potentials to mimic start-ups and shut-downs of a PEMWE device. We report minimal Mo dissolution under HER conditions but it continuously increased with higher electrode potentials. In particular, Mo dissolution peaked during the irreversible oxidation from Mo(IV) to Mo(VI) starting at E = 0.7 VRHE which in turn fully annihilates HER activity. Since no change in Mo and S surface composition was observed, the decline in HER activity was attributed to the continuous exfoliation of the 2D MoS2 stacked layers induced by oxidation/dissolution of Mo. Additionally, our findings indicate that Mo cations can redeposit onto the cathode catalytic layer, forming a Mo blue film primarily composed of Mo(VI) species. This redeposition hampers HER performance by blocking catalytic sites and diminishing the catalyst's overall efficiency. These insights demonstrate the need to avoid excursions above E = 0.6 VRHE for the safe use of MoS2 cathode catalyst in PEMWE.

New insights into the catalyzed ozonation mechanism of a hydroxyl riched goethite: Contributions of H2O2 and surface Fe2+

Fe-based catalysts have been widely used to catalyze ozonation during water treatment. Among these catalysts, goethite (α-FeOOH) is of concern for the properties of low cost, easy availability, and excellent performance. In general, the surface hydroxyl groups of goethite are believed to be crucial catalytic sites. However, the contributions of Fe2+ on the goethite surface and H2O2 produced from pollutant degradation have rarely been mentioned. In this study, a goethite with rich surface hydroxyl was fabricated to remove aromatics by O3 catalysis. Probe and quenching experiments together proved that although the •OH was produced less than the O2•⁻ and 1O2 in the catalytic system, it contributed about 95 % of the target removal. EDTA complexation and heating experiments suggested that when the surface Fe2+ of the catalyst was destroyed, although the Fe-site hydroxyl or the vacancy hydroxyl of the catalyst was retained, its catalytic activity was reduced greatly. The outcomes of degradation kinetics of acetic acid further confirmed that, in the catalytic process, most of •OH originated from the reaction of Fe2+ reducing HO2• and Fe2+ ozonation, while the surface hydroxyl contributed less than 44.7 %. Moreover, as the main source of HO2•, the role of H2O2 produced from aromatics degradation cannot be ignored. The detection of H2O2 precursors in the degradation byproducts further confirmed this opinion. Finally, an efficient circular route for •OH production was proposed. This may be beneficial for the development of efficient Fe-based catalysts.

Functionalized construction of multiple active centers for durability controlling during catalytic combustion of chlorinated aromatic hydrocarbons

The catalytic combustion of chlorine-containing VOCs primarily encounters the bottleneck of catalyst poisoning by chlorine, thereby impeding the further industrial application of this technology. The development of multi-active catalytic materials for discerning chlorine fixation, chlorine transfer, deep oxidation during elimination of chlorine-containing VOCs can mitigate catalyst chlorination and enhance stability. Herein, we utilizing LDHs as catalyst precursors and successfully synthesized flower-like Co2FexCr1-xOy catalyst with different functionalized reaction centers. The addition of Cr improved the surface lattice oxygen, oxygen vacancies, and acid sites of catalyst. The removal efficiency of CB can be achieved >90 % at 247 °C (WHSV = 33000 mL · g−1·h−1). The fixation of dissociated chlorine contributed by Cr not only enhances oxidation performance and directional adsorption of chlorine, but also improves carbon deposition resistance and catalyst sintering resistance significantly. Compared with Co2Fe1Oy, Co2Fe0.67Cr0.33Oy catalyst achieves a remarkable threefold reduction in surface carbon deposition. The DFT calculation revealed that water dissociation energy over the Co site is −0.72 eV, which is significantly lower than Fe (−0.59 eV) and Cr (−0.17 eV), facilitating water dissociation and subsequently removes a substantial amount of accumulated chlorine on Cr to form HCl. With the help of In situ DRIFT and GC/MS analysis, we found the efficient removal of chlorine atoms enhances the exposure of active sites on the catalyst surface with hydrolyzed hydroxyl group, which facilitating the conversion of aromatic hydrocarbons into a greater quantity of maleate and carboxylate species. This phenomenon is beneficial for the subsequent mineralization process of chlorobenzene. This work provide valuable insights for multi-active site catalysis mechanism in practical applications aimed at eliminating chlorinated organic waste gases from industrial emissions.

A Highly Conjugated Nickel(II)-Acetylide Framework for Efficient Photocatalytic Carbon Dioxide Reduction.

The incorporation of transition-metal single atoms as molecular functional entities into the skeleton of graphdiyne (GDY) to construct novel two-dimensional (2D) metal-acetylide frameworks, known as metalated graphynes (MGYs), is a promising strategy for developing efficient catalysts, which can combine the tunable charge transfer of GDY frameworks, the catalytic activity of metal and the precise distribution of single metallic centers. Herein, four highly conjugated MGY photocatalysts based on NiII, PdII, PtII, and HgII were synthesized for the first time using the 'bottom-up' strategy through the use of M-C bonds (-C≡C-M-C≡C-). Remarkably, the NiII-based graphyne (TEPY-Ni-GY) exhibited the highest CO generation rate of 18.3 mmol g-1 h-1 and a selectivity of 98.8%. This superior performance is attributed to the synergistic effects of pyrenyl and -C≡C-Ni(PBu3)2-C≡C- moieties. The pyrenyl block functions as an intramolecular π-conjugation channel, facilitating kinetically favorable electron transfer, while the -C≡C-Ni(PBu3)2-C≡C- moiety serves as the catalytic site that enhances CO2 adsorption and activation, thereby suppressing competitive hydrogen evolution. This study provides a new perspective on MGY-based photocatalysts for developing highly active and low-cost catalysts for CO2 reduction.

NixB/Mo0.8B3 Nanorods Encapsulated by a Boron‐Rich Amorphous Layer for Universal pH Water Splitting at the Ampere Level

AbstractHeterostructured interfaces are crucial to electrocatalysts for water splitting. Herein, coral‐like multiheterostructured NixB/Mo0.8B3 (NMB) nanorods encapsulated by a boron‐rich amorphous layer are prepared for water splitting. Density‐functional theory (DFT) calculations indicate that the NMB interface adjusts the d‐band center and electronic structure of the molybdenum sites. Owing to the strong electronic coupling between Ni, Mo, and B at the heterojunction, large number of exposed catalytic active sites, as well as the special hydrophilic characteristics endowed by the surrounding amorphous layer, the NMB catalyst exhibits remarkable universal‐pH hydrogen evolution reaction (HER) activity with low overpotentials (η) of 15, 26, and 83 mV to deliver 10 mA cm−2 in basic, acid, and neutral media, respectively, and outstanding oxygen evolution reaction (OER) characteristics in the basic medium with η10 and η500 of 170 and 420 mV, respectively. The unique self‐supporting 3D hierarchical interconnected structure facilitates mass transport thus leading to high mechanical stability for 450 and 200 h in HER and OER at ≈1000 mA cm−2. More importantly, the NMB exhibits excellent performance toward overall‐water electrolysis as a bifunctional catalyst with ultralow cell voltages of 1.45/1.56/1.85 V @ 10/100/1000 mA cm−2, demonstrating the large potential in industrial water splitting applications.

Oriented Crystal Polarization Tuning Bulk Charge and Single-Site Chemical State for Exceptional Hydrogen Photo-Production.

Rapid bulk charge recombination and mediocre surface catalytic sites harshly restrict the photocatalytic activities. Herein, the aforementioned concerns are well addressed by coupling macroscopic spontaneous polarization and atomic-site engineering of CdS single-crystal nanorods for superb H2 photo-production. The oriented growth of CdS nanorods along the polar axis, vectorially superimposing substantial polar units with orderly arrangement, renders a strong polarization electric field (20.1 times enhancement), which boosts bulk charge separation with an efficiency up to 72.4% (80.4-fold). Remarkably, polarization electric field alters the chemical state of Pt single sites by orderly reducing the binding energy of Pt atom with stepwise polarization enhancement of CdS substrate, which increases the onsite electron density of Pt from 10.232 to 10.261e- and *H key intermediates, providing preponderant Volmer-Tafel/Volmer-Heyrovsky reaction pathways with significantly decreased energy barriers for H2 production. Thus, highly polarized CdS nanorods with atomically dispersed Pt sites perform an outstanding H2 space-time yield of 118.5mmol g-1 h-1 and apparent quantum efficiency of 57.7% at λ = 420nm, and a record-high H2 turnover frequency of 57798.4 h-1, being one of the best catalysts for photocatalytic H2 evolution. This work highlights the function of polarization in manipulating charge separation and catalytic reaction.

Accelerating the Reduction Kinetics of V4+ to V3+ on Atomically Fe─N4 Decorated Carbon Nanotubes for Vanadium Electrolyte Preparation.

The high manufacturing cost of vanadium electrolytes is caused by the sluggish kinetics of V4+ to V3+, which restricts the commercialization of all vanadium flow batteries (VFBs). Here, density functional theory calculations first reveal the detailed reaction pathway and point out the rate-determined step by the desorption of the end product [V(H2O)6]3+. Catalytic site engineering at the molecular level can optimize the adsorption energy of [V(H2O)6]3+ to boost the kinetics. Furthermore, iron single-atoms embedded nitrogen-doped carbon nanotubes (FeSA/NCNT) are designed to decrease the adsorption energy of [V(H2O)6]3+. The reaction rate constant of FeSA/NCNT toward V4+ to V3+ is 1.62 × 10-7cm s-1, 37.5 times that of the commercial carbon catalyst. Therefore, the energy consumption is reduced by 22.5%. Meanwhile, the prepared vanadium electrolyte is of high quality with the ideal oxidation state of + 3.5 without impurities. This work reveals the catalytic mechanism of V4+ to V3+ and proposes a simple but practical strategy to reduce the preparation cost of V3.5+ electrolyte.

Enhanced power generation by carbonized microsphere embedded with bimetallic carbides nanoparticles as efficient electrocatalyst in bioenergy harvesting systems

The performance and preparation method of anode are the key factors for power generation and magnified application of microbial fuel cell (MFC). This is because the anode plays an essential role in whole process for extracellular electron transfer (EET) as the carrier of exoelectrogens. In this work, dual-phased Mo2C-W2C microsphere are prepared on carbon-based matrices as binder-free anode by in-situ pyrolysis of Mo/W precursors. As expected, the Mo2C-W2C/CC anode exhibits brilliant electrocatalytic activity, electron harvesting capacity and improved EET rate, thus the maximum power density of corresponding MFC achieves 4.89 W/m2. The above enhancement can be attributed to the microspherical three-dimensional structure consisting of numerous carbon nanosheets embedded with Mo2C-W2C heterogeneous nanoparticles, which will provide more catalytic active sites for microbial metabolic reactions. The microbial community analysis indicates that the formation of electroactive biofilms has been promoted by the selective screening of Mo2C-W2C for exoelectrogens and other bacteria related to sulfur metabolism. Finally, the bioenergy harvesting system assembled with Mo2C-W2C electrocatalyst successfully charges the 12 V battery. This study provides a facile, low-cost modification method for the development of high-performance MFC anodic materials conducive to large-scale preparation and has a promising effect in practical application.

In Situ Reconstructing NiFe Oxalate Toward Overall Water Splitting.

Surface reconstruction plays an essential role in electrochemical catalysis. The structures, compositions, and functionalities of the real catalytic species and sites generated by reconstruction, however, are yet to be clearly understood, for the metastable or transit state of most reconstructed structures. Herein, a series of NiFe oxalates (NixFe1- xC2O4, x = 1, 0.9, 0.7, 0.6, 0.5, and 0) are synthesized for overall water splitting electrocatalysis. Whilst NixFe1-xC2O4 shows great hydrogen evolution reaction (HER) activity, the in situ reconstructed NixFe1-xOOH exhibits outstanding oxygen evolution reaction (OER) activity. As identified by the in situ Raman spectroscopy and quasi-in situ X-ray absorption spectroscopy (XAS) techniques, reconstructions from NixFe1-xC2O4 into defective NixFe1-xOOH and finally amorphous NixFe1-xOOH active species (R-NixFe1-xOOH) are confirmed upon cyclic voltammetry processes. Specifically, the fully reconstructed R-Ni0.6Fe0.4OOH demonstrates the best OER activity (179mV to reach 10mA cm-2), originating from its abundant real active sites and optimal d-band center. Benefiting from the reconstruction, an alkaline electrolyzer composed of a Ni0.6Fe0.4C2O4 cathode and an in situ reconstructed R-Ni0.6Fe0.4OOH anode achieves a superb overall water splitting performance (1.52 V@10mA cm-2). This work provides an in-depth structure-property relationship understanding on the reconstruction of catalysts and offers a new pathway to designing novel catalyst.

Balanced adsorption and oxidation in a porous P, N-doped carbon prepared by melt-salt-mediated strategy for enhanced fenton-like reaction

The activation of persulfate oxidation processes using carbon-based catalysts is attractive for eliminating persistent aromatic organic pollutants in wastewater treatment. Herein, N and P co-doped carbonaceous (NPC) catalysts with an ultrahigh surface area were synthesized using a melt-salt-mediated strategy, employing Zeolitic Imidazolate Framework-8 as a self-sacrificing template. The NPC(1:1) carbon, prepared under optimized conditions, exhibited the highest surface area of 2001.5 m2/g, characterized by the highest number of defects and a high dispersion of N (1.89 %) and P (0.30 %) atoms on the carbon. This carbon catalyst exhibited a high capacity for adsorption and potential for activating persulfates in the removal of p-Nitrophenol (p-NP). Experimental data indicate a balance between adsorption and oxidation in the NPC(1:1)/PDS/p-NP system, with the highest catalytic removal rate achieved through moderate pre-adsorption of p-NP. Evidence from quenching, electron paramagnetic resonance (EPR), and amperometric i-t experiments suggests that the NPC(1:1)/PDS system primarily degrades p-NP through an electron transfer pathway. Defects in carbon and graphitic N were identified as catalytic sites. These defects resulted in an electron-deficient state, which leads to the activation of PDS and graphitic N was more reactive than both pyridinic and pyrrolic N in the adsorption of PDS molecules. Additionally, P-containing groups such as C-P-O, C-O-P, and C3-P were pinpointed as active sites on the carbons through DFT calculations. The intermediates during p-NP degradation were identified, and possible degradation pathways were proposed. A toxicity analysis indicated a significant reduction in overall toxicity following the oxidation treatment. This study provides innovative insights into the balance between adsorption and catalytic activity in porous carbon-activated persulfate oxidation reactions, thereby aiding in the development of enhanced oxidation catalysts for environmental remediation.

Bifunctional Mott-Schottky-type Co-Fe3N electrocatalyst as sulfur host and separator modifier to enhance the transformation kinetics of Li2S

Recently, lithium-sulfur batteries (LSBs) with ultra-high theoretical energy density attract the attention of researchers. However, the shuttle of lithium polysulfides (LPSs) seriously restrict the development of LSBs. Here, Co-Fe3N with Mott-Schottky type exhibits exceptional chemisorption and catalytic capabilities towards LPSs. The Co-Fe3N Mott-Schottky heterojunction induces charge redistribution at the heterogeneous interface, thereby increasing the rate of charge transfer, enhancing chemisorption ability, and reducing the energy barrier for S8 reduction and Li2S oxidation. The Co metal provides more catalytic and adsorption active sites for the conversion of LPSs and further improves the catalytic activity of Fe3N. Under the synergistic effect of the metal Co and Fe3N, the redox reaction of LPSs is improved, and the nucleation/decomposition energy barriers of Li2S are decreased, realizing the multifunctional coupling of adsorption-catalytic-conversion of LPSs. The LSBs with Co-Fe3N/S cathode and Co-Fe3N-PP separator exhibits a low capacity decay of 0.067 % per cycle at 1 C during 400 cycles. Even at a high sulfur loading of 3.1 mg cm−2, the LSBs delivers a reversible capacity of 1016 mA h g−1 at 0.1 C. The utilization of the Co-Fe3N with Mott-Schottky type in LSBs presents a novel approach towards designing multifunctional coupled materials with adsorption-catalysis-conversion capabilities.

Degradation of Natural Undaria pinnatifida into Unsaturated Guluronic Acid Oligosaccharides by a Single Alginate Lyase.

Here, we report on a bifunctional alginate lyase (Vnalg7) expressed in Pichia pastoris, which can degrade natural Undaria pinnatifida into unsaturated guluronic acid di- and trisaccharide without pretreatment. The enzyme activity of Vnalg7 (3620.00 U/mL-culture) was 15.81-fold higher than that of the original alg (228.90 U/mL-culture), following engineering modification. The degradation rate reached 52.75%, and reducing sugar reached 30.30 mg/mL after combining Vnalg7 (200.00 U/mL-culture) and 14% (w/v) U. pinnatifida for 6 h. Analysis of the action mode indicated that Vnalg7 could degrade many substrates to produce a variety of unsaturated alginate oligosaccharides (AOSs), and the minimal substrate was tetrasaccharide. Site-directed mutagenesis showed that Glu238, Glu241, Glu312, Arg236, His307, Lys414, and Tyr418 are essential catalytic sites, while Glu334, Glu344, and Asp311 play auxiliary roles. Mechanism analysis revealed the enzymatic degradation pattern of Vnalg7, which mainly recognizes and attacks the third glycosidic linkage from the reducing end of oligosaccharide substrate. Our findings provide a novel alginate lyase tool and a sustainable and commercial production strategy for value-added biomolecules using seaweeds.

Functional Characterization of Chlorophyll b Reductase NON-YELLOW COLORING 1 in Medicago truncatula

Chlorophyll degradation is a characteristic process of leaf senescence. Two mutant lines, which showed green leaves and seeds during senescence, were identified by screening a Tnt-1 retrotransposon-tagged population of Medicago truncatula. Genetic and molecular analyses indicated that the mutated gene is NON-YELLOW COLORING 1 (MtNYC1) in M. truncatula. MtNYC1 encoded a chlorophyll b reductase, characterized by three transmembrane domains and a catalytic site (Y***K). Our investigation further identified three splicing variants of MtNYC1, encoding a full-length protein (MtNYC1A) and two truncated proteins (MtNYC1B, MtNYC1C). Genetic evidence indicated that the catalytic site and the third transmembrane domain were critical domains for chlorophyll b reductase. The coordinated action of three splicing variants plays a pivotal role in the degradation of chlorophyll during the senescence of leaves. This discovery provides precise target sites for the development of stay-green legume cultivars.

Electronic synergy between NiCo2O4 and adjacent carbon defects to enhance styrene cracking activity for styrene-saturated activated carbon regeneration

The design and construction of catalysts featuring abundant electron transfer and defect structures for the regeneration of styrene-saturated activated carbon (AC) pose a significant challenge. This paper presents successful preparation of a regenerated adsorbent with synergistic catalytic active sites of NiCo2O4 spinel and carbon defects using a simple impregnation method. Enhanced catalytic activity is attributed to the electronic synergy between NiCo2O4 and carbon defects in 2.5Ni-2.5Co-900, involving substantial electron transfers, abundant acidic sites, and strong reducibility. Reactive oxygen species and the robust oxygen transfer facilitate the deep oxidation of intermediates and carbon elimination. The optimized regenerated adsorbent achieved a styrene adsorption capacity of 446.4mg/g with a recovery of 92.4% of the fresh sample, which is 1.5 times higher than 5Ni-900 and about 1.8 times higher than the unmodified regenerated activated carbon sample, RAC-900. The mechanism of styrene cracking and the evolution of intermediates were investigated using thermogravimetric-infrared coupling, and the effects of catalytic temperature and active sites on styrene cracking, deep oxidation of intermediates, and elimination of carbon deposits were explored. Kinetic analysis demonstrated that the adsorption of styrene on regenerated samples entailed a multifaceted process integrating both physical and chemical adsorption. The significance of chemical adsorption became increasingly evident as the concentration of defective sites grew. Intra-pore diffusion is the main determining step of the adsorption process. After five cycles, the adsorption capacity of 2.5Ni-2.5Co-900 decreased to below 25%, suggesting promising strategies to overcome challenges of regenerating styrene-saturated AC.

Fast tailoring the ZIF-8 surface microenvironment at ambient temperature to boost glucose oxidase-like activity of AuNPs for biosensing

Rational design and tailoring of the surface microenvironment surrounding the catalytic sites, such as noble metal nanoparticles, is an effective way to enhance the catalytic activity of mimicking enzymes. However, it remains on-going challenges to regulate the microenvironment of the catalytic sites due to the lack of tunable variability in structural precision of conventional solid catalysts. Herein, three types of zeolitic imidazolate framework-8 (ZIF-8) with different major crystal facet orientations, i.e., cubic with (100) facets (denoted ZIF-8c), truncated dodecahedral with (100), (110) facets (denoted ZIF-8tr), and dodecahedral with (110) facets (denoted ZIF-8r), were developed facilely using an electrochemical method by switching the potential at ambient temperature. Because the Zn2+ nodes were predominantly exposed on the (100) facets of ZIF-8, while the ligands were mainly exposed on the (110) facets. Hence, gold nanoparticles (AuNPs) showed differential glucose oxidase (GOx)-like activities when anchored in situ on different crystal facets of ZIF-8 and obeyed the following order ZIF-8c/Au>ZIF-8tr/Au>ZIF-8r/Au. Notably, both the metal nodes and aromatic linkers of ZIF-8 interacted with AuNPs through coordination and π-π interactions. The Zn2+ nodes facilitated the formation of the electron-deficient Au species. The electron transfer from AuNPs to Zn2+ sites effectively boosted the catalytic activity. It was known that directly tailoring the microenvironment at the supporting sites of noble metal catalysts to boost catalysis through a facile electrochemical method was not reported. Based on the favorable GOx-like activity and long-term stability of ZIF-8tr/Au, a highly sensitive electrochemical biosensing platform for assaying squamous cell carcinoma antigen (SCCA) was developed. It enabled fg-level detection of cancer marker.

Turning Waste into Treasure: Utilizing Environment-Pollutant Graphite Tailings as Photocatalyst for Photocatalytic Building Materials

Graphite tailings, as solid waste residuals from graphite extraction and refinement, pose serious risks to the surrounding ecological environment and the safety of residents’ lives. However, it is desirable but challenging how to rationalize the utilization of graphite tailings and further to develop their functionality. Herein, we demonstrate a "turning waste into treasure" strategy: capitalizing on the characteristics of graphite tailings in visible light absorption and rich metal catalytic sites, graphite tailings are employed as photocatalysts and fine aggregates to manufacture photocatalytic building materials, achieving sustainable use. Tailings powder from Luobei, Heilongjiang Province is selected as the photocatalyst, we discover that it exhibits photocatalytic degradation capability for methylene blue (MB) in water under visible-light irradiation: the degradation rates reach 70% within one hour and near-complete degradation within two hours, accompanying good recyclability. Structural analysis reveals that the graphite tailings are enriched with Fe2O3 and TiO2. They are capable of forming type-II heterojunction that enable efficient charge separation and transfer processes, transmitting photogenerated electrons to the active catalytic site to accomplish the photocatalytic degradation of MB. Moreover, other tailings, such as those from Jixi, also achieve photocatalytic degradation of MB, and cement specimens made with graphite tailings also bespoke photocatalytic degradation performance. This work is to provide solutions for the reuse of graphite tailings in the field of functional building materials, and to explore the feasibility of transforming graphite tailings from industrial solid waste to photocatalytic building materials.

Naphthyl-functionalized acetamide derivatives: Promising agents for cholinesterase inhibition and antioxidant therapy in Alzheimer’s disease

This study presents the synthesis and characterization of a series of 13 novel acetamides. These were subjected to Ellman’s assay to determine the efficacy of the AChE and BChE inhibitors. Finally, we report their antioxidant activity as an alternative approach for the search for drugs to treat AD. These studies revealed that compounds 1a–1k and 2l–2m were obtained in moderate yield. Four amides (1h, 1j, 1k, and 2l) were selective for one of the enzymes (BChE); thus, those that inhibited BChE were more active than the positive control (galantamine) and showed better IC50 values (3.30–5.03 µM). The theoretical free binding energies calculated by MM-GBSA indicated that all inhibitors were more stable than rivastigmine, and the inhibition mechanisms involved the entire active site: peripheral anionic site, oxyanion hole, acyl-binding pockets, and catalytic site. We examined the cytotoxicity of compounds 1h, 1j, 1k, and 2l in human dermal cells and found that they did not exhibit any toxic effects under the tested conditions. Additionally, these compounds, which also inhibited BChE, displayed mixed inhibition and did not exhibit hemolytic effects on human erythrocytes. Furthermore, the ABTS and DPPH assays indicated that, although none of the compounds showed activity in the DPPH assay, the EC50 values for radical trapping by the ABTS method showed that compounds 1a, 1d, 1e, and 1g had EC50 values lower than 10 µg/mL, indicating their strong radical scavenging capacity. We also report the crystal structures of compounds 1c, 1d, 1f, and 1g, which are found in monoclinic crystal systems.