Catalytic Generation Research Articles

Nickel metallaphotoredox-catalyzed C–O bond activation/Csp2–Csp3 coupling enabled by phosphine

A novel and general nickel/photoredox dual catalysis platform for benzyl alcohol C–O bond activation/Csp2–Csp3 cross coupling of benzothiazolyl bromide and free alcohol, enabled by the catalytic generation of an alkyl radical, is reported.

A ROS storm generating nanocomposite for enhanced chemodynamic therapy through H2O2 self-supply, GSH depletion and calcium overload.

Catalytic generation of toxic hydroxyl radicals (˙OH) from hydrogen peroxide (H2O2) is an effective strategy for tumor treatment in chemodynamic therapy (CDT). However, the intrinsic features of the microenvironment in solid tumors, characterized by limited H2O2 and overexpressed glutathione (GSH), severely impede the accumulation of intracellular ˙OH, posing significant challenges. To circumvent these critical issues, in this work, a CaO2-based multifunctional nanocomposite with a surface coating of Cu2+ and L-buthionine sulfoximine (BSO) (named CaO2@Cu-BSO) is designed for enhanced CDT. Taking advantage of the weakly acidic environment of the tumor, the nanocomposite gradually disintegrates, and the exposed CaO2 nanoparticles subsequently decompose to produce H2O2, alleviating the insufficient supply of endogenous H2O2 in the tumor microenvironment (TME). Furthermore, Cu2+ detached from the surface of CaO2 is reduced by H2O2 and GSH to Cu+ and ROS. Then, Cu+ catalyzes H2O2 to generate highly cytotoxic ˙OH and Cu2+, forming a cyclic catalysis effect for effective CDT. Meanwhile, GSH is depleted by Cu2+ ions to eliminate possible ˙OH scavenging. In addition, the decomposition of CaO2 by TME releases a large amount of free Ca2+, resulting in the accumulation and overload of Ca2+ and mitochondrial damage in tumor cells, further improving CDT efficacy and accelerating tumor apoptosis. Besides, BSO, a molecular inhibitor, decreases GSH production by blocking γ-glutamyl cysteine synthetase. Together, this strategy allows for enhanced CDT efficiency via a ROS storm generation strategy in tumor therapy. The experimental results confirm and demonstrate the satisfactory tumor inhibition effect both in vitro and in vivo.

Micromotor-based electrochemical immunoassays for reliable determination of amyloid-β (1–42) in Alzheimer's diagnosed clinical samples.

Alzheimer's disease (AD), in addition to being the most common cause of dementia, is very difficult to diagnose, with the 42-amino acid form of Aβ (Aβ-42) being one of the main biomarkers used for this purpose. Despite the enormous efforts made in recent years, the technologies available to determine Aβ-42 in human samples require sophisticated instrumentation, present high complexity, are sample and time-consuming, and are costly, highlighting the urgent need not only to develop new tools to overcome these limitations but to provide an early detection and treatment window for AD, which is a top-challenge. In recent years, micromotor (MM) technology has proven to add a new dimension to clinical biosensing, enabling ultrasensitive detections in short times and microscale environments.To this end, here an electrochemical immunoassay based on polypyrrole (PPy)/nickel (Ni)/platinum nanoparticles (PtNPs) MM is proposed in a pioneering manner for the determination of Aβ-42 in left prefrontal cortex brain tissue, cerebrospinal fluid, and plasma samples from patients with AD. MM combines the high binding capacity of their immunorecognition external layer with self-propulsion through the catalytic generation of oxygen bubbles in the internal layer due to decomposition of hydrogen peroxide as fuel, allowing rapid bio-detection (15 min) of Aβ-42 with excellent selectivity and sensitivity (LOD = 0.06 ng/mL). The application of this disruptive technology to the analysis of just 25 μL of the three types of clinical samples provides values concordant with the clinical values reported, thus confirming the potential of the MM approach to assist in the reliable, simple, fast, and affordable diagnosis of AD by determining Aβ-42.

Unraveling the Slurry/Substrate Interfacial Reaction Mechanism for Wide Band Gap (WBG) Chemical Mechanical Planarization (CMP)

Wide band gap (WBG) semiconductors have become of great interest to extend Moore’s Law beyond the limitations of current Si IC technology. More specifically, WBG materials (i.e., Silicon Carbide and Gallium Nitride) have been shown to increase performance due to their intrinsic properties (i.e., high capacitance, thermal stability, and wear resistance) associated with these materials. Current CMP processing of these WBG materials utilizes aggressive chemical conditions (i.e., abrasive nanoparticles and harsh oxidizers) and increasing shear forces to obtain the desired material removal rates (MRR) and surface planarity. Unfortunately, these processing conditions can cause defectivity (i.e., organic residue, pad debris, scratches, etc.) during the polishing process, leading to increasingly complex post-CMP cleaning steps. This work focuses on the strategic design of chemically activated, peroxide-based CMP slurries for emergent materials that target redox activation at the slurry-substrate surface interface to achieve improved CMP performance (i.e., enhanced material removal rates, superior surface quality, and low defects). More specifically, the catalytic generation of reactive oxygen species (ROS) (i.e., hydroxyl radical (*OH) and singlet oxygen (1O2)) at the substrate interface via surface complexation during the polishing process is exploited. The generated ROS can weaken the Si-C bonds within the surface of the substrate, allowing the particles to remove the surface more readily. This work explored organometallic complexes and non-metal catalysts, such as boron-based additives, as surface-active redox modulators. Initial results show that lower-stability complexes result in equally low MRR ranges below 400 nm/hr, while highly stable complexes increase the MRR as high as 1600 nm/hr. This complex stability/MRR trend has been further correlated to changes in the electron-poor areas of the complexes and ROS generation via radical trapping. The surface roughness analysis has shown improved surface quality between 0.8-1.0 nm across the substrate; however, organic residues from the complexes remain. Transitioning to non-metal boron electrophiles has shown similar MRR results (1000-1400 nm/hr) but can alleviate surface contamination. This implementation of Araca. Inc.’s patent-pending Flucto-CMP® technology employs megasonic energy to promote enhanced ROS generation, thus accelerating removal and significantly improving surface defectivity.

Hydrogen production on CoFe, CoFeMn and CoFeMo coatings deposited on Ni foam via electroless metal plating


 
 
 
 In this study, the catalytic hydrogen generation was evaluated on the cobalt–iron (CoFe), cobalt–iron–manganese (CoFeMn) and cobalt–ironmolybdenum (CoFeMo) coatings deposited on the Ni foam substrate using the electroless metal plating method and morpholine borane as the reducing agent. The characterisation of the surface morphology, structure and composition of resulted coatings was done using scanning electron microscopy (SEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The catalytic activity of the prepared CoFe/Ni, CoFeMn/Ni and CoFeMo/Ni catalysts was investigated for hydrogen generation from an alkaline sodium borohydride (NaBH4) solution at different temperatures. It was found that the hydrogen generation rate of ca. 5.2, 7.8 and 11.7 L min–1 g–1 was achieved by using the CoFe/ Ni, CoFeMo/Ni and CoFeMn/Ni coatings, respectively, at 343 K. Among the investigated catalysts, CoFeMn/Ni exhibits the lowest activation energy of 62.4 kJ mol–1 and the highest HGR of 11.7 L min–1 g–1 at 343 K.
 
 
 

3D printing Al porous metamaterials with triply periodic minimal surfaces (TPMS) for hydrogen generation from Al-water reaction

Porous metamaterials with three-dimensional periodic minimal surfaces provide new inspirations to develop catalytic hydrogen generation materials owing to their excellent mass transfer. Herein, ten kinds of Al porous metamaterials with triply periodic minimal surfaces (TPMS) were prepared by selective laser melting (SLM) for hydrogen generation from Al–H2O reaction. The structures of TPMS type Al materials significantly affect their hydrogen generation performance, and the increased reaction area and liquid flow rate of TPMS structure can effectively improve the galvanical replacement reaction and rapidly form a Ni/Al battery, thus accelerating the hydrogen generation. Compared to conventional aluminum powder, the obtained Diamond type Al porous metamaterial exhibit short induction period, high hydrogen generation yield (81.4 % after 2 h reaction) and high hydrogen generation rate (468 mL-H2·min−1·gAl−1), easy activation of surface passivation film, good structural stability and convenience to recycle the materials after use. This work highlights a simple, low-cost and optional porous structure design strategy that can be applied in the field of safe and efficient catalytic hydrogen generation.

Co-Pd alloy nanoparticles supported on activated carbon for High-efficiency production of vanillin from 4-methylguaiacol

Producing vanillin from lignin model compounds in an elegant and efficient manner is a focus of chemical utilization in lignocellulosic biomass. The facile synthesis of a cobalt-palladium bimetallic alloy anchored on activated carbon (Co-Pd/C), which excels in the selective oxidation of the lignin model compound 4-methylguaiacol to vanillin, is reported here. The characterization results of Co-Pd/C indicate that the catalysts enhance the catalytic efficiency by forming a cobalt-palladium alloy to modulate the number of d-band cavities and influence the O2 adsorption. Meanwhile, the synergistic effect between the alloys causes the Co-Pd/C catalyst exhibits good activity and stability in cycling experiments. A series of controlled experiments offer insight into the mechanism of catalytic generation of vanillin from 4-methylguaiacol. This work opens a new opportunity for achieving the valuable aromatic products from lignin.

Isopropylthiol emission by bloom-forming Microcystis: Biochemistry, ecophysiology and semiochemistry of a volatile organosulfur compound

Microcystis species not only produce toxic cyanobacterial blooms, but can be a significant source of taste and odour. Previous studies have associated foul-smelling volatile organic sulfur compounds (VOSCs) with Microcystis blooms, but have largely attributed these compounds to bacterial bloom decomposition. However, earlier reports of the production of isopropylthio compounds by several Microcystis strains suggests that these cyanobacteria may themselves be a source of these VOSCs. Sulphur compounds have been shown to play important semiochemical roles in algal cell protection and grazer interactions in marine systems, but little is known about the production and chemical ecology of freshwater cyanobacterial VOSCs. To address this knowledge gap, we undertook the first detailed investigation of the biochemistry, ecophysiology and semiochemistry of these compounds and their production by Microcystis, and tested the hypothesis that they act as multifunctional semiochemicals in processes related to cell protection and grazer defence. Using short-term incubations and an adapted headspace-GC–MS technique, we investigated VOSC production by axenic and non-axenic strains, and verified that isopropylthio compounds are in fact produced by these cyanobacteria, identifying 5 isopropyl moiety-containing VOSCs (isopropylthiol (ISH), isopropylmethyl sulfide, isopropyl methyl disulfide, diisopropyl disulfide (ISSI) and diisopropyl trisulfide) as well as methanethiol in three strains. Further studies with the axenic strain Microcystis PCC 7806 using different light regimes, metabolic inhibitors (sodium azide, DCMU), the antioxidant enzyme catalase and stable labelled precursors (hydrogencarbonate, acetates and sulfate) demonstrated that ISH is a true exo-metabolite, synthesized via the acetate pathway. It is actively produced and continuously excreted by the cyanobacteria during growth, with minimal internal storage or post-lysis catalytic generation. The molar ratios of the redox pair ISH/ISSI are not directly involved in the photosynthetic and respiratory electron transport chains, but dependant on the redox state of the cell - likely mediated by reactive oxygen species (ROS), as shown by a marked effect of catalase. These results, along with toxicological and behavioural assays using the two aquatic invertebrates Thamnocephalus platyurus and Daphnia magna indicate that ISH plays multiple important physiological and ecological roles. It acts as an effective antioxidant against high ROS levels, as often experienced in surface blooms, it elicits avoidance-related behavioural responses in grazer communities and at high levels, it can be toxic to some invertebrates.

Mixed Metal-Organic Framework Mixed-Matrix Membranes: Insights into Simultaneous Moisture-Triggered and Catalytic Delivery of Nitric Oxide using Cryo-scanning Electron Microscopy.

The fundamental chemical and structural diversity of metal-organic frameworks (MOFs) is vast, but there is a lack of industrial adoption of these extremely versatile compounds. To bridge the gap between basic research and industry, MOF powders must be formulated into more application-relevant shapes and/or composites. Successful incorporation of varying ratios of two different MOFs, CPO-27-Ni and CuBTTri, in a thin polymer film represents an important step toward the development of mixed MOF mixed-matrix membranes. To gain insight into the distribution of the two different MOFs in the polymer, we report their investigation by Cryo-scanning electron microscopy (Cryo-SEM) tomography, which minimizes surface charging and electron beam-induced damage. Because the MOFs are based on two different metal ions, Ni and Cu, the elemental maps of the MOF composite cross sections clearly identify the size and location of each MOF in the reconstructed 3D model. The tomography run was about six times faster than conventional focused ion beam (FIB)-SEM and the first insights to image segmentation combined with machine learning could be achieved. To verify that the MOF composites combined the benefits of rapid moisture-triggered release of nitric oxide (NO) from CPO-27-Ni with the continuous catalytic generation of NO from CuBTTri, we characterized their ability to deliver NO individually and simultaneously. These MOF composites show great promise to achieve optimal dual NO delivery in real-world medical applications.

Catalytic chemical vapor generation microplasma optical emission spectrometry for field detection of urea in dried blood spots

Despite widespread acceptance of dried blood spots (DBS) as a robust sampling strategy for clinical diagnosis, the analysis methods based on DBS frequently require tedious sample pretreatments, and bulky and expensive instruments, resulting in analyte loss, high reagent blank, long analysis time and limiting its field analysis. Herein, a method coupling catalytic chemical vapor generation (CVG) to miniature point discharge emission spectrometry (μPD-OES) was developed for the sensitive quantification of urea in DBS. In the presence of urease, the non-volatile urea contained in DBS could be catalytically converted to CO2 and NH3, which were separated from DBS and further swept into the μPD-OES for its quantitation via monitoring carbon atomic emission line at 193.0 nm. Compared to the conventional methods, the proposed catalytic CVG not only eliminates extraction, centrifugal separation, and other tedious pretreatments but also provides an efficient and high anti-interference sample introduction means for μPD-OES, allowing rapid, convenient, selective, and sensitive detection of blood urea. The proposed method provides a limit of detection (LOD) of 0.03 mM and a relative standard deviation (RSD) of 3.3% at 1 mM of urea with sampling 20 μL of blood. The accuracy and practicability of the catalytic CVG-μPD-OES were validated by successfully analyzing several finger blood samples. Owing to the advantages of the CVG and the μPD-OES, the proposed method also provides promising potentials for the field determination of other clinical targets spotted on DBS with small sample volume consumption and high sensitivity.

Gas station in blood vessels: An endothelium mimicking, self-sustainable nitric oxide fueling stent coating for prevention of thrombosis and restenosis

Stenting is the primary treatment for vascular obstruction-related cardiovascular diseases, but it inevitably causes endothelial injury which may lead to severe thrombosis and restenosis. Maintaining nitric oxide (NO, a vasoactive mediator) production and grafting endothelial glycocalyx such as heparin (Hep) onto the surface of cardiovascular stents could effectively reconstruct the damaged endothelium. However, insufficient endogenous NO donors may impede NO catalytic generation and fail to sustain cardiovascular homeostasis. Here, a dopamine-copper (DA-Cu) network-based coating armed with NO precursor L-arginine (Arg) and Hep (DA-Cu-Arg-Hep) is prepared using an organic solvent-free dipping technique to form a nanometer-thin coating onto the cardiovascular stents. The DA-Cu network adheres tightly to the surface of stents and confers excellent NO catalytic activity in the presence of endogenous NO donors. The immobilized Arg functions as a NO fuel to generate NO via endothelial nitric oxide synthase (eNOS), while Hep works as eNOS booster to increase the level of eNOS to decompose Arg into NO, ensuring a sufficient supply of NO even when endogenous donors are insufficient. The synergistic interaction between Cu and Arg is analogous to a gas station to fuel NO production to compensate for the insufficient endogenous NO donor in vivo. Consequently, it promotes the reconstruction of natural endothelium, inhibits smooth muscle cell (SMC) migration, and suppresses cascading platelet adhesion, preventing stent thrombosis and restenosis. We anticipate that our DA-Cu-Arg-Hep coating will improve the quality of life of cardiovascular patients through improved surgical follow-up, increased safety, and decreased medication, as well as revitalize the stenting industry through durable designs.

Tandem catalytic hydrogen gas generation and reduction of nitro aromatic derivatives via hydrolysis of ammonia borane over Ag NPs@ZIF-8 nanocomposites in aqueous media

In this research, three composites composed of ZIF-8 metal–organic framework and silver nanoparticles (Ag NPs) with different mole ratios were successfully synthesized. The fabricated Ag NPs@ZIF-8 composites were characterized by Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), energy-dispersive X-ray (EDX) mapping, field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques. The composite Ag NPs@ZIF-8 (1:1 mol ratio) was also characterized by Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS) analyses. Catalytic activity of the Ag NPs@ZIF-8 composites in tandem hydrogen generation from ammonia borane (H3N-BH3) and reduction of nitro-aromatic derivatives was investigated in one-pot reactions. The rate of evaluated H2 gas from the hydrolysis of H3N-BH3 by the Ag NPs@ZIF-8 (1:1) composite was measured to be about 198.9 (mL/g−1.min−1) in these catalytic reactions. Various derivatives of nitro compounds, including electron-withdrawing and electron-donating groups were converted to the corresponding amines with excellent yields by this catalytic system in less than one hour.

Engineered DNA-copper double-modified NIR carbon nanodots as oxidative stress amplifier for targeted intracellular production of reactive oxygen species

Regulating redox homeostasis is an advanced and efficient approach for cancer treatment. Well-designed catalytic drugs, which can catalytic generation of reactive oxygen species (ROS) in targeted cells, minimizing side effects, are urgently needed. Here, we developed a near infrared (NIR) carbon dot-based oxidative stress amplifier (named AptCND-Cu) for targeted cellular imaging and intracellular generation of ROS. AptCND-Cu was designed and prepared through a controllable double-covalent modification of NIR CNDs with a DNA aptamer and Cu complex. Detailed characterization techniques, including TEM, AFM, XPS and DLS, were used to confirm the successful coupling of both oligomer aptamer and metal complex. The resulting AptCND-Cu owns superior tumor targeting, stable NIR fluorescence (FL) emission, good photostability, and stable copper delivery. We demonstrate that this material can deplete glutathione (GSH) and can amplify Cu-induced Fenton-like reaction eventually causing cell death in vitro. AptCND-Cu exhibit also long tumor retention time in tumor-bearing mice and enhanced body clearance. This work not only propose an alternative strategy to the multifunctionalization of red-emissive CNDs, by simply integrating DNA and ion-based catalytic drugs, but also broadens their uses in cancer catalytic nanomedicine.

Bilayer vascular grafts with on-demand NO and H2S release capabilities

Nitric oxide (NO) and hydrogen sulfide (H2S) gasotransmitters exhibit potential therapeutic effects in the cardiovascular system. Herein, biomimicking multilayer structures of biological blood vessels, bilayer small-diameter vascular grafts (SDVGs) with on-demand NO and H2S release capabilities, were designed and fabricated. The keratin-based H2S donor (KTC) with good biocompatibility and high stability was first synthesized and then electrospun with poly (l-lactide-co-caprolactone) (PLCL) to be used as the outer layer of grafts. The electrospun poly (ε-caprolactone) (PCL) mats were aminolyzed and further chelated with copper (II) ions to construct glutathione peroxidase (GPx)-like structural surfaces for the catalytic generation of NO, which acted as the inner layer of grafts. The on-demand release of NO and H2S selectively and synergistically promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation and migration of human umbilical artery smooth muscle cells (HUASMCs). Dual releases of NO and H2S gasotransmitters could enhance their respective production, resulting in enhanced promotion of HUVECs and inhibition of HUASMCs owing to their combined actions. In addition, the bilayer grafts were conducive to forming endothelial cell layers under flow shear stress. In rat abdominal aorta replacement models, the grafts remained patency for 6 months. These grafts were capable of facilitating rapid endothelialization and alleviating neointimal hyperplasia without obvious injury, inflammation, or thrombosis. More importantly, the grafts were expected to avoid calcification with the degradation of the grafts. Taken together, these bilayer grafts will be greatly promising candidates for SDVGs with rapid endothelialization and anti-calcification properties.

Construction and demolition waste as a high-efficiency advanced process for organic pollutant degradation in Fenton-like reaction to approach circular economy

The Fenton-like reaction is a promising organic wastewater treatment reaction among advanced oxidation processes (AOP), which has emerged to replace the conventional Fenton reaction. Recycled construction and demolition waste (CDW), which is porous and rich in iron, manganese, and magnesium, can be reused as a Fenton-like catalyst. This study proposes an AOP wastewater treatment strategy using recycled porous CDW mixed with hydrogen peroxide (H2O2) to decompose methylene blue (MB) wastewater. According to the apparent first-order rate (Kapp) of 10 ppm MB adsorption, CDW-3, having the highest specific surface area, also has the highest Kapp of 0.23 min−1 g−1. The optimized conditions recommended by the Taguchi method include a 0.3 g mL−1 CDW-3 concentration, a 0.254 g mL−1 H2O2 concentration, and 10 ppm MB, resulting in an about 2.01 min−1Kapp value. In addition, MB concentration is observed as the most influential factor for Kapp, which decreases with increasing MB concentration and is about 0.62 min−1 at 1000 ppm MB. Repeating the Fenton-like reaction five times at 100 p.m. MB using the same CDW-3, the Kapp is about 0.64 min−1, which is 86% of the initial run. The synergistic effect index (ξ) is defined to quantify the level of interaction between CDW and H2O2, which produces free radicals during the Fenton-like process. The ξ of CDW-3 is about 2.16. Overall, it is demonstrated that CDW is a promising catalyst for Fenton-like reactions, and the synergistic effect index (ξ) can be used as a reference index to evaluate the catalytic generation of free radicals between the catalyst and H2O2.

Hydrogen catalytic performance of hybrid Fe3O4/FeS2/g-C3N4 nanocomposite structures

In this work, Fe3O4/FeS2/g-C3N4 nanocomposites were developed for catalytic hydrogen generation from sodium borohydride. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM) were used to analyze these nanocomposites. The XRD diffraction peaks of Fe3O4 and FeS2 cubic phase showed an average crystal size of calculation of 15 and 20 nm. ESEM micrographs showed a 2D broken up sheet structure having more edge sites. The BET surface areas for S@g-C3N4, 1.0, 2.0, and 3.0 wt% Fe3O4/FeS2 were 40, 109, 137 and 162 m2/g, respectively. Even though Fe3O4/FeS2 were incorporated into the nanosheet, the pore size was increased from 2.0 to 2.15 nm. S@g-C3N4 has an average band gap of 2.60 eV that decreased to 2.30, 2.21 and 2.18 eV at 1.0, 2.0 and 3.0 wt% of FeS2. In addition, Fe3O4/FeS2/g-C3N4 nanosheets showed an emission band at 460 nm. Moreover, the intensity of this band decreased as the content of Fe3O4/FeS2 reached 3.0 wt%. The rate of hydrogen production is accelerated as the percentage of Fe3O4/FeS2 increased from 1.0 to 3.0 wt%. The sample 3.0 wt% Fe3O4/FeS2 showed the best rate of hydrogen production (8480 mL/g·min).

Self‐Driven Electricity Modulates d‐Band Electrons of Copper Single‐Atom Nanozyme for Boosting Cancer Therapy

AbstractSingle‐atom nanozymes (SAzymes) are considered as the most promising candidates for natural enzymes due to their atomically dispersed active sites that closely resemble the metal active centers of their natural counterparts. However, a significant challenge still exists for improving their catalytic activities, retarding their practical applications. Herein, this article presents that through the application of a human self‐driven triboelectric device to impose electrical stimulus, the multiple enzyme‐like activities of a single‐atom copper nanozyme (Cu‐NC) are remarkably improved, thereby boosting cancer cell oxidative damage and death for realizing improved therapy. Under an electrical stimulus with 20 V voltage, the peroxidase, catalase, oxidase, and glutathione oxidase like activities of Cu‐NC are all improved to boost the catalytic generation of free radicals. Through calculation, this work analyzes how the electrical stimulus modulates the catalytic activity via decreasing adsorption energy of H2O2 on Cu active sites, increasing Cu dxy orbital near the Fermi level, and shifting the d‐band center of Cu, facilitating the catalytic reactions. This work opens new perspectives on improving single‐atom nanoenzymes for cancer therapy.

Amino Acid-Derived Ionic Chiral Catalysts Enable Desymmetrizing Cross-Coupling to Remote Acyclic Quaternary Stereocenters.

Synthetic application of asymmetric catalysis relies on strategic alignment of bond construction to creation of chirality of a target molecule. Remote desymmetrization offers distinctive advantages of spatial decoupling of catalytic transformation and generation of a stereogenic element. However, such spatial separation presents substantial difficulties for the chiral catalyst to discriminate distant enantiotopic sites through a reaction three or more bonds away from a prochirality center. Here, we report a strategy that establishes acyclic quaternary carbon stereocenters through cross-coupling reactions at distal positions of aryl substituents. The new class of amino acid-derived ionic chiral catalysts enables desymmetrizing (enantiotopic-group-selective) Suzuki-Miyaura reaction, Sonogashira reaction, and Buchwald-Hartwig amination between diverse diarylmethane scaffolds and aryl, alkynyl, and amino coupling partners, providing rapid access to enantioenriched molecules that project substituents to widely spaced positions in the three-dimensional space. Experimental and computational investigations reveal electrostatic steering of substrates by the C-terminus of chiral ligands through ionic interactions. Cooperative ion-dipole interactions between the catalyst's amide group and potassium cation aid in the preorganization that transmits asymmetry to the product. This study demonstrates that it is practical to achieve precise long-range stereocontrol through engineering the spatial arrangements of the ionic catalysts' substrate-recognizing groups and metal centers.

Rational construction of mushroom-like Ni@N-doped carbon tubes composites with enhanced electromagnetic wave absorption

It is confirmed that electromagnetic wave absorption (EMA) materials with a metal-carbon dual-phase structure has exposed great potential for achieving tunable, strong, and wide EMA. Herein, the mushroom-like Ni@N-doped carbon tubes (NNCTs) are prepared by nickel-catalyzed growth of carbon tubes, realizing carbon encapsulated metal particles. One end of the carbon tube grows and connects to form a bundle of mushroom-like structures, and the other end of the carbon tube is filled with nickel as the mushroom head. The structure control of NNCTs can be achieved by adjusting the amount of catalyst Ni. Appropriate amount of nickel can control the formation of mushroom-like structure. The results show that the structure has a great influence on the EMA performance. Particularly, NNCT-0.5 provides a minimum reflection loss of -60.47 dB with a thickness of 4.0 mm, and the widest effective absorption bandwidth for RL< -10 dB of NNCT-1.5 at a thickness of 2.00 mm was 7.53 GHz (10.47–18.00 GHz). The immobilization of carbon in melamine was achieved by catalytic generation of carbon tubes with metal ions Ni. Metal-carbon biphasic composites introduce dielectric and magnetic losses. The presence of multiple interfaces and voids in the mushroom structure allows tuning the dielectric parameters and optimizing the impedance matching. This work provides an effective strategy for the fabrication of dielectric and magnetic composites with special structures, which has great potential in attenuating electromagnetic wave energy.

Functional Study and Efficient Catalytic Element Mining of CYP76AHs in Salvia Plants.

Salvia is a large genus with hundreds of species used in traditional Chinese medicine. Tanshinones are a highly representative class of exclusive compounds found in the Salvia genus that exhibit significant biological activity. Tanshinone components have been identified in 16 Salvia species. The CYP76AH subfamily (P450) is crucial for the synthesis of tanshinone due to its catalytic generation of polyhydroxy structures. In this study, a total of 420 CYP76AH genes were obtained, and phylogenetic analysis showed their clear clustering relationships. Fifteen CYP76AH genes from 10 Salvia species were cloned and studied from the perspectives of evolution and catalytic efficiency. Three CYP76AHs with significantly improved catalytic efficiency compared to SmCYP76AH3 were identified, providing efficient catalytic elements for the synthetic biological production of tanshinones. A structure-function relationship study revealed several conserved residues that might be related to the function of CYP76AHs and provided a new mutation direction for the study of the directed evolution of plant P450.