Catalytic Nanostructures Research Articles

Fabricating NiCoFe2O4 decorated PANI nanostructures for high-performance electrochemical detection of 3-Nitro-L-tyrosine biomarkers for rapid diagnosis

A recent development in novel catalytic nanostructures offers numerous opportunities to perform the electrochemical operations towards sensing applications. The organic material PANI has been endorsed as a conducting polymer as it has controlled electrical properties and low density which will be beneficial over the metallic nanostructures. Herein, Nickel Cobalt Ferrite (NiCoFe2O4 (NCF)) nanostructures were anchored on the surface of PANI and engineered for electrochemical sensing applications. 3-nitro-L-tyrosine (3-NT) is an important compound for diagnosing oxidizing biomarkers that plays a vital role in therapy and diagnosing pathogenesis. Due to NCF/PANI’s conductivity, and superior surface area. It was probed for electrochemical sensing of 3-NT. The NCF/PANI displayed an excellent LOD, broad linear range, better sensitivity, selectivity, and stability. Furthermore, the proposed sensor exhibits sensitive 3-NT detection in biological samples with satisfactory recovery rates.

Temporal (Dis)Assembly of Peptide Nanostructures Dictated by Native Multistep Catalytic Transformations.

Emergence of complex catalytic machinery via simple building blocks under non-equilibrium conditions can contribute toward the system level understanding of the extant biocatalytic reaction network that fuels metabolism. Herein, we report temporal (dis)assembly of peptide nanostructures in presence of a cofactor dictated by native multistep cascade transformations. The short peptide can form a dynamic covalent bond with the thermodynamically activated substrate and recruit cofactor hemin to access non-equilibrium catalytic nanostructures (positive feedback). The neighboring imidazole and hemin moieties in the assembled state rapidly converted the substrate to product(s) via a two-step cascade reaction (hydrolase-peroxidase like) that subsequently triggered the disassembly of the catalytic nanostructures (negative feedback). The feedback coupled reaction cycle involving intrinsic catalytic prowess of short peptides to realize the advanced trait of two-stage cascade degradation of a thermodynamically activated substrate foreshadows the complex non-equilibrium protometabolic networks that might have preceded the chemical emergence of life.

Novel Nanostructured Pd/Co-Alumina Materials for the Catalytic Oxidation of Atmospheric Pollutants.

Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the synthesis of core-shell catalytic nanostructures to secure the chemical/thermal stability of active sites on the catalyst carrier. The catalysts were further promoted with a low Pd content (0.5 wt.%) incorporated via either incipient wetness impregnation (DI) or spray impregnation. The results revealed the superior performance of the spray-impregnated catalysts (Co/γ-Al2O3-SI) for both reactions. The deposition of Co oxide on the outer surface of the alumina particle (SEM images) and the availability of the active Co phase resulted in the enhancement of the Co/γ-Al2O3 catalysts' oxidation activity. Pd incorporation increased the catalysts' reducibility (TPR-H2) and improved the catalysts' performance for both reactions. However, the Pd incorporation method affected the catalytic performance; with the SI method, the active phase of Co3O4 was probably covered with PdO and was not available for the oxidation reactions. On the contrary, the incorporation of Pd with the DI method resulted in a better dispersion of PdO all over the Co/Al catalyst surface, maintaining available Co active sites and a better Pd-Co interaction. MeOH desorption studies revealed the methanol oxidation mechanism: the Co/Al catalysts promoted the partial oxidation of MeOH to formaldehyde (HCHO) and dehydration to dimethyl ether (DME), while the Pd-based Co/Al catalysts enhanced the complete oxidation of methanol to CO2 and H2O.

N-Heterocyclic carbene-functionalized metal nanoparticles and nanoclusters for nanocatalysis.

N-Heterocyclic carbenes (NHCs) have recently emerged as a popular ligand for the functionalization of metal nanoparticles and atomically precise metal clusters. The strong electron-donating properties of NHCs and robust NHC-metal covalent bonding endow metal nanostructures with improved stability and enhanced catalytic performances. In this review, we focus on NHC-coordinated metal nanoparticles and nanoclusters for the electrochemical CO2 reduction reaction (eCO2RR), selective hydrogenation of unsaturated compounds, and asymmetrical catalytic reactions. We discuss the underlying factors that may be at play in determining the improved activity of NHC-functionalized metals and address a few promising perspectives of NHC functionalization for new and better catalytic metal nanostructures.

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH.

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

Design of platinum nanoflower catalyst exhibiting near-ideal local coordination in a complex shape

Here, we investigate the oxygen reduction reaction activity of near-monocrystalline platinum nanoflowers presenting a low microstrain to decorrelate the contribution of (i) distorted lattice and (ii) high coordination active sites found within the platinum nanoflower pores to the specific activity enhancement. The results are discussed within the framework of previous investigations onto various catalytic nanostructures. We evidenced that the microstrain of the platinum nanoflowers stands out of the trends previously established for defective platinum-based nanostructures, where the activity is driven by lattice distortion. This indicates that (i) ‘defective’ structures with low lattice distortion, but high variation in coordination number, can be synthesized and (ii) that their specific activity improvement is comparable to the surface distortion approach in liquid electrolyte.

Structural Expansion of Catalytic RNA Nanostructures through Oligomerization of a Cyclic Trimer of Engineered Ribozymes.

The multimolecular assembly of three-dimensionally structured proteins forms their quaternary structures, some of which have high geometric symmetry. The size and complexity of protein quaternary structures often increase in a hierarchical manner, with simpler, smaller structures serving as units for larger quaternary structures. In this study, we exploited oligomerization of a ribozyme cyclic trimer to achieve larger ribozyme-based RNA assembly. By installing kissing loop (KL) interacting units to one-, two-, or three-unit RNA molecules in the ribozyme trimer, we constructed dimers, open-chain oligomers, and branched oligomers of ribozyme trimer units. One type of open-chain oligomer preferentially formed a closed tetramer containing 12 component RNAs to provide 12 ribozyme units. We also observed large assembly of ribozyme trimers, which reached 1000 nm in size.

Catalytic Nanomedicine as a Therapeutic Approach to Brain Tumors: Main Hypotheses for Mechanisms of Action.

Glioblastoma multiforme (GBM) is the most aggressive primary malignant tumor of the brain. Although there are currently a wide variety of therapeutic approaches focused on tumor elimination, such as radiotherapy, chemotherapy, and tumor field therapy, among others, the main approach involves surgery to remove the GBM. However, since tumor growth occurs in normal brain tissue, complete removal is impossible, and patients end up requiring additional treatments after surgery. In this line, Catalytic Nanomedicine has achieved important advances in developing bionanocatalysts, brain-tissue-biocompatible catalytic nanostructures capable of destabilizing the genetic material of malignant cells, causing their apoptosis. Previous work has demonstrated the efficacy of bionanocatalysts and their selectivity for cancer cells without affecting surrounding healthy tissue cells. The present review provides a detailed description of these nanoparticles and their potential mechanisms of action as antineoplastic agents, covering the most recent research and hypotheses from their incorporation into the tumor bed, internalization via endocytosis, specific chemotaxis by mitochondrial and nuclear genetic material, and activation of programmed cell death. In addition, a case report of a patient with GBM treated with the bionanocatalysts following tumor removal surgery is described. Finally, the gaps in knowledge that must be bridged before the clinical translation of these compounds with such a promising future are detailed.

Cuprous Oxide-Based Dual Catalytic Nanostructures for Tumor Vascular Normalization-Enhanced Chemodynamic Therapy

Cuprous Oxide-Based Dual Catalytic Nanostructures for Tumor Vascular Normalization-Enhanced Chemodynamic Therapy

Energy-efficient ultrafast microwave crystalline phase evolution for designing highly efficient oxygen evolution catalysts

Lowering the production cost while maintaining the superb activity of catalysts for sluggish oxygen evolution reaction (OER) is the utmost challenge towards the success of electrolytic hydrogen-based green economy. Here, we report a fast (seconds scale) and very low energy-consuming recrystallization strategy for the universal development of nickel–iron-based sulfide, selenide and phosphide nanostructures with the state-or-the-art OER activity. Amorphous irregular bulk morphology of the iron nitrate treated nickel foam rapidly recrystallizes into the uniform nanostructures of sulfide, selenide and phosphide phases by microwave ultrafast thermal treatment upon graphene substrate. As-developed nanosheets of iron-doped Ni3S2/NiS in-plane heterostructure shows exceptionally high OER activity, with an overpotential of only 187 mV at 10 mA cm−2. It also requires only 289 mV to achieve a very high current density of 500 mA cm−2, which is well below the well-recognized target value (<300 mV) for commercial use. Comprehensive analysis reveals that NiS phase of Ni3S2/NiS selectively transforms into an amorphous (oxy)hydroxide phase under OER condition along with the in-situ yield of iron-doped Ni3S2/NiOOH heterostructure with a high activity. This efficient recrystallization protocol into high performance catalytic nanostructures is not only interesting for generating diverse crystalline phases, but also highly important for the low-cost practical utilization.

XNAzymes targeting the SARS-CoV-2 genome inhibit viral infection

The unprecedented emergence and spread of SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic, underscores the need for diagnostic and therapeutic technologies that can be rapidly tailored to novel threats. Here, we show that site-specific RNA endonuclease XNAzymes – artificial catalysts composed of single-stranded synthetic xeno-nucleic acid oligonucleotides (in this case 2’-deoxy-2’-fluoro-β-D-arabino nucleic acid) – may be designed, synthesised and screened within days, enabling the discovery of a range of enzymes targeting SARS-CoV-2 ORF1ab, ORF7b, spike- and nucleocapsid-encoding RNA. Three of these are further engineered to self-assemble into a catalytic nanostructure with enhanced biostability. This XNA nanostructure is capable of cleaving genomic SARS-CoV-2 RNA under physiological conditions, and when transfected into cells inhibits infection with authentic SARS-CoV-2 virus by RNA knockdown. These results demonstrate the potential of XNAzymes to provide a platform for the rapid generation of antiviral reagents.

Nanomedicine in the Face of Parkinson's Disease: From Drug Delivery Systems to Nanozymes.

The complexity and overall burden of Parkinson's disease (PD) require new pharmacological approaches to counteract the symptomatology while reducing the progressive neurodegeneration of affected dopaminergic neurons. Since the pathophysiological signature of PD is characterized by the loss of physiological levels of dopamine (DA) and the misfolding and aggregation of the alpha-synuclein (α-syn) protein, new proposals seek to restore the lost DA and inhibit the progressive damage derived from pathological α-syn and its impact in terms of oxidative stress. In this line, nanomedicine (the medical application of nanotechnology) has achieved significant advances in the development of nanocarriers capable of transporting and delivering basal state DA in a controlled manner in the tissues of interest, as well as highly selective catalytic nanostructures with enzyme-like properties for the elimination of reactive oxygen species (responsible for oxidative stress) and the proteolysis of misfolded proteins. Although some of these proposals remain in their early stages, the deepening of our knowledge concerning the pathological processes of PD and the advances in nanomedicine could endow for the development of potential treatments for this still incurable condition. Therefore, in this paper, we offer: (i) a brief summary of the most recent findings concerning the physiology of motor regulation and (ii) the molecular neuropathological processes associated with PD, together with (iii) a recapitulation of the current progress in controlled DA release by nanocarriers and (iv) the design of nanozymes, catalytic nanostructures with oxidoreductase-, chaperon, and protease-like properties. Finally, we conclude by describing the prospects and knowledge gaps to overcome and consider as research into nanotherapies for PD continues, especially when clinical translations take place.

Catalysis-involved 3D N-doped graphene aerogel achieves a superior solar water purification rate and efficiency

Solar-driven water evaporation is a promising technology to address the water scarcity concern. While in the past years this research direction has initiated sizable progress in water purification, its application remains challenging due to the low water evaporation rate and treatment efficiency. Herein, a 3D cylinder evaporator (SMNG) with superior evaporation rate and excellent water treatment efficiency is developed through a unique 3D structural design by incorporating catalytic Ag-MnO2 nanostructure with N-doped graphene aerogel. The SMNG evaporator possesses an evaporation rate as high as 6.46 kg m−2 h−1 under one sun irradiation, with a photothermal conversion efficiency of 90.25 %. In addition, the SMNG also exhibits a remarkable desalination ability, with an evaporation rate of 6.15 kg m−2 h−1 and an ions rejection rate up to 99.9 % on seawater. In an outdoor environment, the SMNG can attain a maximum seawater evaporation rate of 8.57 kg m−2 h−1, demonstrating its promising practical applications. The SMNG evaporator also shows over 99.9 % efficiencies in purifying wastewater that contains organic dyes, heavy ions, formaldehyde, and E. coli.

Targeting non-coding RNA family members with artificial endonuclease XNAzymes

Non-coding RNAs (ncRNAs) offer a wealth of therapeutic targets for a range of diseases. However, secondary structures and high similarity within sequence families make specific knockdown challenging. Here, we engineer a series of artificial oligonucleotide enzymes (XNAzymes) composed of 2’-deoxy-2’-fluoro-β-D-arabino nucleic acid (FANA) that specifically or preferentially cleave individual ncRNA family members under quasi-physiological conditions, including members of the classic microRNA cluster miR-17~92 (oncomiR-1) and the Y RNA hY5. We demonstrate self-assembly of three anti-miR XNAzymes into a biostable catalytic XNA nanostructure, which targets the cancer-associated microRNAs miR-17, miR-20a and miR-21. Our results provide a starting point for the development of XNAzymes as a platform technology for precision knockdown of specific non-coding RNAs, with the potential to reduce off-target effects compared with other nucleic acid technologies.

Markov State Study of Electrostatic Channeling within the Tricarboxylic Acid Cycle Supercomplex.

The high efficiency of cascade reactions in supramolecular enzyme nanoassemblies, known as metabolons, has attracted substantial attention in various fields ranging from fundamental biochemistry and molecular biology to recent applications in biofuel cells, biosensors, and chemical synthesis. One reason for the high efficiency of metabolons is the structures formed by sequential enzymes that allow the direct transport of intermediates between consecutive active sites. The supercomplex of malate dehydrogenase (MDH) and citrate synthase (CS) is an ideal example of the controlled transport of intermediates via electrostatic channeling. Here, using a combination of molecular dynamics (MD) simulations and a Markov state model (MSM), we examined the transport process of the intermediate oxaloacetate (OAA) from MDH to CS. The MSM enables the identification of the dominant transport pathways of OAA from MDH to CS. Analysis of all pathways using a hub score approach reveals a small set of residues that control OAA transport. This set includes an arginine residue previously identified experimentally. MSM analysis of a mutated complex, where the identified arginine is replaced by alanine, led to a 2-fold decrease in transfer efficiency, also consistent with experimental results. This work provides a molecular-level understanding of the electrostatic channeling mechanism and will enable the further design of catalytic nanostructures utilizing electrostatic channeling.

Thermal annealing effects on palladium-decorated gold nanoparticle catalysts

Palladium metal supported on gold in the form of surface ensembles have enhanced catalytic properties compared to monometallic Pd, as exemplified by Pd-decorated Au nanoparticles (Pd-on-Au NPs) for various room-temperature reactions. Whereas the catalytic properties and nanostructure of Pd-on-Au NPs are not known at higher temperatures, this work focuses on thermal annealing effects on the Pd-on-Au NP nanostructure, bimetal distribution, and room-temperature water-phase trichloroethene hydrodechlorination (TCE HDC) as the model reaction. Analysis of the average coordination environment of Pd and Au atoms through x-ray absorption spectroscopy showed that as-synthesized Pd-on-Au NPs transitioned from a Au core/Pd shell structure to Au-rich core/PdAu surface alloy or PdAu mixed alloy structures depending on the Pd surface coverage (30–150 sc%) and annealing temperature (100–400 °C). The HDC activity strongly correlated with Pd ensemble size, where the as-formed Pd islands exhibited one order of magnitude enhanced activity compared to monometallic Pd. Higher annealing temperatures led to a surface/mixed alloy structure with smaller Pd ensemble size, resulting in lower activity but still ∼3 times more active than monometallic Pd. These results illustrate the importance of catalyst structure on activity and the usefulness of metal-decorated metal catalysts for higher-temperature reactions.

Optimizing Lattice Strain and Electron Effect of Ultrathin Platinum Nanoshells through Core–Shell Construction toward Superior Electrocatalytic Hydrogen Evolution

For optimizing the lattice strain and electron effect of Pt catalysts toward boosting their intrinsic electrocatalytic properties, we herein report the building of ultrathin Pt nanoshells in subnanoscale on the fine AgPd alloy cores, which are produced by alloying Pd atoms into the Ag nanoparticles through galvanic replacement reaction (GRR). Because of the smaller lattice expansion and modified electron effect of the ultrathin Pt shells in core–shell AgPd@Pt nanoparticles relative to those in core–shell Ag@Pt counterparts, the d-band center of core–shell AgPd@Pt nanoparticles locates at a lower position, favorable for weakening the adsorption of hydrogen and promoting their electrocatalysis for hydrogen evolution reaction (HER) in an acidic medium. Specifically, the core–shell AgPd@Pt nanoparticles with an appropriate Pt shell thickness not only show the lowest overpotential of 15.8 mV at 10 mA cm–2 in comparison with 27 mV of core–shell Ag@Pt nanoparticles, and 35 mV of commercial Pt/C catalyst, but also possesses the highest mass activity (1092.6 A g–1) at the overpotential of 25 mV, which is 1.58 times higher than that of core–shell Ag@Pt nanoparticles (693.5 A g–1) and 6.74 times higher than that of commercial Pt/C (162 A g–1). Moreover, alloying Pd into Ag cores also endows the ultrathin Pt shells with excellent electrocatalytic durability for HER. The concept of both lattice strain and electronic engineering through a core–shell construction may provide guidance for designing other highly catalytic and cost-effective nanostructures for a myriad of electrochemical reactions.

The modulation of DNA helical stability and geometry by the sequence and asymmetry of internal loops

Localized domains of unpaired nucleotides can arise in DNA and RNA through several pathways, including inherent sequence, processing errors, and protein interactions. For catalytic nucleic acids and DNA nanostructures, these domains have critical roles that include serving as functional sites and positioning helical domains; however, these unpaired domains can impart genomic instability as in the trinucleotide repeat disorders. Here, we present findings from experimental and computational work that address the role of DNA internal loop characteristics (sequence, size, and asymmetry) on the energetics and structural dynamics of loop-containing helical domains.

Polyphenylene sulfide as an efficient solid-phase ligand for improved selective alkyne hydrogenation

Liquid phase catalytic selective hydrogenation of alkynes to alkenes is a widely used reaction in the industry. Pairing nanocatalysts with soluble ligands or developing advanced catalytic nanostructures are two general protocols to realize preferable hydrogenation performance. However, both protocols are not cost-effective, and it is still challenging to achieve high selectivity and high activity with conventional hydrogenation nanocatalysts. In this work, commercial available, low-cost, and reactant-inert polyphenylene sulfide (PPS) is used as a new solid-phase ligand for palladium nanocatalysts in selective alkyne hydrogenation. Hydrogenation experiments have been carried out on different terminal and internal alkyne substrates, to investigate the universal effects of PPS on hydrogenation. As a result, over-hydrogenation and/or isomerization could be effectively suppressed upon the addition of solid PPS powders. The beneficial effects can be easily tuned by varying the PPS dosage. Importantly, both solid supported nanocatalysts and PPS can be simply separated via sedimentation and washing for subsequent experiments. A recycling experiment with PPS/Pd@CaCO3 has demonstrated the good cyclability (ten times of usage without much changes in effectiveness) of the catalyst system. X-ray photoelectron spectroscopy results indicate that the weak binding of PPS as a solid-phase ligand to nanocatalysts may contribute to the improved selective hydrogenation performance.

Enhancement of Activity of Copper Sites Toward Electroreduction of Carbon Dioxide through Hierarchical Deposition of Metal Oxide Cocatalysts

There has been growing interest in preparation of the advanced catalytic systems that efficiently utilize nanosized materials with well-defined composition, structure, thickness and desirable electrocatalytic properties. The ability of polynuclear inorganic metal oxo systems to support, stabilize and functionalize catalytic metal nanostructures is explored here. Certain nanostructured metal oxides, including oxides of zirconium and tungsten, have been demonstrated to influence catalytic metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu), thus affecting their chemisorptive and catalytic properties. Metal oxide (ZrO2, WO3) nanospecies can generate –OH groups at electrocatalytic interface. Our electrocatalytic results with copper nanostructures over-coated with ZrO2 or WO3 nanostructures imply the systems’ improved selectivity toward CO2-reduction relative to the competitive hydrogen evolution as well as the lower tendency of copper sites to undergo poisoning