Functionalization of Hollow Nanomaterials for Catalytic Applications: Nanoreactor Construction

Novel catalytic behavior of defective nanozymes with catalase-mimicking characteristics for the degradation of tetracycline

Although nanozymes have shown significant potential in wastewater treatment, enhancing their degradation performance remains challenging. Herein, a novel catalytic behavior was revealed for defective nanozymes with catalase-mimicking characteristics that efficiently degraded tetracycline (TC) in wastewater. Hydroxyl groups adsorbed on defect sites facilitated the in-situ formation of vacancies during catalysis, thereby replenishing active sites. Additionally, electron transfer considerably enhanced the catalytic reaction. Consequently, numerous reactive oxygen species (ROS) were generated through these processes and subsequent radical reactions. The defective nanozymes, with their unique catalytic behavior, proved effective for the catalytic degradation of TC. Experimental results demonstrate that •OH, •O2-, 1O2 and e- were the primary contributors to the degradation process. In real wastewater samples, the normalized degradation rate constant for defective nanozymes reached 26.0 min-1 g-1 L, exceeding those of other catalysts. This study reveals the new catalytic behavior of defective nanozymes and provides an effective advanced oxidation process for the degradation of organic pollutants.

Rationally designed hierarchical hollow CuS/CdIn2S4 heterostructure nanoboxes for boosted photoreduction of CO2

A novel double-shelled CuS/CdIn2S4 photocatalyst was rationally designed using CdIn2S4 sheets in situ grown upon the exterior of hollow CuS nanocubes. The unique hierarchical hollow structure of CuS/CdIn2S4 provides numerous active sites and reduces carrier diffusion length. Surface sulfur vacancies mitigate the detachment of the intermediate, which is favorable for a multi-electron reaction path such as that in the production of CH4. Meanwhile, a suitable band-structure alignment between p-type CuS and n-type CdIn2S4 leads to the formation of a type-II heterostructure, thus resulting in effective light-harvesting and spatial separation of electron-hole pairs for CO2 photoreduction. The CuS/CdIn2S4 heterostructure exhibits significantly enhanced performance with a boosted CO yield of 40.73 μmol g-1 h-1 as well as a noticeably improved CH4 selectivity (36.5%, 23.41 μmol g-1 h-1). This work introduces innovative concepts in designing photocatalytic systems with unique morphologies and rational band structures, promising advancements in CO2 photoreduction at reduced costs.

Built-In Electric Field Boost Photocatalytic Degradation of Pollutants in Wastewater

The photocatalysis technique shows significant potential for wastewater degradation; however, the rapid recombination of photogenerated holes and electrons severely limits its photocatalytic efficiency. This situation necessitates the development of effective strategies to tackle these challenges. One well-documented approach is built-in electric field engineering in heterojunctions or composites, which has been shown to enhance electron transfer and thereby reduce the recombination of electrons and holes. This strategy has proven highly effective in significantly improving photocatalytic activity for the degradation of pollutants in wastewater. In this context, we summarize recent advancements in built-in electric field engineering in photocatalysts, highlighting the fundamentals and modifications of this approach, as well as its positive impact on photocatalytic performance in the degradation of wastewater pollutants.

Direct and specific detection of methyl-paraoxon using a highly sensitive fluorescence strategy combined with phosphatase-like nanozyme and molecularly imprinted polymer

Methyl paraoxon (MP) is a highly toxic, efficient and broad-spectrum organophosphorus pesticide, which poses significant risks to ecological environment and human health. Many detection methods for MP are based on the enzyme catalytic or inhibition effect. But natural biological enzymes are relatively expensive and easy to be inactivated with a short service life. As a unique tool of nanotechnology with enzyme-like characteristics, nanozyme has attracted increasing concern. However, a large proportion of nanozymes lack the intrinsic specificity, becoming a main barrier of constraining their use in biochemical analysis. Here, we use a one-pot reverse microemulsion polymerization combine the gold nanoclusters (AuNCs) with molecularly imprinted polymers (MIPs), polydopamine (PDA) and hollow CeO2 nanospheres to synthesize the bright red-orange fluorescence probe (CeO2@PDA@AuNCs-MIPs) with high phosphatase-like activity for selective detection of MP. The hollow structure possesses a specific surface area and porous matrix, which not only increases the exposure of active sites but also enhances the efficiency of mass and electron transport. Consequently, this structure significantly enhances the catalytic activity by reducing transport distances. The introduced MIPs provide the specific recognition sites for MP. And Ce (III) can excite aggregation induced emission of AuNCs and enhance the fluorescent signal. The absolute fluorescence quantum yield (FLQY) of CeO2@PDA@AuNCs-MIPs (1.41 %) was 12.8-fold higher than that of the GSH-AuNCs (0.11 %). With the presence of MP, Ce (IV)/Ce (III) species serve as the active sites to polarize and hydrolyze phosphate bonds to generate p-nitrophenol (p-NP), which can quench the fluorescent signal through the inner-filter effect. The as-prepared CeO2@PDA@AuNCs-MIPs nanozyme-based fluorescence method for MP detection displayed superior analytical performances with wide linearities range of 0.45-125 nM and the detection limit of 0.15 nM. Furthermore, the designed method offers satisfactory practical application ability. The developed method is simple and effective for the in-field detection.

Pore engineering of Porous Materials: Effects and Applications

Porous materials, characterized by their controllable pore size, high specific surface area, and controlled space functionality, have become cross-scale structures with microenvironment effects and multiple functions and have gained tremendous attention in the fields of catalysis, energy storage, and biomedicine. They have evolved from initial nanopores to multiscale pore-cavity designs with yolk-shell, multishells, or asymmetric structures, such as bottle-shaped, multichambered, and branching architectures. Various synthesis strategies have been developed for the interfacial engineering of porous structures, including bottom-up approaches by using liquid-liquid or liquid-solid interfaces "templating" and top-down approaches toward chemical tailoring of polymers with different cross-linking degrees, as well as interface transformation using the Oswald ripening, Kirkendall effect, or atomic diffusion and rearrangement methods. These techniques permit the design of functional porous materials with diverse microenvironment effects, such as the pore size effect, pore enrichment effect, pore isolation and synergistic effect, and pore local field enhancement effect, for enhanced applications. In this review, we delve into the bottom-up and top-down interfacial-oriented synthesis approaches of porous structures with advanced structures and microenvironment effects. We also discuss the recent progress in the applications of these collaborative effects and structure-activity relationships in the areas of catalysis, energy storage, electrochemical conversion, and biomedicine. Finally, we outline the persisting obstacles and prospective avenues in terms of controlled synthesis and functionalization of porous engineering. The perspectives proposed in this paper may contribute to promote wider applications in various interdisciplinary fields within the confined dimensions of porous structures.

Design of hollow structured nanoreactors for liquid-phase hydrogenations

Inspired by the attractive structures and functions of natural matter (such as cells, organelles and enzymes), chemists are constantly exploring innovative material platforms to mimic natural catalytic systems, particularly liquid-phase hydrogenations, which are of great significance for chemical upgrading and synthesis. Hollow structured nanoreactors (HSNRs), featuring unique nanoarchitectures and advantageous properties, offer new opportunities for achieving excellent catalytic activity, selectivity, stability and sustainability. Notwithstanding the great progress made in HSNRs, there still remain the challenges of precise synthetic chemistry, and mesoscale catalytic kinetic investigation, and smart catalysis. To this extent, we provide an overview of recent developments in the synthetic chemistry of HSNRs, the unique characteristics of these materials and catalytic mechanisms in HSNRs. Finally, a brief outlook, challenges and further opportunities for their synthetic methodologies and catalytic application are discussed. This review might promote the creation of further HSNRs, realize the sustainable production of fine chemicals and pharmaceuticals, and contribute to the development of materials science.

Nanoengineering Multilength-Scale Porous Hierarchy in Mesoporous Metal-Organic Framework Single Crystals

Developing a reliable method for constructing mesoporous metal-organic frameworks (MOFs) with single-crystalline forms remains a challenging task despite numerous efforts. This study presents a solvent-mediated assembly method for fabricating zeolitic imidazolate framework (ZIF) single-crystal nanoparticles with a well-defined micro-mesoporous structure using polystyrene-block-poly(ethylene oxide) diblock copolymer micelles as a soft-template. The precise control of particle sizes, ranging from 85 to 1200 nm, is achieved by regulating nucleation and crystal growth rates while maintaining consistent pore diameters in mesoporous nanoparticles and a rhombohedral dodecahedron morphology. Furthermore, this study presents a robust platform for nanoarchitecturing to prepare hierarchically porous materials (e.g., core-shell and hollow structures), including microporous ZIF@mesoporous ZIF, hollow mesoporous ZIF, and mesoporous ZIF@mesoporous ZIF. Such a multimodal pore design, ranging from microporous to microporous/mesoporous and further micro-/meso-/macroporous, provides significant evidence for the future possibility of the structural design of MOFs.

Colloidal Templating in Catalyst Design for Thermocatalysis

Conventional catalyst preparative methods commonly entail the impregnation, precipitation, and/or immobilization of nanoparticles on their supports. While convenient, such methods do not readily afford the ability to control collective ensemble-like nanoparticle properties, such as nanoparticle proximity, placement, and compartmentalization. In this Perspective, we illustrate how incorporating colloidal templating into catalyst design for thermocatalysis confers synthetic advantages to facilitate new catalytic investigations and augment catalytic performance, focusing on three colloid-templated catalyst structures: 3D macroporous structures, hierarchical macro-mesoporous structures, and discrete hollow nanoreactors. We outline how colloidal templating decouples the nanoparticle and support formation steps to devise modular catalyst platforms that can be flexibly tuned at different length scales. Of particular interest is the raspberry colloid templating (RCT) method which confers high thermomechanical stability by partially embedding nanoparticles within its support, while retaining high levels of reactant accessibility. We illustrate how the high modularity of the RCT approach allows one to independently control collective nanoparticle properties, such as nanoparticle proximity and localization, without concomitant changes to other catalytic descriptors that would otherwise confound analyses of their catalytic performance. We next discuss how colloidal templating can be employed to achieve spatially disparate active site functionalization while directing reactant transport within the catalyst structure to enhance selectivity in multistep catalytic cascades. Throughout this Perspective, we highlight developments in advanced characterization that interrogate transport phenomena and/or derive new insights into these catalyst structures. Finally, we offer our outlook on the future roles, applications, and challenges of colloidal templating in catalyst design for thermocatalysis.

Hollow Nanoreactors Unlock New Possibilities for Persulfate-Based Advanced Oxidation Processes

As a novel type of catalytic material, hollow nanoreactors are expected to bring new development opportunities in the field of persulfate-based advanced oxidation processes due to their peculiar void-confinement, spatial compartmentation, and size-sieving effects. For such materials, however, further clarification on basic concepts and construction strategies, as well as a discussion of the inherent correlation between structure and catalytic activity are still required. In this context, this review aims to provide a state-of-the-art overview of hollow nanoreactors for activating persulfate. Initially, hollow nanoreactors are classified according to the constituent components of the shell structure and their dimensionality. Subsequently, the different construction strategies of hollow nanoreactors are described in detail, while common synthesis methods for these construction strategies are outlined. Furthermore, the most representative advantages of hollow nanoreactors are summarized, and their intrinsic connections to the nanoreactor structure are elucidated. Finally, the challenges and future prospects of hollow nanoreactors are presented.

Ultrasmall Inorganic Mesoporous Nanoparticles: Preparation, Functionalization, and Application

Ultrasmall mesoporous nanoparticles (<50 nm), a unique porous nanomaterial, have been widely studied in many fields in the last decade owing to the abundant advantages, involving rich mesopores, low density, high surface area, numerous reaction sites, large cavity space, ultrasmall size, etc. This paper presents a review of recent advances in the preparation, functionalization, and applications of ultrasmall inorganic mesoporous nanoparticles for the first time. The soft monomicelles-directed method, in contrast to the hard-template and template-free methods, is more flexible in the synthesis of mesoporous nanoparticles. This is because the amphiphilic micelle has tunable functional blocks, controlled molecule masses, configurations and mesostructures. Focus on the soft micelle directing method, monomicelles could be classified into four types, i.e., the Pluronic-type block copolymer monomicelles, laboratory-synthesized amphiphilic block copolymers monomicelles, the single-molecule star-shaped block copolymer monomicelles, and the small-molecule anionic/cationic surfactant monomicelles. This paper also reviews the functionalization of the inner mesopores and the outer surfaces, which includes constructing the yolkshell structures (encapsulated nanoparticles), anchoring the active components packed on the shell and building an asymmetric Janus architecture. Then, several representative applications, involving catalysis, energy storage, and biomedicines are presented. Finally, the prospects and challenges of controlled synthesis and large-scale applications of ultrasmall mesoporous nanoparticles in the future are foreseen.

Molecular Engineering and Morphology Control of Covalent Organic Frameworks for Enhancing Activity of Metal-Enzyme Cascade Catalysis

Metal-enzyme integrated catalysts (MEICs) that combine metal and enzyme offer great potential for sustainable chemoenzymatic cascade catalysis. However, rational design and construction of optimal microenvironments and accessible active sites for metal and enzyme in individual nanostructures are necessary but still challenging. Herein, Pd nanoparticles (NPs) and Candida antarctica lipase B (CALB) are co-immobilized into the pores and surfaces of covalent organic frameworks (COFs) with tunable functional groups, affording Pd/COF-X/CALB (X = ONa, OH, OMe) MEICs. This strategy can regulate the microenvironment around Pd NPs and CALB, and their interactions with substrates. As a result, the activity of the COF-based MEICs in catalyzing dynamic kinetic resolution of primary amines is enhanced and followed COF-OMe > COF-OH > COF-ONa. The experimental and simulation results demonstrated that functional groups of COFs modulated the conformation of CALB, the electronic states of Pd NPs, and the affinity of the integrated catalysts to the substrate, which contributed to the improvement of the catalytic activity of MEICs. Further, the MEICs are prepared using COF with hollow structure as support material, which increased accessible active sites and mass transfer efficiency, thus improving catalytic performance. This work provides a blueprint for rational design and preparation of highly active MEICs.

Hollow UiO-66-NH2 Encapsulated Pd Catalysts for Highly Selective Hydrogenation of Furfural to Furfuryl Alcohol

The selective hydrogenation of furfural (FFA) to furfuryl alcohol (FA) is regarded as attractive transformation to achieve the sustainable synthesis of value-added chemicals from biomass resources. However, the conventional supported catalysts are significantly restricted by their narrow pore size, ununiform dispersion and easy leaching or aggregation of catalytic sites. Herein, we designed hollow UiO-66-NH2 as the support to encapsulate Pd nanoparticles (Pd@H-UiO-66-NH2) to achieve the highly active and selective conversion of FFA to FA. Benefiting from the void-confinement effect and substrate enrichment of hollow structure, as well as the surface wrinkles, the as-prepared catalyst Pd@H-UiO-66-NH2 exhibited 96.8 % conversion of FFA with satisfactory selectivity reaching up to 92.4 % at 80 °C, 0.5 MPa H2 in isopropanol solvent within 6 h. More importantly, as-prepared Pd@H-UiO-66-NH2 catalyst exhibited excellent long-term stability, as well as good universality toward a series of hydrogenation of unsaturated hydrocarbons.

Spatially Confined Nanoreactors Designed for Biological Applications

The applications of nanoreactors in biology are becoming increasingly significant and prominent. Specifically, nanoreactors with spatially confined, due to their exquisite design that effectively limits the spatial range of biomolecules, attracted widespread attention. The main advantage of this structure is designed to improve reaction selectivity and efficiency by accumulating reactants and catalysts within the chambers, thus increasing the frequency of collisions between reactants. Herein, the recent progress in the synthesis of spatially confined nanoreactors and their biological applications is summarized, covering various kinds of nanoreactors, including porous inorganic materials, porous crystalline materials with organic components and self-assembled polymers to construct nanoreactors. These design principles underscore how precise reaction control could be achieved by adjusting the structure and composition of the nanoreactors to create spatial confined. Furthermore, various applications of spatially confined nanoreactors are demonstrated in the biological fields, such as biocatalysis, molecular detection, drug delivery, and cancer therapy. These applications showcase the potential prospects of spatially confined nanoreactors, offering robust guidance for future research and innovation.

An all-metallic nanovesicle for hydrogen oxidation

Vesicle, a microscopic unit that encloses a volume with an ultrathin wall, is ubiquitous in biomaterials. However, it remains a huge challenge to create its inorganic metal-based artificial counterparts. Here, inspired by the formation of biological vesicles, we proposed a novel biomimetic strategy of curling the ultrathin nanosheets into nanovesicles, which was driven by the interfacial strain. Trapped by the interfacial strain between the initially formed substrate Rh layer and subsequently formed RhRu overlayer, the nanosheet begins to deform in order to release a certain amount of strain. Density functional theory (DFT) calculations reveal that the Ru atoms make the curling of nanosheets more favorable in thermodynamics applications. Owing to the unique vesicular structure, the RhRu nanovesicles/C displays excellent hydrogen oxidation reaction (HOR) activity and stability, which has been proven by both experiments and DFT calculations. Specifically, the HOR mass activity of RhRu nanovesicles/C are 7.52 A mg(Rh+Ru)-1 at an overpotential of 50 mV at the rotating disk electrode (RDE) level; this is 24.19 times that of commercial Pt/C (0.31 mA mgPt-1). Moreover, the hydroxide exchange membrane fuel cell (HEMFC) with RhRu nanovesicles/C displays a peak power density of 1.62 W cm-2 in the H2-O2 condition, much better than that of commercial Pt/C (1.18 W cm-2). This work creates a new biomimetic strategy to synthesize inorganic nanomaterials, paving a pathway for designing catalytic reactors.

DNA-modified Prussian blue nanozymes for enhanced electrochemical biosensing

Prussian blue nanoparticles exhibit the potential to be employed in bioanalytical applications due to their robust stability, peroxidase-like catalytic functionality, straightforward synthesis, and biocompatibility. An efficient approach is presented for the synthesis of nucleic acid-modified Prussian blue nanoparticles (DNA-PBNPs), utilizing nanoparticle porosity to adsorb nucleic acids (polyT). This strategic adsorption leads to the exposure of nucleic acid sequences on the particle surface while retaining catalytic activity. DNA-PBNPs further couple with functional nucleic acid sequences and aptamers through complementary base pairing to act as transducers in biosensors and amplify signal acquisition. Subsequently, we integrated a copper ion-dependent DNAzyme (Cu2+-DNAzyme) and a vascular endothelial growth factor aptamer (VEGF aptamer) onto screen-printed electrodes to serve as recognition elements for analytes. Significantly, our approach leverages DNA-PBNPs as a superior alternative to traditional enzyme-linked antibodies in electrochemical biosensors, thereby enhancing both the efficiency and adaptability of these devices. Our study conclusively demonstrates the application of DNA-PBNPs in two different biosensing paradigms: the sensitive detection of copper ions and vascular endothelial growth factor (VEGF). These results indicate the promising potential of DNA-modified Prussian blue nanoparticles in advancing bioanalytical sensing technologies.

Nitrogen-oxygen co-doped carbon@silica hollow spheres as encapsulated Pd nanoreactors for acetylene dialkoxycarbonylation

The introduction of heteroatoms into hollow carbon spheres is imperative for enhancing catalytic activity. Consequently, we investigated the utilization of nitrogen-oxygen(N/O) co-doped hollow carbon (C)/silica (SiO2) nanospheres (NxC@mSiO2), which have a large internal volume and a nano-constrained environment that limits metal aggregation and loss, making them a potential candidate. In this study, we demonstrate the synthesis of nitrogen-oxygen (N/O) co-doped hollow carbon spheres using resorcinol and formaldehyde as carbon precursors, covered with silica, and encapsulated with palladium nanoparticles (NPs) in situ. The N/O co-doping process introduced defects on the surface of the internal C structure, which acted as active sites and facilitated substrate adsorption. Subsequent treatment with hydrogen peroxide (H2O2) introduced numerous carboxyl groups onto the C structure, increasing the catalytic environment as acid auxiliaries. The carboxyl group is present in the carbon structure, as determined calculations based on by density functional theory, reduces the adsorption energy of acetylene, thereby promoting its adsorption and enrichment. Furthermore, H2O2-treatment enhanced the oxygen defects in the carbon structure, improving the dispersion of Pd NPs and defect structure. The Pd/NxC@mSiO2-H2O2 catalysts demonstrated outstanding performance in the acetylene dialkoxycarbonylation reaction, showcasing high selectivity towards 1,4-dicarboxylate (>93 %) and remarkable acetylene conversion (>92 %). Notably, the catalyst exhibited exceptional selectivity and durability throughout the reaction.

Fe3O4 nanoparticles entrapped in the inner surfaces of N-doped carbon microtubes with enhanced biomimetic activity

Tubular structured composites have attracted great interest in catalysis research owing to their void-confinement effects. In this work, we synthesized a pair of hollow N-doped carbon microtubes (NCMTs) with Fe3O4 nanoparticles (NPs) encapsulated inside NCMTs (Fe3O4@NCMTs) and supported outside NCMTs (NCMTs@Fe3O4) while keeping other structural features the same. The impact of structural effects on the catalytic activities was investigated by comparing a pair of hollow-structured nanocomposites. It was found that the Fe3O4@NCMTs possessed a higher peroxidase-like activity when compared with NCMTs@Fe3O4, demonstrating structural superiority of Fe3O4@NCMTs. Based on the excellent peroxidase-like catalytic activity and stability of Fe3O4@NCMTs, an ultra-sensitive colorimetric method was developed for the detection of H2O2 and GSH with detection limits of 0.15 μM and 0.49 μM, respectively, which has potential application value in biological sciences and biotechnology.

Gallium-based liquid metals as reaction media for nanomaterials synthesis

Gallium-based liquid metals (LMs) and their alloys have gained prominence in the realm of flexible and stretchable electronics. Recent advances have expanded the interest to explore the electron-rich core and interface of LMs to synthesize various nanomaterials, where Ga-based LMs serve as versatile reaction media. In this paper, we delve into the latest developments within this burgeoning field. Our discussion begins by elucidating the unique attributes of LMs that render them suitable as reaction media, including their high metal solubility, low standard reduction potential, self-limiting oxidation and ultra-smooth and "layer" surface. We then provide a comprehensive categorized summary of utilizing these features to fabricate a variety of nanomaterials, including pure metallic materials (metal alloys, metal crystals, porous metals, high-entropy alloys and metallic single atoms), metal-inorganic compounds (2D metal oxides, 2D metallic inorganic compounds and 2D graphitic materials), as well as metal-organic composites (metal-organic frameworks). This paper concludes by discussing the current challenges in this field and exploring potential future directions. The versatility and unique properties of Ga-based LMs are poised to play a pivotal role in the future of nanomaterial science, paving the way for more efficient, sustainable, and innovative technological solutions.

A frogspawn inspired twin Mo2C/Ni composite with a conductive fibrous network as a robust bifunctional catalyst for advanced anion exchange membrane electrolyzers

Anion exchange membrane water electrolysis (AEMWE) is considered one of the most cost-effective methods for producing green hydrogen. However, the performance of AEMWE is still restrained by the slow reaction kinetics and poor ion/electron transport of catalysts. Herein, inspired by frogspawn, Mo2C nanoparticles coupled with Ni were in situ embedded into a N-doped porous carbon nanofiber network (Mo2C/NCNTs@Ni) by chemical crosslinking electrospinning combined with carbonization. The unique bionic structure can guarantee favorable overall structural flexibility and fast ion/electron transport kinetics. As a result of the robust hydrogen binding energy of Mo2C, as well as the synergistic impact between Ni and Mo2C nanoparticles and the conductive network resembling frogspawn, the catalyst developed demonstrates excellent performance in both the HER and OER. When employed as a bifunctional catalyst in water electrolysis, Mo2C/NCNTs@Ni delivers overpotentials of 155 mV and 320 mV at 10 mA cm-2 for the HER and OER, respectively. In addition, the Mo2C/NCNTs@Ni also displays excellent long-term durability during a continuous operation test under different currents for 50 h. The assembled AEMWE electrolyzers with Mo2C/NCNTs@Ni as both the anode and cathode can achieve a current density of 82.5 mA cm-2 at 1.99 V, indicating great potential for industrial water splitting. These results give an insight for the development of advanced bifunctional electrocatalysts for the next generation of green and efficient H2 production by water electrolysis.

Modulating the Structure and Composition of Single-Atom Electrocatalysts for CO2 reduction

Electrochemical CO2 reduction reaction (eCO2 RR) is a promising strategy to achieve carbon cycling by converting CO2 into value-added products under mild reaction conditions. Recently, single-atom catalysts (SACs) have shown enormous potential in eCO2 RR due to their high utilization of metal atoms and flexible coordination structures. In this work, the recent progress in SACs for eCO2 RR is outlined, with detailed discussions on the interaction between active sites and CO2 , especially the adsorption/activation behavior of CO2 and the effects of the electronic structure of SACs on eCO2 RR. Three perspectives form the starting point: 1) Important factors of SACs for eCO2 RR; 2) Typical SACs for eCO2 RR; 3) eCO2 RR toward valuable products. First, how different modification strategies can change the electronic structure of SACs to improve catalytic performance is discussed; Second, SACs with diverse supports and how supports assist active sites to undergo catalytic reaction are introduced; Finally, according to various valuable products from eCO2 RR, the reaction mechanism and measures which can be taken to improve the selectivity of eCO2 RR are discussed. Hopefully, this work can provide a comprehensive understanding of SACs for eCO2 RR and spark innovative design and modification ideas to develop highly efficient SACs for CO2 conversion to various valuable fuels/chemicals.

Morphology Tuning via Linker Modulation: Metal-Free Covalent Organic Nanostructures with Exceptional Chemical Stability for Electrocatalytic Water Splitting

The development of synthetic routes for the formation of robust porous organic polymers (POPs) with well-defined nanoscale morphology is fundamentally significant for their practical applications. The thermodynamic characteristics that arise from reversible covalent bonding impart intrinsic chemical instability in the polymers, thereby impeding their overall potential. Herein, a unique strategy is reported to overcome the stability issue by designing robust imidazole-linked POPs via tandem reversible/irreversible bond formation. Incorporating inherent rigidity into the secondary building units leads to robust microporous polymeric nanostructures with hollow-spherical morphologies. An in-depth analysis by extensive solid-state NMR (1D and 2D) study on 1H, 13C, and 14N nuclei elucidates the bonding and reveals the high purity of the newly designed imidazole-based POPs. The nitrogen-rich polymeric nanostructures are further used as metal-free electrocatalysts for water splitting. In particular, the rigid POPs show excellent catalytic activity toward the oxygen evolution reaction (OER) with long-term durability. Among them, the most efficient OER electrocatalyst (TAT-TFBE) requires 314 mV of overpotential to drive 10 mA cm-2 current density, demonstrating its superiority over state-of-the-art catalysts (RuO2 and IrO2).

Sodium chloride modulated construction of hollow Co/Co3O4 heterostructure with enhanced mesoscale diffusion towards overall water splitting

Fabricating an efficient electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) isthe most challenging task for overall water splitting. Herein, we utilized the confinement effect of molten sodium chloride (NaCl) to controllably prepare hollow Co/Co3O4 nanoparticles embedded into nitrogen-doped carbon (H-Co/Co3O4-NC). Experimental and theoretical investigations revealed that the interfacial interaction within Co/Co3O4 heterostructure played a pivotal role in modulating the electronic structure and facilitating the electron transfer. Meanwhile, the superiority of hollow nanostructure could promote the mesoscale mass diffusion. Remarkably, the as-prepared H-Co/Co3O4-NC catalyst achieved the low overpotentials of 316 mV and 252 mV towards OER and HER, respectively, which delivered overall water splitting with the potential of 1.76 V at a current density of 10 mA cm-2.

Anisotropic hat-like carbon nanoparticles with tunable inner hollow architectures by growth and dissolution kinetics control

The synthesis of nanoparticles with a hollow and anisotropic structure have attracted considerable interest in synthetic methodology and diverse potential applications, but endowing them with delicate control of the hollow structure and outer anisotropic morphology remains a significant challenge. In this study, anisotropic nanoparticles with hat-like morphology are prepared via a kinetics-controlled growth and dissolution strategy. Starting from forming solid polymer nanospheres with location-specific compositional chemistry distribution based on the distinct reactivity and growth kinetics of two reactants. After etching by acetone, the inhomogeneity nanospheres transformed to hat-like nanoparticles through the kinetics-controlled dissolution of two kinds of precursors. Due to chemical etching and repolymerization reactions occurring within a single nanospheres, an autonomous asymmetrical repolymerization and concave process are observed, which is novel at the nanoscale. Moreover, regulating the amount of ammonia significantly impacts the growth kinetics of precursors, primarily affecting the composition and subsequent dissolution process of solid polymer nanospheres, which play an important role in constructing polymer nanoparticles with varying morphologies and internal structures. The as-synthesized hat-like carbon nanoparticles with an open carbon structure, highly porous shell, and favorable N-doped functionalities demonstrate a potential candidate for lithium-sulfur batteries.

Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H2O2 electrosynthesis

The nanoreactor holds great promise as it emulates the natural processes of living organisms to facilitate chemical reactions, offering immense potential in catalytic energy conversion owing to its unique structural functionality. Here, we propose the utilization of precisely engineered carbon spheres as building blocks, integrating micromechanics and controllable synthesis to explore their catalytic functionalities in two-electron oxygen reduction reactions. After conducting rigorous experiments and simulations, we present compelling evidence for the enhanced mass transfer and microenvironment modulation effects offered by these mesoporous hollow carbon spheres, particularly when possessing a suitably sized hollow architecture. Impressively, the pivotal achievement lies in the successful screening of a potent, selective, and durable two-electron oxygen reduction reaction catalyst for the direct synthesis of medical-grade hydrogen peroxide disinfectant. Serving as an exemplary demonstration of nanoreactor engineering in catalyst screening, this work highlights the immense potential of various well-designed carbon-based nanoreactors in extensive applications.

Mesoscience in Hollow Multi-Shelled Structures

The prevalence of mesoscale complexity in materials science underscores the significance of the compromise in competition principle, which gives rise to the emergence of mesoscience. This principle offers valuable insights into understanding the formation process, characteristics, and performance of complex material systems, ultimately guiding the future design of such intricate materials. Hollow multi-shelled structures (HoMS) represent a groundbreaking multifunctional structural system that encompasses several spatial regimes. A plethora of mesoscale cases within HoMS present remarkable opportunities for exploring, understanding, and utilizing mesoscience, varying from the formation process of HoMS, to the mesoscale structural parameters, and finally the distinctive mass/energy transfer behaviors exhibited by HoMS. The compromise in competition between the diffusion and reaction contributes to the successful formation of multi-shells of HoMS, allowing for precise regulation of the structural parameters by dynamically varying the interplay between two dominances. Moreover, the distinct roles played by the shells and cavities within HoMS significantly influence the energy/mass transfer processes with the unique temporal-spatial resolution, providing guidance for customizing the application performance. Hopefully, the empirical and theoretical anatomy of HoMS following mesoscience would fuel new discoveries within this promising and complex multifunctional material system.

Enabling Ultrafine Ru Nanoparticles with Tunable Electronic Structures via a Double-Shell Hollow Interlayer Confinement Strategy toward Enhanced Hydrogen Evolution Reaction Performance

Engineering of the catalysts' structural stability and electronic structure could enable high-throughput H2 production over electrocatalytic water splitting. Herein, a double-shell interlayer confinement strategy is proposed to modulate the spatial position of Ru nanoparticles in hollow carbon nanoreactors for achieving tunable sizes and electronic structures toward enhanced H2 evolution. Specifically, the Ru can be anchored in either the inner layer (Ru-DSC-I) or the external shell (Ru-DSC-E) of double-shell nanoreactors, and the size of Ru is reduced from 2.2 to 0.9 nm because of the double-shell confinement effect. The electronic structures are efficiently optimized thereby stabilizing active sites and lowering the reaction barrier. According to finite element analysis results, the mesoscale mass diffusion can be promoted in the double-shell configuration. The Ru-DSC-I nanoreactor exhibits a much lower overpotential (η10 = 73.5 mV) and much higher stability (100 mA cm-2). Our work might shed light on the precise design of multishell catalysts with efficient refining electrostructures toward electrosynthesis applications.

Catalytic Conversion of Levulinic Acid to Pyrrolidone under Mild Conditions with Disordered Mesoporous Silica-Supported Pt Catalyst

Catalytic conversion of biomass-derived levulinic acid (LA) into high-valued 5-methylpyrrolidones has become an attractive case in studies of biomass utilization. Herein, we developed a disordered mesoporous Pt/MNS catalyst for this reductive amination process under room temperature and atmospheric pressure of hydrogen. The disordered mesoporous structures in support of Pt/MNS catalyst led the formation of highly dispersed Pt species via confinement effect, providing high specific area for enhancing the catalytic sites. With the synergistic effect between highly dispersed Pt species and mesoporous structures, 5-methylpyrrolidones were successfully synthesized from biomass-derived LA and primary amines with high selectivity. Mechanism studies indicated that introducing protonic acid would promote the reductive-amination process, and enamine intermediates could be detected during the in-situ DRIFT tests. Density functional theory (DFT) calculation confirmed that the hydrogenation of enamine intermediate was more accessible than that of imide intermediates, leading the excellent performance of the Pt/MNS catalyst. This work provided a green method to produce 5-methylpyrrolidone and revealed the impact of catalyst structural characteristics on the reaction process.

Hollow Mesoporous Molybdenum Single-Atom Nanozyme-Based Reactor for Enhanced Cascade Catalytic Antibacterial Therapy

Purpose

The remarkable peroxidase-like activity of single-atom nanozymes (SAzymes) allows them to catalyze the conversion of H2O2 to •OH, rendering them highly promising for antibacterial applications. However, their practical in vivo application is hindered by the near-neutral pH and insufficient H2O2 levels present in physiological systems. This study was aimed at developing a SAzyme-based nanoreactor and investigating its in vivo antibacterial activity.

Methods

We developed a hollow mesoporous molybdenum single-atom nanozyme (HMMo-SAzyme) using a controlled chemical etching approach and pyrolysis strategy. The HMMo-SAzyme not only exhibited excellent catalytic activity but also served as an effective nanocarrier. By loading glucose oxidase (GOx) with HMMo-SAzyme and encapsulating it with hyaluronic acid (HA), a nanoreactor (HMMo/GOx@HA) was constructed as glucose-triggered cascade catalyst for combating bacterial infection in vivo.

Results

Hyaluronidase (HAase) at the site of infection degraded HA, allowing GOx to convert glucose into gluconic acid and H2O2. An acid environment significantly enhanced the catalytic activity of HMMo-SAzyme to promote the further catalytic conversion of H2O2 to •OH for bacterial elimination. In vitro and in vivo experiments demonstrated that the nanoreactor had excellent antibacterial activity and negligible biological toxicity.

Conclusion

This study represents a significant advancement in developing a cascade catalytic system with high efficiency based on hollow mesoporous SAzyme, promising the advancement of biological applications of SAzyme.

Atomic Engineering Modulates Oxygen Reduction of Hollow Carbon Matrix Confined Single Metal-Nitrogen Sites for Zinc-Air Batteries

The systematical understanding of metal-dependent activity in electrocatalyzing oxygen reduction reaction (ORR), a vital reaction with sluggish kinetics for zinc-air batteries, remains quite unclear. An atomic and spatial engineering modulating ORR activity over hollow carbon quasi-sphere (HCS) confined in a series of single M-N (M = Cu, Mn, Ni) sites is reported here. Based on the theoretical prediction and experimental validation, Cu-N4 site with the lowest overpotential shows a better ORR kinetics than Mn-N4 and Ni-N4 . The ORR activity of single-atom Cu center can be further improved by decreasing the coordination number of N to two, namely Cu-N2 , due to the enhancement of electrons with lower coordination structure. Benefitting from the unique spatial confinement effect of the HCS structure in modulating electronic feature of active sites, the Cu-N2 site confined in HCS also delivers highly improved ORR kinetics and activity relative to that on planner graphene. Additionally, the best catalyst holds excellent promise in the application of zinc-air batteries. The findings will pave a new way to atomically and electronically tune active sites with high efficiency for other single-atom catalysts.

An Immunomodulatory Biomimetic Single-Atomic Nanozyme for Biofilm Wound Healing Management

Nanozyme-driven catalytic antibacterial therapy has become a promising modality for bacterial biofilm infections. However, current catalytic therapy of biofilm wounds is severely limited by insufficient catalytic efficiency, excessive inflammation, and deep tissue infection. Drawing from the homing mechanism of natural macrophages, herein, a hollow mesoporous biomimetic single-atomic nanozyme (SAN) is fabricated to actively target inflamed parts, suppress inflammatory factors, and eliminate deeply organized bacteria for enhance biofilm eradication. In the formulation, this biomimetic nanozyme (Co@SAHSs@IL-4@RCM) consists of IL-4-loaded cobalt SANs-embedded hollow sphere encapsulate by RAW 264.7 cell membrane (RCM). Upon accumulation at the infected sites through the specific receptors of RCM, Co@SAHS catalyze the conversion of hydrogen peroxide into hydroxyl radicals and are further amplify by NIR-II photothermal effect and glutathione depletion to permeate and destroy biofilm structure. This behavior subsequently causes the dissociation of RCM shell and the ensuing release of IL-4 that can reprogram macrophages, enabling suppression of oxidative injury and tissue inflammation. The work paves the way to engineer alternative "all-in-one" SANs with an immunomodulatory ability and offers novel insights into the design of bioinspired materials.

Kinetics-Driven Dual Hydrogen Spillover Effects for Ultrasensitive Hydrogen Sensing

Palladium (Pd)-modified metal oxide semiconductors (MOSs) gas sensors often exhibit unexpected hydrogen (H2 ) sensing activity through a spillover effect. However, sluggish kinetics over a limited Pd-MOS surface seriously restrict the sensing process. Here, a hollow Pd-NiO/SnO2 buffered nanocavity is engineered to kinetically drive the H2 spillover over dual yolk-shell surface for the ultrasensitive H2 sensing. This unique nanocavity is found and can induce more H2 absorption and markedly improve kinetical H2 ab/desorption rates. Meanwhile, the limited buffer-room allows the H2 molecules to adequately spillover in the inside-layer surface and thus realize dual H2 spillover effect. Ex situ XPS, in situ Raman, and density functional theory (DFT) analysis further confirm that the Pd species can effectively combine H2 to form Pd-H bonds and then dissociate the hydrogen species to NiO/SnO2 surface. The final Pd-NiO/SnO2 sensors exhibit an ultrasensitive response (0.1-1000 ppm H2 ) and low actual detection limit (100 ppb) at the operating temperature of 230 °C, which surpass that of most reported H2 sensors.

Engineering metallenes for boosting electrocatalytic biomass-oxidation-assisted hydrogen evolution reaction

Metallenes exhibit great potential for catalytic reaction, particularly for the hydrogen evolution reaction (HER) and biomass oxidation reaction, due to their favorable electronic configurations, ultrahigh specific surface areas, and highly accessible surface atoms. Therefore, metallenes can function as bifunctional electrocatalysts to boost the energy-saving biomass-oxidation-assisted HER, and have attracted great interest. Given the growing importance of green hydrogen as an alternative energy source in recent years, it is timely and imperative to summarize the recent progress and current status of metallene-based catalysts for the biomass-oxidation-assisted HER. Here, we review the recent advances in metallenes in terms of composition and structural regulations including alloying, nonmetal doping, defect engineering, surface functionalization, and heterostructure engineering strategies and their applications in driving electrocatalytic HER, with special focus on biomass-oxidation-assisted hydrogen production. The underlying structure-activity relationship and mechanisms are also comprehensively discussed. Finally, we also propose the challenges and future directions of metallene-based catalysts for the applications in biomass-oxidation-assisted HER.

Balancing Mass Transfer and Active Sites to Improve Electrocatalytic Oxygen Reduction by B,N Codoped C Nanoreactors

Mass transfer is critical in catalytic processes, especially when the reactions are facilitated by nanostructured catalysts. Strong efforts have been devoted to improving the efficacy and quantity of active sites, but often, mass transfer has not been well studied. Herein, we demonstrate the importance of mass transfer in the electrocatalytic oxygen reduction reaction (ORR) by tailoring the pore sizes. Using a confined-etching strategy, we fabricate boron- and nitrogen-doped carbon (B,N@C) electrocatalysts featuring abundant active sites but different porous structures. The ORR performance of these catalysts is found to correlate with diffusion of the reactant. The optimized B,N@C with trimodal-porous structures feature enhanced O₂ diffusion and better activity per heteroatomic site toward the ORR process. This work demonstrates the significance of the nanoarchitecture engineering of catalysts and sheds light on how to optimize structures featuring abundant active sites and enhanced mass transfer.

Nanointerfaces: Concepts and Strategies for Optical and X-ray Spectroscopic Characterization

Interfaces at the nanoscale, also called nanointerfaces, play a fundamental role in physics and chemistry. Probing the chemical and electronic environment at nanointerfaces is essential in order to elucidate chemical processes relevant for applications in a variety of fields. Many spectroscopic techniques have been applied for this purpose, although some approaches are more appropriate than others depending on the type of the nanointerface and the physical properties of the different phases. In this Perspective, we introduce the major concepts to be considered when characterizing nanointerfaces. In particular, the interplay between the characteristic length of the nanointerfaces, and the probing and information depths of different spectroscopy techniques is discussed. Differences between nano- and bulk interfaces are explained and illustrated with chosen examples from optical and X-ray spectroscopies, focusing on solid-liquid nanointerfaces. We hope that this Perspective will help to prepare spectroscopic characterization of nanointerfaces and stimulate interest in the development of new spectroscopic techniques adapted to the nanointerfaces.

Optimizing the Electronic Structure of Atomically Dispersed Ru Sites with CoP for Highly Efficient Hydrogen Evolution in both Alkaline and Acidic Media

Developing efficient and stable electrocatalysts for hydrogen evolution reaction (HER) over a wide pH range and industrial large-scale hydrogen production is critical and challenging. Here, a tailoring strategy is developed to fabricate an outstanding HER catalyst in both acidic and alkaline electrolytes containing high-density atomically dispersed Ru sites anchored in the CoP nanoparticles supported on carbon spheres (NC@Ru_SA -CoP). The obtained NC@Ru_SA -CoP catalyst exhibits excellent HER performance with overpotentials of only 15 and 13 mV at 10 mA cm^-2 in 1 m KOH and 0.5 m H₂ SO₄ , respectively. The experimental results and theoretical calculations indicate that the strong interaction between the Ru site and the CoP can effectively optimize the electronic structure of Ru sites to reduce the hydrogen binding energy and the water dissociation energy barrier. The constructed alkaline anion exchange membrane water electrolyze (AAEMWE) demonstrates remarkable durability and an industrial-level current density of 1560 mA cm^-2 at 1.8 V. This strategy provides a new perspective on the design of Ru-based electrocatalysts with suitable intermediate adsorption strengths and paves the way for the development of highly active electrocatalysts for industrial-scale hydrogen production.

Enhancing the catalytic performance of Co-N-C derived from ZIF-67 by mesoporous silica encapsulation for chemoselective hydrogenation of furfural

Developing Cr-free and non-noble metal catalysts with high activity, selectivity and durability for chemoselective hydrogenation of furfural to furfuryl alcohol is highly desirable yet challenging. In this study, we design a hollow mesoporous Co-N-C@mSiO₂ nanostructure derived from ZIF-67 via the encapsulation-pyrolysis strategy. The Co-N-C@mSiO₂ catalyst exhibits excellent catalytic performance in the furfural hydrogenation towards furfuryl alcohol with good stability, and is much better than the Co-N-C catalyst originating from plain ZIF-67 and other reported transition metal catalysts. Characterization methods and control experiments show that Co-N_x species rather than Co metal should be catalytically active sites for the above reaction. The enhanced performance is associated with abundant Co-N_x active sites, good mass transport, and the SiO₂ shell protection. This work provides a novel and facile strategy for preparing highly efficient non-precious metal catalysts to replace Cr-based and noble metal catalysts for furfural hydrogenation.

Recent Progress of Hollow Carbon Nanocages: General Design Fundamentals and Diversified Electrochemical Applications

Hollow carbon nanocages (HCNCs) consisting of sp2  carbon shells featured by a hollow interior cavity with defective microchannels (or customized mesopores) across the carbon shells, high specific surface area, and tunable electronic structure, are quilt different from the other nanocarbons such as carbon nanotubes and graphene. These structural and morphological characteristics make HCNCs a new platform for advanced electrochemical energy storage and conversion. This review focuses on the controllable preparation, structural regulation, and modification of HCNCs, as well as their electrochemical functions and applications as energy storage materials and electrocatalytic conversion materials. The metal single atoms-functionalized structures and electrochemical properties of HCNCs are summarized systematically and deeply. The research challenges and trends are also envisaged for deepening and extending the study and application of this hollow carbon material. The development of multifunctional carbon-based composite nanocages provides a new idea and method for improving the energy density, power density, and volume performance of electrochemical energy storage and conversion devices.

Amorphous NiFe Oxide-based Nanoreactors for Efficient Electrocatalytic Water Oxidation

Synergy engineering is an important way to enhance the kinetic activity of oxygen-evolution-reaction (OER) electrocatalysts. Here, we fabricated NiFe amorphous nanoreactor (NiFe-ANR) oxide as OER electrocatalysts via a mild self-catalytic reaction. Firstly, the amorphousness helps transform NiFe-ANR into highly active hydroxyhydroxides, and its many fine-grain boundaries increase active sites. More importantly, as proved by experiments and finite element analysis, the nanoreactor structure alters the spatial curvature and the mass transfer over the catalyst, thereby enriching OH^- in the catalyst surface and inner part. Thus, the catalyst with the structure of amorphous nanoreactors gained excellent activity, far superior to the NiFe catalyst with the structure of crystalline nanoreactor or amorphous non-nanoreactor. This work provides new insights into the applications and mechanisms of amorphousness and nanoreactors, embodying the "1+1>2" synergy of crystalline state and morphology.

Hollow Heterostructured Nanocatalysts for Boosting Electrocatalytic Water Splitting

The implementation of electrochemical water splitting demands the development and application of electrocatalysts to overcome sluggish reaction kinetics of hydrogen/oxygen evolution reaction (HER/OER). Hollow nanostructures, particularly for hollow heterostructured nanomaterials can provide multiple solutions to accelerate the HER/OER kinetics owing to their advantageous merit. Herein, the recent advances of hollow heterostructured nanocatalysts and their excellent performance for water splitting are systematically summarized. Starting by illustrating the intrinsically advantageous features of hollow heterostructures, achievements in engineering hollow heterostructured electrocatalysts are also highlighted with the focus on structural design, interfacial engineering, composition regulation, and catalytic evaluation. Finally, some perspective insights and future challenges of hollow heterostructured nanocatalysts for electrocatalytic water splitting are also discussed.

Kinetics Driven by Hollow Nanoreactors: An Opportunity for Controllable Catalysis

As a novel class of catalytic materials, hollow nanoreactors offer new opportunities for improving catalytic performance owing to their higher controllability on molecular kinetic behavior. Nevertheless, to achieve controllable catalysis with specific purposes, the catalytic mechanism occurring inside hollow nanoreactors remains to be further understood. In this context, this Review presents a focused discussion about the basic concept of hollow nanoreactors, the underlying theory for hollow nanoreactor-driven kinetics, and the intrinsic correlation between key structural parameters of hollow nanoreactors and molecular kinetic behaviors. We aim to provide in-depth insights into understanding kinetics occurred within typical hollow nanoreactors. The perspectives proposed in this paper may contribute to the development of the fundamental theoretical framework of hollow nanoreactor-driven catalysis.

Messenger Nanozyme for Reprogramming the Microenvironment of Rheumatoid Arthritis

Dysregulation of superoxide anion (O₂^-) and hydrogen peroxide (H₂O₂) metabolism in the microenvironment of rheumatoid arthritis (RA) drives the feedback loops of TNF-α and IL-1β thereby inducing an inflammatory storm between immune cells and joint tissue cells. Here, we combine nanoscale manganese dioxide (MnO₂) with microvesicles derived from macrophage (MMV). The former possesses superoxide dismutase (SOD) and catalase (CAT)-like activities that can modulate this imbalance, and we amplify the enzyme-like activities by using the amorphous hollow mesoporous structure and surface modification. The latter is a natural endogenous component with the parent cell-like inflammatory homing ability and a unique function of transmitting information to surrounding and distant cells (″messenger function″), which helps amorphous hollow MnO₂ (H-MnO₂) nanozymes to cloak in the blood and reach the site of inflammation, where they can not only accumulate in activated macrophages but also pretend to be ″messengers″ that are utilized by fibroblast-like synoviocytes (FLS) and chondrocytes. In addition, we also load dexamethasone sodium phosphate (DSP) for helping the nanozymes work. Messenger nanozyme (MMV-MnO₂@DSP) inherits the natural properties of MMV and mimics the enzymatic activity of SOD and CAT. It accumulates in activated macrophages to restore the metabolism of O₂^- and H₂O₂ while promoting repolarization and inhibits the feedback loops of TNF-α and IL-1β among macrophages, fibroblast-like synoviocytes, and chondrocytes, leading to anti-rheumatoid arthritis effects in vitro and in vivo.

Nanoenzyme Reactor-Based Oxidation-Induced Reaction for Quantitative SERS Analysis of Food Antiseptics

Nanoenzyme reactors based on shell-isolated colloidal plasmonic nanomaterials are well-established and widely applied in catalysis and surface-enhanced Raman scattering (SERS) sensing. In this study, a "double wing with one body" strategy was developed to establish a reduced food antiseptic sensing method using shell-isolated colloidal plasmonic nanomaterials. Gold nano particles (Au NPs) were used to synthesize the colloidal plasmonic nanomaterials, which was achieved by attaching ferrous ions (Fe²⁺), ferric ions (Fe³⁺), nitroso (NO^-) group, cyanogen (CN^-) group, and dopamine (DA) via coordinative interactions. The oxidation-induced reaction was utilized to generate •OH following the Fe²⁺-mediated Fenton reaction with the shell-isolated colloidal plasmonic nanomaterials. The •OH generated in the cascade reactor had a high oxidative capacity toward acid preservatives. Importantly, with the introduction of the signal molecule DA, the cascade reactor exhibited also induced a Raman signal change by reaction with the oxidation product (malondialdehyde) which improved the sensitivity of the analysis. In addition, the stable shell-isolated structure was effective in realizing a reproducible and quantitative SERS analysis method, which overcomes previous limitations and could extend the use of nanoenzymes to various complex sensing applications.

Biometric Photoelectrochemical-Visual Multimodal Biosensor Based on 3D Hollow HCdS@Au Nanospheres Coupled with Target-Induced Ion Exchange Reaction for Antigen Detection

Three-dimensional (3D) hollow photoactive nanomaterials can enhance light capture due to the light scattering benefiting from the unique hollow nanostructures, which contributes to the decrease in energy loss and the electron-hole recombination during the process of photoelectric conversion. Herein, a 3D hollow HCdS@Au nanosphere synthesized by the templated-assisted method and photodeposition is employed to construct a multimodal sensing platform by combining the photoelectrochemical (PEC) biosensor with colorimetric analysis and photothermal imaging. In the presence of target carcinoembryonic antigen (CEA), a sandwich structure is formed on magnetic beads based on the dual-aptamer recognition, followed by the initiation of rolling circle amplification (RCA) to bind numerous CuO-DNA probes. Upon stimulation by chlorhydric acidic, a large number of Cu²⁺ is released from CuO, which could interact with yellow HCdS@Au on electrode to produce dark CuS by ion exchange. As a result, with increased CEA level, the photocurrent is weakened and the color of electrode interface is changed from yellow to dark, which thus facilitates the PEC and colorimetric detection of CEA. Simultaneously, the formed CuS with highly photothermal effect can achieve qualitative visual analysis of CEA using a portable infrared thermal imager. This work exhibits an excellent performance for sensitive and selective detection of CEA in the dynamic working range from 0.015 to 2.4 ng/mL with a detection limit as low as 3.5 pg/mL. Moreover, the proposed PEC biosensor is successfully applied to CEA determination in human serum, which holds great promise in accurate analysis of biomarkers and early diagnosis of diseases in the clinic.

Construction of Bimetallic Metal-Organic Frameworks with the Nanosheet-Assembled Hierarchical Hollow Structure for CO2 Fixation

Incorporating secondary metal nodes with functionality into organic ligand nodes to form a bimetallic metal-organic frameworks (MOFs) would facilitate an enhancement in properties and broaden applied areas of MOFs. Hierarchical tubular Cu/Zn-MOF-74 assembled by nanosheet arrays is synthesized at ambient temperature and pressure by phase transformation of Cu-based precursor MOF in immersion solution with Zn²⁺. The content of Zn in Cu/Zn-MOF-74 can be controlled by adjusting the concentration of Zn²⁺ in immersion solution, and it can reach a maximum of 36.4%. Moreover, the catalytic activity toward cycloaddition of CO₂ with styrene oxide of Cu/Zn-MOF-74 is improved significantly compared with that of monometallic Cu-MOF-74. Meanwhile, the advanced hierarchical tubular structure contributing to enhancement in catalytic activity enables Cu/Zn-MOF-74 to present higher conversion toward this cycloaddition of CO₂ than traditional rod-like Cu/Zn-MOF-74. This templated synthesis would provide an opportunity for designing various bimetallic MOFs or MOF-based compounds with improved performances in multiple applications.