Mesoporous metallic rhodium nanoparticles

Multiscale Investigation of the Mechanism and Selectivity of CO2 Hydrogenation over Rh(111)

CO2 hydrogenation over Rh catalysts comprises multiple reaction pathways, presenting a wide range of possible intermediates and end products, with selectivity toward either CO or methane being of particular interest. We investigate in detail the reaction mechanism of CO2 hydrogenation to the single-carbon (C1) products on the Rh(111) facet by performing periodic density functional theory (DFT) calculations and kinetic Monte Carlo (kMC) simulations, which account for the adsorbate interactions through a cluster expansion approach. We observe that Rh readily facilitates the dissociation of hydrogen, thus contributing to the subsequent hydrogenation processes. The reverse water-gas shift (RWGS) reaction occurs via three different reaction pathways, with CO hydrogenation to the COH intermediate being a key step for CO2 methanation. The effects of temperature, pressure, and the composition ratio of the gas reactant feed are considered. Temperature plays a pivotal role in determining the surface coverage and adsorbate composition, with competitive adsorption between CO and H species influencing the product distribution. The observed adlayer configurations indicate that the adsorbed CO species are separated by adsorbed H atoms, with a high ratio of H to CO coverage on the Rh(111) surface being essential to promote CO2 methanation.

Ordered Mesoporous Crystalline Frameworks Toward Promising Energy Applications

Ordered mesoporous crystalline frameworks (MCFs), which possess both functional frameworks and well-defined porosity, receive considerable attention because of their unique properties including high surface areas, large pore sizes, tailored porous structures, and compositions. Construction of novel crystalline mesoporous architectures that allows for rich accessible active sites and efficient mass transfer is envisaged to offer ample opportunities for potential energy-related applications. In this review, the rational synthesis, unique structures, and energy applications of MCFs are the main focus. After summarizing the synthetic approaches, an emphasis is placed on the delicate control of crystallites, mesophases, and nano-architectures by concluding basic principles and showing representative examples. Afterward, the currently fabricated components of MCFs such as metals, metal oxides, metal sulfides, and metal-organic frameworks are described in sequence. Further, typical applications of MCFs in rechargeable batteries, supercapacitors, electrocatalysis, and photocatalysis are highlighted. This review ends with the possible development and synthetic challenges of MCFs as well as a future prospect for high-efficiency energy applications, which underscores a pathway for developing advanced materials.

Hofmann-Type Cyanide Bridged Coordination Polymers for Advanced Functional Nanomaterials

Since the discovery of Hofmann clathrates of inorganic cyanide bridged coordination polymers (Hofmann-type CN-CPs), extensive research is done to understand their behavior during spin transitions caused by guest molecules or external stimuli. Lately, research on their nanoscale architectures for sensors and switching devices is of interest. Their potential is reported for producing advanced functional inorganic materials in two-dimensional (2D) morphology using a scalable solid-state thermal treatment method. For instance, but not restricted to, alloys, carbides, chalcogenides, oxides, etc. Simultaneously, their in situ crystallization at graphene oxide (GO) nanosheet surfaces, followed by a subsequent self-assembly to build layered lamellar structures, is reported providing hybrid materials with a variety of uses. Hence, an overview of the most recent developments is presented here in the synthesis of nanoscale structures, including thin films and powders, using Hofmann-type CN-CPs. Also thoroughly demonstrated are the most recent synthetic ideas with the modest control over the size and shape of nanoscale particles. Additionally, in order to create new functional hybrid materials for electrical and energy applications, their thermal decomposition in various environments and hybridization with GO and other guest molecules is examined. This review article also conveyed their spin transition, astounding innovative versatile adhesives, and structure features.

Mesoporous TiO2 Single-Crystal Particles from Controlled Crystallization-Driven Mono-Micelle Assembly as an Efficient Photocatalyst

Mesoporous materials with crystalline frameworks have been widely explored in many fields due to their unique structure and crystalline feature, but accurate manipulations over crystalline scaffolds, mainly composed of uncontrolled polymorphs, are still lacking. Herein, we explored a controlled crystallization-driven monomicelle assembly approach to construct a type of uniform mesoporous TiO2 particles with atomically aligned single-crystal frameworks. The resultant mesoporous TiO2 single-crystal particles possess an angular shape ∼80 nm in diameter, good mesoporosity (a high surface area of 112 m2 g-1 and a mean pore size at 8.3 nm), and highly oriented anatase frameworks. By adjusting the evaporation rate during assembly, such a facile solution-processed strategy further enables the regulation of the particle size and mesopore size without the destruction of the oriented crystallites. Such a combination of ordered mesoporosity and crystalline orientation provides both effective mass and charge transportation, leading to a significant increase in the hydrogen generation rate. A maximum hydrogen evolution rate of 12.5 mmol g-1 h-1 can be realized, along with great stability under solar light. Our study is envisaged to extend the possibility of mesoporous single crystal growth to a range of functional ceramics and semiconductors toward advanced applications.

Anisotropic Interface Successive Assembly for Bowl-Shaped Metal-Organic Framework Nanoreactors with Precisely Controllable Meso-/Microporous Nanodomains

Colloidal metal-organic framework (MOF) nanoparticles, with tailored asymmetric nanoarchitectures and hierarchical meso-/microporosities, have significant implications in high-performance nanocatalysts, nanoencapsulation carriers, and intricate assembly architectures. However, the methodology that could achieve precise control over the anisotropic growth of asymmetric MOF particles with tailored distributions of meso- and microporous regions has not yet been established. In this study, we introduce a facile anisotropic interface successive assembly approach to synthesize asymmetric core-shell MOF (ZIF-67) nanobowls with worm-like mesopores in the core and intrinsic micropores in the shell. Our synthesis pathway relies on anisotropic nucleation of mesoporous MOF nanohemispheres on emulsion interfaces through the cooperative assembly of surfactants and MOF precursors. This is followed by the growth of microporous MOF layers on both interfaces of mesoporous cores and emulsion droplets, resulting in a hierarchically porous core-shell nanostructure. By utilizing this multi-interface-driven approach, we enable the creation of diverse geometries and distributions of mesopores and micropores in asymmetric MOF nanoarchitectures. The obtained bowl-like meso-/microporous core-shell ZIF-67 particles exhibit enhanced catalytic activity for CO2 cycloaddition, attributed to reactant accumulation within the bowl-like architecture, active site accessibility in the open mesoporous core, and improved structural stability. Overall, our study provides insights and inspiration for exploring the intricate asymmetric nanostructures of hierarchically porous MOFs with diverse potential applications.

Facile one-step synthesis of mesoporous Pt-based alloy nanospheres for ethanol electrooxidation

Mesoporous Pt-based alloy nanospheres were prepared via a one-step soft-template strategy. The regulation of electronic structure, lattice contraction and abundant active sites endowed the mesoporous Pt-based catalysts with remarkable electrochemical activity towards ethanol oxidation reaction.

Recovery of platinum group metal resources from high-level radioactive liquid wastes by non-contact photoreduction

Recovery of platinum group metals (PGMs) including palladium (Pd), rhodium (Rh), and ruthenium (Ru) from high-level radioactive liquid waste (HLLW) possesses enormous environmental and economic benefits. A non-contact photoreduction method was herein developed to selectively recover each PGM from HLLW. Soluble Pd(II), Rh(III), and Ru(III) ions were reduced to insoluble zero-valent metals and separated from simulated HLLW containing neodymium (Nd) as a representative for lanthanides, another main component in HLLW. Detailed investigation on the photoreduction of different PGMs revealed that Pd(II) could be reduced under 254- or 300-nm UV exposure using either ethanol or isopropanol as reductants. Only 300-nm UV light enabled the reduction of Rh(III) in the presence of ethanol or isopropanol. Ru(III) was the most difficult to reduce, which was only realized by 300-nm UV illumination in isopropanol solution. The effects of pH was also studied, suggesting that lower pH favored the separation of Rh(III) but hindered the reduction of Pd(II) and Ru(III). A delicate three-step process was accordingly designed to achieve the selective recovery of each PGM from simulated HLLW. Pd(II) was reduced by 254-nm UV light with the help of ethanol in the first step. Then Rh(III) was reduced by 300-UV light in the second step after the pH was adjusted to 0.5 to suppress the Ru(III) reduction. In the third step, Ru(III) was reduced by 300-nm UV light after isopropanol was added and the pH was adjusted to 3.2. The separation ratios of Pd, Rh, and Ru exceeded 99.8%, 99.9%, and 90.0%, respectively. Meanwhile, all Nd(III) still remained in the simulated HLLW. The separation coefficients between Pd/Rh and Rh/Ru exceeded 56,000 and 75,000, respectively. This work may provide an alternative method to recover PGMs from HLLW, which minimize the secondary radioactive wastes compared with other approaches.

Mesoporous multimetallic nanospheres with exposed highly entropic alloy sites

Multimetallic alloys (MMAs) with various compositions enrich the materials library with increasing diversity and have received much attention in catalysis applications. However, precisely shaping MMAs in mesoporous nanostructures and mapping the distributions of multiple elements remain big challenge due to the different reduction kinetics of various metal precursors and the complexity of crystal growth. Here we design a one-pot wet-chemical reduction approach to synthesize core-shell motif PtPdRhRuCu mesoporous nanospheres (PtPdRhRuCu MMNs) using a diblock copolymer as the soft template. The PtPdRhRuCu MMNs feature adjustable compositions and exposed porous structures rich in highly entropic alloy sites. The formation processes of the mesoporous structures and the reduction and growth kinetics of different metal precursors of PtPdRhRuCu MMNs are revealed. The PtPdRhRuCu MMNs exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 10, 13, and 28 mV at a current density of 10 mA cm-2 in alkaline (1.0 M KOH), acidic (0.5 M H2SO4), and neutral (1.0 M phosphate buffer solution (PBS)) electrolytes, respectively. The accelerated kinetics of the HER in PtPdRhRuCu MMNs are derived from multiple compositions with synergistic interactions among various metal sites and mesoporous structures with excellent mass/electron transportation characteristics.

Nanoarchitectonics of Metallene Materials for Electrocatalysis

Controlling the synthesis of metal nanostructures is one approach for catalyst engineering and performance optimization in electrocatalysis. As an emerging class of unconventional electrocatalysts, two-dimensional (2D) metallene electrocatalysts with ultrathin sheet-like morphology have gained ever-growing attention and exhibited superior performance in electrocatalysis owing to their distinctive properties originating from structural anisotropy, rich surface chemistry, and efficient mass diffusion capability. Many significant advances in synthetic methods and electrocatalytic applications for 2D metallenes have been obtained in recent years. Therefore, an in-depth review summarizing the progress in developing 2D metallenes for electrochemical applications is highly needed. Unlike most reported reviews on the 2D metallenes, this review starts by introducing the preparation of 2D metallenes based on the classification of the metals (e.g., noble metals, and non-noble metals) instead of synthetic methods. Some typical strategies for preparing each kind of metal are enumerated in detail. Then, the utilization of 2D metallenes in electrocatalytic applications, especially in the electrocatalytic conversion reactions, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, fuel oxidation reaction, CO₂ reduction reaction, and N₂ reduction reaction, are comprehensively discussed. Finally, current challenges and opportunities for future research on metallenes in electrochemical energy conversion are proposed.

Stepwise Monomicelle Assembly for Highly Ordered Mesoporous TiO2 Membranes with Precisely Tailored Mesophase and Porosity

Mesoporous materials with crystalline frameworks have been acknowledged as very attractive materials in various applications. Nevertheless, due to the cracking issue during crystallization and incompatible hydrolysis and assembly, the precise control for crystalline mesoscale membranes is quite infertile. Herein, we presented an ingenious stepwise monomicelle assembly route for the syntheses of highly ordered mesoporous crystalline TiO₂ membranes with delicately controlled mesophase, mesoporosity, and thickness. Such a process involves the preparation of monomicelle hydrogels and follows self-assembly by stepwise solvent evaporation, which enables the sensitive hydrolysis of TiO₂ oligomers and dilatory micelle assembly to be united. In consequence, the fabricated mesoporous TiO₂ membranes exhibit a broad flexibility, including tunable ordered mesophases (worm-like, hexagonal p6mm to body-centered cubic Im3̅m), controlled mesopore sizes (3.0-8.0 nm), and anatase grain sizes (2.3-8.4 nm). Besides, such mesostructured crystalline TiO₂ membranes can be extended to diverse substrates (Ti, Ag, Si, FTO) with tailored thickness. The great mesoporosity of the in situ fabricated mesoscopic membranes also affords excellent pseudocapacitive behavior for sodium ion storage. This study underscores a novel pathway for balancing the interaction of precursors and micelles, which could have implications for synthesizing crystalline mesostructures in higher controllability.

Covalent organic framework-supported ultrasmall Rh nanoparticles as peroxidase mimics for colorimetric sensing of cysteine

Covalent organic frameworks (COFs), as a novel porous organic polymer with periodic and highly ordered structure, are ideal carrier matrix for metal nanoparticles due to high specific surface area, good stability, controllable pore size, and structural tunability. In this work, COFs are used as a carrier to in-situ grow ultrasmall rhodium nanoparticles (Rh NPs, ∼2.4 nm), which are uniformly distributed in the pores and on the surfaces of the COFs. The formed composite (COF-Rh) shows excellent peroxidase-mimetic activity benefiting from the good catalytic activity of ultrafine and highly dispersed Rh NPs as well as the high affinity of COFs to organic molecules (i.e., catalytic substrates). Cysteine (Cys) can inhibit the peroxidase-like activity of COF-Rh due to the interaction of -SH in Cys with Rh and the reduction of oxidized peroxidase substrate by Cys. By regulating the peroxidase-like activity of the system, a colorimetric method is successfully developed for Cys detection. Using smartphone as a readout, a portable strategy is further proposed for rapid and visual sensing of Cys.

Noble-Metal-Metalloid Alloy Architectures: Mesoporous Amorphous Iridium-Tellurium Alloy for Electrochemical N2 Reduction

Amorphous noble metals with high surface areas have attracted significant interest as heterogeneous catalysts due to the numerous dangling bonds and abundant unsaturated surface atoms created by the amorphous phase. However, synthesizing amorphous noble metals with high surface areas remains a significant challenge due to strong isotropic metallic bonds. This paper describes the first example of a mesoporous amorphous noble metal alloy [iridium-tellurium (IrTe)] obtained using a micelle-directed synthesis method. The resulting mesoporous amorphous IrTe electrocatalyst exhibits excellent performance in the electrochemical N₂ reduction reaction. The ammonia yield rate is 34.6 μg mg^-1 h^-1 with a Faradaic efficiency of 11.2% at -0.15 V versus reversible hydrogen electrode in 0.1 M HCl solution, outperforming comparable crystalline and Ir metal counterparts. The interconnected porous scaffold and amorphous nature of the alloy create a complementary effect that simultaneously enhances N₂ absorption and suppresses the hydrogen evolution reaction. According to theoretical simulations, incorporating Te in the IrTe alloy effectively strengthens the adsorption of N₂ and lowers the Gibbs free energy for the rate-limiting step of the electrocatalytic N₂ reduction reaction. Mesoporous chemistry enables a new route to achieve high-performance amorphous metalloid alloys with properties that facilitate the selective electrocatalytic reduction of N₂.

Controllable Preparation of Gold Nanocrystals with Different Porous Structures for SERS Sensing

Porous Au nanocrystals (Au NCs) have been widely used in catalysis, sensing, and biomedicine due to their excellent localized surface plasma resonance effect and a large number of active sites exposed by three-dimensional internal channels. Here, we developed a ligand-induced one-step method for the controllable preparation of mesoporous, microporous, and hierarchical porous Au NCs with internal 3D connecting channels. At 25 °C, using glutathione (GTH) as both a ligand and reducing agent combined with the Au precursor to form GTH-Au(I), and under the action of the reducing agent ascorbic acid, the Au precursor is reduced in situ to form a dandelion-like microporous structure assembled by Au rods. When cetyltrimethylammonium bromide (C₁₆TAB) and GTH are used as ligands, mesoporous Au NCs formed. When increasing the reaction temperature to 80 °C, hierarchical porous Au NCs with both microporous and mesoporous structures will be synthesized. We systematically explored the effect of reaction parameters on porous Au NCs and proposed possible reaction mechanisms. Furthermore, we compared the SERS-enhancing effect of Au NCs with three different pore structures. With hierarchical porous Au NCs as the SERS base, the detection limit for rhodamine 6G (R6G) reached 10^-10 M.

Shape-Preserving Transformation of Electrodeposited Macroporous Microparticles for Single-Particle SERS Applications

Microparticles composed of bicontinuous and ordered macropores are important in many applications. However, rational integration of ordered macropores into a single crystalline microparticle remains a challenge. Here, we report a method to prepare three-dimensionally ordered macroporous (3DOM) Ag₇O₈NO₃ micropyramids via selectively cementing the colloidal crystal templates via an electrochemical method and their shape-preserving transformation into 3DOM Ag micropryamids formed by Ag nanoparticles via a chemical reduction process. The interconnected macropores facilitated the transportation and enrichment of the analyte molecules into the 3DOM Ag micropyramids. The dense Ag nanoparticles on the skeletons of the 3DOM Ag micropyramids provided strong electromagnetic fields. Taken together, a 3DOM Ag micropyramid as a kind of single-particle surface-enhanced Raman scattering (SERS) sensing substrate demonstrated high SERS sensitivity and outstanding SERS signal reproducibility. We explored the application of 3DOM Ag micropyramids in SERS detection of biomolecules (e.g., adenosine, adenine, hemoglobin bovine, and lysozyme) and proved their potentials in distinguishing exosomes from tumor and non-tumor cells. The method can be extended to prepared 3DOM structures of other materials with promising applications in sensing, separation, and catalytic fields.

Microwave-assisted synthesis of octahedral Rh nanocrystals and their performance for electrocatalytic oxidation of formic acid

Uniform and well-defined octahedral Rh nanocrystals were rapidly synthesized in a domestic microwave oven for only 140 s of irradiation by reducing Rh(acac)₃ with tetraethylene glycol (TEG) as both a solvent and a reducing agent in the presence of an appropriate amount of KI, didecyl dimethyl ammonium chloride (DDAC), ethylene diamine (EDA) and polyvinylpyrrolidone (PVP). KI, DDAC and EDA were essential for the creation of octahedral Rh nanocrystals. Electrochemical measurements showed a significantly enhanced electrocatalytic activity and stability for the as-prepared octahedral Rh nanocrystals compared with commercial Rh black.

Recent Trends in Metal Nanoparticles Decorated 2D Materials for Electrochemical Biomarker Detection

Technological advancements in the healthcare sector have pushed for improved sensors and devices for disease diagnosis and treatment. Recently, with the discovery of numerous biomarkers for various specific physiological conditions, early disease screening has become a possibility. Biomarkers are the body's early warning systems, which are indicators of a biological state that provides a standardized and precise way of evaluating the progression of disease or infection. Owing to the extremely low concentrations of various biomarkers in bodily fluids, signal amplification strategies have become crucial for the detection of biomarkers. Metal nanoparticles are commonly applied on 2D platforms to anchor antibodies and enhance the signals for electrochemical biomarker detection. In this context, this review will discuss the recent trends and advances in metal nanoparticle decorated 2D materials for electrochemical biomarker detection. The prospects, advantages, and limitations of this strategy also will be discussed in the concluding section of this review.

Nanomaterials as Photocatalysts-Synthesis and Their Potential Applications

Increasing demand for energy and environmental degradation are the most serious problems facing the man. An interesting issue that can contribute to solving these problems is the use of photocatalysis. According to literature, solar energy in the presence of a photocatalyst can effectively (i) be converted into electricity/fuel, (ii) break down chemical and microbial pollutants, and (iii) help water purification. Therefore, the search for new, efficient, and stable photocatalysts with high application potential is a point of great interest. The photocatalysts must be characterized by the ability to absorb radiation from a wide spectral range of light, the appropriate position of the semiconductor energy bands in relation to the redox reaction potentials, and the long diffusion path of charge carriers, besides the thermodynamic, electrochemical, and photoelectrochemical stabilities. Meeting these requirements by semiconductors is very difficult. Therefore, efforts are being made to increase the efficiency of photo processes by changing the electron structure, surface morphology, and crystal structure of semiconductors. This paper reviews the recent literature covering the synthesis and application of nanomaterials in photocatalysis.

Ultrasensitive lateral flow immunoassay for staphylococcal enterotoxin B using nanosized fluorescent metal-organic frameworks

Owing to their outstanding optical properties and superior physical/chemical stability, dye-doped fluorescent nanoparticles (NPs) are growing exponentially as signal labels of immunochromatographic lateral flow immunoassay (LFA) for the detection of various analytes. However, the key challenge in the design of these fluorescent NPs is to confine the fluorophores inside NPs at extreme concentrations, at which dyes tend to self-quench resulting from the formation of non-fluorescent aggregates. Looking for other advantageous nanomaterials, we propose for the first time the use of a nanosized fluorescent metal-organic framework (nanoMOF) in LFA for the detection of staphylococcal enterotoxin B (SEB) as a model analyte. Featured by the chromophore assembly, the nanoMOF exhibited a high dye loading (∼60%) and strong fluorescence intensity, which was due to the reduced self-quenching of dyes in a variety of MOF matrices. The strong green fluorescence intensity of the nanoMOF gives a high contrast against the background of the strips and the sensitivity reflected by photoluminescence was improved by the enhanced antenna effect. Furthermore, due to the high surface area for antibody stemming, the limit of detection (LOD) of the MOF based LFA for SEB detection was as low as 0.025 ng mL^-1. The compatibility of the MOF based LFA with dairy samples and its stability under long-term storage conditions were also demonstrated. The integration of a nanoMOF into LFA to detect toxins could inspire the utilization of such nanomaterial-based labels in similar immunochromatographic testing methods to improve their performance.

Ultrathin rhodium nanosheet-gold nanowire nanocomposites for alkaline methanol oxidation reaction

Electrostatically assembled ultrathin rhodium nanosheet-gold nanowire nanocomposites (Rh-Au CNSs) were used as an advanced electrocatalyst for the methanol oxidation reaction, which revealed a mass activity of 355 mA mg_Rh^-1 at 0.607 V potential, much higher than single metal Rh nanosheets (273 mA mg_Rh^-1) and commercial Rh nanoparticles (165 mA mg_Rh^-1).

Rhodium-Tellurium Nanorod Synthesis Using Galvanic Replacement-Polyol Regrowth for Thermo-Dynamic Dual-Modal Cancer Phototherapy

Rh is a noble metal introduced in bioapplications, including diagnosis and therapy, in addition to its consolidated utilization in organic catalysis and electrocatalysis. Herein, we designed the synthesis of highly crystalline Rh nanocrystal-decorated Rh-Te nanorods (RhTeNRs) through galvanic replacement of sacrificial Te nanorod (TeNR) templates and subsequent polyol regrowth. The obtained RhTeNRs showed excellent colloidal stability and efficient heat dissipation and photocatalytic activity under various laser irradiation wavelengths. Based on the confirmed biocompatibility, RhTeNRs were introduced into in vitro and in vivo cancer phototherapies. The results confirmed the selective physical death of cancer cells in the local area through laser irradiation. While chemotherapy does not guarantee successful treatment due to side effects and resistance, phototherapy using heat and reactive oxygen species generation of RhTeNRs induces physical death.

Dynamic Coassembly of Amphiphilic Block Copolymer and Polyoxometalates in Dual Solvent Systems: An Efficient Approach to Heteroatom-Doped Semiconductor Metal Oxides with Controllable Nanostructures

Dynamic coassembly of block copolymers (BCPs) with Keggin-type polyoxometalates (POMs) is developed to synthesize heteroatom-doped tungsten oxide with controllable nanostructures, including hollow hemispheres, nanoparticles, and nanowires. The versatile coassembly in dual n-hexane/THF solvent solution enables the fomation of poly(ethylene oxide)-b-polystyrene (PEO-b-PS)/POMs (e.g., silicotungstic acid, H₄SiW₁₂O₄₀) nanocomposites with different morphologies such as spherical vesicles, inverse spherical micelles, and inverse cylindrical micelles, which can be readily converted into diverse nanostructured metal oxides with high surface area and unique properties via in situ thermal-induced structural evolution. For example, uniform silicon-doped WO₃ (Si-WO₃) hollow hemispheres derived from coassembly of PEO-b-PS with H₄SiW₁₂O₄₀ were utilized to fabricate gas sensing devices which exhibit superior gas sensing performance toward acetone, thanks to the selective gas-solid interface catalytic reaction that induces resistance changes of the devices due to the high specific surface areas, abundant oxygen vacancies, and the Si-doping induced metastable ε-phase of WO₃. Furthermore, density functional theory (DFT) calculation reveals the mechanism about the high sensitivity and selectivity of the gas sensors. On the basis of the as-fabricated devices, an integrated gas sensor module was constructed, which is capable of real-time monitoring the environmental acetone concentration and displaying relevant sensing results on a smart phone via Bluetooth communication.

Mesoporous platinum nanoparticles as a peroxidase mimic for the highly sensitive determination of C-reactive protein

The generation of a mesoporous structure in platinum nanoparticles can effectively enhance physical and chemical properties. In this study, mesoporous platinum nanoparticles (MPNs) were synthesized by a soft template-mediated one-pot chemical method. To develop a mesoporous structure, Pluronic F-127 was employed. The Pluronic F-127 surfactant forms self-assembled micelles, and the micelles act as the pore-directing agents in the synthesis of nanoparticles. Scanning electron microscopy results revealed that the MPN had a uniform size of 70 nm on average and a distinct mesoporous structure. The development of a concave mesoporous structure on the surface of the MPNs can increase the surface area and facilitate the efficient transport of reactants. The synthesized MPNs exhibited peroxidase-like activity. Furthermore, the MPNs showed excellent catalytic efficiency compared to HRP, due to the high surface area derived from the presence of the mesoporous structure. The peroxidase-like MPNs were applied to the enzyme-linked immunosorbent assay (ELISA) of C-reactive protein (CRP). The MPN-based ELISA exhibited sensitive CRP detection in the range from 0.24 to 7.8 ng/mL with a detection limit of 0.13 ng/mL. Moreover, the recoveries of the CRP concentrations in spiked human serum were 98.6% and 102%. These results demonstrate that as a peroxidase mimic, the MPNs can replace the natural enzymes in conventional ELISA for sensitive CRP detection.

Expeditious Electrochemical Synthesis of Mesoporous Chalcogenide Flakes: Mesoporous Cu2 Se as a Potential High-Rate Anode for Sodium-Ion Battery

Nanostructured copper selenide (Cu₂ Se) attracts much interest as it shows outstanding performance as thermoelectric, photo-thermal, and optical material. The mesoporous structure is also a promising morphology to obtain better performance for electrochemical and catalytic applications, thanks to its high surface area. A simple one-step electrochemical method is proposed for mesoporous chalcogenides synthesis. The synthesized Cu₂ Se material has two types of mesopores (9 and 18 nm in diameter), which are uniformly distributed inside the flakes. These materials are also implemented for sodium (Na) ion battery (NIB) anode as a proof of concept. The electrode employing the mesoporous Cu₂ Se exhibits superior and more stable specific capacity as a NIB anode compared to the non-porous samples. The electrode also exhibits excellent rate tolerance at each current density, from 100 to 1000 mA g^-1 . It is suggested that the mesoporous structure is advantageous for the insertion of Na ions inside the flakes. Electrochemical analysis indicates that the mesoporous electrode possesses more prominent diffusion-controlled kinetics during the sodiation-desodiation process, which contributes to the improvement of Na-ion storage performance.

Noble-Metal-Based Hollow Mesoporous Nanoparticles: Synthesis Strategies and Applications

As second-generation mesoporous materials, mesoporous noble metals (NMs) are of significant interest for their wide applications in catalysis, sensing, bioimaging, and biotherapy owing to their structural and metallic features. The introduction of interior hollow cavity into NM-based mesoporous nanoparticles (MNs), which subtly integrate hierarchical hollow and mesoporous structure into one nanoparticle, produces a new type of hollow MNs (HMNs). Benefiting from their higher active surface, better electron/mass transfer, optimum electronic structure, and nanoconfinement space, NM-based HMNs exhibit their high efficiency in enhancing catalytic activity and stability and tuning catalytic selectivity. In this review, recent progress in the design, synthesis, and catalytic applications of NM-based HMNs is summarized, including the findings of the groups. Five main strategies for synthesizing NM-based HMNs, namely silica-assisted surfactant-templated nucleation, surfactant-templated sequential nucleation, soft "dual"-template, Kirkendall effect in synergistic template, and galvanic-replacement-assisted surfactant template, are described in detail. In addition, the applications in ethanol oxidation electrocatalysis and hydrogenation reactions are discussed to highlight the high activity, enhanced stability, and optimal selectivity of NM-based HMNs in (electro)catalysis. Finally, the further outlook that may lead the directions of synthesis and applications of NM-based HMNs is prospected.

Versatile synthesis of dendritic mesoporous rare earth-based nanoparticles

Rare earth-based nanomaterials that have abundant optical, magnetic, and catalytic characteristics have many applications. The controllable introduction of mesoporous channels can further enhance its performance, such as exposing more active sites of rare earth and improving the loading capacity, yet remains a challenge. Here, we report a universal viscosity-mediated assembly strategy and successfully endowed rare earth-based nanoparticles with central divergent dendritic mesopores. More than 40 kinds of dendritic mesoporous rare earth-based (DM-REX) nanoparticles with desired composition (single or multiple rare earth elements, high-entropy compounds, etc.), particle diameter (80 to 500 nanometers), pore size (3 to 20 nanometers), phase (amorphous hydroxides, crystalline oxides, and fluorides), and architecture were synthesized. Theoretically, a DM-REX nanoparticle library with 393,213 kinds of possible combinations can be constructed on the basis of this versatile method, which provides a very broad platform for the application of rare earth-based nanomaterials with rational designed functions and structures.

A Porous Bimetallic Au@Pt Core-Shell Oxygen Generator to Enhance Hypoxia-Dampened Tumor Chemotherapy Synergized with NIR-II Photothermal Therapy

The characteristic hypoxia of solid tumors and inadequate oxygen supply become a key causation of the resistance to chemotherapy in cancer treatment. Herein, a bimetallic oxygen nanogenerator, i.e., porous Au@Pt core-shell nanostructures, is particularly developed to reduce the multidrug resistance by oxygenating the tumor along with synergistic chemo-photothermal therapy for efficient tumor eradication. The porous platinum (Pt) shell was able to catalyze oxygen generation from endogenous hydrogen peroxide in the tumor, reducing the exocytosis of doxorubicin (DOX) via suppressed expression of hypoxia-inducible factor-1α, multidrug resistance gene 1, and P-glycoprotein. The strong absorbance of Au@Pt nanostructures in NIR window II enabled NIR-II photothermal therapy. Further incorporation of DOX into the mesopores of Au@Pt nanostructures with the assistance of phase change materials (PCM) led to the formulation of Au@Pt-DOX-PCM-PEG nanotherapeutics for NIR-II-activated chemotherapy. This work presents an efficient H₂O₂-driven oxygenerator for enhanced hypoxia-dampened chemotherapy and NIR-II photothermal therapy.

Biological Synthesis of Silver Nanoparticles and Prospects in Plant Disease Management

Exploration of nanoparticles (NPs) for various biological and environmental applications has become one of the most important attributes of nanotechnology. Due to remarkable physicochemical properties, silver nanoparticles (AgNPs) are the most explored and used NPs in wide-ranging applications. Also, they have proven to be of high commercial use since they possess great chemical stability, conductivity, catalytic activity, and antimicrobial potential. Though several methods including chemical and physical methods have been devised, biological approaches using organisms such as bacteria, fungi, and plants have emerged as economical, safe, and effective alternatives for the biosynthesis of AgNPs. Recent studies highlight the potential of AgNPs in modern agricultural practices to control the growth and spread of infectious pathogenic microorganisms since the introduction of AgNPs effectively reduces plant diseases caused by a spectrum of bacteria and fungi. In this review, we highlight the biosynthesis of AgNPs and discuss their applications in plant disease management with recent examples. It is proposed that AgNPs are prospective NPs for the successful inhibition of pathogen growth and plant disease management. This review gives a better understanding of new biological approaches for AgNP synthesis and modes of their optimized applications that could contribute to sustainable agriculture.

Sulfate-Enabled Nitrate Synthesis from Nitrogen Electrooxidation on a Rhodium Electrocatalyst

The electrocatalytic nitrogen oxidation reaction (NOR) to generate nitrate is gaining increasing attention as an alternative approach to the conventional industrial manufacture. But, current progress in NOR is limited by the difficulties in activation and conversion of the strong N≡N bond (941 kJ mol^-1 ). Herein, we designed to utilize sulfate to enhance NOR performance over an Rh electrocatalyst. After the addition of sulfate, the inert Rh nanoparticles exhibited superior NOR performance with a nitrate yield of 168.0 μmol g_cat ^-1  h^-1 . The ¹⁵ N isotope-labeling experiment confirmed the produced nitrate from nitrogen electrooxidation. A series of electrochemical in situ characterizations and theoretical calculation unveiled that sulfate promoted nitrogen adsorption and decreased the reaction energy barrier, and in situ formed sulfate radicals reduced the activation energy of the potential-determining step, thus accelerating NOR.

A General Concurrent Template Strategy for Ordered Mesoporous Intermetallic Nanoparticles with Controllable Catalytic Performance

We report a general concurrent template strategy for precise synthesis of mesoporous Pt-/Pd-based intermetallic nanoparticles with desired morphology and ordered mesostructure. The concurrent template not only supplies a mesoporous metal seed for re-crystallization growth of atomically ordered intermetallic phases with unique atomic stoichiometry but also provides a nanoconfinement environment for nanocasting synthesis of mesoporous nanoparticles with ordered mesostructure and rhombic dodecahedral morphology under elevated temperature. Using the selective hydrogenation of 3-nitrophenylacetylene as a proof-of-concept catalytic reaction, mesoporous intermetallic PtSn nanoparticles exhibited remarkably controllable intermetallic phase-dependent catalytic selectivity and excellent catalytic stability. This work provides a very powerful strategy for precise preparation of ordered mesoporous intermetallic nanocrystals for application in selective catalysis and fuel cell electrocatalysis.

Self-electrochemiluminescence biosensor based on CRISPR/Cas12a and PdCuBP@luminol nanoemitter for highly sensitive detection of cytochrome c oxidase subunit III gene of acute kidney injury

The cytochrome c oxidase subunit III (COX III) gene is a powerful biomarker for the early diagnosis of acute kidney injury. However, current methods for COX III gene detection are usually laborious and time-consuming, with limited sensitivity. Herein, we report a novel self-electrochemiluminescence (ECL) biosensor for highly sensitive detection of the COX III gene based on CRISPR/Cas12a and nanoemitters of luminol-loaded multicomponent metal-metalloid PdCuBP alloy mesoporous nanoclusters. The nanoemitter with excellent self-ECL in neutral media exhibited a high specific surface area for binding luminol and outstanding oxidase-like catalytic activity toward dissolved O₂. Meanwhile, the CRISPR/Cas12a system, as a target-trigger, was employed to specifically recognize the COX III gene and efficiently cleave the interfacial quencher of dopamine-labeled hairpin DNA. As a result, the ECL biosensor showed superior analytical performance for COX III gene detection without exogenous coreactant. Benefiting from the high-efficiency ECL emission of the nanoemitter and Cas12a-mediated interfacial cleavage of the quencher, the developed ECL biosensor exhibited high sensitivity to COX III with a low detection limit of 0.18 pM. The established ECL biosensing method possessed excellent practical performance in urine samples. Meaningfully, the proposed strategy presents promising prospects for nucleic acid detection in the field of clinical diagnostics.

Liquid Metal Interfacial Growth and Exfoliation to Form Mesoporous Metallic Nanosheets for Alkaline Methanol Electroreforming

Two-dimensional (2D) materials have spurred great interest in the field of catalysis due to their fascinating electronic and thermal transport properties. However, adding uniform mesopores to 2D metallic materials has remained a great challenge owing to the inherent high surface energy. Here, we introduce a generic liquid metal interfacial growth and exfoliation strategy to synthesize a library of penetrating mesoporous metallic nanosheets. The formation of liquid-metal/water interface promotes the adsorption of metal ion-encapsulated copolymer micelles, induces the self-limiting galvanic replacement reaction, and enables the exfoliation of products under mechanical agitation. These 2D mesoporous metallic nanosheets with large lateral size, narrow thickness distribution, and uniform perforated structure provide facilitated channels and abundant active sites for catalysis. Typically, the generated mesoporous PtRh nanosheets (mPtRh NSs) exhibit superior electroactivity and durability in hydrogen evolution reaction as well as methanol electrooxidation in alkaline media. Moreover, the constructed symmetric mPtRh NSs cell requires only a relative low electrolysis voltage to achieve methanol-assisted hydrogen production compared with traditional overall water electrolysis. The work reveals a specific growth pattern of noble metals at the liquid-metal/water interface and thus introduces a versatile strategy to form 2D penetrating mesoporous metallic nanomaterials with extensive high-performance applications.

Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb₂O₃. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of ~44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics.

Synthesis of a functionalized carbon supported platinum–iridium nanoparticle catalyst by the rapid chemical reduction method for the anodic reaction of direct methanol fuel cells

Direct methanol fuel cells (DMFCs) stand out among the most common technologies in energy storage and are environmentally friendly energy converters that convert chemical energy into electrical energy.

Formation and selected catalytic properties of ruthenium, rhodium, osmium and iridium nanoparticles

The synthesis and applications in catalysis of nanoparticles formed from ruthenium, rhodium, osmium and iridium have been reviewed.

Mesoporous Noble Metal-Metalloid/Nonmetal Alloy Nanomaterials: Designing Highly Efficient Catalysts

Mesoporous metals have received increasing attention in catalysis and related applications because of their novel physicochemical properties and functional geometric features. Control of multicomponent compositions and crystalline structures of mesoporous metals is critical for their applications. Recently, mesoporous metals have gradually expanded from traditional metal-metal alloys to metal-metalloid/nonmetal alloys with random solids and/or ordered intermetallics. As new, highly efficient nanocatalysts, mesoporous metal-metalloid/nonmetal alloys not only increase the utilization efficiency of precious noble metals and accelerate electron/mass transfer but also introduce new functions and optimize the surface electronic structure of metal sites, all of which enhance their catalytic activity and stability and tune their catalytic selectivity. In this Perspective, we focus on the latest developments in this area, including the findings from our group regarding the rational design and targeted synthesis of mesoporous noble metal-metalloid/nonmetal alloy nanocatalysts. We summarize the current synthetic strategies for mesoporous noble metal-metalloid/nonmetal alloys and discuss key effects of crystalline mesoporosity and metalloid/nonmetal alloys in enhancing catalytic performances of noble metal catalysts. We also describe the current bottlenecks and major challenges to explore further directions in synthesis and applications of mesoporous noble metal-metalloid/nonmetal alloys.

Application of Nanomaterials to Ensure Quality and Nutritional Safety of Food

Nanomaterials (NMs) are emerging novel tools for preserving quality, enhancing shelf life, and ensuring food safety. Owing to the distinctive physicochemical characters, engineered NMs under varying sizes and dimensions have great potentials for application in the manufacturing, packaging, processing, and safety of quality agrifood. The promise of various kinds of novel NMs that are useful for food industries has opened a possibility of a new revolution in agroprocessing industries in both the emerging and advanced nations. The rapid advancement of nanoscience has provided a great impact on material science that has allowed researchers to understand every aspect of molecular complexity and its functions in life sciences. The reduced size of NMs that increase the surface area is useful in the specific target of different organs, and biodegradable nanospheres are helpful in the transport of bioactive molecules across the cellular barriers. However, nanotechnology creates a great revolution in several sections including agriculture and food industry and also reduces environmental pollution, while the toxicity of some NMs in the food industry poses a great concern to researchers for their greater application. However, most of the developed countries have regulatory control acts but developing countries do not have them yet. Therefore, for the safe use of NMs and also to minimize the health and environmental risks in both the developed and developing countries, it is indispensable to recognize the toxicity-constructed, toxicodynamic, and toxicokinetic features of NMs, which should carefully be emphasized at the home and industrial levels. The current study highlights the updates of the NMs to safeguard the quality and nutritional safety of foods at home and also at the industrial level.

Prospects of Nanotechnology in Improving the Productivity and Quality of Horticultural Crops

Nanotechnology shows high promise in the improvement of agricultural productivity thus aiding future food security. In horticulture, maintaining quality as well as limiting the spoilage of harvested fruit and vegetables is a very challenging task. Various kinds of nanomaterials have shown high potential for increasing productivity, enhancing shelf-life, reducing post-harvest damage and improving the quality of horticultural crops. Antimicrobial nanomaterials as nanofilm on harvested products and/or on packaging materials are suitable for the storage and transportation of vegetables and fruits. Nanomaterials also increase the vitality of the cut flower. Nanofertilizers are target-specific, slow releasing and highly efficient in increasing vegetative growth, pollination and fertility in flowers, resulting in increased yield and improved product quality for fruit trees and vegetables. Formulated nanopesticides are target-specific, eco-friendly and highly efficient. Nanosensors facilitate up-to-date monitoring of growth, plant disease, and pest attack in crop plants under field conditions. These novel sensors are used to precisely identify the soil moisture, humidity, population of crop pests, pesticide residues and figure out nutrient requirements. This review aimed to provide an update on the recent advancement of nanomaterials and their potential uses for enhancing productivity, quality of products, protection from pests and reduction of the postharvest losses of the horticultural crops. This study reveals that nanotechnology could be used to generate cutting-edge techniques towards promoting productivity and quality of horticultural crops to ensure food and nutritional security of ever-increasing population of the world.

Sustained CO2-photoreduction activity and high selectivity over Mn, C-codoped ZnO core-triple shell hollow spheres

Solar conversion of CO₂ into energy-rich products is one of the sustainable solutions to lessen the global energy shortage and environmental crisis. Pitifully, it is still challenging to attain reliable and affordable CO₂ conversion. Herein, we demonstrate a facile one-pot approach to design core-triple shell Mn, C-codoped ZnO hollow spheres as efficient photocatalysts for CO₂ reduction. The Mn ions, with switchable valence states, function as “ionized cocatalyst” to promote the CO₂ adsorption and light harvesting of the system. Besides, they can capture photogenerated electrons from the conduction band of ZnO and provide the electrons for CO₂ reduction. This process is continuous due to the switchable valence states of Mn ions. Benefiting from such unique features, the prepared photocatalysts demonstrated fairly good CO₂ conversion performance. This work is endeavoured to shed light on the role of ionized cocatalyst towards sustainable energy production.

Photoreduction of CO₂ into energy-rich products is a sustainable solution to lessen the global energy and environmental crisis. Here the authors show that Mn ions in Mn, C-codoped ZnO hollow spheres function as “ionized cocatalyst” to promote the CO₂ adsorption and light harvesting to boost the CO₂ photoreduction activity.

Flexible nanocellulose-based SERS substrates for fast analysis of hazardous materials by spiral scanning

Surface-enhanced Raman scattering (SERS) has proven to be a valuable tool for assessing harmful chemicals in various substances, including water, soil, and foods. However, a fast measurement system is required for multiplexed detection to extend the range of its applications. The rotating scanning stage of the SERS substrate is considered to be a promising approach to achieving a fast measurement system. This paper reports a facile measurement system by using a flexible nanocellulose-based SERS substrate and a spiral scanning system, which rotates the cylinder sample holder and moves the stage. A flexible nanocellulose-based SERS substrate deposited with Au nanoparticles is suitable for the spiral scanning system, which requires SERS substrates to be highly flexible and durable. The well-known toxic fungicide, thiram, was tested by this system. The results revealed that the nanocellulose-based SERS substrate is well-fitted with a spiral scanning system and that the signal data from a large area substrate can be obtained within 30 s. It is noteworthy that the error of spiral scanning measurements is smaller than that of multi-spot sampling. This work provides a powerful tool for Raman spectroscopic analysis, which requires quantitative and fast testing. Furthermore, various flexible SERS substrates can be utilized in this system for toxic materials detection.