Nonsacrificial Self-Template Synthesis of Colloidal Magnetic Yolk-Shell Mesoporous Organosilicas for Efficient Oil/Water Interface Catalysis

Magnetic yolk-shell structured periodic mesoporous organosilica supported palladium as a powerful and highly recoverable nanocatalyst for the reduction of nitrobenzenes

A novel palladium-loaded yolk-shell structured nanomaterial with magnetite core and phenylene-based periodic mesoporous organosilica (PMO) shell (Fe3O4@YS-Ph-PMO/Pd) nanocatalyst was synthesized for the reduction of nitrobenzenes. The Fe3O4@YS-Ph-PMO/Pd was prepared through cetyltrimethylammonium bromide (CTAB) directed condensation of 1,4-bis(triethoxysilyl)benzene (BTEB) around Fe3O4@silica nanoparticles followed by treatment with palladium acetate. This nanocatalyst was characterized by using Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), low-angle and wide-angle powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analyses. These analyses showed a magnetic nanomaterial with high chemical and thermal stability for the designed composite. The Fe3O4@YS-Ph-PMO/Pd nanocomposite was employed as a powerful and highly recoverable catalyst in the green reduction of nitroarenes in H2O at room temperature. A variety of nitroarene derivatives were applied as substrate in the presence of 0.9 mol% of Fe3O4@YS-Ph-PMO/Pd catalyst. All nitroarenes were selectively converted to their corresponding amines with high to excellent yields (92-96%) within short reaction times (10-18 min). This catalyst was recovered and reused at least 11 times without significant decrease in efficiency and stability.

Current On-Skin Flexible Sensors, Materials, Manufacturing Approaches, and Study Trends for Health Monitoring: A Review

Due to an ever-increasing amount of the population focusing more on their personal health, thanks to rising living standards, there is a pressing need to improve personal healthcare devices. These devices presently require laborious, time-consuming, and convoluted procedures that heavily rely on cumbersome equipment, causing discomfort and pain for the patients during invasive methods such as sample-gathering, blood sampling, and other traditional benchtop techniques. The solution lies in the development of new flexible sensors with temperature, humidity, strain, pressure, and sweat detection and monitoring capabilities, mimicking some of the sensory capabilities of the skin. In this review, a comprehensive presentation of the themes regarding flexible sensors, chosen materials, manufacturing processes, and trends was made. It was concluded that carbon-based composite materials, along with graphene and its derivates, have garnered significant interest due to their electromechanical stability, extraordinary electrical conductivity, high specific surface area, variety, and relatively low cost.

Amine-containing yolk-shell structured magnetic organosilica nanocomposite as a highly efficient catalyst for the Knoevenagel reaction

The yolk-shell structured silica nanocomposites have been considered by many researchers due to their specific physical and chemical properties. These materials have been widely used in adsorption and catalysis processes. Especially, the void space of yolk-shell nanostructures can provide a unique environment for storage, compartmentation, and confinement in host-guest interactions. In this paper, for the first time, the preparation, characterization, and catalytic application of a novel amine-containing magnetic methylene-based periodic mesoporous organosilica with yolk-shell structure (YS-MPMO/pr-NH2) are developed. The magnetic periodic mesoporous organosilica nanocomposite was synthesized through surfactant-directed co-condensation of bis(triethoxysilyl)methane (BTEM) and tetraethoxysilane around Fe3O4 nanoparticles. After Soxhlet extraction, the surface of YS-MPMO nanocomposite was modified with 3-aminopropyl trimethoxysilane to deliver YS-MPMO-pr-NH2 nanocatalyst. This catalyst was characterized by using EDX, FT-IR, VSM, TGA, XRD, nitrogen-sorption, and SEM analyses. The catalytic activity of YS-MPMO/pr-NH2 was studied in the Knoevenagel reaction giving the corresponding products in a high yield and selectivity. The YS-MPMO/pr-NH2 nanocatalyst was recovered and reused at least four times without a significant decrease in efficiency and activity. A leaching test was performed to study the nature of the catalyst during reaction conditions Also, the catalytic performance of our designed nanocomposite was compared with some of the previous catalysts used in the Knoevenagel reaction.

Yolk-shell structured magnetic mesoporous organosilica supported ionic liquid/Cu complex: an efficient nanocatalyst for the green synthesis of pyranopyrazoles

The preparation of yolk-shell structured magnetic mesoporous composites is a significant subject between researchers. Especially, modification of theses composites with ionic liquid/metal complex is very important for catalytic processes. In the present study, a novel magnetic methylene-based periodic mesoporous organosilica (PMO)-supported ionic liquid/Cu complex with yolk-shell structure (YS-Fe3O4@PMO/IL-Cu) was prepared via the soft template-assisted method. The TGA, FT-IR, SEM, EDX, XRD, VSM, nitrogen-sorption, and ICP techniques were employed to identify YS-Fe3O4@PMO/IL-Cu. The YS-Fe3O4@PMO/IL-Cu material was applied as a powerful nanocatalyst for the synthesis of pyranopyrazoles under ultrasonic media. The study demonstrated that the YS-Fe3O4@PMO/IL-Cu nanocatalyst is highly recyclable, selective, and effective. The leaching test was performed to investigate the nature of the designed catalyst under the applied conditions.

Development of ZnO/SnO2/rGO hybrid nanocomposites for effective photocatalytic degradation of toxic dye pollutants from aquatic ecosystems

The impact of ZnO/SnO₂/reduced graphene oxide nanocomposites (ZnO/SnO₂/rGO NCs) for improved photocatalytic degradation of organic dye pollution is examined in this study. The developed ternary nanocomposites had a variety of characteristics that were detected, such as crystallinity, recombination of photogenerated charge carriers, energy gap, and surface morphologies. When rGO was added to the mixture, the optical band gap energy of ZnO/SnO₂ was lowered, which improved the photocatalytic activity. Additionally, in comparison to ZnO, ZnO/rGO, SnO₂/rGO samples, the ZnO/SnO₂/rGO nanocomposites demonstrated exceptional photocatalytic effectiveness for the destruction of orange II (99.8%) and reactive red 120 dye (97.02%), respectively after 120 min exposure to sunlight. The high electron transport properties of the rGO layers, which make it feasible to efficiently separate electron-hole pairs, are attributed to the enhanced photocatalytic activity of the ZnO/SnO₂/rGO nanocomposites. According to the results, synthesized ZnO/SnO₂/rGO nanocomposites are a cost-efficient option for removing dye pollutants from an aqueous ecosystem. Studies show that ZnO/SnO₂/rGO nanocomposites are effective photocatalysts and may one day serve as the ideal material to reduce water pollution.

Research progress of yolk-shell structured nanoparticles and their application in catalysis

Yolk-shell nanoparticles (YSNs) have attracted a broad interest in the field of catalysis due to their unique structure and properties. The hollow structure of YSNs brings high porosity and specific surface areas which is conducive to the catalytic reactions. The flexible tailorability and functionality of both the cores and shells allow a rational design of the catalyst and may have synergistic effect which will improve the catalytic performance. Herein, an overview of the research progress with respect to the synthesis and catalytic applications of YSNs is provided. The major strategies for the synthesis of YSNs are presented, including hard template method, soft template method, ship-in-a-bottle method, galvanic replacement method, Kirkendall diffusion method as well as the Ostwald ripening method. Moreover, we discuss in detail the recent progress of YSNs in catalytic applications including chemical catalysis, photocatalysis and electrocatalysis. Finally, the future research and development of YSNs are prospected.

A Magnetically Separable Pd Single-Atom Catalyst for Efficient Selective Hydrogenation of Phenylacetylene

Selective hydrogenation of alkynes to alkenes plays a crucial role in the synthesis of fine chemicals. However, how to achieve high selectivity and effective separation of the catalyst and substrate while obtaining high activity is the key for this reaction. In this work, a Pd single-atom catalyst is anchored to the shell of magnetic core-shell particles that consist of a Ni-nanoparticles core and a graphene sheets shell (Ni@G) for semi-hydrogenation of phenylacetylene, delivering 93% selectivity to styrene at full conversion with a robust turnover frequency of 7074 h^-1 under mild reaction conditions (303 K, 2 bar H₂ ). Moreover, the catalyst can be recovered promptly from the liquid phase due to its magnetic separability, which makes it present good stability for enduring five cycles. Experimental and theoretical investigations reveal that H₂ and substrates are activated by atomically dispersed Pd atoms and Ni@G hybrid support, respectively. The hydrogenation reaction occurs on the surface of Ni@G via hydrogen spillover from the metal to the support. Such a strategy opens an avenue for designing highly active, selective, and magnetically recyclable catalysts for selective hydrogenation in liquid reaction systems.

Construction of a hydrangea-like Bi2WO6/BiOCl composite as a high-performance photocatalyst

Bi2WO6 flower-like microspheres were acted as porous templates for depositing BiOCl to prepare a hydrangea-like Bi2WO6/BiOCl composite. The Bi2WO6/BiOCl heterojunction exhibits a high photocatalytic activity under visible light.

Interface Assembly to Magnetic Mesoporous Organosilica Microspheres with Tunable Surface Roughness as Advanced Catalyst Carriers and Adsorbents

Surface roughness endows microspheres with unique and useful features and properties like improved hydrophobicity, enhanced adhesion, improved stability at the oil-water interface, and superior cell uptake properties, thus expanding their applications. Core-shell magnetic mesoporous microspheres combine the advantages of magnetic particles and mesoporous materials and have exhibited wide applications in adsorption, catalysis, separation, and drug delivery. In this study, virus-like rough core-shell-shell-structured magnetic mesoporous organosilica (denoted as RMMOS) microspheres with controllable surface roughness were successfully obtained through electrostatic interaction-directed interface co-assembly. The obtained RMMOS microspheres possess uniform spherical morphology with tunable surface roughness, radially aligned pore channels with a diameter of 3.0 nm in the outer organosilica shell, high specific surface area (396 m²/g), large pore volume (0.66 cm³/g), high magnetization (35.1 emu/g), and superparamagnetic property. The RMMOS microspheres serve as desirable candidates to support Au nanoparticles (2.5 nm) and show superior catalytic activity and excellent stability in hydrogenation of 4-nitrophenol. In addition, the RMMOS microspheres modified with carboxylic groups further displayed promising performance in convenient adsorption removal of dyes in polluted water.

Integrated fast-mass transfer and high Ti-sites utilization into hybrid amphiphilic TS@PMO catalyst towards efficient solvent-free methyl oleate epoxidation

For solvent-free catalytic oxidations, low efficiency resulted from poor mass transfer and insufficient utilization of active centers remains a tough problem. Herein, we demonstrate a novel hybrid core-shell catalyst (TS@PMO) with an amphiphilic shell and a Ti-surface-enriched mesoporous TiO₂-SiO₂ (TS) core to address this challenge. Such TS@PMO realizes its amphiphilicity via an ex situ formed periodic mesoporous organosilica (PMO) shell. Simultaneously, by a unique etching effect induced by organic precursor growth on [SiO₄] tetrahedra in TS core, active Ti sites are facilely enriched in near-surface layer of core and extra mesoporous cavities are introduced for substrate reservation. When applied for solvent-free epoxidation of methyl oleate (MO) with H₂O₂, TS@PMO exhibits remarkably boosted catalytic activity (X = 90.2%) and epoxide selectivity (S = 70.2%), overwhelming the unmodified titanosilicate (X = 63.7%, S = 49.2%) and Ti-containing organosilica (X = 39.8%, S = 25.0%). Such result benefits from an evidently enhanced interphase mass transfer and sufficiently accessible active Ti sites in TS@PMO. On the one hand, amphiphilic PMO shell can efficiently collect hydrophobic substrate and H₂O₂, while abundant mesopores in the shell offer open-path for them to access active sites in the core; on the other hand, an increased framework Ti (IV) density and their surface-enrichment in TS core greatly improve the utilization of active Ti sites. This study effectively makes up for the deficiencies of slow mass transfer and insufficient utilization of conventional titanosilicates in biphasic reactions, which paves a new avenue to exploit other hybrid catalysts for high-efficiency solvent-free catalysis.

Structure Engineering of Yolk-Shell Magnetic Mesoporous Silica Microspheres with Broccoli-Like Morphology for Efficient Catalysis and Enhanced Cellular Uptake

Yolk-shell magnetic mesoporous microspheres exhibit potential applications in biomedicine, bioseparation, and catalysis. Most previous reports focus on establishing various interface assembly strategies to construct yolk-shell mesoporous structures, while little work has been done to control their surface topology and study their relevant applications. Herein, a unique kind of broccoli-like yolk-shell magnetic mesoporous silica (YS-BMM) microsphere is fabricated through a surfactant-free kinetic controlled interface assembly strategy. The obtained YS-BMM microspheres possess a well-defined structure consisting of a magnetic core, middle void, mesoporous silica shell with tunable surface roughness, large superparamagnetism (36.4 emu g^-1 ), high specific surface area (174 m² g^-1 ), and large mesopores of 10.9 nm. Thanks to these merits and properties, the YS-BMM microspheres are demonstrated to be an ideal support for immobilization of ultrafine Pt nanoparticles (≈3.7 nm) and serve as superior nanocatalysts for hydrogenation of 4-nitrophenol with yield of over 90% and good magnetic recyclability. Furthermore, YS-BMM microspheres show excellent biocompatibility and can be easily phagocytosed by osteoclasts, revealing a potential candidate in sustained drug release in orthopedic disease therapy.

Tailored Mesoporous Inorganic Biomaterials: Assembly, Functionalization, and Drug Delivery Engineering

Infectious or immune diseases have caused serious threat to human health due to their complexity and specificity, and emerging drug delivery systems (DDSs) have evolved into the most promising therapeutic strategy for drug-targeted therapy. Various mesoporous biomaterials are exploited and applied as efficient nanocarriers to loading drugs by virtue of their large surface area, high porosity, and prominent biocompatibility. Nanosized mesoporous nanocarriers show great potential in biomedical research, and it has become the research hotspot in the interdisciplinary field. Herein, recent progress and assembly mechanisms on mesoporous inorganic biomaterials (e.g., silica, carbon, metal oxide) are summarized systematically, and typical functionalization methods (i.e., hybridization, polymerization, and doping) for nanocarriers are also discussed in depth. Particularly, structure-activity relationship and the effect of physicochemical parameters of mesoporous biomaterials, including morphologies (e.g., hollow, core-shell), pore textures (e.g., pore size, pore volume), and surface features (e.g., roughness and hydrophilic/hydrophobic) in DDS application are overviewed and elucidated in detail. As one of the important development directions, advanced stimuli-responsive DDSs (e.g., pH, temperature, redox, ultrasound, light, magnetic field) are highlighted. Finally, the prospect of mesoporous biomaterials in disease therapeutics is stated, and it will open a new spring for the development of mesoporous nanocarriers.

A Mini Review on Yolk-Shell Structured Nanocatalysts

Yolk-shell structured nanomaterials, possessing a hollow shell and interior core, are emerging as unique nanomaterials with applications ranging from material science, biology, and chemistry. In particular, the scaffold yolk-shell structure shows great promise as a nanocatalyst. Specifically, the hollow shell offers a confined space, which keeps the active yolk from aggregation and deactivation. The inner void ensures the pathway for mass transfer. Over the last few decades, many strategies have been developed to endow yolk-shell based nanomaterials with superior catalytic performance. This minireview describes synthetic methods for the preparation of various yolk-shell nanomaterials. It discusses strategies to improve the performance of yolk-shell catalysts with examples for engineering the shell, yolk, void, and related synergistic effects. Finally, it considers the challenges and prospects for yolk-shell nanocatalysts.

Surface engineering of magnetic iron oxide nanoparticles by polymer grafting: synthesis progress and biomedical applications

Magnetic iron oxide nanoparticles (IONPs) have wide applications in magnetic resonance imaging (MRI), biomedicine, drug delivery, hyperthermia therapy, catalysis, magnetic separation, and others. However, these applications are usually limited by irreversible agglomeration of IONPs in aqueous media because of their dipole-dipole interactions, and their poor stability. A protecting polymeric shell provides IONPs with not only enhanced long-term stability, but also the functionality of polymer shells. Therefore, polymer-grafted IONPs have recently attracted much attention of scientists. In this tutorial review, we will present the current strategies for grafting polymers onto the surface of IONPs, basically including "grafting from" and "grafting to" methods. Available functional groups and chemical reactions, which could be employed to bind polymers onto the IONP surface, are comprehensively summarized. Moreover, the applications of polymer-grafted IONPs will be briefly discussed. Finally, future challenges and perspectives in the synthesis and application of polymer-grafted IONPs will also be discussed.

Synthesis of Methyl-Capped TiO2-SiO2 Janus Pickering Emulsifiers for Selective Photodegradation of Water-Soluble Dyes

Recently, Pickering emulsion stabilized by Janus particles has received considerable attention for interfacial reactions and droplet manipulation. However, its potential interests have been rarely explored because of the difficulties in designing and fabricating Janus particles for Pickering emulsion with suitable applications. Also, photocatalytic materials are scarcely applied as emulsifiers in Pickering emulsions because of their photogenerated hydrophilicity. This work reports the synthesis of methyl-capped Janus TiO₂-SiO₂ particles (MJTSs), which can be used as a novel emulsifier and photocatalyst simultaneously. The MJTSs, composed of an anatase TiO₂ sphere and silica rod, are prepared by inverse emulsion-based step-by-step growth. We demonstrate that the Pickering emulsion stabilized by MJTSs represents extraordinary ability of emulsification, excellent stability, and tunable emulsion type (water in oil or oil in water). In addition, the MJTSs exhibit photocatalytic activity in decomposition of pollutants in the water phase while maintaining the stability of the Pickering emulsion.

Au-Fe3O4 decorated polydopamine hollow nanoparticles as high performance catalysts with magnetic responsive properties

We demonstrated a simple approach for fabricating Au-Fe₃O₄/PDA hollow nanoparticles as high-performance catalysts for water purification. The polydopamine (PDA) shell was in situ formed on the silica surface from self-polymerization, which acts as a medium support for coupling with metal ions (for Fe₃O₄ nanoparticle deposition) as well as a reducing agent and stabilizer for Au nanoparticle reduction and deposition. A step of simultaneous Fe₃O₄ nanoparticle deposition and silica core removal under alkaline conditions is first introduced in this study. This process significantly simplifies previous strategies which typically require the use of poisonous agents such as hydrogen fluoride or additional complicated post-treatment steps. Under optimized conditions, the Au-Fe₃O₄/PDA hollow nanoparticles show a high saturation magnetization of 18.8 emu g^-1 and an excellent catalytic performance for the rapid reduction of p-nitrophenol with the reaction kinetic constant of 0.34 min^-1. This catalyst can be easily recovered using a permanent magnet and recycled eight times with a high catalytic cycle stability. The strategy presented in this work provides a facile and versatile approach towards designing complicated Au-Fe₃O₄/PDA hollow nanostructures, which might have great potential for many applications within biological, energy, and environmental technologies.

Rational design of yolk–shell nanostructures for drug delivery

The recent progress in yolk–shell nanoparticles (YSNPs) as a new class of hollow nanostructures applied for drug delivery.