Formation of Fe3O4@C/Ni microtubes for efficient catalysis and protein adsorption

Construction of COFs@MoS2-Pd Hierarchical Tubular Heterostructures for Enhanced Catalytic Performance

Here, we report ternary COFs@MoS2-Pd hybrids with an innovative self-sacrificial approach. MoO3@Covalent organic frameworks (COFs) microcables were first prepared and then two-dimensional MoS2 nanosheets (NSs) were integrated onto the surface of COFs, as COFs@MoS2, after treatment with hydrothermal reaction. The MoS2 NSs were used as an excellent support to introduce Pd nanoparticles (NPs) thanks to their reducing ability for the formation of the ternary COFs@MoS2-Pd hybrids. While COF microtubes improved the electrical conductivity of the hybrid materials, they also decreased the aggregation of MoS2 NSs, as a contribution to the enhanced catalytic performance. The mild reaction between MoS2 and Pd2+ ions realized the dense distribution of Pd NPs onto COFs@MoS2 for abundant active sites to further improve the catalytic performance. Thus, the hierarchical MoS2-based ternary hybrids were prepared with the enhanced catalytical performance as validated with the enzyme-like catalysis and the reduction of 4-nitrophenol.

Construction of hierarchical NCMTs@MoO2/FeNi3 tubular heterostructures for enhanced performance in catalysis and protein adsorption

A new type of hybrid material (NCMTs@MoO2/FeNi3) with a multi-layer heterostructure was designed and fabricated via a one-step pyrolysis process using FeOOH/NiMoO4@PDA as the precursor. FeOOH/NiMoO4@PDA was prepared by the solvothermal method, followed by the nickel-ion etching method coupled with the polymerization of dopamine (DA). The as-obtained material was made of nitrogen-doped carbon nanotubes embedded with FeNi3 and MoO2 nanoparticles (NPs). Notably, the FeNi3 NPs exhibited significantly improved performance in the reduction of 4-nitrophenol (4-NP) and adsorption of histidine-rich protein as well as provided appropriate magnetism resources. The MoO2 NPs imparted a metallic nature with excellent conductivity, and the N-doped mesoporous carbon microtubes also improved conductivity and facilitated mass transfer, thus leading to enhanced performance in catalysis. Benefiting from the 1D hierarchical porous structure and compositional features, the NCMTs@MoO2/FeNi3 composites exhibited excellent performance in 4-NP reduction and protein adsorption via specific metal affinity between the polyhistidine groups of proteins and the FeNi3 NPs. The result presented here indicates that the strategy of combining tailored components, heterostructuring, and carbon integration is a promising way to obtain high-performance composites for other energy-related applications.

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.

Interfacing Ag2S Nanoparticles and MoS2 Nanosheets on Polypyrrole Nanotubes with Enhanced Catalytic Performance

The tubular architecture with multiple components can bring synergistic effects to improve the enzyme-like activity of molybdenum-based nanomaterials. Here, a facile polypyrrole (PPy)-protected hydrothermal sulfidation process was implemented to engineer MoS2/Ag2S heterointerfaces encapsulated in one-dimensional (1D) PPy nanotubes with MoO3@Ag nanorods as the self-sacrificing precursor. Notably, the sulfidation treatment led to the generation of MoS2 nanosheets (NSs) and Ag2S nanoparticles (NPs) and the creation of a tubular structure with a "kill three birds with one stone" role. The Ag2S/MoS2@PPy nanotubes showed the synergistic combined effects of Ag2S NPs, MoS2 NSs, and the 1D tube-like nanostructure. Based on the synergistic effects from these multiple components and the tubular structure, Ag2S/MoS2@PPy nanocomposites were used as a colorimetric sensing platform for detecting H2O2. Moreover, the reduction of 4-nitrophenol (4-NP) revealed excellent catalytic activity in the presence of NaBH4 and Ag2S/MoS2@PPy nanocomposites. This work highlights the effects of MoS2/Ag2S heterointerfaces and the hierarchical tubular structure in catalysis, thereby providing a new avenue for reducing 4-NP and the enzyme-like catalytic field.

Multifunctional Hollow Porous Fe3O4@N-C Nanocomposites as Anodes of Lithium-Ion Battery, Adsorbents and Surface-Enhanced Raman Scattering Substrates

At present, it is still a challenge to prepare multifunctional composite nanomaterials with simple composition and favorable structure. Here, multifunctional Fe₃O₄@nitrogen-doped carbon (N-C) nanocomposites with hollow porous core-shell structure and significant electrochemical, adsorption and sensing performances were successfully synthesized through the hydrothermal method, polymer coating, then thermal annealing process in nitrogen (N₂) and lastly etching in hydrochloric acid (HCl). The morphologies and properties of the as-obtained Fe₃O₄@N-C nanocomposites were markedly affected by the etching time of HCl. When the Fe₃O₄@N-C nanocomposites after etching for 30 min (Fe₃O₄@N-C-3) were applied as the anodes for lithium-ion batteries (LIBs), the invertible capacity could reach 1772 mA h g^-1 after 100 cycles at the current density of 0.2 A g^-1, which is much better than that of Fe₃O₄@N-C nanocomposites etched, respectively, for 15 min and 45 min (948 mA h g^-1 and 1127 mA h g^-1). Additionally, the hollow porous Fe₃O₄@N-C-3 nanocomposites also exhibited superior rate capacity (950 mA h g^-1 at 0.6 A g^-1). The excellent electrochemical properties of Fe₃O₄@N-C nanocomposites are attributed to their distinctive hollow porous core-shell structure and appropriate N-doped carbon coating, which could provide high-efficiency transmission channels for ions/electrons, improve the structural stability and accommodate the volume variation in the repeated Li insertion/extraction procedure. In addition, the Fe₃O₄@N-C nanocomposites etched by HCl for different lengths of time, especially Fe₃O₄@N-C-3 nanocomposites, also show good performance as adsorbents for the removal of the organic dye (methyl orange, MO) and surface-enhanced Raman scattering (SERS) substrates for the determination of a pesticide (thiram). This work provides reference for the design and preparation of multifunctional materials with peculiar pore structure and uncomplicated composition.

Magnetic Dendritic Polymer Nanospheres for High-Performance Separation of Histidine-Rich Proteins

Magnetic nanospheres are becoming a promising platform for a wide range of applications in pharmacy, life science, and immunodiagnostics due to their high surface area, ease of synthesis and manipulation, fast separation, good biocompatibility, and recyclable performance. In this work, an innovative and efficient method is developed by in situ reducing and growing Ni(OH)₂ for the preparation of dendritic mesoporous nanocomposites of silica@Fe₃O₄/tannic acid@nickel hydroxide (dSiO₂@Fe₃O₄/TA@Ni(OH)₂). The flower-like nanospheres have good magnetic response, large surface area, and high histidine-rich protein (His-protein) purification performance. The dSiO₂@Fe₃O₄/TA@Ni(OH)₂ nanospheres were synthesized on the basis of a φ(NaSal/CTAB) of 1/1 and a mass of ferrous chloride tetrahydrate of 0.3 g, resulting in a saturation magnetization value of 48.21 emu/g, which means it can be collected within ∼1 min using a magnetic stand. Also, the BET test showed that the surface area is 92.47 m²/g and the pore size is ∼3.9 nm for dSiO₂@Fe₃O₄/TA@Ni(OH)₂ nanocomposites. Notably, the nickel hydroxide with unique flower-like structural features enables the combination of a large number of Ni²⁺ ions and His-proteins for high performance. The isolation and purification experiments of the synthesized dSiO₂@Fe₃O₄/TA@Ni(OH)₂ were performed by separating His-proteins from a matrix composed of bovine hemoglobin (BHb), bovine serum albumin (BSA), and lysozyme (LYZ). The result showed that the nanospheres have a high combination capacity of ∼1880 mg/g in a rapid equilibrium time of 20 min, which was selective for the adsorption of BHb. In addition, the stability and recyclability of BHb are 80% after seven cycles. Furthermore, the nanospheres were also used to isolate His-proteins from fetal bovine serum, proving its utility. Therefore, the strategy of separating and purifying His-proteins using dSiO₂@Fe₃O₄/TA@Ni(OH)₂ nanospheres is promising for practical applications.

Stöber method and its nuances over the years

Some characteristics of silica-based materials, such as the control/adjustment of their physical and chemical properties, compatibility, and friendly-use synthesis methods, have held the attention of several scientific groups over the years. This condition of prominence becomes even more evident when we seek these characteristics at the micro- and/or nanoscale. Among existing methods to obtain these micro/nanomaterials, the Stöber method is the focus of this review. This method is known to enable the production of silica micro- or nanoparticles from reagents of medium-easy manipulation under mild conditions using equipment that is common in most laboratories. However, this method has many nuances that must be considered to guarantee accurate results, either in size or distribution, and to ensure result reproducibility. Thus, in this review, we discuss the effects of the primary components used in the synthesis of these materials (i.e., TEOS, ammonia, and water), as well as those of other reaction conditions, such as solvent, temperature, and ionic strength. Therefore, we discuss studies involving the synthesis and characterization of micro- and nanoparticles over the years to establish discussions between their experimental observations and proposed models. This review provides experimental observations about the synthesis of these materials, as well as discussions according to complementary and/or contradictory evidence found over the years. This review seeks to help those who intend to work with this method and provide certain key points that, in our experience, can be important to obtain desired results.

Hierarchical microtubes constructed using Fe-doped MoS2 nanosheets for biosensing applications

The structural design of multiple functional components could enhance the synergistic catalytic performance of MoS₂-based composites in enzyme-like catalysis. Herein, one-dimensional (1D) Fe-MoS₂ microtubes were designed to prepare tubular Fe-doped MoS₂ composites with MoO₃ microrods as self-sacrificing precursors. Remarkably, the results indicated that the generated ammonia released from the sulfidation process led to the dissolution of MoO₃ cores and the generation of a tubular structure. The Fe-MoS₂ composites integrated the synergistic effects of Fe-doped MoS₂ nanosheets (NSs) and the 1D tubular structure. Thus, a higher catalytic activity was observed in peroxidase-like catalysis than in other components, such as MoO₃@FeOOH, FeOOH and MoS₂ NSs. The peroxidase-like mechanism originated from the generation of the ˙OH radical. The Fe-MoS₂ microtube-based colorimetric assay was used to detect H₂O₂ with a detection limit (LOD) of 0.51 μM in a linear range from 1.25 to 50 μM. The colorimetric method was simple, selective, and sensitive for glutathione (GSH) detection in the range of 0.25-125 μM with a detection limit (LOD) of 0.12 μM. Thus, we provide a facile synthetic strategy for simultaneously integrating electronic modulation and structural design to develop an efficient MoS₂-based functional catalyst.

Enhanced reduction of nitrobenzene derivatives using reusable Ni nanoparticles supported on multi-layered poly(1,2-phenylenediamine)-coated layered double hydroxides

Recently, nanomaterials with layered double hydroxide (LDH) cores have been the subject of intense research regarding their promising applications in organic synthesis. In this study, nitrobenzene reduction is investigated by designing and synthesizing a novel LDH-based heterogeneous catalyst containing a nickel-1,2-phenylenediamine complex. The Cu–Zn–Al LDH was functionalized with copolymer bearing a glycidyl methacrylate (GMA) linkage that makes it suitable for grafting with 1,2-phenylenediamine. Overall, the synthesized LDH@MPS-GMA-PDA-Ni was found to be a highly efficient heterogeneous nanocatalyst that can catalyze nitroarene reduction with high yields under mild conditions.

Rational design, synthesis, and applications of carbon-assisted dispersive Ni-based composites

Herein, we review recent developments in the rational design and engineering of various carbon-assisted dispersive nickel-based composites, and boosted properties for protein adsorption and nitroaromatics reduction.

In Situ Construction of Co-MoS2/Pd Nanosheets on Polypyrrole-Derived Nitrogen-Doped Carbon Microtubes as Multifunctional Catalysts with Enhanced Catalytic Performance

The structural design of multiple functional components could integrate synergistic effects to enhance the catalytic performance of MoS₂-based composites for catalytic applications. Herein, one-dimensional (1D) Co-MoS₂/Pd@NCMTs composites were designed to prepare Co-doped MoS₂/Pd nanosheets (NSs) on N-doped carbon microtubes (NCMTs) from tubular polypyrrole (PPy) as multifunctional catalysts. The Co-MoS₂/Pd@NCMTs composites integrated the synergistic effects of Co-doping, a 1D tubular structure, and noble-metal Pd decoration. Thus, a higher catalytic activity was observed in 4-nitrophenol (4-NP) reduction and peroxidase-like catalysis than other components, such as MoS₂, MoS₂@NCMTs, and Co-MoS₂@NCMTs. Remarkably, the results indicated that the dissolution, diffusion, and redistribution led to the dissolution of MoO₃@ZIF-67 cores and generation of Co-doped MoS₂ NSs. Benefiting from the synergistic effect from these components, Co-MoS₂/Pd@NCMTs were considered as a facile colorimetric sensing platform for detecting tannic acid. Moreover, outstanding performance was realized in the reduction of 4-NP with the composites. Thus, we provide a simple synthetic strategy for simultaneously integrating electronic engineering and structural advantages to develop an efficient MoS₂-based multifunctional catalyst.

Fabrication of Yolk-Shell Fe3O4@NiSiO3/Ni Microspheres for Efficient Purification of Histidine-Rich Proteins

Magnetic materials perform well in the purification of histidine-rich proteins (His-proteins). In this work, a facile fabrication of yolk-shell magnetic Fe₃O₄@NiSiO₃/Ni microspheres for the efficient purification of His-proteins has been reported. Yolk-shell Fe₃O₄@NiSiO₃ microspheres were prepared via hydrothermal reaction. Then Ni nanoparticles (NPs) were loaded on Fe₃O₄@NiSiO₃ microspheres after the adsorption and in situ reduction of nickel acetylacetonate. The yolk-shell Fe₃O₄@NiSiO₃/Ni microspheres had a hierarchical flower-like structure and large cavities. The size of the cavity depended on the reaction time. This indicated that the microspheres had a large specific surface area for loading of more Ni NPs, which was crucial to the high His-protein adsorption capacity of Fe₃O₄@NiSiO₃/Ni microspheres. Fe₃O₄@NiSiO₃/Ni microspheres had a high adsorption capacity for bovine hemoglobin (BHb, 2822 mg/g), which was better than the values of other His-protein adsorbents. Fe₃O₄@NiSiO₃/Ni microspheres still had a high BHb separation efficiency after seven separation cycles, indicating its good reusability and stability. Therefore, the as-prepared bifunctional yolk-shell Fe₃O₄@NiSiO₃/Ni microspheres exhibited great practical application value for His-protein purification.

Keratin-inorganic hybrid nanoflowers decorated with Fe3O4 nanoparticles as enzyme mimics for colorimetric detection of glucose

Fe3O4 magnetic nanoparticles (MNPs) are highly active enzyme-like catalysts. However, low stability is still a big challenge for Fe3O4-based enzyme mimics because the Fe3O4 MNPs can be easily dissolved when exposed to acidic conditions. Inspired by the numerous catalytic sites of a flower-like structure and the biological functions of amino acids in structural proteins, herein, by employing keratin as a protein component, stable Fe3O4-based MNP embedded keratin-Cu3(PO4)2 nanoflowers were constructed, from which hierarchical nanostructures with a three-dimensional petal-like morphology were selected for subsequent studies owing to their excellent enzymic catalytic activity. The keratin-nanoflower@Fe3O4 exhibited significantly enhanced catalytic activity compared with that of keratin-Cu3(PO4)2 nanoflowers and individual Fe3O4 MNPs. Remarkably, keratin-nanoflower@Fe3O4 exhibited superior long-term stability to Fe3O4 MNPs under more acidic conditions and favorable reusability. This method has been successfully exploited for the colorimetric determination of glucose in human serum with satisfactory sensitivity and specificity, offering a novel approach for glucose detection.

Preparation of Fe3O4@PMAA@Ni Microspheres towards the Efficient and Selective Enrichment of Histidine-Rich Proteins

Magnetic material is considered to as a major concern material for the enrichment of histidine-rich proteins (His-proteins) via metal-ion affinity. In this work, magnetic polymer microspheres with core-shell structure (Fe₃O₄@PMAA@Ni) were successfully prepared via reflux-precipitation polymerization followed by in situ reduction and growth of Ni²⁺. The obtained Ni nanofoams with flower-like structure and uniform pore size (3.34 nm) provided numerous binding sites for His-proteins. The adsorption performance of Fe₃O₄@PMAA@Ni microspheres for His-proteins was estimated via selectively separating bovine hemoglobin (BHb) and bovine serum albumin (BSA) from a matrix composed of BHb, BSA, and lysozyme (LYZ). The results indicated that Fe₃O₄@PMAA@Ni microspheres could efficiently and selectively separate His-proteins from the matrix, with a maximum adsorption capacity of ∼2660 mg/g for BHb. Moreover, Fe₃O₄@PMAA@Ni microspheres exhibited good stability and recyclability for BHb separation over seven cycles. Therefore, this work reported a novel and facile strategy to prepare core-shell Fe₃O₄@PMAA@Ni microspheres, which was promising for practical applications of His-protein separation and purification in proteomics.

A facile template method to fabricate one-dimensional Fe3O4@SiO2@C/Ni microtubes with efficient catalytic and adsorption performance

The Fe3O4@SiO2@C/Ni microtubes were well constructed with MoO3 microrods as sacrificing template, which manifested excellent performance as both catalyst and adsorbent.

A facile synthesis of one-dimensional hierarchical magnetic metal silicate microtubes with enhanced adsorption performance

One-dimensional (1D) hierarchical magnetic hollow micro/nanotubes have attracted special attention in the field of adsorption owing to their high surface area, easy separation and short mass diffusion. Here, we report a facile approach for synthesizing one-dimensional hierarchical magnetic metal silicate microtubes through an extended Stöber method, carbonization treatment and subsequent hydrothermal reaction with metal ions in an alkaline solution. The unique 1D hierarchical magnetic microtubes have a large surface area, good structural stability and high magnetic response. Benefiting from these advantages, the resultant microtubes display excellent performance as good adsorbents for bovine hemoglobin (BHb) and methylene blue (MB). Furthermore, this strategy can also be applied to prepare other 1D hierarchical magnetic metal silicate composites.

A facile template method to fabricate strongly coupled 1D sandwich-like C@Fe3O4@C/Ni coaxial microtubes with enhanced catalytic performance

Sandwich-like C@Fe₃O₄@C/Ni microtubes were well-constructed with MoO₃ microrods as a hard template, which manifested excellent catalytic performance and recycling ability in the reduction of 4-nitrophenol.

Space-confined pyrolysis for fabrication of peacods-like Fe3O4@C-Ni nanostructures for catalysis and protein adsorption

A unique nanostructure of Fe₃O₄ nanoparticles (NPs)-in/carbon layer/out-Ni NPs was developed and proved to be an efficient catalyst and protein adsorbent. This kind of nanostructure was formed through a space-confined pyrolysis procedure using polydopamine-Ni²⁺ coated Fe-NTA nanowires as the precursor. A N-doped carbon interlayer derived from polydopamine (PDA) supported a large amount of Ni NPs and entrapped well-defined Fe₃O₄ NPs, which were obtained through reduction of Ni²⁺, Fe³⁺ by carbonized NTA groups and a PDA layer. The contributions of the unique configuration along with the high density of Ni NPs in Fe₃O₄@C-Ni are significant for improving catalysis and protein adsorption performance, which is expected to be a promising alternative to other conventional catalysts and protein adsorbents. Due to the unique novel nanostructure, this nanocomposite possesses a wide range of applications, not only for catalytic reactions but also for other inhomogeneous reactions.

Adsorption behaviour and mechanism of the PFOS substitute OBS (sodium p-perfluorous nonenoxybenzene sulfonate) on activated carbon

Perfluorooctane sulfonate (PFOS) was listed as a persistent organic pollutant by the Stockholm Convention. As a typical alternative to PFOS, sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has recently been detected in the aquatic environment which has caused great concern. For the first time, the adsorption behaviour and mechanism of OBS on activated carbon (AC) with different physical and chemical properties were investigated. Decreasing the particle size of AC can accelerate its adsorption for OBS, while AC with too small particle size was not conducive to its adsorption capacity due to the destruction of its pore structure during the mechanical crushing process. Intra-particle diffusion had a lesser effect on the adsorption rate of AC with smaller particle size, higher hydrophilicity and larger pore size. Reactivation of AC by KOH can greatly enlarge their pore size and surface area, greatly increasing their adsorption capacities. The adsorption capacity of two kinds of R-GAC exceeded 0.35 mmol g^-1, significantly higher than that of other ACs. However, increasing the hydrophilicity of AC would decrease their adsorption capacities. Further investigation indicated that a larger pore size and smaller particle size can greatly enhance the adsorptive removal of OBS on AC in systems with other coexisting PFASs and organic matter due to the reduction of the pore-blocking effect. The spent AC can be successfully regenerated by methanol, and it can be partly regenerated by hot water and NaOH solution. The percentage of regeneration for the spent AC was 70.4% with 90°C water temperature and up to 95% when 5% NaOH was added into the regeneration solution. These findings are very important for developing efficient adsorbents for the removal of these newly emerging PFASs from wastewater and understanding their interfacial behaviour.

Facile preparation of amidoxime-functionalized Fe3O4@SiO2-g-PAMAM-AO magnetic composites for enhanced adsorption of Pb(ii) and Ni(ii) from aqueous solution

In this paper, using amidoxime as a functional monomer, different generations of polyamidoxime dendrimer magnetic microspheres (Fe₃O₄@SiO₂-g-PAMAM-AO) were fabricated to adsorb Pb²⁺ and Ni²⁺ in aqueous solution. The magnetic adsorbents were characterized by FTIR, XRD, SEM, XPS, TEM, EDS, TGA and BET. The effects of different factors (such as solution pH, adsorption time, adsorption temperature, adsorbent dosage etc.) on adsorption were evaluated. Fe₃O₄@SiO₂-g-PAMAM-AO has a maximum Pb(ii) adsorption of 157.25 mg g⁻¹ (100 mg L⁻¹) at pH 5.5. Furthermore, Fe₃O₄@SiO₂-g-PAMAM-AO showed an excellent adsorption performance for the removal of Ni(ii) with a maximum adsorption capacity of 191.78 mg g⁻¹ (100 mg L⁻¹) at pH 8.0. The sorption isotherm data fitted the Freundlich isotherm model well. Adsorption kinetics analysis showed that it was best described by the pseudo-second-order rate model. Desorption experiment results showed that the adsorbent can be reused in the adsorption–desorption cycles.

In this paper, using amidoxime as a functional monomer, different generations of polyamidoxime dendrimer magnetic microspheres (Fe₃O₄@SiO₂-g-PAMAM-AO) were fabricated to adsorb Pb²⁺ and Ni²⁺ in aqueous solution.

One dimensional hierarchical nanoflakes with nickel-immobilization for high performance catalysis and histidine-rich protein adsorption

Herein, we described a facile strategy for the controllable synthesis of three dimensional hierarchical nickel based composites, which exhibited excellent performance on catalysis and protein adsorption.

Rationally designed hierarchical nickel nanoparticles-based magnetic yolk-like nanospindles for enhanced catalysis and protein adsorption

Herein, we demonstrate a mild route to construct spindle-like hybrid composites (FeO_x@SiO₂@C–Ni) that integrate the magnetic cores with high density metallic nickel NPs in yolk–shell structures, which exhibited excellent performance in catalysis and protein adsorption.