η-Carbides (Co, Mo, or W) Nanoparticles from Octacyanometalates Precursors-Based Network

This paper describes a simple, two-steps chemical pathway to obtain bimetallic carbide nanoparticles (NPs) of general formula MxM″yC, also called η-carbides. This process allows for a control of the chemical composition of metals present in the carbides (M = Co and M″ = Mo or W). The first step involves the synthesis of a precursor consisting of a network of octacyanometalates. The second step consists in a thermal degradation of the previously obtained octacyanometalates networks under neutral atmosphere (Ar or N2 ). It is shown that this process results in the formation of carbide NPs with diameter of ≈ 5nm, and the stoichiometries Co3 M'3 C, Co6 M'6 C, Co2 M'4 C for the CsCoM' systems.

Silver thiolate nanoclusters as support for chiral ligands: application in heterogeneous phase asymmetric catalysis

Silver thiolate nanoclusters have been functionalized with a chiral amino alcohol ligand that has previously shown high catalytic efficiency in different asymmetric reactions. The as-developed nanostructured catalyst, which can be easily recovered by simple centrifugation, has been tested in the addition of nitromethane to aromatic aldehydes, showing the same catalytic activity as the homogeneous ligand. Moreover, it was reused for two further recycling cycles without loss of efficiency. To the best of our knowledge, this is the first example of silver nanoclusters employed as a support for chiral ligands for heterogeneous phase asymmetric catalysis.

Fe3O4/SiO2 decorated trimesic acid-melamine nanocomposite: a reusable supramolecular organocatalyst for efficient multicomponent synthesis of imidazole derivatives

This article describes supramolecular Fe₃O₄/SiO₂ decorated trimesic acid-melamine (Fe₃O₄/SiO₂-TMA-Me) nanocomposite that can be prepared with features that combine properties of different materials to fabricate a structurally unique hybrid material. In particular, we have focused on design, synthesis and evaluation a heterogeneous magnetic organocatalyst containing acidic functional-groups for the synthesis of biologically important imidazole derivatives in good to excellent yields. The introduced Fe₃O₄/SiO₂-TMA-Me nanomaterial was characterized by different techniques such as FTIR, XRD, EDX, FESEM, TEM, TGA and DTA. As a noteworthy point, the magnetic catalytic system can be recycled and reused for more than seven consecutive runs while its high catalytic activity remains under the optimized conditions.

Facile synthesis of polyoxometalate supported on magnetic graphene oxide as a hybrid catalyst for efficient oxidation of aldehydes

In the present study, Anderson-type polyoxometalate [N(C₄H₉)₄] [FeMo₆O₁₈(OH)₆] (FeMo₆) was immobilized on amino-modified magnetic graphene oxide and employed as a new hybrid catalyst in oxidation of aldehydes to carboxylic acids. The synthesized hybrid catalyst Fe₃O₄/GO/[FeMo₆] was characterized using thermogravimetric analysis (TGA), scanning electron microscopies (SEM), Fourier transform infrared (FT-IR), vibrating sample magnetometry (VSM), energy-dispersive X-ray analysis (EDX), Raman spectroscopy and inductively coupled plasma atomic emission spectroscopy (ICP-OES). The results indicated that our catalyst was quite active in oxidizing the aldehydes to their corresponding carboxylic acids in the presence of hydrogen peroxide. The synthesized catalyst can be easily separated from the reaction medium and reused for six consecutive runs without a significant reduction in reaction efficiency.

Application of fungal copper carbonate nanoparticles as environmental catalysts: organic dye degradation and chromate removal

Biomineralization is a ubiquitous process in organisms to produce biominerals, and a wide range of metallic nanoscale minerals can be produced as a consequence of the interactions of micro-organisms with metals and minerals. Copper-bearing nanoparticles produced by biomineralization mechanisms have a variety of applications due to their remarkable catalytic efficiency, antibacterial properties and low production cost. In this study, we demonstrate the biotechnological potential of copper carbonate nanoparticles (CuNPs) synthesized using a carbonate-enriched biomass-free ureolytic fungal spent culture supernatant. The efficiency of the CuNPs in pollutant remediation was investigated using a dye (methyl red) and a toxic metal oxyanion, chromate Cr(VI). The biogenic CuNPs exhibited excellent catalytic properties in a Fenton-like reaction to degrade methyl red, and efficiently removed Cr(VI) from solution due to both adsorption and reduction of Cr(VI). X-ray photoelectron spectroscopy (XPS) identified the oxidation of reducing Cu species of the CuNPs during the reaction with Cr(VI). This work shows that urease-positive fungi can play an important role not only in the biorecovery of metals through the production of insoluble nanoscale carbonates, but also provides novel and simple strategies for the preparation of sustainable nanomineral products with catalytic properties applicable to the bioremediation of organic and metallic pollutants, solely and in mixtures.

Highly Stable Univalent Copper of a Cu@Al/SBA-15 Nanocomposite Catalyzes the Synthesis of Fluorescent Aminobenzotriazoles Derivatives

With the development of green chemistry, it is still a challenge to maintain the unstable valence state of the metal in heterogeneous catalysts and realize new catalytic synthesis methods. In this paper, it is reported that an univalent copper nanocomposite (Cu@Al/SBA-15) can efficiently catalyze the formation of novel amino-containing benzotriazoles with great fluorescence properties in a new synthetic strategy. Subsequently, its application is further verified by an acylation reaction to produce a series of novel benzotriazoles derivatives with high yield. It is worth noting that the Cu@Al/SBA-15 nanocomposites not only enable the reaction completed with high yield in a short time, but can also be recycled many times without a significant reduction in activity, and the leaching of copper and aluminum species in reaction system is negligible. Finally, the detailed and feasible reaction mechanism is also provided.

Magnetically recyclable silica-coated ferrite magnetite-K10 montmorillonite nanocatalyst and its applications in O, N, and S-acylation reaction under solvent-free conditions

Novel silica-coated ferrite nanoparticles supported with montmorillonite (K₁₀) have been prepared successfully by using a simple impregnation method. Further, these nanoparticles were characterized by using different analytical methods like FT-IR, PXRD, EDS, and FE-SEM techniques. In addition, these nanoparticles have been explored for their catalytic activity for the O, N, and S-acylation reactions under solvent-free conditions which gave moderate to excellent yields in a much shorter reaction time. Moreover, these nanoparticles could easily be separated out from the reaction medium after the reaction completion by using an external magnetic field and have been re-used for 10 cycles without any significant loss of the catalytic activity.

Novel silica-coated ferrite nanoparticles supported with montmorillonite (K₁₀) have been prepared and explored for their catalytic activity for the O, N, and S-acylation reactions under solvent-free conditions.

Sustainable plant and microbes-mediated preparation of Fe3O4 nanoparticles and industrial application of its chitosan, starch, cellulose, and dextrin-based nanocomposites as catalysts

Iron oxide nanoparticles (Fe₃O₄ NPs) attracted significant scientific interest, considering their immense diversity of usage and biocompatibility. Perceiving the growing importance of sustainable chemistry, many efforts have been made to prepare these NPs using naturally occurring materials mostly plant extracts and microbes. Magnetic NPs (MNPs) are commonly used as composites and are considered in two matters: synthesis and modification of their functional groups. Biopolymeric nanocomposites are a group of hybrid materials composed of natural polymers and inorganic nanomaterials. Biopolymers such as alginate, cellulose, starch, gelatin, chitosan, etc. have been considered extensively and provided composites with better electrical and mechanical thermal properties. Fe₃O₄ NPs incorporated in a polymer and biopolymer matrix is a good instance of the functional nanostructure, which has been able to enhance the properties of both ingredients. These hybrids can have impressive applications in various scopes such as magneto-optical storage, electromagnetic interference shielding, catalyst, water remediation, biomedical sensing, and so on. In this study, we have tried to briefly introduce Fe₃O₄ NPs, investigate the green and sustainable methods that have been suggested for its synthesis and review recent utilization of their biopolymeric nanocomposite (NC) including starch, chitosan, dextrin, etc. as catalysts and photocatalysts.

Nanoassembly of gold nanoparticles: An active substrate for size-dependent surface-enhanced Raman scattering

Nanoassembly of gold nanoparticles has been achieved through a simple and facile process without using any surfactants or linkers. Atomic force microscopy confirmed assemblies of several tens of microns, whereas tiny interparticle gaps less than 5 nm was revealed by scanning electron microscopy. Such nanoassemblies with tiny interparticle gaps were found to be highly surface-enhanced Raman scattering (SERS)-active with enhancement factor in the order of 6 to 8. Contrary to usual trends in nanoparticles size dependent SERS enhancement, such 2D nanoassemblies of different sizes of nanoparticles showed relatively broadened SERS enhancement distribution. Finite difference time domain (FDTD) analysis was employed to highlight the EM-field distribution in connection to such giant SERS enhancement. In depth and hotsite-wise analysis on EM near-field distributions for monomers, dimers and septamers of 50 nm of gold nanoparticles were carried out at three specific incident polarizations (i.e. s-, 45° and p-polarizations). At s- and p-polarization the strongest hotsites were having the EM near-field distributions in the range of 124.8 and 133.3 V/m respectively with lower population of confined EM near-fields. Such correlated investigation will be indispensable to understand and interpret hierarchical and functional nanoassemblies from its unit nanoparticle blocks for the advances of technological breakthroughs.

E-waste upcycling for the synthesis of plasmonic responsive gold nanoparticles

One of the current challenges in circular economy is the ability to transform waste into valuable products. In this work, waste of electrical and electronic equipment (WEEE) was used as a gold source to prepare stable gold nanoparticles (AuNP). The proposed methodology involves a series of physical and chemical separation steps, carefully designed according to the complex nature of the selected WEEE and the targeted product. In a first step, pins from microprocessors were separated by mechanical treatments, allowing to concentrate gold in a metallic fraction. A two-step hydrometallurgical method was subsequently performed, to obtain a Au (III) enriched solution. Such solution was used as a secondary raw material to obtain AuNP. For that purpose, a specific synthetic method was developed, adapted to the high acidity and ionic strength of the solution. Thanks to the use of two easily available reducing agents (sodium citrate and ascorbic acid) and a polymeric stabilizer (PVP), it was possible to obtain high purity AuNP presenting a mixture of well-defined spherical and triangular shapes. These AuNP were finally deposited onto glass substrates and present a sensitive response to refractive index changes in the environment, a necessary condition towards application in optical sensors. In summary, this upcycling case study demonstrates that e-waste can successfully replace primary raw materials to obtain highly valuable and useful nanomaterials. These results highlight the potential of urban mining as a sustainable and circular approach to the development of nanotechnologies.

Supported metal and metal oxide particles with proximity effect for catalysis

External influence is essential for any change to occur in this world. Similarly, the reaction path of a chemical reaction can be changed with the addition of a catalyst from outside. Sometimes a catalyst performs better when it remains associated with an inert substance, which is called a support material (SM). Improved catalyst accomplishment arises from the 'proximity effect'. Even inert supports play a role in better product formulation or environmental remediation. In this review, it has been shown how the SM, as a nest, aids the catalyst particle synergistically to perform a good job in a chemical reaction. The structure-function relationship of SM helps in catalyst activation to some extent, and produces active centres that are difficult to fully ascertain. In the text, Langmuir-Hinshelwood (L-H), Mars-van Krevelen (MVK), and Eley-Rideal (E-R) mechanisms are highlighted for the adsorption processes as the case may be. Again, the importance of SM for both catalyst and substrates has been consolidated here in the text. Finally, the role of the initiator and the promoter is also discussed in this review.

Three-Dimensional Cathodes for Electrochemical Reduction of CO2: From Macro- to Nano-Engineering

Rising anthropogenic CO2 emissions and their climate warming effects have triggered a global response in research and development to reduce the emissions of this harmful greenhouse gas. The use of CO2 as a feedstock for the production of value-added fuels and chemicals is a promising pathway for development of renewable energy storage and reduction of carbon emissions. Electrochemical CO2 conversion offers a promising route for value-added products. Considerable challenges still remain, limiting this technology for industrial deployment. This work reviews the latest developments in experimental and modeling studies of three-dimensional cathodes towards high-performance electrochemical reduction of CO2. The fabrication-microstructure-performance relationships of electrodes are examined from the macro- to nanoscale. Furthermore, future challenges, perspectives and recommendations for high-performance cathodes are also presented.

Highly Active Ruthenium Catalyst Supported on Magnetically Separable Mesoporous Organosilica Nanoparticles

A facile and direct method for synthesizing magnetic periodic mesoporous organosilica nanoparticles from pure organosilane precursors is described. Magnetic ethylene- and phenylene-bridged periodic mesoporous organosilica nanoparticles (PMO NPs) were prepared by nanoemulsification techniques. For fabricating magnetic ethylene- or phenylene-bridged PMO NPs, hydrophobic magnetic nanoparticles in an oil-in-water (o/w) emulsion were prepared, followed by a sol–gel condensation of the incorporated bridged organosilane precursor (1,2 bis(triethoxysilyl)ethane or 1,4 bis(triethoxysilyl)benzene), respectively. The resulting materials were characterized using high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (XRD), solid-state NMR analysis, and nitrogen sorption analysis (N2-BET). The magnetic ethylene-bridged PMO NPs were successfully loaded using a ruthenium oxide catalyst by means of sonication and evaporation under mild conditions. The obtained catalytic system, termed Ru@M-Ethylene-PMO NPS, was applied in a reduction reaction of aromatic compounds. It exhibited very high catalytic behavior with easy separation from the reaction medium by applying an external magnetic field.

Fabrication of Pd NPs on pectin-modified Fe3O4 NPs: A magnetically retrievable nanocatalyst for efficient C-C and C-N cross coupling reactions and an investigation of its cardiovascular protective effects

The present report represents the synthesis of a novel Pd NPs immobilized over a natural polysaccharide (pectin) coated Fe₃O₄ magnetic nanocomposite material (Fe₃O₄@pectin/Pd) for investigating the cardiovascular protective effects. The biomolecular functionalization not only stabilizes the ferrite nanoparticles from agglomeration but also provides an environment for the biogenic reduction of Pd²⁺ ions. This protocol is a promising breakthrough for the synthesis of a quasi-heterogeneous catalyst, a bridge between heterogeneous and homogeneous medium. The structure, morphology and physicochemical properties of the material were characterized utilizing various analytical techniques like FT-IR, FE-SEM, TEM, VSM, EDX-elemental mapping, ICP, EDX and XPS. The catalyst showed excellent reactivity in C-C and C-N cross coupling reactions via Suzuki and Buchwald-Hartwig reactions respectively. An array of different biphenyls and aryl amines were then procured by reactions of various aryl halides with phenylboronic acid or secondary amines over the catalyst affording good to excellent yields. The catalyst was easily recoverable using an external magnet and thereafter recycled for several trials with insignificant palladium leaching or loss in catalytic performance. To investigate the cardiovascular protective activities of catalyst, the MTT assay was done on Human Aortic Endothelial Cells (HAEC), Human Coronary Artery Endothelial Cells (HCAEC), and Human Pulmonary Artery Endothelial Cells (HPAEC) cell lines. Nanocatalyst-treated cell cutlers significantly (p ≤ 0.01) decreased the caspase-3 activity, and DNA fragmentation. It raised the cell viability and mitochondrial membrane potential in the high concentration of Mitoxantrone-treated HAEC, HCAEC, and HPAEC cells. According to the above findings, nanocatalyst can be administrated as a cardiovascular protective drug for the treatment of cardiovascular diseases after approving in the clinical trial studies in humans.

A novel highly active and reusable carbon based platinum-ruthenium nanocatalyst for dimethylamine-borane dehydrogenation in water at room conditions

In this paper, we present platinum/ruthenium nanoparticles supported on Vulcan carbon (PtRu@VC) as a nanocatalyst for the dehydrogenation of dimethylamine-borane (DMAB) in aqueous solution under mild conditions. PtRu@VC nanocatalyst was fabricated using the alcohol-reduction techniques which is a facile and effective method. The prepared PtRu@VC nanocatalyst exhibited a good stabilization and an effective catalytic activity for hydrogen evolution from the DMAB dehydrogenation in water at room temperature. The composition of PtRu@VC nanocatalyst was investigated using different analytical techniques inductively coupled plasma optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (P-XRD) and X-ray photoelectron spectroscopy (XPS). A monodispersedPt/Ru metals distributions on VC (as supporting material) were revealed by TEM and HR-TEM analyses. The mean particle size of PtRu@VC nanocatalyst was found to be 3.15 ± 0.76 nm. XPS analysis for PtRu@VC nanocatalyst showed that almost Pt-Ru metals were found to be the metallic state. Catalytic experimental results showed that PtRu@VC nanocatalyst has a high catalytic activity with an excellent turn-over frequency (TOF_initial) value of 14926.2 h⁻¹ (248.77 min⁻¹) in the dehydrogenation of DMAB in water at room temperature. Additionally, in the paper, we report some different kinetic data obtained from different experimental parameters of temperature, catalyst and substrate concentrations conducted for DMAB dehydrogenation in water catalyzed with PtRu@VC nanocatalyst.

N-Arylation of (hetero)arylamines using aryl sulfamates and carbamates via C–O bond activation enabled by a reusable and durable nickel(0) catalyst

An effective and general aryl amination protocol has been developed using a magnetically recoverable Ni(0) based nanocatalyst.

Magnetically separable Ru-containing catalysts in supercritical deoxygenation of fatty acids

In the current paper, the possibility of the use of magnetically separable catalysts containing ruthenium oxide species in the supercritical deoxygenation of stearic acid for producing of the second generation of biodiesel is reported. Three different supports (silica, ceria, and hypercrosslinked polystyrene) were used for the stabilization of magnetic nanoparticles (MNPs) and Ru-containing particles. The effect of support on the magnetic properties as well as the catalytic activity of the obtained systems was studied. All synthesized catalysts were shown to provide high stearic acid conversion (up to 95 %). The highest yield of C17+ hydrocarbons (up to 86 %) was observed while using the Ru–Fe3O4-HPS system. Ru–Fe3O4-HPS was characterized by the high values of the specific surface area (364 m2/g) and saturation magnetization (4.5 emu/g). The chosen catalytic system was found to maintain its catalytic activity for a minimum of 10 consecutive cycles.

Magnetic Fe3O4@SiO2-Pt and Fe3O4@SiO2-Pt@SiO2 Structures for HDN of Indole

The effect of a second porous SiO₂ shell in the activity and selectivity of the Fe₃O₄@SiO₂–Pt catalyst in the hydrodenitrogenation of indole is reported. The double Fe₃O₄@SiO₂–Pt@SiO₂ structure was prepared by coating Fe₃O₄ nanoparticles with tetraethyl orthosilicate (TEOS) with a further impregnation of 1.0 wt.% of Pt on the (3-aminopropyl)triethoxysilane functionalized Fe₃O₄@SiO₂ structures. The second porous SiO₂ shell, obtained by using a hexadecyltrimethylammonium bromide (CTAB) template, covered the Fe₃O₄@SiO₂–Pt catalyst with a well-defined and narrow pore-sized distribution. The full characterization by TEM, inductively coupled plasma-optical emission spectroscopy (ICP-OES), XRD, and N₂ adsorption isotherm at 77 K and vibrating sample magnetometry (VSM) of the catalysts indicates homogeneous core@shell structures with a controlled nano-size of metallic Pt. A significant effect of the double SiO₂ shell in the catalytic performance was demonstrated by both a higher activity to eliminate the nitrogen atom of the indole molecule present in model liquid fuel and the improvement of the catalytic stability reaching four consecutive reaction cycles with only a slight conversion level decrease.

Mechanochemical synthesis of carbon-stabilized Cu/C, Co/C and Ni/C nanocomposites with prolonged resistance to oxidation

Metal-carbon nanocomposites possess attractive physical-chemical properties compared to their macroscopic counterparts. They are important and unique nanosystems with applications including in the future development of nanomaterial enabled sensors, polymer fillers for electromagnetic radiation shields, and catalysts for various chemical reactions. However, synthesis of these nanocomposites typically employs toxic solvents and hazardous precursors, leading to environmental and health concerns. Together with the complexity of the synthetic processes involved, it is clear that a new synthesis route is required. Herein, Cu/C, Ni/C and Co/C nanocomposites were synthesized using a two-step method including mechanochemical treatment of polyethylene glycol and acetates of copper, nickel and cobalt, followed by pyrolysis of the mixtures in an argon flow at 700 °C. Morphological and structural analysis of the synthesized nanocomposites show their core-shell nature with average crystallite sizes of 50 (Cu/C), 18 (Co/C) and 20 nm (Ni/C) respectively. The carbon shell originates from disordered sp² carbon (5.2–17.2 wt.%) with a low graphitization degree. The stability and prolonged resistance of composites to oxidation in air arise from the complete embedding of the metal core into the carbon shell together with the presence of surface oxide layer of metal nanoparticles. This approach demonstrates an environmentally friendly method of mechanochemistry for controllable synthesis of metal-carbon nanocomposites.

Inorganic Perovskite-Induced Synergy on Highly Selective Pd-Catalyzed Hydrogenation of Cinnamaldehyde

The transformation of various organic molecules into value-added chemicals has been driven by the success in development of highly active catalytic systems. Heterogeneous catalysts have found use in many industrial processes by virtue of their ease of separation and high activities in various reactions. However, many processes employing heterogeneous catalysts in the transformation of organic molecules suffer significantly when it comes to product selectivity. Herein, we report on the synthesis of highly selective palladium nanoparticle (Pd NP)-containing catalysts. The heterogeneous catalysts reported herein consist of active mixed-metal oxides, in the form of perovskites as catalysts, and as catalytic supports for Pd NPs. The activity of pure perovskites when applied as catalysts in the hydrogenation of cinnamaldehyde is 3 factors lower compared with Pd NPs immobilized on them. However, considering the fact that perovskites achieved percentage conversions between 18 and 25% in a short period of time makes them perfect candidates to replace platinum group metals in the future. In addition to being earmarked as the future of catalysis, perovskites induced a synergistic effect on the conversion of the substrate compared to when Pd NPs are immobilized on the silica support. Furthermore, these catalysts are 100% selective to hydrocinnamaldehyde and stable for up to five catalytic cycles. With regard to reusability of the catalysts, Pd/LaFeO₃ was used as a benchmark catalyst and revealed the need for surface restructuring of the catalyst for optimum activity.

Metal-Organic Frameworks in Polymer Science: Polymerization Catalysis, Polymerization Environment, and Hybrid Materials

The development of metal-organic frameworks (MOFs) has had a significant impact on various fields of chemistry and materials science. Naturally, polymer science also exploited this novel type of material for various purposes, which is due to the defined porosity, high surface area, and catalytic activity of MOFs. The present review covers various topics of MOF/polymer research beginning with MOF-based polymerization catalysis. Furthermore, polymerization inside MOF pores as well as polymerization of MOF ligands is described, which have a significant effect on polymer structures. Finally, MOF/polymer hybrid and composite materials are highlighted, encompassing a range of material classes, like bulk materials, membranes, and dispersed materials. In the course of the review, various applications of MOF/polymer combinations are discussed (e.g., adsorption, gas separation, drug delivery, catalysis, organic electronics, and stimuli-responsive materials). Finally, past research is concluded and an outlook toward future development is provided.