Synergy in the Catalytic Activity of Bimetallic Nanoparticles and New Synthetic Methods for the Preparation of Fine Chemicals

A Review on Plant-Mediated Synthesis of Bimetallic Nanoparticles, Characterisation and Their Biological Applications

The study of bimetallic nanoparticles (BNPs) has constantly been expanding, especially in the last decade. The biosynthesis of BNPs mediated by natural extracts is simple, low-cost, and safe for the environment. Plant extracts contain phenolic compounds that act as reducing agents (flavonoids, terpenoids, tannins, and alkaloids) and stabilising ligands moieties (carbonyl, carboxyl, and amine groups), useful in the green synthesis of nanoparticles (NPs), and are free of toxic by-products. Noble bimetallic NPs (containing silver, gold, platinum, and palladium) have potential for biomedical applications due to their safety, stability in the biological environment, and low toxicity. They substantially impact human health (applications in medicine and pharmacy) due to the proven biological effects (catalytic, antioxidant, antibacterial, antidiabetic, antitumor, hepatoprotective, and regenerative activity). To the best of our knowledge, there are no review papers in the literature on the synthesis and characterisation of plant-mediated BNPs and their pharmacological potential. Thus, an effort has been made to provide a clear perspective on the synthesis of BNPs and the antioxidant, antibacterial, anticancer, antidiabetic, and size/shape-dependent applications of BNPs. Furthermore, we discussed the factors that influence BNPs biosyntheses such as pH, temperature, time, metal ion concentration, and plant extract.

Ag-Catalyzed Multicomponent Synthesis of Heterocyclic Compounds: A Review

The investigation of the procedures for the multi-component synthesis of heterocycles has attracted the interest of organic and medicinal chemists. The use of heterogeneous catalysts, especially transition metal catalysts in organic synthesis, can provide a new, improved alternative to traditional methods in modern synthetic chemistry. The main focus is on the utilization of silver as a catalyst for the multi-component synthesis of heterocyclic compounds. The present review describes some important reported studies for the period of 2010 to 2020. Conclusion: The present review addresses some of the important reported studies on multi-component synthesis of heterocycles in the period of 2010-2020. These approaches were performed under classical and nonclassical conditions, using Ag salts, Ag NPs, Ag on the support, Ag as co-catalysts with other transition metals, ionic liquids, acidic or basic materials. Most of the reported reactions were performed under solvent-free conditions or in green solvents and the utilized catalysts were mostly recyclable. The main aim of the present review is to provide the organic chemists with the most appropriate procedures in the multi-component synthesis of desired heterocycles using silver catalysts.

Production of biodiesel from oleaginous fungal lipid using highly catalytic bimetallic gold-silver core-shell nanoparticle

AIMS

This study aims to synthesize, characterize and apply gold-silver core-shell nanoparticles (Au@Ag NPs), a nanocatalyst, to maximize biodiesel production from fungal isolate Fusarium solani (FS12) via a transesterification one-step reaction.

METHODS AND RESULTS

The Au@Ag NPs structure was examined by UV-vis spectrophotometer, transmission electron microscopy, X-ray diffraction and Fourier transform infrared (FTIR). All devices were used to characterize Au@Ag NPs and confirmed successful synthesis of nanoparticles. Fungal lipid was quantitatively determined by sulfo-phospho-vanillin colorimetric method. Among 15 F. solani isolates obtained from rhizospheric soils of the date palm, F. solani (AF12) was chosen as the highly significant producer that accumulates above 20% lipid. The maximum biodiesel yield was 91.28 ± 0.19%, obtained under the optimum reaction conditions of 3% Au@Ag NPs as nanocatalyst concentration, and 1:20 oil to methanol molar ratio at 70℃ for 30 min. HPLC method was applied for monitoring in situ transesterification reaction. FTIR spectroscopy was used in qualitative analysis of biodiesel by verifying the presence of unique characteristic peaks of diagnostic significance. The quality of the biodiesel produced was confirmed by the high purity of fatty acid methyl esters analysis content up to >99%.

CONCLUSIONS

These findings propose the applicability of F. solani (FS12) as a promising isolate to accumulate lipids and biodiesel production as a feedstock.

SIGNIFICANCE AND IMPACT OF THE STUDY

The link between nanotechnology and fungi. Au@Ag NPs were synthesized at room temperature, which displayed high catalytic activity for in situ transesterification reaction. Catalytic activity appeared at low temperature, mole ratio and short reaction time. Oleaginous fungi are described as easily grown, have short life cycle, are cost-effective, and they utilized various sources of carbon up to waste and a simplified process to develop scale-up production as well, economic value, opposite the usage of vegetable oils which need for large agricultural areas.

Hydrosilylation of carbonyls over electron-enriched Ni sites of intermetallic compound Ni3Ga heterogeneous catalyst

Nanoparticulate intermetallic compound Ni3Ga supported on SiO2 has emerged as a highly efficient catalyst for the hydrosilylation of carbonyls, such as aldehydes and ketones, at room temperature. Formation of electron-enriched Ni via alloying with Ga is the key to the catalytic performance.

Prospects and Applications of Palladium Nanoparticles in the Cross-coupling of (hetero)aryl Halides and Related Analogues

Discovering efficient methods for the formation of carbon-carbon bonds is a central ongoing theme in organic synthesis. Cross-coupling reactions catalysed by metal nanoparticles are attractive alternatives to the traditional use of metal counterparts due to the catalytic tunability, selectivity, recyclability and reusability of the nanoparticles. The ongoing search for sustainable processes demands that reusable and environmentally benign catalysts are used. While the advantages of nanoparticles catalysts over bulk catalysts cannot be overemphasised, the problem of sintering, agglomeration and leaching are drawbacks to their full industrial applications. Hence, efforts are being made towards advancing the efficiency of the catalytic nanoparticle systems over the years. This review presents the progress, the challenges and the prospects of palladium nanoparticle with focus on Heck, Suzuki, Hiyama and Sonogashira cross-coupling reactions involving (hetero) aryl halides and the analogues.

Nickel−palladium alloy nanoparticles supported on reduced graphene oxide decorated with metallic aluminum nanoparticles (Al-rGO/NiPd): a multifunctional catalyst for the transfer hydrogenation of nitroarenes and olefins using water as a hydrogen source

A multifunctional nanocatalyst, Al-rGO/Ni₄₀Pd₆₀, is designed for the transfer hydrogenation of nitroarenes and olefins using water as a hydrogen source and solvent.

Facile Synthesis, Characterization, Anti-Microbial and Anti-Oxidant Properties of Alkylamine Functionalized Dumb-Bell Shaped Copper-Silver Nanostructures

Admirable studies have been established on the utilization of ligand-materials as bimetallic nanoparticles in the field of nanoscience and biotechnology. UV-Vis, XRD, HR-TEM, STEM-HAADF, EDS, FTIR, and DPPH analyses characterized the optical, structural, compositional morphological, and antioxidant properties of synthesized Cu-Ag nanostructures. The spectrum of UV-Vis exhibited absorption bands at 590 and 413 nm, which reflects the surface plasmon resonance of copper-silver nanostructures. Herein, our exploration of alkylamine stabilized copper/silver nanostructures while using hexadecylamine as capping material and their primary biomedical investigation on antimicrobial and antioxidant studies is reported. Cu-Ag bimetallic nanostructures were more effective against gram-negative bacteria E. coli and Klebsiella when compared to gram-positive bacteria. The antioxidant activity of Cu-Ag nanoparticles was comparable with Ascorbic acid.

Earth-Abundant Bimetallic Nanoparticle Catalysts for Aerobic Ammoxidation of Alcohols to Nitriles

Heterogeneous nitrogen-doped carbon-incarcerated iron/copper bimetallic nanoparticle (NP) catalysts prepared from nitrogen-containing polymers were developed. These catalysts showed activity higher than that of the corresponding monometallic NPs for aerobic ammoxidation of alcohols to nitriles. The important procedure for high activity in the catalyst preparation was found to be a simultaneous reduction of two metal salts.

Core-shell PdCu bimetallic colloidal nanoparticles in Sonogashira cross-coupling reaction: mechanistic insights into the catalyst mode of action

Core-shell PdCu nanoparticles with different metal proportions were synthesized using a one-pot methodology and characterized by STEM, HRTEM, XANES and EXAFS analysis. The bimetallic nanoparticles were applied as catalysts in the Sonogashira cross-coupling reaction to investigate the mode of action of the PdCu in the reaction. The copper content directly influenced the generation of the cross-coupling product, shaping the performance of the catalyst. A quasi-homogeneous reaction pathway was evidenced by kinetics and poisoning experiments as well as XAS, HRTEM and HRMS analysis. These findings help to elucidate the mode of action of the PdCu nanocatalysts in the, as yet, unrevealed Sonogashira mechanism and the potential development of new nanocatalysts.

Ag x Cu y Ni z Trimetallic Alloy Catalysts for the Electrocatalytic Reduction of Benzyl Bromide in the Presence of Carbon Dioxide

Different compositions of trimetallic alloy containing silver, copper, and nickel (Ag x Cu y Ni z ) were electrodecorated in a protic ionic liquid medium on glassy carbon electrodes in order to investigate the suitability of the materials as catalysts for electrochemical reduction of carbon dioxide (CO2). Surface characteristic morphology obtained by scanning electron microscopy shows cauliflower crystallites for the deposit of Ag, whereas materials of Cu and Ni exhibit cubic grains and fine particles, respectively. Deposits of trimetallic alloy containing Ag, Cu, and Ni exhibit the mixture of the three characteristic features. Further, trimetallic alloy containing a large amount of Ag provides high crystallinity, whereas predominance of Cu as well as Ni results in porous structures, as revealed by X-ray diffraction analysis. Atomic absorption spectroscopy () was used to determine the compositions of different alloy materials. The suitability of nanomaterials as cathodes for electroreduction of benzyl bromide in CO2 containing 0.1 M tetra-n-butylammonium tetrafluoroborate (DMF/TBABF4)/N,N-dimethylformamide medium was explored. The linear sweep voltammogram reveals that Ag46Cu40Ni14 shows higher cathodic peak current and lower cathodic peak potential than those of other deposited nanomaterials as well as alloys, indicating its higher catalytic activity for such an electroreduction process, whereas potentiostatic electrolysis confirms the abovementioned results.

Palygorskite Supported AuPd Alloy Nanoparticles as Efficient Nano-Catalysts for the Reduction of Nitroarenes and Dyes at Room Temperature

In this work, AuPd alloy palygorskite based Pal-NH₂@AuPd nano-catalysts were prepared and used as catalysts for the reduction of nitroarenes and dyes at room temperature. The surface of palygorskite (Pal) was first modified with 3-aminpropyltriethoxysilane, and then covered with AuPd alloy nanoparticles through co-reduction of HAuCl₄ and K₂PdCl₄. The morphology and structures of the Pal-NH₂@AuPd nano-catalysts were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The as-synthesized Pal-NH₂@AuPd nano-catalysts displayed excellent catalytic performance in reducing 4-nitrophenol (4-NP) and various other nitroaromatic compounds. Moreover, the catalytic activities of the Pal-NH₂@AuPd nano-catalysts were adjustable via changing the atomic ratio of AuPd alloy nanoparticles, leading to the Pal-NH₂@Au₄₈Pd₅₂ component as having the best atomic ratio. The Pal-NH₂@Au₄₈Pd₅₂ continued to display good catalytic stability after being reused for several cycles and there were no obvious changes, either of the morphology or the particle size distribution of the nano-catalysts. Furthermore, these Pal-NH₂@Au₄₈Pd₅₂ nano-catalysts also provided a convenient and accessible way for the degradation of dyes in artificial industrial wastewater.

Development of N-Doped Carbon-Supported Cobalt/Copper Bimetallic Nanoparticle Catalysts for Aerobic Oxidative Esterifications Based on Polymer Incarceration Methods

Heterogeneous nitrogen-doped carbon-incarcerated cobalt/copper bimetallic nanoparticle (NP) catalysts, prepared from nitrogen-containing polymers, were developed, and an efficient catalytic process for aerobic oxidative esterification was achieved in the presence of a low loading (1 mol %) of catalyst that could be reused and easily reactivated. This protocol enabled diverse conditions for the bimetallic NP formation step to be screened, and significant rate acceleration by inclusion of a copper dopant was discovered. The catalytic activity of the bimetallic Co/Cu catalysts is much higher than that for cobalt catalysts reported to date and is even comparable with noble-metal NP catalysts.

Pd–Ni Bimetallic Nanoparticles Supported on Zro2 as an Efficient Catalyst for Suzuki–Miyaura Reactions

Pd–Ni bimetallic nanoparticles (BMNPs) supported on ZrO2 were prepared by an impregnation–reduction method. The BMNPs showed excellent catalytic performance in Suzuki carbon–carbon cross-coupling reactions and almost quantitative conversion of the substrates was obtained under mild conditions in the absence of ligand. The excellent catalytic performance of the bimetallic catalyst could be a result of the synergistic effect between the two metal components. The catalyst showed outstanding recyclability during the reaction process; no obvious decrease in catalytic performance was observed after five cycles.

Au@Pd Bimetallic Nanocatalyst for Carbon-Halogen Bond Cleavage: An Old Story with New Insight into How the Activity of Pd is Influenced by Au

AuPd bimetallic nanocatalysts exhibit superior catalytic performance in the cleavage of carbon-halogen bonds (C-X) in the hazardous halogenated pollutants. A better understanding of how Au atoms promote the reactivity of Pd sites rather than vaguely interpreting as bimetallic effect and determining which type of Pd sites are necessary for these reactions are crucial factors for the design of atomically precise nanocatalysts that make full use of both the Pd and Au atoms. Herein, we systematically manipulated the coordination number of Pd-Pd, d-orbital occupation state, and the Au-Pd interface of the Pd reactive centers and studied the structure-activity relationship of Au-Pd in the catalyzed cleavage of C-X bonds. It is revealed that Au enhanced the activity of Pd atoms primarily by increasing the occupation state of Pd d-orbitals. Meanwhile, among the Pd sites formed on the Au surface, five to seven contiguous Pd atoms, three or four adjacent Pd atoms, and isolated Pd atoms were found to be the most active in the cleavage of C-Cl, C-Br, and C-I bonds, respectively. Besides, neighboring Au atoms directly contribute to the weakening of the C-Br/C-I bond. This work provides new insight into the rational design of bimetallic metal catalysts with specific catalytic properties.

Facile Synthesis of Catalytic AuPd Nanoparticles within Capillary Microreactors Using Polyelectrolyte Multilayers for the Direct Synthesis of H2O2

Microreactors present innovative solutions for problems pertaining to conventional reactors and therefore have seen successful application in several industrial processes. Yet, its application in heterogeneously catalyzed gas-liquid reactions has been challenging, mainly due to the lack of an easy and flexible methodology for catalyst incorporation inside these reactors. Herein, we report a facile technique for obtaining small (<2 nm) and well-distributed catalytic nanoparticles on the walls of silica-coated capillaries, that act as micro(channel) reactors. These particles are formed in situ on the reactor walls using polyelectrolyte multilayers (PEMs), built by layer-by-layer self-assembly. Manipulating the PEMs' synthesis condition gives easy control over metal loading, without compromising on particle size. Both monometallic (Au and Pd) and bimetallic (AuPd) nanoparticles were successfully obtained using this technique. Finally, these catalytic microreactors were found to exhibit exceptional activity for the direct synthesis of hydrogen peroxide from H2 and O2.

Facile Fabrication of Ordered Component-Tunable Heterobimetallic Self-Assembly Nanosheet for Catalyzing "Click" Reaction

How to maximize the number of desirable active sites on the surface of the catalyst and minimize the number of sites promoting undesirable side reactions is currently an important research topic. In this study, a new way based on the synergism to achieve the successful fabrication of an ordered heterobimetallic self-assembled monolayer (denoted as BMSAM) with a controlled composition and an excellent orientation of metals in the monolayer was developed. BMSAM consisting of phenanthroline and Schiff-base groups was prepared, and its novel heterobimetallic (Cu and Pd) self-assembled monolayer anchored in silicon (denoted as Si-Fmp-Cu-Pd BMSAM) with a controlled composition and a fixed position was fabricated and characterized by UV, cyclic voltammetry, Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and water-drop contact angle (WDCA) analyses. The effects of Si-Fmp-Cu-Pd BMSAM on its catalytic properties were also systematically investigated using "click" reaction as a template by WDCA, XPS, SEM, XRD, ICP-AES and in situ Fourier transform infrared analyses in a heterogeneous system. The results showed that the excellent catalytic characteristic could be attributed to the partial (ordered or proper distance) isolation of active sites displaying high densities of specific atomic ensembles. The catalytic reaction mechanism of the click reaction interpreted that the catalytic process mainly occurred on the surface of the monolayer, internal active site (Pd) and rationalized that the Cu(I) species and Pd(0) reduced from the Cu(II) and Pd(II) catalyst were active species, which had a proper distance between two different metals. The cuprate-triazole intermediate and the palladium intermediate, whose production is the key step, should lie in a proper position between the copper and active palladium sites, with which the reaction rate of transmetalation would be improved to increase the amount of the undesired Sonogashira coupling product.

Chemoenzymatic one-pot reaction of noncompatible catalysts: combining enzymatic ester hydrolysis with Cu(i)/bipyridine catalyzed oxidation in aqueous medium

Combination of a lipase (CALB) with a Cu/bipyridine catalyst for environmentally benign synthesis of aldehydes from their corresponding esters.

Activated nanostructured bimetallic catalysts for C–C coupling reactions: recent progress

This minireview highlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions.

FePd alloy nanoparticles assembled on reduced graphene oxide as a catalyst for selective transfer hydrogenation of nitroarenes to anilines using ammonia borane as a hydrogen source

rGO–Fe₄₈Pd₅₂ is an efficient, selective and robust catalyst for transfer hydrogenation of nitroarenes to anilines using ammonia borane as a hydrogen source.

Perspectives on zeolite-encapsulated metal nanoparticles and their applications in catalysis

Recent strategies for the design of zeolites with unusual architectures and porosities offer many opportunities for the encapsulation of catalysts.