Synthesis Of Transition Metal Nanoparticles Research Articles

A Critical Review on Bio-mimetic Synthesis of Transition Metal Nanoparticles: Their Biomedical Applications in Veterinary Medicine

A Critical Review on Bio-mimetic Synthesis of Transition Metal Nanoparticles: Their Biomedical Applications in Veterinary Medicine

Plant Extract Mediated Synthesis of Transition Metal Nanoparticles: A Review

Green technology is a fast evolving scientific topic that has attracted a lot of attention in recent years due to its wide range of applications. It is a multidisciplinary field that is safe, non-hazardous, and ecologically friendly, in contrast to chemical and physical approaches for nanoparticle synthesis. Because the existing biomolecules in plant extract act as both a reducing and capping agent, the produced nanoparticles are very stable. As a result, nanoparticles that have been manufactured have a wide range of potential applications in the environmental and biomedical domains. The current report contains current information on numerous green synthesis methods that rely on different plant parts for green transition metal nanoparticles synthesis.

Pros and Cons of Sacrificial Anode Electrolysis for the Preparation of Transition Metal Colloids: A Review

AbstractElectrochemical synthesis of transition metal nanoparticles (NPs) and related oxides is highly appealing, as it affords nanomaterials with high purity and dimensional control by properly setting only few experimental parameters. The resurgence of electrochemical routes to NPs can be traced back to seminal works by the Reetz's group, about 25 years ago. Despite many advantages, this method has intrinsic limitations, mainly related to the use of organic solvents, which may limit real‐life applications of the as‐prepared NPs. Therefore, an important current issue in the electrosynthesis of these systems regards the preparation of aqueous and long‐lived colloids. In this Review, we provide an overview of the most promising electrosyntheses of colloidal nanomaterials; real‐life applications of electrochemically produced NPs will also be commented on.

Moving Frontiers in Transition Metal Catalysis: Synthesis, Characterization and Modeling.

Nanosized transition metal particles are important materials in catalysis with a key role not only in academic research but also in many processes with industrial and societal relevance. Although small improvements in catalytic properties can lead to significant economic and environmental impacts, it is only now that knowledge-based design of such materials is emerging, partly because the understanding of catalytic mechanisms on nanoparticle surfaces is increasingly improving. A knowledge-based design requires bottom-up synthesis of well-defined model catalysts, an understanding of the catalytic nanomaterials "at work" (operando), and both a detailed understanding and a prediction by theoretical methods. This article reports on progress in colloidal synthesis of transition metal nanoparticles for preparation of model catalysts to close the materials gap between the discoveries of fundamental surface science and industrial application. The transition metal particles, however, often undergo extensive transformations when applied to the catalytic process and much progress has recently been achieved operando characterization techniques under relevant reaction conditions. They allow better understanding of size/structure-activity correlations in these systems. Moreover, the growth of computing power and the improvement of theoretical methods uncover mechanisms on nanoparticles and have recently predicted highly active particles for CO/CO2 hydrogenation or direct H2 O2 synthesis.

Carbon nanofibers as supports for metal nanoparticles

The easy synthesis of transition metal nanoparticles supported on three types of carbon nanofibers (platelet: CNF-P, tubular: CNF-T, herringbone: CNF-H) and nitrogen-doped CNF-H (N-CNF-H) is accomplished by pyrolysis of metal carbonyl clusters such as Ru3(CO)12, Rh4(CO)12, and Ir4(CO)12, and alkene complexes such as Pd2(dba)3·CHCl3 and Pt(dba)2 [dba: dibenzylideneacetone]. Transmission electron microscopy of these CNFs with immobilized metal nanoparticles (M/CNFs and M/N-CNF-H) showed that metal nanoparticles whose size could be controlled, existed on the CNFs, and that their location was dependent on the surface nanostructure of the CNFs: on the edge of the graphite layers (CNF-P), in the tubes and on the surface (CNF-T), and between the layers and on the edge (CNF-H). Among these M/CNFs, Ru/CNF-P and Rh/CNF-T showed excellent catalytic activity towards arene hydrogenation with high reusability and functional group tolerance, while the Pt/CNF-P behaves as an efficient catalyst for the hydrogenation of substituted nitroarenes to the corresponding aniline derivatives with the other functional groups remaining intact. Pt and Pd nanoparticles supported on N-CNF-H act as poisoning catalysts for the transformation of internal alkynes to (Z)-alkenes over Pd/N-CNF-H, and for the transformation of nitroarenes to the corresponding anilines and N-hydroxylamines over Pt/N-CNF-H. [TANSO 2015 (No. 266) 35–40.]

On the two-step mechanism for synthesis of transition-metal nanoparticles.

The two-step particle synthesis mechanism, also known as the Finke-Watzky (1997) mechanism, has emerged as a significant development in the field of nanoparticle synthesis. It explains a characteristic feature of the synthesis of transition metal nanoparticles, an induction period in precursor concentration followed by its rapid sigmoidal decrease. The classical LaMer theory (1950) of particle formation fails to capture this behavior. The two-step mechanism considers slow continuous nucleation and autocatalytic growth of particles directly from precursor as its two kinetic steps. In the present work, we test the two-step mechanism rigorously using population balance models. We find that it explains precursor consumption very well, but fails to explain particle synthesis. The effect of continued nucleation on particle synthesis is not suppressed sufficiently by the rapid autocatalytic growth of particles. The nucleation continues to increase breadth of size distributions to unexpectedly large values as compared to those observed experimentally. A number of variations of the original mechanism with additional reaction steps are investigated next. The simulations show that continued nucleation from the beginning of the synthesis leads to formation of highly polydisperse particles in all of the tested cases. A short nucleation window, realized with delayed onset of nucleation and its suppression soon after in one of the variations, appears as one way to explain all of the known experimental observations. The present investigations clearly establish the need to revisit the two-step particle synthesis mechanism.

Synthesis of mono-disperse CoFe alloy nanoparticles with high activity toward NaBH4 hydrolysis

Traditionally, the synthesis of CoFe nanoparticles with tunable particle sizes and narrow particle size-distributions is accomplished via the use of expensive and air sensitive precursors and strong non-polar capping agents. Such strong capping agents can be difficult to remove from the nanoparticles and thus render them catalytically inactive. We report a novel solution-based methodology to synthesize CoFe alloy nanoparticles with narrow size-distributions using a combination of robust and inexpensive metal precursors and an easily removable polar capping agent. High resolution transmission electron microscope images show that the CoFe alloy nanoparticles are well crystallized, and the particle size is tunable from 9 to 24 nm while keeping a particle size standard deviation of 10%. The CoFe alloy nanoparticles show superior activity for NaBH4 hydrolysis compared with the best-known CoFe catalysts. This work represents a substantial improvement in the synthesis of transition metal nanoparticles, opening the pathway for their application to a number of technologically important catalytic applications.

Biobased green method to synthesise palladium and iron nanoparticles using Terminalia chebula aqueous extract

There are many methods to synthesise metal and metal oxide nanoparticles (NPs) using different reducing agents which are hazardous in nature. Although some researchers have used biobased materials for synthesis of these NPs, further research is needed in this area. To explore the scope of bio-extract for the synthesis of transition metal NPs, the present paper synthesises metal NPs replacing hazardous traditional reducing agents. This paper reports the synthesis of palladium and iron NPs, using aqueous extract of Terminalia chebula fruit. Reduction potential of aqueous extract of polyphenolic rich T. chebula was 0.63V vs. SCE by cyclic voltammetry study which makes it a good green reducing agent. This helps to reduce palladium and iron salts to palladium and iron NPs respectively. Powder X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) analyses revealed that amorphous iron NPs were within the size less than 80nm and cubic palladium NPs were within the size less than 100nm. The synthesised nanomaterials were remarkably stable for a long period and synthesis of stable metal NPs will need to be explored using biobased materials as reducing agents.

Microwave-Assisted Facile Synthesis of Palladium Nanoparticles in HEPES Solution and Their Size-Dependent Catalytic Activities to Suzuki Reaction

Palladium nanoparticles (NPs) were successfully synthesized via a rapid and facile microwave route in HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid) buffer solution. The shape- and size-controlled Pd nanoparticles could be obtained by one-step method without dependence of seed-mediated growth. The capping agent plays a key role in the formation of Pd NPs with different shape and size, which could be tuned by varying capping agents such as polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), sodium citrate (Na3(cit)) and potassium bromide (KBr). The size-dependent catalytic activities of the obtained Pd NPs for Suzuki coupling reaction were also investigated. It demonstrated that the catalytic activity of Pd NPs was enhanced regularly with the decrease of particle size. Pd NPs less than 10 nm exhibited better catalytic activities for Suzuki reaction than the commercial Pd/C catalyst. Pd/MWCNTs and Pd/SBA-15 nanocomposites were also prepared by a facile method and afforded good catalytic activity and reusability. This "green" synthetic protocol could be used as a general method for the rapid synthesis of transition metal nanoparticles.

A Self-Assembling Protein Template for Constrained Synthesis and Patterning of Nanoparticle Arrays

Self-assembling biomolecules that form highly ordered structures have attracted interest as potential alternatives to conventional lithographic processes for patterning materials. Here, we introduce a general technique for patterning nanoparticle arrays using two-dimensional crystals of genetically modified hollow protein structures called chaperonins. Constrained chemical synthesis of transition metal nanoparticles is initiated using templates functionalized with polyhistidine sequences. These nanoparticles are ordered into arrays because the template-driven synthesis is constrained by the nanoscale structure of the crystallized protein. We anticipate that this system may be used to pattern different classes of nanoparticles based on the growing library of sequences shown to specifically bind or direct the growth of materials.

Low-Temperature Synthesis of Transition Metal Nanoparticles from Metal Complexes and Organopolysilane Oligomers

Mo, W, and Cu nanoparticles (5−50 nm) are synthesized from reactions employing a metal complex, such as MoO2Cl2(DME), MoCl5, WCl6, (CuOtBu)4, or CuCl2, and a organopolysilane oligomer Si(SiMe3)4 or (SiMe2)6 either in a hexane solution (343 K) or in a sealed tube (473−673 K). Oxo- and chlorophilicities of the silyl groups provide for an energetically favored reaction route to reduce the metal complexes. The reaction byproducts are removed easily either by evaporation or dissolution into hydrocarbon solvents. It is proposed that the homogeneous mixing of the reactants in vapor and solution phases allows the association and growth of molecules into small clusters, then into nanosized metal particles.