Synthesis,Characterization, and Applications of Copper Nanoparticles

Copper nanoparticles with different structural properties and effective biological effects may be fabricated using new green protocols. The control over particle size and in turn size-dependent properties of copper nanoparticles is expected to provide additional applications. Various methods for the synthesis of copper nanoparticles have been reported including chemical methods, physical methods, biological methods, and green synthesis. Biological methods involve the use of plant extracts, bacteria, and fungi. Commendable work has been done regarding the synthesis and stability of copper nanoparticles. There is a need to summarize the behavior of copper nanoparticles in different media under various conditions. Here, a complete list of the literature on the synthesis of copper nanoparticles, their properties, stabilizing agents, factors affecting the morphology, and their applications is presented. The importance of copper nanoparticles compared to other metal nanoparticles are due to high conductivity. Methods for the synthesis of copper nanoparticles, including green protocols using plants and micro-organisms compared chemical methods, have also been reviewed.     

Colloidal Metal Nanocatalysts: Synthesis,Characterization, and Catalytic Applications

Metal nanoparticles are key materials in heterogeneous catalysis due to their high catalytic activity and selectivity to the desired product. Accordingly, they are playing a pivotal role in most heterogeneous catalytic reactions that are steeply growing with the development of a colloidal synthetic protocol that enables fine control of size, shape, morphology and composition of metal nanoparticles at an atomic level. These colloidal metal nanoparticles can be dispersed on a rigid support such as mesoporous silica, metal oxide and zeolite, which utilizes metal nanoparticles as model heterogeneous catalysts in industrially important processes involving hydrogenation/dehydrogenation, isomerization and cracking. In this review article, we highlight the recent progress on general colloidal synthetic routes with technological advances in characterization tools that enable the atomic-scale observation of metal nanoparticles. Structure-dependent contributions on the control of product selectivity and turnover rate are also discussed by combining advanced ex situ and in situ surface characterization tools that can monitor the structural change of metal nanocatalysts as well as the evolution of reaction intermediates under the reaction conditions.     

Nanoantioxidants: Pioneer Types,Advantages, Limitations,and Future Insights

Free radicals are generated as byproducts of normal metabolic processes as well as due to exposure to several environmental pollutants. They are highly reactive species, causing cellular damage and are associated with a plethora of oxidative stress-related diseases and disorders. Antioxidants can control autoxidation by interfering with free radical propagation or inhibiting free radical formation, reducing oxidative stress, improving immune function, and increasing health longevity. Antioxidant functionalized metal nanoparticles, transition metal oxides, and nanocomposites have been identified as potent nanoantioxidants. They can be formulated in monometallic, bimetallic, and multi-metallic combinations via chemical and green synthesis techniques. The intrinsic antioxidant properties of nanomaterials are dependent on their tunable configuration, physico-chemical properties, crystallinity, surface charge, particle size, surface-to-volume ratio, and surface coating. Nanoantioxidants have several advantages over conventional antioxidants, involving increased bioavailability, controlled release, and targeted delivery to the site of action. This review emphasizes the most pioneering types of nanoantioxidants such as nanoceria, silica nanoparticles, polydopamine nanoparticles, and nanocomposite-, polysaccharide-, and protein-based nanoantioxidants. This review overviews the antioxidant potential of biologically synthesized nanomaterials, which have emerged as significant alternatives due to their biocompatibility and high stability. The promising nanoencapsulation nanosystems such as solid lipid nanoparticles, nanostructured lipid carriers, and liposome nanoparticles are highlighted. The advantages, limitations, and future insights of nanoantioxidant applications are discussed.     

Detail review on chemical,physical and green synthesis,classification, characterizations and applications of nanoparticles

ABSTRACT

Nanotechnology is an emerging field of science. The base of nanotechnology is nanoparticles. The size of nanoparticles ranges from 1 to 100?nm. The nanoparticles are classified into different classes such as inorganic nanoparticles, organic nanoparticles, ceramic nanoparticles and carbon base nanoparticles. The inorganic nanoparticles are further classified into metal nanoparticles and metal oxide nanoparticles.similarly carbon base nanoparticles classified into Fullerene, Carbon nanotubes, Graphene, Carbon nanofiber and carbon black Nanoparticles are also classified on the basis of dimension such as one dimension nanoparticles, two-dimension nanoparticles and three-dimension nanoparticles. The nanoparticles are synthesized by using two approaches like top-down approach and bottom-up approach. In this review chemical, physical and green synthesis of nanoparticles is reported. The synthesized nanoparticles are synthesized using different qualitative and quantitative techniques. The Qualitative techniques include Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectrophotometry, Scanning electron microscope (SEM), X.ray diffraction (XRD) and Atomic Force Microscopy (AFM). The Quantitative techniques include Transmission Electron Microscopy (TEM), Annular Dark-Field Imaging (HAADF) and Intracranial pressure (ICP). The nanoparticles have different application which is reported in this review.     

Rigid nanoscopic containers for highly dispersed, stable metal and bimetal nanoparticles with both size and site control

We demonstrate a novel strategy for the preparation of mesoporous silica-supported, highly dispersed, stable metal and bimetal nanoparticles with both size and site control. The supporting mesoporous silica, functionalized by polyaminoamine (PAMAM) dendrimers, is prepared by repeated Michael addition with methyl acrylates (MA) and amidation reaction with ethylenediamine (EDA), by using aminopropyl-functionalized mesoporous silica as the starting material. The encapsulation of metal nanoparticles within the dendrimer-propagated mesoporous silica is achieved by the chemical reduction of metal-salt-impregnated dendrimer-mesoporous silica by using aqueous hydrazine. The site control of the metal or bimetal nanoparticles is accomplished by the localization of inter- or intradendrimeric nanoparticles within the mesoporous silica tunnels. The size of the encapsulated nanoparticles is controlled by their confinement to the nanocavity of the dendrimer and the mesopore. For Cu and Pd, particles locate at the lining of mesoporous tunnels, and have diameters of less than 2.0 nm. For Pd/Pt, particles locate at the middle of mesoporous tunnels and have diameters in the range of 2.0-4.2 nm. The Pd and Pd/Pt nanoparticles are very stable in air, whereas the Cu nanoparticles are stable only in an inert atmosphere.     

Tuning the size,concaveness, and aspect ratio of concave cubic gold nanoparticles produced with high reproducibility

Reproducible fabrication of concave cubic gold nanoparticles with precise control over size, concaveness, and aspect ratio is important because the nanoscale structural characteristics can influence their plasmonic and catalytic properties. However, this is particularly challenging because the number of synthetic parameters involved in the fabrication strategy adds complexity to the reaction mechanism. Here, we introduce a simplified seed-mediated method and uncover the unknown conceptual insights on how the different halides and their concentration influence the surface structure and stability of underpotential silver monolayer deposited on the high energy facets of nanoparticles. The results reveal that adding Br^? and I^? ions to growth solution offers a predominant way to control the reaction kinetics and engineering nanoparticles with a predefined size, morphology, concaveness, aspect ratio, and plasmonic properties. Using spectroscopy and microscopy techniques, we shed new light on the reaction kinetics of concave cubic gold nanoparticles using the combined influence of silver underpotential deposition and halides. The strategy developed here can be expanded to fabricate gold nanoparticles of complex geometries. The results from our electromagnetic calculations suggest that the self-assembled superstructure of concave cubic gold nanoparticles can be more appealing for developing an ultra-sensitive sensing platform than to self-assembled superstructures of truncated cubic gold nanoparticles.     

Size, shape, and structural control of metallic nanocrystals

In this review, we show that chemical reduction in colloidal assemblies favors the formation of size- and shape-controlled metallic nanoparticles. The key parameters that make possible the size control of spherical nanoparticles produced in spherical reverse micelles are the degree of hydration of the reactants, the dynamic character of the micelles, the capping with the surfactant, and the reducing agent concentration. The particle shape can be controlled by combining the strategy of the surfactant-based template and the capping of salts or molecules. Proof of the quality of the samples is given by the observation of two- and three-dimensional spontaneous self-organizations.     

Spacer-mediated synthesis of size-controlled gold nanoparticles using geminis as ligands

We report a new methodology for the size-controlled aqueous synthesis of gold nanoparticles using geminis with different spacers as ligands. Geminis possess a unique structure in which two hydrophobic chains and two polar headgroups are combined via a spacer. We herein demonstrate that the spacer can be used as a tool to control particle size when geminis are used as ligands for gold nanoparticles. Varying the spacer length of geminis yields facile control over the size and size distribution of nanoparticles. For the 18-s-18-capped gold nanoparticles, FTIR and TGA experiments indicate that the geminis form bilayers on the surface of gold nanoparticles, which serve as templates that control the formation of nanoparticles. The smallest particles are obtained with a moderate spacer length (s = 8) because in that case the gemini bilayers interdigitate to the fullest degree to reach the maximum chain-chain interaction, thus yielding the most compact coating on the surface of gold nanoparticles. This work provides a new approach to the size control of nanoparticles.     

In situ hydrophobized, shape-anisotropic nanoparticles for composite materials

An inverse emulsion technique which allows the anisotropic growth of a broad variety of inorganic nanoparticles, together with an efficient hydrophobization, is described. This method is based upon the combined use of amphiphilic copolymers, which act as emulsifiers as well as compatibilizers, and structure-directing agents that control the crystallization of the inorganic nanoparticles. As a consequence, water-soluble, structure-directing agents can now be applied for the synthesis of hydrophobic, shape-anisotropic nanocrystals. More precisely, spherical, rod-like, and branched CdS as well as Au nanoparticles were prepared. Due to their excellent hydrophobization, these particles were homogeneously incorporated into a poly(2-ethylhexyl methacrylate) matrix. Their shape-dependent properties were transferred to nanocomposites as demonstrated for branched CdS nanocrystals. In comparison to more traditional materials composed of branched CdS nanoparticles, which are stabilized by low molecular weight amphiphiles, our composites show much less scattering. This is due to the homogenous distribution of the nanoparticles in the matrix.     

Modulation of surface charge, particle size and morphological properties of chitosan-TPP nanoparticles intended for gene delivery

This work investigates the polyanion initiated gelation process in fabricating chitosan-TPP (tripolyphosphate) nanoparticles in the size range of 100-250 nm intended to be used as carriers for the delivery of gene or protein macromolecules. It demonstrates that ionic gelation of cationic chitosan molecules offers a flexible and easily controllable process for systematically and predictably manipulating particle size and surface charge which are important properties in determining gene transfection efficacy if the nanoparticles are used as non-viral vectors for gene delivery, or as delivery carriers for protein molecules. Variations in chitosan molecular weight, chitosan concentration, chitosan to TPP weight ratio and solution pH value were examined systematically for their effects on nanoparticle size, intensity of surface charge, and tendency of particle aggregation so as to enable speedy fabrication of chitosan nanoparticles with predetermined properties. The chitosan-TPP nanoparticles exhibited a high positive surface charge across a wide pH range, and the isoelectric point (IEP) of the nanoparticles was found to be at pH 9.0. Detailed imaging analysis of the particle morphology revealed that the nanoparticles possess typical shapes of polyhedrons (e.g., pentagon and hexagon), indicating a similar crystallisation mechanism during the particle formation and growth process. This study demonstrates that systematic design and modulation of the surface charge and particle size of chitosan-TPP nanoparticles can be readily achieved with the right control of critical processing parameters, especially the chitosan to TPP weight ratio.     

Magnetic nanoparticles: synthesis, protection, functionalization, and application

This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in the size and shape control of magnetic nanoparticles has been made by developing methods such as co-precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.     

Controlling chemical reactivity at solid-solution interfaces by means of hydrophobic magnetic nanoparticles

Hydrophobic magnetic nanoparticles are employed to reversibly regulate the hydrophobic/hydrophilic properties of surfaces and to control the electrochemistry and bioelectochemistry at chemically modified electrodes. Selective bioelectrocatalytic transformations at relay-functionalized electrodes are accomplished by the magnetic attractions of the hydrophobic magnetic nanoparticles with coadsorbed hydrophobic redox relays to the electrode. The selective activation of one of two biocatalysts solubilized in the aqueous electrolyte solution in the absence or presence of hydrophobic magnetic nanoparticles results in the specific activation of bioelectrocatalytic processes. The magnetic attraction and retraction of hydrophobic magnetic nanoparticles to and from semiconductor nanoparticle (CdS)-functionalized electrodes enable the control of the photocurrent directions at the electrode from cathodic to anodic directions, respectively. The magnetic attraction of the hydrophobic magnetic nanoparticles to the surfaces is also employed to control biorecognition and biocatalytic transformations at solid supports. The magnetic attraction and retraction of the hydrophobic magnetic nanoparticles to and from the surfaces allow the blockage and activation of DNA hybridization, polymerization, and enzymatic digestion, respectively.     

Expeditious synthesis of water-soluble, monolayer-protected gold nanoparticles of controlled size and monolayer composition

A protocol is reported for the preparation of water-soluble, thiol-protected Au nanoparticles (Au-MPC) where dioctylamine is used as a stabilizing agent when the gold cluster is formed using the two-phase Brust and Schiffrin procedure. The amount of amine controls the size of the nanoparticles in the 1.9-8.9 nm diameter range. The final stabilization of the gold clusters by addition of functionalized thiols is performed under very mild conditions compatible with most biomolecules. The procedure is suitable for a wide variety of functional groups present in the thiol and allows one to use thiol mixtures with a precise control of their composition in the monolayer. As a proof of principle, examples of nanoparticles protected with thiols comprising functional groups ranging from polyethers, saccharides, polyamines and ammonium ions are reported.     

Copper Oxide Nanoparticles: Synthesis,Characterization and Their Antibacterial Activity

Copper oxide nanoparticles were prepared by electrochemical reduction method using tetra butyl ammonium bromide (TBAB) as structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio by optimizing current density and molar concentration of the ligand. The reduction process takes place under inert atmosphere of nitrogen over a period of 2 h. Such nanoparticles are prepared using simple electrolysis cell in which the sacrificial anode as a commercially available copper metal sheet and platinum (inert) sheet act as a cathode. The parameters such as current density, solvent polarity, distance between electrodes, and concentration of stabilizers are used to control the size of nanoparticles. The synthesized copper oxide nanoparticles were characterized by using UV–Visible, FT-IR, XRD, SEM–EDS and TEM analysis techniques. The nanoparticles were tested for antibacterial activity against human pathogens like Escherichia coli (E. coli) and Staphylococcus strains and which was proved to be excellent.     

Room-Temperature Laser Synthesis in Liquid of Oxide,Metal-Oxide Core-Shells,and Doped Oxide Nanoparticles

Although oxide nanoparticles are ubiquitous in science and technology, a multitude of compositions, phases, structures, and doping levels exist, each one requiring a variety of conditions for their synthesis and modification. Besides, experimental procedures are frequently dominated by high temperatures or pressures and by chemical contaminants or waste. In recent years, laser synthesis of colloids emerged as a versatile approach to access a library of clean oxide nanoparticles relying on only four main strategies running at room temperature and ambient pressure: laser ablation in liquid, laser fragmentation in liquid, laser melting in liquid and laser defect-engineering in liquid. Here, established laser-based methodologies are reviewed through the presentation of a panorama of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non-equilibrium compounds, metal-oxide core–shells and other anisotropic morphologies. So far, these materials showed several useful properties that are discussed with special emphasis on catalytic, biomedical and optical application. Yet, given the endless number of mixed compounds accessible by the laser-assisted methodologies, there is still a lot of room to expand the library of nano-crystals and to refine the control over products as well as to improve the understanding of the whole process of nanoparticle formation. To that end, this review aims to identify the perspectives and unique opportunities of laser-based synthesis and processing of colloids for future studies of oxide nanomaterial-oriented sciences.     

Silver nanoparticles capped by oleylamine: formation, growth, and self-organization

Nearly monodisperse silver nanoparticles have been prepared in a simple oleylamine-liquid paraffin system. Intensive study has found that the formation process of silver nanoparticles could be divided into three stages: growth, incubation, and Ostwald ripening stages. Ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM have all demonstrated the occurrence of Ostwald ripening, which could result in better control over the size and size distribution of silver nanoparticles. SAXS (small-angle X-ray scattering) results show that the as-obtained silver nanoparticles can self-assemble into ordered arrays. The possible reduction mechanism of silver ions by oleylamine is related to the Ag+-mediated conversion of primary amines to nitriles.     

Silver metal nanosized particles: Control of particle size,self assemblies in 2D and 3D superlattices and optical properties

Water in oil droplets are used to control the size of silver metal nanoparticles. After synthesis, the silver metal particles are extracted from reverse micelles and redispersed in a non polar solvent. By increasing the size of the water droplets the average size of silver nanoparticles increases from 2 nm to 7 nm with a rather high size distribution. To narrow the panicle distribution a size selected precipitation method is used. By deposition of a dilute solution containing the coated particles on a carbon grid, the particles arrange themselves in a monolayer organized in a hexagonal network. At high particle concentration, the particles are organized in multilayers forming microcrystals arranged in a face centered cubic structure. The optical properties of the silver nanoparticles isolated in micellar solution or self-assembled in 2D or 3D supperlattices are reported.     

Vapor-phase synthesis of nanoparticles

An overview of methods for preparing nanoparticles in the vapor phase is given, and recent advances are reviewed. Developments in instrumentation for monitoring vapor-phase synthesis of nanoparticles and in modeling these processes are also included. The most important developments relate to improved control and understanding of nanoparticle aggregation and coalescence during synthesis, and to methods for producing multi-component nanoparticles.     

Colloidal self-assemblies used as templates to control size,shape and self-organization of nanoparticles

In this paper we show that the use of colloidal assemblies as templates favors the control of the size and shape of nanoparticles. As expected theoretically, the change in size and shape of copper metal nanosized particles induces changes in their optical properties. Cylindrical copper metal particles having the same size and shape can be obtained in various regions of the phase diagram when the template is made of interconnected cylinders. Self-assembly of silver metal nanoparticles is reported. Monolayers of particles organized in a hexagonal network are formed over very large domains. Small or large aggregates can also be produced, and, in these aggregates, the particles are highly organized and form pseudo-crystals with a face-centered cubic structure for various particles sizes. The optical properties of the silver nanoparticles isolated in micellar solution or self-assembled in 2D or 3D supperlattices are reported. Syntheses of magnetic fluids differing in their particle size are presented. The magnetic properties differ with the particle size.     

Biogenic Nanoparticle-Mediated Augmentation of Seed Germination,Growth, and Antioxidant Level of Eruca sativa Mill. Varieties

A study was undertaken to examine the influence of biogenic nanoparticles synthesized from Tridax procumbens on different parameters of seed germination, seedling growth, and various biochemical parameters in four Eruca sativa varieties having low percentage of germination. Seeds were treated with different concentrations (30 and 40 ppm) of biogenic nanoparticles, of which 30 ppm was found to be the most effective and was therefore used for subsequent studies. Initially, the effect of biogenic nanoparticles on germination percentage, speed of germination, coefficient of germination, mean germination time, shoot and root length, fresh and dry matter, and vigor index was studied. From the experiments performed and the results obtained, it was evident that the treatment with biogenic nanoparticles decreased the electrolyte leakage and level of malondialdehyde as compared to control. The treatment with biogenic nanoparticles enhanced the levels of proline and ascorbic acid and stimulated the antioxidant enzyme activities resulting in the reduced level of reactive oxygen species. These activities were found to be variety-dependent. The possible involvement of biogenic nanoparticles in the production of new pores in seed coat during their penetration, resulting in the influx of the nutrients inside the seed, is suggested. This accelerated seed germination is followed by rapid seedling growth. The present findings indicated that biogenic nanoparticles promote seed germination in E. sativa by overcoming the detrimental effects of reactive oxygen species (ROS) and improving the antioxidative defense system which finally result in increased seedling growth.