A facile synthesis of monodisperse Au nanoparticles and their catalysis of CO oxidation

Monodisperse Au nanoparticles (NPs) have been synthesized at room temperature via a burst nucleation of Au upon injection of the reducing agent t-butylamine-borane complex into a 1, 2, 3, 4-tetrahydronaphthalene solution of HAuCl₄·3H₂O in the presence of oleylamine. The as-synthesized Au NPs show size-dependent surface plasmonic properties between 520 and 530 nm. They adopt an icosahedral shape and are polycrystalline with multiple-twinned structures. When deposited on a graphitized porous carbon support, the NPs are highly active for CO oxidation, showing 100% CO conversion at −45 °C. This article is published with open access at Springerlink.com     

A facile and novel way for the synthesis of nearly monodisperse silver nanoparticles

A facile and novel way was reported for the preparation of nearly monodisperse silver nanoparticles with controlled hydrophilic or hydrophobic surface, using trioctylphosphine as the surfactant and stabilizer. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and UV-vis spectroscopy. The monodisperse silver nanoparticles showed a strong surface plasmon resonance band at 402 nm from the UV-vis spectrum.     

The effect of composition and structural ordering on the magnetism of FePt nanoparticles

Spherical 4 nm FePt nanoparticles were synthesized by the simultaneous decomposition of Fe(CO)5 and the polyol reduction of Pt(acac)2. The final Fe-to-Pt composition was tuned between 15-55 at.% by varying the ingredient precursor ratios. The effect of composition and structural ordering on the macroscopic magnetic features of final FePt nanoparticles was examined via post-synthetic annealing stages at different conditions. Structural ordering is promoted in all cases, though samples approximating equiatomic Fe/Pt ratios eventually transform to fct-FePt phase while the FePt3-phase is favored for the Pt-richer samples. Consequently, the magnetic features of the annealed nanoparticles may be categorized; the hard magnetic FePt region dominating for Fe content between 40-55 at.% and the soft magnetic FePt3 region dominating in the region 20-30 at.% while Fe content less than 20 at.% results in Pt-richer phases with diminishing ferromagnetic behavior.     

A facile photochemical route for the synthesis of gold nanoparticles

Synthesis of high-quality, water-dispersed gold nanoparticles (AuNPs), has been prepared employing luminol as a special reductant, via direct irradiation of the molecular precursors rather than traditional heat of the solvent. The final quality of the photochemically generated nanomaterial was characterized by transmission electron microscopy, resonance light scattering spectra, and cyclic voltammetry. AuNPs could enhance the chemiluminescence intensity of the luminol-H₂O₂ system, attributing to their catalysis. On the basis, we developed a nanoparticle-based chemiluminescence method for the determination of H₂O₂. The results demonstrated that it was possible to detect hydrogen peroxide in the range of 10⁻⁸–10⁻³ M.     

Reduction of ordering temperature of self-assembled FePt nanoparticles by addition of Au and Ag

The [FePt]94Au6 and [FePt]90Ag10 nanoparticle arrays were synthesized on Si substrates by a reverse micellar method, combined with plasma treatment and in-situ deposition of a SiO2 overlayer, and the post annealing step was performed to drive the face-centered cubic to tetragonal phase transition. These FePt nanoparticles exhibit a quasi-hexagonal order with tailored inter-particle spacing and particle size. The effects of the Ag and Au on the structural and magnetic properties of FePt were investigated. The results indicate that both Au and Ag additives can remarkably enhance the coercivity and reduce the ordering temperature, however, the optimum composition is different for them. The optimum composition is determined to be [FePt]94Au6 and [FePt]90Ag10, respectively, for which the ordering temperature of FePt nanoparticles is reduced by -100 degrees C. After 600 degrees C annealing, the [FePt]94Au6 and [FePt]90Ag10 nanoparticles are totally ferromagnetic with apparent larger coercivities of -7.0 kOe, which is about 3.8 kOe larger than that of the pure FePt nanoparticles. The mechanism of the chemical ordering acceleration may be attributed to the defects and strains caused by the Au/Ag additives.     

Highly luminescent monodisperse CdSe nanoparticles synthesized in aqueous solution

Simple routes to synthesize highly photoluminescent monodisperse thiol-capped CdSe nanoparticles are reported. The as-synthesized water-soluble CdSe nanoparticles possess higher photoluminescence quantum efficiency (up to 22%), smaller values of full width of half-maximum of photoluminescence spectra (down to 31 nm), higher photostability, and better monodispersity compared with the nanoparticles made from other aqueous routes. The quality of CdSe nanoparticles prepared by our route compares very favourably with those prepared in organic solution.     

Activated hydride-mediated solution phase synthesis of crystallized antimony(0) nanoparticles

This work presents a simple method to produce large quantities of crystallized antimony(0) nanoparticles through SbCl₃ chemical reduction using t-BuONa-activated sodium hydride. t-BuONa acts as a superficial stabilizer of Sb(0) nanoparticles inhibiting their growth and avoiding aggregation. The Sb(0) nanoparticles were characterized using transmission electron microscopy, XPS analysis and X-ray powder diffraction. Results obtained show that rhombohedral Sb(0) with diameters of ca. 4.7 ± 1.9 nm were produced. The influence of purification conditions on the aggregation state of Sb(0) particles is also described.     

A facile synthesis of CuInS2 nanoparticles from molecular single source precursors

CuInS2 nanoparticles have been synthesized via solvent thermolysis of novel bimetallic complexes of the general formula [(Ph3P)2CuIn(S2COR)4] (where R = CH3; C2H5; C(CH3)2); and [(Ph3P)2CuIn(SCH2CH2S)2]. These complexes have been prepared by the reactions of Na/KS2COR and NaSCH2CH2SNa with InCl3 and [(Ph3P)2CuNO3] in methanol, respectively. Solvent thermolyses of these complexes were carried out in ethylene glycol at 196 degrees C for different time periods. The nanoparticles obtained were characterized extensively by techniques like powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. The optical band gap of the nanoparticles was determined by diffuse reflectance spectroscopy (DRS).     

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.     

Ag-catalyzed synthesis of ultrafine nickel nanoparticles: A facile way to size control

We report here a facile strategy, Ag-catalyzed reduction of Ni²⁺ ions, for the synthesis of metallic nickel nanoparticles. The phase structure and morphology of particles were analyzed by means of X-ray diffraction and scanning electron microscopy. It was found that the resultant Ni nanoparticles had narrow size distribution, and the control of particle size could be easily achieved through manipulation of the molar ratio between nickel salts and silver seeds. XRD analysis of the final particles showed the crystalline nickel structure and the presence of metallic Ag, which was influenced by the Ni/Ag molar ratio. The effects of reduction temperature on the final particle size were also investigated.     

Non-catalytic facile synthesis of superhard phase of boron carbide (B13C2) nanoflakes and nanoparticles

Boron Carbide is one the hardest and lightest material that is also relatively easier to synthesis as compared to other superhard ceramics like cubic boron nitride and diamond. However, the brittle nature of monolithic advanced ceramics material hinders its use in various engineering applications. Thus, strategies that can toughen the material are of fundamental and technological importance. One approach is to use nanostructure materials as building blocks, and organize them into a complex hierarchical structure, which could potentially enhance its mechanical properties to exceed that of the monolithic form. In this paper, we demonstrated a simple approach to synthesize one- and two-dimension nanostructure boron carbide by simply changing the mixing ratio of the initial compound to influence the saturation condition of the process at a relatively low temperature of 1500 degrees C with no catalyst involved in the growing process. Characterization of the resulting nano-structures shows B13C2, which is a superhard phase of boron carbide as its hardness is almost twice as hard as the commonly known B4C. Using ab-initio density functional theory study on the elastic properties of both B12C3 and B13C2, the high hardness of B13C2 is consistent to our calculation results, where bulk modulus of B13C2 is higher than that of B4C. High resolution transmission electron microscopy of the nanoflakes also reveals high density of twinning defects which could potentially inhibit the crack propagation, leading to toughening of the materials.     

Hexagonal nanoplatelets of CuSe synthesized through facile solution phase reaction

A novel solution-phase synthetic route for obtaining hexagonal nanoplatelets of copper selenide is presented. Chemical reaction involved in the synthesis is the reduction of copper selenite with hydrazine hydrate. The reaction is performed in various solvents and in the presence of different capping agents. The structure, composition and properties of the nanomaterials obtained were studied with various techniques. The reduction reaction carried out in ethylene glycol even in the absence of any capping agents gave the best results. The relatively low temperature of reaction, usage of single precursor and the surfactant-free growth of nanomaterials make this synthetic route a promising one in perspectives of material science.     

Nonaqueous phase synthesis of copper nanoparticles

Copper nanoparticles were synthesized in a nonaqueous solution of cetyltrimethylammonium bromide with isopropanol as a solvent. Cetyltrimethylammonium bromide in isopropanol is observed to play a role as a catalyst where isopropanol is the reducing agent. The surface plasmon band characteristic for Cu nanoparticles can be observed at approximately 560 nm in the UV-visible spectra at molar ratios for Cu2+: cetyltrimethylammonium bromide of 1:15 and 1:30. On the other hand, at molar ratios of 1:0.25 and 1:1 the presence of peak at approximately 310 nm can be attributed to oligomeric clusters of Cu0. Formation of Cu0 was further confirmed from the X-ray diffraction analysis. The diffractograms exhibited peaks at 2theta = approximately 41.6 degrees, approximately 51.6 degrees, and approximately 74.3 degrees, corresponding to Cu0. At lower concentration of cetyltrimethylammonium bromide (i.e., Cu2+: cetyltrimethylammonium bromide = 1:0.25) higher degree of size dispersity (particles between approximately 5-20 nm) can be noted from transmission electron micrograph. On the other hand, at the highest concentration of cetyltrimethylammonium bromide (i.e., Cu2+: cetyltrimethylammonium bromide = 1:30), formation of finer sized particles with a lower degree of size variation, approximately 2-10 nm, can be observed.     

Bulk synthesis of monodisperse Fe nanoparticles by electromagnetic levitational gas condensation method

A one-step bulk synthesis method for monodisperse Fe nanoparticles was developed by electromagnetic levitational gas condensation (ELGC) process. The Fe vapours ascending from the high temperature levitated droplet was condensed by cryogenic He-Ar gas mixture under atmospheric pressure. The spherical Fe nanoparticles with particle size of 72.1 ± 19.5 nm and a narrow size distribution were prepared using the He-20%Ar gas mixture with the flow rate of 20 l/min. The production rate of the one-step ELGC process was estimated as high as 10 g/h. The nanoparticles were passivated by the formation of a thin layer of Fe oxides with the thickness of 3 nm.     

Facile synthesis of monodisperse thermally immiscible Ag-Ni alloy nanoparticles at room temperature

Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand 100% Ag-Ni ANPs was observed in the system. Using Tetrakis hydroxymethyl phosphonium chloride resulted in construction of near-uniform ANPs in the easily controllable conditions of the present alloying procedure. Nanoparticles having up to 65% Ni were observed for the first time in this research.     

A facile synthesis of lipid stabilized gold nanoparticles: a step towards biodegradable biosensors

A new class of polylactone was successfully synthesized and utilized for the encapsulation and stabilization of gold nanoparticles. Core/shell nanoparticle architecture, in which a layer of this polymer surrounds the nanoparticle core have been investigated both as a means to improve the stability and surface chemistry and as a way of accessing unique physical properties that are not possible from one nano-material alone. Given the fact that only few systems has so far been developed for the encapsulation of nanoparticles, our success in using a new biodegradable biopolymer with inbuilt functionality reveals the robustness of this work. The biodegradability of this polylactone was evaluated using scanning electron microscopy (SEM). The morphology and stability of these gold-polymer hybrids were evaluated by using the transmission electron microscopy (TEM) and UV-VIS spectroscopy.     

Polymer-grafted magnetite nanoparticles via a facile in situ solution radical polymerisation

Polymer-grafted magnetic nanoparticles were prepared via in situ solution radical polymerisation. The oleic acid modified magnetic nanoparticles were prepared by the coprecipitation of magnetic nanoparticles in the presence of oleic acid. Then they were used as comonomers in the polymerisation of styrene. The products were characterised with Fourier transform infrared spectroscopy, thermogravimetric analysis and transmission electron microscope. The effect of the OA-MNPs added on the conversion of styrene (C%), the percentage of grafting (PG%) and the magnetic properties of the polystyrene/magnetic nanoparticles composites (PS/MNPs) were also investigated.     

Selection of microemulsion composition via study of phase behavior for synthesis of stable monodisperse platinum nanoparticles and optimization of experimental parameters

ABSTRACT

Monodisperse platinum nanoparticles were synthesized by microemulsion technique. Feasibility of formation of microemulsion with chosen proportions of components is a common problem with this method. Here, prior to preparation of microemulsion for synthesis purpose, systematic study was carried to check the suitability of selected microemulsion system by establishing phase diagram for ternary system at constant temperature on triangular coordinates. Temperature dependency of microemulsion was studied by preparing phase diagram of temperature against mass fraction of aqueous phase in ternary mixture. Both these triangular coordinate diagram at constant temperature and temperature dependency plots helped to choose proper concentrations of components in the system. Effects of molar concentration of water-to-surfactant ratio, platinum salt concentration, continuous oil phase concentration, and presence of cosurfactant with surfactant on particle size were investigated for selected system of components. Synthesized platinum nanoparticles were characterized by dynamic light scattering and transmission electron microscope. Light backscattering profiles obtained by Turbiscan were used to judge the stability of microemulsions. Further, partial weightage of affecting parameters on size of synthesized particle were studied by Taguchi orthogonal array method.     

Synthesis of FePt nanorods and nanowires by a facile method

FePt nanorods and nanowires have been synthesized by the reduction of Pt(acac)(2) and the thermal decomposition of Fe(CO)(5) in the presence of solvents/surfactants by simply controlling the sequence of addition of surfactants. The as-synthesized FePt nanorods and nanowires have a face centered cubic structure with average diameter of 3?nm. Length of nanorods and nanowires can be adjusted in the range of 15-150?nm by varying reaction parameters. Nanocrystalline L1(0) FePt phase with coercivity up to 24?kOe was obtained after heat treatments.