Process For Synthesis Of Nanoparticles Research Articles

Fluid-dynamic characterization of a radio-frequency induction thermal plasma system for nanoparticle synthesis

The fluid flow in a radio-frequency induction thermal plasma (RF-ITP) system for the synthesis of nanoparticles has been characterized using three- and two-dimensional modelling supported by enthalpy probe and calorimetric measurements in order to provide insights for the improvement of the process. The RF-ITP system is composed of a commercial inductively coupled plasma torch mounted on a reaction chamber that is equipped with viewports for diagnostics. The three-dimensional model predicted an almost axisymmetric temperature field in the reaction chamber in agreement with enthalpy probe measurements performed along two perpendicular scan axes, whereas recirculating flow patterns resulted in being strongly non-axisymmetric. Temperature profiles at two distances (60 mm and 100 mm) from the torch outlet have been calculated using two-dimensional modelling and compared with enthalpy probe measurements for different operating conditions with the aim of validating the predictive ability of the modelling tool. Calorimetric measurements have been performed in order to estimate the power coupled to the torch, which is usually an arbitrary input parameter for the models. Poor agreement was obtained between energy balances from modelling and from calorimetric measurements and, starting from this, a discussion on the uncertainties in the calculation of the radiative losses has been proposed. Finally, new insights for the improvement of the process of nanoparticle synthesis in the RF-ITP system are suggested.

Mycogenic synthesis of silver nanoparticles by the Japanese environmental isolate Aspergillus tamarii

In this study, an environmental friendly process for the synthesis of silver nanoparticles (AgNPs) using a fungus Aspergillus tamarii has been investigated. The process of silver ion reduction by the fungal extracellular filtrate was spontaneous which lead to the development of an easy process for synthesis of silver nanoparticles. The AgNPs formed were characterized using UV–Visible spectrum, FTIR, and SEM. The results revealed that silver ions reduction by the fungal extracellular filtrate started at 420 nm after 0.5 h of incubation time. The FTIR peaks were observed at 1393, 1820, 2727, and 3545 cm−1. The SEM result showed the distribution of spherical AgNPs ranging from 25 to 50 nm.

Size Tailored Nanoparticles of ZrN Prepared by Single-Step Exothermic Chemical Route

ZrN nanoparticles were prepared by an exothermic reduction of <TEX>$ZrCl_4$</TEX> with <TEX>$NaN_3$</TEX> in the presence of NaCl flux in a nitrogen atmosphere. Using a solid-state combustion approach, we have demonstrated that the zirconium nitride nanoparticles synthesis process can be completed in only several minutes compared with a few hours for previous synthesis approaches. The chemistry of the combustion process is not complex and is based on a metathesis reaction between <TEX>$ZrCl_4$</TEX> and <TEX>$NaN_3$</TEX>. Because of the low melting and boiling points of the raw materials it was possible to synthesize the ZrN phase at low combustion temperatures. It was shown that the combustion temperature and the size of the particles can be readily controlled by tuning the concentration of the NaCl flux. The results show that an increase in the NaCl concentration (from 2 to 13 M) results in a temperature decrease from 1280 to <TEX>$750^{\circ}C$</TEX>. ZrN nanoparticles have a high surface area (50-70 <TEX>$m^2/g$</TEX>), narrow pore size distribution, and nano-particle size between 10 and 30 nm. The activation energy, which can be extracted from the experimental combustion temperature data, is: E = 20 kcal/mol. The method reported here is self-sustaining, rapid, and can be scaled up for a large scale production of a transition metal nitride nanoparticle system (TiN, TaN, HfN, etc.) with suitable halide salts and alkali metal azide.

Novel synthesis of crystalline polystyrene nanoparticles (nPS) by monomer atomization in microemulsion and their effect on thermal, rheological, and mechanical properties of polypropylene (PP)

The present paper relates to the atomized process for synthesis of polystyrene nanoparticles (nPS) between 10 to 100 nm with a controlled particle size. The effect of the initiator’s [ammonium persulfate (APS) and a combination of ascorbic acid/hydrogen peroxide (Ac/H2O2)] concentration on particle size and morphology of nPS have been reported in this work. The transmission electron microscopy (TEM) analysis showed that as the wt% of the initiator increased, the particle morphology changed from a spherical shape to a hexagonal shape. The effect of the particle size on crystallinity (X c ) and glass transition temperature (T g ) were also reported. α and β crystal structures of nPS were compared with bulk PS by Fourier transform infrared (FTIR) spectroscopy. The differential scanning calorimetric (DSC) study showed that nPS have higher T g compared to bulk PS. Isolated nPS were blended on Brabender in 0.10%, 0.20%, 0.25%, 0.30%, 0.40%, and 0.5% by weight respectively with polypropylene (PP) by melt process. Sharp increments in DSC peaks as well as thermal stability in thermogravimetric analysis (TGA) were observed up to a 0.25 wt% addition of nPS. The effect of nPS on rheological, thermal, and mechanical properties of PP was studied in comparison to a pristine PP and these improvements were due to a close packing of PP chains as recorded by the improvement in the crystallinity of the PP with the addition of the nPS (0.25 wt%) as shown by SEM.

The green synthesis, characterization and evaluation of the biological activities of silver nanoparticles synthesized from Iresine herbstii leaf aqueous extracts

Silver has been used since time immemorial in different chemical form to treat burns, wounds and several infections caused by pathogenic bacteria. Advancement of biological process of nanoparticles synthesis is evolving into a key area of nanotechnology. The current study deals with the synthesis, characterization of silver nanoparticles using Iresine herbstii and evaluation of their antibacterial, antioxidant and cytotoxic activity. The reaction mixture turned to brownish gray color after 7 days of incubation and exhibits an absorbance peak around 460nm characteristic of Ag nanoparticle. Scanning electron microscopy (SEM) and EDX analysis showed silver nanoparticles were pure and polydispersed and the size were ranging from 44 to 64nm. X-ray diffraction (XRD) studies revealed that most of the nanoparticles were cubic and face centered cubic in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. Biosynthesized silver nanoparticles showed potent antibacterial activity against human pathogenic bacteria. Phytosynthesized nanoparticles exhibited strong antioxidant activity as well as cytotoxicity against HeLa cervical cell lines. The approach of green synthesis seems to be cost efficient, eco-friendly and easy alternative to conventional methods of silver nanoparticles synthesis. The powerful bioactivity demonstrated by the synthesized silver nanoparticles leads towards the clinical use as antibacterial, antioxidant as well as cytotoxic agent.

Fe3O4 and CdS based bifunctional core–shell nanostructure

A room temperature solution process for synthesis of Fe3O4 nanoparticles and their hybrid core shell nanostructures using CdS as the shell material has been described. The as grown particles have been characterised using XRD, Rietveld refinement, high resolution transmission electron microscopy, atomic force microscopy, superconducting quantum interference device, optical absorbance and photoluminescence spectroscopy. A superparamagnetic response revealed from the magnetisation measurements of the as synthesised magnetite nanoparticles was retained even after the growth of the CdS shell. From luminescence and high resolution atomic force microscopy measurements, it is shown that the core–shell structures advantageously combine magnetic as well as fluorescence response with a tendency towards self-organization.

Investigation on effect of ambient pressure in wire explosion process for synthesis of copper nanoparticles by optical emission spectroscopy

Abstract Nanoparticles of copper have been synthesized by wire explosion technique in different ambient chamber pressure in nitrogen environment and effect of the ambient chamber pressure was studied. A copper wire of diameter of 125 μm and 6.1 cm in length is exploded at 1 bar, 500 mbar, 100 mbar and 50 mbar ambient chamber pressures. Current density in the order of 106 A cm− 2 from a 1.85 μF capacitor charged up to 10 kV has been applied to disintegrate the wire. The particle sizes were calculated from the peak of the X-ray diffraction pattern as well as from the transmission electron microscope image. The average particle size is found to be smallest for 500 mbar. Increase in average particle size is observed either with increase in the ambient chamber pressure to 1 bar or when it is decreased to 100 mbar, which makes the intermediate pressure of 500 mbar optimum for synthesis of smaller size particles. In-situ optical emission spectroscopy is carried out to study the plasma chemistry of the process and to determine the plasma parameters during the explosion. The mechanism of arc plasma formation is also studied. It is observed that the mechanism of the arc plasma formation plays a significant role in wire explosion process, which is found to be responsible for increasing particle size with either increased or decreased ambient chamber pressure from the intermediate pressure of 500 mbar.

Size-controlled synthesis, magnetic property, and photocatalytic property of uniform α-Fe2O3 nanoparticles via a facile additive-free hydrothermal route

A facile and effective hydrothermal process for the controllable synthesis of uniform hematite nanoparticles is presented. The structure and morphology of the products were characterized by powder X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results showed that the products were uniform α-Fe2O3 truncated nanooctahedra bound by 8 highly symmetric quasi-trigonal facets corresponding to a probable Miller index of {102} and the particle size was around 800 nm. The formation mechanism of the products, the effects of the reaction temperature, concentration of reactant, the solvent and the Fe(III) counter ion on the size and morphology of the products were investigated. Through adjusting the concentration of the FeCl3 solution, the size of the particles can be systematically tailored over a wide range from ca. 170 nm to ca. 2 μm. The magnetic properties and visible light photocatalytic properties of the as-obtained α-Fe2O3 products were investigated. The results showed that these α-Fe2O3 nanoparticles displayed ferromagnetic or weak ferromagnetic behavior at room temperature and exhibited a good photocatalytic property for rhodamine B.

Configurable 3D-Printed millifluidic and microfluidic ‘lab on a chip’ reactionware devices

We utilise 3D design and 3D printing techniques to fabricate a number of miniaturised fluidic 'reactionware' devices for chemical syntheses in just a few hours, using inexpensive materials producing reliable and robust reactors. Both two and three inlet reactors could be assembled, as well as one-inlet devices with reactant 'silos' allowing the introduction of reactants during the fabrication process of the device. To demonstrate the utility and versatility of these devices organic (reductive amination and alkylation reactions), inorganic (large polyoxometalate synthesis) and materials (gold nanoparticle synthesis) processes were efficiently carried out in the printed devices.

PREPARATION OF SILVER NANOPARTICLE BY MICROORGANISM AND ITS APPLICATION IN PHARMACY

Summary Materials by changing their size from normal to nanometer range shows a great change in their physicochemical properties primarily due to their small size and large specific surface area. A number of techniques have been reported for the preparation of metallic nanoparticles but there is a great need to develop environmentally benign nanoparticle synthesis processes without use of toxic chemicals. Therefore use of biological systems for preparation of nanoparticle is considered as a best solution where use of toxic chemicals and harsh preparation methods can be avoided. Silver nanoparticles can be prepared by bioreduction process using bacteria, actinomycetes and fungi etc very efficiently. The silver nanoparticles formed are having efficient antimicrobial activity.

A multidimensional population balance model to describe the aerosol synthesis of silica nanoparticles

The aim of this work is to present a new detailed multivariate population balance model to describe the aerosol synthesis of silica nanoparticles from tetraethoxysilane (TEOS). The new model includes a chemical representation of the silica particles to facilitate a detailed chemical description of particle processes. Silica nanoparticles are formed by the interaction of silicic acid monomers (Si(OH) 4) in the gas-phase as reported in a previous study. A multidimensional population balance model is developed where each particle is described by its constituent primary particles and the connectivity between these primaries. Each primary, in turn, has internal variables that describe its chemical composition, i.e., the number of Si, free O and OH units. Different particle processes, such as inception, surface reaction, coagulation, sintering, and intra-particle reactions, are formulated from first-principles that alter the particle ensemble and are two-way coupled to the gas-phase. The free parameters in the model are estimated by fitting the model response to experimental values of collision and primary particle diameters using low discrepancy Sobol sequences followed by the simultaneous perturbation stochastic approximation algorithm. The simulation results are finally presented at different process conditions. A strong dependence of particle properties on process temperature and inlet concentration is observed. The desirable operating conditions for different industrial applications are also highlighted. This work illustrates the significance of adopting a multidimensional approach to understand, and hence control, complex nanoparticle synthesis processes.

A Simple Process for Synthesis of Ag Nanoparticles and Sintering of Conductive Ink for Use in Printed Electronics

Various-sized Ag nanoparticles capped with oleylamine were synthesized by means of a thermal decomposition process for low-temperature electronic devices. The Ag nanoparticles, which had diameter of 5.1 nm to 12.2 nm, were synthesized in incubation and ripening stages related to nucleation and growth. After the Ag nanoparticles were made into ink with a proper solvent, inkjet printing and thermal sintering methods were used to form a metal thin film with thickness of 100 nm. A type of thermal sintering related to percolation transformation and surface sintering was conducted at a temperature much lower than the melting point of bulk Ag. The electrical resistivity was examined with the aid of a four-point probe system and compared with the resistivity of bulk Ag, showing that the Ag film had much higher resistivity than bulk Ag. To improve the electrical stability and properties, we applied hexamethyldisilazane (HMDS) surface treatment to the substrate and dipped the as-deposited films into methanol. Both treatments helped to diminish and stabilize the resistivity of the printed conductive films.

Studies on Silver Accumulation and Nanoparticle Synthesis By Cochliobolus lunatus

Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. Biological systems provide a useful option to achieve this objective. In this study, potent fungal strain was selectively isolated from soil samples on silver supplemented medium, followed by silver tolerance (100-1,000ppm) test. The isolated fungus was subjected to morphological, 18S rRNA gene sequencing and phylogenic studies and confirmed as Cochliobolus lunatus. The silver accumulation and nanoparticle formation potential of wet cell mass of C. lunatus was investigated. The accumulation and nanoparticle formation by wet fungal cell mass with respect to pH change was also studied. The desorbing assay was used to recover accumulated silver from cell mass. C. lunatus was found to produce optimum biomass (0.94g%) at 635ppm of silver. Atomic absorption spectroscopy study showed that at optimum pH (6.5 ± 0.2), cell mass accumulates 55.6% of 100ppm silver. SEM and FTIR studies revealed that the cell wall of C. lunatus is the site of silver sorption, and certain organic groups such as carbonyl, carboxyl, and secondary amines in the fungal cell wall have an important role in biosorption of silver in nanoform. XRD determined the FCC crystalline nature of silver nanoparticles. TEM analysis established the shape of the silver nanoparticles to be spherical with the presence of very small-sized nanoparticles. Average size of silver nanoparticles (14nm) was confirmed by particle sizing system. This study reports the synthesis and accumulation of silver nanoparticles through reduction of Ag(+) ions by the wet cell mass of fungus C. lunatus.

A213 高周波熱プラズマを用いた多ホウ化物ナノ粒子の合成(OS-3:プラズマを活用した熱工学の新技術(1))

RF thermal plasma was used to prepare nano-sized boron-rich compounds and the mechanism of nanoparticle formation was investigated by estimating the homogeneous nucleation rate. In order to synthesize aluminum dodecaboride (AlB_<12>), the premixed feed powders in different compositions of aluminum and boron were injected into the thermal plasma operated in different working gas conditions. High boron-ratio and thermal conductive helium were favorable to enhance AlB_<12> synthesis in final product due to higher boiling point of boron than aluminum. In the nanoparticle synthesis process, vaporized raw materials in the high temperature region were rapidly cooled and nucleate in the plasma tail region with a steep temperature gradient. At this point it was predicted that boron nucleates first and then aluminum nucleates. Therefore, AlB_<12> is formed by condensation of aluminum to the boron nuclei.

Thiol-terminated polystyrene through the reversible addition–fragmentation chain transfer technique for the preparation of gold nanoparticles and their application in organic memory devices

This work focuses on the preparation of gold nanoparticles decorated with well-defined polystyrene (PS) for PS-based thin nanocomposite films. Reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene using dibenzyltrithiocarbonate (DBTTC) as a chain transfer agent (CTA) followed by a hydrolysis reaction produced a thiol end-capped PS. The polymer was successfully used as polymeric surface modifier in a two-phase gold nanoparticle (Au-NP) synthesis process, generating Au-NPs having average diameters ranging from 3 to 5 nm. The Au-NPs were incorporated into PS thin films to fabricate organic memory devices, exhibiting switching behaviors.

Room-temperature synthesis of gold nanoparticles &amp;#x2014; Size-control by slow addition

We report a simple and rapid process for the room-temperature synthesis of gold nanoparticles using tannic acid, a green reagent, as both the reducing and stabilising agent. We systematically investigated the effect of pH on the size distribution of nanoparticles synthesized. Based on induction time and zeta- potential measurements, we show that particle size distribution is controlled by a fine balance between the rates of reduction (determined by the initial pH of reactants) and coalescence (determined by the pH of the reaction mixture) in the initial period of growth. This insight led to the optimal batch process for size-controlled synthesis of 2-10 nm gold nanoparticles - slow addition (within 10 minutes) of chloroauric acid into tannic acid.

Rietveld Analysis of Iron Oxide Nanoparticles

A room temperature solution process for synthesis of Fe3O4 nanoparticles demonstrated. It is shown that the particle size can be controlled with low concentration of oleic acid. The structure of as grown particles using X-ray diffraction and Rietveld refinement are discussed. Fe3O4 samples showed reduction in particle size for decreased concentration of oleic acid employed during synthesis. The as grown nanoparticles were found to possess a preferential (311) orientation of the cubic phase. The X-ray diffraction and the Rietveld refinement confirm the inverse spinel structure of cubic phase of magnetite.

Quick Synthesis of Lipid−Polymer Hybrid Nanoparticles with Low Polydispersity Using a Single-Step Sonication Method

Lipid-polymer hybrid nanoparticle, consisting of a hydrophobic polymeric core and a lipid monolayer shell, represents a new and promising drug delivery platform that has shown controllable particle size and surface functionality, high drug loading yield, sustained drug release profile, and excellent in vitro and in vivo stability. These lipid monolayer-coated polymeric nanoparticles are typically fabricated through a modified nanoprecipitation method, which involves sample heating, vortexing, and solvent evaporation. Herein we report a new and fast method to synthesize lipid-polymer hybrid nanoparticles with controllable and nearly uniform particle size. Using a bath sonication approach, we demonstrate that the whole hybrid nanoparticle synthesis process can be completed in about 5 min compared with a few hours for previous synthesis approaches. The size and polydispersity of the resulting nanoparticles can be readily controlled by tuning the relative concentrations of individual building components. Colloidal stability tests of the synthesized hybrid nanoparticles in PBS buffer and serum show no signs of aggregation over a period of 5 days. The present method improves the production rate of the hybrid nanoparticles by near 20-fold while not compromising the physicochemical properties of the particles. This work may facilitate the bench-to-bedside translation of lipid-polymer hybrid nanoparticles as a robust drug nanocarrier by allowing for fabricating a large amount of these nanoparticles at high production rate.

An easy microwave-assisted process for the synthesis of nanostructured palladium catalysts and their use in the selective hydrogenation of cinnamaldehyde

An efficient and highly reproducible process for the microwave-assisted solvothermal synthesis of palladium nanoparticles has been carried out adopting mild reaction conditions and very short microwave irradiation times. Colloidal nanoparticles have straightforwardly been obtained by the direct irradiation of an ethanol solution of Pd(OAc) 2 in the presence of PVP (poly-N-vinyl-2-pyrrolidone) as capping agent. The “in situ” preparation of γ-Al 2O 3-supported catalysts has been conveniently carried out without the addition of PVP, leading to supported palladium nanoparticles with an average diameter of 5–8 nm and a narrow nanoparticle size distribution. These nanocatalysts have been characterized by UV–vis, TEM, XPS and SSA measurements and used as efficient catalysts for the chemoselective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde with selectivities up to 97% in hydrocinnamaldehyde at complete substrate conversion.

Synthesis, optical properties and growth process of In2S3 nanoparticles

Cubic beta-In(2)S(3) nanoparticles (NPs) have been synthesized by a simple and facile way, which is 6 nm in size. Absorption and emission spectra of In(2)S(3) NPs show obvious blue peak shift compared to band gap of bulk In(2)S(3), indicating the strong quantum size confinement effect. The fluorescence quantum yield of In(2)S(3) NPs is found to be 10%. During the synthesis process, the absorption spectra have no peak shift, which is responding to transition from valence band to the conduction band levels. This absorption spectra show that the nucleation and growth process of In(2)S(3) NPs is very quick. The PL lifetime spectra and time resolved spectra give two emission processes in In(2)S(3) NPs, which would be excitonic recombination and electron-hole recombination via defects levels. The blue shift of emission peaks show the emission process in In(2)S(3) NPs is from mainly electron-holes recombination via defects levels to excitonic recombination. The Stokes shift becomes smaller which is mainly contributed by blue shift of emission and smaller contribution from the UV-Vis absorption. The absorption and emission spectra show the size and crystallinity of In(2)S(3) NPs have no changes (HRTEM images provide enough proofs); however the surface-related defects changed greatly in the reaction process.