Shape and Control of Metallic Nanoparticles

A  new  and  novel  approach  for  the  green  synthesis  of  silver
nanoparticles  is  the  need  of  the  hour.  Use  of  plant  parts  for  the
synthesis of silver nanoparticles is ecofriendly, economic and cost
effective. In the present paper, silver nanoparticles were synthesized
using  aqueous  stem  extract  of Cassia  roxburghii DC  as  a  reducing
agent.  The  biosynthesized  AgNPs  were  characterized  by  various
spectral analysis like UV–Vis, FTIR, XRD, TEM and Zeta potential
measurement. UV–vis spectra showed maxima absorption peak at
432  nm.  XRD  and  TEM  analysis  revealed  AgNPs  to  be  facecentered, cubic structures spherical in shape with an average particle
size of 32-35 nm.
The synergistic antibacterial activity was evaluated against two Gram
positive,  two  Gram  negative  bacteria  and  four  fungi  with  fifteen
commercial antibiotics alone and antibiotics plus synthesized AgNPs.
Antioxidant  activity  of  AgNPs  was  evaluated  by  ABTS  and  FRAP
assay.  The  AgNPs  showed  synergistic  antibacterial  activity  even
better than some antibiotics and also good  antioxidant activity. The
results suggest that Cassia roxburghii stem could be exploited for the
fabrication  of  AgNPs  with  potential  therapeutic  application  in
nanomedicine especially against multi drug resistant microorganisms
which  are  cost  effective  and  ecofriendly  and  simple.  They  can  be
definitely used in cosmetics, medical and pharmaceutical applications

Nowadays, nanoelectroctronic, electro-nanotechnologies environmental friendly products become the roadmap in industry. Hence, nanoscale of reinforcement into lead-free solder becomes more popular rather than the micro size of reinforcement. In this paper, Cobalt nanoparticles-reinforced Sn-Ag-Cu composite solders were prepared by thoroughly blending 0.75 wt% of cobalt nanoparticles with near eutectic cement tended to suppress the growth of Cu 3Sn intermetallic layer. However, upon addition of Co nanoparticles, the growth of Cu6Sn5 was enhanced. The distribution of the Co nanoparticles was observed by the elemental mapping which was carried out by using electron micro probe analysis (EPMA) and transmission electron microscopy which equipped together with electron-dispersive X-ray spectroscopy (TEM-EDX). There was no Co detected in the Cu3Sn, it only presented in Cu 6Sn5. The interdiffusion coefficient was increased with the ageing temperature. Upon additionof Co nanoparticles, the interdiffusion coefficient for the formation of Cu3Sn intermetallic layer was reduced, but the interdiffusion coefficient for the formation of Cu 6Sn5 layer was increased. The activation energy for the formation of Cu3Sn was also increased with the Co addition.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5702678&tag=1

In this report a simple and eco-friendly biosynthesis of silver
nanoparticles using Pomegranate peel extract as the reducing agent
from 1 mM AgNO3 had been investigated. The formation of silver
nanoparticles was characterized by UV-Vis spectrum, Fourier
Transform Infrared Spectroscopy (FT-IR) and Scanning Electron
Microscopic (SEM) analysis. The UV-Vis spectra results show a
strong resonance centered on the surface of silver nanoparticles
(AgNPs) at 371 nm. The Fourier Transformation Infrared
Spectroscopy spectral study demonstrates pomegranate peel extract
acted as the reducing agent. The scanning electron microscopic
(SEM) analysis shows nanoparticles with the average particles size
ranges about 5-50 nm. Further the antibacterial activity of AgNPs
was evaluated against Staphylococcus aureus, Pseudomonas
aeruginosa and Escherichia coli pathogens. This route is rapid,
simple, without any hazardous chemicals as reducing or stabilizing
agents and economical to synthesize AgNPs.

Silver sintering is used for bonding of semiconductor dies to the substrate as part of a power module/device packaging. Power-module consisting inverters and converters are used to manage the electric drive systems in the hybrids and electric vehicles (HEVs).  Many  pressure-sintering tools and processes have been patented to produce reliable sintered silver joints for these power applications, and those invented by Siemens, Infineon Technologies, Danfoss, and Valtion (VTT) are analyzed based on the Theory of Inventive Problem Solving (TRIZ) framework. The level of inventiveness for each patent is evaluated, and respective function analysis is conducted to understand the interactions of the components in each sintering tool. This paper is expected to be useful to engineers who are interested in understanding the evolutionary patterns of a technical system especially silver sintering tools

This paper investigates the growth of intermetallics in Sn-3.8Ag-0.7Cu (SAC) solder with and without Co nanoparticle reinforcement. Co reinforced composite was prepared by mechanically mixing 0.5 wt% and 1.5 wt% Co nanoparticles respectively into Sn-3.8Ag-0.7Cu solder paste. The formation and growth of the intermetallic compounds (IMC) at the solder joint interface were evaluated after thermal aging at 150°C for up to 1008 hours. In the solder joint, Cu6Sn5 intermetallic was observed on Cu substrate, followed by Cu3Sn intermetallic formation between Cu 6Sn5 and Cu after prolonged aging. The thickness of both IMC increased linearly as a function of square root of aging time. The Co nanoparticle reinforcement tended to suppress the growth of Cu3Sn intermetallic layer. However, the total of IMC thickeness was almost the same for the specimen with or without Co nanoparticle reinforcement.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5270667

Some recent advances in catalysis by metals are reviewed illustrating the versatility of supported nanoparticles and their high potential to be major contributors to solve energetic or environmental issues of the ongoing century. Since the early structure sensitivity concept, progresses have brought new insights and guidelines on structure-reactivity relationships such as strain effects, the ring-capture model, the particle surface density effect, or the influence of crystallographic planes. These phenomena are proposed to play a key role in the catalytic cycle. Systematic studies are however still required to estimate their real relevance and their respective contributions according to the type of chemical reactions and of operating conditions.

As compared to petroleum diesel, biodiesel is more corrosive for automotive materials. Studies on the characterization of corrosion products of fuel exposed automotive materials are scarce. Automotive fuel system and engine components are made from different ferrous and non-ferrous materials. The present study aims to investigate the corrosion products of different types of automotive materials such as copper, brass, aluminum and cast iron upon exposure to diesel and palm biodiesel. Changes in fuel properties due to exposure of different materials were also examined. Degradation of metal surface was characterized by digital camera, SEM/EDS and X-ray diffraction (XRD). Fuel properties were examined by measuring TAN (total acid number), density and viscosity. Among the metal investigated, copper is found to be least resistant in biodiesel and formed comparatively more corrosion products than other metals. Upon exposure of metals in biodiesel, TAN number crosses the limit given by standard while density and viscosity remain within the acceptable range of limit.

http://www.sciencedirect.com/science/article/pii/S0360544212001211

Ablation of Ni targets in water by laser impact (532 nm, 40 mJ/pulse, 10 Hz and 8 ns duration) focused on massive samples (∼2 mm diameter) generates colloids with fine nanoparticles. The amount of metal released in the solution (measured by mass loss of the target or ICP) was found to increase first linearly with time, but slower after 8 min of impact. The size distribution of the nanoparticles thus produced was measured (by TEM) to be in the range 3–5.3 nm in diameter, with a tendency for the size to be smaller for larger number of laser shots. Actually, nickel oxide nanoparticles were produced, rather than nickel nanoparticles as it was shown by HRTEM. XPS photoemission measurements evidenced the presence of nickel oxide species on the crater of the nickel sample surface after laser ablation.

Since land is scarce in metropolitan locations, it's common for tall building to be erected in C form. With the use of software ETABS 2019, this study examines the features of wind-induced story displacement and story drift operating on tall Cshaped models, with and without shear wall. Also, empirical formulae are used for manual calculations and to obtain the wind force and designed wind pressure on C-shaped tall building using codal provisions of IS 875 (Part 3) : 2015, also its applicability has been validated by a case study. For tall C-shaped buildings, this study gives a comparative result on the effect of wind load on building, with & without shear wall on behalf of maximum story displacement and story drift.

Most wet-chemical methods that synthesize metal nanoparticles (NPs) of a particular size and desired shape include the use of a stabilizing surfactant, such as poly(vinylpyrrolidone) (PVP). The latter has the ability to prohibit and/or promote surface sites from participating in electrocatalytic reactions, i.e. the methanol oxidation reaction (MOR). In light of our recent findings that adsorbed PVP can enhance the MOR on Pt NPs, a strong effort was made herein to separate the NP surface orientation effect from that of surface-bound PVP. We report the in situ ATR-SEIRAS (attenuated total reflection-surface enhanced infrared reflection absorption spectroscopy) and electrochemical (EC) studies of MOR and CO oxidation reaction (COR) performed on PVP-free cubic and octahedral/tetrahedral (O/T) Pt NPs that were obtained using an adapted liquid phase UV photo-oxidation (UVPO) technique. Transmission electron microscope (TEM) images showed no observable changes of shape and size after the elimination of the PVP, while the integrity of the atomic surface structure was further confirmed by the orientation-dependent EC stripping analysis of irreversibly adsorbed adatoms, i.e. Bi and Ge. The MOR activity was enhanced by the preferential surface orientation of the O/T Pt NPs compared to commercial Pt black and the cubic Pt NPs. The in situ ATR-SEIRAS measurements showed that the PVP-free Pt NPs adsorbed more bridge-bound gaseous CO than those with residual PVP and the weakly hydrogen-bound interfacial water played an important role for the orientation dependent enhancement in MOR activity. Additionally, the findings of this work are coupled with previously published investigations regarding the influence that PVP exerts on the ultimate activity of the Pt NPs, i.e., the adsorbed PVP enhances further the MOR activity on the O/T but suppresses it on the cubic Pt NPs.

The aim of the experiments in this research was to produce a coated superparamagnetic iron oxide nanoparticle (SPION)
product that may be used as a contrasting agent for MRI. There are several methods that can be employed to coat SPIONs.
However, many of the current methods employ toxic organic solvents which can be difficult to remove from the product
solution. The encapsulation and characterization of SPIONs in Eudragit was done using a supercritical antisolvent system
(SAS) with ethanol as the solvent and supercritical carbon dioxide (SC-CO2) as the antisolvent. Particles of diameters less
than 200 nm were produced which had preserved superparamagnetic properties. An encapsulation efficiency of 70% was
achieved.

Gold is the chemical element with atomic number 79 and its symbol is Au (from the Latin aurum). It is a soft metal, yellow in color, due to the absorption of the wavelengths of blue from the incident light. Resistant to most chemical compounds, react only with aqua regia and with the cyanide ion. With mercury it forms an amalgam, but not a chemical compound. The human body naturally contains small amounts of gold. About 0.000000003% of body weight (0.2 mg / 70 kg of weight c.a.). Like most other oligominerals , most of this gold is found in the blood...

Purpose - The purpose of this paper is to investigate the effects of addition Co nanoparticles on the characteristic properties of Sn-3.8Ag-0.7Cu solder. Design/methodology/approach - Cobalt (Co) nanoparticles were added to Sn-Ag-Cu solders by thoroughly blending various weight percentages (0-2.0 wt%) of Co nanoparticles with near eutectic SAC387 solder paste. Blending was done mechanically for 30 min to ensure a homogeneous mixture. The paste mixture was then reflowed on a hot plate at 250 degrees C for 45s. The melting points of nanocomposite solder were determined by differential scanning calorimetry. Spreading rate of nanocomposite was calculated following the JIS Z3198-3 standard. The wetting angle was measured after cross-sectional metallographic preparation. Findings - No significant change in melting point of the solder was observed as a result of Co nanoparticle addition. The wetting angles of the solder increased with the addition of nanoparticles, while the spreading rate decreased. Although the wetting angle increased, the values were still within the acceptable range. Scanning micrograph observations revealed that the as-solidified microstructure of the composite solder was altered by the addition of Co nanoparticles. Microhardness of the solders slightly increased upon Co nanoparticles addition to SAC387. Originality/value - The paper demonstrates that a simple process like paste mixing can be used to incorporate nanoparticles into solder.

http://www.emeraldinsight.com/journals.htm?issn=0954-0911&volume=23&issue=1&articleid=1905669&show=pdf

Full Article Figures & data References Citations Metrics Reprints & Permissions Get access ABSTRACT Effect of sonication time on the synthesis of the CdS nanoparticles within the matrix obtained through the covalent functionalization of multiwall carbon nanotube (MWCNT) with maleic anhydride (MA) – 1-octene copolymer was investigated. Cadmium chloride and thiourea were used as the raw materials. MWCNTs used for the matrix were synthesized by Catalytic Chemical Vapor Deposition using Fe-Co/Al2O3 as the catalyst. The obtained nanostructures were characterized by FTIR, XRD, Raman spectroscopy, TEM, SEM, TG and UV-Vis spectroscopy. Electrophysical properties of the polymer nanocomposites obtained using different periods of time for sonication were comparably investigated. The average CdS particle diameter was between 3.9–7.9 nm as confirmed independently by TEM and XRD. UV-Vis spectroscopy revealed that the obtained nanostructures are appropriate base materials for making optical devices.

ZnS nanoparticles have been synthesized by the facile chemical route with a narrow size distribution in the MA/octene-1 copolymer matrix and effect of reaction time has been discussed. X-ray diffraction pattern confirms the pure cubic phase of ZnS with 5-7 nm average crystal sizes which are in good agreement with the AFM and UV-Vis measurements. Absorption spectra exhibit a strong blue shift from the bulk with the 3.98 eV optical band gap which clearly indicates the strong size confinement effect. Thermogravimetric analyses show increased thermal stability of the nanocomposite compared to the copolymer. The possible growth mechanism of the particles formation and stabilization has been discussed.

We predict general trends for surface segregation in a binary metal cluster based on the difference between the atomic properties of the constituent elements. Considering the attractive and repulsive contributions of the cohesive energy of an atom in a cluster, energetically most favorable sites for a guest atom on a pure metal cluster is determined. It is predicted that for adjacent elements in a row of the periodic table, the bimetallic system would be more stable if the component with smallest valence electron density is placed on the surface. On the contrary, for well separated components in the periodic table, the bimetallic cluster would be more stable if the component with the smallest core electron density is placed inside. Such chemical {\bf ordering trends} in the lowest energy configurations of Pt-Au, Pt-Pd and Pt-Ni binary alloy clusters are verified for their 561 atom systems through simulated annealing process. It is predicted that the Ir, Rh, Ni, Pd atoms would tend t...

Biodiesel is currently in regular use as an alternative fuel over conventional petroleum diesel. However, corrosion of automotive materials is one of the concerns related to biodiesel compatibility issues. In addition, auto-oxidation of biodiesel can also enhance the corrosiveness of biodiesel. The present study aims to investigate inhibition effect of ethylenediamine (EDA), n-butylamine (nBA), tert-butylamine (TBA) against corrosion of cast iron. Static immersion tests in biodiesel in the presence (100 ppm) and absence of different corrosion inhibitors were carried out at room temperature for 1200 hours. At the end of the test, corrosion characteristic was investigated by weight loss measurements and changes on the exposed metal surface. Fuels were analyzed by using TAN (total acid number) analyzer and FTIR in order to investigate the acid concentration and compositional characteristics respectively. Surface morphology was examined by digital photography and scanning electron microscope (SEM). Oxide layers were investigated by X-ray diffraction. Results showed that TBA was more effective corrosion inhibitor in reducing corrosion than others.

http://www.sciencedirect.com/science/article/pii/S0378382011002323

We developed a simple and efficient process, laser heating of nickel powder in ethanol, to produce carbon-encapsulated nickel microspheres. Long-pulse-width laser heated nickel powder suspended in pure ethanol into liquid droplets. In turn, the latter droplets became sphere-like, pyrolyzed surrounding ethanol and dissolved the produced carbon atoms. Because of their lower solubility in solid nickel, excess carbon atoms were then expelled from the metal core after solidification, thus forming graphite-like shells on the laser-modified Ni spheres. Hence, after pyrolysis the transformation of carbon was found to follow the dissolution-precipitation mechanism. The produced carbon-encapsulated nickel microspheres exhibited higher oxidation resistance compared with the initial nickel powder, while keeping their magnetic properties essentially unchanged.

The increasing use of silver nanoparticles (AgNPs) in consumer products raises the risk of human toxicity. Currently, there are no therapeutic options or established treatment protocols in cases of AgNPs intoxication. We demonstrated previously that thiol antioxidants compounds can reverse the cytotoxicity induced by AgNPs in Huh-7 hepatocarcinoma cells. Here, we investigated the use of N-acetylcysteine (NAC) against the systemic toxic effects of AgNPs (79.3 nm) in rats. Biochemical, histopathological, hematological, and oxidative parameters showed that a single intravenous injection of AgNPs (5 mg/kg b.w.) induced deleterious effects such as hepatotox-icity, potentially as a result of AgNPs accumulation in the liver. Treatment with a single intraperitoneal injection of NAC (1 g/kg b.w.) one hour after AgNPs exposure significantly attenuated all toxic effects evaluated and altered the bioaccumulation and release patterns of AgNPs in rats. The findings show that NAC may be a promising candidate for clinical management of AgNPs intoxication. ARTICLE HISTORY

Different shapes of Co-aggregates were synthesized via reduction of a Co salt (CoCl 2 Á6H 2 O) by chemical precipitation using glycerol, ethylene glycol and ethanol as solvents. The effect of solvent on the morphology, fcc or hcp phase-content and the magnetic properties of the synthesized samples were investigated. The Co-aggregates synthesized using glycerol have a dense spherical shape and high saturation magnetization (M S), whereas ethylene glycol leads to formation of flower-shaped spherical aggregates through loose packing of smaller plate-like particles which have a moderate M S value. When ethanol was used as a solvent, a dendritic (leaf like)-shape of the aggregates with the lowest M S value was obtained. The formation of the obtained morphology of the aggregates was explained based on the size of the solvent molecule, the viscosity of the solvent and the number of polar groups (–OH) present in the solvent molecules. The magnetic domain state and domain wall dynamics of all the Co-samples were investigated using 59 Co Internal Field Nuclear Magnetic Resonance (IFNMR) spectroscopy at RT and at 77 K. Through the IFNMR spectroscopy, the presence of gain boundaries, single domain particles and multi-domain particles/aggregates with domain walls associated with fcc and hcp phases were identified and quantified. We observed that the use of ethanol facilitates formation of a higher amount of hcp phase in the sample than the use of glycerol or ethylene glycol.

In situ electron microscopy is a tool which offers great promise for
studying the mechanisms responsible for nanoparticle growth. In
aqueous solution, the reduction of Pb2+ by the electron beam results
in the formation of lead nanoparticles. Here, we directly examined the
fundamental processes that influence the growth of lead nanoparticles
in solution using in situ transmission electron microscopy.
Lead nanoparticle growth was directly monitored at the molecular
level and followed the sequence of nucleation, Ostwald ripening, and
aggregative growth. The aggregative growth phase resulted in
macrostructures having micron-sized dimensions. Importantly, when
combined with quantitative measurements, our direct imaging results
suggested that the growth properties observed for lead nanoparticles
were unique in comparison to other metallic entities.

Uniform fine Co80Ni20 particles with diameters between 18 and 540 nm have been synthesized by polyol reduction of metallic salts. Their magnetic properties have been studied as a function of the particle size at 10 and
300 K. From the analysis of the experimental results at room temperature, a transition from polydomain structure to single-domain structure with the reduction of the particle size to around 40 nm is deduced. A considerable decrease of the saturation magnetization with respect to the bulk value has been found as the particle size decreases at both measuring temperatures. At low temperature, a strong increase of coercivity has been observed which is ascribed to an enhancement of the effective magnetic anisotropy induced by the surface layer.

Recently biodiesel, as an alternative fuel is getting more significance to replace diesel fuel completely or partially. However, corrosion of automotive materials in biodiesel is a major concern as this can reduce engine life. This study aims to investigate the corrosion behavior of mild steel at three different temperatures such as room temperature, 50 and 80 degrees C. Static immersion tests in B0 (diesel), B50 (50% biodiesel in diesel), B100 (biodiesel) were carried out for 1200 h. At the end of the tests, corrosion characteristic was investigated by weight loss measurements and changes of the exposed metal surface. Fuels were analyzed by using TAN analyzer and Fourier transform infrared spectroscopy (FTIR) in order to investigate the change in acidity and oxidation of fuel respectively upon exposure. Surface morphology was examined by optical microscope and scanning electron microscope equipped with energy dispersive spectroscopy. Corrosion products were detected by X-ray diffraction (XRD). Results showed that the corrosion of mild steel increases with increase of temperature. Upon exposure of biodiesel to mild steel at high temperature, the water content and oxidation products are increased. (C) 2011 Elsevier Ltd. All rights reserved.

We predict general trends for surface segregation in binary metal clusters based on the difference between the atomic properties of the constituent elements. The energetically most favorable site for a guest atom on a pure metal cluster is determined considering the attractive and repulsive contributions of the cohesive energy of an atom in the cluster. It is predicted that for adjacent elements in a period of the periodic table, the bimetallic system would be more stable if the component with smallest valence electron density is placed on
the surface. On the other hand, in bimetallic clusters built with elements of only one group, the trend to be in the volume (of the atomic component with smaller core density) will be higher for that cluster with atomic components most separated in the group. Such chemical ordering trends in the lowest energy configurations of Pt-Au, Pt-Pd, and Pt-Ni binary alloy clusters are verified for their 561 atom systems through a simulated annealing process. Some of our atomistic predictions are verified through quantum mechanical calculations.

Full Article Figures & data References Citations Metrics Reprints & Permissions Get access ABSTRACT Effect of sonication time on the synthesis of the CdS nanoparticles within the matrix obtained through the covalent functionalization of multiwall carbon nanotube (MWCNT) with maleic anhydride (MA) – 1-octene copolymer was investigated. Cadmium chloride and thiourea were used as the raw materials. MWCNTs used for the matrix were synthesized by Catalytic Chemical Vapor Deposition using Fe-Co/Al2O3 as the catalyst. The obtained nanostructures were characterized by FTIR, XRD, Raman spectroscopy, TEM, SEM, TG and UV-Vis spectroscopy. Electrophysical properties of the polymer nanocomposites obtained using different periods of time for sonication were comparably investigated. The average CdS particle diameter was between 3.9–7.9 nm as confirmed independently by TEM and XRD. UV-Vis spectroscopy revealed that the obtained nanostructures are appropriate base materials for making optical devices.