Chemically-mechanically assisted synthesis of metallic and oxide nanoparticles in ambient conditions

Based on the redox principle of galvanic displacement reaction, active metal foils, including magnesium (Mg), aluminum (Al) and cobalt (Co), were creatively introduced as new heterogeneous reducing media and were successfully employed in the presence of sonomechanical assistance to produce metallic nanoparticles such as silver, copper, tin and metal oxides such as those of iron, cobalt and ruthenium. Various combinations were investigated to determine the optimum ion/foil pairings for dense and monodisperse colloids. A wide range of nanoscale metallic species can be achieved by this method given optimum combination of ion/foil pairing. This new strategy greatly enriches and extends the existing methods for metallic nanoparticles preparation.     

Surfactant assisted solvothermal synthesis of ZnO nanoparticles and study of their antimicrobial and antioxidant properties

This study demonstrated a solvothermal method of growth of three different morphologies of zinc oxide nanoparticles(ZnO NPs): i) flower-like nanorod and nanoflakes, ii) assembled hierarchical structure,and iii) nano granule. Oleic acid(C_(18)H_(34)O_2), gluconic acid(C_6H_(12)O_7) and tween 80(C_(64)H_(124)O_(26)) were used as surfactant/capping/reducing agent for the formation of different morphologies of nanoparticles.The as-synthesized ZnO NPs were characterized by different physicochemical techniques such as UV–vis(UV–vis) spectroscopy, X-ray diffraction(XRD), fourier transform infrared spectroscopy(FTIR), field emission scanning electron microscopy(FE-SEM), energy dispersive X-ray(EDX) analysis and dynamic light scattering(DLS) studies. Further, the antioxidant and antimicrobial activity of these nanostructures was evaluated. The antioxidant activity of these nanostructures was assessed via 2,2-diphenyl,1-1 picrylhydrazyl(DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)(ABTS) and H_2O_2 free radical scavenging activity. The in vitro antimicrobial activity of the obtained nanostructures was demonstrated against both gram negative(Escherichia coli) and gram positive(Staphylococcus aureus) bacterial genera.This study revealed antioxidant and antimicrobial properties of different structures of ZnO NPs suggesting their biomedical and industrial applications.     

Ionic liquid-induced synthesis of selenium nanoparticles

A simple wet chemical method has been used to synthesize selenium nanoparticles by the reaction of ionic liquid with sodium selenosulphate, a selenium precursor, in the presence of polyvinyl alcohol stabilizer, in aqueous medium. The method is capable of producing spherical selenium nanoparticles in the size range of 76-150 nm under ambient conditions. This is a first report on the production of nano-selenium assisted by an ionic liquid. The synthesized nanoparticles can be separated easily from the aqueous sol by a high-speed centrifuge machine, and can be re-dispersed in an aqueous medium. The synthesized selenium nanoparticles have been characterized by X-ray diffraction, energy dispersive X-ray analysis, differential scanning calorimetry and transmission electron microscopy techniques.     

Sonochemical assisted synthesis and spectroscopic characterization of Fe3+ doped ZnO diluted magnetic semiconductor

Fe³⁺ doped ZnO nanopowder has been synthesized by sonochemical assistance and characterized by different spectroscopic techniques. The structure, surface morphologies and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectrometer (PL) and ultraviolet–visible spectrophotometer. XRD reveals that Fe³⁺ ions enter into ZnO lattices without any secondary phases. SEM micrographs of prepared sample show that surface is rough and stone like structure with different sizes. PL studies of Fe³⁺ doped ZnO nanopowder exhibits ultraviolet and blue emission bands. Magnetometric measurements (vibrating sample magnetometer) indicate ferromagnetic behavior at room temperature. This observation is further confirmed by the EPR spectrum of Fe³⁺ doped ZnO at room temperature.     

Silver nanoparticles: Ultrasonic wave assisted synthesis, optical characterization and surface area studies

Silver nanoparticles have been successfully synthesized by the sonochemical route using sodium borohydride and sodium citrate as the reducing agents. The effect of the reducing agents on the particle size and morphology has been studied by carrying out the two reactions at the same ultrasound frequency (20 KHz). The strong reducing agent (NaBH₄) produced spherical silver nanoparticles of sizes 10 nm whereas sodium citrate led to much smaller silver nanoparticles of ~ 3 nm diameter. Powder X-ray diffraction studies reveal a high degree of crystallinity and monophasic silver particles. UV-Visible studies show the presence of a surface plasmon band at 405 nm. However the reflectance spectra give a broad band between 340 and 360 nm which is characteristic for the quasi-spherical silver nanoparticles. The specific surface area was found to be 2.6 and 13.1 m²/g and the pore radius was found to be 15.2 and 12.3 Å for silver nanoparticles obtained by the sodium borohydride and sodium citrate reduction respectively.     

Microwave assisted template synthesis of silver nanoparticles

Easier, less time consuming, green processes, which yield silver nanoparticles of uniform size, shape and morphology are of interest. Various methods for synthesis, such as conventional temperature assisted process, controlled reaction at elevated temperatures, and microwave assisted process have been evaluated for the kind of silver nanoparticles synthesized. Starch has been employed as a template and reducing agent. Electron microscopy, photon correlation spectroscopy and surface plasmon resonance have been employed to characterize the silver nanoparticles synthesized. Compared to conventional methods, microwave assisted synthesis was faster and provided particles with an average particle size of 12 nm. Further, the starch functions as template, preventing the aggregation of silver nanoparticles.     

Vinyl monomers-induced synthesis of polyvinyl alcohol-stabilized selenium nanoparticles

A simple wet chemical method has been developed to synthesize selenium nanoparticles (size 100-200 nm), by reaction of sodium selenosulphate precursor with different vinyl monomers, such as acrylamide, N,N′-dimethylene bis acrylamide, methyl methacrylate, sodium acrylate, etc., in aqueous medium, under ambient conditions. Polyvinyl alcohol has been used to stabilize the selenium nanoparticles. Average size of the synthesized selenium nanoparticles can be controlled by adjusting concentration of both the precursors and the stabilizer. Rate of the reaction as well as size of the resultant selenium nanoparticles have been correlated with the functional groups of the different monomers. UV-vis optical absorption spectroscopy, X-ray diffraction, energy dispersive X-rays, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy techniques have been employed to characterize the synthesized selenium nanoparticles. Gas chromatographic analysis of the reaction mixture established the non-catalytic role of the vinyl monomers, which were found to be consumed during the course of the reaction.     

Mechanochemical assisted synthesis of B4C nanoparticles

The present work reports on the preparation of boron carbide nanoparticles by the reduction of boron oxide with magnesium in the presence of carbon using the mechanochemical processing. The phase transformation and microstructure of powders during ball milling were investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that during ball milling the B₂O₃–Mg–C reacted with a self-propagating combustion mode producing MgO and B₄C compounds. To separate B₄C from the milled powder mixture, an appropriate leaching process was used. After leaching, the purified powder mixture was characterized using XRD and transmission electron microscope (TEM). XRD studies indicated that the prepared particles were single phase crystalline B₄C. Moreover, TEM studies showed the size of B₄C particles were ranging from 10 to 80 nm.     

Polyelectrolyte assisted silver nanoparticles synthesis and thin film formation

Silver nanoparticles were prepared by the reduction of silver salts with sodium borohydride and capped with a copolymer of styrene sulfonate and maleic monomers. The synthesized nanoparticles were then deposited on a glass substrate using the layer-by-layer deposition technique in alternance with polycationic poly(diallyl-dimethylammonium chloride) PDADMAC. The synthesis of the silver nanoparticles as well as the layer-by-layer deposition with PDADMAC was easily monitored by UV–Vis spectroscopy due to the strong plasmon absorbance at 400 nm of the silver nanoparticles. Our study shows that increasing the concentration ration between the co-polyelectrolyte and silver nitrate has a negative effect on the size distribution of the resulting silver nanoparticles. For the layer-by-layer assembly, the PSS-co-Maleic was found to be a good capping agent since it allows later the formation of uniform thin films when deposited with PDADMAC. A linear increase in absorbance as a function of the number of deposited layers was observed.     

Rapid synthesis and characterization of maghemite nanoparticles

Fe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe203-SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.     

Solution assisted laser ablation synthesis of discrete aluminum nanoparticles

Discrete aluminum nanoparticles with an average particle size of 21 nm have been prepared by laser ablation of a metallic aluminum target submerged in dry tetrahydrofuran in the presence of 0.001 M oleic acid as a stabilizing ligand. The particles display high solubility and minimal aggregation while the absence of oleic acid leads to highly aggregated particles and a broader particle size distribution. O/Al ratios obtained from EDS analysis suggest that the particles produced are primarily metallic aluminum with minimal oxide content.     

纳米二氧化铈的电化学制备与表征

在铈盐溶液中用电解的方法制备了CeO2 纳米粉体。X 射线衍射表明 ,所得产物为立方晶系CeO2 ;SEM分析表明 ,CeO2 纳米粒子呈球形 ,晶粒度约 10nm ;TEM分析表明 ,粒径分布均匀 ,粒子不发生团聚 ;电子衍射表明 ,CeO2 纳米粒子为多晶结构。实验探讨了溶液浓度、电流密度等因素对CeO2 质量和产量的影响     

Microwave-assisted synthesis and characterization of tin oxide nanoparticles

Tin oxide nanoplatelets (SnO) and nanoparticles (SnO₂) were prepared by microwave assisted technique with an operating frequency of 2.45 GHz. This technique permits to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystalline size was evaluated from XRD and found to range from 26 to 34 nm. SEM and TEM analyses showed that the nanoparticles present a platelet-like shaped particle or, a pseudo spherical morphology, after calcination at moderate temperature during which the phase transformation from SnO to SnO₂ takes place. Additional FT-IR, density and resistivity measurements were also presented.     

Silver nanoparticles in hyperbranched polybenzobisthiazole: synthesis and characterization

Silver (Ag) nanoparticles were successfully synthesized in hyperbranched polybenzobisthiazoles (HBPBZTs) matrices using a reductive technique. The synthesized Ag nanoparticles were characterized through different spectroscopic and analytical techniques, such as FTIR, XRD, TGA, TEM, UV-vis, and fluorescence spectra. The results showed that the synthesized Ag-HBPBZT nanocomposites exhibited excellent thermostability and the Ag nanoparticles represented face-centered cubic crystal structures. It was interesting that these nanoparticles were soluble in DMSO. The Ag nanoparticles prepared using amino and sulfydryl-terminated HBPBZT (hbp3) as template and stabilizer had smaller sizes, more regular shapes, and narrower size distributions than those prepared using hbpl and hbp2 as templates and stabilizers. The Ag-HBPBZT nanocomposites had UV-vis absorptions at approximately 341 nm to 361 nm which were attributable to the surface plasmon resonance of the Ag nanoparticles. These nanocomposites emitted a strong blue light in DMSO solution. The prepared Ag-HBPBZT nanocomposites are potentially useful in the area of blue light emission.     

Chemical synthesis and characterization of amorphous Fe-Ni-B magnetic nanoparticles

We have synthesized Fe-Ni-B amorphous nanoparticles by chemical reduction of the transition metal solution. A compositional study shows that the nominal Ni/Fe ratio is preserved. The new preparation method used yields a much higher boron composition than the one obtained traditionally by rapid quenching and other chemical synthesis previously reported. For all compositions, the size of the particles is about 2.1 nm diameter with a narrow log-normal distribution.     

Hydrothermal synthesis of zirconium oxide nanoparticles and its characterization

The paper presents the preparation and investigations of zirconium oxide (ZrO₂) nanoparticles that were synthesized by hydrothermal method. The products were characterized by means of powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-absorption spectroscopy and photoluminescence (PL) spectroscopy. The crystal structure was determined using X-ray diffraction. The morphology and the particle size were studied using (SEM) and (TEM). The spherical shaped particles were confirmed through the SEM analysis. The transmission electron microscopic analysis confirmed the formation of the nanoparticles with the particle size. The FT-IR and Raman spectrum ascertained the strong presence of ZrO₂ nanoparticles. The optical properties were obtained from UV–visible absorption spectrum and also PL emission spectrum. The dielectric constant and the dielectric loss were measured as a function of frequency and temperature.     

Riley oxidation: A forgotten name reaction for synthesis of selenium nanoparticles

A simple wet chemical method, involving reaction of acetone with selenium dioxide, has been developed, to synthesize polyvinyl alcohol-stabilized selenium nanoparticles. The method is capable of producing nanoparticles in the size range of about 100-300 nm, under ambient conditions. The synthesized nanoparticles can be separated easily from the aqueous sols by a high-speed centrifuge, and can be re-dispersed in aqueous medium by a sonicator. The effect of concentrations of selenium dioxide, acetone and PVA on the size of the selenium nanoparticles has been studied. The size of the selenium nanoparticles has been found to increase with increase in the reaction time as well as the concentration of selenium dioxide, while it decreases with increase in the concentration of the stabilizer, PVA. The synthesized selenium nanoparticles have been characterized by UV-visible optical absorption spectroscopy, X-ray diffraction, energy dispersive X-ray analysis, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy techniques.     

Silica SBA-15 template assisted synthesis of ultrasmall and homogeneously sized copper nanoparticles

The synthesis of spherical copper nanoparticles with extremely narrow size distribution by electroless copper deposition on mesoporous silica support is described. The materials were characterized by nitrogen sorption, transmission electron microscopy, x-ray diffractometry and Fourier transform infrared spectroscopy. The copper nanoparticles have a cubic crystalline structure and an average particle size of 5.5 +/- 0.8 nm. The copper nanoparticles are stable, without detectable oxidation or further agglomeration under ambient conditions even after months. These results demonstrate that electroless copper reduction can be conducted and constrained within the mesoporous silica framework, which pave the way for engineered mesoreactors.     

Surfactant assisted solid-state synthesis and gas sensor application of a SWCNT/SnO2 nanocomposite material

Although tin oxide has been the most widely investigated metal oxide material for gas detection, it suffers from the large resistance and high operating temperature. This could be overcome by hybridization with nanostructured carbon. In this work, tin oxide nanoparticles with ultrasmall sizes of 1-3 nm have been uniformly coated onto bundles of single-walled carbon nanotubes by a surfactant assisted solid state synthesis approach for the first time. Gas sensor properties of the as-synthesized nanocomposite material toward NO2 (from 5 to 60 ppm) are measured at 150 degrees C. Compared to the pure carbon tubes gas sensors, the nanocomposite gas sensor responds to NO2 in low concentrations with good linearity, high sensitivity, and fast recovery, while working at a relatively low temperature.     

Calcium carbonate nanoparticles: synthesis, characterization and biocompatibility

The synthesis of nanoparticles and their functionalization to effectively utilize them in biological applications including drug delivery is currently a challenge. Calcium carbonate among many other inorganic nanosized particles offers promising results for such applications. We have synthesized calcium carbonate nanoparticles using polymer mediated growth technique, where one of the ions bound within polymer matrix and the other diffuses and reacts to form desired compound. The synthesized nanoparticles are characterized using X-ray diffraction, Scanning Electron Microscopy and spectroscopic techniques such as Fourier-Transform Infra-red spectroscopy and UV-Vis spectroscopy. The diameter of the calcium carbonate nanoparticles is estimated to be 39.8 nm and their biocompatibility studies showed no significant induction of oxidative stress or cell death even at higher concentrations (50 microg) upon exposure to HeLa and LE cells. Here, we report that the synthesized calcium carbonate nanosized particles using polymer mediated growth technique are biocompatible and can be safely used for biomedical applications.