Levitation-jet synthesis of In-O nanoparticles with room-temperature ferromagnetic properties

Octahedral and roughly spherical In-In₂O₃ nanoparticles ranging in average particle size from 30 up to 300 nm were prepared by levitation-jet aerosol synthesis through condensation of metal indium vapor in helium gas flow with gaseous oxygen/air injection at ambient and reduced pressure. Scanning electron microscopy (SEM), X-ray diffraction (XRD), BET measurements, UV–vis, FT-IR, Raman, XPS, and vibrating-sample magnetometry (VSM) characterized the nanoparticles. Room-temperature ferromagnetism with maximum magnetization of up to 0.17 emu/g was recorded for the nanoparticles. The results indicate a predominant role of the actual microstructure on the nanoparticle properties. It is suggested that the observed ferromagnetic ordering may be related to intrinsic defects at the In/In₂O₃ interface structure of such a composite material. This suggestion is in good agreement with the results of optical and XPS experiments on the NPs.     

Reliable synthesis of bismuth nanoparticles for heavy metal detection

A reliable and facile pathway is described here for preparing high-quality bismuth nanoparticles. Combined with hydrothermal method and confined growing effect of polymer, bismuth nanoparticles with uniform size and shape were obtained with remarkable productivity. The nanoparticles is proved to be pure Rhombohedral structure Bi crystals with R-3m space group and the diameter of the nanoparticles is about 80 nm with a quite narrow particle size distribution. Those bismuth nanoparticles were predicted to grow from a rolling process by sheet-like Bi nanocrystal intermediates. The obtained bismuth nanoparticles were used to prepare modified electrode for the detection of Cd²⁺ and Pb²⁺ in water solution by stripping analysis. Compared with naked glassy carbon electrodes, the modified electrode showed two obvious responses at −0.85 V and −0.62 V, corresponding to the reduction process of Pb²⁺ and Cd²⁺ and this well-resolved stripping response can be observed when the concentration is as low as 10 μg/L, indicating potential application in electroanalysis for environmental inspection.     

Rapid synthesis of Ag@Ni core-shell nanoparticles using a microwave-polyol method

Mixtures of AgNO₃ and NiSO₄·6H₂O, NiCl₂·6H₂O, or Ni(NO₃)₂·6H₂O were reduced in ethylene glycol (EG) in the presence of NaOH and poly(vinylpyrrolidone) (PVP) under microwave (MW) heating for 10 min. Then, we succeeded in the synthesis of Ag core-Ni shell nanoparticles, denoted as Ag@Ni, in high yield. The formation of Ag@Ni particles was confirmed using energy dispersed X-ray spectroscopic (EDS) measurements and selected area electron diffraction (SAED) patterns. The growth mechanism of Ag@Ni is discussed. The UV-Vis spectra of Ag@Ni were similar to those of Ni particles.     

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.     

Rapid and continuous hydrothermal synthesis of metal and metal oxide nanoparticles with a microtube-reactor at 523 K and 30 MPa

A flow-through apparatus with a microtube-reactor has been developed for rapid and continuous hydrothermal synthesis. Heat-up time of starting solution to 523 K is within 0.08 s and this promises rapid nucleation of nanoparticles compared with conventional batch reactor. Continuous production of Ag, Fe₂O₃, TiO₂, and ZrO₂ particles from metal salts aqueous solution was performed at 523 K and 30 MPa with the reactor. Nanoparticles having an average particle size and a coefficient of variation less than 5.4 nm and 0.22 could be continuously obtained.     

Rapid microwave-assisted synthesis of dextran-coated iron oxide nanoparticles for magnetic resonance imaging

Currently, magnetic iron oxide nanoparticles are the only nanosized magnetic resonance imaging (MRI) contrast agents approved for clinical use, yet commercial manufacturing of these agents has been limited or discontinued. Though there is still widespread demand for these particles both for clinical use and research, they are difficult to obtain commercially, and complicated syntheses make in-house preparation unfeasible for most biological research labs or clinics. To make commercial production viable and increase accessibility of these products, it is crucial to develop simple, rapid and reproducible preparations of biocompatible iron oxide nanoparticles. Here, we report a rapid, straightforward microwave-assisted synthesis of superparamagnetic dextran-coated iron oxide nanoparticles. The nanoparticles were produced in two hydrodynamic sizes with differing core morphologies by varying the synthetic method as either a two-step or single-step process. A striking benefit of these methods is the ability to obtain swift and consistent results without the necessity for air-, pH- or temperature-sensitive techniques; therefore, reaction times and complex manufacturing processes are greatly reduced as compared to conventional synthetic methods. This is a great benefit for cost-effective translation to commercial production. The nanoparticles are found to be superparamagnetic and exhibit properties consistent for use in MRI. In addition, the dextran coating imparts the water solubility and biocompatibility necessary for in vivo utilization.     

Aniline as a stabilizer for metal nanoparticles

Palladium nanoparticles were synthesized by two different methods, i.e. reflux and γ-radiolysis in the presence of various monomers like aniline, N-ethyl aniline, N-methyl aniline, o-anisidine and o-toluidine as the stabilizing agent for the Pd nanoparticles. UV–Visible spectral analysis reveals that the aniline renders best stability to the Pd nanoparticles up to a period of 96 h. Nanocomposites were synthesized by polymerizing aniline stabilized Pd° nanoparticle solution by using ammonium persulphate as an oxidizing agent. The average particle size of the nanoparticles calculated from X-ray diffraction patterns were ∼24 nm (reflux method) and ∼28 nm (γ-irradiation method). The above results are supported by TEM analysis.     

Controlled self-assembly of metal-organic frameworks on metal nanoparticles for efficient synthesis of hybrid nanostructures

We report a novel approach for synthesizing inorganic nanoparticle/metal-organic frameworks (MOFs) heterostructured nanocomposites by self-assembly of MOFs on nanoparticles. This approach involves the synthesis of Au nanoparticles and preferential growth of [Cu(3)(btc)(2)](n) frameworks consisting of Cu(2+) ions and benzene-1,3,5-tricarboxylate (btc) on nanoparticles. Aggregates consisting of 11-mercaptoundecanoic acid (MUA)-stabilized Au nanoparticles linked by Cu(2+) ions were necessary for preferential self-assembly of [Cu(3)(btc)(2)](n) frameworks on the aggregates, resulting in the formation of Au nanoparticles/[Cu(3)(btc)(2)](n) nanocomposites. The present approach was confirmed to be applicable for other hybrids consisting of Au nanoparticles and tetragonal [Cu(2)(ndc)(2)(dabco)](n) frameworks.     

Rapid synthesis of cubic Pt nanoparticles and their use for the preparation of Pt nanoagglomerates

We report the synthesis of hexadecyltrimethylammonium bromide (CTAB)-stabilized cubic Pt nanoparticles by NaBH4 reduction of H2PtCl6 in aqueous CTAB solution. These Pt nanoparticles (average size of 7 nm) were well dispersed in aqueous solution and stable at least for 2 months. Addition of a trace amount of AgNO3 can alter the morphology of these Pt nanoparticles. More interestingly, the as-prepared uniform Pt nanoparticles were further developed into bigger Pt nanoagglomerates (approximately 20 to 47 nm) by a seed-mediate growth process. Dentritic and spherical Pt nanoagglomerates can be synthesized by altering the incubation time and their size can be tuned by controlling the amount of the seeds added.     

Rapid synthesis of highly stable silver nanoparticles and its application for colourimetric sensing of cysteine

A modified green approach for the synthesis of stable silver nanoparticles (AgNPs) using tea leaf extract is described. The method involves the reduction of silver salt by the polyphenols present in the green tea leaf extract and requires no additional capping/stabilising agents. Compared to other biogenic methods for the synthesis of AgNPs, the uniqueness of the approach described here lies in its simplicity, low-cost, and rapid synthesis rate; the reaction being completed within 10–15 min at room temperature. The reaction was carried out in alkaline medium without stirring and heating, and requires no special cleaning or drying of the glassware used. The synthesised AgNPs were characterised by UV–Vis spectroscopy and transmission electron microscopy (TEM). The results showed that AgNPs with a strong surface plasmon resonance peak around 410 nm and particle size in the 5–30 nm range were prepared. The synthesised AgNPs show excellent chemical stability for more than six months in aqueous solution. Additionally, we showed that the as-synthesised AgNPs can be used as highly selective colorimetric and optical sensors for the detection of cysteine. Thus, with a simple synthesis strategy, and enhanced stability, these green-tea-functionalised AgNPs have the potential for further applications as biosensors and antimicrobial agents.     

Multi-functional chitosan nanoparticles encapsulating quantum dots and Gd-DTPA as imaging probes for bio-applications

Chitosan was used to encapsulate both CdSe/ZnS quantum dots (QDs) and the magnetic resonance imaging (MRI) contrast agent gadolinium-diethylenetriaminepentaacetate (Gd-DTPA), forming multi-functional nanoparticles that can be used in a wide range of in vitro or in vivo studies as fluorescent biological labels as well as MRI contrast agents, respectively. Multi-color QDs at pre-determined molar ratios were encapsulated into chitosan nanoparticles to produce bar-coding fluorescent labels. The encapsulated QDs and Gd-DTPA still maintained their desirable optical properties and relatively high relaxivity, respectively. The chitosan nanoparticles also showed good aqueous stability and enhanced biocompatibility on myoblast cells.     

Gadolinium-doped silica nanoparticles encapsulating indocyanine green for near infrared and magnetic resonance imaging

Clinical applications of the indocyanine green (ICG) dye, the only near infrared (NIR) imaging dye approved by the Food and Drug Administration (FDA) in the USA, are limited due to rapid protein binding, fast clearance, and instability in physiologically relevant conditions. Encapsulating ICG in silica particles can enhance its photostability, minimize photobleaching, increase the signal-to-noise (S/N) ratio and enable in vivo studies. Furthermore, a combined magnetic resonance (MR) and NIR imaging particulate can integrate the advantage of high-resolution 3D anatomical imaging with high-sensitivity deep-tissue in-vivo fluorescent imaging. In this report, a novel synthesis technique that can achieve these goals is presented. A reverse-microemulsion-based synthesis protocol is employed to produce 25 nm ICG-doped silica nanoparticles (NPs). The encapsulation of ICG is achieved by manipulating coulombic attractions with bivalent ions and aminated silanes and carrying out silica synthesis in salt-catalyzed, mildly basic pH conditions using dioctyl sulfosuccinate (AOT)/heptane/water microemulsion system. Furthermore, paramagnetic properties are imparted by chelating paramagnetic Gd to the ICG-doped silica NPs. Aqueous ICG-dye-doped silica NPs show increased photostability (over a week) and minimal photobleaching as compared to the dye alone. The MR and optical imaging capabilities of these particles are demonstrated through phantom, in vitro and in vivo experiments. The described particles have the potential to act as theranostic agents by combining photodynamic therapy through the absorption of NIR irradiated light.     

A room-temperature synthesis of titanium nitride hollow spheres

Titanium nitride hollow spheres were synthesized by the reaction of TiCl4 and NaNH2 at room temperature. X-ray powder diffraction (XRD) pattern could be indexed as cubic TiN with the lattice constants of a = 4.236 A. Transmission electron microscopy (TEM) images showed hollow spheres with diameter about 200 nm. A possible formation mechanism of TiN hollow spheres was discussed.     

Bio-inspired strategy for on-surface synthesis of silver nanoparticles for metal/organic hybrid nanomaterials and LDI-MS substrates

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety of two-?to three-dimensional material surfaces, utilizing polydopamine, an emerging surface modifying agent, is reported in this paper. This material-independent platform for AgNP synthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparing substrates for laser desorption-ionization time-of-flight mass spectrometry (LDI-ToF MS).     

Role of polyfunctional organic molecules in the synthesis and assembly of metal nanoparticles

The role of polyfunctional organic molecules in the synthesis of differently shaped metallic nanostructures and their assembly is investigated. These molecules could be used as spacer ligands and also for surface passivation of nanoparticles, especially with the objective of controlling their electronic and optical properties depending on their length scales. We investigate the role of several such molecules, such as 4-aminothiophenol, tridecylamine, Bismarck brown R and Y, mordant brown, fat brown, chrysoidin (basic orange), and 3-aminobenzoic acid in the synthesis and assembly of various nanoparticles of gold and silver. For example, the use of 4-ATP helps in the formation of rod shaped micelles in aqueous acetonitrile as confirmed by transmission electron microscopy (TEM) suggesting their role as soft templates. In addition, 4-ATP has also been used for the formation of heteroassembly of spherical nanoparticles of gold and silver at controlled pH. Significantly, triangular and hexagonal gold nanoplates are formed at room temperature by similar polyfunctional dye molecule, Bismarck brown R (BBR), while other analogous dye molecules give only arbitrary shaped gold nanoparticles. Further confirmation of their role in shape determination comes from linear amine molecules such as tridecylamine, which give only spherical nanoparticles both for silver and gold. In essence, our study confirms the role of various such organic molecules in shape controlled synthesis of nanoparticles. We also report optical and electrochemical properties of few of these nanostructures as a function of their shape.     

Facile synthesis of metal and alloy nanoparticles by ultrasound-assisted dealloying of metallic glasses

Metal and alloy nanoparticles synthesized by chemical reduction have attracted increasing attention due to their superior physical,chemical,and biological properties.However,most chemical synthesis processes rely on the use of harsh reducing agents and complicated chemical ingredients.Herein,we report a novel reduction-agent-free and surfactant(stabilizer)-free strategy to synthesize Cu,Ag,Au,Cu-Pt,Cu-Au,Cu-Au-Pt-Pd,and Au-Pt-Pd-Cu nanoparticles by ultrasound-assisted dealloying of Mg-based metallic glasses.The formation mechanism of the metal and alloy nanoparticles is revealed by a detailed investigation of sequential intermediate products.We demonstrate that the glass-liquid phase transition of the initially dealloying metallic glasses,together with the synergistic effect of dealloying and ultrasound-driven ligament-breakage of small enough nanoporous intermediates,play key roles in preparing the uniformly dispersed metal and alloy nanoparticles.This approach greatly simplifies the up-scaling synthesis of monometallic and bimetallic nanoparticles,and also provides a general strategy for synthesizing unprecedented multimetallic nanoparticles.     

High permittivity and microwave absorption of porous graphitic carbons encapsulating Fe nanoparticles

Porous graphitic carbons encapsulating Fe nanoparticles (PGCFs) were fabricated by infiltrating activated carbon (AC) with an iron salt and thereafter heat-treating the products in vacuum, and the electromagnetic parameters of the PGCF were investigated over 2–18 GHz frequency. The results demonstrated that the formation of porous graphitic network encapsulating Fe nanoparticles endowed the composite a very high permittivity and dielectric loss at 2–18 GHz. Return loss (RL) for the PGCF-based absorbers were investigated based on the measured electromagnetic parameters. A typical dual-layer absorber exhibited an excellent microwave absorption with a 43 dB maximum absorption at 10 GHz and a nearly 7 GHz bandwidth for RL < −20 dB.     

由有机和无机金属前躯体自蔓延高温合成碳包覆磁纳米粒子(英文)

介绍了一项由自蔓延高温合成(SHS)碳包覆磁纳米粒子的系统研究。采用还原剂NaN3和三种不同氧化剂-聚四氟乙烯、六氯乙烷和六氯苯,实施了SHS制备。研究了金属前躯体(Fe(CO)5或K3[Fe(CN)6])对产物的得率、反应热、形貌、结构和磁性能的影响。结果表明:有机铁前躯体和C2Cl6氧化剂反应体系可获得磁性最佳、得率最高的产物。     

Synthesis,structure, and room-temperature ferromagnetism of Ni-doped ZnO nanoparticles

In this paper, Ni-doped ZnO (Zn_1−x Ni _x O, in which 0 ≤ x ≤ 0.05) diluted magnetic semiconductors nanoparticles are prepared by an ultrasonic assisted sol–gel process. Transmission electron microscopy shows sphere-like nanoparticles with an average size of about 25 nm. From the analysis of X-ray diffraction, the Ni-doped ZnO nanoparticles are identified to be a wurtzite structure, but impurity phases are observed when the Ni content x reaches 0.05. Sample structures are further studied by Raman spectra, from which a broad and strong Raman band in the range of 500–600 cm⁻¹ is observed in Zn_1−x Ni _x O. With the increment of x, wurtzite structures degrade gradually. The magnetic properties are measured using superconducting quantum interference device at room temperature; the Zn_1−x Ni _x O (x ≤ 0.02) nanoparticles show ferromagnetism. However, for the sample of Zn_0.95Ni_0.05O, paramagnetism is observed, which may be ascribed to ferromagnetic–antiferromagnetic competition.