Size-dependent structural and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

Phase transitions and magnetic properties of shape-memory materials can be tailored by tuning the size of the constituent materials,such as nanoparticles.However,owing to the lack of suitable synthetic methods for size-controlled Heusler nanoparticles,there is no report on the size dependence of their properties and functionalities.In this contribution,we present the first chemical synthesis of size-selected Co-Ni-Ga Heusler nanoparticles.We also report the structure and magnetic properties of the biphasic Co-Ni-Ga nanoparticles with sizes in the range of 30-84 nm,prepared by a SBA-15 nanoporous silicatemplated approach.The particle sizes could be readily tuned by controlling the loading and concentration of the precursors.The fractions and crystallite sizes of each phase of the Co-Ni-Ga nanoparticles are closely related to their particle size.Enhanced magnetization and decreased coercivity are observed with increasing partide size.The Curie temperature (Tc) of the Co-Ni-Ga nanoparticles also depends on their size.The 84 nm-sized particles exhibit the highest Tc (≈ 1,174 K) among all known Heusler compounds.The very high Curie temperatures of the Co-Ni-Ga nanoparticles render them promising candidates for application in high-temperature shape memory alloy-based devices.     

Synthesis of gold nanoparticles of variable morphologies using aqueous leaf extracts of Cocculus hirsutus

Spherical, triangular (prismatic) and square plate shaped gold nanoparticles have been synthesised from HAuCl₄?·?3H₂O solution using the aqueous leaf extract of Cocculus hirsutus. Nanoparticles are characterised using higher resolution transmission electron microscope, X-ray diffraction and UV–Vis absorption spectroscopic study. FT-IR analysis reveals that the gold nanostructures are mostly stabilised by the carbonyl and amide groups present in the active component of C. hirsutus leaf extract. Formation of gold nanostructures of variable morphologies has been explained due to slow reduction of gold ions by the mild reducing ascorbic acid present within the extract and this controlled reduction assists the preferential deposition of Au atom on different lesser-protected faces of initially grown gold nanostructure.     

合成工艺对水相合成金纳米颗粒的影响

分别采用柠檬酸三钠和硼氢化钠为还原剂在水相中还原氯金酸制备了稳定的金纳米溶胶。通过透射电子显微镜、激光粒度分析仪、紫外-可见分光光度计对所制备的金纳米颗粒的形貌、结构、粒度分布以及光学特性进行表征,研究了还原剂用量、加热反应时间、反应温度、pH值对水相制备金纳米颗粒的影响。结果表明通过调节合成工艺,可以实现金纳米颗粒的可控生长,制备出平均粒径在5～70nm粒度分布均匀的球形金纳米颗粒。     

Sodium niobate particles with controlled morphology synthesized by hydrothermal method and their use as templates in KNN fibers

Sodium niobate – NN (NaNbO₃) powders were synthesized by hydrothermal process to be used as template particles in the fabrication of textured lead free piezoelectric ceramics. Sodium hexaniobate–Na₈Nb₆O₁₉⋅13H₂O particles with rod-like morphology were synthesized at 120 °C. Particles with needle-like morphology and Na₂(Nb₂O₆)(H₂O) phase started to form at temperatures of 130 °C and above. Synthesis at 150 °C yields particles with totally needle-like morphology and consisting entirely of the Na₂(Nb₂O₆)(H₂O) phase. Sodium niobate–NaNbO₃ particles with cubic morphology were synthesized at temperatures of 160 °C and above. Rod-like and needle-like morphology was retained even after annealing at 400 °C for 1 h. A preliminary study was also done to integrate these anisometric template particles in the preparation of textured potassium sodium niobate (KNN) fibers.     

Synthesis of high magnetic moment CoFe nanoparticles via interfacial diffusion in core/shell structured Co/Fe nanoparticles

We report the synthesis of high magnetic moment CoFe nanoparticles via the diffusion of Co and Fe in core/shell structured Co/Fe nanoparticles. In an organic solution, Co nanoparticles were coated with a layer of Fe to form a Co/Fe core/shell structure. Further raising the solution temperature led to inter-diffusion of Co and Fe and formation of CoFe alloy nanoparticles. These nanoparticles have high saturation magnetization of up to 192 emu/g CoFe and can be further stabilized by thermal annealing at 600 °C. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. These two authors made an equal contribution to the work.     

Silver nanoparticles enhance Pseudomonas aeruginosa PAO1 biofilm detachment

Objectives: Silver nanoparticles (AgNPs) with a size ranging from 7 to 70?nm were synthesized using the ascorbic acid-citrate seed-mediated growth approach at room temperature.

Methods: The 8?nm silver particles were prepared using gallic acid in alkaline conditions and used as seed to prepare AgNPs.

Results: The presence of ascorbic acid and citrate allows the regulation of size and size distribution of the nanoparticles. The increase in free silver ion-to-seed ratio (Ag⁺/Ag⁰) resulted in changes of particle shape from spherical to pseudo-spherical and minor cylindrical shape. Further, a repetitive seeding approach resulted in the formation of pseudo-spherical particles with higher polydispersity index and minor distributions of tetrahedral particles. Citrate-capped AgNPs were stable and did not agglomerate upon centrifugation. The effect of AgNPs on biofilm reduction was evaluated using static culture on 96-well microtiter plates. Results showed that AgNPs with the smallest average diameter were most effective in the reduction of Pseudomonas aeruginosa biofilm colonies, which accounted for 90% of removal.

Conclusion: The biofilm removal activities of the nanoparticles were found to be concentration-independent particularly for the concentration within the range of 80–200?µg/mL.     

Direct synthesis of monodispersed ZnO nanoparticles in an aqueous solution

Monodispersed ZnO nanoparticles with mesopores were successfully prepared via a simple route through the transformation of Zn(NH₃)₄²⁺ precursor in the presence of sodium oleate and hydrazine at 80 °C with the pH of 8.5. Hydrazine and sodium oleate were used to control the size at 30-60 nm and to improve dispersion properties of ZnO nanoparticles. The samples were characterized by TEM, XRD, IR and TG-DTA, and the results suggest that the grains are composed of ZnO and a small quantity of oleate. The oleate plays an important role in preventing the ZnO nanoparticles from aggregating.     

Size-controllable synthesis of calcium carbonate nanoparticles using aqueous foam films as templates

A new method for the synthesis of calcium carbonate nanoparticles using two types of foam which are separately stabilized by surfactants with opposite change has been described here. In detail, one type of foam is formed by the aqueous solution of CaCl₂ which contains the anionic surfactant alkyl polyoxyethylene alcohol sulfate sodium (AES) and the other is formed by the aqueous solution of Na₂CO₃ and the cationic surfactant alkyl polyoxyethylene quaternary ammonium chloride (AEAC). Two types of foam contact each other in a specially designed apparatus after draining completely, then Ca²⁺ and CO₃²⁻ entrapped by the surfactant layers at the thin borders between the foam bubbles react and result in the generation of CaCO₃ nanoparticles. TEM determination showed that perfect mono-dispersed spherical nanoparticles were obtained and the size of particles can be conveniently controlled by changing the concentration of CaCl₂ and Na₂CO₃. Also, the mechanism leading to the synthesis of CaCO₃ nanoparticles was discussed in detail.     

酚醛树脂为前驱体制备多孔碳泡沫材料

以液态酚醛树脂为前驱体,正戊烷为发泡剂,吐温80为匀泡剂,在高压釜中通过卸压发泡的方法制备了酚醛树脂泡沫,然后将其经1000℃碳化后得到碳泡沫.研究结果表明,所得的典型碳泡沫样品是一种以无定形碳结构为主的轻质多孔碳材料,密度约为0.15g/cm3.碳泡沫的微结构可以通过调节卸压速率而得到有效控制,当卸压速率为0.05MPa/min时,可以得到孔洞相互贯穿、平均孔径约为300μm且分布较为均匀、接点完好,韧带光滑的多孔碳泡沫.     

Comparison of antibacterial activity of Ag nanoparticles synthesized from leaf extract of Parthenium hystrophorus L in aqueous media and Gentamicin sulphate: in-vitro

Monodisperse silver (Ag) nanoparticles were synthesized by using Parthenium hystrophorus L leaf extract in aqueous media. The synthesized nanoparticles were characterized by using UV-vis spectrophotometer, X-ray diffracto-meter (XRD), transmission electron microscope (TEM), and dynamics light scattering (DLS). Size-dependent antibacterial activities of Ag nanoparticles were tested against Gram negative Pseudomonas aeruginosa and Gram positive Staphylococcus aureus. Ag nanoparticles having 20?±?2?nm size in diameter show maximum zone of inhibition (23?±?2.2?mm) in comparison to 40?nm and 70?nm diameter nanoparticles for Pseudomonas aeruginosa. The zone of inhibition against Staphylococcus aureus were 19?±?1.8?mm, 15?±?1.5?mm and 11?±?1?mm for 20?nm, 40?nm, and 70?nm, respectively. In addition, affect of concentration of 20?nm size Ag nanoparticles on Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus species were also reported and results were compared with 10?µg/ml dose of Gentamicin sulphate. The Parthenium hystrophorus L leaf extract capped 20?±?2?nm Ag nanoparticles (7.5?µg/ml) shows statistically significant antibacterial activity than Gentamicin sulphate (10?µg/ml) against Staphylococcus aureus.     

One-step high-yield aqueous synthesis of size-tunable multispiked gold nanoparticles

Multispiked gold nanoparticles are required in large quantities for many fundamental studies and applications like (bio)sensing, but their preparation in high yield by the bottom-up chemical synthetic method is challenging. A water-based, non-'seed-mediated', straightforward method for the synthesis of gold nanoparticles with well-developed surface spikes is reported here. The yield of multispiked gold particles is very high (>90%). The method allows the tuning of the number and size of the spikes and the overall size of the particles, and hence the localized surface plasmon resonances of the particles over the broad spectral range in the visible and near-infrared. A mechanism for the evolution of twinned, sharp-tipped surface protrusions has been proposed based on systematic spectrophotometric and transmission electron microscopic studies, which were employed to elucidate the morphological features, structure, chemical composition, and optical properties of the multispiked gold nanoparticles.     

A novel direct reduction method to synthesize ordered Fe-Pt alloy nanoparticles

In this work, a direct green solid-phase reduction method for the fabrication of large yield of ordered phase Fe-Pt alloy nanoparticles was reported, in which inorganic salts were used as metal precursors and H₂-containing atmosphere was used as reducer. Utilizing this method, the composition and chemical ordered phase, such as L1₂-Fe₃Pt, L1₂-FePt₃, and L1₀-FePt phases can be easily achieved by one step reaction. The synthesized nanoparticles have clean surface because no organic precursors, no organic solutions or organic surfactants/ligands were used. Their magnetic performance and the formation mechanism of Fe-Pt alloy nanoparticles were also investigated. This strategy can be applied to synthesize many other types of alloy nanoparticles with desired composition and necessary crystal structure, which can be used for a variety of practical applications, such as in magnetism and catalyst research fields.     

纳米Au在蒙脱石层间的插层组装

以Na基蒙脱石为载体,分别以十二胺和PAA作为插层剂,利用此类插层剂可以捕捉金胶体的特点,使预先制备的金胶体插层于蒙脱石的层间制备组装型纳米金催化剂,并考察了高温焙烧对插层效果的影响。此外,以Au(en2)Cl3作为金的前驱体,研究了利用蒙脱石的阳离子交换特性直接进行纳米金插层组装的可行性。采用X射线衍射(XRD)、荧光分析(XRF)和透射电子显微镜(TEM)对所制备的样品进行了表征,结果表明:基于阳离子交换插层的制备方法未能实现纳米金的插层组装,金颗粒主要负载于蒙脱石片层的外表面,而基于配位俘获机理的插层组装方法所制备的纳米金在蒙脱石层间的插层组装效果良好,高温焙烧虽然导致层间纳米金的迁移,但金的粒径仍然保持在较低的尺寸范围。     

Effectivity of copper and cadmium sulphide nanoparticles in mitotic and meiotic cells of Nigella sativa L. (black cumin) – can nanoparticles act as mutagenic agents?

The present investigation deals with wet chemical preparation and characterisation of copper (Cu) and cadmium sulphide (CdS) nanoparticles (NPs) (using UV–visible spectra, Fourier transform infra-red scattering, X-ray diffraction, dynamic light scattering, field emission scanning electron microscopy and transmission electron microscopy) and their effectivity on mitotic and meiotic cells of Nigella sativa L. (Ranunculaceae) in comparison to ethyl methanesulphonate (EMS) and gamma irradiations. The objective of the study is to foresee whether Cu- and CdS-NPs can induce similar type of chromosomal aberrations as that of EMS and gamma irradiations, or not. Dry seeds of N. sativa (2n = 12) are exposed to Cu- and CdS-NPs (0.25, 0.50 and 1.0 µg/ml; 3 and 6 h), EMS (0.25, 0.50 and 1.0%; 3 and 6 h) and doses of gamma irradiations (25, 50, 100, 200 and 300 Gy). Cu-NPs (range: 25.7 to 120.4 nm; 33.2 nm ± 9.6) and CdS-NPs (range: 29.4 to 115.7 nm; 37.8 nm ± 10.7) are both cubical to spherical in shape. NPs are found to induce similar responses as that of the studied conventional mutagens, in relation to physiological and chromosomal (mitotic and meiotic) attributes. Uptake of Cu- and CdS-NPs in seedlings is also studied using atomic absorption spectroscopy. Results suggest that Cu- and CdS-NPs can act as mutagenic agent, a pioneer report of its kind.     

Removal of lead ions in aqueous solution by hydroxyapatite/polyurethane composite foams

We have prepared hydroxyapatite/polyurehthane (HAp/PU) composite foams with two different HAp contents of 20 and 50 wt.% and investigated their removal capability of Pb2+ ions from aqueous solutions with various initial Pb2+ ion concentrations and pH values of 2-6. HAp/PU composite foams synthesized exhibited well-developed open pore structures which provide paths for the aqueous solution and adsorption sites for Pb2+ ions. With increasing the HAp content in the composites, the removal capability of Pb2+ ions by the composite foams increases owing to the higher adsorption capacity, whereas the removal rate is slower due to the less uniform dispersity of HAp in composite foams. The removal rate of Pb2+ ions is also slower with increasing the initial Pb2+ ion concentration in aqueous solutions. The removal mechanism of Pb2+ ion by the composites is varied, depending on the pH value of aqueous solution: the dissolution of HAp and precipitation of hydroypyromorphite is dominant at lower pH 2-3, the adsorption of Pb2+ ions on the HAp/PU composite surface and ion exchange reaction between Ca2+ of HAp and Pb2+ in aqueous solution is dominant at higher pH 5-6, and two removal mechanisms compete at pH 4. The equilibrium removal process of Pb2+ ions by the HAp/PU composite foam at pH 5 was described well with the Langmuir isotherm model, resulting in the maximum adsorption capacity of 150 mg/g for the composite foam with 50 wt.% HAp content.     

Bio-directed synthesis of gold nanoparticles using Ananas comosus aqueous leaf extract and their photocatalytic activity for LDPE degradation

A bio-directed synthesis of gold nanoparticles (Au NPs) was developed via the reduction of hydrogen tetrachloroaurate (III) (HAuCl₄·3H₂O) solution by the aqueous leaf extract of Ananas comosus. The polyphenol stabilized Au NPs were characterized by UV–visible, Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD)/selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. The HRTEM images revealed that Au NPs were well dispersed with spherical structures. The size ranges from 7.39 to 32.09 nm with average particle size of 18.85 ± 6.74 nm. The peaks of XRD analysis at (2θ) 37.96°, 44.06°, 64.54°, 77.50° and 81.73° were respectively assigned to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of the face-centered cubic (fcc) lattice of gold. The photocatalytic potential of Au NPs was studied through the solid-phase degradation of low-density polyethylene (LDPE) film. The photoinduced degradation of LDPE@Au nanocomposite film was higher than that of the pure LDPE film. The weight loss of LDPE@Au (1.0 wt%) nanocomposite film steadily increased and reached 51.4 ± 4.8% in 240 h under solar light irradiation, compared to the photo-induced LDPE with only 8.6 ± 0.7%. However, LDPE film with 1.0% Au NPs gave a weight loss value of 4.72 ± 0.71 under the dark condition at the end of 240 h. Thus, LDPE film with 1.0% Au NPs showed a degradation efficiency of 90.8% under solar irradiation after 240 h. The sustainability of the nanoparticles was confirmed through reusability in the photocatalytic degradation reaction up to five consecutive cycles without substantial loss in its catalytic performance.     

Effect of eggshell powder as nucleating agent on the structure,morphology and functional properties of normal corn starch foams

Corn starch and eggshell powder (with particle sizes of 4–5µm and 8–10µm) composite foams were prepared by extrusion. Effects of eggshell on the structure, morphology, physical properties (unit density and expansion ratio), mechanical properties (spring index and compressibility) and thermal behaviour (thermal transition and stability) of the foams were investigated. Foam cell size decreased and cell population increased with addition of eggshell into starch matrix. The foam unit density, expansion ratio and compressibility decreased significantly (p < 0.05), while the spring index increased significantly (p < 0.05) as the eggshell content increased from 0 to 6wt%. Further increasing eggshell content to 10wt% increased the unit density and compressibility and decreased the expansion ratio and spring index. The thermal transition and stability increased with the addition of eggshell. The optimum eggshell content was 6wt% and the smaller‐sized eggshell powder had a favourable effect on the functional properties of the foams. Copyright © 2006 John Wiley & Sons, Ltd.     

Mosquito-larvicidal efficacy of gold nanoparticles synthesized from the seaweed,Turbinaria ornata (Turner) J.Agardh 1848

Malaria is considered a dreadful mosquito-borne infectious disease of human beings caused and spread by biting of the female mosquito Anopheles stephensi infected with a parasitic protozoan Plasmodium falciparum. Continuous application of chemicals/synthetic insecticides for vector control causes various problems such as resistant mechanism of mosquito, toxicity to nontarget aquatic organisms and disturbance to the microbial community of the soil. Currently, green synthesized nanoparticles are being employed in various biological processes including insect and pest control. The present investigation focused on the mosquito-larvicidal property of Turbinaria ornata-mediated gold nanoparticles (To-AuNPs) and its boiled aqueous extract (To-AE) against the malarial vector A. stephensi. The recorded lethal concentration (LC₅₀ and LC₉₀) values (µg/ml) of To-AE and To-AuNPs against fourth instar larvae of A. stephensi were 37.77 and 159.55 and 12.79 and 78.70, respectively. The To-AuNPs were characterized through UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDX), zeta potential and dynamic light scattering (DLS) method. The presently synthesized gold nanoparticles through the single-step, eco-friendly method is a potentially effective mosquitocidal agent.     

Synthesis of iron oxide nanoparticles of narrow size distribution on polysaccharide templates

We report here the preparation of nanoparticles of iron oxide in the presence of polysaccharide templates. Interaction between iron (II) sulfate and template has been carried out in aqueous phase, followed by the selective and controlled removal of the template to achieve narrow distribution of particle size. Particles of iron oxide obtained have been characterized for their stability in solvent media, size, size distribution and crystallinity and found that when the negative value of the zeta potential increases, particle size decreases. A narrow particle size distribution with D ₁₀₀ = 275 nm was obtained with chitosan and starch templates. SEM measurements further confirm the particle size measurement. Diffuse reflectance UV-vis spectra values show that the template is completely removed from the final iron oxide particles and powder XRD measurements show that the peaks of the diffractogram are in agreement with the theoretical data of hematite. The salient observations of our study shows that there occurs a direct correlation between zeta potential, polydispersity index, bandgap energy and particle size. The crystallite size of the particles was found to be 30–35 nm. A large negative zeta potential was found to be advantageous for achieving lower particle sizes, owing to the particles remaining discrete without agglomeration.