Antibacterial and plant growth-promoting properties of novel Fe3O4/Cu/CuO magnetic nanoparticles

In this work, an Fe₃O₄/Cu/CuO (FC) antibacterial nano-agent was synthesized in a “one-pot” approach using copper sulfate and ferric chloride as raw materials, and it was studied using TEM, XRD, XPS, UV-vis, and VSM methods. The antibacterial activity and mechanism of FC were studied, using a commercially available Bordeaux mixture as a control. The effects of an FC on mung bean development and its toxicity to human mammary epithelial cells were also investigated. The results revealed that FC could break the cell walls of E. coli and S. aureus, quadrupling the antibacterial activity of the Bordeaux combination. Furthermore, it was shown that FC might improve the germination, root development, and chlorophyll content of mung bean seeds while being 1/8 as hazardous to human mammary epithelial cells as the Bordeaux combination. The as-prepared FC can replace the Bordeaux combination in the management of agroforestry pathogens.

In this work, an Fe₃O₄/Cu/CuO (FC) antibacterial nano-agent was synthesized in a “one-pot” approach using copper sulfate and ferric chloride as raw materials, and it was studied using TEM, XRD, XPS, UV-vis, and VSM methods.     

5-氟尿嘧啶磁性纳米粒的制备及性能

背景:磁性载药微粒在外加磁场作用下,能实现定向治疗作用,减少全身毒副作用,同时作为缓释载体,能减少药物的频繁给药,达到有效治疗目的.目的:制备5-氟尿嘧啶的磁性纳米粒,评价微球性能.方法:以海藻酸钠和壳聚糖作为壁材,5-氟尿嘧啶为模型药物,Span80为乳化剂,液体石蜡为分散介质,乳化-复凝聚法制备磁性纳米粒.并从外观、稳定性、磁响应性、结构、溶胀实验及体外释放实验等多方面考察纳米粒性能.结果与结论:所制5-氟尿嘧啶的磁性纳米粒形态良好,均匀圆整,分散性较好,粒径在100～300 nm,具有较好稳定性和磁响应性.考察Fe3O4用量的影响,发现随着Fe3O4用量的增加,磁响应性增强,但载药量下降.红外谱图说明微粒中包裹磁性物质Fe3O4,及5-氟尿嘧啶与壁材之间产生相互作用.将5-氟尿嘧啶磁性纳米粒分别浸渍在蒸馏水,0.9%NaCl溶液和磷酸盐缓冲液(pH=7.4)中,结果蒸馏水吸水速度最快且溶胀率最大,磷酸盐缓冲液(pH=7.4)吸水程度最小且溶胀率最小.微粒的缓释性能良好,50 h内释放的药物占总含药量的53.20%.     

Size-dependent magnetic and magnetothermal properties of gadolinium silicide nanoparticles

Gadolinium silicide (Gd₅Si₄) nanoparticles are an interesting class of materials due to their high magnetization, low Curie temperature, low toxicity in biological environments and their multifunctional properties. We report the magnetic and magnetothermal properties of gadolinium silicide (Gd₅Si₄) nanoparticles prepared by surfactant-assisted ball milling of arc melted bulk ingots of the compound. Using different milling times and speeds, a wide range of crystallite sizes (13–43 nm) could be produced and a reduction in Curie temperature (T_C) from 340 K to 317 K was achieved, making these nanoparticles suitable for self-controlled magnetic hyperthermia applications. The magnetothermal effect was measured in applied AC magnetic fields of amplitude 164–239 Oe and frequencies 163–519 kHz. All particles showed magnetic heating with a strong dependence of the specific absorption rate (SAR) on the average crystallite size. The highest SAR of 3.7 W g⁻¹ was measured for 43 nm sized nanoparticles of Gd₅Si₄. The high SAR and low T_C, (within the therapeutic range for magnetothermal therapy) makes the Gd₅Si₄ behave like self-regulating heat switches that would be suitable for self-controlled magnetic hyperthermia applications after biocompatibility and cytotoxicity tests.

Gadolinium silicide (Gd₅Si₄) nanoparticles prepared by surfactant-assisted ball milling exhibit a size-dependent reduction in magnetic ordering temperature and a high magnetothermal effect making them suitable for magnetic hyperthermia applications.     

Experimental and ab initio studies on the structural,magnetic, photocatalytic,and antibacterial properties of Cu-doped ZnO nanoparticles

Copper-doped ZnO nanoparticles with a dopant concentration varying from 1–7 mol% were synthesized and their structural, magnetic, and photocatalytic properties were studied using XRD, TEM, SQUID magnetometry, EPR, UV-vis spectroscopy, and first-principles methods within the framework of density functional theory (DFT). Structural analysis indicated highly crystalline Cu-doped ZnO nanoparticles with a hexagonal wurtzite structure, irrespective of the dopant concentration. EDX and EPR studies indicated the incorporation of doped Cu²⁺ ions in the host ZnO lattice. The photocatalytic activities of the Cu-doped ZnO nanoparticles investigated through the degradation of methylene blue demonstrated an enhancement in photocatalytic activity as the degradation rate changed from 9.89 × 10⁻⁴ M min⁻¹ to 4.98 × 10⁻² M min⁻¹. By the first-principles method, our results indicated that the Cu(3d) orbital was strongly hybridized with the O(2p) state below the valence band maximum (VBM) due to covalent bonding, and the ground states of the Cu-doped ZnO is favorable for the ferromagnetic state by the asymmetry of majority and minority states due to the presence of unpaired electron.

Magnetic, photocatalytic and antibacterial performance of ZnO NPs were enhanced as doped with Cu.     

Diluted magnetic semiconductor properties in TM doped ZnO nanoparticles

The hydrothermal method was used to create dilute magnetic semiconductor nanoparticles of Zn_1−xCo_xO (x = 0, 0.01, 0.05, 0.09). The effect of cobalt doping on the microstructure, morphological and optical properties of Zn_1−xCo_xO was also studied and the Co doping to host ZnO was confirmed from XRD and EDX analysis. The structural analysis showed that doping of cobalt into ZnO decreased the crystallinity, but the preferred orientation didn''t change. SEM analysis revealed that the cobalt dopant did not have a strong influence on the shape of the synthesized nanoparticles. No defect-related absorption peaks were observed in the UV-Vis spectra. The crystallinity of the doped samples was improved by high growth temperature and long growth time. Ferromagnetic behavior above room temperature was detected in co-doped ZnO nanoparticles. The ferromagnetic behavior increased with increasing Co (up to x = 0.05) doping. The ferromagnetic behavior declined when the Co content was further increased. Related research shows that doped ZnO nanoparticles have better dielectric, electrical conductivity, and magnetic properties than pure ZnO. This high ferromagnetism is usually a response reported for dilute magnetic semiconductors. These semiconductor nanoparticles were further used to designed spintronic based applications.

The enlarged central part M–H loop shows for the Co = 0.09 doped ZnO sample, the ferromagnetic (FM) behavior increased, i.e., a M_r of 0.2412 emu g⁻¹ with a H_c of 85 Oe.     

Tuning of spinel magnesium ferrite nanoparticles with enhanced magnetic properties

Monodispersed magnesium ferrite nanoparticles with enhanced magnetic properties were successfully fabricated by a simple solvothermal method without employing any templates, complex apparatus or techniques. The structure, morphology, composition, and magnetic properties of the products were tuned and characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy and vibrating sample magnetometry. The results show that the reaction time and temperature have an important influence on the morphology, composition, structure and particle size of the synthesized MgFe₂O₄ nanoparticles. Not only the size, size distribution, crystallization, but also the atomic ratio of Mg : Fe has a decisive effect on their magnetic properties. The MgFe₂O₄ magnetic nanoparticles synthesized at 180 °C for 12 hours have excellent dispersion, narrow size distribution, good crystallinity and a Mg : Fe atomic ratio of approximately 1 : 4.53 and an average particle size of 114.3 nm, thus the highest saturation magnetization of 67.35 emu g⁻¹. It provides a reliable synthesis method for the better application of spinel structure magnesium ferrite nanoparticles in the future.

Monodispersed magnesium ferrite nanoparticles with enhanced magnetic properties were successfully fabricated by a simple solvothermal method without employing any templates, complex apparatus or techniques.     

Correlating the effect of preparation methods on the structural and magnetic properties,and reducibility of CuFe2O4 catalysts

CuFe₂O₄ spinel oxide has attracted research interest because of its versatile practical applications, especially for catalysis. In this study, nanometre-sized CuFe₂O₄ particles were prepared by three different methods, including nanospace confinement in SBA-15, hard template removal, and sol–gel combustion. The relationship between structure, size, magnetic behaviour, and reducibility of the catalysts was further investigated by various advanced techniques. Samples prepared by impregnation and hard template removal show high surface area and small crystallite size with superparamagnetic behaviour. In contrast, the sol–gel sample exhibits ferromagnetic properties with a large crystallite size and low surface area. Although all samples present a tetragonal crystal structure, the distributions of Fe and Cu cations in tetrahedral and octahedral sites in the spinel structure are different. The reducibility results demonstrate that the supported CuFe₂O₄/SBA-15 shows the lowest reduction profile. These results could suggest that the synthesis method strongly affects the crystal properties and cation distribution in the spinel structure, microstructure, surface area and reducibility, which are among the most relevant physicochemical properties for the catalytic activity.

The preparation method plays an important role in the structural properties and catalytic performance of CuFe₂O₄ catalysts.     

High coercivity Pr2Fe14B magnetic nanoparticles by a mechanochemical method

Nd₂Fe₁₄B nanoparticles are widely used because of their outstanding hard magnetic properties. In fact, Pr₂Fe₁₄B has higher magneto-crystalline anisotropy than Nd₂Fe₁₄B, which makes Pr-Fe-B a promising magnetic material. However, the chemical synthesis route to Pr₂Fe₁₄B nanoparticles is challenging because of the higher reduction potential of Pr³⁺, as well as the complex annealing conditions. In this work, Pr₂Fe₁₄B nanoparticles were successfully synthesized via an efficient and green mechanochemical method consisting of high energy ball milling, annealing, and a washing process. Microstructural investigations revealed that the oxide precursors were uniformly wrapped by CaO and CaH₂, which formed an embedded structure after ball milling. Then, Pr₂Fe₁₄B powder was synthesized via a time-saving annealing process. The impact of the Pr₂O₃ content and the preparation conditions was investigated. The coercivity of the as-annealed powder with 100 wt% Pr₂O₃ excess is 18.9 kOe. After magnetic alignment, the coercivity, remanence, and maximum energy product were: 9.8 kOe, 78.4 emu g⁻¹, and 9.8 MGOe, respectively. The present work provides a promising strategy for preparing anisotropic Pr-Fe-B permanent magnetic materials.

Nd₂Fe₁₄B nanoparticles are widely used because of their outstanding hard magnetic properties.     

Shape-controlled synthesis of magnetic Fe3O4 nanoparticles with different iron precursors and capping agents

This paper describes a modified method to prepare monodisperse Fe₃O₄ magnetic nanoparticles with different shapes (cube, octahedron, and sphere). The shape of the magnetic nanoparticles could be conveniently controlled by changing the types of precursor/capping agent and concentration of capping agent. The prepared samples were characterized using scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry. Cubes and octahedra were formed using ferrous sulfate heptahydrate as an iron source, ethylene glycol as a solvent and potassium hydroxide (KOH) as a capping agent while spheres were formed by using ferric chloride hexahydrate as an iron source, ethylene glycol as a solvent and ammonium acetate as a capping agent. By varying KOH concentration (0.5 M, 1 M, 1.5 M, and 5 M), the shape was transformed from cubes to octahedra because octahedra are developed dominantly at higher concentration of KOH within the reaction mixture. The magnetic studies show superparamagnetic behavior for all samples at room temperature. The Fe₃O₄ nanoparticles show the magnetic saturation values of 87 emu g⁻¹, 85 emu g⁻¹, and 82 emu g⁻¹ for spheres, cubes, and octahedrons, respectively.

This paper describes a modified method to prepare monodisperse Fe₃O₄ magnetic nanoparticles with different shapes (cube, octahedron, and sphere).     

Investigation of the structural,optical, elastic and electrical properties of spinel LiZn2Fe3O8 nanoparticles annealed at two distinct temperatures

Nanoparticles of Li_0.5ZnFe_1.5O₄ (LiZn₂Fe₃O₈) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures. X-ray diffractograms and Rietveld refinement confirmed the formation of the spinel structure. The morphology was analyzed by electron microscopy, which showed that the grains were composed of different crystallites. Elastic properties were determined from infrared spectroscopy. It was found that the elastic parameters increased with the increase in annealing temperatures. The band gap depends on the annealing temperature and it decreased on increasing the particle size. The conductivity of the specimen annealed at 500 °C followed either the Jonscher''s model or Drude''s model depending on the temperature range. This conductivity decreased when the annealing temperature was raised by 600 °C. AC conductivity was found to be controlled by the hopping model. A single relaxation phenomenon was evidenced for each sample from impedance analysis. The Nyquist diagram proved that the samples were simultaneously capacitive and resistive and also supported the presence of multiple relaxation times.

Nanoparticles of Li_0.5ZnFe_1.5O₄ (LiZn₂Fe₃O₈) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures.     

Resistive switching effect and magnetic properties of iron oxide nanoparticles embedded-polyvinyl alcohol film

In this study, the memory device of iron oxide (IO) nanoparticles (NPs) embedded in polyvinyl alcohol (PVA) demonstrates the bipolar resistive switching characteristics under an external electric field. The phase and magnetic properties of iron oxide nanoparticles change corresponding to its resistive states. At the high resistance state (HRS) of device, iron oxide nanoparticles are primarily in Fe₂O₃ phase and the ferromagnetism behavior is observed. In contrast, the iron oxide nanoparticles clustered by the bridging oxygen vacancies lead to mainly Fe₃O₄ phase and no hysteresis magnetic curve is observed at the low resistance state (LRS) of device. The results reveal that oxygen vacancies/ions in nanoparticles notably influence the resistance and magnetic behavior of nanocomposite thin films. Our study indicated that the magnetic NPs is high potential of multi-dimensional storage fields.

Bipolar resistive switching behavior of iron oxide nanoparticles embedded into polyvinyl alcohol matrix.     

SiO2/Ni核壳结构纳米粒子的制备及其磁性

背景:包覆层的存在能够阻止纳米粒子氧化、晶体长大、腐蚀和团聚,并赋予特殊的性能.目的:制备SiO2/Ni核壳结构纳米粒子,并评估复合粉体的磁性能.设计、时间及地点:观察性实验,于2005-11/2006-03在大连理工大学纳米复合材料研究实验室完成.材料:应用直流电弧等离子体法制备纳米镍粉,硅酸钠由天津市石英钟厂霸州市化工分厂生产.方法:以硅酸钠为主要原料,通过液相沉淀法在纳米镍粉表面包覆了一层SiO2.主要观察指标:应用X射线衍射仪、傅里叶红外光谱仪、透射电镜、振动样品磁强计、热重分析仪等对复合粉体的结构、形貌和磁性能进行检测.结果:SiO2以非晶态的形式包覆在纳米镍粒子表面,形成了核壳结构,降低了纳米粉体的团聚现象.经SiO2包覆后纳米镍粉氧化温度由287℃提高到385℃.磁性分析结果表明,粉体包覆前由于表面氧化层(NiO)的存在,粉体的磁滞回线偏移;包覆后的粉体由于SiO2的存在,饱和磁化强度降低,矫顽力升高.结论:成功制备了SiO2/Ni核壳结构纳米粒子,SiO2的包覆提高了纳米粉体的抗氧化性,且纳米镍粉具有很好的铁磁性能,矫顽力升高.     

Structural,magnetic and hyperthermia properties and their correlation in cobalt-doped magnetite nanoparticles

Cobalt doped magnetite nanoparticles (Co_xFe_3−xO₄ NPs) are investigated extensively because of their potential hyperthermia application. However, the complex interrelation among chemical compositions and particle size means their correlation with the magnetic and heating properties is not trivial to predict. Here, we prepared Co_xFe_3−xO₄ NPs (0 ≤ x ≤ 1) to investigate the effects of cobalt content and particle size on their magnetic and heating properties. A detailed analysis of the structural features indicated the similarity between the crystallite and particle sizes as well as their non-monotonic change with the increase of Co content. Magnetic measurements for the Co_xFe_3−xO₄ NPs (0 ≤ x ≤ 1) showed that the blocking temperature, the saturation magnetization, the coercivity, and the anisotropy constant followed a similar trend with a maximum at x = 0.7. Moreover, ⁵⁷Fe Mössbauer spectroscopy adequately explained the magnetic behaviour, the anisotropy constant, and saturation magnetization of low Co content samples. Finally, our study shows that the relaxation loss is a primary contributor to the SAR in Co_xFe_3−xO₄ NPs with low Co contents as well as their potential application in magnetic hyperthermia.

The interrelation among chemical compositions, structure, and heating properties of cobalt doped magnetite nanoparticles (Co_xFe_3−xO₄ NPs) for their potential hyperthermia application.     

Revealing the structural and chemical properties of copper-based nanoparticles released from copper treated wood

Copper-based preservatives consisting of micronized and nanoscale copper particles have been widely used in applications for wood protection. The widespread use of these preservatives along with the potential release of copper-containing nanoparticles (Cu NPs) during the life cycle of treated wood, has raised concerns over the impacts on the environment and occupational exposure. Along with assessing the potential hazards of these materials, a critical step is determining the chemical and morphological characteristics of the copper species released from copper-treated wood. Therefore, a combination of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) was utilized to characterize and differentiate the released copper-containing particles based on their structures, sizing, and chemical properties. Airborne wood dust samples were collected during the abrasion and sawing of micronized copper (MC) treated wood in a laboratory testing system. Based on the signature Cu L_2,3 edge of EEL spectra, three different copper species (i.e., basic copper carbonate, copper, and copper–wood complex) were identified as major components of the embedded particles in wood dust. In addition, two types of individual Cu NPs consisting of basic copper carbonate and copper were identified. The variation of morphologies and chemical properties of copper-containing particles indicates the importance of copper–wood interactions to determine the formation and distribution of copper species in wood components. Our findings will advance the fundamental understanding of their released forms, potential transformation, and environmental fate during the life cycle.

A combination of analytical electron microscopy and electron energy loss spectroscopy enables effective speciation and characterization of airborne copper nanoparticles released from copper-treated wood.     

Temperature-dependent optical properties of CuFeO2 through the structural phase transition

Delafossite CuFeO₂ has recently attracted considerable attention because of its complex phase transitions and practical applications. A thorough understanding of the optical properties of CuFeO₂ is essential for its further exploration. In this paper, we investigated the temperature-dependent optical properties of CuFeO₂ single crystals through Raman scattering spectroscopy and spectroscopic ellipsometry. The room temperature Raman scattering spectrum exhibited six phonon modes at approximately 352, 509, 692, 1000, 1052, and 1171 cm⁻¹. Upon cooling across 11 K, which is the rhombohedral to monoclinic structural phase transition temperature, a softening of the E_g-symmetry 352 cm⁻¹ mode and a hardening of the A_1g-symmetry 692 cm⁻¹ mode were observed. Moreover, analysis of the temperature-dependent real part of the dielectric function and direct band gap revealed anomalies at 11 K. These results demonstrate a profound connection between the structural phase transition, lattice dynamics, and electronic structure of CuFeO₂ and provide key information for CuFeO₂-based device design and fabrication.

Delafossite CuFeO₂ has recently attracted considerable attention because of its complex phase transitions and practical applications.     

Face-to-Face and blended methods to improve oral competence in nursing students through simulation

Communication and interpersonal skills are relevant to the health professions, so it is important to promote these competencies at university. This research assesses the effectiveness of teaching oral competence through simulation using face-to-face and blended methods. A public speaking workshop was conducted in a group of 144 first year nursing students. Three groups were obtained according to the teaching method (Group 1: traditional method-3 sessions, Group 2: traditional method-2 sessions, Group 3: blended method-2 sessions). Public speaking confidence was measured at the beginning and end of the training, and oral competence was assessed at the end. As a result, all groups achieved a good level of oral competence after the training. However, while students in Group 1 showed greater oral competence, with regard to confidence in public speaking, students in Group 1 showed significantly worst results than those in Group 3. We concluded that simulation is a useful strategy to improve cognitive learning, and behavioural and practical competencies such as public speaking. As for the teaching method, although blended learning did not offer better results than traditional learning, it seems useful provide there is at least one face-to-face session so that the student can perform a speech and receive corrective feedback.     

Silica coated iron nanoparticles: synthesis,interface control,magnetic and hyperthermia properties

This work provides a detailed study on the synthesis and characterization of silica coated iron nanoparticles (NPs) by coupling Transmission Electronic Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and magnetic measurements. Remarkably, iron NPs (of 9 nm of mean diameter) have been embedded in silica without any alteration of the magnetization of the iron cores, thanks to an original protocol of silica coating in non alcoholic medium. Tuning the synthesis parameters (concentration of reactants and choice of solvent), different sizes of Fe@SiO₂ composites can be obtained with different thicknesses of silica. The magnetization of these objects is fully preserved after 24 h of water exposure thanks to a thick (14 nm) silica layer, opening thus new perspectives for biomedical applications. Hyperthermia measurements have been compared between Fe and Fe@SiO₂ NPs, evidencing the self-organization of the free Fe NPs when a large amplitude magnetic field is applied. This phenomenon induces an increase of heating power which is precluded when the Fe cores are immobilised in silica. High-frequency hysteresis loop measurements allowed us to observe for the first time the increase of the ferrofluid susceptibility and remanence which are the signature of the formation of Fe NPs chains.

A novel method has been developed for the silica coating of iron nanoparticles while preserving the magnetic properties.     

Cobalt,nickel and copper complexes with glycinamide: structural insights and magnetic properties

Ten new compounds of Co, Ni and Cu with glycinamide (HL = glycinamide): [Co(H₂O)₂(HL)₂]Cl₂ (1a), [Co(H₂O)₂(HL)₂]Br_1.06Cl_0.94 (1b), [Co(H₂O)₂(HL)₂]I₂ (1c), [Ni(H₂O)₂(HL)₂]Cl₂ (2a), [Ni(H₂O)₂(HL)₂]Br_0.94Cl_1.06 (2b), [Ni(H₂O)₂(HL)₂]I₂ (low and room temperature polymorph, 2c_LT and 2c_RT), [CuCl₂(HL)₂] (3a), [CuBr_1.3Cl_0.7(HL)₂] (3b) and {[Cu(HL)₂]₂[Cu₂I₆]}_n (3c), as well as glycinamide hydroiodide (H₂LI) and a new polymorph of glycinamide hydrochloride (β-H₂LCl) were prepared and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermal analysis (TG/DTA) and ESR spectroscopy. 1a, 1b, 2a and 2b are isostructural, as well as 1c and 2c_RT, while the Cu compounds (3a–c) have entirely different molecular structures. All investigated compounds are mononuclear with exception of the 1D coordination polymer 3c. Compound 3c contains copper ions in the mixed oxidation state Cu(i) and Cu(ii) with interesting magnetic properties. Paramagnetic behaviour was found in 1a, 1b, 3a and 3b. Temperature induced polymorphic transformation was observed in 2c. Compounds 1a and 3a showed moderate antiproliferative activity and selectivity toward the human breast tumor cell line MCF-7.

We report the crystal structures and magnetic properties of nine mononuclear complexes and one 1D coordination polymer containing Cu^II/Cu^I ions.     

磁性隐形阿霉素脂质体的制备及其对SKOV-3细胞影响初步研究

目的制备磁性隐形阿霉素脂质体,对其理化性质及其热疗后对SKOV-3细胞的影响进行评价。方法使用pH梯度法制备磁性隐形阿霉素脂质体,通过透射电镜观察其形态,通过紫外分光光度计测试其包封率,差示扫描量热仪测定其相变温度,MTT及流式细胞仪测定凋亡率。结果不同脂质体粒径在80-150nm间,包封率达到76%,相变温度为42.3℃,MTT及流式的结果均显示热疗对SKOV-3细胞的杀伤作用显著高于对照组。结论磁性隐形阿霉素脂质体包封率较高,粒径较小,对SKOV-3具有显著影响。