Nanoparticles: Implication of Ligand Choice on Surface Properties,Crystal Structure,and Magnetic Properties of Iron Nanoparticles (Part. Part. Syst. Charact. 3/2013)

The behavior of iron nanoparticles is heavily influenced by their highly reactive surfaces. A better understanding of organic ligand/particle interactions must be achieved in order to synthesize iron nanoparticles with magnetic saturations (σ _sat) equivalent to bulk iron. Even when synthesized using careful, air‐free chemistry techniques and ligands more weakly interacting than those often reported in the literature, the magnetic saturation of iron nanoparticles generally only approaches, but not equals, the magnetic saturation of bulk iron. Here, iron nanoparticles are synthesized using Schlenk line chemistry methods and two different weakly interacting ligands: 2,4‐pentanedione and hexaethylene glycol monododecylether. These particles have saturation magnetizations slightly lower than bulk iron, which is believed to be caused by interactions between the passivating ligands and the surface of the nanoparticles. Using X‐ray absorption fine structure studies, it is shown that oxidized species of iron exist at the nanoparticles’ surface and can be attributed to iron/ligand interaction. The percentage of oxidized species scales with the surface to volume ratio of the nanoparticles, and therefore appears limited to the nanoparticle surface. X‐ray absorption fine structure analysis also shows that the nanoparticles have an expanded crystalline lattice, which can further impact their magnetic properties.     

Uptake and Intracellular Fate of Peptide Surface‐Functionalized Silica Hybrid Magnetic Nanoparticles In Vitro

Recently, the use of nanomaterials as intracellular targeting tools for theranostics has gained heightened interest. Despite the clear advantages posed by surface‐functionalized nanoparticles (NPs) in this regard, limited understanding currently exists due to difficulties in reliably synthesizing NPs with surface functionalizations adequate for use in such applications, as well as the manner of analytics used to assess the cellular uptake and intracellular localization of these NPs. In the present study, two key surface functionalities (a nuclear localization sequence (NLS) and integrin‐ligand (cRGD)) are attached to the surface of multifunctional, silica hybrid magnetic nanoparticles (SHMNPs) containing a polyethylene glycol (PEG) polymer coating using a well‐described, reliable, and reproducible microreactor set‐up. Subsequent analytical interpretation, via laser scanning confocal, transmission electron and dark‐field microscopy, as well as flow cytometry, of the interaction of SHMNPs‐PEG‐cRGD‐NLS with macrophage (J774A.1) and epithelial (HeLa) cells shows internalization of the SHMNPs‐PEG‐cRGD‐NLS in both cell types up to 24 h after 20 μg mL^?1 exposure, as well as increasing aggregation inside of vesicles over this time period. The findings of this study show that by incorporating a variety of state‐of‐the‐art analytical and imaging approaches, it is possible to determine the specific effectiveness of surface peptide and ligand sequences upon multifunctional SHMNPs.     

Magnetic Properties of Nanoparticles of Antiferromagnetic Materials

Hyperfine Interactions - The magnetic properties of antiferromagnetic nanoparticles have been studied by Mössbauer spectroscopy and neutron scattering. Temperature series of Mössbauer...     

Colloidal Nanoparticles: Formation of Large 2D Arrays of Shape‐Controlled Colloidal Nanoparticles at Variable Interparticle Distances (Part. Part. Syst. Charact. 1/2013)

A method for the production of homogeneous layers of nanoparticles of arbitrary shape is presented. The method relies on a ligand exchange with a functionalized polymer and a subsequent self‐assembly of a thin film on the substrates. The interparticle distances in the layer can be adjusted by the length of the polymer. In the case of spherical particles, the approach yields quasi‐hexagonal structures; in the case of anisotropic particles, the minimum distance between adjacent particles is controlled. Regular arrangements of the nanoparticles covering areas of several square centimeters are achieved.     

稀磁ZnO纳米颗粒的生长和性能

利用Zn、Fe、Mn、Co的铜铁试剂盐为前驱体,胺为表面包裹剂,在200℃N2保护下生长了2%的过渡金属离子掺杂的ZnO稀磁纳米晶体,研究了纳米晶体的结构、形态、光学和磁学性能。所有ZnO纳米晶体均为近圆形的颗粒,晶体结构为六角纤锌矿结构,无其他氧化物相的析出,但过渡金属离子的掺入使纳米颗粒的尺寸增大。在掺杂纳米颗粒的吸收谱和发射谱中均可以观察到明显的激子吸收和发射峰,所有纳米颗粒在温度高于43K时只有顺磁性。     

Surface Modification of Magnetic Nanoparticles Using Gum Arabic

Magnetite nanoparticles were synthesized and functionalized by coating the particle surfaces with gum arabic (GA) to improve particle stability in aqueous suspensions (i.e. biological media). Particle characterization was performed using transmission electron microscopy (TEM) and dynamic light scattering (DLS) to analyze the morphology and quantify the size distribution of the nanoparticles, respectively. The results from DLS indicated that the GA-treated nanoparticles formed smaller agglomerates as compared to the untreated samples over a 30-h time frame. Thermogravimetric analyses indicated an average weight loss of 23%, showing that GA has a strong affinity toward the iron oxide surface. GA most likely contributes to␣colloid stability via steric stabilization. It was determined that the adsorption of GA onto magnetite exhibits Langmuir behavior.     

Protein Binding on the Surface of Magnetic Nanoparticles

Magnetic nanoparticles (MNPs) are widely used in the areas of biology and biomedicine. The interaction between MNPs and proteins plays a crucial role in the bioapplication of MNPs, and the binding affinity of protein–MNPs is the manifestation of this interaction. The binding affinity of some proteins with MNPs modified in various ways is determined by fluorescence quenching. The results show that the binding affinity depends on the properties of both the MNPs and the proteins. The higher the surface curvature of MNPs, the larger the MNP, and the higher the binding affinity. No significant difference is found in binding affinity between MNPs with different modification methods. For proteins, the binding affinity depends on the properties of individual proteins, such as the amino acid sequence, the native protein conformation in solution, the isoelectric point, and surface potential. In general, the binding affinity is higher for proteins with cysteine residues on the surface. In addition, pH affects the binding affinity between proteins and MNPs; positively charged proteins and lower pH are more suitable for MNP binding due to electrostatic forces.