Microwave assisted nanoparticle surface functionalization

We introduce the input of microwave energy to elaborate a multimodal magnetic nanoplatform. This magnetic nanomaterial consists of superparamagnetic γFe(2)O(3) nanoparticles conjugated to hydroxymethylene bisphosphonate (HMBP) molecules with an amine function as the terminal group. The feasibility of such a process is illustrated by the coupling of Rhodamine B to the hybrid magnetic nanomaterial. Using a microwave we manage to have approximately a 50 fold increase in molecules per nanoparticle compared to conventional procedures. Moreover we show that the amount of Rhodamine on the nanoparticle surface could be tuned using various stoichiometric ratios. The presence of Rhodamine B on the nanoparticle surface provides an amphiphilic character to facilitate penetration into the cells.     

Antibacterial surfaces through dopamine functionalization and silver nanoparticle immobilization

Immobilization of silver nanoparticles on the dopamine functionalized polyimide (PI) films was carried out by photo-induced silver ion-reduction under atmosphere conditions. The dopamine has been successfully deposited on the PI surface in mild aqueous environments. The effects of pH, dopamine concentration and reaction time on the dopamine polymerization were investigated. The water contact angles of the poly(dopamine) functionalized PI films reduced remarkably in comparison with that of the pristine PI film. The chemical composition and structure of the UV-induced deposited-silver on the modified PI films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The topography of the modified PI films was investigated by scanning electron microscope (SEM). The deposited poly(dopamine) layer acted as binding sites for the silver ions. The silver-plated PI films showed good antibacterial activity due to that biofilm formation was inhibited on the polymeric surfaces in contact with bacteria.     

Controlled functionalization of graphene oxide through surface modification with acetone

The facile method to functionalize graphene oxide through surface modification with acetone was studied and improved. The resulting nanomaterials showed variable characteristics as the surface energy could be tailored according to the combination (proportion of H₂O to acetone) of mixed solvent under sonication. Stability test and contact angle measurement showed that the treated graphene oxide exhibited different dispersibility and wettability. SEM images of graphene oxide films corroborated the changes in chemical composition of the sheets. FT-IR, XPS, and TGA observation provided direct evidence for chemical composition changes occurred on the surface. The presence of alkyl chain could decrease the surface energy and obviously control the hydrophilicity of the graphene oxide sheets. These results will provide significant guidance for the study of graphene-based bio-materials and nano-composites.     

A new aluminum-based metal matrix composite reinforced with cobalt ferrite magnetic nanoparticle

A new composite with cobalt ferrite magnetic nanoparticle dispersed in an aluminum matrix has been prepared using the ball-milling technique followed by compaction and sintering. Our efforts were largely focused on investigating the contribution of cobalt ferrite to the enhancement of structural, mechanical and magnetic properties of aluminum. Incorporation of 1–10 weight (wt)% of nanosized cobalt ferrite into the aluminum matrix could affect remarkable change in mechanical properties. Enhancement of hardness value, elastic modulus, and compressive strength was observed in the case of cobalt ferrite-incorporated aluminum matrix as compared to the pure aluminum sample. Incorporation of cobalt ferrite could impart considerable improvement of magnetization value of the aluminum matrix with a saturation magnetization of 17.07 emu/g for the aluminum sample reinforced with 10 wt% of cobalt ferrite. A decrease in coercive force in the sample arising from the increase in surface effects and inter-particle interaction between the ferromagnetic cobalt ferrite and soft phases in the matrix was also observed.     

Triggered release from liposomes through magnetic actuation of iron oxide nanoparticle containing membranes

The ideal nanoscale drug delivery vehicle allows control over the released dose in space and time. We demonstrate that this can be achieved by stealth liposomes comprising self-assembled superparamagnetic iron oxide nanoparticles (NPs) individually stabilized with palmityl-nitroDOPA incorporated in the lipid membrane. Alternating magnetic fields were used to control timing and dose of repeatedly released cargo from such vesicles by locally heating the membrane, which changed its permeability without major effects on the environment.     

Enhanced separation of Toluene and Xylene through surface modified porous carbon matrix

Aromatics that are present in the feed of the Claus sulfur recovery process are well known to poison the catalyst and hence continued efforts are being made within the scientific community to remove them. In this context, the present work attempts to develop superior adsorbents in comparison with contemporary adsorbents for removal of toluene and m-xylene. In a bid to improve adsorption properties, nitrogen-containing surface functional groups were successfully introduced onto porous carbon by minimizing pore damage while maximizing nitrogen content. The surface modified adsorbents were subjected to gas phase adsorption of toluene and m-xylene at 45°C to generate the adsorption isotherms. Toluene adsorption capacity for the modified adsorbent was observed to have increased by approximately 30% at pressure of about 20 mbar and m-xylene by about 10% at about 22 mbar. Several orders of magnitude increase in adsorption capacity was observed for both aromatics at pressures less than 10 mbar. Such high adsorption capacity have not been reported in literature and could potentially favorably alter the economics of aromatics removal in gas processing. Regenerability of nitrogen doped adsorbent was ensured through cyclic adsorption/desorption tests. The adsorption isotherms as well as the kinetics of adsorption were modelled.     

Metal nanoparticle doped coloured coatings on glasses and plastics through tuning of surface plasmon band position

Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO₂, Au in mixed SiO₂-TiO₂ and SiO₂-ZrO₂, Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layer-by-layer (two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios.     

Method for analysis of nanoparticle hemolytic properties in vitro

Hemolysis (destruction of red blood cells) in vivo can lead to anemia, jaundice, and other pathological conditions; therefore the hemolytic potential of all intravenously administered pharmaceuticals must be evaluated. Nanotechnology-derived devices and drug carriers are emerging as alternatives to conventional small-molecule drugs, and in vitro evaluation of their biocompatibility with blood components is a necessary part of early preclinical development. The small size and unique physicochemical properties of nanoparticles may cause their interactions with erythrocytes to differ from those observed for conventional pharmaceuticals and may also cause interference with standardized in vitro tests. Separating true hemolytic responses from the false-positive or false-negative results caused by particle interference is important for correct interpretation of these tests. Here we describe validation of an in vitro assay for the analysis of nanoparticle hemolytic properties and discuss observed nanointerferences with the assay. We propose alternative methods to avoid misleading results from nanoparticles and discuss the potential relevance of nanoparticle in vitro hemolytic properties to in vivo systems.     

Transient magnetic birefringence for determining magnetic nanoparticle diameters in dense, highly light scattering media

The increasing use of biofunctionalized magnetic nanoparticles in biomedical applications calls for further development of characterization tools that allow for determining the interactions of the nanoparticles with the biological medium in situ. In cell-incubating conditions, for example, nanoparticles may aggregate and serum proteins adsorb on the particles, altering the nanoparticles' performance and their interaction with cell membranes. In this work we show that the aggregation of spherical magnetite nanoparticles can be detected with high sensitivity in dense, highly light scattering media by making use of magnetically induced birefringence. Moreover, the hydrodynamic particle diameter distribution of anisometric nanoparticle aggregates can be determined directly in these media by monitoring the relaxation time of the magnetically induced birefringence. As a proof of concept, we performed measurements on nanoparticles included in an agarose gel, which scatters light in a similar way as a more complex biological medium but where particle-matrix interactions are weak. Magnetite nanoparticles were separated by agarose gel electrophoresis and the hydrodynamic diameter distribution was determined in situ. For the different particle functionalizations and agarose concentrations tested, we could show that gel electrophoresis did not yield a complete separation of monomers and small aggregates, and that the electrophoretic mobility of the aggregates decreased linearly with the hydrodynamic diameter. Furthermore, the rotational particle diffusion was not clearly affected by nanoparticle-gel interactions. The possibility to detect nanoparticle aggregates and their hydrodynamic diameters in complex scattering media like cell tissue makes transient magnetic birefringence an interesting technique for biological applications.     

Measurement of surface topography of magnetic recording materials through computer analyzed microscopic interferometry

A recently developed surface characterization technique, Computer Analyzed Microscopic Interferometry, is shown to have many applications in the study of magnetic recording surfaces. Three-dimensional and quantitative interferometric images produce very high depth resolution without reducing the field of view. This allows very precise surface roughness and volume measurements.     

Use of magnetic nanoparticle heating in the treatment of breast cancer

Magnetic nanoparticles are promising tools for the minimal invasive elimination of small tumours in the breast using magnetically-induced heating. The approach complies with the increasing demand for breast conserving therapies and has the advantage of offering a selective and refined tuning of the degree of energy deposition allowing an adequate temperature control at the target. The biophysical basis of the approach, the magnetic and structural properties of magnetic nanoparticles are reviewed. Results with model targets and in vivo experiments in laboratory animals are reported.     

Electrocodeposition of magnetic nickel matrix nanocomposites in a static magnetic field

The effect of an external magnetic field on the electrocodeposition of composites consisting of either Co or magnetite nanoparticles in a Ni matrix has been studied. An alkaline Ni pyrophosphate bath containing citrate was used. The magnetic particles were prepared by thermal decomposition (Co) or chemical precipitation (magnetite) and characterized by transmission electron microscopy, X-ray diffraction, dynamic light scattering, zeta potential and vibrating sample magnetometry measurements. The particle incorporation showed a distinct dependency on the orientation of an externally applied magnetic field. While the particle incorporation increased in a perpendicular field (perpendicular with regard to the electrode surface), it decreased in a parallel orientation. This result is explained with the dominating action of the magnetophoretic force. The structure and the properties of the Ni layers were significantly affected by the particle codeposition. A refinement of the Ni grains was found with increasing plating current density and as a result of the nanoparticle incorporation. The magnetic hardness and the Vickers microhardness of the films increased significantly due to the incorporation of the nanoparticles.     

Effect of magnetic anisotropy on the mobility of the boundaries in thin magnetic films

This paper discusses the effect of magnetic crystallographic anisotropy on the mobility of the domain walls in thin magnetic films with an easy axis in the plane of the film. It shows that the stable configuration of a domain wall is a single-vortex Bloch domain wall. Besides this, there are two metastable states of the domain wall—a Néel domain wall and a domain wall with two magnetic vortices along the normal to the plane of the film. It is also shown that the mobilities of the single-vortex and Néel domain walls and the domain wall with two vortices decrease as the anisotropy constant increases and tend to the same value. Pis’ma Zh. Tekh. Fiz. 24, 42–46 (January 26, 1998)     

On the heat exchange between a probing nanoparticle and a surface through near-field modes of a fluctuational electromagnetic field

Heat exchange between a nanoparticle (representing the probe of a scanning microscope) and a solid surface in a range of distances from zero to several microns is considered in a relativistic approximation. It is shown that the role of the time lag increases with the conductivity of materials and the distance from particle to surface. The heat flux is always smaller than that obtained in the nonrelativistic approximation. Maximum heating is expected for high-resistivity materials.     

Ultrasonic assessment of extracellular matrix content in healing Achilles tendon

Although several imaging modalities have been utilized to observe tendons, assessing injured tendons by tracking the healing response over time with ultrasound is a desirable method which is yet to be realized. This study examines the use of ultrasound for non-invasive monitoring of the healing process of Achilles tendons after surgical transection. The overall extracellular matrix content of the transection site is monitored and quantified as a function of time. B-mode images (built from successive A-scan signatures) of the injury site were obtained and compared to biomechanical properties. A quantitative measure of tendon healing using the extracellular matrix (ECM) content of the injury site was analyzed using linear regression with all biomechanical measures. Contralateral tendons were used as controls. The trend in the degree of ECM regrowth in the 4 weeks following complete transection of excised tendons was found to be most closely paralleled with that of linear stiffness (R(2) = 0.987, p < .05) obtained with post-ultrasound biomechanical tests. Results suggest that ultrasound can be an effective imaging technique in assessing the degree of tendon healing, and can be used to correlate structural properties of Achilles tendons.     

Charge transport in cellular nanoparticle networks: meandering through nanoscale mazes

The transport of electrons through topologically complex two-dimensional Au nanoparticle networks has been investigated using a combination of low temperature (4.5 K) direct current I(V) measurements and numerical simulations. Intricate, spatially correlated nanostructured networks were formed via spin-casting. The topological complexity of the nanoparticle assemblies produces I(V) curves associated with nonlinearity exponents, zeta approximately 4.0. Simulations based on tunneling transport in sparse and inhomogeneous planar networks are used to elucidate the influence of topology on the value of zeta.