Magnetic properties of Cd(1 - x)Mn(x)Te/C nanocrystals.

Mn doped CdTe nanocrystals coated by carbon (Cd(1 - x)Mn(x)Te/C) were synthesized by a one-step, kinetically controlled solid state reaction under autogenic pressure at elevated temperatures. Electron microscopic analysis confirmed that the 40-52 nm Cd(1 - x)Mn(x)Te core was encapsulated by a 6-9 nm carbon shell. The efficient doping by Mn(2+) in the zinc blende Cd(1 - x)Mn(x)Te lattice, up to an atomic ratio of Mn/Cd of 0.031, was confirmed from electron paramagnetic resonance (EPR) experiments. In the case of higher doping, it is likely that manganese is partially expelled to the nanocrystal surface. All the doped samples exhibit ferromagnetism at room temperature. The lowest doped sample has the highest magnetic moment (1.91 ± 0.02 µ(B)/Mn). The more concentrated samples exhibit weaker ferromagnetic interactions, probably due to an incomplete coupling between carriers in the host CdTe semiconductor and dopant spins.

Strontium hexaferrite nanomagnets suspended in a cosmetic preparation: a convenient tool to evaluate the biological effects of surface magnetism on human skin.

BACKGROUND/PURPOSE: Magnetic therapy has been popular for ages, but its therapeutic abilities remain to be demonstrated. We aimed to develop a homogeneous, stable dispersion of magnetic nanoparticles in a skin-care preparation, as a tool to analyze the biological and physiological effects of superficial magnetism in skin. METHODS: SrFe(12)O(19) nanoparticles were generated by ultrasound, dispersed in glycerol, stabilized in Dermud cream and permanently magnetized. The magnetic cream was applied on the epidermis of human skin organ cultures. The effects on UV-induced cell toxicity, apoptosis and inflammatory cytokine expression were analyzed. A clinical test was performed to check skin moisturization. RESULTS: Nanomagnets were found to be homogenously and stably dispersed. After magnetization, the preparation generated a magnetic field of 1-2 G. Upon cream application, no cytotoxicity and no impairment of cellular vitality were found after 24 and 48 h, respectively. The anti-apoptotic and anti-inflammatory properties of Dermud were not modified, but its long-term effect on moisturization in vivo was slightly increased. CONCLUSION: Nanomagnetic Dermud cream can be used as a tool to analyze the biological effects of nanomagnets dispersed on the skin surface at the cellular and molecular levels, thus allowing to explore the possible therapeutic uses of superficial magnetism for skin care.

Sonochemical synthesis under a magnetic field: fabrication of nickel and cobalt particles and variation of their physical properties.

We report on the variation of the physical properties of nickel and cobalt nanoparticles prepared by using ultrasound irradiation as energy source. First, we describe a sonochemical method for preparing aggregated particles. Second, we interpret the results on the basis of Einstein's theory (1905), which deals with a mathematical expression for the diffusivity of particles into solvents. This theory explains the stability of organosols of nickel and cobalt nanoparticles in polyethylene glycol. Finally, the effect of applying an external magnetic field during sonochemical formation of both aggregated particles and their stable colloids is investigated.

Ta2O5 nanobars and their composites: synthesis and characterization.

Novel Ta2O5 nanobars anchored on micron-sized carbon spheres were synthesized by the thermal decomposition of pentaethoxy tantalate, Ta(OEt)5. This one-step reaction was carried out using the RAPET (Reaction Under Autogenic Pressure at Elevated Temperature) method by dissociating Ta(OEt)5 at 800 degrees C for 3 h. The as-prepared Ta2O5/C nanobar-composite was annealed under air at 500 degrees C for 3 h (eliminating the carbon spheres), resulting in neat Ta2O5 nanobars. The products, Ta2O5/C and Ta2O5 nanobars, were characterized using methods such as electron microscopy (SEM, TEM, HRTEM, SAEDS, EA, EDX) and Powder-XRD. Transmission electron microscope (TEM) images indicated the particle size of the Ta2O5 nanobars coated on 40-60 nm carbon spheres. The optical properties of the Ta2O5/C nanobar-composite and the neat Ta2O5 nanobars were determined by UV-vis absorption spectrometry and their band gaps were found at 265 (4.7 eV) and 260 nm (4.8 eV), respectively. A PL band was also observed for a Ta2O5/C nanobar-composite and Ta2O5 nanobars. The above results indicate that Ta2O5 nanobars have a promising application in optical devices.

Selective oxidation of CO in the presence of air over gold-based catalysts Au/TiO2/C (sonochemistry) and Au/TiO2/C (microwave).

Two model catalysts, Au/TiO2/C (S) (sonochemically derived) and Au/TiO2/C (M) (microwave derived), were produced by employing ultrasound irradiation and microwave irradiation, respectively. The deposition of gold colloids onto the support powders, TiO2/C, was accomplished by using a solvated metal atom impregnation (SMAI) method. The SMAI technique provides highly-dispersed gold particles on the TiO2/C support. The catalytic performance of Au based catalysts 1 wt% Au-TiO2/C (S) and 1 wt%Au-TiO2(M)/C (M) have been tested for the oxidation of CO in the temperature range of 0-300 degrees C and compared to that of 1 wt% Au-TiO2 (Degussa-P25). A boost in the conversion of CO was observed for the sonochemically-derived catalyst, Au/TiO2/C (S), at low temperature. Hence, the reactivity order found for CO oxidation is (Au/TiO2/C (S)>Au/TiO2 (P25)>Au/TiO2/C (M)).

A facile method for the deposition of volatile natural compound-based nanoparticles on biodegradable polymer surfaces.

In the current work, stable nanoparticles (NPs) of vanillin are formed in situ from an aqueous/ethanol solution and deposited on the surface of chitosan, a natural polymer, using a high-intensity ultrasonic method. The spectroscopic, physical, mechanical and morphological properties of the coated chitosan films are examined by helium-ion microscopy (HIM), atomic-force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), UV-vis spectroscopy, X-ray diffractometry (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and texture analysis, and compared with the original film properties. Vanillin NPs were detected on the film surface. It was also found that the sonochemical deposition method does not affect the bulk properties of the chitosan films. All the chitosan films demonstrated antimicrobial activity against Gram-negative and Gram-positive bacteria. The deposition of vanillin NPs on the chitosan film also leads to significant antibiofilm activity, especially against the biofilm formation of Escherichia coli bacteria. The in vivo antimicrobial effect of the modified chitosan films was examined on fresh-cut watermelon, melon and strawberry. Vanillin NP-coated chitosan films led to inhibition of total microbial growth and the substantial inhibition of mold and yeast on the fruit. This research can serve as a platform for the development of a mild and effective method for the activation and modification of natural polymers for their future application in biomedical devices and biodegradable active packaging materials.

Templating mesoporous silica with chiral block copolymers and its application for enantioselective separation.

In this paper we describe the synthesis of chiral mesoporous silica based on chiral block copolymers of poly(ethylene oxide) and of d-phenylalanine (PEO-b-D-Phe) as a surfactant template. The resulting porous structures are characterized by nitrogen sorption experiments, transmission electron microscopy, and small-angle XRD. It is shown that chiral block copolymers of PEO-b-D-Phe are effective as a surfactant template for the preparation of silica materials with highly ordered periodic mesoporous structures of hexagonal symmetry with a pore size of ca. 5 nm and high surface areas of ca. 700 m2/g. The enantioselectivity feature of this porous silica, after the extraction of the chiral copolymers, was examined by selective adsorption of enantiomers and racemic solutions of valine. The selective adsorption was measured by circular dichroism (CD) spectroscopy. A chiral selectivity factor of 2.34 was found with the D enantiomer of valine adsorbed preferably.

Are sonochemically prepared alpha-amylase protein microspheres biologically active?

Using high-intensity ultrasound, we have synthesized alpha-amylase microspheres. The paper presented characterization as well as catalytic experiments of the sonochemically-produced microspheres. It also provided an estimate of the efficiency of the sonochemical process in converting the native protein to microspheres. These microspheres showed a very good enzymatic activity compared with the native alpha-amylase. The enzymatic activity of the amylase microspheres was 27% of that of the native protein after a short reaction time (3 min), while over a longer reaction time (1 h) it reached 56% of the activity of the native protein.

Sonochemical fabrication of edible fragrant antimicrobial nano coating on textiles and polypropylene cups.

We report on a simple and effective ultrasound-assisted deposition of vanillin nanoparticles (∼50nm in size), raspberry ketone (RK) nanoparticles (∼40nm in size) and camphor nanoparticles (width ∼30nm, length ∼40nm in size) on textiles and on polypropylene surfaces. The excellent antibacterial and antifungal activity of the fragrant coatings on cotton bandages, and polypropylene surface against Escherichia coli (E. coli), Salmonella paratyphi A (S. paratyphi A) and the yeast Candida albicans (C. albicans) cultures was demonstrated. It is worth pointing out that these fragrant materials are edible, making them very useful for packaging. The mechanism of the edible fragrant coating formation and adhesion to the textile was discussed, and finally an up-scaling of the sonochemical process for textile coating was carried out.

One-step surface grafting of organic nanoparticles: in situ deposition of antimicrobial agents vanillin and chitosan on polyethylene packaging films.

Nanoparticles of natural antimicrobial agents, volatile vanillin and non-volatile chitosan, were deposited in situ from an aqueous/ethanol solution onto a polyethylene (PE) surface using the ultrasonic method. The modified PE films were comprehensively characterized in terms of their microscopic, spectroscopic, mechanical and physical properties, and the presence of stable organic nanoparticles on the polymer surface was established. The nanoparticle-grafted films showed specific antimicrobial activity against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. The vanillin nanoparticles led to a total inhibition of E. coli and the chitosan nanoparticles led to a total inhibition of S. aureus. The antimicrobial effect of the prepared active PE films was also examined on a food model, fresh-cut watermelons. Contact with the active film significantly inhibits the fruit microbial spoilage, especially in the case of the vanillin nanoparticles on PE. As they are surface-grafted in a nanoparticle form, the active agents are fully utilized, allowing for a significant enhancement in their effectivity and a reduction in the amount required. The presented method is of general interest as a facile technique for the surface deposition of organic nanoparticles, and can potentially be applied as a feasible approach for the incorporation of active agents into polymer matrices.

Formation of a three-dimensional microstructure of Fe3O4-poly(vinyl alcohol) composite by evaporating the hydrosol under a magnetic field.

In this paper, we report on the self-assembly formation of three-dimensional microstructures of Fe3O4 hydrosol. First, we perform new, facile, and direct fabrication of a stable hydrosol of Fe3O4 nanoparticles, based on the sonolysis of an aqueous solution of iron acetate in the presence of PVA-100,000. This is then followed by investigations of the formation of different microstructures obtained on drying a drop of the water suspension on a glass microscope substrate. The evaporation was carried out both without and in the presence of an external magnetic field.

Thermal decomposition of commercial silicone oil to produce high yield high surface area SiC nanorods.

This article reports on the synthesis of high surface area (563m2/g) beta-SiC nanorods by thermal decomposition of commercial silicone oil at a relatively low reaction temperature (800 degrees C) in a closed Swagelok cell. High yield (75%) of SiC nanorods are obtained in this one-stage, solvent-, catalyst-, and template-free synthesis technique that runs at a relative low temperature and employs cheap single-precursor. The morphological (TEM, HR-SEM), compositional (CHNS, EDX, SAEDX]), structural (XRD, HR-TEM, and ED), thermal (TGA) characterizations and surface area analysis are carried out for the obtained SiC nanorods. The possibility of hydrogen storage in this high surface area nano-SiC rods are also tested and reported for the first time.

Synthesis of a conducting SiO2-carbon composite from commercial silicone grease and its conversion to paramagnetic SiO2 particles.

The thermal decomposition of commercial silicone grease was carried out in a closed reactor (Swagelok) that was heated at 800 degrees C for 3 h, yielding a SiO2-carbon composite with a BET surface area of 369 m2/g. The bulk conductivity (5.72 x 10(-6) S x cm(-2)) of the SiO2-carbon composite was determined by impedance measurements. The as-prepared SiO2-carbon composite was further annealed at 500 degrees C in air for 2 h, which led to the formation of white paramagnetic silica particles (confirmed by ESR), possessing a surface area of 111 m2/g. The present synthetic technique requires unsophisticated equipment and a low-cost commercial precursor, and the reaction is carried out without a solvent, surfactant, or catalyst. The mechanism for the formation of a porous SiO2-carbon composite from the silicone grease is also presented.

Nanotechnology solutions to restore antibiotic activity.

This review focuses on the development of nanoparticle systems that enables to enhance and restore the antibiotic activity for drug-resistant organisms. New and more aggressive antibiotic resistant bacteria and parasites calls for the development of new therapeutic strategies to overcome the inefficiency of conventional antibiotics and bypass treatment limitations related to these pathologies. Nanostructured biomaterials, nanoparticles in particular, have unique physicochemical properties such as ultra-small and controllable size, large surface area to mass ratio, high reactivity, and functionalizable structure. These properties can be applied to facilitate the administration of antimicrobial drugs, thereby overcoming some of the limitations in traditional antimicrobial therapeutics. Here the current progress and challenges in synthesizing nanoparticle platforms for restoring activity of various antimicrobial drugs are reviewed with an emphasis on antibiotics. We also call attention to the need to unite the shared interest between nanoengineers and microbiologists in developing nanotechnology for the treatment of microbial diseases.

The preparation of magnetic proteinaceous microspheres using the sonochemical method.

Using high-intensity ultrasound, we have developed a method for the synthesis of magnetic microspheres. The microspheres are composed of iron oxide-filled and coated globular bovine serum albumin (BSA). The magnetic microspheres are prepared from BSA and iron pentacarbonyl, or from BSA and iron acetate. Transmission electron microscopy and scanning electron microscopy show spherical particles. The particle size distributions are gaussian, with a mean diameter of a few micrometers. Using chemical analysis, it was found that the total percentage of iron oxide in the microspheres is between 39% and 42%. Mössbauer measurements were also performed.

New approach for the removal of metal ions from water: adsorption onto aquatic plants and microwave reaction for the fabrication of nanometals.

We adsorb heavy metal ions such as Ag(+), Pb(2+), and Ru(3+) onto an aquatic plant and convert the adsorbed ions to the corresponding nanometallic particles by the polyol reaction carried out in a microwave oven.

Fabrication and magnetic properties of Ni nanospheres encapsulated in a fullerene-like carbon.

A very simple, efficient, and economical synthetic technique, which produces fascinating fullerene-like Ni-C (graphitic) core-shell nanostructures at a relatively low temperature, is reported. The thermal dissociation of Ni acetylacetonate is carried out in a closed vessel cell (Swagelok) that was heated at 700 degrees C for 3 h. The encapsulation of ferromagnetic Ni nanospheres into the onion structured graphitic layers is obtained in a one-stage, single precursor reaction, without a catalyst, that possesses interesting magnetic properties. The magnetoresistance (MR) property of Ni nanospheres encapsulated in a fullerene-like carbon was measured, which shows large negative MR, of the order of 10%. The proposed mechanism for the formation of the Ni-C core-shell system is based on the segregation and the surface flux formed in the Ni and carbon particles during the reaction under autogenic pressure at elevated temperature.

The use of tin-decorated mesoporous carbon as an anode material for rechargeable lithium batteries.

A sonochemical process has been developed for the insertion of tin nanoparticles into mesoporous carbon, giving a product which was used as a building block for the anode of a rechargeable Li battery; the electrode could deliver a reversible capacity of 400 mAh gr(-1)(C + Sn) at 100% cycling efficiency, which is higher than that of graphite electrodes.

The preparation of avidin microspheres using the sonochemical method and the interaction of the microspheres with biotin.

Avidin microspheres were prepared using the sonochemical method. It was found that avidin microspheres can bind biotin, but to a lesser degree than the native protein. The binding of the biotin molecules to the avidin microspheres was probed primarily by TPD measurements.

Preparation of stable porous nickel and cobalt oxides using simple inorganic precursor, instead of alkoxides, by a sonochemical technique.

Porous nickel and cobalt oxides were prepared using NiSO4.6H2O and anhydrous Co(CH3COO)2, a precursor other than alkoxides and cetyltrimethylammonium bromide as organic surfactant. The sonication method has been used for such synthesis. The surfactants were removed by calcination, as well as by solvent extraction and it is extent was examined by IR spectroscopy. The trend of removal of surfactant was followed by TGA studies and the change in phases by DSC. The products were identified by XRD. Peak in low angle XRD indicates the porous nature of the oxides. The morphology of the pores was studied by transmission electron microscopy. The pores were found less ordered, having an average size of 4-6 nm. The Brunauer-Emmet-Teller surface areas of the as-prepared, as well as the treated samples are reported having H2 and H4 type hysteresis for Ni and Co, respectively.