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.

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.

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.

Sonochemical synthesis, structural, magnetic and grain size dependent electrical properties of NdVO4 nanoparticles.

NdVO4 nanoparticles are successfully synthesized by efficient sonochemical method using two different structural directing agents like CTAB and P123. The phase formation and functional group analysis are carried out using X-ray diffraction (XRD) and fourier transform infra red (FT-IR) spectra, respectively. Using Scherrer equation the calculated grain sizes are 27 nm, 24 nm and 20 nm corresponding to NdVO4 synthesized by without surfactant, with CTAB and P123, respectively. The TEM images revealed that the shape of NdVO4 particles is rice-like and rod shaped particles while using CTAB and P123 as surfactants. The growth mechanism of NdVO4 nanoparticles is elucidated with the aid of TEM analysis. From electrical analysis, the conductivity of NdVO4 nanoparticles synthesized without surfactant showed a higher conductivity of 5.5703 × 10(-6) S cm(-1). The conductivity of the material depends on grain size and increased with increase in grain size due to the grain size effect. The magnetic measurements indicated the paramagnetic behavior of NdVO4 nanoparticles.

Micro- and nano-spheres of low melting point metals and alloys, formed by ultrasonic cavitation.

Metals and alloys of low melting points (<430 °C) can be melted in hot silicone oil to form two immiscible liquids. Irradiation of the system with ultrasonic energy induces acoustic cavitation in the oil, which disperses the molten metals into microspheres that solidify rapidly upon cooling. This method has been applied to seven pure metals (Ga, In, Sn, Bi, Pb, Zn, Hg) and two eutectic alloys of gold (Au-Ge and Au-Si). The morphology and composition of the resulting microspheres were examined by SEM and EDS. Eutectic Au-Si formed also crystalline Au nanoparticles, which were separated and studied by HRTEM.

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.

Ultrasound radiation as a "throwing stones" technique for the production of antibacterial nanocomposite textiles.

Ultrasound irradiation was applied as a "throwing stones" technique for coating cotton bandages with MgO and Al(2)O(3) commercially obtained nanoparticles. The homogeneous distribution of the nanoparticles without any aggregation on the fabrics was demonstrated. The antibacterial activities of the MgO/Al(2)O(3)-fabric nanocomposite were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures. A significant bactericidal effect, even in a concentration <1% (by weight), was detected.

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.

Decorating parylene-coated glass with ZnO nanoparticles for antibacterial applications: a comparative study of sonochemical, microwave, and microwave-plasma coating routes.

A glass substrate, coated with a Parylene film, was coated with ZnO by three different methods: ultrasound, microwave, and microwave-plasma irradiation. These coating modes are simple, efficient, and environmentally friendly one-step processes. The structure of the coated products was characterized and compared using methods such as XRD, HR-SEM, EDS, RBS, and optical spectroscopy. Coating by ZnO nanoparticles was achieved for all three approaches. The products were found to differ in their particle sizes, coating thickness, and depth of penetration. All of the ZnO-Parylene-glass composites demonstrated a significant antibacterial activity against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) strains.

Highly Luminescent Zn(x)Cd(1-x)Se/C Core/Shell Nanocrystals: Large Scale Synthesis, Structural and Cathodoluminescence Studies.

Zn(x)Cd(1-x)Se/C core/shell nanocrystals with 31-39 nm semiconducting core and 11-25 nm carbon shell were synthesized from solid state precursors in large scale amounts. A mixture of spherical and tripod nanostructures were obtained only in the one-step reaction (ZC3), where the Zn- and Cd-precursors were reacted simultaneously, rather than in the two step reactions (ZC1 and ZC2), where largely spherical nanostructures were observed. Rietveld analysis of the X-ray diffraction patterns of the samples prepared in three different ways, all under their autogenic pressure, reveal varying compositions of the Zn(x)Cd(1-x)Se nanocrystal core, where the cubic phases with higher Zn content were dominant compared to the hexagonal phases. Carbon encapsulation offers excellent protection to the nanocrystal core and is an added advantage for biological applications. Cathodoluminescence (CL) measurements with spatially integrated and highly localized excitations show distinct peaks and sharp lines at various wavelengths, representing emissions from single nanostructures possessing different compositions, phases, and sizes. Transmission electron microscopy (TEM) showed striations in the nanocrystals that are indicative of a composition modulation, and possibly reveal a phase separation and spinodal decomposition within the nanocrystals. Thermal quenching of the luminescence for both the near band-edge and defect related emissions were observed in the range 60-300 K. The measured activation energies of ∼50-70 meV were related to the presence of shallow donors or acceptors, deep level emissions, and thermal activation and quenching of the luminescence due to the thermal release of electrons from shallow donors to the conduction band or a thermal release of holes from shallow acceptors to the valence band. Spatially integrated CL spectra revealed the existence of broadening and additional components that are consistent with the presence of a composition modulation in the nanocrystals. Spatial localization of the emission in isolated single nanocrystals was studied using monochromatic CL imaging and local CL spectroscopy. CL spectra acquired by a highly localized excitation of individual nanocrystals showed energy shifts in the excitonic luminescence that are consistent with a phase separation into Zn- and Cd-rich regions. The simultaneous appearance of both structural and compositional phase separation for the synthesis of Zn(x)Cd(1-x)Se nanocrystals reveals the complexity and uniqueness of these results.

Antibacterial properties of an in situ generated and simultaneously deposited nanocrystalline ZnO on fabrics.

Zinc oxide (ZnO) nanoparticles were synthesized and deposited on the surface of cotton fabrics using ultrasound irradiation. Optimization of the process resulted in a homogeneous distribution of ZnO nanocrystals, 30 nm in size, on the fabric surface. The mechanism of the ultrasound-assisted coating was proposed. The antibacterial activities of the ZnO-fabric composite were tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures. A significant bactericidal effect, even in a 0.75% coated fabric (wt %), was demonstrated.

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.

Effects of a 10 T external magnetic field on the thermal decomposition of Fe, Ni, and Co acetyl acetonates.

The current investigation is centered on the thermal decomposition (700 degrees C) of acetyl acetonates of Ni, Co, and Fe in a closed reactor that was conducted by employing an external magnetic field (MF) of 10T. Interestingly, reactions of Co and Ni acetyl acetonates under a 10T MF produce Co and Ni nanoparticles (NPs) coated with carbon, while Fe acetyl acetonate produces Fe3O4 uncoated with carbon. Additionally, it is observed that all the as-formed magnetic particles tend to align in one dimension along applied MF; thus, this process can be used to fabricate large arrays of magnetic nanoparticles. The effect of an applied MF to synthesize morphologically and compositionally different products from corresponding precursors with their mesoscopic organization is the key theme of the present paper, explained with a plausible mechanism.

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)).

One-pot fabrication and magnetic studies of Mn-doped TiO(2) nanocrystals with an encapsulating carbon layer.

Mn-doped TiO(2) nanocrystals encapsulated in a carbon layer (Ti(1-x)Mn(x)O(2)@C) were synthesized by the one-pot RAPET (reaction under autogenic pressure at elevated temperature) technique. Manganese was doped into the body-centered tetragonal TiO(2) anatase phase to give a Mn:Ti atomic ratio of 1%, 5% and 10%. The surface modification by carbon was achieved in order to make the cubic/tetragonal nanocrystals non-toxic and biocompatible. Electron paramagnetic resonance (EPR) studies revealed a broad resonance (centered at g = 1.9977 due to the interacting spins in the oxide matrix) with increased dopant concentration and the resonance due to carbon. Manganese is mainly present as +II or +III oxidation states. The magnetic behavior was found to be very dependent on the manganese concentration with a ferromagnetic behavior of the 1% doped sample due to the coupling between carriers and manganese spins. A predominant paramagnetic behavior was observed for the higher Mn-doped samples. This study opens up a new dimension for the carbon encapsulation of room-temperature ferromagnetic diluted magnetic semiconductor (DMS) nanomaterials.

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.

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.

External magnetic field-induced mesoscopic organization of Fe3O4 pyramids and carbon sheets.

The current investigation is centered on the thermal decomposition of iron(II) acetyl acetonate, Fe(C5H7O2)2, in a closed cell at 700 degrees C, which is conducted under a magnetic field (MF) of 10 T. The product is compared with a similar reaction that was carried out without a MF. This article shows how the reaction without a MF produces spherical Fe3O4 particles coated with carbon. The same reaction in the presence of a 10 T MF causes the rejection of the carbon from the surface of pyramid-shaped Fe3O4 particles, increases the Fe3O4 particle diameter, forms separate carbon particles, and leads to the formation of an anisotropic (long cigarlike) orientation of Fe3O4 pyramids and C sheets. The macroscopic orientation of Fe3O4 pyramids+C sheets is stable even after the removal of an external MF. The suggested process can be used to fabricate large arrays of uniform wires comprised of some magnetic nanoparticles, and to improve the magnetic properties of nanoscale magnetic materials. The probable mechanism is developed for the growth and assembly behavior of magnetic Fe3O4 pyramids+C sheets under an external MF. The effect of an applied MF to synthesize morphologically different, but structurally the same, products with mesoscopic organization is the key theme of the present paper.

Difference in the bonding scheme of calix(6)arene and p-sulfonic calix(6)arene to nanoparticles of Fe(2)O(3) and Fe(3)O(4).

Calix(6)arene (C6) and p-sulfonic calix(6)arene (p-C6) formed chemical bonds with Fe(2)O(3) and Fe(3)O(4), respectively. The complexes exhibit different nature of bonding of C6 and p-C6 to the substrates.