Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria

Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.

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Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Applications of nanotechnology in water and wastewater treatment

Reactive magnesium oxide nanoparticles and halogen (Cl2, Br2) adducts of these MgO particles were allowed to contact certain bacteria and spore cells. Bacteriological test data, atomic force microscopy (AFM) images, and electron microscopy (TEM) images are provided, which yield insight into the biocidal action of these nanoscale materials. The tests show that these materials are very effective against Gram-positive and Gram-negative bacteria as well as spores. ζ-Potential measurements show an attractive interaction between the MgO nanoparticles and bacteria and spore cells, which is confirmed by confocal microscopy images. The AFM studies illustrate considerable changes in the cell membranes upon treatment, resulting in the death of the cells. TEM micrographs confirm these results and supply additional information about the processes inside the cells. Overall, the results presented illustrate that dry powder nanoparticulate formulations as well as water slurries are effective. It is proposed that abrasive...

Metal Oxide Nanoparticles as Bactericidal Agents

Nanocrystals of MgO and CaO have been prepared by a modified aerogel/hypercritical drying/dehydration method. For nanocrystalline MgO (AP-MgO) surface areas ranged from 250 to 500 m2/g, whereas for AP-CaO 100−160 m2/g. These materials have been compared with more conventional (CP) microcrystalline samples of lower surface area with regard to (1) morphology (AP-samples (autoclave preparation) are tiny polyhedral crystallites, while CP-samples (conventional preparation) are larger, hexagonal platelets and cubes); (2) residual surface OH (AP-samples have less acidic OH, which are more isolated from each other; (3) acid gas adsorption (AP-samples adsorb more SO2 and CO2 at low pressures and room temperature and prefer monodentate rather than bidentate adsorption modes, but at higher pressures CP-samples adsorb more SO2 and HCl apparently due to the formation of more well ordered multilayers); (4) destructive adsorption of organophosphorus compounds and chlorocarbons (AP-samples are superior due to higher surf...

Nanocrystals as Stoichiometric Reagents with Unique Surface Chemistry

A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4–7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption properties are due to nanocrystal shape, polar surfaces, and high surface areas. Free-flowing powders or consolidated pellets are effective, and pore structure can be controlled by consolidation pressures. Chemical properties can be adjusted by choice of metal oxide as well as by incorporating other oxides as monolayer films.

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

Catalytic Solid State Reactions on the Surface of Nanoscale Metal Oxide Particles

Nanocrystals of magnesium oxide react with organophosphorus compounds at room temperature by dissociative chemisorption, which we term "destructive adsorption" This process involves cleavage of P-O and P-F bonds (but not P-C bonds) and immobilization of the resultant molecular fragments These ultrafine powders have unusual crystalline shapes and possess high surface concentrations of reactive edge/corner and defect sites, and thereby display higher surface reactivity, normalized for surface area, than typical polycrystalline material This high surface reactivity coupled with high surface area allows their use for effective decontamination of chemical warfare agents and related toxic substances Herein data is presented for paraoxon, diisopropylfluorophosphate (DFP), and (CH3CH2O)2P(O)CH2-SC6H5 (DEPTMP) Solid-state NMR and IR spectroscopy indicate that all OR and F groups dissociate; this leaves bound -PO4, -F, and -OR groups for paraoxon, DFP, and DEPTMP, respectively For paraoxon, it was shown that one monolayer reacts For DEPTMP, the OR groups dissociate, but not the P-CH2SC6H5 group The nanocrystalline MgO reacts much faster and in higher capacity than typical activated carbon samples, which physisorb but do not destructively adsorb these phosphorous compounds

Nanocrystalline metal oxides as destructive adsorbents for organophosphorus compounds at ambient temperatures.

Compositions and method for destroying biological agents such as toxins are provided wherein the substance to be destroyed is contacted with finely divided metal oxide nanocrystals. In various embodiments, the metal oxide nanocrystals have reactive atoms stabilized on their surfaces, species adsorbed on their surfaces, or are coated with a second metal oxide. The desired metal oxide nanocrystals can be pressed into pellets for use when a powder is not feasible. The methods of the invention are safe for humans, equipment, and the environment, and provide for decontamination of warfare sites, of equipment exposed to the contaminant, and of soil, water, and air having been exposed to the contaminant. Preferred metal oxides for the methods include MgO, CaO, TiO2, ZrO2, FeO, V2O3, V2O5, MN2O3, Fe2O3, NiO, CuO, Al2O3, ZnO, and mixtures thereof. Preferred coating metal oxides include oxides of metals selected from the group consisting of Ti, V, Fe, Cu, Ni, Co, Mn, Zn, and mixtures thereof. Preferred reactive atoms include halogens and Group I metals, and preferred species include SO2, NO2, and ozone.

Shawn Decker

Papers

Nanocrystals as Stoichiometric Reagents with Unique Surface Chemistry

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

Catalytic Solid State Reactions on the Surface of Nanoscale Metal Oxide Particles

Nanocrystalline metal oxides as destructive adsorbents for organophosphorus compounds at ambient temperatures.

Reactive nanoparticles as destructive adsorbents for biological and chemical contamination