Stanislav Ferdov

A Review on the Green Synthesis of Silver Nanoparticles and Their Morphologies Studied via TEM

Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology.

Improved performance of rare earth doped LiMn2O4 cathodes for lithium-ion battery applications

Different rare-earth element (Dy, Gd, Tb and Yb) doped LiMn2O4 spinel active materials were prepared by a sol–gel method. The rare earth doping elements decrease the particle size but do not affect the formation of a cubic spinel structure. Furthermore, these dopants have a strong influence on the overall electrical properties of the cathodes prepared from them. In cyclic voltammetry measurements, two pairs of separated redox peaks are observed, regardless of the dopant. LiMn2O4 materials doped with gadolinium (Gd) and dysprosium (Dy) exhibit comparable room temperature rate capabilities to pristine LiMn2O4, with a discharge capacity of 94.5 mA h g−1 and 82.3 mA h g−1, respectively, versus 73.4 mA h g−1 for pristine LiMn2O4 at a rate of C5. Terbium (Tb) and ytterbium (Yb) doping shows, on the other hand, lower performance. After 50 cycles at C2, the capacity fade is 7% for LiMn1.95Dy0.05O4 and 14% for LiMn1.95Gd0.05O4, whereas for LiMn2O4 it is 32%. The improved cycling performance of LiMn2O4 doped with Gd and Dy is attributed to the powder size and atomic radii of the elements. The differences of the capacity retention on cycling are attributed to superior structural stability due to the rare earth doping. These results indicate that improved cathode materials doped with rare earth elements are suitable for lithium-ion battery applications.

Influence of zeolite structure and chemistry on the electrical response and crystallization phase of poly(vinylidene fluoride)

Zeolites with framework types LTL, LTA, FAU, and MFI were synthesized and used as fillers to prepare PVDF/zeolite composites. The obtained composites showed structural and electrical dependence on the pore system and chemical content of the inorganic host. The larger polymer-zeolite electrostatic interactions of the Y and A zeolites lead the polymer to crystallize in the electroactive γ-phase, which in the case of the L zeolite is prevented due to the reduced interaction area. The solvent and water encapsulation ability of the zeolite as well as improve of the dielectric response of the composite is directly related to the Si/Al ratio, leading zeolites with lower Si/Al ratios to larger dielectric responses and encapsulation efficiencies in the composites. These effects show also some dependency on the dimensionality of the pore system; the zeolite L-containing 1D channels showing superior dielectric performance than the 3D pore system of zeolite Y.

New Crystalline Layered Zinc Phosphate with 10-Membered-Ring Channels Perpendicular to Layers

A novel layered zinc phosphate, [N(2)C(6)H(12)](2)[Zn(7)H(3)(HPO(4-x))(5)(PO(4))(3)]H(2)O, with unique 10-membered-ring ellipsoidal channels running perpendicularly to ladder-shaped tetrahedral layers, has been synthesized ionothermally via in situ generation of 1,4-diazabicyclo[2.2.2]octane.

Silver Nanoparticles: Synthesis, Properties, and Applications

1Department of Physics, University of Oslo, 24 Sem Saelandsvei, 316 Oslo, Norway 2Institute of Physics, University of Tartu, Ravila 14c, 51014 Tartu, Estonia 3Tartu College, Tallinn University of Technology, Puiestee 78, 51008 Tartu, Estonia 4Department of Physics, University of Minho, 4800-058 Guimaraes, Portugal 5Department of Physics, Brock University, St. Catharines, ON, Canada L2S 3A1 6CWIT Capital Inc., 8 Baker Drive, St. Catharines, ON, Canada L2N 2V8

A microporous titanosilicate for selective killing of HeLa cancer cells

Structural distribution of zinc(II) ions in the pore system of three silicate molecular sieves has revealed an unprecedented application of the microporous titanosilicate Zn–ETS-4 as a non toxic, highly efficient and selective inhibitor of HeLa cancer cells.

Layered titanosilicates for size- and pattern-controlled overgrowth of MFI zeolite

Size- and pattern-selective overgrowth of an MFI-type zeolite (silicalite-1) on the layered titanosilicates JDF-L1 (Jilin Davy Faraday-Layered solid 1, also known as Aveiro Manchester-1, AM-1) and AM-4 (Aveiro Manchester-4) is realized. The shell of MFI is grown as a closely packed monolayer of submicron cask-like particles following the surface contour of the core of plate-like particles of JDF-L1. The overgrowth of MFI on AM-4 carries the characteristics of heteroepitaxial interconnection. Isolated crystals (5–10 μm) of MFI are closely embedded along various orientations to the plate-like particles of AM-4. The thermal behaviour of the interconnected materials was evaluated by in situ high-temperature powder X-ray diffraction. The realized heterochemical and heterostructural interconnections show that the surface of the layered titanosilicates can act as multi- and single-nucleation sites. This finding might be applied to other members of the family of tetrahedral–octahedral molecular sieves and may be important for the design of hierarchical catalysts and adsorbents with mixed properties.

Hydrothermal synthesis, crystal structure, and magnetic properties of a new inorganic vanadium(III) phosphate with a chain structure.

A new vanadium(III) phosphate, Na3V(OH)(HPO4)(PO4), has been synthesized by using mild hydrothermal conditions under autogeneous pressure. This material represents a very rare example of sodium vanadium(III) phosphate with a chain structure. The crystal structure has been determined by refinement of powder X-ray diffraction data, starting from the atomic coordinates of an isotypic compound, Na3Al(OH)(HPO4)(PO4), which was obtained under high temperature and high pressure. The phase crystallizes in monoclinic space group C2/m (No. 12) with lattice parameters a = 15.423(9) A, b = 7.280(0) A, c = 7.070(9) A, beta = 96.79(7) degrees, V = 788.3(9) A(3), and Z = 4. The structure consists of one-dimensional chains composed of corner-sharing VO5(OH) octahedra running along the b direction. They are decorated by isolated PO4 and HPO4 tetrahedra sharing two of their corners with the ones of the vanadium octahedra. The interconnection between the chains is assured by three crystallographically distinct Na(+) cations. Magnetic investigation confirms the 3+ oxidation state of the vanadium ions and reveals an antiferromagnetic arrangement between those ions through the chain.

A rapid method of synthesizing the layered titanosilicate JDF-L1

A rapid procedure for synthesis of highly crystalline and pure samples of JDF-L1 without using organics are reactants or templates is described and indexation of the powder X-ray diffraction pattern of this phase is presented.

Rapid and phase pure synthesis of microporous copper silicate (CuSH–1Na) with 12-ring channel system

Phase pure sample of the microporous copper silicate CuSH–1Na has been obtained by simplified hydrothermal method without using additives (H2O2 and Na2HPO4). Ion exchange of Na+ by Cs+, Ca2+ and Sr2+ ions showed that the structure can suffer partial replacement of the charge compensating cations. Ion exchange with Cs+ resulted in distinct dehydration while the ion exchange with Sr2+ increased the total amount of water. Water content in the Ca-exchanged sample is comparable to the as-synthesized sodium phase. Raman spectroscopy revealed that the divalent cations as Ca2+ and Sr2+ induce stronger local structural deformations than the monovalent Cs+. These structural changes have been also followed by the refined lattice distortions. Magnetic analyses showed that CuSH–1Na presents a very weak ferromagnetic interaction along the Cu2+ chains with a nearly vanishing Curie–Weiss temperature. This magnetic coupling is associated with super-super-exchange interactions through Cu–Na–O–Na–Cu paths. Antiferromagnetic coupling, attributed to inter-chains super-super-exchange interactions, competes with the ferromagnetic one and prevails at the lowest temperature.