Interaction between Dioxane and Nanocluster Polyoxomolybdates and Their Composites Containing Water-Soluble Polymers

Russian Journal of Physical Chemistry A - New data are obtained on the thermodynamics and molecular mechanisms of the interaction between dioxane and nanocluster polyoxomolybdates of the keplerate...     

Study of the stability of solid polyoxometalate Mo72Fe30 with a buckyball structure

Samples of polyoxometalate Mo₇₂Fe₃₀: [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂ {H₂Mo₂O₈(H₂O)}(H₂O)₉₁] · ??150H₂O with a buckyball structure, which can be both crystalline and amorphous, were synthesized. It was shown that such samples can be studied by neutron diffraction. The stability of Mo₇₂Fe₃₀ to heating and UV light exposure (in poly(vinyl alcohol) and polyvinylpyrrolidone films) was studied by IR, EPR, and electronic absorption spectroscopy; thermal analysis; and mass spectrometry. Mo₇₂Fe₃₀ was found to be less stable to heating and irradiation in a poly(vinyl alcohol) film as compared with the related polyoxometallate Mo₁₃₂ free of iron. The sorption properties of Mo₇₂Fe₃₀ to organic vapors and its stability under sorption conditions were studied. It was demonstrated that, in addition to sorption, organic substances cause the destruction of buckyballs.     

Association of Spherical Porous Nanocluster Keplerate-Type Polyoxometalate Mo<Subscript>72</Subscript>Fe<Subscript>30</Subscript> with Biologically Active Substances

The peculiarities of formation of ionic associates of the spherical porous nanocluster polyoxometalate [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁] ~ 150H₂O with biologically active substances, in particular, thiamine chloride using the methods of UV/Vis spectroscopy, pH-metry, laser light scattering (the measurement of Zeta potential and particle size distribution), Raman spectroscopy, infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy has been studied. The location of thiamine molecules on POM’s surface is given. The solubility product of associate was estimated. The formation of molecular associates of polyoxometalate with insulin, albumin has been shown. Using the meglumine acridonacetate the influence of complexing agents on the possibility of obtaining associates on the basis of [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁] ~ 150H₂O has been studied.     

Electric conductivity of nanocluster polyoxomolybdates in the solid state and solutions

The electric conductivity of nanocluster polyoxomolybdates (POMs) Mo₁₃₂ and Mo₇₂Fe₃₀ with a keplerate structure in aqueous solutions, of these POMs in the solid state, and of Mo₁₃₈ with a toroidal structure was studied. Data on the concentration dependence of the equivalent electric conductivity in solutions and on the specific conductivity of the solid samples were obtained. Solid Mo₁₃₂ showed predominantly electron type of conductivity at nearly room temperatures due to the presence of molybdenum at different oxidation levels; Mo₇₂Fe₃₀, which has metal components at the highest oxidation levels, was found to be poor electric conductor; Mo₁₃₈, which has a lower content of low-valence molybdenum than Mo₁₃₂, showed intermediate conductivity and a reversible transition between the proton and electron types of conductivity.     

Prerequisites and prospects for the development of novel systems based on the Keplerate type polyoxomolybdates for the controlled release of drugs and fluorescent molecules

Russian Chemical Bulletin - Synthetic approaches were proposed to the development of hybrid organic—inorganic systems based on giant Keplerate polyoxometalates (POM Mo132), biocompatible...     

Fundamental Aspects of Xanthene Dye Aggregation on the Surfaces of Nanocluster Polyoxometalates: H- to J-Aggregate Switching

The induced aggregation of the xanthene dye rhodamine B (RhB) on metal oxide centers belonging to the highly symmetric surfaces of precise nanoscale templates with Keplerate (Mo₁₃₂) or toroidal (Mo₁₃₈) structures has been studied. With the joint use of the Langmuir isotherm and full Stern–Volmer models, the thermodynamic reasons for dye adsorption on the nanocluster surface, such as a mixture of monomer, H-aggregate (H-dimer), and J-aggregate forms (which can coexist or switch one into another under the exact conditions), were established: this was shown through UV/Vis and fluorescence spectroscopies. By using the framework of the exciton model, it is shown that the angle (α) between the transition dipole moments of RhB is very sensitive to surface strain inside the dye sub-monolayer. As a result, it is possible to switch from H- to J-aggregates by the post-functionalization of polyoxometalate (POM)-RhB associates by the surfactant bilayer shell, which allows the surface strain to grow. Recommendations are provided for managing the appearance of H- or J-aggregates on metal oxide (or polyelectrolyte) surfaces during photovoltaic or bioimaging applications.     

On the possibility of controlling the hydrophilic/hydrophobic characteristics of toroid Mo138 nanocluster polyoxometalates

Russian Journal of Physical Chemistry A - The possibility of changing the hydrophilic (polar) surfaces of toroid nanocluster polyoxomolibdates to hydrophobic (nonpolar) surfaces via the...     

Evolution of ammonium metavanadate crystals in polyvinyl alcohol films

The formation processes, morphological features, and evolution of ammonium metavanadate crystals in polyvinyl alcohol films have been studied. These crystals have unusual shapes. The aforementioned processes are simulated.