N. D. Golubeva

Hybrid polymer-immobilized palladium nanoparticles: Preparation and catalytic properties

A new approach to the synthesis of mixed-type immobilized catalysts was developed: the frontal polymerization of a metal-containing monomer in the presence of a highly dispersed mineral support. The synthesis of an acrylamide complex of Pd(II) nitrate on the surface of SiO2, Al2O3, or C and its subsequent polymerization and reduction resulted in the formation of an organic-inorganic composite that included nanosized Pd particles stabilized by a polymer matrix and an inorganic support. The resulting hybrid nanocomposites are efficient and selective catalysts for the hydrogenation reactions of cyclohexene and alkene and acetylene alcohols.

Preparation of nanostructured materials through thermolysis of metal chelate complexes

We demonstrate that nanocomposites (metals and metal carbides and sulfides) can be produced by thermolysis (370 and 600°C) in a self-generated atmosphere using Cu(II), Co(II), and Ni(II) 2-hydroxy- and 2-N-tosylaminobenzaldehyde azomethine bis-chelates as precursors.

Synthesis and reactivity of metal-containing monomers 76. Nanostructured materials obtained by controlled thermolysis of Ni, Co, and Cu chelate complexes with azomethine ligands

The controlled thermolysis of mono(NiII, CuII, and CoII) and dinuclear (NiII, CuII, and FeII) chelate complexes with azomethine ligands, containing oxygen, nitrogen, and sulfur atoms in the chelate rings, was studied. The effect of the ligand environment on the thermal stability and composition of the resulting nanocomposites was examined. Comparative thermal analysis (DSC, DTA, and TGA) of the metal chelate complexes was performed. Their thermolysis products were characterized using elemental analysis, X-ray powder diffraction, scanning electron microscopy, and gel permeation chromatography. The magnetic properties of the nanocomposites obtained were analyzed.

Hafnium-containing nanocomposites

New types of hafnium-containing nanocomposites are prepared by combining polymer synthesis and controlled thermolysis. This approach involves the preparation and subsequent thermolysis of hafnium-containing polymers or concurrent solid-state polymerization of hafnium-containing monomers and thermal decomposition of the forming metal-containing polymer at different temperatures. The composition and structure of the synthesized hafnium-containing precursors and thermolysis products are determined by elemental analysis, IR spectroscopy, mass spectrometry, optical microscopy, and x-ray diffraction. Thermodynamic analysis is used to assess the equilibrium composition of the Hf-C-H-O system and establish the conditions under which HfC and HfO2 are formed.

Polymer-immobilized rhodium complexes forming in situ: preparation and catalytic properties

We elaborated a method for frontal polymerization of a Rh-containing monomer in the presence of a conventional support to obtain polymer-immobilized hydrogenation catalysts. A hybrid nanocomposite forms during the propagation of a narrow molten zone (first-order phase transition) and is characterized by stable front propagation throughout the reaction volume. The products were characterized by various physicochemical methods and were tested as catalysts in the hydrogenation of cyclohexene, allyl alcohol, and nitrobenzene. The transformation of the X-ray photoelectron spectrum (XPS) on passing from the starting rhodium nitrate complex to its metal monomer (acrylamide complex), polymer, and supported catalyst is described. Native intermediate products were isolated and characterized by XPS.

Synthesis and characterization of nanostructured MnO2–CoO and its relevance as an opto-electronic humidity sensing device

Metal carboxylates are widely used in science and technology and have been the subject of intense studies due to the practical importance of their products. The present paper reports the synthesis of MnO2–CoO using metal carboxylates as precursors and the effect of humidity on the transmitted power through its thin film at room temperature. The refractive index of the material was found to be 1.445930 and the peak obtained from the photoluminescence spectra lies in the visible region. TEM reported a minimum grain size of ∼5.7 nm and SAED confirmed the crystalline nature of the material, which was further confirmed by XRD. Fluorescence characteristics also confirmed the low dimensionality of the material. The film was then investigated using SEM which exhibited the porous morphology. Through UV-Vis spectroscopy, it was found that the absorption of the film takes place in the UV region and the optical band-gap was observed to be 3.849 eV from the Tauc plot. The film was employed as a transmission based opto-electronic humidity sensor. Average sensitivity was found to be ∼2.225 μW/% RH with response and recovery times of 47 s and 59 s respectively. Experiments were repeated and the reproducibility of result was found to be ∼89%.

Synthesis and characterization of metal–polymer nanocomposites with radiation-protective properties

Metal–polymer nanocomposites, which can weaken the activity of a beta radiation source in undesirable directions at the minimum protection size, are developed. These nanocomposites are fabricated by dispersing metal-containing nanoparticles in thermoplastic matrices. Metal nanoparticles are synthesized by the polymerassisted thermolysis of metal-containing precursors. The composition and structure of the nanocomposites are characterized by elemental and X-ray diffraction analyses and transmission electron microscopy.

Polymers based on unsaturated alkoxides of refractory metals

Metallopolymers based on unsaturated alkoxides of refractory metals (Ti(IV), V(V), Ta(V), Nb(V)) are synthesized and characterized; their thermal behavior is studied via TGA, TMA, and DSC. It is shown that nanocomposite materials can be synthesized through the polymerization of metal-containing monomers and subsequent controlled thermolysis of the products.

Frontal Polymerization of Metal-Containing Monomers as a way for Synthesis of Polymer Nanocomposites

The frontal polymerization of metal-containing monomers based on acry lamide (AAm) complexes of transition and noble metal nitrates M(AAm) x(H2O)y(NO3)2 (M = Co, Ni, Fe, Cu, Zn, Cd, Ba, Pd) and the properties of the products obtained are studied. This is a first example of thermal (353-433 K) initiation of frontal polymerization without any c hemical initiators. By examining the kinetics of thermolysis and evolution of gaseous products o f transformation we have concluded that nitrogen oxides formed during partial oxidation of nitrate g oups are able to initiate the reaction. We succeeded first in carrying out frontal copolyme rization of acrylamide complexes with traditional monomers. The main copolymerization parameters are estimated. Following controllable thermolysis of metallopolymers formed or controlled chan ge of frontal polymerization into burning regime leads to the formation of metallopolymer nanocompos ites. The yield product is metal (or metal oxides) nanoparticles stabilized by a pyroliz ed polymer matrix. The size of the particles is about 6 to 30 nm. The novel approach for synthesis of palladi um immobilized catalysts via frontal polymerization of acrylamide complexes into surface of inorganic ox ides is elaborated.