Ivanka Spassova

Ivanka Spassova
Bulgarian Academy of Sciences | BAS · Institute of General and Inorganic Chemistry

PhD

About

61
Publications
5,933
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576
Citations
Citations since 2016
35 Research Items
404 Citations
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100

Publications

Publications (61)
Article
Full-text available
The present paper reports on MnCoFeO4 spinels with peculiar composition and their catalytic behavior in the reactions of complete oxidation of hydrocarbons. The samples were synthesized by solution combustion method with sucrose and citric acid as fuels. All samples were characterized by powder X-ray diffraction, N2-physisorption, scanning electron...
Article
Full-text available
The activated carbons were produced from waste biomass using a mixture of used motor oil and diverse plastic residues, such as high-density polyethylene and thermoplastic phenol formaldehyde resins. They were used as a host matrix of iron and/or chromium oxide nanoparticles. The obtained materials were characterized in details by a complex of physi...
Article
Thermo-responsive copolymer, Agar agar-graft-poly(N-vinylcaproactam) (AA-g-PnVCL) was prepared by grafting N-vinylcaprolactam units onto the Agar backbone. Graft copolymer was synthesized by free-radical polymerization, using 2,2′-Azobis(2,4-dimethylvaleronitrile) (AMVN) as an initiator in the nitrogen atmosphere. In order to evaluate the compositi...
Article
Full-text available
In the present study, we report on the facile prepared nanocomposites of reduced graphene oxide RGO with Cu and Ag. The synthesis was performed through an environmentally friendly and easy method by simultaneous reduction in solutions containing Cu2+ or Ag+ and graphene oxide (GO) using zinc powder as a reducing agent in aqueous acidic media. The c...
Article
Full-text available
Nickel-decorated mesoporous cerium–iron oxide composites were synthesized by a combination of incipient wetness impregnation and template-assisted hydrothermal techniques. The effects of the Fe/Ce ratio and the calcination temperature of cerium–iron oxides on the phase composition, texture, structure, and redox properties of the composites were stu...
Article
Full-text available
Oregano oil (OrO) possesses well-pronounced antimicrobial properties but its application is limited due to low water solubility and possible instability. The aim of this study was to evaluate the possibility to incorporate OrO in an aqueous dispersion of chitosan–alginate nanoparticles and how this will affect its antimicrobial activity. The encaps...
Article
Full-text available
Bifunctionalized mesoporous silica materials were prepared by sol–gel method applying newly proposed sequence of addition of the used silanols in the systems tetraethylortosilicate (TEOS): Tris[3-(trimethoxysilyl)propyl] isocyanurate (ISC): bis[(3- trimethoxysilyl)propyl]amine (BTPA), TEOS: ISC: (3-mercaptopropyl)trimethoxysilane (MPTMS) (TEOS: ISC...
Poster
Full-text available
Capturing carbon dioxide from large CO 2 emission sources, like power plants and steel mills, is technologically the first important stage of the CCS and CCU approaches aimed at mitigating the global warming. Nowadays, separation of CO 2 using liquid sorbents such as amine liquids is a mainstream CO 2 capture technology. This separation technique u...
Article
Full-text available
Carbon foams with different surface functionality and tailored texture characteristics were prepared from mixtures containing coal tar pitch and furfural in different proportions. The obtained materials were used as a host matrix for the preparation of zinc- and cobalt-mixed ferrite nanoparticles. The texture, morphology, phase composition, and the...
Article
Potassium Nickel hexacyanoferrate Prussian Blue Analogues (K-NiFe-PBAs) offer an excellent platform for efficient CO2 capture due to their porous nature and accessible channels. Herein, the effect of Ni:K atomic ratio on the structure and the CO2 storage capacity was studied by employing K-NiFe-PBAs with Ni:K ratio of ca. 2.5 and 12. The porosity a...
Data
Pore size distribution of silica samples having a different degree of hydrophobization: 1-MJ0, α=0 /hydrophilic/; 2 - MJ2, α=0.352; 3 - MJ4, α=0.7; 4 - MJ6, α=1.055 and 5 - MJ8, α=1.407, hydrophobic.
Article
Full-text available
Original method for direct preparation of nanocomposites of reduced gra-phene oxide and metal nanoparticles was developed. The technological scheme involves the preparation of graphene oxide by modified Hummers' method and the subsequent composite synthesis by simultaneous reduction of mixture of GO and the appropriate silver and copper salts. The...
Article
Full-text available
Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy and texture measurements based on nitrogen adsorption-desorption isotherms are combined to characterize silica aerogel granules with different degrees of hydrophobicity. The aerogels were prepared from tetraethoxysilane via a room temperature hydrolysis-gelation process, solvent exchange,...
Article
Full-text available
This work is focused on the preparation of Ni0.5M0.5Fe2O4 mixed ferrites (M = Zn or Cu), supported on nanoporous carbons materials. The carbon supports are obtained from various waste residues, such as peach stones from the canning industry and by-products from the low rank coals pyrolysis. X-ray diffraction (XRD), nitrogen physisorption, high-reso...
Article
Full-text available
Mesostructured alumina-carbon composites with different Al/C ratio were synthesized by soft template approach. Copper oxide active phase was deposited by incipient wetness technique. The composites and the catalysts were characterized by TG, XRD, low temperature N 2-adsorption, TEM, XPS. The catalytic behaviour in NO reduction with CO in 25-300 • C...
Preprint
Full-text available
Reduced graphene oxide (RGO) is a promising material for environmental protection, energy storage, but still very few papers have reported its use as catalyst support. In the present study we report the preparation of novel RGO-supported nickel-zinc ferrite catalyst for hydrogen production from methanol. The catalyst is highly active and reaches 10...
Article
This study presents the potential of Mobil Composition of Matter No.41 (MCM-41) and Hollow Mesoporous Silica (HMS) as an efficient drug delivery system for anticancer drug bicalutamide (BLT). Bicalutamide loaded nanoparticles were characterized by using X-ray diffraction (XRD), N2-physisorption, dynamic light scattering (DLS), TEM and attenuated to...
Article
Full-text available
A series of mesoporous cerium-iron binary oxides was prepared by a hydrothermal technique using CTAB as a template. The influence of the Fe/Ce ratio and the variations in the preparation techniques such as the type of solvent and the precipitation agent, the approach of the template release, and the temperature of calcination on the phase compositi...
Article
The present study evaluated the impact of doxorubicin encapsulation in chitosan-alginate nanoparticles on its stability, cytotoxic potential in multidrug resistant lymphoma cells (L5178 MDR1) and toxicity in H9c2 cardioblasts. The results indicated that the encapsulation stabilized the drug against degradation due to its inner location in nanoparti...
Article
Full-text available
Amine-functionalized mesoporous silica materials were prepared by sol–gel method in the system tetraethylortosilicate: bis[(3- trimethoxysilyl)propyl]amine (TEOS: BTPA). The hybrid amine functionalized silica materials were synthesized by co-condensation reaction between TEOS and BTPA precursors in acidic media. Soft template approach for pore form...
Article
The influence of the glycine-glycerol fuel mixing ratio on the structure, morphology, magnetic and catalytic properties of nanosized MnFe2O4 prepared by solution combustion method was investigated. The samples were synthesized using mixture of glycerol and glycine in the reducing power ratios 1:0, 0.75:0.25, 0.5:0.5, and 0.25:0.75. All samples were...
Article
High quality activated carbon was prepared using by-products from the pyrolysis of low rank coals as a precursor. The obtained carbon material was applied as a host matrix of nanosized MFe2O4 ferrites (M = Ni, Cu or Zn). XRD, Mössbauer and TPR analyses were performed for samples characterization and their catalytic behavior in methanol decompositio...
Article
This study is aimed at the development of intelligent approach for clean energy production via valorization of industrial waste by-products. The proposed scheme is based on the preparation of activated carbon based catalysts for methanol decomposition as a source of hydrogen. Peach stones from the canning industry and by-products from low-rank coal...
Article
Lomefloxacin (LF) is interesting as a model molecule from a safety point of view because of its high potential for serious adverse drug effects (i.e. phototoxic reactions). In this study, MCM-41 mesoporous silica nanoparticles (MCM-41) were loaded with lomefloxacin, aiming to overcome the drug’s intrinsic cytotoxicity. The good biocompatibility of...
Article
Herein, we present development of new pH-responsive drug delivery systems for D3-dopamine receptor agonist pramipexole, based on its encapsulation in MCM-41 mesoporous silica particles. Pramipexole loaded particles were further coated with chitosan and/or sodium alginate in order to modify drug release. The prepared pramipexole loaded nanoparticles...
Article
Full-text available
In this study, spherical hollow mesoporous silica (HMS) particles with average size of 550 nm were loaded with dopamine-receptor agonist pramipexole, as a model drug. High drug loading (55%) was achieved by its incorporation in the reservoir structure of HMS. The newly developed drug-delivery systems were further double-coated with bioadhesive poly...
Article
Full-text available
The formation of silicagel from sodium silicate solution obtained by alkaline autoclave treatment of copper slag was investigated. The influence of the parameters of the gelation process (type of acid used, the pH of the medium, and drying conditions) on the structure and properties of the resulting silicagel, were studied. Silicagels obtained unde...
Article
This study is aimed at the development of intelligent integrated scheme for full utilization of biomass for clean energy production. The proposed approach includes production of activated carbon based catalysts for methanol decomposition as a source of hydrogen, where both activated carbon and methanol, could be produced from biomass. In order to e...
Article
Activated carbons obtained from used motor oil mixtures with furfural or coal tar pitch were prepared and tested as a host matrix of zinc and/or iron oxide nanoparticles. The obtained composites were characterized by nitrogen physisorption, Boehm method, XRD, UV–Vis, FTIR, Moessbauer spectroscopy and temperature programmed reduction. The catalytic...
Article
Full-text available
A combination of thermal and mechanical (high energy ball milling) treatment was applied in an attempt to obtain polycrystalline mixed metal binary and ternary oxides of the type CoxZn1-xFe2O4 (x = 0; 0.25; 0.5; 0.75; 1). The synthetic procedure used successfully produced single-phased, homogeneous ZnFe2O4, CoFe2O4, and Co0.75Zn0.25Fe2O4, as well a...
Article
Mesostructured silica-carbon composites were synthesized by soft template approach and were characterized by TG, XRD, low temperature N2- adsorption, TEM, XPS. The CO2 adsorption capacities were investigated and the heats of adsorption were determined. The CO2 capture from flue gas was tested. The carbon-containing materials exhibit better performa...
Article
Copper catalysts supported on two types of silica–carbon composites- with ordered and with disordered architecture were investigated in reactions of NOx elimination. Disordered silica-carbons were prepared by sol–gel method and ordered composites by tri-constituent co-assembly of resol, silica oligomers and triblock copolymer. Two Si/C ratios were...
Article
Full-text available
Cobalt-silica-carbon composites were prepared by sol-gel method and tested as catalysts for NO reduction by CO. Active carbons of different texture parameters were used for synthesis of these composites. A cobalt-silica composite was also prepared for comparison purposes. The catalysts were characterized by low-temperature nitrogen adsorption, X-ra...
Article
Full-text available
Activated carbons (AC) from various waste agriculture precursors with different texture and surface characteristics were obtained by different preparation procedures. These AC were used as a host matrix of mono- and bi-component copper and cobalt nanoparticles. The effect of carbon properties on the formation of copper/cobalt phases was studied by...
Article
The effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/Al catalyst were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (X...
Poster
Full-text available
We have recently studied a series of alumina-supported catalysts containing Ce and/or Mn with various ratios as active phase. It was established that alumina supported mixed ceria-manganese catalysts have a potential in methanol decomposition and in an integrated process for NO reduction with methanol decomposition products. The best catalytic perf...
Article
First time a combined wet impregnation (WI)-organometallics chemical vapor deposition (OMCVD) strat-egy was applied for loading of 3–7 wt.% copper in mesoporous silica KIT-6 matrix nanoparticles withtailored particle size. XRD, HRTEM, nitrogen physisorption, UV–vis, XPS and temperature programmedreduction with hydrogen were used for the samples cha...
Article
A hybrid material from diatomite and activated carbon is prepared and modified by aluminum. On the basis of the unmodified and modified hybrid materials are synthesized Cu-supported catalysts by impregnation with different types of solution. The obtained supports and catalysts are characterized by XRD, XPS and SEM. The texture parameters are determ...
Article
The effect of low loading rare earth metal addition (RE= La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in NO reduction with CO was investigated. Samples RE/CuCo/Al (RE= La, Ce, Nd and Gd) were prepared by vacuum- evaporation. The rare earth modified as well as their "parent" catalysts were characteri...
Article
The effect of Ce addition to alumina-supported copper, cobalt, and copper-cobalt oxides with low loadings on the catalysts efficiency in NO reduction with CO was studied. The attention was focused on varying the impregnation procedure in the ternary-supported catalysts in order to determine the best catalyst as well as the reasons for the enhanced...
Article
Full-text available
Cu–Cr and Co–Cr oxide systems supported on Al2O3 and Al2O3 + SiO2 were studied in order to find the appropriate combination as a catalyst for the reduction of NO with CO with respect to the active phase and the nature of the support. The catalysts were prepared by successive impregnation of the support with solution mixtures of tartaric acid and ni...
Article
Full-text available
Depleted fullerene soot (DFS) with fullerene residue content of about 2.2-3.2% are investigated in order to elucidate the possibility for their use as support of catalysts in low-temperature reduction of NO with CO. Bimetalic copper-cobalt and copper-manganese oxides supported on DFS are prepared. All samples are characterized by chemical analysis,...
Article
Full-text available
The catalytic activity of mixed alumina-supported copper-manganese oxides during complete oxidation of CO, ethylacetate, toluene and benzene is investigated. The samples were prepared by impregnation of γ-Al 2O3 with aqueous solutions of copper and manganese formates at room temperature and subsequent calcination at 670 K .All samples have been obt...
Article
Full-text available
The influence of a sequence of copper and cerium oxide deposition on alumina, on the activity of the prepared catalysts in the reduction of NO with CO, was analyzed. The response curves of the reaction products were also analyzed and the rate-controlling step of the catalytic reactions were determined. The results show that in the case of AlCeCu wh...
Article
Full-text available
Samples of three series alumina supported catalysts of copper, manganese and copper-manganese oxides are investigated with respect to ozone decomposition at low temperatures. The catalysts are found to be active in the reaction studied and the most active are mixed copper-manganese catalysts—they do not change their activity for prolonged time. The...
Article
Full-text available
Alumina and alumina-silica supported copper-chromium and cobalt chromium oxides were investigated as cata-lysts for complete oxidation of methyl-ehyl-ketone and toluene. It was found the spinel phases formed to play a decisive role in the catalytic process. The nature of the support does not affect substantially on the activity of the samples.
Article
The adsorption capacity for NO of alumina-supported oxides and oxide-hydroxides of manganese have been studied. Two series of samples have been prepared by precipitation on gamma-alumina and appropriate thermal treatment. The samples have been characterized by adsorption methods, magnetic methods, electronic paramagnetic resonance (EPR), transient...
Article
Direct decomposition of NO over Cu-Mn oxide catalysts in both presence and absence of oxygen was studied. The catalysts are active in direct decomposition of NO at room temperature. No N20 is formed during the reaction. When conversion proceeds in the absence of oxygen in the gas phase, part of the oxygen evolved during NO decomposition leads to se...
Article
Full-text available
A copper-manganese oxide catalyst prepared by coprecipitation of copper and manganese hydroxides with a Cu:Mn ratio of 1:1 was investigated in order to elucidate the mechanism of NO conversion with CO. A scheme for the NO-CO interaction based on the redox couple Cu2+ +Mn3+ Cu++Mn4+ is proposed.
Article
The activity of the mixed copper-manganese oxides CuO-MnO{sub x} (1.5 < x < 2), obtained by coprecipitation and activated at 300 C, has been studied for CO-NO and CO-NO-O{sub 2} reactions. As shown by magnetic susceptibility data, X-ray diffraction, FTIR spectra, and catalytic tests, an interaction between CuO and MnO{sub x} with formation of a dis...
Article
The activity of the mixed copper–manganese oxides CuO–MnOx (1.5<x<2), obtained by coprecipitation and activated at 300°C, has been studied for CO–NO and CO–NO–O2 reactions. As shown by magnetic susceptibility data, X-ray diffraction, FTIR spectra, and catalytic tests, an interaction between CuO and MnOx with formation of a disordered mixed oxide wi...
Article
Full-text available
Copper-manganese oxides with a Cu:Mn atomic ratio of 1∶1 have been studied for low-temperature oxidation of CO. The catalyst treated at 300°C showed the best activity in the CO−O2 reaction.
Article
Full-text available
The low temperature oxidation of CO over MnO2 containing samples for batteries has been investigated. It is found that the samples contain compositional and hydrate water and Mn4+, Mn3+, Mn2+ ions. The high efficiency is due to Mn4+ content. CO MnO2, . , Mn4+, Mn3+, Mn2+. Mn4+.

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