Vlad Gun'ko

Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine · Amorphous and Structurally Ordered Oxides

Comparative characterization of the particulate morphology and texture of various silicas (fumed silicas, silica gels, ordered mesoporous silicas) and carbons (chars and activated carbons, AC) is of interest from both theoretical and practical points of view since it allows one better understanding of advantages and disadvantages of various adsorbe...

Magnetosensitive biochars were prepared with mechanochemical ball-milling of lignin and blast furnace dust with further pyrolysis at 800 °C under an inert gas atmosphere. The physicochemical and sorption characteristics of the materials were analyzed using several techniques: low-temperature nitrogen adsorption–desorption, X-ray powder diffraction,...

The characteristics and properties of fumed oxides depend strongly on various external actions that is of importance from a practical point of view. Therefore, gelation or high-pressure cryogelation (HPC) of aqueous media pure or with 0.1 M NaCl, and mechanochemical activation (MCA) of dry or wetted powders of individual (silica, alumina, their mec...

Hybrid adsorbents with carbon/silica, carbon/metal oxide/silica, and carbon/metal/silica could be of interest from a practical point of view since they can effectively adsorb both polar and nonpolar compounds. Therefore, mesoporous silica gel Si–60 modified by carbonization acetylacetone or Ti, Zn, Ni, Co, Cr, Zr acetylacetonates has been studied u...

It has been assumed that nanoparticle/aggregate/agglomerate structure, texture and surface characteristics of hydrophobic nanosilica AM1 treated with certain amounts of arginine and water may provide better conditions for methane adsorption compared to AM1 alone. Nanosilica and composites are characterized using adsorption, desorption, microscopic,...

Hypothesis Various nanosilica characteristics depend on hydrophobization strongly affecting interfacial phenomena. Is it possible to prepare hydrophilic samples with hydrophobic silica (AM1) alone and in blends with hydrophilic one (A–300)? It can be done with addition of a small amount of water to the powders which then are mechanically treated....

The most important results of the scientific studies, carried out by the Institutes of the National Academy of sciences of Ukraine in the frames of the program for scientific research of the NAS of Ukraine "New Functional Substances and Materials for Chemical Engineering" in 2017-2021, are summarized. In the result of fulfillment of the projects of...

New hybrid composite materials were prepared by polymerization of resorcinol-formaldehyde resins in the presence of bentonite with various contents of polymer and water, and then exposed to pyrolysis in an inert atmosphere at 800 • C. The influence of the filler and synthesis method on the morphological, textural and structural characteristics has...

Nanoporous microspheres with divinylbenzene (DVB), styrene (St), and lignin were synthesized by an emulsion-suspension polymerization method. Several types of lignins were used: (1) kraft lignin before (L-unmod) and after modification with methacryloyl chloride (L-Met) and (2) low-molecular-weight kraft lignin unmodified (LWL-unmod) and modified wi...

It is well known that interaction of hydrophobic powders with water is weak, and upon mixing, they typically form separated phases. Preparation of hydrophobic nanosilica AM1 with a relatively large content of bound water with no the formation of the separated phases was the aim of this study. Unmodified nanosilica A-300 and initial AM1 (A-300 compl...

In this work, a role of the number of free silanol groups at a nanosilica surface (specific surface area S_BET = 250 m²/g, initial amount of silanols α_ОН = 0.60-0.62 mmol/g) was analyzed in interaction with poly(vinyl pyrrolidone) (PVP) vs. the degree (Q_TMS) of silica hydrophobization by hexamethyldisilaza...

Nanoporous microspheres with divinylbenzene (DVB), styrene (St), and lignin were synthesized by an emulsion-suspension polymerization method. Several types of lignins were used: (1) kraft lignin before (L-unmod) and after modification with methacryloyl chloride (L-Met) and (2) low-molecular-weight kraft lignin unmodified (LWL-unmod) and modified wi...

A method has been proposed to control the macro- and micro-wetting properties of hydrophobic surfaces through changes in the roughness due to modifying siloxane films with silica microparticles (MP). An experimental and theoretical analysis of macro- and micro-wettability dependence on the roughness of a film surface was carried out by combination...

The present review is aimed to familiarize researchers with modified Nguyen-Do method for accurate and thorough analysis on textural structure on the basis of low-temperature nitrogen adsorption-desorption data. A deep analysis offers scope for conceptual foresight of properties of adsorbents, catalysts, active compounds carriers etc. The method is...

A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption–desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsor...

SiO2@PDMS and CeO2–ZrO2–SiO2@PDMS nanocomposites were prepared and studied using nitrogen adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), measurements of advancing and receding contact angles with water, and microcalorimetry. The pore size distributions indicate that the textural character...

Methane adsorption onto hydrated (0.1 g/g) initial and compacted nanosilica A-50 and compacted A-50/hydrophobic AM1 (based on nanosilica A-300) and water behavior vs. temperature were analyzed using ¹H NMR and theoretical methods. Methane adsorption increases with temperature because of changes in structure of mobile water. Stronger compaction of A...

In this paper adsorptive removal of hazardous dye C.I. Reactive Black 5 from aqueous solutions was investigated using the mixed silica–alumina oxides including of 4% SiO2 and 96% Al2O3 as well as 97% SiO2 and 3% Al2O3. The kinetic studies revealed that with the increasing initial dye concentration from 10 to 30 mg/l and contact time from 1 to 240 m...

Wastewaters containing organic and inorganic contaminants such as dyes, heavy metal ions, salts, and surfactants are considered to be a serious environmental problem in human society. Adsorption is the most popular technique for wastewater treatment. In this paper, a new mesoporous silica-alumina oxide (97% SiO2, 3% Al2O3) synthesized by pyrogenic...

The increasing availability of various types of technical lignins as result of the emergence of new biorefinery technologies has boosted the interest in the commercialization of lignin-based materials. Here we suggest a novel method for the preparation of uniform porous microspheres through emulsion-suspension polymerization of various technical li...

A series of silica gels (Si-40, Si-60, Si-100) and related carbon–silica gels, prepared by carbonization of CH2Cl2 at a surface of silica gels at 550 °C, characterized using FTIR/PAS, SEM/EDX, and nitrogen adsorption, was investigated upon interactions with polar (water, dimethylsulfoxide), weakly polar (chloroform), and nonpolar (n-hexane, n-decan...

This work deals with effects of polymer molecular weight, Wm, below the entanglement threshold, Wm,e, on molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto silica particles, employing differential scanning calorimetry (DSC) and two dielectric techniques, broadband dielectric spectroscopy (BDS) and thermally stimulated depolarization cu...

Interactions of human serum albumin (10 wt.% H2O and 0.3 wt.% sodium caprylate) with doxorubicin hydrochloride (1 wt.%) were studied alone or with addition of HCl (3.6 wt.% HCl) using ¹H NMR spectroscopy. A model of hydrated HAS/12DOX was calculated using PM7 method with COSMO showing large variations in the binding constant depending on structural...

The adsorption and electrokinetic properties, as well as the stability of the mixed oxide suspensions in the absence and presence of poly(vinyl alcohol)-PVA were studied. Two alumina-silica-titania (AST) oxides were used: AST50 (TiO2: 50%, SiO2: 28%, Al2O3: 22%) and AST71 (TiO2: 71%, SiO2: 8%, Al2O3: 21%). All measurements were carried out in the p...

In this study, a set of CoFe2O4/SiO2/TiO2 nanocomposites was synthesized. The total concentration of metals (Co + Fe) was varied from 3 to 9 mmol with respect to 1 g of SiO2. Titania was formed in two concentrations — 2 and 4 mmol/g. The structure of the samples was analyzed by application of XRD, UV–vis spectroscopy, magnetometry, SEM, low-tempera...

A series of TiO2-ZrO2/SiO2 nanocomposites were synthesized using a liquid-phase method and characterized by various techniques, namely, nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy, and photon correlation spectroscopy (PCS). It w...

The behavior of interfacial liquids adsorbed alone or co-adsorbed as miscible or immiscible pairs or triples strongly differs from that for bulk liquids because of several effects , and the main of them is the confined space effect. In the confined space of pores the mobility of molecules decreases, the activity of solvents is reduced, and the free...

Bisphenol A (BPA) is worldwide used to produce plastics and/or epoxy-based foodstuff packages. But it is known that this compound is considered as a quite toxic contaminant due to (1) its similarity to the hormone estrogen and (2) its universal use in many industrial proceses. In our study the photodegradation of BPA stimulated by tin(IV) oxide-mod...

Using the method of electrochemical analysis the charge capacity of electrochemical cells with cathode material on the bases of simple and mechanically activated mixtures 0,2α-Fe₂O₃+0,8Al₂O₃, 0,2α-Fe₂O₃+0,8SiO₂ та 0,2γ-Fe₂O₃,8SiO₂ has been...

Carbon particles containing iron, nickel and cobalt magnetic nanoparticles (MNP) were synthesized from polystyrene and metal salts using pyrolysis method. The morphology, structural features and magnetic properties of the particles were investigated by emission scanning electron microscope, X-ray diffraction, thermogravimetry and vibrating scanning...

A series of microporous carbons (chars) containing various amounts of magnetic Ni nanoparticles were prepared using a simple procedure. The resorcinol-formaldehyde polymers containing nickel(II) acetate was carbonized to produce chars (labelled as Ni/C-20, Ni/C-35 and Ni/C-50). All chars were characterized by X-ray diffraction, Raman spectroscopy,...

Interactions of water, methane, HCl, C6H6, F3CCOOD, and hyaluronic acid with fullerite C60/C70 and multi-walled carbon nanotubes (MWCNT) were studied in various media using 1H NMR spectroscopy. The materials were characterized using microscopy, differential scanning calorimetry, Raman spectroscopy, and quantum chemical methods. Water with weakly (W...

Untreated or partially purified effluents from the textile, paper, plastic, leather, food and cosmetic industries containing dyes and pigments are a serious environmental problem. Therefore, in this paper, adsorptive removal of acid (C.I. Acid Orange 7, AO7), reactive (C.I. Reactive Black 5, RB5) and direct (C.I. Direct Blue 71, DB71) dyes from aqu...

Effects of silica and titania nanoparticles of a wide range of size (8 – 80 nm in diameter for primary particles) and specific surface roughness (specific surface area, SBET, 25 – 342 m2/g) on interfacial dynamics of linear polydimethylsiloxane (PDMS) in nanocomposites (NCs) of the core–shell type were studied by employing differential scanning cal...

The effects of conformerisation and internal molecular dynamics (IMD) of n-dodecane conformers on energy transfers between gas and liquid phases are investigated. Bond energies, Gibbs free energies of internal dynamics of a set of n-dodecane conformers, and energies of the molecules colliding with the surface of an n-dodecane nanodroplet are studie...

Crystalline and electronic structures of SiO2/Al2O3 mixtures have been analyzed using X-ray diffraction (XRD) and ultra-soft X-ray emission spectroscopy (USXES). Comparison of ultrasoft X-ray emission AlLα-, SiLα- and OKα-bands redistribution Alsp-, Sisp- and Op-valence electrons when changing the mass ratio (0,23Al2O3+0,77 SiO2;, 0,30Al2O3+0,70SiO...

The adsorption of non-ionic polysaccharide guar gum (GG) in the presence of surfactants (anionic SDS, non-ionic TX-100, cationic CTAB and their equimolar mixtures) from their NaCl solutions onto an alumina surface (Al2O3) was studied spectrophotometrically. This study is important in light of the many disagreements concerning the structure and beha...

New series of carbon/silica gel nanocomposites, carbosils, prepared by the carbonization of starch bound to silica gel, and carbosils additionally silylated with octadecyldimethylchlorosilane were synthesized. These materials were applied as adsorbents in solid-phase extraction of explosive nitrate esters and nitroaromatics from aqueous solutions....

The effects of temperature and conformerisation on the evaporation/condensation coefficient (beta) and the evaporation rate (gama) for n-dodecane nano and micro-droplets are analysed using quantum chemical DFT calculations for several ensembles of conformers of n-dodecane molecules in the gas and liquid phases. To highlight the underlying physics o...

Crystalline and electronic structures of SiO2/γ-Fe2O3 mixtures have been analyzed using X-ray diffraction (XRD) and ultra-soft X-ray emission spectroscopy (USXES). The energy redistribution of Fesрd, Sisp and Op valence electrons due to changes in the mass ratio (0,2 SiO2 + 0,8 γ-Fe2O3 , 0,5 SiO2 + 0,5 γ-Fe2O3, 0,8 SiO2 + 0,2 γ-Fe2O3) of SiO2 and α...

The evaporation/condensation coefficient (β) and the evaporation rate (γ) for n-dodecane vs. temperature, gas pressure, gas and liquid density, and solvation effects at a droplet surface are analysed using quantum chemical density functional theory calculations of several ensembles of conformers of n-dodecane molecules in the gas phase (hybrid func...

Effects of changes in the hydration degree of lactic acid bacteria (LAB), dispersion media composition and interactions with silica TS 100 and silylated silica gel Sipernat 50 were analysed using 1H NMR and DSC methods. Several types of water were found in wetted LAB. There were strongly and weakly bound waters determined from changes in Gibbs free...

A new adsorbent consisting of fumed, mixed alumina, silica and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapour deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper the adsor...

A new adsorbent consisting of fumed, mixed alumina, silica, and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapor deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper, the adso...

Resorcinol-formaldehyde resin (RFR) was synthesized as a porous material characterized by specific surface area of 140 m2/g and pore volume of 0.59 cm3/g with major proportions of broad mesopores and macropores. The interfacial behavior of water at low (h = 0.05 g of water/gram of dry RFR) and high (h = 2 g/g) hydration degrees depends on temperatu...

Fumed silica, initial alumina blend, after mechanochemical activation (MCA), and fumed binary silica/alumina (SA) were studied using infrared spectroscopy, X-ray diffraction (XRD), ultrasoft X-ray emission (USXE) spectroscopy (giving emission bands Si Lα, Al Lα and O Kα related to valence electron transfer onto core levels) and quantum chemistry. T...

The adsorption and electrokinetic properties as well as the stability of the AST71 suspension in the absence and presence of polyvinyl alcohol (PVA) were examined. AST71 is a mixed oxide of alumina, silica and titania. All measurements were carried out as a function of solution pH and the polymer molecular weight. The pooled result analysis showed...

Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core–shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the fille...

Nanocomposites based on sequential semi-interpenetrating polymer network (semi-IPN) of cross-linked polyurethane and linear poly(2-hydroxyethyl methacrylate) with 0.25 and 3 wt % of nanosilica filler were prepared and investigated. The unmodified silica, carboxyl-modified, and amino-modified silica were used in an attempt to control the microphase...

The influence of solution pH (in the range 3-9) on the adsorption of polyacrylic acid (PAA) on the mixed silica-alumina surface (SA-3: SiO2 97 %-Al2O3 3 % and SA-96: SiO2 4 %-Al2O3 96 %) was investigated. The following methods were applied in experiments: spectrophotometry, viscosimetry, potentiometric titration, and microelectrophoresis, which ena...

Modeling of water structure at a surface of different adsorbents, as well as an influence of dissolved compounds or co-adsorbates on bound water, is of importance to understand the temperature dependence of the characteristics of bound water, especially at T < 273 K, in comparison with bulk water. 1H NMR spectra giving useful information on the wat...

Products of resorcinol-formaldehyde resin carbonization (chars) are characterized by different morphology (particle shape and sizes) and texture (specific surface area, pore volume and pore size distribution) depending on water content during resin polymerization. At a low amount of water (Cw = 37.8 wt.%) during synthesis resulting in strongly cros...

Evaporation rate (gamma) of molecules from Diesel fuel molecular clusters and nanodrops is analysed using the solvation model SMD within quantum chemistry, the kinetic gas theory, and experimental or extrapolation data on temperature dependence of the enthalpy of evaporation and liquid density. The SMD/HF or SMD/DFT with the same 6-31G(d,p) basis s...

Crystalline structure of nanotitania (anatase, rutile) and the morphology of primary and secondary particles can be regulated using low-amount additions of Na2SO4 (or K3PO4), NaOH or Н2О2. Anions SO42− and PO43− can bind to Ti-containing species that lead to the formation of anatase nanocrystallites with sulfate and phosphate functionalities. Accor...

Understanding of both the textural and functionality changes occurring during (mesoporous) polysaccharide carbonisation at the molecular level provides a deeper insight into the whole spectrum of material properties, from chemical activity to pore shape and surface energy, which is crucial for the successful application of carbonaceous materials in...

Nanocomposites with nanosilica A380 (SBET = 378 m2/g) and grafted ZnO or/and zinc silicate were prepared using zinc acetate adsorbed onto nanosilica and then treated at 600-900 °C. The samples studied using a variety of methods demonstrated the dependences of the textural and structural characteristics and phase transformations on the amounts of ad...

Two sets of hybrid polyurethane-poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer networks - nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH, NH2 or CH=CH2 groups were prepared. Combined atomic force microscopy, infrared spectroscopy, thermally stimulated depolarisation current, differential sc...

The nondestructive, covalent reactivity of single-layer graphene oxide (SLGO) and hydrazine-reduced graphene oxide (rGO) in relation to its 3-dimensional geometry has been previously considered for various chemical reactions. However, the capability of the modified system to undergo additional chemistry is now demonstrated through an in-situ polyco...

Detailed analysis of the interfacial behavior of water and weakly polar or nonpolar organics adsorbed alone or co-adsorbed onto activated carbons (AC) at different temperatures is a complex problem important for practical applications of adsorbents. Interaction of water, 1-decanol, and n-decane with AC possessing highly developed porosity (pore vol...

The spectra and kinetics of fluorescence decay of 1,2-benzanthracene (1,2-BA) molecular clusters adsorbed in nanoporous borosilicate glasses were investigated. It has been shown that the type of the decay kinetics of delayed fluorescence is determined by the annihilation of triplet excitons in crystalline and percolation clusters. The influence of...

The interfacial and temperature behavior of n-decane bound to weakly hydrated nanosilica A-400 (initial, heated or compacted) or silica gel Si-60 was studied using low-temperature 1H NMR spectroscopy applied to static samples that allowed us to observe signals only of mobile decane and unfrozen water molecules. For deeper insight into the phenomena...

The influence of solution pH and polymer molecular weight on the stability of mixed alumina-silica oxide suspension in the absence and presence of polyacrylic acid (PAA) was studied. The composition of the adsorbent was: Al2O3 (96%) and SiO2 (3%). To obtain changes in the stability of the investigated systems as a function of time the turbidimetry...

A series of carbon-iron-silica (CIS) composites (carbonizates) were prepared by carbonization of phenol-formaldehyde resin - Fe(III) acetylacetonate mixtures with addition of different amount of nanosilica A380 and compared with a composite prepared without silica (CFe composite). The characteristics of the composites differ because two type iron s...

The interfacial behavior of silicone oils Oxane 1000 and Oxane 5700 (polydimethylsiloxanes, PDMS) interacting with dried or hydrated (hydration h=0.005 or 0.1g/g) silica gels Si-60 and Si-100 or nanosilica A-400 was studied using low-temperature (1)H NMR spectroscopy over the 210-310K range. Broadening of the melting temperature range toward both s...

Adsorption of myoglobin (Mb), bovine serum albumin (BSA) and γ-globulin (GG) onto activated carbons (ACs) with different pore size distributions, and poly(vinyl alcohol) (PVA) monolithic cryogels containing AC particles was studied. The highest initial rate of Mb adsorption was observed for AC having the largest specific surface area (1939 m2 g−1)...

Experimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and f...

To analyze the influence of silica surface modification and confined space effects on specific interactions of divalent and trivalent metal cations with surface functionalities, three different high surface area silicas with different pore size distributions were modified with the following organosilanes: 3-aminopropyltriethoxysilane, N-(2-aminoeth...

A set of glutaraldehyde (GA) cross-linked poly(vinyl alcohol)/activated carbon (PVA/GA/AC) composites prepared in the form of monolithic rods using a cryogelation technique and studied using adsorption, mercury porosimetry, SEM and quantum chemistry methods displays porosity similar to that of PVA/GA cryogel at a high GA content (content ratio GA/A...

Water, as a probe liquid bound in model systems (highly disperse hydroxyapatite - protein composites as a model of the main components of bones) and rat bone tissues healthy and affected by osteoporosis occurred due to experimental Alzheimer's disease (EAD), has been investigated using low-temperature (1)H NMR spectroscopy, NMR cryoporometry, TG/DT...

C/AST/PEG nanocomposites with fumed AST (89 wt % Al2O3, 10 wt % SiO2, 1 wt % TiO2), activated carbon, and poly(- ethylene glycol), PEG, were prepared in a wide range of PEG and C/AST (1 : 9) contents. Thermal transitions (mainly in a PEG phase) were investigated by differential scanning calorimetry. The dynamic behavior was investigated by thermall...

The extensive oxygen-group functionality of single-layer graphene oxide proffers useful anchor sites for chemical functionalization in the controlled formation of graphene architecture and composites. However, the physicochemical environment of graphene oxide and its single-atom thickness facilitate its ability to undergo conformational changes due...

Low-temperature (1)Н NMR spectroscopy was used to study states of water bound to phosphoric and phosphonic acids (phosporus oxyacids, POA) alone or adsorbed onto nanosilica OX-50 (specific surface area S(BET)=52 m(2)/g) or A-300 (S(BET)=297 m(2)/g). Concentrated solutions or weakly hydrated solid POA or dried silica/POA powders placed in CCl(4) med...

The joint adsorption of water and methane in pores of the synthetic carbon adsorbent with specific surface area of 3463 m2/g was studied by 1H NMR spectroscopy. It was shown that during adsorption of water and methane in pores of activated carbon AC86 under conditions of low surface filling the adsorbate molecules are localized not only in micropor...

Single-layer graphene oxides (SLGOs) undergo morphological changes depending on the pH of the system and may account for restricted chemical reactivity. Herein, SLGO may also capture nanoparticles through layering and enveloping when the pH is changed, demonstrating potential usefulness in drug delivery or waste material capture.

Chemical and structural factors of carbon materials affect their activity in adsorption and surface reactions in aqueous media. Decomposition of hydrogen peroxide studied is a probe reaction for exploring parameters of carbons that might be involved, such as specific surface area, nitrogen and oxygen doping and conformational changes. To date, a de...

The porous structure and the state of the water are two main factors which define the vast applications of hydrogels in the life science arena. The structural characterisation and water state in hydrogels produced by the cryogelation of poly(hydroxyethyl methacrylate) and gelatine were undertaken using different techniques. Images obtained using co...