Władysław Janusz - Academia.edu (original) (raw)

Papers by Władysław Janusz

Electrochimica Acta, 2000

The growth of leuco-methylene blue (LMB) films and their electrodissolution have been studied by ... more The growth of leuco-methylene blue (LMB) films and their electrodissolution have been studied by voltammetry and piezogravimetry using bare gold (Au) and sulphur modified gold (Au-S) electrodes in methylene blue (MB + ) solutions. The growth rate anisotropy has been found for thin LMB films formed on Au-S modified electrodes and on bare Au electrodes. Excellent agreement has been found between the experimental equivalent molmass of thin LMB films deposited from fluoride solutions on Au, with general formula

Surface Chemistry in Biomedical and Environmental Science, 2006

ABSTRACT Different surface sites of silica, alumina, titania, and related mixed oxides, and pre-a... more ABSTRACT Different surface sites of silica, alumina, titania, and related mixed oxides, and pre-adsorbed poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG), affect the interaction with Ni(II), Cd(II), and Pb(II) studied using adsorption and potentiometric titration methods. Bridging hydroxyls (Brönsted acid sites) capable of taking part in ion-exchange reactions, and pre-adsorbed polymers, enhance the adsorption of metal ions at pH < 7. At pH > 7 PVA adsorbed on silica slightly enhances the adsorption of metal ions but pre- adsorbed PEG gives the opposite result. PEG has only electron-donor functionalities (C-O-C) which reduce the number of possible adsorption sites. PVA has COH groups with both electron-donor and proton-donor properties, which can effectively interact with metal ions and their hydroxy species.

Chromatographia, 2014

The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the... more The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, N-methylformamide and N,N-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase. During the study we found that there is no linear correlation between EOF velocity of the mobile phase and single variables such as zeta potential or dielectric constant or viscosity. However, there is quite strong linear correlation between EOF velocity of the mobile phase and variable obtained by multiplying zeta potential of the stationary phase-mobile phase interface, by dielectric cons...

Microporous and Mesoporous Materials, 2005

ABSTRACT A series of carbon/silica gel (CS) samples at different concentration of phosphorus comp... more ABSTRACT A series of carbon/silica gel (CS) samples at different concentration of phosphorus compounds (CP) was synthesized by carbonization of glucose in the presence of phosphoric acid on silica gel Si-100 in a rotary reactor in a nitrogen atmosphere at 500°C (5h) at a heating rate of 2 and 4°C/min (from 20 to 500°C). Prepared CS samples were studied using adsorption (nitrogen, Cd(II)), thermal analysis, titration, and spectroscopic (FTIR, XRF, XRD) methods in gaseous and liquid media. Contributions of nano-, meso-, and macropores to total porosity and specific surface area depend strongly on the CP value and the heating rate. An increase in the CP value enhances the negative surface charge density and the adsorption of Cd(II) characterized by a bi- or trimodal distribution function of Cd(II) binding constant f(Kn) over a broad Kn range.

Microporous and Mesoporous Materials, 2006

Two series of carbon/silica (carbosil, CS) adsorbents were prepared on the basis of silica gel as... more Two series of carbon/silica (carbosil, CS) adsorbents were prepared on the basis of silica gel as a matrix and glucose as a carbon precursor by pyrolysis of 0.01, 0.03, 0.05mol of glucose per 10g of mesoporous silica gel Si-100. Initial samples (CSn) were modified with hydrogen sulfide (CSn/S). On preparation of the CSn series, only nitrogen (100cm3/min) was used as a carrier gas. The CSn/S samples were prepared in the nitrogen (90cm3/min) and hydrogen sulfide (60cm3/min) atmosphere. Carbosils were studied using adsorption (nitrogen, butane, ammonia, and Ni(II)) and thermal analysis methods. During glucose pyrolysis in the hydrogen sulfide atmosphere the chemical reactions between glucose and hydrogen sulfide take place that leads to a greater yield of carbon deposits. The presence of sulfur on the carbosil surface has a negative effect on butane adsorption and the opposite effect is observed on the adsorption of ammonium and Ni(II).

Langmuir, 2002

ABSTRACT Pristine fumed silica and powders with dried residuals of centrifuged aqueous suspension... more ABSTRACT Pristine fumed silica and powders with dried residuals of centrifuged aqueous suspensions of fumed silica, silica/PVP, or silica/protein were studied using nitrogen adsorption and IR spectroscopy methods. The aqueous suspensions of silica with added polymers, surfactant, or ethanol were investigated by means of photon correlation spectroscopy, 1H NMR, and adsorption methods. The impact of polymers on the suspension and dried powder characteristics depends on the adsorption mechanism and the conformation of polymer molecules (globular or unfolded) due to strong or weak intramolecular interactions. Globular proteins interacting with silica through the flocculation mechanism affect the textural characteristics of dried powders more weakly than do unfolded proteins but strongly impact the aqueous suspension, thus shifting the swarm size distribution toward larger sizes compared to the size distribution of poly(vinylpyrrolidone), PVP. PVP is adsorbed in the unfolded state and gives a nearly monomodal particle size distribution (PSD). The ionogenic surfactant 1,2-ethylene-bis(N-dimethyl carbodecyloxymethyl)ammonium dichloride at CAet < 0.01 wt % and ethanol at CEtOH = 10−50 wt % impacts the silica's PSD-dependent nonlinearly on the concentrations and pH.

Journal of Thermal Analysis and Calorimetry, 2011

Mechanochemical activation of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide syst... more Mechanochemical activation of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide system in various media (air, water, and ethanol) has been studied. Powder X-ray diffraction, nitrogen adsorptiondesorption, thermogravimetric and chemical analysis, FTIR and Raman spectroscopy, and scanning electron microscopy have been used for research of prepared milled samples. The electrokinetic properties (dependence zeta potential-pH, position of isoelectric point) of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide system, synthesized via mechanochemical treatment in various medium, in aqueous solutions of electrolytes also have been determined. Initial, milled, and spent samples are characterized with the help of XRD, FTIR and Raman spectroscopy, and SEM and adsorption of nitrogen. The catalytic properties of vanadium-molybdenum oxide composition activated in different media have been investigated in reaction of oxidation dehydrogenation of propane.

Journal of Radioanalytical and Nuclear Chemistry Articles, 1988

The surface charge and adsorption densities of Na+ and Cl– ions at the zirconium dioxide/electrol... more The surface charge and adsorption densities of Na+ and Cl– ions at the zirconium dioxide/electrolyte interface have been determined as a function of pH for 0.1, 0.01 and 0.001 M solutions of NaCl. Using potentiometric titration of the surface hydroxy groups, it was found that the point of zero charge occurred at pH 4.3±0.15. The results are discussed in terms

Journal of Materials Science, 1991

... 115 (1987) 555. 11. AL DAWIDOWlCZ, J. MATUSEWlCZ and J. WYSOCKA-LISEK, Talanta, 36 (1989) 586... more ... 115 (1987) 555. 11. AL DAWIDOWlCZ, J. MATUSEWlCZ and J. WYSOCKA-LISEK, Talanta, 36 (1989) 586 12. JA DAVIS, RO JAMES and JO LECKIE, J. Colloid Interface Sci. 63 (1978) 480. Received 2 February and accepted 30 November 1990 4868

Journal of Colloid and Interface Science, 2000

Journal of Colloid and Interface Science, 2006

Successive interaction of different pairs of water-soluble polymers (poly(ethylene glycol) (PEG),... more Successive interaction of different pairs of water-soluble polymers (poly(ethylene glycol) (PEG), poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA)), proteins (bovine serum albumin (BSA), ovalbumin, gelatin, and ossein), and smaller organics such as lecithin (1-stearoyl-2oleoyl phosphatidylcholine, SOPC) and Aethonium (1,2-ethylene-bis(N-dimethyl carbodecyl oxymethyl) ammonium dichloride) with nanosilicas A-300 (S BET = 232 and 297 m 2 g −1 ) and A-50 (S BET = 52 m 2 g −1 ) was studied using dynamic light scattering, adsorption, and infrared (FTIR) spectroscopy methods. Time-dependent rearrangement of particle size distributions (PSDs) depicts appearance of both smaller and larger aggregates for silica/PEG(I-first adsorbate)/BSA(II-second adsorbate) and silica/PVP(I)/BSA(II) (i.e., BSA adsorbs onto PEG/silica or PVP/silica) than that for silica/organic compound I. However, in the cases of PVA(I)-BSA(II) and PVA(I)-SOPC(II) a similar effect is not observed because only increased aggregation occurs. The successive equilibrium adsorption of similar pairs shows a diminution of the adsorption of the second compound (gelatin, ovalbumin) with increasing amount of the first adsorbed polymer (PEG or PVP). (V.M. Gun'ko). induced conformational changes, chemical and morphological characteristics of solids, and characteristics of the media (pH, salinity, concentrations of polymers and solid particles, and temperature) . The interfacial phenomena are more complex for mixtures of adsorbates, especially macromolecules, with strongly different spatial and chemical structures. Results of their competitive adsorption depend on their mobility and affinity to a surface as well as on the mentioned factors and applied external electrical or mechanical forces governing the interfacial layer structure with time. Smaller molecules, adsorbing faster (because of limitation of this process by the diffusion rate) than larger but slower ones, can be displaced by the latter if pores of solid particles are much larger than molecules. This phenomenon, known as the Vroman effect, related to the adsorption of proteins and discovered for fibrinogen competing with other plasma proteins [1], has been observed for blends of various proteins . The Vroman effect has substantial significance for the biocompatibility of biomaterials because it 0021-9797/$ -see front matter

Journal of Colloid and Interface Science, 1997

charge through the acid-base reactions of surface hydroxyl Adsorption of the monovalent cations C... more charge through the acid-base reactions of surface hydroxyl Adsorption of the monovalent cations Cs / and Na / from mixed groups, solutions of NaCl and CsCl at the TiO 2 (anatase)/water interface was studied. Higher adsorption of Cs / than Na / was observed from solutions of similar electrolyte concentration. The surface

Journal of Colloid and Interface Science, 2011

The structural, textural, and adsorption characteristics of mechanochemically activated (MCA) fum... more The structural, textural, and adsorption characteristics of mechanochemically activated (MCA) fumed silica A-300 as dry or water, ethanol, or water/ethanol-wetted powders (0.5 g of a solvent per gram of silica) in a ball mill for 1-6 h were studied in comparison with those of the initial powder. The MCA treatment enhances bulk density (ρ(b)) of the powder (from 0.045 g/cm(3) for the initial silica to 0.4 g/cm(3) for 6 h-MCA-treated water-wetted silica) depending on medium type and MCA time (t(MCA)). Stronger effects are observed for the MCA treatment of water-wetted silica than of dry or ethanol- or water/ethanol-wetted samples. The MCA treatment weakly affects the specific surface area (S(BET)). However, void (pore) size distribution, porosity, particle aggregation and size distribution in aqueous suspension, behavior of interfacial water, properties of poly(vinyl alcohol)/silica composites and adsorption of gelatin depend more strongly on the t(MCA) and ρ(b) values. Some of the observed changes in the characteristics (e.g., gelatin adsorption) depend on the ρ(b) value but are independent of the medium type used on the MCA. Other characteristics are nonlinear functions of both t(MCA) and ρ(b) values.

Journal of Colloid and Interface Science, 2002

Cab-O-Sil HS-5 grafted with 3aminopropyldimethylsilyl (APDMS), butyldimethylsilyl (BDMS), octadec... more Cab-O-Sil HS-5 grafted with 3aminopropyldimethylsilyl (APDMS), butyldimethylsilyl (BDMS), octadecyldimethylsilyl (ODDMS), and trimethylsilyl (TMS) groups of different concentrations were studied using photon correlation spectroscopy, electrophoresis, potentiometric titration, and nitrogen adsorption methods. Calculations of both electrophoretic mobility and ζ potential were performed taking into consideration the topological structure of "porous" aggregates of primary particles of fumed silica using two different approaches. Changes in surface charge density and the textural, aggregative, and electrophoretic characteristics of modified silicas depend on the type of grafted OSC, its chain length, polarity, and surface concentration. Particle swarms of initial and modified silicas in aqueous suspension are typically characterized by bimodal size distributions between 20 and 300 nm (aggregates) and 1-3 µm (agglomerates of aggregates). The difference between parameter values computed according to the Smoluchowski theory and improved approaches increases with increasing pH and is concordant for both mobility and ζ potential. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2005

Several series of fumed silicas and mixed fumed oxides produced and treated under different condi... more Several series of fumed silicas and mixed fumed oxides produced and treated under different conditions were studied in gaseous and liquid media using nitrogen and water adsorption-desorption, mass spectrometry, FTIR, NMR, thermally stimulated depolarization current (TSDC), photon correlation spectroscopy (PCS), zeta potential, potentiometric titration, and Auger electron spectroscopy methods. Aggregation of primary particles and adsorption capacity (Vp) decrease and hysteresis loops of nitrogen adsorption-desorption isotherms becomes shorter with decreasing specific surface area (S(BET)). However, the shape of nitrogen adsorption-desorption isotherms can be assigned to the same type independent of S(BET) value. The main maximum of pore size distribution (gaps between primary nonporous particles in aggregates and agglomerates) shifts toward larger pore size and its intensity decreases with decreasing S(BET) value. The water adsorption increases with increasing S(BET) value; however, the opposite effect is observed for the content of surface hydroxyls (in mmol/m2). Associative desorption of water (2(SiOH)-->SiOSi+H2O) depends on both the morphology and synthesis conditions of fumed silica. The silica dissolution rate increases with increasing S(BET) and pH values. However, surface charge density and the modulus of zeta-potential increase with decreasing S(BET) value. The PCS, 1H NMR, and TSDC spectra demonstrate rearrangement of the fumed silica dispersion depending on the S(BET) value and the silica concentration (C(SiO2)) in the aqueous suspensions. A specific state of the dispersion is observed at the C(SiO2) values corresponding to the bulk density of the initial silica powder.

Journal of Colloid and Interface Science, 2006

The study of the adsorptions of cadmium and oxalate ions at the titania/electrolyte interface and... more The study of the adsorptions of cadmium and oxalate ions at the titania/electrolyte interface and the changes of the electrical double layer (edl) structure in this system are presented. The adsorption of cadmium or oxalate ions was calculated from an uptake of their concentration from the solution. The concentration of Cd(II) or oxalate ions in the solution was determined by radiotracer method. For labeling the solution 14C and 115Cd isotopes were used. Coadsorption of Cd(II) and oxalic ions was determined simultaneously. Besides, the main properties of the edl, i.e., surface charge density and zeta potential were determined by potentiometer titration and electrophoresis measurements, respectively. The adsorption of cadmium ions increases with pH increase and shifts with an increase of the initial concentration of Cd(II) ions towards higher pH values. The adsorption process causes an increase of negatively charged sites on anatase and a decrease of the zeta potential with an increase of initial concentration of these ions. The adsorption of oxalate anions at the titania/electrolyte interface proceeds through the exchange with hydroxyl groups. A decrease of pH produces an increase of adsorption of oxalate ions. The processes of anion adsorption lead to increase the number of the positively charged sites at the titania surface. However, specific adsorption of bidenate ligand as oxalate on one surface hydroxyl group may form inner sphere complexes on the metal oxide surface and may overcharge the compact part of the edl. The presence of oxalate ions in the system affects the adsorption of Cd(II) ions on TiO2, increasing the adsorption at low pH range and decreasing the adsorption at high pH range. Using adsorption as a function of pH data, some characteristic parameters of adsorption envelope were calculated.

Journal of Colloid and Interface Science, 2010

Adsorption of low-molecular adsorbates (nonpolar hexane, nitrogen, weakly polar acetonitrile, and... more Adsorption of low-molecular adsorbates (nonpolar hexane, nitrogen, weakly polar acetonitrile, and polar diethylamine, triethylamine, and water) onto individual (silica, alumina, titania), binary (silica/alumina (SA), silica/titania (ST)), and ternary (alumina/silica/titania, AST) fumed oxides was studied to analyse the effects of morphology and surface composition of the materials. Certain aspects of the interfacial phenomena dependent on the structural characteristics of oxides were analysed using calorimetry, (1)H NMR, and Raman spectroscopies, XRD, and ab initio quantum-chemical calculations. The specific surface area S(BET,X)-to-S(BET,N(2)) ratio (X is an organic adsorbate) changes from 0.68 for hexane adsorbed onto amorphous SA8 (degassed at 200 degrees C) to 1.85 for acetonitrile adsorbed onto crystalline alumina (degassed at 900 degrees C). These changes are relatively large because of variations in orientation, lateral interactions, and adsorption compressing of molecules adsorbed onto oxide surfaces. Larger S(BET,X)/S(BET,N(2)) values are observed for mixed oxides with higher crystallinity of titania or/and alumina phases in larger primary nanoparticles with greater surface roughness and hydrophilicity. Polar adsorbates can change the structure of aggregates of oxide nanoparticles that can, in turn, affect the results of adsorption measurements.

Journal of Colloid and Interface Science, 2007

Polymethylsiloxane (PMS) hydrogel (C(PMS)=10 wt%, soft paste-like hydrogel), diluted aqueous susp... more Polymethylsiloxane (PMS) hydrogel (C(PMS)=10 wt%, soft paste-like hydrogel), diluted aqueous suspensions, and dried/wetted xerogel (powder) were studied in comparison with suspensions and dry powders of unmodified and silylated nanosilicas and silica gels using (1)H NMR, thermally stimulated depolarization current (TSDC), quasielastic light scattering (QELS), rheometry, and adsorption methods. Nanosized primary PMS particles, which are softer and less dense than silica ones because of the presence of CH(3) groups attached to each Si atom and residual silanols, form soft secondary particles (soft paste-like hydrogel) that can be completely decomposed to nanoparticles with sizes smaller than 10 nm on sonication of the aqueous suspensions. Despite the soft character of the secondary particles, the aqueous suspensions of PMS are characterized by a higher viscosity (at concentration C(PMS)=3-5 wt%) than the suspension of fumed silica at a higher concentration. Three types of structured water are observed in dry PMS xerogel (adsorbed water of 3 wt%). These structures, characterized by the chemical shift of the proton resonance at delta(H) approximately 1.7,3.7, and 5 ppm, correspond to weakly associated but strongly bound water and to strongly associated but weakly or strongly bound waters, respectively. NMR cryoporometry and QELS results suggest that PMS is a mesoporous-macroporous material with the textural porosity caused by voids between primary particles forming aggregates and agglomerates of aggregates. PMS is characterized by a much smaller adsorption capacity with respect to proteins (gelatin, ovalbumin) than unmodified fumed silica A-300.

Journal of Colloid and Interface Science, 2002

Adsorption of Na + ions from water solutions on the surface of a porous silica layer covering the... more Adsorption of Na + ions from water solutions on the surface of a porous silica layer covering the optical fiber core was studied. It was shown that Na + ions adsorbed on silica obtained by the sol-gel method influence optical signal transmitted by optical fiber. The dependence of optical signal intensity on pH was observed. The results of optical measurements are in good agreement with those obtained by the potentiometric titration and adsorption of Na + cations with application of a radioactive isotope. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2003

The interaction of fumed silica A-300 (S(BET) = 297 m2 g(-1)) with bovine serum albumin (prepared... more The interaction of fumed silica A-300 (S(BET) = 297 m2 g(-1)) with bovine serum albumin (prepared by different methods), ovalbumin, human hemoglobin, and gelatin as a function of pH, salinity, and concentrations of components in aqueous medium was studied by adsorption and photon correlation spectroscopy (PCS) methods. Comparison of equilibrium (incubation time t(i) approximately 1 h) adsorption of proteins on A-300, minute (t(i) approximately 1 min) flocculation rate, and the particle size distributions measured by the PCS method shows different rearrangement of particle swarms depending on pH, salinity, and concentration of proteins, especially at pH close to IEP of silica or proteins. The electrokinetic mobility of protein/silica swarms is greater than that of individual components at pH far from the IEP of proteins. Changes in the Gibbs free energy (DeltaG) on protein adsorption depend on pH (-DeltaG is minimal at pH 2, close to the IEP of silica, and maximal at pH between the IEP of protein and silica), concentration (-DeltaG is maximal at C(p) between 1 and 6 mg/ml), type of proteins, and their preparation technique.

Electrochimica Acta, 2000

The growth of leuco-methylene blue (LMB) films and their electrodissolution have been studied by ... more The growth of leuco-methylene blue (LMB) films and their electrodissolution have been studied by voltammetry and piezogravimetry using bare gold (Au) and sulphur modified gold (Au-S) electrodes in methylene blue (MB + ) solutions. The growth rate anisotropy has been found for thin LMB films formed on Au-S modified electrodes and on bare Au electrodes. Excellent agreement has been found between the experimental equivalent molmass of thin LMB films deposited from fluoride solutions on Au, with general formula

Surface Chemistry in Biomedical and Environmental Science, 2006

ABSTRACT Different surface sites of silica, alumina, titania, and related mixed oxides, and pre-a... more ABSTRACT Different surface sites of silica, alumina, titania, and related mixed oxides, and pre-adsorbed poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG), affect the interaction with Ni(II), Cd(II), and Pb(II) studied using adsorption and potentiometric titration methods. Bridging hydroxyls (Brönsted acid sites) capable of taking part in ion-exchange reactions, and pre-adsorbed polymers, enhance the adsorption of metal ions at pH < 7. At pH > 7 PVA adsorbed on silica slightly enhances the adsorption of metal ions but pre- adsorbed PEG gives the opposite result. PEG has only electron-donor functionalities (C-O-C) which reduce the number of possible adsorption sites. PVA has COH groups with both electron-donor and proton-donor properties, which can effectively interact with metal ions and their hydroxy species.

Chromatographia, 2014

The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the... more The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, N-methylformamide and N,N-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase. During the study we found that there is no linear correlation between EOF velocity of the mobile phase and single variables such as zeta potential or dielectric constant or viscosity. However, there is quite strong linear correlation between EOF velocity of the mobile phase and variable obtained by multiplying zeta potential of the stationary phase-mobile phase interface, by dielectric cons...

Microporous and Mesoporous Materials, 2005

ABSTRACT A series of carbon/silica gel (CS) samples at different concentration of phosphorus comp... more ABSTRACT A series of carbon/silica gel (CS) samples at different concentration of phosphorus compounds (CP) was synthesized by carbonization of glucose in the presence of phosphoric acid on silica gel Si-100 in a rotary reactor in a nitrogen atmosphere at 500°C (5h) at a heating rate of 2 and 4°C/min (from 20 to 500°C). Prepared CS samples were studied using adsorption (nitrogen, Cd(II)), thermal analysis, titration, and spectroscopic (FTIR, XRF, XRD) methods in gaseous and liquid media. Contributions of nano-, meso-, and macropores to total porosity and specific surface area depend strongly on the CP value and the heating rate. An increase in the CP value enhances the negative surface charge density and the adsorption of Cd(II) characterized by a bi- or trimodal distribution function of Cd(II) binding constant f(Kn) over a broad Kn range.

Microporous and Mesoporous Materials, 2006

Two series of carbon/silica (carbosil, CS) adsorbents were prepared on the basis of silica gel as... more Two series of carbon/silica (carbosil, CS) adsorbents were prepared on the basis of silica gel as a matrix and glucose as a carbon precursor by pyrolysis of 0.01, 0.03, 0.05mol of glucose per 10g of mesoporous silica gel Si-100. Initial samples (CSn) were modified with hydrogen sulfide (CSn/S). On preparation of the CSn series, only nitrogen (100cm3/min) was used as a carrier gas. The CSn/S samples were prepared in the nitrogen (90cm3/min) and hydrogen sulfide (60cm3/min) atmosphere. Carbosils were studied using adsorption (nitrogen, butane, ammonia, and Ni(II)) and thermal analysis methods. During glucose pyrolysis in the hydrogen sulfide atmosphere the chemical reactions between glucose and hydrogen sulfide take place that leads to a greater yield of carbon deposits. The presence of sulfur on the carbosil surface has a negative effect on butane adsorption and the opposite effect is observed on the adsorption of ammonium and Ni(II).

Langmuir, 2002

ABSTRACT Pristine fumed silica and powders with dried residuals of centrifuged aqueous suspension... more ABSTRACT Pristine fumed silica and powders with dried residuals of centrifuged aqueous suspensions of fumed silica, silica/PVP, or silica/protein were studied using nitrogen adsorption and IR spectroscopy methods. The aqueous suspensions of silica with added polymers, surfactant, or ethanol were investigated by means of photon correlation spectroscopy, 1H NMR, and adsorption methods. The impact of polymers on the suspension and dried powder characteristics depends on the adsorption mechanism and the conformation of polymer molecules (globular or unfolded) due to strong or weak intramolecular interactions. Globular proteins interacting with silica through the flocculation mechanism affect the textural characteristics of dried powders more weakly than do unfolded proteins but strongly impact the aqueous suspension, thus shifting the swarm size distribution toward larger sizes compared to the size distribution of poly(vinylpyrrolidone), PVP. PVP is adsorbed in the unfolded state and gives a nearly monomodal particle size distribution (PSD). The ionogenic surfactant 1,2-ethylene-bis(N-dimethyl carbodecyloxymethyl)ammonium dichloride at CAet < 0.01 wt % and ethanol at CEtOH = 10−50 wt % impacts the silica's PSD-dependent nonlinearly on the concentrations and pH.

Journal of Thermal Analysis and Calorimetry, 2011

Mechanochemical activation of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide syst... more Mechanochemical activation of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide system in various media (air, water, and ethanol) has been studied. Powder X-ray diffraction, nitrogen adsorptiondesorption, thermogravimetric and chemical analysis, FTIR and Raman spectroscopy, and scanning electron microscopy have been used for research of prepared milled samples. The electrokinetic properties (dependence zeta potential-pH, position of isoelectric point) of individual V 2 O 5 , MoO 3 and mixed vanadium-molybdenum oxide system, synthesized via mechanochemical treatment in various medium, in aqueous solutions of electrolytes also have been determined. Initial, milled, and spent samples are characterized with the help of XRD, FTIR and Raman spectroscopy, and SEM and adsorption of nitrogen. The catalytic properties of vanadium-molybdenum oxide composition activated in different media have been investigated in reaction of oxidation dehydrogenation of propane.

Journal of Radioanalytical and Nuclear Chemistry Articles, 1988

The surface charge and adsorption densities of Na+ and Cl– ions at the zirconium dioxide/electrol... more The surface charge and adsorption densities of Na+ and Cl– ions at the zirconium dioxide/electrolyte interface have been determined as a function of pH for 0.1, 0.01 and 0.001 M solutions of NaCl. Using potentiometric titration of the surface hydroxy groups, it was found that the point of zero charge occurred at pH 4.3±0.15. The results are discussed in terms

Journal of Materials Science, 1991

... 115 (1987) 555. 11. AL DAWIDOWlCZ, J. MATUSEWlCZ and J. WYSOCKA-LISEK, Talanta, 36 (1989) 586... more ... 115 (1987) 555. 11. AL DAWIDOWlCZ, J. MATUSEWlCZ and J. WYSOCKA-LISEK, Talanta, 36 (1989) 586 12. JA DAVIS, RO JAMES and JO LECKIE, J. Colloid Interface Sci. 63 (1978) 480. Received 2 February and accepted 30 November 1990 4868

Journal of Colloid and Interface Science, 2000

Journal of Colloid and Interface Science, 2006

Successive interaction of different pairs of water-soluble polymers (poly(ethylene glycol) (PEG),... more Successive interaction of different pairs of water-soluble polymers (poly(ethylene glycol) (PEG), poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA)), proteins (bovine serum albumin (BSA), ovalbumin, gelatin, and ossein), and smaller organics such as lecithin (1-stearoyl-2oleoyl phosphatidylcholine, SOPC) and Aethonium (1,2-ethylene-bis(N-dimethyl carbodecyl oxymethyl) ammonium dichloride) with nanosilicas A-300 (S BET = 232 and 297 m 2 g −1 ) and A-50 (S BET = 52 m 2 g −1 ) was studied using dynamic light scattering, adsorption, and infrared (FTIR) spectroscopy methods. Time-dependent rearrangement of particle size distributions (PSDs) depicts appearance of both smaller and larger aggregates for silica/PEG(I-first adsorbate)/BSA(II-second adsorbate) and silica/PVP(I)/BSA(II) (i.e., BSA adsorbs onto PEG/silica or PVP/silica) than that for silica/organic compound I. However, in the cases of PVA(I)-BSA(II) and PVA(I)-SOPC(II) a similar effect is not observed because only increased aggregation occurs. The successive equilibrium adsorption of similar pairs shows a diminution of the adsorption of the second compound (gelatin, ovalbumin) with increasing amount of the first adsorbed polymer (PEG or PVP). (V.M. Gun'ko). induced conformational changes, chemical and morphological characteristics of solids, and characteristics of the media (pH, salinity, concentrations of polymers and solid particles, and temperature) . The interfacial phenomena are more complex for mixtures of adsorbates, especially macromolecules, with strongly different spatial and chemical structures. Results of their competitive adsorption depend on their mobility and affinity to a surface as well as on the mentioned factors and applied external electrical or mechanical forces governing the interfacial layer structure with time. Smaller molecules, adsorbing faster (because of limitation of this process by the diffusion rate) than larger but slower ones, can be displaced by the latter if pores of solid particles are much larger than molecules. This phenomenon, known as the Vroman effect, related to the adsorption of proteins and discovered for fibrinogen competing with other plasma proteins [1], has been observed for blends of various proteins . The Vroman effect has substantial significance for the biocompatibility of biomaterials because it 0021-9797/$ -see front matter

Journal of Colloid and Interface Science, 1997

charge through the acid-base reactions of surface hydroxyl Adsorption of the monovalent cations C... more charge through the acid-base reactions of surface hydroxyl Adsorption of the monovalent cations Cs / and Na / from mixed groups, solutions of NaCl and CsCl at the TiO 2 (anatase)/water interface was studied. Higher adsorption of Cs / than Na / was observed from solutions of similar electrolyte concentration. The surface

Journal of Colloid and Interface Science, 2011

The structural, textural, and adsorption characteristics of mechanochemically activated (MCA) fum... more The structural, textural, and adsorption characteristics of mechanochemically activated (MCA) fumed silica A-300 as dry or water, ethanol, or water/ethanol-wetted powders (0.5 g of a solvent per gram of silica) in a ball mill for 1-6 h were studied in comparison with those of the initial powder. The MCA treatment enhances bulk density (ρ(b)) of the powder (from 0.045 g/cm(3) for the initial silica to 0.4 g/cm(3) for 6 h-MCA-treated water-wetted silica) depending on medium type and MCA time (t(MCA)). Stronger effects are observed for the MCA treatment of water-wetted silica than of dry or ethanol- or water/ethanol-wetted samples. The MCA treatment weakly affects the specific surface area (S(BET)). However, void (pore) size distribution, porosity, particle aggregation and size distribution in aqueous suspension, behavior of interfacial water, properties of poly(vinyl alcohol)/silica composites and adsorption of gelatin depend more strongly on the t(MCA) and ρ(b) values. Some of the observed changes in the characteristics (e.g., gelatin adsorption) depend on the ρ(b) value but are independent of the medium type used on the MCA. Other characteristics are nonlinear functions of both t(MCA) and ρ(b) values.

Journal of Colloid and Interface Science, 2002

Cab-O-Sil HS-5 grafted with 3aminopropyldimethylsilyl (APDMS), butyldimethylsilyl (BDMS), octadec... more Cab-O-Sil HS-5 grafted with 3aminopropyldimethylsilyl (APDMS), butyldimethylsilyl (BDMS), octadecyldimethylsilyl (ODDMS), and trimethylsilyl (TMS) groups of different concentrations were studied using photon correlation spectroscopy, electrophoresis, potentiometric titration, and nitrogen adsorption methods. Calculations of both electrophoretic mobility and ζ potential were performed taking into consideration the topological structure of "porous" aggregates of primary particles of fumed silica using two different approaches. Changes in surface charge density and the textural, aggregative, and electrophoretic characteristics of modified silicas depend on the type of grafted OSC, its chain length, polarity, and surface concentration. Particle swarms of initial and modified silicas in aqueous suspension are typically characterized by bimodal size distributions between 20 and 300 nm (aggregates) and 1-3 µm (agglomerates of aggregates). The difference between parameter values computed according to the Smoluchowski theory and improved approaches increases with increasing pH and is concordant for both mobility and ζ potential. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2005

Several series of fumed silicas and mixed fumed oxides produced and treated under different condi... more Several series of fumed silicas and mixed fumed oxides produced and treated under different conditions were studied in gaseous and liquid media using nitrogen and water adsorption-desorption, mass spectrometry, FTIR, NMR, thermally stimulated depolarization current (TSDC), photon correlation spectroscopy (PCS), zeta potential, potentiometric titration, and Auger electron spectroscopy methods. Aggregation of primary particles and adsorption capacity (Vp) decrease and hysteresis loops of nitrogen adsorption-desorption isotherms becomes shorter with decreasing specific surface area (S(BET)). However, the shape of nitrogen adsorption-desorption isotherms can be assigned to the same type independent of S(BET) value. The main maximum of pore size distribution (gaps between primary nonporous particles in aggregates and agglomerates) shifts toward larger pore size and its intensity decreases with decreasing S(BET) value. The water adsorption increases with increasing S(BET) value; however, the opposite effect is observed for the content of surface hydroxyls (in mmol/m2). Associative desorption of water (2(SiOH)-->SiOSi+H2O) depends on both the morphology and synthesis conditions of fumed silica. The silica dissolution rate increases with increasing S(BET) and pH values. However, surface charge density and the modulus of zeta-potential increase with decreasing S(BET) value. The PCS, 1H NMR, and TSDC spectra demonstrate rearrangement of the fumed silica dispersion depending on the S(BET) value and the silica concentration (C(SiO2)) in the aqueous suspensions. A specific state of the dispersion is observed at the C(SiO2) values corresponding to the bulk density of the initial silica powder.

Journal of Colloid and Interface Science, 2006

The study of the adsorptions of cadmium and oxalate ions at the titania/electrolyte interface and... more The study of the adsorptions of cadmium and oxalate ions at the titania/electrolyte interface and the changes of the electrical double layer (edl) structure in this system are presented. The adsorption of cadmium or oxalate ions was calculated from an uptake of their concentration from the solution. The concentration of Cd(II) or oxalate ions in the solution was determined by radiotracer method. For labeling the solution 14C and 115Cd isotopes were used. Coadsorption of Cd(II) and oxalic ions was determined simultaneously. Besides, the main properties of the edl, i.e., surface charge density and zeta potential were determined by potentiometer titration and electrophoresis measurements, respectively. The adsorption of cadmium ions increases with pH increase and shifts with an increase of the initial concentration of Cd(II) ions towards higher pH values. The adsorption process causes an increase of negatively charged sites on anatase and a decrease of the zeta potential with an increase of initial concentration of these ions. The adsorption of oxalate anions at the titania/electrolyte interface proceeds through the exchange with hydroxyl groups. A decrease of pH produces an increase of adsorption of oxalate ions. The processes of anion adsorption lead to increase the number of the positively charged sites at the titania surface. However, specific adsorption of bidenate ligand as oxalate on one surface hydroxyl group may form inner sphere complexes on the metal oxide surface and may overcharge the compact part of the edl. The presence of oxalate ions in the system affects the adsorption of Cd(II) ions on TiO2, increasing the adsorption at low pH range and decreasing the adsorption at high pH range. Using adsorption as a function of pH data, some characteristic parameters of adsorption envelope were calculated.

Journal of Colloid and Interface Science, 2010

Adsorption of low-molecular adsorbates (nonpolar hexane, nitrogen, weakly polar acetonitrile, and... more Adsorption of low-molecular adsorbates (nonpolar hexane, nitrogen, weakly polar acetonitrile, and polar diethylamine, triethylamine, and water) onto individual (silica, alumina, titania), binary (silica/alumina (SA), silica/titania (ST)), and ternary (alumina/silica/titania, AST) fumed oxides was studied to analyse the effects of morphology and surface composition of the materials. Certain aspects of the interfacial phenomena dependent on the structural characteristics of oxides were analysed using calorimetry, (1)H NMR, and Raman spectroscopies, XRD, and ab initio quantum-chemical calculations. The specific surface area S(BET,X)-to-S(BET,N(2)) ratio (X is an organic adsorbate) changes from 0.68 for hexane adsorbed onto amorphous SA8 (degassed at 200 degrees C) to 1.85 for acetonitrile adsorbed onto crystalline alumina (degassed at 900 degrees C). These changes are relatively large because of variations in orientation, lateral interactions, and adsorption compressing of molecules adsorbed onto oxide surfaces. Larger S(BET,X)/S(BET,N(2)) values are observed for mixed oxides with higher crystallinity of titania or/and alumina phases in larger primary nanoparticles with greater surface roughness and hydrophilicity. Polar adsorbates can change the structure of aggregates of oxide nanoparticles that can, in turn, affect the results of adsorption measurements.

Journal of Colloid and Interface Science, 2007

Polymethylsiloxane (PMS) hydrogel (C(PMS)=10 wt%, soft paste-like hydrogel), diluted aqueous susp... more Polymethylsiloxane (PMS) hydrogel (C(PMS)=10 wt%, soft paste-like hydrogel), diluted aqueous suspensions, and dried/wetted xerogel (powder) were studied in comparison with suspensions and dry powders of unmodified and silylated nanosilicas and silica gels using (1)H NMR, thermally stimulated depolarization current (TSDC), quasielastic light scattering (QELS), rheometry, and adsorption methods. Nanosized primary PMS particles, which are softer and less dense than silica ones because of the presence of CH(3) groups attached to each Si atom and residual silanols, form soft secondary particles (soft paste-like hydrogel) that can be completely decomposed to nanoparticles with sizes smaller than 10 nm on sonication of the aqueous suspensions. Despite the soft character of the secondary particles, the aqueous suspensions of PMS are characterized by a higher viscosity (at concentration C(PMS)=3-5 wt%) than the suspension of fumed silica at a higher concentration. Three types of structured water are observed in dry PMS xerogel (adsorbed water of 3 wt%). These structures, characterized by the chemical shift of the proton resonance at delta(H) approximately 1.7,3.7, and 5 ppm, correspond to weakly associated but strongly bound water and to strongly associated but weakly or strongly bound waters, respectively. NMR cryoporometry and QELS results suggest that PMS is a mesoporous-macroporous material with the textural porosity caused by voids between primary particles forming aggregates and agglomerates of aggregates. PMS is characterized by a much smaller adsorption capacity with respect to proteins (gelatin, ovalbumin) than unmodified fumed silica A-300.

Journal of Colloid and Interface Science, 2002

Adsorption of Na + ions from water solutions on the surface of a porous silica layer covering the... more Adsorption of Na + ions from water solutions on the surface of a porous silica layer covering the optical fiber core was studied. It was shown that Na + ions adsorbed on silica obtained by the sol-gel method influence optical signal transmitted by optical fiber. The dependence of optical signal intensity on pH was observed. The results of optical measurements are in good agreement with those obtained by the potentiometric titration and adsorption of Na + cations with application of a radioactive isotope. C 2002 Elsevier Science (USA)

Journal of Colloid and Interface Science, 2003

The interaction of fumed silica A-300 (S(BET) = 297 m2 g(-1)) with bovine serum albumin (prepared... more The interaction of fumed silica A-300 (S(BET) = 297 m2 g(-1)) with bovine serum albumin (prepared by different methods), ovalbumin, human hemoglobin, and gelatin as a function of pH, salinity, and concentrations of components in aqueous medium was studied by adsorption and photon correlation spectroscopy (PCS) methods. Comparison of equilibrium (incubation time t(i) approximately 1 h) adsorption of proteins on A-300, minute (t(i) approximately 1 min) flocculation rate, and the particle size distributions measured by the PCS method shows different rearrangement of particle swarms depending on pH, salinity, and concentration of proteins, especially at pH close to IEP of silica or proteins. The electrokinetic mobility of protein/silica swarms is greater than that of individual components at pH far from the IEP of proteins. Changes in the Gibbs free energy (DeltaG) on protein adsorption depend on pH (-DeltaG is minimal at pH 2, close to the IEP of silica, and maximal at pH between the IEP of protein and silica), concentration (-DeltaG is maximal at C(p) between 1 and 6 mg/ml), type of proteins, and their preparation technique.