NATO Science for Peace and Security Series B: Physics and Biophysics, 2018
This study is concerned with the preparation and characterization of electrocatalysts containing ... more This study is concerned with the preparation and characterization of electrocatalysts containing Magneli phases as a support material, and different metallic systems (Co, Pt, and CoPt, Co:Pt = 1:1 wt.), as catalytic phase. The main idea was to reduce the amount of Pt with the addition of Co as a non-noble metal. The studied electrocatalysts were tested for water electrolysis in aqueous electrolytes, i.e. for hydrogen evolution reactions (HER) and for oxygen evolution reactions (OER). They were also tested in PEM fuel cells for oxygen reduction reaction (ORR). The order of activity for HER and OER was the following: CoPt > Pt > Co, and for ORR: CoPt ≈ Pt > Co. Co has been shown as promoter for reducing Pt particles (the most active monometallic phase), so the reduction of the Pt quantity in the metallic phase was compensated by smaller particles. Also, the interaction between the metallic phases increases the intrinsic catalytic activity for all reactions (HER, OER and ORR).
NATO Science for Peace and Security Series B: Physics and Biophysics, 2020
The aim of this study is to analyze the sensor activity of polyaniline (PANI) based nanocomposite... more The aim of this study is to analyze the sensor activity of polyaniline (PANI) based nanocomposites reinforced with carbon nanostructures (CNSs) such as graphene (G) and multi walled carbon nanotubes (MWCNT), in order to use them as pH sensors. For their realization the nanocomposites are applied on screen printed electrode (SPE) by means of steady state electrochemical polarization. The optimal conditions for electropolymerization of the PANI/CNSs on gold SPE were defined by steady state polarization measurements. It was found that the optimal potential for electropolymerization of the PANI based nanocomposites on gold SPE is 1.15 V vs. saturated calomel electrode (SCE). The prepared nanosensors are characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The stability of the nanosensors was tested in synthetic sea water with pH = 8.4 and the most stabile was 3% MWCNT reinforced PANI nanocomposite at average of 12 min time, with minimal deviations for a period of more than 30 days. The results show also that decreasing the temperature leads to lower resistivity, which is attributed to reduced diffusion in the process of doping and dedoping. On the other side this reflects in the increased stabilization time of the nanosensor. Tests were conducted by two probe method to study the sensor activity of the nanocomposites against pH changes. The pH changes varied from 8.49 to 7.96 and represent simulation of the changes happening in real sea water. It was found that with changing the pH of the water, time of 1 min was needed for stabilization of the sensor resistivity. The resistivity changes versus pH changes show linear dependence by increasing the resistivity of the nanosensor with decreasing the pH of the water.
In the last few years, application of selenium has increased significantly due to its unique poss... more In the last few years, application of selenium has increased significantly due to its unique possibilities to acts as an antioxidant and as an anticancer reagent in human body. Due to this, selenium is one of the most important chemical elements for human health. Recently, selenium usage in microelectronics was significantly increased as semiconductors with characteristic electronic properties. The selenium is the least abundant element in earth crust, but as the application fields of selenium are widely opened, the needs of this element are larger. This opens new views in the field of improving existing and developing new technologies for extraction of selenium. In this work, a new technology for extraction of selenium from natural resources was developed, by combining the advantages and removing the disadvantages and weaknesses of the existing technologies. The sediments near mineral water springs and used water filters with content from 0.0656 to 0.9291 % wt. of Se were used as m...
Material Science & Engineering International Journal
The subject of this research work was to analyze the structural and morphological changes of TiO2... more The subject of this research work was to analyze the structural and morphological changes of TiO2 as a result of incorporation of CNTs and interpret the underlying principles for the observed interactions. Hybrid TiO2/CNTs nanostructures were prepared by simplified sol-gel method followed by monitoring the thermally-induced alterations occurring up to 400 ºC. The effects of different type of CNTs (activated MWCNTs and as prepared SWCNTs) as well as the variation of the content of MWCNTs in association with the metal-dopant (Pt or Co) influencing the structural parameters of TiO2 was monitored. Addition of CNTs and metallic phase causes reduction of TiO2 (anatase) crystallite size. The applied instrumental techniques such as XRPD, Raman spectroscopy and thermal (TG, DTA and DTG) analysis points out on achieved interaction between TiO2 and incorporated CNTs. Morphological changes, observed from the SEM micrographs, revealed better inter-locking of the TiO2 matrix with SWCNTs than with...
This article presents production and characterizations of MWCNTs produced by non-stationary curre... more This article presents production and characterizations of MWCNTs produced by non-stationary current regimes into lithium molten chloride. In order to improve the process of MWCNTs production, instead of applying a constant cathode potential, the method of reversing the potential was applied. It should be mentioned that during the process of electrolysis reduced lithium intercalate at graphite surface and generates a high mechanical stress that causes exfoliation of the graphite cathode. This phenomenon enables electrochemical synthesis of MWCNTs to be possible. The measurements were performed in temperature interval from 700 to 800°C. Several techniques were employed for characterization, i.e. electron microscopy (SEM and TEM), Raman spectroscopy, thermo gravimetric and differential thermal analysis (TGA and DTA). SEM and TEM images show that nanotubes are mostly of curved shape with length of 1÷20 μm and diameter of 20÷40 nm. Raman peaks indicate that the crystal lenity of produced nanotubes is rather low. The obtained results suggest that formed product contains of up to 80% MWCNTs, the rest being non-reacted graphite and fullerenes. DTA curves show that combustion process of the nanotubes takes place in two stages, i.e. at 450°C and 720°C. At the lower temperature combustion of MWCNTs occurs, while at higher one fullerenes and non-reacted graphite particles burn.
Abstract In the current study, graphene, synthesized in the laboratory for nanomaterials of the F... more Abstract In the current study, graphene, synthesized in the laboratory for nanomaterials of the Faculty of Technology and Metallurgy in Skopje, marked as G-ASP2, was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis (TGA). The acid activation of the G-ASP2 was performed using concentrated H2SO4 and HNO3. The aim of this work was to investigate the adsorption ability of graphene, G-ASP2, and its activated form AG-ASP2, in the removal of Ni(II), Pb(II), and Fe(II) ions from aqueous solutions. The influence of the adsorption time on the efficiency of heavy metal ion removal was studied, and thus the analysis of the process kinetics was carried out. The study found that for all examined systems, the adsorption process followed the pseudo second-order kinetic model. The comparison of the removal percentage of metal ions in the single and multimetal systems was also performed. Therefore, graphene and activated graphene are promising adsorbents for Ni(II), Pb(II), and Fe(II) removal from polluted water.
The rapid industrial development and urbanization have intensified environmental pollution and ca... more The rapid industrial development and urbanization have intensified environmental pollution and caused deterioration of ecosystems by accumulation of many pollutants, especially heavy metals. Most of the heavy metals are toxic, and their ions are not biodegradable with the tendency to accumulate in the soil, water resources and the living organisms; hence, they are significant environmental pollutants. Therefore, the treatment of the heavy metal ions and their elimination from water and wastewater is very important for environmental protection and thus the public health. In the frame of this work, the adsorption abilities of natural and nanosorbents, particularly natural peanut husks, expanded perlite and graphene, to remove Ni(II), Pb(II), and Fe(II) ions from water systems, were investigated. The influence of the pH (4–8) of the solution, the amount of adsorbent (0.5–5.5 g/l), the initial metal ion concentration (0.3–2.0 mg/l), and the contact time (5–180 min.) on the efficiency of removal of metal ions was investigated. Thus, the optimal conditions for achieving maximal effectiveness for heavy metals removal were determined. The characterization of the sorbents was performed utilizing the following techniques: SEM and TGA. Adsorption equilibrium of the systems was analyzed using the following isotherms: Langmuir, Freundlich, Langmuir–Freundlich, and Redlich–Peterson. The maximal adsorption capacity of the peanut husks, perlite and graphene for Ni(II), Fe(II), Pb(II) was obtained, and the percentage of removal was determined. A comparative analysis for the efficiency of all used sorbents for Ni(II), Pb(II), and Fe(II) ions removal from the three component systems was conducted at the end. The expanded perlite gave the best results for the removal of Ni (II) and Pb (II) ions, while graphene proved to be excellent adsorbent for Fe(II) ions with an efficiency of 100%.
Polymer nanocomposites of conductive polymer, polyaniline (PANI) with multi-walled carbon nanotub... more Polymer nanocomposites of conductive polymer, polyaniline (PANI) with multi-walled carbon nanotubes (MWCNTs), have gained a great interest for their application in environmental and water quality monitoring (where pH value becomes one of the reliable data). Compared to the inorganic counterparts, conducting polymers have advantage in achieving high sensitivity and selectivity by virtue of their chemical and structural diversity. In the framework of FP7 project COMMON SENSE (OCEAN 2013.2-614155), screen-printed electrodes as a pH nanosensors based on nanocomposites of conductive polymer matrix-PANI and MWCNT were prepared by electrochemical polymerization. Characterization was performed by several spectroscopic techniques and electrical measurements. Electrochemical synthesis of the PANI-based composites was performed at 0.75 V vs. saturated calomel electrode (SCE) for 40 and 60 minutes. The working conditions were determined using electrochemical steady-state polarization measurements. Morphology of the produced composites was observed using scanning electron microscope (SEM), structural characteristics were studied using Raman spectroscopy, while thermal stability was determined using thermal gravimetric analysis (TGA/DTA). The results point out on fibrous and porous structure of PANI-based composites, with strong interaction between quinoidal structure of PANI with carbon nanostructures via p–p stacking according to Raman spectroscopy measurements. TGA coupled with DTA showed the increased thermal stability of the studied composites. The obtained nanocomposites exhibited a high value of conductivity which attributed to the synergy effect of the conductive polymer matrix and carbon nanostructure. Resistivity (i.e., conductivity) changes were measured at different pHs (4 to 10) as well as in different marine regions.
Material Science & Engineering International Journal
The processes of generation, management, treatment and disposal of fly ash industrial waste parti... more The processes of generation, management, treatment and disposal of fly ash industrial waste particles, all over the world, were considered as serious issues of solid waste. The subject of this research work was to create and to characterize the Fly ash/Chitosan composites aimed for heavy metal adsorption in polluted waters. Three different types of fly ash waste particles were used, two types supplied from EURONICKEL and one supplied from OSLOMEJ, Macedonia. The surface of the fly ash (FA) particles was modified by treated with nitric acid (HNO3). Several types of composite adsorbents were prepared using the chitosan as a polymer matrix. The characterization of the metallurgical waste particles was performed by XRF, XRD, TGA, SEM and FTIR analysis, while the obtained composites were tested by TGA, SEM and FTIR analysis. It was observed that the structure, morphology, and some other characteristics of FA particles have been significantly changed after treatment with chitosan and it i...
Material Science & Engineering International Journal
The literature review of the developments of nanomaterials, application methods, their anti-viral... more The literature review of the developments of nanomaterials, application methods, their anti-viral activity confirmed the importance and highlighted the contribution of nanostructures in fighting the corona virus. In order to improve and enhanced the protection function of the facemasks against different viruses, especially last one SARS-CoV-2 (Covid 19), various nanostructures were used, fabricated and modified for that purpose. Among the others, special attention was given on carbon based (carbon nanotubes and graphene) and nano silver, TiO2, iron and cooper with antiviral and antibacterial effects. In this paper, an overview will be presented on several nanostructures used in the facemasks for preventing the spread and protection of Covid 19.
NATO Science for Peace and Security Series B: Physics and Biophysics, 2018
This study is concerned with the preparation and characterization of electrocatalysts containing ... more This study is concerned with the preparation and characterization of electrocatalysts containing Magneli phases as a support material, and different metallic systems (Co, Pt, and CoPt, Co:Pt = 1:1 wt.), as catalytic phase. The main idea was to reduce the amount of Pt with the addition of Co as a non-noble metal. The studied electrocatalysts were tested for water electrolysis in aqueous electrolytes, i.e. for hydrogen evolution reactions (HER) and for oxygen evolution reactions (OER). They were also tested in PEM fuel cells for oxygen reduction reaction (ORR). The order of activity for HER and OER was the following: CoPt > Pt > Co, and for ORR: CoPt ≈ Pt > Co. Co has been shown as promoter for reducing Pt particles (the most active monometallic phase), so the reduction of the Pt quantity in the metallic phase was compensated by smaller particles. Also, the interaction between the metallic phases increases the intrinsic catalytic activity for all reactions (HER, OER and ORR).
NATO Science for Peace and Security Series B: Physics and Biophysics, 2020
The aim of this study is to analyze the sensor activity of polyaniline (PANI) based nanocomposite... more The aim of this study is to analyze the sensor activity of polyaniline (PANI) based nanocomposites reinforced with carbon nanostructures (CNSs) such as graphene (G) and multi walled carbon nanotubes (MWCNT), in order to use them as pH sensors. For their realization the nanocomposites are applied on screen printed electrode (SPE) by means of steady state electrochemical polarization. The optimal conditions for electropolymerization of the PANI/CNSs on gold SPE were defined by steady state polarization measurements. It was found that the optimal potential for electropolymerization of the PANI based nanocomposites on gold SPE is 1.15 V vs. saturated calomel electrode (SCE). The prepared nanosensors are characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The stability of the nanosensors was tested in synthetic sea water with pH = 8.4 and the most stabile was 3% MWCNT reinforced PANI nanocomposite at average of 12 min time, with minimal deviations for a period of more than 30 days. The results show also that decreasing the temperature leads to lower resistivity, which is attributed to reduced diffusion in the process of doping and dedoping. On the other side this reflects in the increased stabilization time of the nanosensor. Tests were conducted by two probe method to study the sensor activity of the nanocomposites against pH changes. The pH changes varied from 8.49 to 7.96 and represent simulation of the changes happening in real sea water. It was found that with changing the pH of the water, time of 1 min was needed for stabilization of the sensor resistivity. The resistivity changes versus pH changes show linear dependence by increasing the resistivity of the nanosensor with decreasing the pH of the water.
In the last few years, application of selenium has increased significantly due to its unique poss... more In the last few years, application of selenium has increased significantly due to its unique possibilities to acts as an antioxidant and as an anticancer reagent in human body. Due to this, selenium is one of the most important chemical elements for human health. Recently, selenium usage in microelectronics was significantly increased as semiconductors with characteristic electronic properties. The selenium is the least abundant element in earth crust, but as the application fields of selenium are widely opened, the needs of this element are larger. This opens new views in the field of improving existing and developing new technologies for extraction of selenium. In this work, a new technology for extraction of selenium from natural resources was developed, by combining the advantages and removing the disadvantages and weaknesses of the existing technologies. The sediments near mineral water springs and used water filters with content from 0.0656 to 0.9291 % wt. of Se were used as m...
Material Science & Engineering International Journal
The subject of this research work was to analyze the structural and morphological changes of TiO2... more The subject of this research work was to analyze the structural and morphological changes of TiO2 as a result of incorporation of CNTs and interpret the underlying principles for the observed interactions. Hybrid TiO2/CNTs nanostructures were prepared by simplified sol-gel method followed by monitoring the thermally-induced alterations occurring up to 400 ºC. The effects of different type of CNTs (activated MWCNTs and as prepared SWCNTs) as well as the variation of the content of MWCNTs in association with the metal-dopant (Pt or Co) influencing the structural parameters of TiO2 was monitored. Addition of CNTs and metallic phase causes reduction of TiO2 (anatase) crystallite size. The applied instrumental techniques such as XRPD, Raman spectroscopy and thermal (TG, DTA and DTG) analysis points out on achieved interaction between TiO2 and incorporated CNTs. Morphological changes, observed from the SEM micrographs, revealed better inter-locking of the TiO2 matrix with SWCNTs than with...
This article presents production and characterizations of MWCNTs produced by non-stationary curre... more This article presents production and characterizations of MWCNTs produced by non-stationary current regimes into lithium molten chloride. In order to improve the process of MWCNTs production, instead of applying a constant cathode potential, the method of reversing the potential was applied. It should be mentioned that during the process of electrolysis reduced lithium intercalate at graphite surface and generates a high mechanical stress that causes exfoliation of the graphite cathode. This phenomenon enables electrochemical synthesis of MWCNTs to be possible. The measurements were performed in temperature interval from 700 to 800°C. Several techniques were employed for characterization, i.e. electron microscopy (SEM and TEM), Raman spectroscopy, thermo gravimetric and differential thermal analysis (TGA and DTA). SEM and TEM images show that nanotubes are mostly of curved shape with length of 1÷20 μm and diameter of 20÷40 nm. Raman peaks indicate that the crystal lenity of produced nanotubes is rather low. The obtained results suggest that formed product contains of up to 80% MWCNTs, the rest being non-reacted graphite and fullerenes. DTA curves show that combustion process of the nanotubes takes place in two stages, i.e. at 450°C and 720°C. At the lower temperature combustion of MWCNTs occurs, while at higher one fullerenes and non-reacted graphite particles burn.
Abstract In the current study, graphene, synthesized in the laboratory for nanomaterials of the F... more Abstract In the current study, graphene, synthesized in the laboratory for nanomaterials of the Faculty of Technology and Metallurgy in Skopje, marked as G-ASP2, was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis (TGA). The acid activation of the G-ASP2 was performed using concentrated H2SO4 and HNO3. The aim of this work was to investigate the adsorption ability of graphene, G-ASP2, and its activated form AG-ASP2, in the removal of Ni(II), Pb(II), and Fe(II) ions from aqueous solutions. The influence of the adsorption time on the efficiency of heavy metal ion removal was studied, and thus the analysis of the process kinetics was carried out. The study found that for all examined systems, the adsorption process followed the pseudo second-order kinetic model. The comparison of the removal percentage of metal ions in the single and multimetal systems was also performed. Therefore, graphene and activated graphene are promising adsorbents for Ni(II), Pb(II), and Fe(II) removal from polluted water.
The rapid industrial development and urbanization have intensified environmental pollution and ca... more The rapid industrial development and urbanization have intensified environmental pollution and caused deterioration of ecosystems by accumulation of many pollutants, especially heavy metals. Most of the heavy metals are toxic, and their ions are not biodegradable with the tendency to accumulate in the soil, water resources and the living organisms; hence, they are significant environmental pollutants. Therefore, the treatment of the heavy metal ions and their elimination from water and wastewater is very important for environmental protection and thus the public health. In the frame of this work, the adsorption abilities of natural and nanosorbents, particularly natural peanut husks, expanded perlite and graphene, to remove Ni(II), Pb(II), and Fe(II) ions from water systems, were investigated. The influence of the pH (4–8) of the solution, the amount of adsorbent (0.5–5.5 g/l), the initial metal ion concentration (0.3–2.0 mg/l), and the contact time (5–180 min.) on the efficiency of removal of metal ions was investigated. Thus, the optimal conditions for achieving maximal effectiveness for heavy metals removal were determined. The characterization of the sorbents was performed utilizing the following techniques: SEM and TGA. Adsorption equilibrium of the systems was analyzed using the following isotherms: Langmuir, Freundlich, Langmuir–Freundlich, and Redlich–Peterson. The maximal adsorption capacity of the peanut husks, perlite and graphene for Ni(II), Fe(II), Pb(II) was obtained, and the percentage of removal was determined. A comparative analysis for the efficiency of all used sorbents for Ni(II), Pb(II), and Fe(II) ions removal from the three component systems was conducted at the end. The expanded perlite gave the best results for the removal of Ni (II) and Pb (II) ions, while graphene proved to be excellent adsorbent for Fe(II) ions with an efficiency of 100%.
Polymer nanocomposites of conductive polymer, polyaniline (PANI) with multi-walled carbon nanotub... more Polymer nanocomposites of conductive polymer, polyaniline (PANI) with multi-walled carbon nanotubes (MWCNTs), have gained a great interest for their application in environmental and water quality monitoring (where pH value becomes one of the reliable data). Compared to the inorganic counterparts, conducting polymers have advantage in achieving high sensitivity and selectivity by virtue of their chemical and structural diversity. In the framework of FP7 project COMMON SENSE (OCEAN 2013.2-614155), screen-printed electrodes as a pH nanosensors based on nanocomposites of conductive polymer matrix-PANI and MWCNT were prepared by electrochemical polymerization. Characterization was performed by several spectroscopic techniques and electrical measurements. Electrochemical synthesis of the PANI-based composites was performed at 0.75 V vs. saturated calomel electrode (SCE) for 40 and 60 minutes. The working conditions were determined using electrochemical steady-state polarization measurements. Morphology of the produced composites was observed using scanning electron microscope (SEM), structural characteristics were studied using Raman spectroscopy, while thermal stability was determined using thermal gravimetric analysis (TGA/DTA). The results point out on fibrous and porous structure of PANI-based composites, with strong interaction between quinoidal structure of PANI with carbon nanostructures via p–p stacking according to Raman spectroscopy measurements. TGA coupled with DTA showed the increased thermal stability of the studied composites. The obtained nanocomposites exhibited a high value of conductivity which attributed to the synergy effect of the conductive polymer matrix and carbon nanostructure. Resistivity (i.e., conductivity) changes were measured at different pHs (4 to 10) as well as in different marine regions.
Material Science & Engineering International Journal
The processes of generation, management, treatment and disposal of fly ash industrial waste parti... more The processes of generation, management, treatment and disposal of fly ash industrial waste particles, all over the world, were considered as serious issues of solid waste. The subject of this research work was to create and to characterize the Fly ash/Chitosan composites aimed for heavy metal adsorption in polluted waters. Three different types of fly ash waste particles were used, two types supplied from EURONICKEL and one supplied from OSLOMEJ, Macedonia. The surface of the fly ash (FA) particles was modified by treated with nitric acid (HNO3). Several types of composite adsorbents were prepared using the chitosan as a polymer matrix. The characterization of the metallurgical waste particles was performed by XRF, XRD, TGA, SEM and FTIR analysis, while the obtained composites were tested by TGA, SEM and FTIR analysis. It was observed that the structure, morphology, and some other characteristics of FA particles have been significantly changed after treatment with chitosan and it i...
Material Science & Engineering International Journal
The literature review of the developments of nanomaterials, application methods, their anti-viral... more The literature review of the developments of nanomaterials, application methods, their anti-viral activity confirmed the importance and highlighted the contribution of nanostructures in fighting the corona virus. In order to improve and enhanced the protection function of the facemasks against different viruses, especially last one SARS-CoV-2 (Covid 19), various nanostructures were used, fabricated and modified for that purpose. Among the others, special attention was given on carbon based (carbon nanotubes and graphene) and nano silver, TiO2, iron and cooper with antiviral and antibacterial effects. In this paper, an overview will be presented on several nanostructures used in the facemasks for preventing the spread and protection of Covid 19.
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Papers by Anita Grozdanov