Marijan Marcius - Academia.edu (original) (raw)

Papers by Marijan Marcius

Research paper thumbnail of Sol-gel derived biphasic calcium phosphate ceramics on nitinol for medical applications

International Journal of Electrochemical Science, 2013

ABSTRACT Nitinol is an attractive material for various types of medical implants due to its super... more ABSTRACT Nitinol is an attractive material for various types of medical implants due to its superior mechanical and unique properties (shape memory effect, superelasticity, high damping capacity etc). The Nitinol surface was modified with biocompatible coatings of calcium phosphate prepared by the sol-gel dip-coating method. The surface morphology, structure, and chemical composition of coatings were investigated by field emission scanning electron microscopy (FE - SEM)/energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The barrier properties were investigated in vitro in simulated physiological solution using electrochemical impedance spectroscopy (EIS). It has been shown that the cycling dip-coating-calcining procedure produces homogeneous films with excellent barrier properties.

Research paper thumbnail of Low Temperature Deposition of SiNx Thin Films by the LPCVD Method

Croatica Chemica Acta, 2012

Thin silicon rich nitride (SiN x ) films were deposited using the LPCVD (Low Pressure Chemical Va... more Thin silicon rich nitride (SiN x ) films were deposited using the LPCVD (Low Pressure Chemical Vapor Deposition) method. Silane diluted in argon and ammonia were used as the reactant gasses, and the low temperature deposition at 570 °C was used. The films were deposited on silicon (111) substrates. Films with the different values of the nitrogen content were deposited by varying the ratio of the flows of ammonia and silane in the horizontal tube reactor. The films were characterized in terms on the surface quality (by scanning electron microscopy), in terms of the nitrogen content x by time of flight elastic recoil detection analysis and by Raman and FTIR spectroscopy. The thickness and dielectric constant were measured by ellipsometry. The films were found to have a very smooth, homogeneous surface with nitrogen content that vary from x = 0 to x = 1 in dependence on the deposition parameters. The intensity of the Si-N stretching peak has shown strong correlation with the film thickness measured by ellipsometry. The films showed a smooth surface layer and the value of dielectric constant easily controllable by the ratio of the flow of the gases in the reactor. (doi: 10.5562/cca1970)

Research paper thumbnail of Porous silicon prepared from p− and p++ bulk silicon

ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation... more ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation of p- and p++ doped silicon wafers in hydrofluoric acid (HF) based electrolyte under galvanostatic conditions. Anodisation time and current were varied in order to obtain different PSi morphologies. Samples were characterized by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and Raman spectroscopy. Samples prepared on p- type substrates were macro-porous, showed visible photoluminescence and no observable phonon confinement in Raman spectrum. Porous silicon prepared on p++ type substrates was mesoporous, showed no observable photoluminescence and intense phonon confinement was observed in their Raman spectra. Silicon nanocrystal dimensions in PSi samples obtained from photoluminescence and phonon confinement models were correlated with silicon electrochemical dissolution valence nd. A surface morphology instability is identified in case where electrolyte is more conductive than the silicon substrate.

Research paper thumbnail of Synthesis and properties of iridium-doped hematite (α-Fe2O3)

Journal of Alloys and Compounds, 2012

The effect of the incorporation of Ir 3+ ions on the properties of a-Fe 2 O 3 formed by dehydroxy... more The effect of the incorporation of Ir 3+ ions on the properties of a-Fe 2 O 3 formed by dehydroxylation of a-FeOOH was investigated using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), 57 Fe Mössbauer, UV-Vis-NIR and FT-IR spectroscopies, SQUID magnetometer, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Pure and Ir-doped hematite samples were obtained by heating of pure and Ir-doped goethites (a-FeOOH) formed by precipitation from mixed Fe(III)-Ir(III) chloride solutions in a highly alkaline medium. The incorporation of Ir 3+ ions into the a-Fe 2 O 3 structure led to changes in unit-cell dimensions, crystallinity, particle size and shape, as well as changes in the magnetic, infrared and UV-Vis properties. An increase in the temperature of the Morin transition with an increase in Ir-doping was observed by Mössbauer spectroscopy and magnetic measurements.

Research paper thumbnail of Electrochemical etching of silicon-on-insulator layers using dc and ac currents

Research paper thumbnail of Enhanced near-infrared response of nano- and microstructured silicon/organic hybrid photodetectors

Applied Physics Letters, 2015

Research paper thumbnail of Effects of Experimental Light-activated Bleaching Procedures on Dental Surface Changes

Objective: To evaluate the effects of experimental light-activated bleaching procedures, which de... more Objective: To evaluate the effects of experimental light-activated bleaching procedures, which demonstrated a potential of improving the bleaching process, on surface microstructure and microhardness of human enamel and dentine. Method: Forty human third molars were randomly divided into four groups and dissected in half. One half of molar was used for enamel and other half for dentine microhardness assessment. In each group (n=20), except the control, bleaching of both surfaces was induced by different light source – LED405, OLED or femtosecond laser, for 2×15 minutes. Effects of these experimental light sources on surface microhardness were tested for applications of three bleaching agents – ZOOM2 (Discus Dental, USA), Opalesence BOOST (Ultradent, USA) and 30% VivaStyle (Ivoclar, Liechtenstein). Vickers microhardness was measured at the baseline, after the light-activated bleaching treatment and after 2 weeks storage in either artificial saliva with amorphous calcium phosphate (AC...

Research paper thumbnail of Formation and characterization of ribbon-like RuO2/Ru fibers

Materials Letters, 2015

ABSTRACT Experimental conditions for the formation of RuO2/Ru fibers by electrospinning were inve... more ABSTRACT Experimental conditions for the formation of RuO2/Ru fibers by electrospinning were investigated. Samples were characterized by the FE SEM, XRD, FT-IR and Raman techniques. Round fibers were produced by electrospinning a viscous polyvinylpyrrolidone (PVP)-C2H5OH-H2O solution, whereas with the addition of RuNO(NO3)3, ribbon-like fibers were produced. Heating the ribbon-like fibers of PVP+RuNO(NO3)3 at 400 °C for 1 h yielded a RuO2/Ru composite with the preserved morphology of the precursor. The surface of the ribbon-like RuO2/Ru fibers showed a porous nano/microstructure. PVP+RuNO(NO3)3 foils, produced by freeze-drying the corresponding viscous solution, did not yield ribbon-like fibers upon heating at 400 °C for 1 h. This suggests that the formation of a ribbon-like morphology is the cumulative effect of solvent evaporation during the electrospinning of a viscous solution and the interaction of PVP with RuNO(NO3)3.

Research paper thumbnail of Surface changes of enamel and dentin after two different bleaching procedures

Acta clinica Croatica, 2013

Bleaching agents have effect on chemical/physical and morphological structure of enamel and denti... more Bleaching agents have effect on chemical/physical and morphological structure of enamel and dentin that must be taken into account when this therapy is used. The aim of this in vitro study was to evaluate the effects of two bleaching agents containing a high concentration of hydrogen peroxide for professional use on human enamel and dentin surface and to evaluate the potential remineralizing effect of amorphous calcium phosphate gel (ACP). Twenty-five human third molars were divided into two groups and dissected in half and both surfaces were bleached with either ZOOM2 or Opalescence BOOST for 3 x 15 minutes. Vickers microhardness of enamel and dentin was measured before, after the bleaching treatment, and after treatment with artificial saliva and ACP gel or 2-week storage in deionized water. Surface microstructure was evaluated using scanning electron microscopy. The mixed model ANOVA and Wilcoxon Rank Sum test were used. Both bleaching agents showed significant reduction in surfa...

Research paper thumbnail of Formation of RuO2 nanoparticles by thermal decomposition of Ru(NO)(NO3)3

Ceramics International, 2015

ABSTRACT A simple one-pot synthesis of RuO2 nanoparticles by the thermal decomposition of rutheni... more ABSTRACT A simple one-pot synthesis of RuO2 nanoparticles by the thermal decomposition of ruthenium nitrosyl nitrate [Ru(NO)(NO3)3] up to 800 °C was investigated. The RuO2 phase was characterized by XRD, SAXS, FE SEM/EDS, Raman, DTA/TGA and FT-IR techniques. Broadening of prominent diffraction lines (110), (101) and (211) was used to estimate nanocrystallite sizes in RuO2 particles. FE SEM showed the formation of RuO2 plates at 400 °C which consisted of RuO2 nanoparticles of about 15–25 nm in size. At 800 °C RuO2 nanoparticles showed the sintering effect and some of them increased in size to about 200 nm. Raman and FT-IR spectra consolidated the findings. Moreover, DTA curves showed the decomposition and release of NO and NO3- groups to be a stepwise process.

Research paper thumbnail of Porous silicon prepared from p− and p++ bulk silicon

ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation... more ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation of p- and p++ doped silicon wafers in hydrofluoric acid (HF) based electrolyte under galvanostatic conditions. Anodisation time and current were varied in order to obtain different PSi morphologies. Samples were characterized by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and Raman spectroscopy. Samples prepared on p- type substrates were macro-porous, showed visible photoluminescence and no observable phonon confinement in Raman spectrum. Porous silicon prepared on p++ type substrates was mesoporous, showed no observable photoluminescence and intense phonon confinement was observed in their Raman spectra. Silicon nanocrystal dimensions in PSi samples obtained from photoluminescence and phonon confinement models were correlated with silicon electrochemical dissolution valence nd. A surface morphology instability is identified in case where electrolyte is more conductive than the silicon substrate.

Research paper thumbnail of The Influence of Experimental Conditions on the Formation of ZnO Fibers by Electrospinning

Croatica Chemica Acta, 2014

The influence of experimental conditions on the formation of ZnO fibers by electrospinning has be... more The influence of experimental conditions on the formation of ZnO fibers by electrospinning has been investigated. The electrospinning of a viscous suspension containing polyvinylpyrrolidone and zinc acetate in C2H5OH/H2O produced very long fibers (several hundred μm). Upon calcination a thin deposit of precursor fibers at 400 or 500 °C for 1 h the fibers consisting of ZnO nanoparticles were obtained. On the other hand, ZnO fibers were not obtained upon heating a thick deposit of precursor fibers at 600 °C for 6 h. At all three heating temperatures (400, 500 or 600 °C) ZnO nanoparticles with a gradual increase in size were produced. The Raman spectrum of ZnO nanoparticles formed at 600 °C showed additional bands which were assigned to graphene oxide. It was suggested that in the thick deposit the organic component did not burn out completely, i.e., the residual carbon (graphite) transformed into graphene oxide for the experimental conditions applied. Figure 10. Deconvolution of D (disorder) and G (graphite) Raman bands, characteristic of graphene oxide (GO).

Research paper thumbnail of Optical Effects of Experimental Light-Activated Bleaching Procedures

Photomedicine and Laser Surgery, 2014

The purpose of this study was to evaluate the efficiency of experimental light-activated bleachin... more The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures. The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching. Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy. Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis. The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

Research paper thumbnail of Synthesis and long-term phase stability of Mn3O4 nanoparticles

Journal of Molecular Structure, 2013

Research paper thumbnail of Thermal decomposition of hydrated salts of Ni(II)-acetate and Ni(II)-lactate

Journal of Molecular Structure, 2013

Research paper thumbnail of Formation and microstructure of nickel oxide films

Journal of Alloys and Compounds, 2012

The formation and microstructure of NiO films on different substrates were monitored using XRD, R... more The formation and microstructure of NiO films on different substrates were monitored using XRD, Raman, UV/Vis/NIR and FE-SEM/EDS techniques. The formation of NiO films on Ni plates in air atmosphere between 400 and 800°C was confirmed by XRD and Raman spectroscopy. The origin of Raman bands and corresponding Raman shifts in the samples are discussed. An increase in the size of NiO particles in the films from nano to micro dimensions was demonstrated. A change in the atomic ratio Ni:O with an increase in heating temperature was observed. Polished Ni plates coated with a thin Ni-acetate layer upon heating at high temperatures gave similar NiO microstructures on the surface like in the case of non-treated Ni plates. Glass substrates coated with thin Ni-acetate films upon heating between 400 and 800°C yielded pseudospherical NiO nanoparticles. The dominant Raman band as an indicator of NiO formation on a glass substrate was shown. The formation of NiO nanoparticles on glass substrates with maximum size distribution from 16 to 27 nm in a broad temperature range from 400 to 800°C can be explained by the absence of a constant source of metallic nickel which was present in the case of Ni plates.

Research paper thumbnail of Formation of Iron Oxides by Surface Oxidation of Iron Plate

Croatica Chemica Acta, 2012

Oxidation of iron plates (α-phase) at high temperatures and in atmospheric conditions was monitor... more Oxidation of iron plates (α-phase) at high temperatures and in atmospheric conditions was monitored. The composition of oxidation products was analyzed with XRD, Raman and Mössbauer spectroscopies, whereas the morphologies of oxidation products were inspected by FE-SEM.

Research paper thumbnail of Dependence of NiO microstructure on the electrospinning conditions

Ceramics International, 2014

A strong effect of the electrospinning conditions on NiO microstructure was noticed. Viscous solu... more A strong effect of the electrospinning conditions on NiO microstructure was noticed. Viscous solutions containing nickel nitrate (Ni(NO 3 ) 2 ), polyvinylpyrrolidone (PVP), ethanol (C 2 H 5 OH), and H 2 O were prepared. Produced electrospun fibers were thermally treated. The chemical composition of the viscous solution, the time of electrospinning and calcination played a crucial role in the formation of corresponding nickel oxide (NiO) microstructures. At a lower Ni(NO 3 ) 2 concentration a porous microstructure consisting of interconnected fibers was obtained, whereas at a higher Ni(NO 3 ) 2 concentration a laminar microstructure was obtained. The formation of metallic Ni was assigned to the reducing action of PVP during the heating of electrospun fibers. Based on EDS and XRD analyses it was suggested that metallic Ni was restricted to the surface of NiO particles. With a prolonged heating time at increased temperature metallic Ni was reoxidized to NiO.

Research paper thumbnail of Sol-gel derived biphasic calcium phosphate ceramics on nitinol for medical applications

International Journal of Electrochemical Science, 2013

ABSTRACT Nitinol is an attractive material for various types of medical implants due to its super... more ABSTRACT Nitinol is an attractive material for various types of medical implants due to its superior mechanical and unique properties (shape memory effect, superelasticity, high damping capacity etc). The Nitinol surface was modified with biocompatible coatings of calcium phosphate prepared by the sol-gel dip-coating method. The surface morphology, structure, and chemical composition of coatings were investigated by field emission scanning electron microscopy (FE - SEM)/energy dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The barrier properties were investigated in vitro in simulated physiological solution using electrochemical impedance spectroscopy (EIS). It has been shown that the cycling dip-coating-calcining procedure produces homogeneous films with excellent barrier properties.

Research paper thumbnail of Low Temperature Deposition of SiNx Thin Films by the LPCVD Method

Croatica Chemica Acta, 2012

Thin silicon rich nitride (SiN x ) films were deposited using the LPCVD (Low Pressure Chemical Va... more Thin silicon rich nitride (SiN x ) films were deposited using the LPCVD (Low Pressure Chemical Vapor Deposition) method. Silane diluted in argon and ammonia were used as the reactant gasses, and the low temperature deposition at 570 °C was used. The films were deposited on silicon (111) substrates. Films with the different values of the nitrogen content were deposited by varying the ratio of the flows of ammonia and silane in the horizontal tube reactor. The films were characterized in terms on the surface quality (by scanning electron microscopy), in terms of the nitrogen content x by time of flight elastic recoil detection analysis and by Raman and FTIR spectroscopy. The thickness and dielectric constant were measured by ellipsometry. The films were found to have a very smooth, homogeneous surface with nitrogen content that vary from x = 0 to x = 1 in dependence on the deposition parameters. The intensity of the Si-N stretching peak has shown strong correlation with the film thickness measured by ellipsometry. The films showed a smooth surface layer and the value of dielectric constant easily controllable by the ratio of the flow of the gases in the reactor. (doi: 10.5562/cca1970)

Research paper thumbnail of Porous silicon prepared from p− and p++ bulk silicon

ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation... more ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation of p- and p++ doped silicon wafers in hydrofluoric acid (HF) based electrolyte under galvanostatic conditions. Anodisation time and current were varied in order to obtain different PSi morphologies. Samples were characterized by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and Raman spectroscopy. Samples prepared on p- type substrates were macro-porous, showed visible photoluminescence and no observable phonon confinement in Raman spectrum. Porous silicon prepared on p++ type substrates was mesoporous, showed no observable photoluminescence and intense phonon confinement was observed in their Raman spectra. Silicon nanocrystal dimensions in PSi samples obtained from photoluminescence and phonon confinement models were correlated with silicon electrochemical dissolution valence nd. A surface morphology instability is identified in case where electrolyte is more conductive than the silicon substrate.

Research paper thumbnail of Synthesis and properties of iridium-doped hematite (α-Fe2O3)

Journal of Alloys and Compounds, 2012

The effect of the incorporation of Ir 3+ ions on the properties of a-Fe 2 O 3 formed by dehydroxy... more The effect of the incorporation of Ir 3+ ions on the properties of a-Fe 2 O 3 formed by dehydroxylation of a-FeOOH was investigated using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), 57 Fe Mössbauer, UV-Vis-NIR and FT-IR spectroscopies, SQUID magnetometer, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Pure and Ir-doped hematite samples were obtained by heating of pure and Ir-doped goethites (a-FeOOH) formed by precipitation from mixed Fe(III)-Ir(III) chloride solutions in a highly alkaline medium. The incorporation of Ir 3+ ions into the a-Fe 2 O 3 structure led to changes in unit-cell dimensions, crystallinity, particle size and shape, as well as changes in the magnetic, infrared and UV-Vis properties. An increase in the temperature of the Morin transition with an increase in Ir-doping was observed by Mössbauer spectroscopy and magnetic measurements.

Research paper thumbnail of Electrochemical etching of silicon-on-insulator layers using dc and ac currents

Research paper thumbnail of Enhanced near-infrared response of nano- and microstructured silicon/organic hybrid photodetectors

Applied Physics Letters, 2015

Research paper thumbnail of Effects of Experimental Light-activated Bleaching Procedures on Dental Surface Changes

Objective: To evaluate the effects of experimental light-activated bleaching procedures, which de... more Objective: To evaluate the effects of experimental light-activated bleaching procedures, which demonstrated a potential of improving the bleaching process, on surface microstructure and microhardness of human enamel and dentine. Method: Forty human third molars were randomly divided into four groups and dissected in half. One half of molar was used for enamel and other half for dentine microhardness assessment. In each group (n=20), except the control, bleaching of both surfaces was induced by different light source – LED405, OLED or femtosecond laser, for 2×15 minutes. Effects of these experimental light sources on surface microhardness were tested for applications of three bleaching agents – ZOOM2 (Discus Dental, USA), Opalesence BOOST (Ultradent, USA) and 30% VivaStyle (Ivoclar, Liechtenstein). Vickers microhardness was measured at the baseline, after the light-activated bleaching treatment and after 2 weeks storage in either artificial saliva with amorphous calcium phosphate (AC...

Research paper thumbnail of Formation and characterization of ribbon-like RuO2/Ru fibers

Materials Letters, 2015

ABSTRACT Experimental conditions for the formation of RuO2/Ru fibers by electrospinning were inve... more ABSTRACT Experimental conditions for the formation of RuO2/Ru fibers by electrospinning were investigated. Samples were characterized by the FE SEM, XRD, FT-IR and Raman techniques. Round fibers were produced by electrospinning a viscous polyvinylpyrrolidone (PVP)-C2H5OH-H2O solution, whereas with the addition of RuNO(NO3)3, ribbon-like fibers were produced. Heating the ribbon-like fibers of PVP+RuNO(NO3)3 at 400 °C for 1 h yielded a RuO2/Ru composite with the preserved morphology of the precursor. The surface of the ribbon-like RuO2/Ru fibers showed a porous nano/microstructure. PVP+RuNO(NO3)3 foils, produced by freeze-drying the corresponding viscous solution, did not yield ribbon-like fibers upon heating at 400 °C for 1 h. This suggests that the formation of a ribbon-like morphology is the cumulative effect of solvent evaporation during the electrospinning of a viscous solution and the interaction of PVP with RuNO(NO3)3.

Research paper thumbnail of Surface changes of enamel and dentin after two different bleaching procedures

Acta clinica Croatica, 2013

Bleaching agents have effect on chemical/physical and morphological structure of enamel and denti... more Bleaching agents have effect on chemical/physical and morphological structure of enamel and dentin that must be taken into account when this therapy is used. The aim of this in vitro study was to evaluate the effects of two bleaching agents containing a high concentration of hydrogen peroxide for professional use on human enamel and dentin surface and to evaluate the potential remineralizing effect of amorphous calcium phosphate gel (ACP). Twenty-five human third molars were divided into two groups and dissected in half and both surfaces were bleached with either ZOOM2 or Opalescence BOOST for 3 x 15 minutes. Vickers microhardness of enamel and dentin was measured before, after the bleaching treatment, and after treatment with artificial saliva and ACP gel or 2-week storage in deionized water. Surface microstructure was evaluated using scanning electron microscopy. The mixed model ANOVA and Wilcoxon Rank Sum test were used. Both bleaching agents showed significant reduction in surfa...

Research paper thumbnail of Formation of RuO2 nanoparticles by thermal decomposition of Ru(NO)(NO3)3

Ceramics International, 2015

ABSTRACT A simple one-pot synthesis of RuO2 nanoparticles by the thermal decomposition of rutheni... more ABSTRACT A simple one-pot synthesis of RuO2 nanoparticles by the thermal decomposition of ruthenium nitrosyl nitrate [Ru(NO)(NO3)3] up to 800 °C was investigated. The RuO2 phase was characterized by XRD, SAXS, FE SEM/EDS, Raman, DTA/TGA and FT-IR techniques. Broadening of prominent diffraction lines (110), (101) and (211) was used to estimate nanocrystallite sizes in RuO2 particles. FE SEM showed the formation of RuO2 plates at 400 °C which consisted of RuO2 nanoparticles of about 15–25 nm in size. At 800 °C RuO2 nanoparticles showed the sintering effect and some of them increased in size to about 200 nm. Raman and FT-IR spectra consolidated the findings. Moreover, DTA curves showed the decomposition and release of NO and NO3- groups to be a stepwise process.

Research paper thumbnail of Porous silicon prepared from p− and p++ bulk silicon

ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation... more ABSTRACT Macro and meso-porous silicon (PSi) samples were prepared by electrochemical anodisation of p- and p++ doped silicon wafers in hydrofluoric acid (HF) based electrolyte under galvanostatic conditions. Anodisation time and current were varied in order to obtain different PSi morphologies. Samples were characterized by scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and Raman spectroscopy. Samples prepared on p- type substrates were macro-porous, showed visible photoluminescence and no observable phonon confinement in Raman spectrum. Porous silicon prepared on p++ type substrates was mesoporous, showed no observable photoluminescence and intense phonon confinement was observed in their Raman spectra. Silicon nanocrystal dimensions in PSi samples obtained from photoluminescence and phonon confinement models were correlated with silicon electrochemical dissolution valence nd. A surface morphology instability is identified in case where electrolyte is more conductive than the silicon substrate.

Research paper thumbnail of The Influence of Experimental Conditions on the Formation of ZnO Fibers by Electrospinning

Croatica Chemica Acta, 2014

The influence of experimental conditions on the formation of ZnO fibers by electrospinning has be... more The influence of experimental conditions on the formation of ZnO fibers by electrospinning has been investigated. The electrospinning of a viscous suspension containing polyvinylpyrrolidone and zinc acetate in C2H5OH/H2O produced very long fibers (several hundred μm). Upon calcination a thin deposit of precursor fibers at 400 or 500 °C for 1 h the fibers consisting of ZnO nanoparticles were obtained. On the other hand, ZnO fibers were not obtained upon heating a thick deposit of precursor fibers at 600 °C for 6 h. At all three heating temperatures (400, 500 or 600 °C) ZnO nanoparticles with a gradual increase in size were produced. The Raman spectrum of ZnO nanoparticles formed at 600 °C showed additional bands which were assigned to graphene oxide. It was suggested that in the thick deposit the organic component did not burn out completely, i.e., the residual carbon (graphite) transformed into graphene oxide for the experimental conditions applied. Figure 10. Deconvolution of D (disorder) and G (graphite) Raman bands, characteristic of graphene oxide (GO).

Research paper thumbnail of Optical Effects of Experimental Light-Activated Bleaching Procedures

Photomedicine and Laser Surgery, 2014

The purpose of this study was to evaluate the efficiency of experimental light-activated bleachin... more The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures. The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching. Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy. Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis. The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

Research paper thumbnail of Synthesis and long-term phase stability of Mn3O4 nanoparticles

Journal of Molecular Structure, 2013

Research paper thumbnail of Thermal decomposition of hydrated salts of Ni(II)-acetate and Ni(II)-lactate

Journal of Molecular Structure, 2013

Research paper thumbnail of Formation and microstructure of nickel oxide films

Journal of Alloys and Compounds, 2012

The formation and microstructure of NiO films on different substrates were monitored using XRD, R... more The formation and microstructure of NiO films on different substrates were monitored using XRD, Raman, UV/Vis/NIR and FE-SEM/EDS techniques. The formation of NiO films on Ni plates in air atmosphere between 400 and 800°C was confirmed by XRD and Raman spectroscopy. The origin of Raman bands and corresponding Raman shifts in the samples are discussed. An increase in the size of NiO particles in the films from nano to micro dimensions was demonstrated. A change in the atomic ratio Ni:O with an increase in heating temperature was observed. Polished Ni plates coated with a thin Ni-acetate layer upon heating at high temperatures gave similar NiO microstructures on the surface like in the case of non-treated Ni plates. Glass substrates coated with thin Ni-acetate films upon heating between 400 and 800°C yielded pseudospherical NiO nanoparticles. The dominant Raman band as an indicator of NiO formation on a glass substrate was shown. The formation of NiO nanoparticles on glass substrates with maximum size distribution from 16 to 27 nm in a broad temperature range from 400 to 800°C can be explained by the absence of a constant source of metallic nickel which was present in the case of Ni plates.

Research paper thumbnail of Formation of Iron Oxides by Surface Oxidation of Iron Plate

Croatica Chemica Acta, 2012

Oxidation of iron plates (α-phase) at high temperatures and in atmospheric conditions was monitor... more Oxidation of iron plates (α-phase) at high temperatures and in atmospheric conditions was monitored. The composition of oxidation products was analyzed with XRD, Raman and Mössbauer spectroscopies, whereas the morphologies of oxidation products were inspected by FE-SEM.

Research paper thumbnail of Dependence of NiO microstructure on the electrospinning conditions

Ceramics International, 2014

A strong effect of the electrospinning conditions on NiO microstructure was noticed. Viscous solu... more A strong effect of the electrospinning conditions on NiO microstructure was noticed. Viscous solutions containing nickel nitrate (Ni(NO 3 ) 2 ), polyvinylpyrrolidone (PVP), ethanol (C 2 H 5 OH), and H 2 O were prepared. Produced electrospun fibers were thermally treated. The chemical composition of the viscous solution, the time of electrospinning and calcination played a crucial role in the formation of corresponding nickel oxide (NiO) microstructures. At a lower Ni(NO 3 ) 2 concentration a porous microstructure consisting of interconnected fibers was obtained, whereas at a higher Ni(NO 3 ) 2 concentration a laminar microstructure was obtained. The formation of metallic Ni was assigned to the reducing action of PVP during the heating of electrospun fibers. Based on EDS and XRD analyses it was suggested that metallic Ni was restricted to the surface of NiO particles. With a prolonged heating time at increased temperature metallic Ni was reoxidized to NiO.