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Rajić, Vladimir B.

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Author's Bibliography

Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry

Rajić, Vladimir; Stojković Simatović, Ivana; Veselinović, Ljiljana; Belošević Čavor, Jelena; Novaković, Mirjana; Popović, Maja; Škapin, Srečo Davor; Mojović, Miloš; Stojadinović, Stevan; Rac, Vladislav; Janković Častvan, Ivona; Marković, Smilja

(Royal Society of Chemistry, 2020)

TY  - JOUR
AU  - Rajić, Vladimir
AU  - Stojković Simatović, Ivana
AU  - Veselinović, Ljiljana
AU  - Belošević Čavor, Jelena
AU  - Novaković, Mirjana
AU  - Popović, Maja
AU  - Škapin, Srečo Davor
AU  - Mojović, Miloš
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Janković Častvan, Ivona
AU  - Marković, Smilja
PY  - 2020
UR  - https://pubs.rsc.org/en/content/articlelanding/2020/cp/d0cp03377d
UR  - https://dais.sanu.ac.rs/123456789/9544
AB  - Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1−xFexO, x = 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn2+ partial substitution with Fe3+ on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 V vs. RHE), current density (0.231 mA cm−2 at 0.150 V vs. RHE), and faster kinetics (Tafel slope, b = 248 mV dec−1), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (000) facets. Quite the contrary, the OER study showed that the introduction of Fe3+ ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm−2 at 2.216 V vs. RHE, an onset potential of 1.856 V vs. RHE, and the smallest potential difference between the OER and ORR (ΔE = 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.
PB  - Royal Society of Chemistry
T2  - Physical Chemistry Chemical Physics
T1  - Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry
SP  - 22078
EP  - 22095
VL  - 22
IS  - 38
DO  - 10.1039/D0CP03377D
ER  - 
@article{
author = "Rajić, Vladimir and Stojković Simatović, Ivana and Veselinović, Ljiljana and Belošević Čavor, Jelena and Novaković, Mirjana and Popović, Maja and Škapin, Srečo Davor and Mojović, Miloš and Stojadinović, Stevan and Rac, Vladislav and Janković Častvan, Ivona and Marković, Smilja",
year = "2020",
url = "https://pubs.rsc.org/en/content/articlelanding/2020/cp/d0cp03377d, https://dais.sanu.ac.rs/123456789/9544",
abstract = "Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1−xFexO, x = 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn2+ partial substitution with Fe3+ on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 V vs. RHE), current density (0.231 mA cm−2 at 0.150 V vs. RHE), and faster kinetics (Tafel slope, b = 248 mV dec−1), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (000) facets. Quite the contrary, the OER study showed that the introduction of Fe3+ ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm−2 at 2.216 V vs. RHE, an onset potential of 1.856 V vs. RHE, and the smallest potential difference between the OER and ORR (ΔE = 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.",
publisher = "Royal Society of Chemistry",
journal = "Physical Chemistry Chemical Physics",
title = "Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry",
pages = "22078-22095",
volume = "22",
number = "38",
doi = "10.1039/D0CP03377D"
}

Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry

Rajić, Vladimir; Stojković Simatović, Ivana; Veselinović, Ljiljana; Belošević Čavor, Jelena; Novaković, Mirjana; Popović, Maja; Škapin, Srečo Davor; Mojović, Miloš; Stojadinović, Stevan; Rac, Vladislav; Janković Častvan, Ivona; Marković, Smilja

(Royal Society of Chemistry, 2020)

TY  - JOUR
AU  - Rajić, Vladimir
AU  - Stojković Simatović, Ivana
AU  - Veselinović, Ljiljana
AU  - Belošević Čavor, Jelena
AU  - Novaković, Mirjana
AU  - Popović, Maja
AU  - Škapin, Srečo Davor
AU  - Mojović, Miloš
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Janković Častvan, Ivona
AU  - Marković, Smilja
PY  - 2020
UR  - https://pubs.rsc.org/en/content/articlelanding/2020/cp/d0cp03377d
UR  - https://dais.sanu.ac.rs/123456789/9543
AB  - Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1−xFexO, x = 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn2+ partial substitution with Fe3+ on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 V vs. RHE), current density (0.231 mA cm−2 at 0.150 V vs. RHE), and faster kinetics (Tafel slope, b = 248 mV dec−1), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (000) facets. Quite the contrary, the OER study showed that the introduction of Fe3+ ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm−2 at 2.216 V vs. RHE, an onset potential of 1.856 V vs. RHE, and the smallest potential difference between the OER and ORR (ΔE = 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.
PB  - Royal Society of Chemistry
T2  - Physical Chemistry Chemical Physics
T1  - Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry
SP  - 22078
EP  - 22095
VL  - 22
IS  - 38
DO  - 10.1039/D0CP03377D
ER  - 
@article{
author = "Rajić, Vladimir and Stojković Simatović, Ivana and Veselinović, Ljiljana and Belošević Čavor, Jelena and Novaković, Mirjana and Popović, Maja and Škapin, Srečo Davor and Mojović, Miloš and Stojadinović, Stevan and Rac, Vladislav and Janković Častvan, Ivona and Marković, Smilja",
year = "2020",
url = "https://pubs.rsc.org/en/content/articlelanding/2020/cp/d0cp03377d, https://dais.sanu.ac.rs/123456789/9543",
abstract = "Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1−xFexO, x = 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn2+ partial substitution with Fe3+ on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 V vs. RHE), current density (0.231 mA cm−2 at 0.150 V vs. RHE), and faster kinetics (Tafel slope, b = 248 mV dec−1), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (000) facets. Quite the contrary, the OER study showed that the introduction of Fe3+ ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm−2 at 2.216 V vs. RHE, an onset potential of 1.856 V vs. RHE, and the smallest potential difference between the OER and ORR (ΔE = 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.",
publisher = "Royal Society of Chemistry",
journal = "Physical Chemistry Chemical Physics",
title = "Bifunctional catalytic activity of Zn1−xFexO toward the OER/ORR: seeking an optimal stoichiometry",
pages = "22078-22095",
volume = "22",
number = "38",
doi = "10.1039/D0CP03377D"
}

Point defect-enhanced optical and photoelectrochemical water splitting activity of nanostructured Zn1-xFeyO(1-x+1.5y)

Marković, Smilja; Rajić, Vladimir B.; Stojković Simatović, Ivana; Veselinović, Ljiljana; Belošević Čavor, Jelena; Ivanovski, Valentin N.; Novaković, Mirjana; Škapin, Srečo Davor; Stojadinović, Stevan; Rac, Vladislav; Uskoković, Dragan

(Belgrade : Materials Research Society of Serbia, 2019)

TY  - CONF
AU  - Marković, Smilja
AU  - Rajić, Vladimir B.
AU  - Stojković Simatović, Ivana
AU  - Veselinović, Ljiljana
AU  - Belošević Čavor, Jelena
AU  - Ivanovski, Valentin N.
AU  - Novaković, Mirjana
AU  - Škapin, Srečo Davor
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Uskoković, Dragan
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/6677
AB  - Even has been under study since 1935, zinc oxide (ZnO) based materials still attract a huge scientific attention. Owing to a wide band gap energy (3.37 eV at room temperature) and a large exciton binding energy (60 meV) ZnO has a variety of application, e.g. in electronics, optoelectronics, spintronics and photocatalysis. Besides, it has been shown that zinc oxide-based materials have a great potential as photoelectrocatalysts in the processes of water splitting, yielding an increased both photocurrent density and photoconversion efficiency. However, with a band gap energy of 3.37 eV, ZnO is restricted to absorb UV light only. This restriction can be overcome by modifying optical properties of zinc oxide particles. During the years different approaches have been applied to modify the visible light photocatalytic activity of ZnO materials, for example: (1) metal and nonmetal ion doping, (2) hydrogenation, (3) the incorporation of crystalline defects in the form of vacancies and interstitials, (4) the modification of particles morphology and surface topology, etc.
In this study we employed 3d metal ion substitution to improve visible light-driven photoactivity of zinc oxide particles. We investigated the influence of Fe concentration in Zn1-xFeyO(1-x+1.5y) nanoparticles on crystal structure, textural, optical and photoelectrocatalytic properties. Zn1-xFeyO(1-x+1.5y) nanoparticles with nominally 5, 10, 15 and 20 at.% of Fe ions were synthesized by microwave processing of a precipitate. The crystal structure and phase purity of the samples were investigated by X-ray diffraction, Raman and ATR-FTIR spectroscopy. Mössbauer spectroscopy was carried out to clarify the valence state of the iron ions in the ZnO crystal structure. Effects of the iron ions concentration on particles morphology and texture properties were observed with field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) with elemental mapping, and nitrogen adsorption–desorption isotherm, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence (PL) spectroscopy. Photoelectrochemical activity of the Zn1-xFeyO(1-x+1.5y) samples as anode material was evaluated by linear sweep voltammetry in Na2SO4 electrolyte; the oxygen evolution kinetics were determined and compared. In addition, a series of first principles calculations were performed to address the influence of the iron concentration on the electronic structure of Zn1-xFeyO(1-x+1.5y) samples.
PB  - Belgrade : Materials Research Society of Serbia
C3  - Programme and The Book of abstracts / Twenty-first Annual Conference YUCOMAT 2019 & Eleventh World Round Table Conference on Sintering WRTCS 2019, Herceg Novi, Montenegro, September 2-6, 2019
T1  - Point defect-enhanced optical and photoelectrochemical water splitting activity of nanostructured Zn1-xFeyO(1-x+1.5y)
SP  - 54
EP  - 54
ER  - 
@conference{
author = "Marković, Smilja and Rajić, Vladimir B. and Stojković Simatović, Ivana and Veselinović, Ljiljana and Belošević Čavor, Jelena and Ivanovski, Valentin N. and Novaković, Mirjana and Škapin, Srečo Davor and Stojadinović, Stevan and Rac, Vladislav and Uskoković, Dragan",
year = "2019",
url = "http://dais.sanu.ac.rs/123456789/6677",
abstract = "Even has been under study since 1935, zinc oxide (ZnO) based materials still attract a huge scientific attention. Owing to a wide band gap energy (3.37 eV at room temperature) and a large exciton binding energy (60 meV) ZnO has a variety of application, e.g. in electronics, optoelectronics, spintronics and photocatalysis. Besides, it has been shown that zinc oxide-based materials have a great potential as photoelectrocatalysts in the processes of water splitting, yielding an increased both photocurrent density and photoconversion efficiency. However, with a band gap energy of 3.37 eV, ZnO is restricted to absorb UV light only. This restriction can be overcome by modifying optical properties of zinc oxide particles. During the years different approaches have been applied to modify the visible light photocatalytic activity of ZnO materials, for example: (1) metal and nonmetal ion doping, (2) hydrogenation, (3) the incorporation of crystalline defects in the form of vacancies and interstitials, (4) the modification of particles morphology and surface topology, etc.
In this study we employed 3d metal ion substitution to improve visible light-driven photoactivity of zinc oxide particles. We investigated the influence of Fe concentration in Zn1-xFeyO(1-x+1.5y) nanoparticles on crystal structure, textural, optical and photoelectrocatalytic properties. Zn1-xFeyO(1-x+1.5y) nanoparticles with nominally 5, 10, 15 and 20 at.% of Fe ions were synthesized by microwave processing of a precipitate. The crystal structure and phase purity of the samples were investigated by X-ray diffraction, Raman and ATR-FTIR spectroscopy. Mössbauer spectroscopy was carried out to clarify the valence state of the iron ions in the ZnO crystal structure. Effects of the iron ions concentration on particles morphology and texture properties were observed with field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) with elemental mapping, and nitrogen adsorption–desorption isotherm, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence (PL) spectroscopy. Photoelectrochemical activity of the Zn1-xFeyO(1-x+1.5y) samples as anode material was evaluated by linear sweep voltammetry in Na2SO4 electrolyte; the oxygen evolution kinetics were determined and compared. In addition, a series of first principles calculations were performed to address the influence of the iron concentration on the electronic structure of Zn1-xFeyO(1-x+1.5y) samples.",
publisher = "Belgrade : Materials Research Society of Serbia",
journal = "Programme and The Book of abstracts / Twenty-first Annual Conference YUCOMAT 2019 & Eleventh World Round Table Conference on Sintering WRTCS 2019, Herceg Novi, Montenegro, September 2-6, 2019",
title = "Point defect-enhanced optical and photoelectrochemical water splitting activity of nanostructured Zn1-xFeyO(1-x+1.5y)",
pages = "54-54"
}

A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions

Ivanovski, Valentin N.; Belošević-Čavor, Jelena; Rajić, Vladimir; Umićević, Ana; Marković, Smilja; Kusigerski, Vladan; Mitrić, Miodrag; Koteski, Vasil

(AIP Publishing, 2019)

TY  - JOUR
AU  - Ivanovski, Valentin N.
AU  - Belošević-Čavor, Jelena
AU  - Rajić, Vladimir
AU  - Umićević, Ana
AU  - Marković, Smilja
AU  - Kusigerski, Vladan
AU  - Mitrić, Miodrag
AU  - Koteski, Vasil
PY  - 2019
UR  - https://aip.scitation.org/doi/10.1063/1.5095837
UR  - http://dais.sanu.ac.rs/123456789/6883
AB  - In order to study the effect of Fe cation substitution on the local structure, defect formation, and hyperfine interactions in ZnO, Mössbauer spectroscopy measurements of the microwave processed Zn1−xFexO (x=0.05, 0.10, 0.15, and 0.20) nanoparticles, together with ab initio calculations, were performed. Complementary information on the distribution of particle size and morphology, as well as magnetic properties, were obtained by X-ray diffraction, transmission electron microscopy, and squid-magnetometry. The selected model for analyzing the Mössbauer spectra of our samples is a distribution of quadrupole splittings. The fitting model with two Lorentz doublets was rejected due to its failure to include larger doublets. The Fe3+ ions do not yield magnetic ordering in the samples at room temperature. The results from first-principles calculations confirm that the major component of the Mössbauer spectra corresponds to the Fe-alloyed ZnO with Zn vacancy in the next nearest neighbor environment. The magnetic measurements are consistent with the description of the distribution of iron ions over the randomly formed clusters in the ZnO host lattice. While at room temperature all the samples are paramagnetic, magnetic interactions cause a transition into a cluster spin-glass state at low temperatures.
PB  - AIP Publishing
T2  - Journal of Applied Physics
T1  - A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions
SP  - 125703
VL  - 126
IS  - 12
DO  - 10.1063/1.5095837
ER  - 
@article{
author = "Ivanovski, Valentin N. and Belošević-Čavor, Jelena and Rajić, Vladimir and Umićević, Ana and Marković, Smilja and Kusigerski, Vladan and Mitrić, Miodrag and Koteski, Vasil",
year = "2019",
url = "https://aip.scitation.org/doi/10.1063/1.5095837, http://dais.sanu.ac.rs/123456789/6883",
abstract = "In order to study the effect of Fe cation substitution on the local structure, defect formation, and hyperfine interactions in ZnO, Mössbauer spectroscopy measurements of the microwave processed Zn1−xFexO (x=0.05, 0.10, 0.15, and 0.20) nanoparticles, together with ab initio calculations, were performed. Complementary information on the distribution of particle size and morphology, as well as magnetic properties, were obtained by X-ray diffraction, transmission electron microscopy, and squid-magnetometry. The selected model for analyzing the Mössbauer spectra of our samples is a distribution of quadrupole splittings. The fitting model with two Lorentz doublets was rejected due to its failure to include larger doublets. The Fe3+ ions do not yield magnetic ordering in the samples at room temperature. The results from first-principles calculations confirm that the major component of the Mössbauer spectra corresponds to the Fe-alloyed ZnO with Zn vacancy in the next nearest neighbor environment. The magnetic measurements are consistent with the description of the distribution of iron ions over the randomly formed clusters in the ZnO host lattice. While at room temperature all the samples are paramagnetic, magnetic interactions cause a transition into a cluster spin-glass state at low temperatures.",
publisher = "AIP Publishing",
journal = "Journal of Applied Physics",
title = "A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions",
pages = "125703",
volume = "126",
number = "12",
doi = "10.1063/1.5095837"
}
2
1
2

Tuning the optical, electrical and photoelectrocatalytic properties of Zno materials by varying of intrinsic defects concentration

Marković, Smilja; Rajić, Vladimir; Veselinović, Ljiljana; Stojković Simatović, Ivana; Belošević Čavor, Jelena; Škapin, Srečo Davor; Kovač, Janez; Nikolić, Marko G.; Uskoković, Dragan

(Budapest : [s. n.], 2019)

TY  - CONF
AU  - Marković, Smilja
AU  - Rajić, Vladimir
AU  - Veselinović, Ljiljana
AU  - Stojković Simatović, Ivana
AU  - Belošević Čavor, Jelena
AU  - Škapin, Srečo Davor
AU  - Kovač, Janez
AU  - Nikolić, Marko G.
AU  - Uskoković, Dragan
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/6997
AB  - During the last decade zinc oxide (ZnO) has attracted considerable attention as a promising material for electronic, optoelectronic and spintronic devices. ZnO has a wide bandgap (3.37 eV at room temperature) and relatively large exciton binding energy (60 meV) which enables multifunctional application. Until now ZnO-based materials have been used as UV and blue light emitters, varistors, thermistors, semiconductors, photoanodes, and other. Various approaches have been applied to improve functional properties of zinc oxide, such as: fabrication of ZnO-based heterojunction particles, particles’ surface sensitization, hydrogenation, etc. It has been found that intrinsic defects (vacancies, interstitials and antisites) in the crystal structure of a ZnO strongly influenced its electrical and optical properties. Thus, correlation of the intrinsic defects concentration with optical and electrical properties of ZnO materials is of great importance for their further application in opto-electronic devices. In this study we investigated the influence of intrinsic defects concentration on the optical, electrical and photoelectrocatalytic properties of ZnO materials. To obtain ZnO powder with a high concentration of intrinsic defects microwave processing of precipitate was employed, while for further varying of defects concentration, the powder was thermally treated in three different atmospheres: air, argon and oxygen. The ZnO powder was uniaxially pressed (P = 100 MPa) in cylindrical compacts (R= 6 mm and h approx. 3 mm) which were sintered in different atmospheres by heating rate of 10 °/min up to 1100 °C, and with dwell time of 1 h. To study a crystal structure of ZnO samples XRD and Raman spectroscopy were used, while for microstructural investigation field emission scanning electron micrographs were recorded. Optical properties were studied using UV–Vis diffuse reflectance spectroscopy. To reveal the role of intrinsic defects in ZnO crystal lattice on functional properties, XPS, photoluminescence, electroluminescence and electrochemical impedance spectra were analyzed. A detailed analysis of the experimental results imply that a high concentration of intrinsic defects, in particular oxygen vacancies, is of the greatest importance for tunable light-emitting diode application and significant for the photoanode properties. To support our experimental observation we performed ab initio calculations based on density functional theory (DFT).
PB  - Budapest : [s. n.]
C3  - Abstracts / International Workshop on Woman in Ceramic Science (WoCeram2019), April 7-9, 2019/ Budapest, Hungary, Novotel Danube Budapest
T1  - Tuning the optical, electrical and photoelectrocatalytic properties of Zno materials by varying of intrinsic defects concentration
SP  - 11
EP  - 11
ER  - 
@conference{
author = "Marković, Smilja and Rajić, Vladimir and Veselinović, Ljiljana and Stojković Simatović, Ivana and Belošević Čavor, Jelena and Škapin, Srečo Davor and Kovač, Janez and Nikolić, Marko G. and Uskoković, Dragan",
year = "2019",
url = "http://dais.sanu.ac.rs/123456789/6997",
abstract = "During the last decade zinc oxide (ZnO) has attracted considerable attention as a promising material for electronic, optoelectronic and spintronic devices. ZnO has a wide bandgap (3.37 eV at room temperature) and relatively large exciton binding energy (60 meV) which enables multifunctional application. Until now ZnO-based materials have been used as UV and blue light emitters, varistors, thermistors, semiconductors, photoanodes, and other. Various approaches have been applied to improve functional properties of zinc oxide, such as: fabrication of ZnO-based heterojunction particles, particles’ surface sensitization, hydrogenation, etc. It has been found that intrinsic defects (vacancies, interstitials and antisites) in the crystal structure of a ZnO strongly influenced its electrical and optical properties. Thus, correlation of the intrinsic defects concentration with optical and electrical properties of ZnO materials is of great importance for their further application in opto-electronic devices. In this study we investigated the influence of intrinsic defects concentration on the optical, electrical and photoelectrocatalytic properties of ZnO materials. To obtain ZnO powder with a high concentration of intrinsic defects microwave processing of precipitate was employed, while for further varying of defects concentration, the powder was thermally treated in three different atmospheres: air, argon and oxygen. The ZnO powder was uniaxially pressed (P = 100 MPa) in cylindrical compacts (R= 6 mm and h approx. 3 mm) which were sintered in different atmospheres by heating rate of 10 °/min up to 1100 °C, and with dwell time of 1 h. To study a crystal structure of ZnO samples XRD and Raman spectroscopy were used, while for microstructural investigation field emission scanning electron micrographs were recorded. Optical properties were studied using UV–Vis diffuse reflectance spectroscopy. To reveal the role of intrinsic defects in ZnO crystal lattice on functional properties, XPS, photoluminescence, electroluminescence and electrochemical impedance spectra were analyzed. A detailed analysis of the experimental results imply that a high concentration of intrinsic defects, in particular oxygen vacancies, is of the greatest importance for tunable light-emitting diode application and significant for the photoanode properties. To support our experimental observation we performed ab initio calculations based on density functional theory (DFT).",
publisher = "Budapest : [s. n.]",
journal = "Abstracts / International Workshop on Woman in Ceramic Science (WoCeram2019), April 7-9, 2019/ Budapest, Hungary, Novotel Danube Budapest",
title = "Tuning the optical, electrical and photoelectrocatalytic properties of Zno materials by varying of intrinsic defects concentration",
pages = "11-11"
}

Zinc oxide-based materials with enhanced sunlight-driven photo- and photo-electro-catalytic activity

Marković, Smilja; Rajić, Vladimir B.; Stojković Simatović, Ivana; Uskoković, Dragan

(Belgrade : Serbian Ceramic Society, 2017)

TY  - CONF
AU  - Marković, Smilja
AU  - Rajić, Vladimir B.
AU  - Stojković Simatović, Ivana
AU  - Uskoković, Dragan
PY  - 2017
UR  - http://dais.sanu.ac.rs/123456789/4773
AB  - Current trend in photocatalysis is to develop efficient semiconductors which can be activated by absorbing sunlight. Which wavelength of sunlight will be absorbed depends on the semiconductor band gap; semiconductors with a wide band gap (> 3 eV) can absorb only UV light (5% of sunlight), while those with a narrow band gap (< 3 eV) can be activated by visible light (45% of sunlight). Zinc oxide (ZnO) is promising semiconductor with band gap of 3.37 eV. Various approaches have been applied to modify its optical properties, for example: incorporation of different metal and nonmetal ions or defects into the crystal structure, particles’ surface sensitization or hydrogenation. In this study, we examined the influence of different defects present in ZnO particles on their photo- and photo-electro-catalytic properties. Processing of ZnO particles were carried out in order to introduce: (1) lattice defects, through microwave procedure, (2) surface defects, through mechanical activation, and (3) surface defects, trough composite with polyethylene oxide. Synthesized particles were characterized by XRD, FESEM, laser diffraction particle size analyzer, Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopy. The results of achieved photo- and photo-electro-catalytic tests indicate that both, structural and surface, defects enhanced sunlight-driven activity of ZnO particles.
PB  - Belgrade : Serbian Ceramic Society
C3  - Program and the Book of Abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VI: New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, September 18-20, 2017
T1  - Zinc oxide-based materials with enhanced sunlight-driven photo- and photo-electro-catalytic activity
SP  - 57
EP  - 57
ER  - 
@conference{
author = "Marković, Smilja and Rajić, Vladimir B. and Stojković Simatović, Ivana and Uskoković, Dragan",
year = "2017",
url = "http://dais.sanu.ac.rs/123456789/4773",
abstract = "Current trend in photocatalysis is to develop efficient semiconductors which can be activated by absorbing sunlight. Which wavelength of sunlight will be absorbed depends on the semiconductor band gap; semiconductors with a wide band gap (> 3 eV) can absorb only UV light (5% of sunlight), while those with a narrow band gap (< 3 eV) can be activated by visible light (45% of sunlight). Zinc oxide (ZnO) is promising semiconductor with band gap of 3.37 eV. Various approaches have been applied to modify its optical properties, for example: incorporation of different metal and nonmetal ions or defects into the crystal structure, particles’ surface sensitization or hydrogenation. In this study, we examined the influence of different defects present in ZnO particles on their photo- and photo-electro-catalytic properties. Processing of ZnO particles were carried out in order to introduce: (1) lattice defects, through microwave procedure, (2) surface defects, through mechanical activation, and (3) surface defects, trough composite with polyethylene oxide. Synthesized particles were characterized by XRD, FESEM, laser diffraction particle size analyzer, Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopy. The results of achieved photo- and photo-electro-catalytic tests indicate that both, structural and surface, defects enhanced sunlight-driven activity of ZnO particles.",
publisher = "Belgrade : Serbian Ceramic Society",
journal = "Program and the Book of Abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VI: New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, September 18-20, 2017",
title = "Zinc oxide-based materials with enhanced sunlight-driven photo- and photo-electro-catalytic activity",
pages = "57-57"
}

Influence of point defects concentration on optical and photocatalytic properties of ZnO ceramics

Marković, Smilja; Rajić, Vladimir B.; Veselinović, Ljiljana; Belošević Čavor, Jelena; Škapin, Srečo Davor; Stojadinović, Stevan; Rac, Vladislav; Lević, Steva; Mojović, Miloš; Uskoković, Dragan

(Belgrade : Materials Research Society of Serbia, 2016)

TY  - CONF
AU  - Marković, Smilja
AU  - Rajić, Vladimir B.
AU  - Veselinović, Ljiljana
AU  - Belošević Čavor, Jelena
AU  - Škapin, Srečo Davor
AU  - Stojadinović, Stevan
AU  - Rac, Vladislav
AU  - Lević, Steva
AU  - Mojović, Miloš
AU  - Uskoković, Dragan
PY  - 2016
UR  - http://dais.sanu.ac.rs/123456789/902
AB  - Zinc oxide is one of the most studied materials due to its wide bandgap (3.37 eV) and large exciton binding energy (60 meV) which enables application in electronics, optoelectronics and spintronics. In the forms of single crystal and thin-film ZnO are used as UV and blue light emitter, while sintered ZnO-based ceramics are important as varistors, thermistors or semiconductors. It has been found that point defects in the crystal structure of a ZnO strongly influenced its electrical and optical properties. Neutral oxygen vacancies are considered to be a major component of the defect structure of ZnO. Thus, correlation of the oxygen vacancies concentration with band gap energy of ZnO product is important to its application in optoelectronic devices. In this study we investigated the influence of point defects concentration in ZnO crystal structure on its optical and photocatalytic properties. We analyzed ZnO powders prepared by different techniques: (a) microwave processing of precipitate and (b) hydrothermal processing, which yield different ordered crystal structure. To increase a concentration of the point defects in the crystal structure, the powders were sintered in air atmosphere by heating rate of 10 °/min up to 1100 °C, with dwell time of 1 h. The crystal structure, average crystallite size and phase purity of the ZnO ceramics were determined by X-ray diffraction and Raman spectroscopy. The optical properties, in particular, absorption capacity and bang gap energy, were studied using UV–Vis diffuse reflectance spectroscopy. To reveal the role of microstructures and point defects in ZnO crystal lattice, which are receptive for luminescence and photocatalytic activity of this functional oxide, photoluminescence (PL), photoluminescence excitation (PLE) and EPR spectra were analyzed. The influence of point defects concentration in the ZnO crystal structure on photocatalytic properties was examined via decolorization of methylene blue under direct sunlight irradiation. Correlation between amount of the point defects, absorption capacity and photocatalytic efficiency were established. In order to clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.
PB  - Belgrade : Materials Research Society of Serbia
C3  - Programme and The Book of Abstracts / Eighteenth Annual Conference YUCOMAT 2016, Herceg Novi, September 5-10, 2016
T1  - Influence of point defects concentration on optical and photocatalytic properties of ZnO ceramics
SP  - 34
EP  - 34
ER  - 
@conference{
author = "Marković, Smilja and Rajić, Vladimir B. and Veselinović, Ljiljana and Belošević Čavor, Jelena and Škapin, Srečo Davor and Stojadinović, Stevan and Rac, Vladislav and Lević, Steva and Mojović, Miloš and Uskoković, Dragan",
year = "2016",
url = "http://dais.sanu.ac.rs/123456789/902",
abstract = "Zinc oxide is one of the most studied materials due to its wide bandgap (3.37 eV) and large exciton binding energy (60 meV) which enables application in electronics, optoelectronics and spintronics. In the forms of single crystal and thin-film ZnO are used as UV and blue light emitter, while sintered ZnO-based ceramics are important as varistors, thermistors or semiconductors. It has been found that point defects in the crystal structure of a ZnO strongly influenced its electrical and optical properties. Neutral oxygen vacancies are considered to be a major component of the defect structure of ZnO. Thus, correlation of the oxygen vacancies concentration with band gap energy of ZnO product is important to its application in optoelectronic devices. In this study we investigated the influence of point defects concentration in ZnO crystal structure on its optical and photocatalytic properties. We analyzed ZnO powders prepared by different techniques: (a) microwave processing of precipitate and (b) hydrothermal processing, which yield different ordered crystal structure. To increase a concentration of the point defects in the crystal structure, the powders were sintered in air atmosphere by heating rate of 10 °/min up to 1100 °C, with dwell time of 1 h. The crystal structure, average crystallite size and phase purity of the ZnO ceramics were determined by X-ray diffraction and Raman spectroscopy. The optical properties, in particular, absorption capacity and bang gap energy, were studied using UV–Vis diffuse reflectance spectroscopy. To reveal the role of microstructures and point defects in ZnO crystal lattice, which are receptive for luminescence and photocatalytic activity of this functional oxide, photoluminescence (PL), photoluminescence excitation (PLE) and EPR spectra were analyzed. The influence of point defects concentration in the ZnO crystal structure on photocatalytic properties was examined via decolorization of methylene blue under direct sunlight irradiation. Correlation between amount of the point defects, absorption capacity and photocatalytic efficiency were established. In order to clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.",
publisher = "Belgrade : Materials Research Society of Serbia",
journal = "Programme and The Book of Abstracts / Eighteenth Annual Conference YUCOMAT 2016, Herceg Novi, September 5-10, 2016",
title = "Influence of point defects concentration on optical and photocatalytic properties of ZnO ceramics",
pages = "34-34"
}

Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites

Marković, Smilja; Rajić, Vladimir B.; Stanković, Ana; Veselinović, Ljiljana; Belošević Čavor, Jelena; Batalović, Katarina; Abazović, Nadica; Škapin, Srečo Davor; Uskoković, Dragan

(Elsevier, 2016)

TY  - JOUR
AU  - Marković, Smilja
AU  - Rajić, Vladimir B.
AU  - Stanković, Ana
AU  - Veselinović, Ljiljana
AU  - Belošević Čavor, Jelena
AU  - Batalović, Katarina
AU  - Abazović, Nadica
AU  - Škapin, Srečo Davor
AU  - Uskoković, Dragan
PY  - 2016
UR  - http://dais.sanu.ac.rs/123456789/2317
AB  - ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites’ particles morphology and size distributions were studied by FE-SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. It is found that in the wavelength range 550–800 nm, ZnO and ZnO/PEO composites absorb about 50% of the incident light intensity. Also red-shift of band gap energy (0.12–0.15 eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200,000, 600,000 and 900,000 g/mol, on photocatalytic activity of ZnO/PEO composites were examined via de-colorization of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB de-colorization was found after 6 h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.
PB  - Elsevier
T2  - Solar Energy
T1  - Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites
SP  - 124
EP  - 135
VL  - 127
DO  - 10.1016/j.solener.2016.01.026
ER  - 
@article{
author = "Marković, Smilja and Rajić, Vladimir B. and Stanković, Ana and Veselinović, Ljiljana and Belošević Čavor, Jelena and Batalović, Katarina and Abazović, Nadica and Škapin, Srečo Davor and Uskoković, Dragan",
year = "2016",
url = "http://dais.sanu.ac.rs/123456789/2317",
abstract = "ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites’ particles morphology and size distributions were studied by FE-SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. It is found that in the wavelength range 550–800 nm, ZnO and ZnO/PEO composites absorb about 50% of the incident light intensity. Also red-shift of band gap energy (0.12–0.15 eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200,000, 600,000 and 900,000 g/mol, on photocatalytic activity of ZnO/PEO composites were examined via de-colorization of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB de-colorization was found after 6 h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.",
publisher = "Elsevier",
journal = "Solar Energy",
title = "Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites",
pages = "124-135",
volume = "127",
doi = "10.1016/j.solener.2016.01.026"
}
7
8
9

Synthesis and optical properties of ZnO and ZnO/PEO nanonsructured powders

Rajić, Vladimir B.; Veselinović, Ljiljana; Marković, Smilja; Uskoković, Dragan

(Belgrade : Union of Engineers and Technicians of Serbia, 2016)

TY  - JOUR
AU  - Rajić, Vladimir B.
AU  - Veselinović, Ljiljana
AU  - Marković, Smilja
AU  - Uskoković, Dragan
PY  - 2016
UR  - https://scindeks.ceon.rs/article.aspx?artid=0040-21761601009R
UR  - http://www.ncbi.nlm.nih.gov/pubmed/0040-21761601009R
UR  - http://dais.sanu.ac.rs/123456789/3359
AB  - In this paper, microwave processing of nanostructured ZnO powder as well as preparation of nanostructured ZnO/PEO composite were described. As a fast processing method which introduces a large amount of energy in the reaction system, the role of microwave processing was to modify ZnO crystal structure, while the role of PEO was to additionally sensitivize surface of ZnO particles; both of the approaches were used in the aim to improve optical properties of zinc oxide in comparison with bulk one. The synthesized powders were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence (PL). It was found that point defects (oxygen vacancies and zinc interstitials) were created in the crystal structure of zinc oxide. However, PEO has two-fold role, it passivate surface of the ZnO particles, but also introduce oxygen interstitials on the surface. The influence of the point defects on optical properties of ZnO was studied; it was found that oxygen vacancies, zinc interstitials and oxygen interstitials improved percent of thevisible light absorption, also shift band gap energy toward visible range of the spectrum.
AB  - U ovom radu opisan je postupak mikrotalasnog procesiranja nanostrukturnog praha ZnO kao i metoda pripreme nano strukturnog kompozita ZnO/PEO (PEO - polietilen oksid). Uloga mikrotalasnog procesiranja, kao brze metode koja u sistem uvodi veliku količinu energije, bila je da modifikuje kristalnu strukturu ZnO dok je uloga PEO bila da dodatno senzitivizuje površinu čestica ZnO, a sve u cilju modifikovanja (poboljšanja) standardnih optičkih osobina cink oksidnog materijala. Sintetisani prahovi su analizirani metodama rendgenske difrakcije (XRD), Ramanove spektroskopije, skanirajuće elektronske mikroskopije (FESEM), UV-Vis difuzione refleksione spektroskopije (UV-Vis DRS) i fotoluminiscencije (FL). Uočeno je da su se u kristalnoj strukturi ZnO formirali tačkasti defekti, tačnije kiseonične vakancije i intersticije cinka, dok je prisustvo PEO sa jedne strane dovelo do pasivizacije površine čestica, dok je sa druge strane došlo do formiranja kiseoničnih intersticija. Ispitan je uticaj tačkastih defekata na optičke karakteristike prahova ZnO; kiseonične vakancije, kao i intersticije cinka i kiseonika utiču kako na procenat apsorpcije vidljive svetlosti (%) tako i na pomeraj energetskog procepa (eV) ka vidljivom delu spektra
PB  - Belgrade : Union of Engineers and Technicians of Serbia
T2  - Tehnika
T1  - Synthesis and optical properties of ZnO and ZnO/PEO nanonsructured powders
T1  - Sinteza i optičke karakteristike nanostrukturnih prahova ZnO i ZnO/PEO
SP  - 9
EP  - 15
VL  - 71
IS  - 1
DO  - 10.5937/tehnika1601009R
ER  - 
@article{
author = "Rajić, Vladimir B. and Veselinović, Ljiljana and Marković, Smilja and Uskoković, Dragan",
year = "2016",
url = "https://scindeks.ceon.rs/article.aspx?artid=0040-21761601009R, http://www.ncbi.nlm.nih.gov/pubmed/0040-21761601009R, http://dais.sanu.ac.rs/123456789/3359",
abstract = "In this paper, microwave processing of nanostructured ZnO powder as well as preparation of nanostructured ZnO/PEO composite were described. As a fast processing method which introduces a large amount of energy in the reaction system, the role of microwave processing was to modify ZnO crystal structure, while the role of PEO was to additionally sensitivize surface of ZnO particles; both of the approaches were used in the aim to improve optical properties of zinc oxide in comparison with bulk one. The synthesized powders were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence (PL). It was found that point defects (oxygen vacancies and zinc interstitials) were created in the crystal structure of zinc oxide. However, PEO has two-fold role, it passivate surface of the ZnO particles, but also introduce oxygen interstitials on the surface. The influence of the point defects on optical properties of ZnO was studied; it was found that oxygen vacancies, zinc interstitials and oxygen interstitials improved percent of thevisible light absorption, also shift band gap energy toward visible range of the spectrum., U ovom radu opisan je postupak mikrotalasnog procesiranja nanostrukturnog praha ZnO kao i metoda pripreme nano strukturnog kompozita ZnO/PEO (PEO - polietilen oksid). Uloga mikrotalasnog procesiranja, kao brze metode koja u sistem uvodi veliku količinu energije, bila je da modifikuje kristalnu strukturu ZnO dok je uloga PEO bila da dodatno senzitivizuje površinu čestica ZnO, a sve u cilju modifikovanja (poboljšanja) standardnih optičkih osobina cink oksidnog materijala. Sintetisani prahovi su analizirani metodama rendgenske difrakcije (XRD), Ramanove spektroskopije, skanirajuće elektronske mikroskopije (FESEM), UV-Vis difuzione refleksione spektroskopije (UV-Vis DRS) i fotoluminiscencije (FL). Uočeno je da su se u kristalnoj strukturi ZnO formirali tačkasti defekti, tačnije kiseonične vakancije i intersticije cinka, dok je prisustvo PEO sa jedne strane dovelo do pasivizacije površine čestica, dok je sa druge strane došlo do formiranja kiseoničnih intersticija. Ispitan je uticaj tačkastih defekata na optičke karakteristike prahova ZnO; kiseonične vakancije, kao i intersticije cinka i kiseonika utiču kako na procenat apsorpcije vidljive svetlosti (%) tako i na pomeraj energetskog procepa (eV) ka vidljivom delu spektra",
publisher = "Belgrade : Union of Engineers and Technicians of Serbia",
journal = "Tehnika",
title = "Synthesis and optical properties of ZnO and ZnO/PEO nanonsructured powders, Sinteza i optičke karakteristike nanostrukturnih prahova ZnO i ZnO/PEO",
pages = "9-15",
volume = "71",
number = "1",
doi = "10.5937/tehnika1601009R"
}
1

Influence of PEO molecular weight on properties of ZnO/PEO composites

Rajić, Vladimir B.; Marković, Smilja

(Belgrade : Institute of Technical Sciences of SASA, 2015)

TY  - CONF
AU  - Rajić, Vladimir B.
AU  - Marković, Smilja
PY  - 2015
UR  - http://dais.sanu.ac.rs/123456789/838
AB  - The removal of inorganic, organic and biological pollutants from drinking water and wastewater is one of the key steps in environmental protection. In recent 10 years a heterogeneous photocatalysis, as an efficient method for the degradation and mineralization of pollutants from water, has been widely studied and developed. For heterogeneous photocatalysis mostly used materials to initiate the photoreaction are oxide semiconductors such as TiO2 and ZnO. However, these oxide semiconductors, having band gap energies around 3.3 eV, can absorb UV light only. Since sunlight is a source of clean and cheap energy, where UV light makes no more than 3–5% of the total sunlight, it is highly desirable to modify the oxide semiconductor materials to be capable for visible light photocatalysts. Numerous approaches have been applied to modify the optical absorption properties and to improve the visible light photocatalytic activity including: (1) the incorporation of transition metal ions into the crystal structure, (2) sensitization of the particles’ surface, (3) hydrogenation, (4) the incorporation of crystalline defects in metal oxide semiconductors in the form of vacancies and interstitials, etc. Microwave processing is recognized as an attractive synthesis technique to introduce lattice defects. In this study ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites' particles morphology and size distributions were studied by FE–SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. It is found that ZnO and ZnO/PEO composites absorb about 50% of visible light, also red-shift of band gap energy (0.12-0.15 eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200.000, 600.000 and 900.000 g/mol, on photocatalytic activity of ZnO/PEO composites were examined via degradation of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB degradation was found after 6 h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.
PB  - Belgrade : Institute of Technical Sciences of SASA
C3  - Program and the Book of Abstracts / Fourteenth Young Researchers' Conference Materials Sciences and Engineering, December 9-11, 2015, Belgrade, Serbia
T1  - Influence of PEO molecular weight on properties of ZnO/PEO composites
SP  - 44
EP  - 44
ER  - 
@conference{
author = "Rajić, Vladimir B. and Marković, Smilja",
year = "2015",
url = "http://dais.sanu.ac.rs/123456789/838",
abstract = "The removal of inorganic, organic and biological pollutants from drinking water and wastewater is one of the key steps in environmental protection. In recent 10 years a heterogeneous photocatalysis, as an efficient method for the degradation and mineralization of pollutants from water, has been widely studied and developed. For heterogeneous photocatalysis mostly used materials to initiate the photoreaction are oxide semiconductors such as TiO2 and ZnO. However, these oxide semiconductors, having band gap energies around 3.3 eV, can absorb UV light only. Since sunlight is a source of clean and cheap energy, where UV light makes no more than 3–5% of the total sunlight, it is highly desirable to modify the oxide semiconductor materials to be capable for visible light photocatalysts. Numerous approaches have been applied to modify the optical absorption properties and to improve the visible light photocatalytic activity including: (1) the incorporation of transition metal ions into the crystal structure, (2) sensitization of the particles’ surface, (3) hydrogenation, (4) the incorporation of crystalline defects in metal oxide semiconductors in the form of vacancies and interstitials, etc. Microwave processing is recognized as an attractive synthesis technique to introduce lattice defects. In this study ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites' particles morphology and size distributions were studied by FE–SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. It is found that ZnO and ZnO/PEO composites absorb about 50% of visible light, also red-shift of band gap energy (0.12-0.15 eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200.000, 600.000 and 900.000 g/mol, on photocatalytic activity of ZnO/PEO composites were examined via degradation of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB degradation was found after 6 h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed.",
publisher = "Belgrade : Institute of Technical Sciences of SASA",
journal = "Program and the Book of Abstracts / Fourteenth Young Researchers' Conference Materials Sciences and Engineering, December 9-11, 2015, Belgrade, Serbia",
title = "Influence of PEO molecular weight on properties of ZnO/PEO composites",
pages = "44-44"
}

Photocatalytic activity of ZnO-PEO composites

Marković, Smilja; Rajić, Vladimir B.; Stanković, Ana; Uskoković, Dragan

(Belgrade : Materials Research Society of Serbia, 2014)

TY  - CONF
AU  - Marković, Smilja
AU  - Rajić, Vladimir B.
AU  - Stanković, Ana
AU  - Uskoković, Dragan
PY  - 2014
UR  - http://dais.sanu.ac.rs/123456789/591
AB  - The removal of organic pollutants from wastewater is very important for environmental protection. During the years different methods have been developed and applied on wastewater treatment. Between those methods a heterogeneous photocatalysis has received extensive attention since it allows a complete mineralization of pollutants. ZnO-based materials has established role in heterogeneous photocatalysis. However, major drawback of ZnO is a band energy gap of 3.37 eV (368 nm) which restricts the material to absorb only UV light. Since sunlight is a source of clean and cheap energy, where UV light makes no more than 3–5% while visible light is about 45% of the total sunlight, it is highly desirable to synthesize ZnO-based materials capable for visible light photocatalysis. To modify the optical absorption properties and improving the visible light photocatalytic activity of ZnO materials several approaches have been applied: (1) metal ion doping, (2) nonmetal doping, (3) defect induced doping, (4) surface sensitization of ZnO particles to extend the spectral response into the visible region, (5) band gap modification by creation of oxygen vacancies and oxygen sub-stoichiometry, etc. In this study, ZnO powder with nanospherical morphology was synthesized by microwave processing. In the continuation, the synthesized powder was used for preparation of composites with polyethylene oxide (PEO). PEO powders with three different molecular mass (200.000, 600.000 and 900.000) were used for composites preparation. The phase purity and crystal structure of the composites were investigated by X-ray diffraction and Raman spectroscopy. The particles morphology and size distributions were studied by FE–SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of ZnO-PEO composites was examined via decomposition of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB degradation was found after 6 h of irradiation. An enhanced optical and photocatalytical properties of ZnO-PEO composites were attributed to: (1) lattice defects introduced in crystal structure of ZnO by fast microwave processing, and (2) surface sensitization by polyethylene oxide (PEO).
PB  - Belgrade : Materials Research Society of Serbia
C3  - The Sixteenth Annual Conference YUCOMAT 2014: Programme and the Book of Abstracts
T1  - Photocatalytic activity of ZnO-PEO composites
SP  - 31
EP  - 31
ER  - 
@conference{
author = "Marković, Smilja and Rajić, Vladimir B. and Stanković, Ana and Uskoković, Dragan",
year = "2014",
url = "http://dais.sanu.ac.rs/123456789/591",
abstract = "The removal of organic pollutants from wastewater is very important for environmental protection. During the years different methods have been developed and applied on wastewater treatment. Between those methods a heterogeneous photocatalysis has received extensive attention since it allows a complete mineralization of pollutants. ZnO-based materials has established role in heterogeneous photocatalysis. However, major drawback of ZnO is a band energy gap of 3.37 eV (368 nm) which restricts the material to absorb only UV light. Since sunlight is a source of clean and cheap energy, where UV light makes no more than 3–5% while visible light is about 45% of the total sunlight, it is highly desirable to synthesize ZnO-based materials capable for visible light photocatalysis. To modify the optical absorption properties and improving the visible light photocatalytic activity of ZnO materials several approaches have been applied: (1) metal ion doping, (2) nonmetal doping, (3) defect induced doping, (4) surface sensitization of ZnO particles to extend the spectral response into the visible region, (5) band gap modification by creation of oxygen vacancies and oxygen sub-stoichiometry, etc. In this study, ZnO powder with nanospherical morphology was synthesized by microwave processing. In the continuation, the synthesized powder was used for preparation of composites with polyethylene oxide (PEO). PEO powders with three different molecular mass (200.000, 600.000 and 900.000) were used for composites preparation. The phase purity and crystal structure of the composites were investigated by X-ray diffraction and Raman spectroscopy. The particles morphology and size distributions were studied by FE–SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV–Vis diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of ZnO-PEO composites was examined via decomposition of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB degradation was found after 6 h of irradiation. An enhanced optical and photocatalytical properties of ZnO-PEO composites were attributed to: (1) lattice defects introduced in crystal structure of ZnO by fast microwave processing, and (2) surface sensitization by polyethylene oxide (PEO).",
publisher = "Belgrade : Materials Research Society of Serbia",
journal = "The Sixteenth Annual Conference YUCOMAT 2014: Programme and the Book of Abstracts",
title = "Photocatalytic activity of ZnO-PEO composites",
pages = "31-31"
}