Using a spray pneumatic technique, cobalt (Co) and copper (Cu) co-doped zinc oxide thin films were effectively deposited on a glass substrate. The goal of this work was to create a semiconductor with good optical and electrical properties by co-doping ZnO thin films with Cu and Co. The ZnO thin films obtained from the Co and Cu co-doping exhibit patterns of x-ray diffraction spectra that suggest they are hexagonal ZnO (wurtzite, JCPDS 36-1451). The thin film elaborated with 2 % Co and 7 % Cu has the lowest value of crystallite size (D = 14.67 nm). The transmission spectra demonstrate that all films have good optical transparency in the visible spectrum, with 7 % Cu achieving the highest transmission. Increasing Cu contents raised the band gap energy. The value at the minimum was 3.31 eV. The optical band gap’s broadening is a significant characteristic of advanced materials and may be useful in applications involving metal oxide nanostructures for visible light gas sensing.
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ZnO is an ideal material for UV detection. However, due to the surface effect of ZnO, the photosensitivity of the ZnO based UV detector needs to be improved. In this study, we deposited a hydroxyl group functionalized (3,4-propylenethiophene) polymer (PProDOT-OH) film onto a hydrothermally grown ZnO nanoarray by electro-chemical deposition method to prevent the corrosion of ZnO by phosphotungsten acid (PWA), and then PWA was drip-coated on the composite film to prepare the ZnO/PProDOT-OH/PWA composite based UV detector. The structure and morphology of the composite were characterized by SEM, UV–vis, FT-IR, XRD, Raman, EDS, XPS analysis, illustrating the phosphotungstic acid was uniformly coated on ZnO/PProDOT-OH surface and con-firming the composite was successfully synthesized. The UV detection performance was studied through preparing a UV detector with the composite material and results indicate that the introduction of PWA could enhance the responsivity of the ZnO/PProDOT-OH composite-based UV detector.
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In a vacuum environment, when ZnO is prepared using the chemical vapor deposition method and the molecular beam epitaxial growth method, H-gap impurities inevitably remain in the ZnO system, which is often ignored. The study of Zn vacancies under experimental conditions poses a challenge. Second, as an n-type semiconductor, ZnO is characterized by a self-compensation of natural donor defects and poor stability, which severely limit the acquisition of p-type ZnO. Based on the above problems, the conductive properties of S/Se/Te doped and VZn-Hi coexisting ZnO were investigated by first principle to acquire high-stability and high-quality p-ZnO. The study found that Zn35SO35, Zn35SeO35, and Zn35SHiO35 all have good p-type conductivity, which can effectively improve hole mobility and electrical conductivity. Among them, Zn35SO35 has the largest hole concentration at 2.80×1021 cm−3, as well as the best conductivity. The choice of Zn35SO35 provides a reference for obtaining new high-quality p-type ZnO semiconductors.
The development of studies on layered double hydroxide (LDH) material as a photocatalyst for the degradation of dye pollutants continues to increase. LDH is an anionic clay, which is a natural or synthetic mixed metal hydroxide. Pristine LDH is written as M2+/M3+ LDH, (M is metal ion). This study prepared pristine Mg/Al LDH and Zn/Al LDH composited with metal oxide TiO2 and ZnO, respectively. Composite is denoted by M2+/M3+ -metal oxide. The coprecipitation method used was accompanied by calcination of the composite at a temperature 300 °C that was not high. The prepared composites were morphologically characterized by SEM. The materials that had been used until the fifth cycle of regeneration were characterized by XRD and FTIR which still indicated the presence of LDH-metal oxide composite structure. The materials degraded cationic dyes namely rhodamine-B (RhB) and methylene blue (MB). RhB degraded better than MB by pristine LDH and composites. The percent degradation of RhB for pristine Mg/Al LDH, composites Mg/Al-TiO2 and Mg/Al-ZnO were 53.1%, 59.8%, 62.8%, respectively. The percent RhB degradation for pristine Zn/Al LDH, composites Zn/Al-TiO2 and Zn/Al-ZnO were 51.4%, 58.5%, 58.9%, respectively. The percentage of degradation indicates that the LDH-metal oxide composite has succeeded in increasing the photodegradation catalytic ability and the regeneration ability of LDH pristine.
In this work, zinc oxide (ZnO) thin films are deposited on glass substrate using the sol-gel spin coating technique. The effect of annealing temperature on structural properties was investigated. The ZnO sol-gel was produced from zinc acetate dehydrate as the starting material with iso-propanol alcohol as the stabilizer. The ratio was controlled, distilled water and diethanolamine as the solvent mixing on a magnetic stirrer for an hour under constant heat of 60°C. The ZnO thin film was deposited using the spin coating technique with the speed of 3000 rpm for 30 minutes before the sample undergoes pre-heat in the oven at the temperature of 100°C for 10 minutes. The sample was annealing in the furnace for an hour at 200°C, 350°C, and 500°C. The X-ray diffraction (XRD) analysis confirms that hexagonal wurtzite structure with zincite and zinc acetate hydroxide hydrate composition. The thin films surface roughness was analyzed using an atomic force microscope (AFM) and scanning electron microscope (SEM) for surface morphology observation.
Zinc oxide (ZnO) is a prominent n-type semiconductor material used in optoelectronic devices owing to the wide bandgap and transparency. The low-temperature growth of ZnO thin films expands diverse applications, such as growth on glass and organic materials, and it is also cost effective. However, the optical and electrical properties of ZnO films grown at low temperatures may be inferior owing to their low crystallinity and impurities. In this study, ZnO thin films were prepared by atomic layer deposition on SiO2 and glass substrates in the temperature range of 46-141℃. All films had a hexagonal würtzite structure. The carrier concentration and electrical conductivity were also investigated. The low-temperature grown films showed similar carrier concentration (a few 1019 cm-3 at 141°C), but possessed lower electrical conductivity compared to high-temperature (>200°C) grown films. The optical transmittance of 20 nm thin ZnO film reached approximately 90% under visible light irradiation. Additionally, bandgap energies in the range of 3.23-3.28 eV were determined from the Tauc plot. Overall, the optical properties were comparable to those of ZnO films grown at high temperature.
The increasing growth of the textile industry does not only provide benefits in the economic sector but also has the potential to damage the environment, because it generates the dye wastewater which is hard to eliminate. Procion red is one of the synthetic textile dyes that is toxic to the aquatic environment and it needs to be processed properly. The photocatalytic method of processing dye wastewater is the most effective, because it can remove the harmful pollutants in the dye wastewater. This study aimed to prepare and characterize the ZnO-Zeolite nanocomposites for photocatalytic applications tested with a 50 mg/L procion red dye sample. The nanocomposites consisted of the ZnO semiconductors and synthetic zeolite adsorbents prepared by using the sol-gel method. The dye degradation test was carried out under the irradiation conditions with ultraviolet (UV) lamp. Apart from the ZnO-Zeolite nanocomposite, testing was also carried out with the synthetic zeolite and ZnO. The results of SEM-EDX and XRD characterization proved that the nanocomposite forming components were ZnO and zeolite and could be seen from the resulting peaks. BET showed that the surface area value of the ZnO-Zeolite nanocomposite increased to 95.98 m2/g, the pore size of the ZnO-Zeolite nanocomposite was 4.42 nm, and the total pore volume was 0.08 cm3/g. The obtained average crystalline size of ZnO-Zeolite nanocomposite was 32.87 nm. The percentage of dye degradation using the ZnO-Zeolite nanocomposite for 120 minutes has reached 90.42%.
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β-Ni(OH)2/ZnO composite powders were successfully synthesized by hydrothermal method at 180 °C for 15 h whereas NiO/ZnO composite powders formed after the as-prepared powders were calcined at 800 °C for 1 h in air. The X-ray diffractometer (XRD), scanning electron microscope (SEM), UV-Vis spectrophotometer were used to characterize the phase, particle shape as well as size and optical properties, respectively. In this system, it was found that ZnO is a major phase while β-Ni(OH)2 and NiO are a minor phases. The altered particle shape of ZnO was influenced by addition of Ni(CH3COO)2ˑ6H2O whereas the particle shape of the minor phase was changed due to the calcination process. The optical band gap decreased when the amount of minor phase increased. For photocatalytic study, it was found that 6 mol% β-Ni(OH)2/ZnO composite powders exhibited the best decolorization of methylene blue aqueous solution.
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High-power terahertz sources operating at room-temperature are promising for many applications such as explosive materials detection, non-invasive medical imaging, and high speed telecommunication. Here we report the results of a simulation study, which shows the significantly improved performance of room-temperature terahertz quantum cascade lasers (THz QCLs) based on a ZnMgO/ZnO material system employing a 2-well design scheme with variable barrier heights and a delta-doped injector well. We found that by varying and optimizing constituent layer widths and doping level of the injector well, high power performance of THz QCLs can be achieved at room temperature: optical gain and radiation frequency is varied from 108 cm−1 @ 2.18 THz to 300 cm−1 @ 4.96 THz. These results show that among II–VI compounds the ZnMgO/ZnO material system is optimally suited for high-performance room-temperature THz QCLs.
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Binary and ternary nanocomposites based on TiO2, SiO2 and ZnO were synthesized by PVA-based template-free gel combustion method. The morphology and the particles sizes of the synthesized samples depended on some parameters including the initial concentrations of metal salts and PVA amount in the sol, solvent composition and solution pH. Effects of these parameters were investigated and optimized by using the Taguchi method. In the experimental design, the Taguchi L25 array was used to investigate six factors at five levels. The samples were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) specific surface areas, scanning electron microscopy (SEM). The obtained results showed that the present method can be used to synthesize TiO2/SiO2/ZnO ternary nanocomposite with an effective surface area of 0.3 m2 · g−1 and ZnO/TiO2, TiO2/SiO2, ZnO/SiO2 binary nanocomposites with an effective surface area of 234 m2 · g-1, 6 m2 · g-1 and 0.5 m2 · g-1, respectively. The ZnO/TiO2 nanocomposite which was synthesized under the following experimental conditions: 2.5 wt.% Zn salt, 2.5 wt.% Ti salt, 2.0 wt.% PVA, pH = 1 and ethanol:water ratio 30:70 was selected by the Taguchi method as an optimum sample with the smallest particles (average diameter = 50 nm).
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In the present work, mixed structure Zn(S,O) nanoparticles have been synthesized using solution based chemical coprecipitation technique. Two different zinc sources (Zn(CH3COO) 2·2H2O and ZnSO4·7H2O) and one sulfur source (CSNH2NH2) have been used as primary chemical precursors for the synthesis of the nanoparticles in the presence and absence of a capping agent (EDTA). The structural, morphological, compositional and optical properties of the nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transmission infra-red (FT-IR) and UV-Visible (UV-Vis) spectroscopy. XRD revealed the formation of mixed phases of c-ZnS, h-ZnS and h-ZnO in the synthesized nanoparticles. The surface morphology was analyzed from SEM micrographs which showed noticeable changes due to the effect of EDTA. EDX analysis confirmed the presence of zinc, sulfur and oxygen in Zn(S,O) nanoparticles. FT-IR spectra identified the presence of characteristic absorption peaks of ZnS and ZnO along with other functional group elements. The optical band gap values were found to vary from 4.16 eV to 4.40 eV for Zn(S,O) nanoparticles which are higher in comparison to the band gap values of bulk ZnS and ZnO. These higher band gap values may be attributed to the mixed structure of Zn(S,O) nanoparticles.
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In this study, CdZnO films prepared at different ratios of dopants (CdO:ZnO = 5:5, CdO:ZnO = 6:4, and CdO:ZnO = 8:2) were coated on glass surface by using the sol-gel spin coating technique. After this process, surface structure and optical properties of the CdZnO films was investigated by atomic force microscopy (AFM) and UV-Vis spectroscopy. The surface structure of the CdZnO films depended on the content of ZnO and CdO in the films. Low percentage of CdO films were very similar to the ZnO film but higher amount of CdO resuted in granular structures together with pure structure of ZnO in the films. Eg values of produced CdZnOs depended on the additions of CdO and ZnO. The obtained Eg values of the produced CdO:ZnO = 5:5 (S3), CdO:ZnO = 6:4 (S4), and CdO:ZnO = 8:2 (S5) films are 2.5 eV, 2.49 eV, and 2.4 eV, respectively.
In this study, an attempt was made to investigate the flame retardancy of cotton fabrics coated with a high nano-ZnO content. Via a simply method in situ, a novel ZnO/cotton composite can be fabricated with a high proportion of nano-ZnO assembled on cotton fabric, where the finished cotton fabric has a certain property of flame retardancy. Discussed herein is the effect of the processed liquid concentration, ammonia-smoking time, and curing temperature on fabric properties such as flame retardancy and hand feeling. Performed were also tests of doping boric acid using the vertical burning method. The finished cotton fabrics were analysed using X-Ray Diffrcation (XRD) and a field emission scanning electron microscope(FESEM), which indicated that between the fibres, and inside the lumen and mesopores of the cotton fibres are assembled with nano-ZnO. The results show that the nano-ZnO content on cotton fabrics can reach up to 15.63 wt%, with the finished cotton fabric having excellent flame retardancy, despite the long after-glow time; however, doping with 0.8 wt% boric acid on the cotton fabric can markedly reduce this. Therefore, a high amount of nano-ZnO doped with boric acid assembled on cotton fabric has great potential in the future.
PL
W pracy podjęto próbę zbadania ognioodporności tkanin bawełnianych pokrytych nano-ZnO. Omówiono wpływ przetworzonej cieczy, stężenie, czas palenia amoniaku i temperaturę utwardzania (wulkanizacji) na właściwości tkaniny bawełnianej, takie jak: ognioodporność i chwyt. Wykonano również analizę kwasu borowego metodą pionowego spalania. Gotowe tkaniny bawełniane analizowano za pomocą dyfrakcji rentgenowskiej (XRD) i skaningowego mikroskopu elektronowego z emisją polową (FESEM), które wskazywały, że między włóknami oraz w lumenach i mezoporach włókien bawełnianych zgromadził się nano-ZnO. Wyniki pokazują, że zawartość nano-ZnO na tkaninach bawełnianych może dochodzić do 15,63% wag., Przy czym gotowa tkanina bawełniana ma doskonałą ognioodporność, pomimo długiego czasu po żarzeniu, jednak dodanie 0,8% wag. kwasu borowego może to znacznie zmniejszyć. Stwierdzono, że zastosowanie nano-ZnO z kwasem borowym na tkaninie bawełnianej ma ogromny potencjał do zastosowania w przyszłości.
Constantly developing nanotechnology provides the possibility of manufacturing nanostructured composites with a polymer matrix doped with ceramic nanoparticles, including ZnO. A specific feature of polymers, i.e. ceramic composite materials, is an amelioration in physical properties for polymer matrix and reinforcement. The aim of the paper was to produce thin fibrous composite mats, reinforced with ZnO nanoparticles and a polyvinylpyrrolidone (PVP) matrix obtained by means of the electrospinning process and then examining the influence of the strength of the reinforcement on the morphology and optical properties of the composite nanofibers. The morphology and structure of the fibrous mats was examined by a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) and Fourier-transform infrared spectroscopy (FTIR). UV –Vis spectroscopy allowed to examine the impact of zinc oxide on the optical properties of PVP/ZnO nanofibers and to investigate the width of the energy gap.
Among the large family of metallic oxides, there is a considerable group possessing excellent semiconducting properties. What follows, they are promising materials for applications in the field of optoelectronics and photonics. Thanks to the development of nanotechnology in the last few decades, it is now possible to manufacture a great variety of different nanostructures. By controlling their size, shape, composition and crystallinity, one can influence such properties as band gap, absorption properties, surface to volume ratio, conductivity, and, as a consequence, tune the material for the chosen application. The following article reviews the research conducted in the field of application of the metallic oxide nanoparticles, especially ZnO, TiO2 and ITO (Indium-Tin Oxide), in such branches of optoelectronics as solid-state lightning, photodetectors, solar-cells and transparent conducting layers.
The study presented the results of the examinations obtained during treatment of dairy wastewater in a membrane photoreactor where photocatalysis was sequentially combined with low-pressure membrane process. The aim of the study was to determine the effectiveness of degradation of the contaminants contained in such wastewater during photocatalysis and in the arrangement that combined photocatalysis with ultrafiltration. Several experiments were performed in order to determine the most beneficial conditions of the photocatalysis process, e.g. the dose of the photocatalysts used (TiO2 and ZnO), duration of the process and pH of wastewater subjected to oxidation. The dose of titanium dioxide was changed from 1 to 40 g/dm3, whereas the content of zinc oxide ranged from 1 to 6 g/dm3. The results obtained in the study showed that the extension of the irradiation time to over 30 minutes (TiO2) and over 45 minutes (ZnO) during photocatalysis does not lead to increased removal of contaminants from the dairy wastewater. It was also demonstrated that the increase in the doses of both photocatalysts does not lead to the increase in the efficiency of their treatment. In the case of treatment of dairy wastwater with TiO2, the photocatalysis occurred most effectively for its dose of 10 g/dm3. Removal rates for COD, TOC and total nitrogen were 58% (1670 mg/dm3), 62% (450 mg/dm3) and 56% (128 mg/dm3), respectively. Replacing titanium dioxide with zinc oxide (ZnO – 2 g/dm3) in the photocatalysis process allowed for obtaining higher degrees of removal of contaminants determined as COD, TOC and total nitrogen to the level of 77.8% (870 mg/dm3), 62% (445 mg/dm3) and 52% (139 mg/dm3), respectively. Since both photocatalysts were supplied to the photoreactor in the form of a suspension, the membrane in the next reactor represented an efficient barrier for their particles. It was observed that higher volumetric stream of the permeate was obtained during the process of low-pressure membrane filtration of sewage initially treated in the process of photocatalysis with titanium dioxide (4.6·10-5 m3/m2·s – TiO2 and 4.1·10-5m3/m2·s – ZnO). It was found that the ultrafiltration process in the case of the feed material with TiO2 led to the reduction in COD, TOC and total nitrogen by 78% (370 mg/dm3), 72% (126 mg/dm3) and 40% (80 mg/dm3). Slightly better quality of permeate was obtained when the feed material contained ZnO powder. Degree of retention of the contaminants COD, TOC and total nitrogen were 68% (280 mg/dm3), 66% (143 mg/dm3) and 42% (76 mg/dm3), respectively.
PL
W pracy zaprezentowano wyniki badań jakie otrzymano podczas oczyszczania ścieków mleczarskich w fotoreaktorze membranowy w którym sekwencyjnie skojarzono procesy fotokatalizę z niskociśnieniowym procesem membranowymi. Celem badań było określenie skuteczności degradacji zanieczyszczeń znajdujących się w tego rodzaju wodach odpadowych w samodzielnie prowadzonym procesie fotokatalizy jak również w układzie kojarzącym go z procesem ultrafiltracji. Przeprowadzono szereg eksperymentów w celu ustalenia najkorzystniejszych warunków prowadzenia procesu fotokatalizy tj. dawka zastosowanych fotokatalizatorów (TiO2 i ZnO), czas prowadzenia procesu oraz wartość pH ścieków poddawanych utlenianiu. Dawkę ditlenku tytanu zmieniano w zakresie od 1 do 40 g/dm3 a tlenku cynku od 1 do 6 g/dm3. Na podstawie uzyskanych wyników badań stwierdzono, że wydłużanie czasu naświetlania powyżej 30 minut (TiO2) oraz powyżej 45 min (ZnO) w procesie fotokatalizy nie wpływa na zwiększanie usunięcia zanieczyszczeń z oczyszczanych ścieków mleczarskich. Wykazano również, że zwiększanie stosowanych dawek obu fotokatalizatorów nie skutkuje wzrostu efektywności ich oczyszczania. W przypadku oczyszczania ścieków mleczarskich z TiO2 proces fotokatalizy przebiegał najkorzystniej jego dawce wynoszącej 10 g/dm3. Stopień usunięcia ChZT, OWO i azotu ogólnego wynosił odpowiednio 58% (1670 mg/dm3), 62% (450 mg/dm3) i 56% (128 mg/dm3). Zastąpienie ditlenku tytanu tlenkiem cynku (ZnO – 2g/dm3) w procesie fotokatalizy pozwoliło na uzyskanie wyższych stopni usunięcia zanieczyszczeń oznaczanych jako ChZT, OWO i azotu ogólnego odpowiednio do poziomu 77.8% (870 mg/dm3), 62% (445 mg/dm3) i 52% (139 mg/dm3). Z uwagi na fakt, że oba dawkowano do fotoreaktora w formie zawiesiny to znajdująca się w kolejnym reaktorze membrana była skuteczną barierę dla ich cząstek. Zaobserwowano, że wyższy objętościowy strumień permeatu uzyskano w trakcie prowadzenia procesu niskociśnieniowej filtracji membranowej ścieków wstępnie podczyszczonych w procesie fotokatalizy z ditlenkiem tytanu (4,6·10-5 m3/m2·s – TiO2 i 4,1·10-5 m3/m2·s – ZnO). Stwierdzono że wykorzystany proces ultrafiltracji w przypadku nadawy z TiO2 przyczynił się do obniżenia wartości wskaźników ChZT, OWO i azotu ogólnego odpowiednio o 78% (370 mg/dm3), 72 % (126 mg/dm3) i 40% (80 mg/dm3). Nieznacznie lepszej jakości permeat otrzymano, gdy nadawa zawierała proszek ZnO. Stopień retencji zanieczyszczeń ChZT, OWO i azotu ogólnego wynosił odpowiednio 68% (280 mg/dm3), 66 % (143 mg/dm3) i 42% (76 mg/dm3).
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In this article, ZnO thin-film deposition on a glass substrate was done using microwave induced oxygen plasma based CVD system. The prepared thin-films were tested in terms of crystallinity and optical properties by varying the microwave power. The effect of power variation on the morphology and size of final products was carefully investigated. The crystal structure, chemical composition and morphology of the final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and photoluminescence (PL). This technique confirmed the presence of hexagonal ZnO nanocrystals in all the thin-films. The minimum crystallite grain size as obtained from the XRD measurements was ~9.7 nm and the average diameter was ~18 nm.
This paper presents research results of zinc oxide thin films deposited on a glass substrate with use of ALD method. Our researches focused on analyzing of the influence of ALD deposition process temperature on the morphology and transparency of thin layers. The morphology was examined using both scanning and transmission electron microscopes. Transparency study was performed by UV-VIS spectroscopy. For our experiments, two sets of the coating have been prepared, differing in temperature and number of cycle used during the preparation process. The first set was deposited in 100 cycles, second one in 500 cycles. Each set of tested coating contained samples prepared at different temperatures.
Efektywność rozkładu zanieczyszczeń organicznych w procesie fotokatalizy zależy od szeregu czynników, wśród których decydującą rolę odgrywają zarówno, dobór rodzaju, jak i dawki fotokatalizatora. Do najczęściej opisywanych w literaturze półprzewodników stosowanych w procesach oczyszczania strumieni wodnych zalicza się tlenek tytanu(IV) i tlenek cynku. W pracy przedstawiono zmiany toksyczności wodnych mieszanin fotokatalizatorów bez i w trakcie ich naświetlania promieniami UV o długości fali przekraczającej 300 nm. Badania prowadzono z użyciem czterech półprzewodników, tj. TiO2 jako mieszaniny anatazu i rutylu, TiO2 w postaci czystego anatazu, ZnO oraz ZnO farmaceutycznego w dawce 25, 50, 100 i 200 mg/dm3. Efekt toksyczny oceniono z użyciem biotestu Microtox®. Wykazano, że wraz ze wzrostem czasu napromieniowania mieszaniny ZnO oraz ZnO farmaceutycznego wzrasta odpowiedź toksykologiczna organizmów testowych. Świadczy to o braku stabilności fotochemicznej obu tych półprzewodników oraz dyskwalifikuje ich użycie w przypadku oczyszczania strumieni wodnych odprowadzanych do środowiska naturalnego. Zmiany efektu toksykologicznego nie obserwowano w przypadku mieszanin wodnych z półprzewodnikami, które nie były naświetlane promieniami UV. Również naświetlanie mieszanin zawierających TiO2 bez względu na formę nie wpłynęło na zmianę ich toksyczności.
EN
The efficiency of decomposition of organic pollutants during photocatalytic oxidation process depends on several factors, among which the type and dose of photocatalyst plays a significant role. According to literature, the most commonly used semiconductors in processes of water streams treatment are titanium dioxide and zinc oxide. The paper presents the change in toxicity of aqueous mixtures of photocatalysts unirradiated and irradiated with UV light with wavelength greater than 300 nm. Studies were carried out by the use of four semiconductor i.e. TiO2 as a mixture of anatase and rutile, TiO2 as a pure form of anatase, ZnO and pharmaceutical ZnO at a dose of 25, 50, 100 and 200 mg/dm3. Toxic effects were evaluated using the Microtox® bioassay. It has been demonstrated that the toxic response of the test organisms increases with the increase of the irradiation time of mixtures containing ZnO and ZnO pharmaceutical. That fact indicates a lack of photochemical stability of both semiconductors and disqualifies their use during the treatment of water streams which will be discharged into the environment. Changes in toxicological effects were not observed for semiconductors water mixtures, which were not irradiated with UV light. Also, the UV exposure of mixtures containing TiO2 did not affect any change of their toxicity.
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