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1.
《Ceramics International》2021,47(19):27469-27478
ZnO nanostructures are well-known photocatalysts for the degradation of toxic organic dyes and their morphology, size, and other physicochemical properties play important roles in their photocatalytic performance. To study the effect of size, morphology, and synthesis conditions in photocatalytic performance, we synthesized ZnO nanoparticles of different morphologies through a simple microwave-assisted chemical process at different pH values of the reaction mixture. Different pH values of the reaction mixture produced ZnO nanoparticles of different morphologies and sizes. The nature of the pH controlling agent and final pH of the reaction mixture were seen to have considerable effects on the lattice parameters and microstrain of the ZnO nanocrystals, along with their photocatalytic performance. We observed that while the ZnO nanostructures synthesized at very high pH values of the reaction mixture have a high specific surface area, their photocatalytic activity is higher when they are synthesized at acidic pH or pH near the isoelectric point of ZnO. The results demonstrate that the photocatalytic activity of ZnO nanostructures not only depends on their size or specific surface area but also strongly depends on the concentration of catalytic sites at their surface. 相似文献
2.
Effect of Cl?1 concentration on morphology and optical properties of Cl-doped ZnO nanostructures was studied. The Cl-doped ZnO nanostructures and undoped ZnO microstructures were grown on Si(1 1 1) substrates using a physical vapor deposition method. The ZnO nanostructures have been doped with different concentrations of chlorine. The Cl-doped ZnO nanostructures with 6% atom Cl, showed a nanodisk morphology with a hexagonal shape, while the Cl-doped ZnO nanostructures with 9% atom Cl, exhibited a stacked nanoplate morphology with smaller thickness in comparison to the Cl-doped ZnO nanodisks. In addition, with increasing Cl content to 13%, morphology of the products changed to more stacked nanoplates with nanoflakes morphology. X-ray diffraction results clearly showed a hexagonal structure for the all samples. Raman spectroscopy results showed a strong crystalline quality for the undoped ZnO microdisks and Cl-doped ZnO nanodisks; while these results indicated a weak crystalline quality for the Cl-doped ZnO nanoplates and nanoflakes. Photoluminescence (PL) studies also confirmed the Raman results and it exhibited a lower optical property for the Cl-doped ZnO nanoplates and nanoflakes in comparison to the undoped ZnO microdisks and Cl-doped ZnO nanodisks. Furthermore, the UV peak of the Cl-doped ZnO nanostructures was blue-shifted with respect to that of the undoped ZnO. 相似文献
3.
Zinc oxide (ZnO) nanostructures of various morphologies were prepared using a microwave-assisted aqueous solution method. Herein, a comparative study between three different morphologies of ZnO nanostructures, namely nanoparticles (NPs), nanoflowers (NFs) and nanorods (NRs) has been reviewed and presented. The morphologies of the prepared powders have been studied using field effect scanning electron microscopy (FESEM). X-ray diffraction (XRD) results prove that ZnO nanorods have biggest crystallite size compared with nanoflowers and nanoparticles. The texture coefficient (Tc) of three morphologies has been calculated. The Tc changed with varying morphology. A comparative study of surfaces of NPs, NFs and NRs were investigated using X-ray photoelectron spectroscopy (XPS). The possible growth mechanisms of ZnO NPs, NFs and NRs have been described. The optical properties of the ZnO nanostructures of various morphologies have been investigated and showed that the biggest crystallite size of ZnO nanostructures has lowest band gap energy. The obtained results are in agreement with experimental and theoretical data of other researchers. 相似文献
4.
《Ceramics International》2017,43(11):8289-8293
In this work, zinc oxide (ZnO) nanostructures were successfully synthesized by thermal oxidation of zinc (Zn) coated steel substrates. Zn coatings were electrodeposited on the mild carbon steel sheet in the sulfate bath by DC current. The zinc coated samples were oxidized in air at distinct annealing temperatures between 400 °C and 800 °C. The phase structure and surface morphology of the ZnO films were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of these ZnO layers was examined by means of decomposition of methylene blue (MB) aqueous solutions under UV lamp irradiation for various duration. The findings illustrated that annealing temperatures had a big effect on the morphology and structure of the ZnO layers. The annealed layers showed significantly enhanced photoactivity activity than the pure Zn layer under UV-irradiation. The sample with ZnO nanostructures oxidized at 800 °C exhibited a better photocatalytic degradation of MB than the other samples. This paper can provide an important contribution to the development of efficient photocatalysts for the solution of the environmental pollution problems. 相似文献
5.
ZnO nanopowders were synthesized by hydrothermal and solvothermal method by using CTAB as surfactant, and the effects of CTAB on the morphologies of ZnO nanopowders were investigated. The results showed that the presence of CTAB could greatly vary the shape of the ZnO crystals. ZnO nanorods were prepared from the hydrothermal system without CTAB and flowers-like ZnO nanostructures were produced from hydrothermal system with 0.4 M and 0.5 M CTAB. Low concentration of CTAB in ethanol was conducive to the formation of ZnO nanorods, but the concentration continued to increase, the morphology of sample transformed into hexagonal bipyramid, and then transformed into spherical. The synthesis mechanism of ZnO powders with different morphologies has been presented. 相似文献
6.
Shaolin Zhang Son T. Nguyen Thuy H. Nguyen Woochul Yang Jin‐Seo Noh 《Journal of the American Ceramic Society》2017,100(12):5629-5637
Despite the great potential of zinc oxide (ZnO) nanostructures as a sensing material for high‐performance gas sensors, the correlation between the morphology of ZnO nanostructure and its gas‐sensing performance has not been systematically investigated yet. In this work, ZnO nanostructures with controlled morphologies were synthesized by low‐temperature solution route and chemical bath deposition method. Thin film gas sensors were fabricated from the nanostructures and the sensor performance such as the response, recovery time, and stability was examined for several gases. It is demonstrated that the gas‐sensing performance of a ZnO nanostructure sensor is strongly influenced by its morphology. One dimensional ZnO nanocones are highly promising for practical application to gas sensors, due to their large surface area per unit mass and unique conical structure. 相似文献
7.
8.
The ZnO nanowire/multi-walled carbon nanotube (MWNT) nanocomposites have been successfully synthesized by one-step hydrothermal method using zinc chloride as Zn source. Their photocatalytic degradation performances on methylene blue and Rhodamine 6G have been investigated under UV irradiation. Experimental results show that the photocatalytic efficiency of the as-synthesized ZnO/MWNT nanocomposites is 3 times higher than that of pure ZnO nanowires. The enhanced photocatalytic activity is attributed to the fast transfer of photo-generated electrons from ZnO to MWNTs, leading to low recombination rate of photo-induced electron–hole pairs. 相似文献
9.
In this study, zinc oxide (ZnO) nanocrystals with different morphologies were synthesized and used as substrates for enzyme immobilization. The effects of morphology of ZnO nanocrystals on enzyme immobilization and their catalytic activities were investigated. The ZnO nanocrystals were prepared through a hydrothermal procedure using tetramethylammonium hydroxide as a mineralizing agent. The control on the morphology of ZnO nanocrystals was achieved by varying the ratio of CH3OH to H2O, which were used as solvents in the hydrothermal reaction system. The surface of as-prepared ZnO nanoparticles was functionalized with amino groups using 3-aminopropyltriethoxysilane and tetraethyl orthosilicate, and the amino groups on the surface were identified and calculated by FT-IR and the Kaiser assay. Horseradish peroxidase was immobilized on as-modified ZnO nanostructures with glutaraldehyde as a crosslinker. The results showed that three-dimensional nanomultipod is more appropriate for the immobilization of enzyme used further in catalytic reaction. 相似文献
10.
Parag V. Adhyapak Satish P. Meshram Vijaykumar TomarDinesh P. Amalnerkar Imtiaz S. Mulla 《Ceramics International》2013
Hierarchical zinc oxide nanostructures were successfully synthesized by facile hydrothermal and sonochemical routes using citrate and PEG as structure directing agents. The effect of precursor concentration and preparation methods on the formation of typical morphology was systematically studied under hydrothermal and sonochemical conditions. Different concentrations of zinc acetate, sodium citrate and NaOH under hydrothermal and sonochemical methods generate different hierarchical structures such as flower-like, cabbage-like, and ellipsoidal ball-like morphologies, depending on the preparation conditions. The as-prepared ZnO samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission election microscopy (TEM), photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and particle size distribution (PSD) analysis. Catalytic activities of the as-prepared samples were studied by photodegradation of Methylene blue. 相似文献
11.
Farid Jamali-Sheini Ramin Yousefi M.R. Mahmoudian Nabeel Ali Bakr Abdolhossein Sa΄aedi Nay Ming Huang 《Ceramics International》2014
Te-doped ZnO nanostructures were synthesized by an annealing (vapor–solid) process under ambient conditions, and characterized in terms of their morphological, structural, compositional and optical properties. The structural and morphological characterizations revealed that the synthesized nanostructures were well-defined multipods, needles and spherical particles, and possessed well-crystalline ZnO wurtzite hexagonal phase. Also, in the X-ray diffraction studies, the presence of a shift in the peak positions towards a lower angle, and a decrease in the intensity, with an increase in the Te concentration, as compared to the undoped ZnO, were observed. The chemical composition confirmed the presence of Te, in the case of multipod and needle morphologies. The effect of doping on the crystalline quality and optical properties was also investigated, by using photoluminescence (PL) and Raman spectrometers. The Raman results demonstrated that the doped ZnO nanostructures had a lower crystalline quality than the undoped ZnO. Moreover, the PL results showed a decrease in the band gap for the doped ZnO nanostructures, in comparison to the undoped ZnO. A possible growth mechanism was also proposed. 相似文献
12.
《Dyes and Pigments》2013,96(3):443-449
Single crystalline ZnO with hexagonal cylinder-like bipods morphologies were successfully synthesized via a cationic surfactant-assisted hydrothermal microemulsion route. The structure, morphologies and properties of the as-prepared samples were determined using X-ray diffraction, scanning electron microscopy, photoluminescence spectrum and Ultraviolet and Visible absorption spectroscopy. The photocatalytic activities of the obtained products were evaluated by the degradation of Reactive Brilliant Red K-2BP in aqueous solution under a variety of conditions. Under the optimum condition, approximately 99.5% decolorization efficiency within 45 min and 65.3% TOC removal efficiency within 3 h were achieved, which were higher than that by the commercial ZnO. Moreover, the degradation products were analyzed by a gas chromatography coupled with mass spectrometry system and the probable pathways for the formation of the intermediates were proposed. The photocatalytic results indicated that the as-prepared ZnO showed good photocatalytic activity and it could be considered as a promising photocatalyst for dyes wastewater treatment. 相似文献
13.
Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO. 相似文献
14.
铅笔状ZnO生长机理的研究及光催化性能表征 总被引:1,自引:0,他引:1
用水热法于175℃合成了铅笔状ZnO。并通过XRD、EDS、SEM、TEM和HRTEM对不同碱性条件下合成的ZnO的形貌进行了分析,结果表明,n(OH-)∶n(Zn2+)=4∶1时,ZnO的形貌为平均厚度90nm的片状结构;当n(OH-)∶n(Zn2+)=10∶1时,ZnO的形貌为直径200nm、长度2.5μm的铅笔状结构。探讨了不同形貌的ZnO的形成机理。用UV-vis吸收光谱和PL光谱分析了ZnO的形貌对次甲基蓝光催化降解的影响,结果发现,铅笔状氧化锌的光催化性能优于片状氧化锌。 相似文献
15.
The study of the mechanisms of formation and growth of ZnO nanostructures is crucial as they have the potential to find applications in opto-electronic devices. ZnO nanostructures of different morphologies have been synthesized using a low-temperature polymeric precursor process. Controlling the Zn cation and nitric acid concentrations, flower-like morphology of the ZnO nanostructures could be synthesized with excellent reproducibility. Besides chemistry, the effects of spin-coating variables on morphology were also investigated. The results show that the morphology of the flowers is controlled by Zn2+ ion concentration, whereas spin speed and film thickness are responsible for the size variations. All obtained ZnO structures reveal a polycrystalline hexagonal wurtzite structure and strong UV photoluminescence along with lattice defects. Polar surfaces of ZnO promoting multilayer Volmer–Weber growth play a crucial role in the development of these flower-like structures. Possible mechanisms for variations of morphology with synthesis parameters are discussed. 相似文献
16.
以二水醋酸锌和六次甲基四胺为原料,采用温和水热法制备了六方柱状ZnO。采用X射线衍射(XRD)、扫描电镜(SEM)和紫外可见光谱对其物相、形貌和光催化性能进行了分析,着重研究了不同的反应条件对ZnO形貌的影响,探讨了六方柱状ZnO的形成机理。结果表明:溶液浓度、pH值、反应温度和反应时间对生成晶体的形貌和晶体质量都会产生影响。制备结晶良好的ZnO的最佳反应条件为:反应液浓度为0.57mol/L,pH值为6.0,反应温度为97℃,反应时间为16h。六方柱状ZnO晶体的形成机理是在一定的水热条件下,醋酸锌与六次甲基四胺水解后形成晶核,由于(0001)晶面的生长速率大于其它晶面,以及(0001)晶面易俘获原子,使得成核后的ZnO沿(0001)面定向生长,最终形成六方柱状结构。 相似文献
17.
采用浊度法绘制十六烷基三甲基溴化铵(CTAB)/正丁醇/环己烷/硝酸锌或草酸铵水溶液体系的拟三元相图,确定微乳液稳定区域最大时CTAB与正丁醇的质量比为1∶1。在此条件下,选择m(CTAB+正丁醇)∶m(环己烷)=3∶7,以硝酸锌和草酸铵为原料,采用微乳法制备ZnO的前驱体二水合草酸锌,然后通过煅烧得到ZnO样品。考察水与CTAB的摩尔比(R)和反应物浓度对ZnO材料结构、形貌、光学性质和光催化性能的影响。实验结果表明:ZnO样品为纯的六方纤锌矿结构晶体,形貌均为棒状,且样品的尺寸随R值和反应物浓度的不同而不同。在300 W汞灯紫外光照射下,ZnO样品对亚甲基蓝溶液均具有较好的光催化性能,光催化反应过程符合准一级反应动力学。其中,在反应物浓度为0.15 mol/L,R=15条件下制备的ZnO样品在光照90 min时可使亚甲基蓝的降解率达到97.0%,且降解反应速率常数k最大,其光催化性能最好。 相似文献
18.
Mohammad Taghi Hosseinnejad Marzieh Shirazi Mahmood Ghoranneviss Mohammad Reza Hantehzadeh Elham Darabi 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(2):405-412
ZnO is one of the most promising transparent conducting oxide materials, which widely used in thin film gas sensors. In this research, the dependence of the thermal oxidation time on structural, morphological and gas sensing properties of ZnO thin films is investigated. ZnO nanostructures are synthesized by using DC magnetron sputtering for deposition of pure zinc layers on glass substrates and then thermal oxidation of deposited zinc layers to produce zinc oxide (ZnO) thin films. Obtained results from X-ray diffraction revealed that the degree of crystallinity and the average grain size of the ZnO deposited thin films enhance with increasing the thermal oxidation time. Surface topography and growth behavior of ZnO thin films have important role in optimization of gas sensing properties of these films. In this study, scanning electron microscopy and atomic force microscopy have been used to investigate the effective parameters related to the surface topography of the films. Obtained results from these analyzes revealed that the surface topography of ZnO deposited samples strongly depend on thermal oxidation time. Also the effect of thermal oxidation time on the performance of ZnO gas sensors is investigated. The results indicated that the ethanol gas sensing properties of ZnO samples improve with decreasing the size of grains. 相似文献
19.
《Ceramics International》2016,42(3):3820-3825
Environmentally benign procedure for synthesis symmetrical imidazolium based ionic liquids has been achieved. These Ionic liquids dissolved in water have been used as a reaction medium for synthesis of different morphologies of ZnO nanostructures like nanocoral, spherical and nanosheet by reflux method. The structural and optical properties of these ZnO particles were studied by using XRD, SEM and UV–visible. The characteristic results revealed that the anion and cation of ionic liquids effect on band gap and morphology of the zinc oxide species. The results show that the longer alkyl chain at positions 1 and 3 of imidazole ring ionic liquid cause the nanosheet morphology. 相似文献
20.
We report the synthesis of porous ZnO-ZnSe nanocomposites for use in visible light photocatalysis. Porous ZnO nanostructures were synthesized by a microwave-assisted hydrothermal reaction then converted into porous ZnO-ZnSe nanocomposites by a microwave-assisted dissolution-recrystallization process using an aqueous solution containing selenium ions. ZnO and ZnSe nanocrystallites of the nanocomposites were well-mixed (rather than forming simple core-shell (ZnO-ZnSe) structures), particularly, in the outer regions. Both ZnO and ZnSe were present at the surface and exposed to the environment. The porous ZnO-ZnSe nanocomposites showed absorption bands in the visible region as well as in the UV region. The porous ZnO-ZnSe nanocomposites had much higher activities than the porous ZnO nanostructures. Control experiments using cutoff filters revealed that the main photocatalytic activity of the synthesized nanostructures arose from photo-excitation of the semiconductor (ZnO or ZnSe) via absorption of light of an energy equal to or exceeding the band gap energy. 相似文献