Paederia foetida Linn. promoted synthesis of CoFe2 O4 and NiFe2 O4 nanostructures and their photocatalytic efficiency

A facile method of synthesis of cobalt ferrite (CoFe₂ O₄) and nickel ferrite (NiFe₂ O₄) nanoparticles (NPs) was developed using urea as a hydroxylating agent and Paederia foetida Linn. (family: Rubiaceae) leaf extract as a bio‐template. The synthesised ferrite NPs were characterised in a detailed manner by powder X‐ray diffraction (XRD), transmission electron microscopy, Fourier transform‐infrared spectroscopy and vibrating sample magnetometer analysis. The XRD patterns revealed the formation of cubic face‐centred phase for both CoFe₂ O₄ and NiFe₂ O₄ NPs. These quasi‐spherical particles of CoFe₂ O₄ and NiFe₂ O₄ were shown to have sizes in the range of 10–80 and 5–50 nm, respectively. The photocatalytic activity of metal ferrites was evaluated in H₂ O₂ assisted oxidative degradation of methylene blue (MB) and rhodamine B (RhB) under irradiation of solar light. Both metal ferrite photocatalysts exhibited pronounced activity in degradation of MB and RhB, respectively, but relatively higher activity was observed for NiFe₂ O₄. After completion, the catalysts were recovered using an external magnet. Recycling of these recovered catalysts up to five times showed no noticeable change in the efficiency.Inspec keywords: nanoparticles, nanofabrication, photochemistry, catalysts, cobalt compounds, nickel compounds, ferrites, X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectra, crystal structure, dyesOther keywords: Paederia foetida Linn, nanostructures, photocatalytic efficiency, cobalt ferrite nanoparticles, nickel ferrite nanoparticles, hydroxylating agent, leaf extract, bio‐template, powder X‐ray diffraction, transmission electron microscopy, Fourier transform‐infrared spectroscopy, vibrating sample magnetometer analysis, cubic face‐centred phase, quasi‐spherical particles, photocatalytic activity, methylene blue, rhodamine B, size 5 nm to 80 nm, CoFe₂ O₄ , NiFe₂ O₄      

片状磁性纳米TiO2/SiO2/NiFe2O4制备及光催化性能

以锐钛矿磁性纳米TiO2/SiO2/NiFe2O4(TSN)为原料,采用水热法制备了片状磁性纳米TSN.利用XRD、TEM等技术对样品进行了表征.水热法处理后核壳结构的TSN部分转变为片状,催化剂磁性增强.以亚甲基兰溶液为模拟水样测试了样品的光催化性能,考察了催化剂加入量、反应时间、pH值等因素的影响.实验表明:片状磁性纳米TSN光催化性能明显优于粒状TSN.片状TSN具有良好的吸附性能,提高了光催化反应的初始速率.用于处理亚甲基兰废水时受pH值的影响较小,1小时的脱色率在90%以上.     

Ag/AgCl纳米枝状结构的制备及其光催化性能研究

采用离子液体法,以离子液体(DESs)为溶剂,柠檬酸三钠为还原剂,氯金酸为晶种,硝酸银为银源,制备了Ag/AgCl纳米枝状结构。利用SEM、XRD、EDS对样品的形貌、成分、结构进行了表征分析,并测试了样品的光催化性能。结果表明,当反应温度为160℃,反应时间为24h时,可获得完整的Ag/AgCl纳米枝状结构;枝状结构的形成是基于AgCl在还原剂作用下不断向Ag转换过程的结果;产物具有较好的光催化效果,并且随着反应时间的延长,产物的光催化性能减弱。     

合成和表征NiFe2O4纳米线阵列

采用真空灌注结合溶胶-凝胶和氧化铝模板法,在多孔氧化铝模板中制备了平均直径为50 nm的NiFe2O4纳米线阵列.X射线衍射结果显示所制备的纳米线是纯相的NiFe2O4纳米线,透射电镜和电子衍射的结果显示已制备的纳米线是多晶的且表面光滑,场发射扫描电镜图片显示纳米线是大面积且平行有序的、纳米线的长度和所用的氧化铝模板的厚度相当.磁测量的结果显示此纳米线阵列有形状各向异性,同块状材料相比矫顽力有所增强.对纳米线的生长机理做了简单的讨论.     

Synthesis of polyaniline-modified Fe3O4/SiO2/TiO2 composite microspheres and their photocatalytic application

Polyaniline-modified Fe₃O₄/SiO₂/TiO₂ composite microspheres have been successfully synthesized by sol–gel reactions on Fe₃O₄ microspheres followed by the chemical oxidative polymerization of aniline. The synthesized multilayer-structured composites were characterized by TEM, XRD, TGA, UV–vis diffuse reflectance spectra and magnetometer. The photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light. The effect of polyaniline (PANI) amounts on the photocatalytic activity was investigated. The photocatalytic activity results show that the Fe₃O₄/SiO₂/TiO₂ composites with about 2.4 wt.%–4.1 wt.% PANI could show higher photocatalytic efficiency than that of Fe₃O₄/SiO₂/TiO₂. Furthermore, the PANI-Fe₃O₄/SiO₂/TiO₂ photocatalyst could be easily recovered using a magnet.     

Synthesis and photocatalytic properties of TiO2 nanostructures

TiO₂ particles, rods, flowers and sheets were prepared by hydrothermal method via adjusting the temperature, the pressure and the concentration of TiCl₄. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and N₂ adsorption–desorption measurements. It was found that pressure is the most important factor influencing the morphology of TiO₂. The photocatalytic activity of the products was evaluated by the photodegradation of aqueous brilliant red X-3B solution under UV light. Among the as-prepared nanostructures, the flower-like TiO₂ exhibited the highest photocatalytic activity.     

NiFe2O4-BiFeO3纳米管的制备与磁电特性研究

采用溶胶-凝胶法在多孔氧化铝模板的纳米孔洞中成功地合成了xNiFe₂O₄-(1-x) BiFeO₃ (NFO-BFO)复合纳米管阵列。扫描电镜照片显示纳米管的外径约为70 nm, 内径约为50 nm, 长度约为80 μm。X射线衍射图谱显示, 通过自组装形成了钙钛矿结构的铁电相BFO和尖晶石结构的铁磁相NFO。磁性和铁电性的测试结果表明, 复合纳米管具有明显的室温铁磁性和电极化性能, 且易磁化方向沿着纳米管的长轴方向。随着NFO复合比例的增加, 纳米管阵列的磁性和电极化性能逐渐增强。NFO对复合纳米管阵列铁磁贡献的计算结果表明, NFO-BFO纳米管阵列中存在着磁电耦合效应。     

Synthesis of titanate nanostructures using amorphous precursor material and their adsorption/photocatalytic properties

This article reports on a new and swift hydrothermal chemical route to prepare titanate nanostructures (TNS) avoiding the use of crystalline TiO₂ as starting material. The synthesis approach uses a commercial solution of TiCl₃ as titanium source to prepare an amorphous precursor, circumventing the use of hazardous chemical compounds. The influence of the reaction temperature and dwell autoclave time on the structure and morphology of the synthesised materials was studied. Homogeneous titanate nanotubes with a high length/diameter aspect ratio were synthesised at 160 °C and 24 h. A band gap of 3.06 ± 0.03 eV was determined for the TNS samples prepared in these experimental conditions. This value is red shifted by 0.14 eV compared to the band gap value usually reported for the TiO₂ anatase. Moreover, such samples show better adsorption capacity and photocatalytic performance on the dye rhodamine 6G (R6G) photodegradation process than TiO₂ nanoparticles. A 98% reduction of the R6G concentration was achieved after 45 min of irradiation of a 10 ppm dye aqueous solution and 1 g L⁻¹ of TNS catalyst.     

Rapid Synthesis of Nanocrystalline NiFe2O4 and CoFe2O4 Powders by a Microwave-Assisted Combustion Method

A facile and rapid microwave-assisted combustion method was applied to synthesize the nanocrystalline NiFe₂O₄ and CoFe₂O₄ powders. The results suggested that application of microwave heating to synthesize the homogeneous porous NiFe₂O₄ and CoFe₂O₄ powders was achieved in a few minutes. The structure and morphology of the as-prepared nanocrystalline powders of NiFe₂O₄ and CoFe₂O₄ were investigated by means of X-ray diffraction (XRD) and tunneling electron microscopy (TEM). The XRD spectra confirmed the formation of spinel structure with a crystallite size of 30.03 nm for NiFe₂O₄ and 36.7 nm for CoFe₂O₄ nanopowders, and TEM results indicated spherical shape of the products. Magnetic measurements revealed that at room temperature while NiFe₂O₄ is superparamagnetic, CoFe₂O₄ shows ferromagnetic behavior.     

聚苯乙烯-SiO2/NiFe2O4磁性微球的制备与表征

以NiFe2O4纳米粒子作磁性载体、苯乙烯(ST)、正硅酸乙酯(TEOS)为原料,KH-570为交联剂,采用乳液聚合法制备了聚苯乙烯-SiO2/NiFe2O4磁性微球材料。通过VSM、FT-IR、SEM、TG-DTA、溶剂抽提等方法对磁性微球材料进行了测试。制备的NiFe2O4粒子为面心立方结构,NiFe2O4纳米颗粒及聚苯乙烯-SiO2/NiFe2O4磁性微球具有超顺磁性。聚苯乙烯-SiO2/NiFe2O4磁性微球以SiO2/NiFe2O4为核、PS为壳,通过KH-570接枝到SiO2/NiFe2O4上,核壳间以共价键相接的包覆型纳米粒子,平均直径为100nm左右,具有良好的热稳定性和耐溶剂性能。热重(TG)分析表明,磁性聚苯乙烯微球磁性物质质量分数为28.8%。     

纳米增韧NiFe2O4陶瓷惰性阳极烧结行为与性能的研究

采用粉末冶金法制备NiFe₂O₄纳米粉增韧NiFe₂O₄陶瓷铝电解惰性阳极, 研究了NiFe₂O₄纳米粉添加量对NiFe₂O₄陶瓷惰性阳极烧结行为和材料性能的影响。通过线收缩和SEM对NiFe₂O₄陶瓷的烧结性能和显微结果进行分析。研究结果表明: 随着NiFe₂O₄纳米粉添加量的增加, 烧结收缩程度逐渐增大, 烧结致密化开始温度和烧结初期活化能逐渐降低, 添加量为40%时试样从900℃开始大幅度收缩, 烧结初期表观活化能下降到291.43 kJ/mol。NiFe₂O₄陶瓷惰性阳极的体积密度、抗弯强度和断裂韧性随NiFe₂O₄纳米粉添加量的增加均呈现先上升后下降的变化趋势, 气孔率和静态腐蚀率呈先下降后上升的趋势, 均在30%达到极值, 断裂韧性达到最大值3.12 MPa•m^1/2, 是未添加纳米粉试样的2.14倍。NiFe₂O₄纳米粉的添加能够明显增强晶界结合强度, 降低陶瓷材料气孔率, 从而提高断裂表面能实现增韧作用。     

Shape-dependent photocatalytic activities of bismuth subcarbonate nanostructures

Different shaped bismuth subcarbonate ((BiO)2CO3) nanostructures including irregular nanoplates, relatively uniform nanoplates and nanocubes were prepared and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflection spectroscopy (DRS) and nitrogen adsorption. The photocatalytic performance of the as-synthesized (BiO)2CO3 nanostructures on the degradation of Rhodamine B (RhB), methyl orange (MO) and methyl blue (MB) were evaluated under UV-vis light irradiation (modeling sunlight). The photocatalysis tests showed that all the different (BiO)2CO3 nanostructures displayed enhanced photodegradation performance compared with commercial (BiO)2CO3. The irregular (BiO)2CO3 nanoplates exhibited the highest photocatalytic activity on the degradation of different organic dyes. (BiO)2CO3 nanosturctures exhibited the different capacity to bleach the three organic dyes, which might be attributed to their different molecular structures. This work may provide a potential photocatalyst for the environmental pollutants treatments.     

低温燃烧合成法制备纳米NiFe_2O_4

以九水硝酸铁、六水硝酸镍、水溶性肼类燃料为原料,添加金属离子络合剂、分散剂等为辅助剂,利用溶液燃烧合成法制备了纳米NiFe2O4粉体。利用XRD、TEM、SEM等测试方法对产物进行了表征,并研究了不同燃料、络合剂用量、分散剂用量、煅烧温度对粉体粒径和形貌的影响。实验结果表明,在以水溶性肼为燃料、络合剂2g、分散剂2g、煅烧温度800℃、煅烧时间2h时,可获得粒径均匀的纳米NiFe2O4粉体。所得产物的粒径范围为40～80nm,结构膨松,分散性良好。     

NiFe2O4/TiO2纳米棒阵列薄膜光电化学性能和光催化性能研究

用水热法制备一维有序纳米棒状TiO₂薄膜(TiO₂ NRAs), 并采用浸渍沉积煅烧得到NiFe₂O₄/TiO₂ NRAs。借助SEM、TEM、XRD、Raman、XPS、UV-Vis等对样品的物相和形貌结构进行了表征, 结果表明: NiFe₂O₄纳米颗粒均匀沉积在金红石相TiO₂ NRAs表面, 使TiO₂光谱吸收范围拓展至可见光区。利用电化学工作站对其光电转换性能进行研究, 发现NiFe₂O₄改性后的TiO₂在可见光下光电流响应显著增大, 在电压-电流曲线和电流随时间开关灯变化中, NiFe₂O₄/TiO₂ NRAs的光电流密度分别是纯TiO₂ NRAs的12倍和8倍。NiFe₂O₄/TiO₂ NRAs可见光下降解偏二甲肼(UDMH)的效率是单纯TiO₂ NRAs降解率的3倍, 并对光催化降解机理进行了探讨。     

催化相转化法制备纳米铁酸镍及性质研究

用催化相转化法在不同初始浓度，不同pH值下．在液相中短时间内合成出了纳米铁酸镍微晶．利用XRD、TEM对产物进行了表征，并测定了产物的磁化强度、密度及比表面。结果表明，该方法制备的纳米级铁酸镍具有超顺磁性，粒径小于20nm。     

The preparation and characterization of quadrate NiFe2O4/polyaniline nanocomposites

Core-shell structured nanocomposites with NiFe₂O₄ as the magnetic core and polyaniline (PANI) as the conducting shell were prepared. The structural components in the NiFe₂O₄ and NiFe₂O₄/PANI were identified from Fourier transform infrared (FTIR) of the samples. The crystalline phase of NiFe₂O₄ and NiFe₂O₄/PANI was characterized by X-ray diffraction (XRD). The shape and size distribution of particles were observed by transmission electron microgragh (TEM). The thermal stability of samples was ensured by thermogravimetric analysis (TGA). The magnetic properties were measured by vibrating sample magnetometer (VSM). The results indicated that the resultant composites exhibited good quadrate morphology and uniform size with magnetic and conducting characteristic and high thermal stability.     

The effect of support on the structure and photocatalytic activity of ternary ZnO-ZnFe2O4/palygorskite composite photocatalysts

The ternary ZnO-ZnFe₂O₄/palygorskite composite photocatalysts were fabricated via a solvothermal method followed by thermal treatment. The structure, morphology and photoelectric performances of samples were characterized, and the results indicated that ZnO/ZnFe₂O₄ nanoparticles with size of 25–30 nm were adequately anchored on the palygorskite fibers surface. Compared with ZnO, ZnFe₂O₄, ZnO/ZnFe₂O₄ and ZnO/palygorskite, the ZnO-ZnFe₂O₄/palygorskite composite photocatalysts exhibited significantly improved photocatalytic activity in degradation of methylene blue (MB). Especially, the optimal photocatalyst (ZF1.5) displayed the highest photocatalytic activity, achieving 99.68% and 99.48% degradation efficiency after 90 min of UV–vis (350 ≤ λ ≤ 780 nm) and 100 min of visible-light (λ ≥ 420 nm) irradiation, respectively. The photocatalysis degradation process matched well with the Langmuir-Hinshelwood kinetics. The obtained improvement of photocatalytic activity was ascribed to the synergetic effect of superior visible-light utilization; effective charge carrier separation and palygorskite support effect (optimize nanoparticles dispersibility, developed mesoporous structure, enlarge specific surface area and increase adsorption capacity).