从Mn3O4前驱体到MnO2纳米结构的形貌和结构变化

锰氧化物是一类重要的且具有广泛应用背景的材料, 控制合成不同形貌和组成的锰氧化物纳米结构将有助于拓宽其应用领域. 本文报道了以Mn3O4为前驱体, 通过水热法控制合成MnO2纳米结构的方法. 用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等手段对产物进行表征. 在硫酸体系中,当反应温度为80 和180 ℃时, 所得产物分别为γ-MnO2海胆结构和β-MnO2单晶纳米棒. 此外, MnOOH纳米线可以在稀酸溶液中合成. 考察了反应温度、溶液酸度、反应时间对产物结构的影响, 并提出了基于γ-MnO2为中间产物的反应机理. 实验结果表明, 水热体系促进了产物的各向异性生长并最终形成不同形貌和结构的锰氧化物.     

简单方法合成α-MnO2和β-MnO2单晶纳米棒

通过简单的水热方法分别在150 ℃和220 ℃选择控制合成了单晶α-MnO2和β-MnO2纳米棒. 并用扫描电镜(SEM)、透射电镜(TEM)、能谱元素分析(EDX)、粉末X射线衍射(XRD)对产物进行了表征. 结果表明, 在水热反应过程中, 温度在控制合成α-MnO2和β-MnO2纳米棒中起到重要作用     

系列纳米结构锰氧化物的水热合成

以KMnO₄为锰源、抗坏血酸(AA)为还原剂,采用水热法制备系列纳米结构锰氧化物。通过调节反应物的物质的量的比、水溶液的pH值、反应温度和反应时间,制备出了不同纳米结构的锰氧化物,包括Mn₃O₄纳米粒子、MnOOH、α-MnO₂和β-MnO₂纳米棒。采用XRD和TEM测试技术对合成产物进行了表征,同时对其反应机理进行了探讨。     

反应条件对乳液法自组装合成氧化锰纳米粒子结构、形貌和尺寸的影响

通过改变反应物物质的量比、分散相与连续相体积比、反应体系温度和煅烧后处理温度,研究了反应条件对乳液法自组装合成氧化锰纳米粒子结构、形貌和尺寸的影响.结果表明:当高锰酸钾与油酸物质的量比在1∶5～1∶1之间时,形成蜂窝状纳米粒子和空心纳米粒子;当分散相(油酸)与连续相(水)的体积比为4∶200时,形成良好的空心球纳米结构;反应体系温度升高不利于产物的洗涤;不同温度的煅烧后处理不仅影响氧化锰纳米粒子的形貌,而且影响其结晶度和晶型.     

反相胶束法控制合成不同形貌半导体Ag_2S纳米晶

采用水 (溶液 ) /TritonX 10 0 /环已烷 /正戊醇反相胶束体系 ,制备出不同形貌的Ag2 S纳米晶 ,其中合成出的直径为 5 0～ 10 0nm、长度为 2 .0～ 3.5 μm、长径比为 2 0～ 70的纯相Ag2 S纳米棒为首次报导 .就不同ω0 、反应物浓度和陈化时间等因素对合成Ag2 S的形貌和尺寸的影响进行了研究 ,获得了控制合成不同形貌Ag2 S纳米晶的反应条件 .所得产物利用透射电子显微镜分析进行了表征     

一维纳米结构MnO2的微波合成及其电化学性能

以在水热条件下合成的纳米结构γ-MnOOH为前驱物, 以K2S2O8为氧化剂, 采用单模式微波加热法制备出一维纳米结构MnO2. 采用XRD和TEM等手段对样品进行了表征. 以在100 ℃下水热合成的γ-MnOOH纳米纤维为前驱物时, 制得α-MnO2纳米纤维; 以在150 ℃下水热合成的γ-MnOOH纳米棒为前驱物时, 制得β-MnO2纳米棒. 分别用α-MnO2纳米纤维和β-MnO2纳米棒作为Li/MnO2电池的正极材料进行恒电流放电实验, 研究结果显示, α-MnO2纳米纤维的放电容量为270.23 mA·h/g, β-MnO2纳米棒的放电容量为186.66 mA·h/g.     

基于MCM-41模板制备β-MnO_2纳米纤维及其催化降解亚甲基蓝染料

以介孔氧化硅材料MCM-41为模板,硝酸锰为锰源,通过浸渍、450℃焙烧4 h得到Mn-MCM-41,用NaOH溶液溶解除去氧化硅模板得到锰氧化物,采用XRD,HRTEM和N2吸附-脱附等测试技术对产物进行了表征.结果表明,所得产物是纯相的β-MnO2纳米纤维,直径小于3 nm.纳米纤维之间有序排列组成类似MCM-41模板的介孔结构,其比表面积达到136.5 m2/g.将所制备的β-MnO2纳米纤维用于催化过氧化氢氧化分解质量浓度为60 mg/L的亚甲基蓝(MB)模拟染料废水,经100 min反应后,亚甲基蓝水溶液脱色率达到97.59%.所制备的催化剂对降解处理高浓度亚甲基蓝溶液,具有降解脱色率高和反应速度快等优点.     

用于筛膜反应器的γ-MnO2纳米粉的合成

醋酸锰与柠檬酸发生沉淀反应生成锰配合物,经热分解和酸处理手段最终制备出γ-MnO2纳米材料,用X射线衍射、差热/热重分析、透射电镜及原子力显微镜等手段对合成的样品进行了表征.同时考察了反应条件对反应速度、最终产品粒度的影响.结果表明,通过对反应条件的控制可以在一定程度上控制产品的粒度,得到了均粒度和超细粒度的γ-MnO2纳米材料.对于异丙醇和环己烷等氧化脱氢反应,γ-MnO2纳米筛膜反应器与传统的固定床反应器相比反应物的转化率提高了20%.     

用于筛膜反应器的γ-MnO_2纳米粉的合成

醋酸锰与柠檬酸发生沉淀反应生成锰配合物,经热分解和酸处理手段最终制备出γ-MnO2纳米材料,用X射线衍射、差热/热重分析、透射电镜及原子力显微镜等手段对合成的样品进行了表征.同时考察了反应条件对反应速度、最终产品粒度的影响.结果表明,通过对反应条件的控制可以在一定程度上控制产品的粒度,得到了均粒度和超细粒度的γ-MnO2纳米材料.对于异丙醇和环己烷等氧化脱氢反应,γ-MnO2纳米筛膜反应器与传统的固定床反应器相比反应物的转化率提高了20%.     

ZnO纳米环的可控合成

以六次甲基四胺(Hexamethylenetetramine, C6H12N4)和水合硝酸锌[Zn(NO3)2·2H2O]为原料, 表面活性剂聚丙烯酰胺-氯化二烯丙基二甲基铵[poly(acrylamide-co-diallyldimethylammonium chloride, 缩写为PAM-CTAC]为形貌控制剂, 采用液相沉淀法合成了ZnO纳米环. 产物的结构与形貌经X射线粉末衍射(XRD)和扫描电子显微镜(SEM)表征. 研究了不同实验条件(如表面活性剂的浓度、反应物浓度、反应温度和反应时间等)对产物形貌与尺寸的影响. 讨论了PAM-CTAC作用下ZnO纳米环可能的形成机理. 结果表明, 合成产物为六方Wurtzite型结构的ZnO纳米环, 环内径约为220 nm, 壁厚约为70 nm. 反应物浓度、反应温度对ZnO纳米环的形成以及纳米环的尺寸都有一定的影响, 但起关键作用的是PAM-CTAC. 通过改变PAM-CTAC的浓度, 能有效地实现ZnO纳米环的可控合成. 室温荧光光谱显示, ZnO纳米环的紫外发射峰具有较窄的半高宽(FWHM)(约7 nm), 表明合成产物具有较窄的尺寸分布.     

Synthesis and bioanalytical applications of specific-shaped metallic nanostructures: A review

Many successful synthesis routes for producing different shapes of metallic nanostructures, including sphere, rod, cube, and hollow shapes, have been developed in the past few decades. Many applications using these nanostructures have been studied because the outstanding properties of the nanostructures are not exhibited by their bulk-state counterparts. This review paper reports some recent developments in clinical and biosensor applications. The first part focused on the synthesis methods of metallic nanostructures having various shapes along with their optical properties. The second and third part is an introduction of the gold nanoparticle assemblies and arrays, explaining the conjugation methods of metallic nanostructures with biological entities. The final part reviews on the recent bioanalytical applications using various shapes of metallic nanostructures.     

Effects of shape and size of cobalt ferrite nanostructures on their MRI contrast and thermal activation

Cobalt ferrite magnetic nanostructures were synthesized via a high temperature solution phase method. Spherical nanostructures of various sizes were synthesized with the help of seed mediated growth of the nanostructures in organic phase, while faceted irregular (FI) cobalt ferrite nanostructures were synthesized via the same method but in the presence of a magnetic field. Magnetic properties were characterized by SQUID magnetometry, relaxivity measurements and thermal activation under RF field, as a function of size and shape. The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the FI nanostructures exhibit lower saturation magnetization than their spherical counterparts. The relaxivity coefficient of cobalt ferrite nanostructures increases with increase in size; while FI nanostructures show a higher relaxivity coefficient than spherical nanostructures with respect to their saturation magnetization. In the case of RF thermal activation, the specific absorption rate (SAR) of nanostructures increases with increase in the size. The contribution sheds light on the role of size and shape on important magnetic properties of the nanostructures in relation to their biomedical applications.     

Ultrathin Covalently Bound Organic Layers on Mica: Formation of Atomically Flat Biofunctionalizable Surfaces

Mica is the substrate of choice for microscopic visualization of a wide variety of intricate nanostructures. Unfortunately, the lack of a facile strategy for its modification has prevented the on‐mica assembly of nanostructures. Herein, we disclose a convenient catechol‐based linker that enables various surface‐bound metal‐free click reactions, and an easy modification of mica with DNA nanostructures and a horseradish peroxidase mimicking hemin/G‐quadruplex DNAzyme.     

桑葚状CaF2纳米材料的合成及CaF2:yb3+的光学性质

通过一步水热法合成了分散性良好、尺寸均一的桑葚状CaF2纳米材料,采用X射线粉末衍射(XRD)、场发射扫描电子显微镜(FESEM)和透射电子显微镜(TEM)对产物的结构、形貌及尺寸进行了表征,发现CaF2纳米材料是由尺寸约为50 nm的纳米粒子构成.通过对不同反应阶段产物的分析提出了其形成机理,研究了yb3+掺杂CaF...     

Kinetics-driven growth of orthogonally branched single-crystalline magnesium oxide nanostructures

Orthogonally branched single-crystalline magnesium oxide nanostructures were synthesized through a simple chemical vapor transport and condensation process in a flowing Ar/O(2) atmosphere. Other morphologies, such as cubes and nanowires, can also be obtained under different controlled conditions. The formation of different types of nanostructures can be tuned by modifying oxygen partial pressure during the synthesis. All the nanostructures are cubic single-crystalline enclosed by low-index {100} facets. Growth mechanisms for the nanostructures are discussed in detail: different supersaturation ratios, relatively high substrate temperatures, and surface defects in certain crystallographic planes cooperatively take important effects on determining the product morphologies. Structural defect-related blue light emission of the three types of MgO nanostructures was investigated. The MgO nanostructures with abundant morphologies may find applications in various nanodevices, and the kinetics-driven methodology might be exploited to synthesize similar nanostructures of other functional oxide materials.     

Recent Development on Controlled Synthesis of Metal Sulfides Hollow Nanostructures via Hard Template Engaged Strategy: A Mini‐Review

In this mini‐review, we highlighted the recent progresses in the controlled synthesis of metal sulfides hollow nanostructures via hard template technique. After a brief introduction about the formation mechanism of the inorganic hollow nanostructures via hard template technique, the discussions primarily focused on the emerging development of metal sulfides hollow nanostructures. Various synthetic strategies were summarized concerning the use of the hard template engaged strategies to fabricate various metal sulfides hollow nanostructures, such as hydrothermal method, solvothermal method, ion‐exchange, sulfidation or calcination etc. Finally, the perspectives and summaries have been presented to demonstrate that a facile synthetic technique would be widely used to fabricate metal sulfides hollow nanostructures with multi‐shells and components.     

Metal and Metal Oxide Nanostructures Prepared by Electrical Arc Discharge Method in Liquids

In this review, the importance of electrical arc discharge technique in liquids in synthesis of various nanostructures from carbon based materials to metal and metal oxide nanostructures with their general and specific properties, especially the photocatalytic performance of metal oxide nanostructures is studied. The effect of arc current on size distribution, morphology and physicochemical properties of metal and semiconductor nanostructures was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS) and UV–Vis spectroscopy. WO₃ Cubic nanostructures with 30 nm mean particle size were formed during the discharge process in water. Discharge between zinc electrodes in water leads to formation of rod like and semi spherical ZnO nanostructures with 15–20 nm diameter range. ZrO₂ nanoparticles were formed using zirconium electrodes in water. Photodegradation of Rhodamine B (Rh. B) shows that the as prepared nanostructures in this method have potential ability for environmental purifications. Also, using silver electrodes in water leads to formation of silver nanoparticles with 8–15 nm average particle size. Moreover, a novel method for synthesis of gold nanoparticles without using gold electrodes is presented. Finally, the future outlook of this technique in synthesis of various nanocrystalline materials is presented.     

Self-assembly of conjugated polymers for anisotropic nanostructures

As their potential applications in various electronic devices increase, the preparation of anisotropic conjugated polymer nanostructures are highly desirable. This paper presents a review of the literature and our recent results on the self-assembly of one-, two- and three-dimensional anisotropic nanostructures using conjugated polymers as building blocks, including the formation of one-dimensional (1D) nanofibers and nanotubes, two-dimensional (2D) nanoribbons and nanosheets, and three-dimensional (3D) superstructures. The mechanisms guiding the formation of various nanostructures are analyzed by a cooperative effect of - stacking interaction and other noncovalent interactions.     

Controlled way to prepare quasi-1D nanostructures with complex chemical composition in porous anodic alumina

Herein we propose a novel approach to the preparation of quasi-1D nanostructures with various chemical compositions based on infiltration of colloidal solution into the asymmetric anodic alumina membrane. The proposed technique was successfully applied for the preparation of ordered arrays of the magnetically hard anisotropic hexaferrite nanostructures.