Synthesis and evolution of PbS nanocrystals through a surfactant-assisted solvothermal route

We present a surfactant-assisted solvothermal approach for the controllable synthesis of a PbS nanocrystal at low temperature (85 degrees C). Nanotubes (400 nm in length with an outer diameter of 30 nm), bundle-like long nanorods (about 5-15 mum long and an average diameter of 100 nm), nanowires (5-20 mum in length and with a diameter of 20-50 nm), short nanorods (100-300 nm in length and an axial ratio of 5-10), nanoparticles (25 nm in width with an aspect ratio of 2), and nanocubes (a short axis length of 10 nm and a long axis length of 15 nm) were successfully prepared and characterized by transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction pattern. A series of experimental results indicated that several experimental factors, such as AOT concentration, ratio of [water]/[surfactant], reaction time, and ratio of the reagents, play key roles in the final morphologies of PbS. Possible formation mechanisms of PbS nanorods and nanotubes were proposed.     

Enhanced photocatalytic activity of cobalt-doped CeO2 nanorods

In this paper, CeO₂ and cobalt-doped CeO₂ nanorods synthesized by surfactant free co-precipitation method. The microstructures of the synthesized products were characterized by XRD, FESEM and TEM. The structural properties of the grown nanorods have been investigated using electron diffraction and X-ray diffraction. High resolution transmission electron microscopy studies show the polycrystalline nature of the Co-doped cerium oxide nanorods with a length of about 300?nm and a diameter of about 10?nm were produced. The X-ray Photoelectron spectrum confirms the presence of cobalt in cerium oxide nanorods. From BET, the specific surface area of the CeO₂ (Co-doped) nanostructures (131 m²?g^??) is found to be significantly higher than that of pure CeO₂ (52 m²?g^??). The Co-doped cerium nanorods exhibit an excellent photocatalytic performance in rapidly degrading azodyes acid orange 7 (AO7) in aqueous solution under UV illumination.     

(Ba, Sr)TiO3纳米棒的反相微乳法制备与表征

在氢氧化钡和氢氧化锶水溶液/Triton X-100/环己烷/正己醇四元W/O型反相微乳液中制备了钛酸锶钡纳米棒, 研究了ω₀值(水与表面活性剂Triton X-100的物质的量之比)、反应物浓度、陈化时间对产品形貌和尺寸的影响, 用TEM, SAED, SEM, EDS和XRD等技术对产品进行了表征. 结果表明, 所得Ba_0.7Sr_0.3TiO₃纳米棒长约500～1200 nm、直径约为50～120 nm; 具有立方相单晶结构. 产品中钡、锶、钛的物质的量之比约为0.7∶0.3∶1.     

A simple method of fabricating large-area α-MnO2 nanowires and nanorods

α-MnO₂ nanowires or nanorods have been selectively synthesized via the hydrothermal method in nitric acid condition. The α-MnO₂ nanowires hold with average diameter of 50 nm and lengths ranging between 10 and 40 μm, using MnSO₄·H₂O as manganese source; meanwhile, α-MnO₂ bifurcate nanorods with average diameter of 100 nm were obtained by adopting MnCO₃ as starting material. The morphology of α-MnO₂ bifurcate nanorods is the first one to be reported in this paper. X-ray powder diffraction (XRD), field scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products. Experimental results indicate that the concentrated nitric acid plays a crucial role in the phase purity and morphologies of the products. The possible formation mechanism of α-MnO₂ nanowires and nanorods has been discussed.     

氢氧化钴纳米棒的室温固相化学合成及其表征

一维或准一维纳米结构体系或纳米材料的研究,既是研究其他低维材料的基础,又与纳米电子器件及微型传感器密切相关,是近年来国内外研究的前沿.尽管有许多合成一维纳米材料的方法[1～4],但是这些方法往往各有其局限性且大多需要多个步骤,操作复杂,条件苛刻.因此,寻找反应条件温和,易于操作,适用范围广,一步就能制备一维纳米材料的新方法尤为重要.     

Fabrication of symmetric hierarchical hollow PbS microcrystals via a facile solvothermal process

Symmetric hierarchical hollow PbS structures consisting of nanowalls were successfully fabricated by a facile solvothermal process in ethylenediamine at 120 degrees C for 12 h, employing lead acetate trihydrate and dithizone as precursors; the thickness of the nanowalls is about 80 nm. No surfactants or other templates were used in the process. The synthesized product was characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), ultraviolet-visible spectrometer (UV-vis), near-infrared absorption spectroscopy (near-IR), and fluorescence spectrophotometer. The effect of the reaction conditions on the size and morphologies of PbS structures was investigated. The results show that the temperatures, solvent, and sulfur sources are crucial factors on the morphologies and sizes of the symmetric hierarchical hollow PbS microcrystals. A possible growth mechanism of hierarchical hollow PbS structures is presented. UV-vis absorption spectrum holds a weak peak at 253 nm; the near-infrared absorption spectrum of PbS microcrystals has the two absorption peaks centered at 9613 cm(-1) (1040 nm) and 6771 cm(-1) (1477 nm), showing a blue shift compared with the bulk PbS (approximately 3020 nm). And the fluorescence spectrum of PbS microcrystals consists of an emission peak with a maximum at 305 nm. These PbS microcrystals may have potential applications in the fundamental study of nanostructures as well as fabricating nanodevices.     

Well Crystallized α-GaOOH Nanocrystals Synthesized through Hydrothermal Routes and Their Properties

A facile hydrothermal process involving Ga(NO₃)₃·H₂O·NaN₃ solutions led to the formation of α‐GaOOH nano‐platelets. X‐ray diffraction (XRD) pattern revealed that the synthesized samples belonged to an orthorhombic crystal structure with lattice constants a=0.4510 nm, b=0.9750 nm and c=0.2965 nm. Transmission electron microscopy (TEM) studies showed that α‐GaOOH displayed the morphologies of an eccentric platelet‐like structure with 60–120 and 200–300 nm in the short and long axes, respectively. The average thickness of products was about 70 nm through scanning electron microscopy (SEM) images. The ultraviolet absorption of the samples was at 214 nm. The prepared α‐GaOOH nano‐platelets exhibited a broad emission band from 220 to 400 nm with a maximum at 343 nm under short UV excitation of 200 nm. Fourier transform infrared (FTIR) spectrum confirmed the existence of Ga₂O and Ga–OH bending modes. A possible mechanism for the formation of α‐GaOOH nano‐platelets was discussed briefly.     

Formation of Eu2O3 Nanorods through Solvothermal Routes by Surfactant Assistance

Eu₂O₃nanorods were synthesized and characterized. The crystallites of Eu₂O(CO₃)₂·H₂O nanorods and Eu₂O₃ nanorods were obtained by means of surfactant assistance, with aqueous butanol solution as the solvent and hexamethylene tetramine as the base. The characteristics of the nanorods were analyzed by transmission electron microscopy, high‐resolution transmission electron microscopy, scanning electron microscopy and X‐ray diffraction. The Eu₂O₃ nanorod is about 80–300 nm in diameter and 1–5 µm in length. The formation mechanism of the 1D products was also proposed.     

球状、立方状及空心立方状PbS纳米晶的控制合成及其形成机理

以醋酸铅为铅源,硫代乙酰胺为硫源,在表面活性剂十二烷基硫酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)共同作用下,通过简单地调节水热反应的反应温度控制合成出球状、立方状和空心立方状PbS纳米晶。利用XRD、TEM对合成产物的结构和形貌进行了表征,发现合成的球状、立方状和空心立方状PbS纳米晶尺寸均一,直径为100 nm左右。对球状、立方状和空心立方状PbS纳米晶的形成机理进行了初探,结果表明反应温度较低时,水热反应初始阶段形成的PbS小颗粒呈球形,在表面活性剂SDS的烷基链模板和CTAB微胶束软模板共同作用下生成球状PbS纳米晶;反应温度较高时,水热反应初始阶段形成的PbS小颗粒由于自身的立方相岩盐晶体结构的影响有呈立方状趋势,在SDS和CTAB共同作用下产物堆积成空心立方体状或立方状。     

PbS nanostructures synthesized via surfactant assisted mechanochemical route

PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM, surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa₂•2H₂O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate crystal morphology by combining effect of milling and surfactant application.      

Thermal analysis and phase evolution of nanocrystalline perovskite oxide materials synthesized via hydrothermal and self-combustion methods

Nanocrystalline perovskite oxide materials ABO₃ (where A = Ba, Ca, Mg, Sr; and B = Ce, Mn, and Ti) have been synthesized via sol-citrate combustion and hydrothermal-based methods with and without surfactant under mild conditions. Metal-titanates (ATiO₃) were prepared using synthesized anatase-TiO₂ nanotube powder, metal hydroxide/chloride solutions, and NaOH as raw materials. The stoichiometric amount of all reactants were put in polytetrafluoroethylene (PTFE)-lined stainless steel digestion reactor and were kept in convention oven at desired reaction conditions like mole composition, pH, temperature, and time, in range A/Ti = 0.9–1.1, 10–12, 150–170 °C for 24–48 h, respectively. The nanocrystalline barium cerium oxide (BaCeO₃) was synthesized using citric acid as polymerization agent in sol-combustion process, whereas barium manganite (BaMnO₃) was prepared via hydrothermal process using polyethyl glycol surfactant as structure directing agent. Thermal stability, phase evolution, and morphology of synthesized products were characterized by thermogravimetry and differential thermal analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD results revealed that synthesized CaTiO₃ and BaMnO₃ nanorods had an orthorhombic perovskite and hexagonal structure, respectively; whereas, the nanoparticle morphologies of BaTiO₃, Ba_0.5Sr_0.5TiO₃, and MgTiO₃, BaCeO₃ perovskite oxides were found strongly depended on pH of the precursor solutions. SEM images showed variety of morphological structures ranging from nanostructured surface with distinct particles morphology to nanowires and nanorods (length varies from nano to several micrometers) and uniform diameter ~<100 nm, depending upon the hydrothermal reaction conditions.     

Effect of polyvinylpyrrolidone as capping agent on Ce3+ doped flowerlike ZnS nanostructure

Nanoparticles of zinc sulfide doped with Ce³⁺ have been synthesized through a simple chemical precipitation method utilizing optimum dopant concentration (1.5 g) and employing various concentrations of polyvinylpyrrolidone (PVP, M.W: 40,000) as capping agent. The optical properties of the synthesized products were studied by UV–Vis absorption and photoluminescence measurements. The phase and size of the products were predicted by X-ray diffraction data. The existence of functional groups in the synthesized products was identified by Fourier transform infrared spectroscopy. Field emission scanning electron microscope results of Ce³⁺ doped ZnS show a uniform growth pattern of the nanorods with flowerlike structure. However, on surfactant assisted Ce³⁺ doped ZnS nanoparticles, the morphology of the products was changed from rod to spherical particles. The morphologies of the uncapped and PVP capped ZnS nanocrystals were confirmed by high resolution transmission electron microscopy.     

Preparation and Magnetic Property of La0.7Sr0.3MnO3 Nanorod by Combination Sol-Gel with Molten Salt

La0.7Sr0.3MnO3（LSMO） nanorods were synthesized by a method combining sol-gel with molten salts at 950 ℃ for 10 h, which employed KCl＋NaCl（mass ratio 4：1） as eutectic molten salts. The morphologies and magnetic properties of the resulting LSMO nanorods were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and vibrating sample magnetometer（VSM） measurements. It was found that the obtained perovskite manganite LSMO was a uniform nanorod with a diameter of about 50 nm and a length of longer than 500 rim. The Curie temperature（To） of the LSMO nanorod used here was 262 K, much lower than that of bulky single crystal LSMO（360 K）. The low Curie temperature might be a result of the great disorder near the grain boundary, which could be observed clearly from the TEM picture.     

Synthesis and photophysics of leadsulphide nanocrystallites

Nanoparticles of lead sulphide have been stabilized in the presence of excess Pb²⁺ in aqueous basic medium by a simple chemical route of synthesis. These PbS nanoparticles were synthesized very conveniently at room temperature using hexametaphosphate as stabilizer. These nanoparticles have an absorption extending into the NIR region. A significant quantum confinement effect made the bandgap of lead sulphide nanoparticles produce a blue shift from 0.41 eV to about 1.5 eV. The size and morphology of the particles were studied by TEM. Particles were relatively small sized (about 6 nm) having narrow size distribution. XRD data analysis indicate that the product is a mixture of PbS, PbO and Pb(OH)₂. Both XRD pattern and HRTEM images confirm the crystalline structure of lead sulphide crystals. IR spectroscopy indicates the formation of PbS. PbS nanoparticles were fairly stable and could be stored for about three weeks at room temperature and for about two months at 5°C without agglomeration. These particles were photoactive and sensitized the reaction of aniline by light leading to the formation of azobenzene.     

微波固相合成氧化锌纳米棒

通过前驱体的微波固相热分解法快速合成了氧化锌纳米棒, 其直径在60～385 nm之间, 长可达数微米. 前驱体则通过一步室温固相反应制备. 用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能量色散X射线分析(EDX)和透射电子显微镜(TEM)对产物的结构和形貌进行了表征. 同时, 对氧化锌纳米棒的光致发光(PL)性能作了测试, 结果表明在355 nm处有一个明显的近带隙发射峰. 另外, 对比实验表明, 微波辐射在氧化锌纳米棒的形成过程中起了关键性作用, 并对其形成机理进行了初步探讨.     

Synthesis and luminescence properties of Eu(III)-doped silica nanorods based on the sol–gel process

Uniform Eu³⁺-doped SiO₂ nanorods were synthesized through a simple sol–gel method using cetyltrimethylammonium bromide (CTAB) as surfactant template and tetraethylorthosilicate as silicon source. X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrum, scanning electron microscope (SEM), transmission electron microscopy, and photoluminescence spectra were employed to characterize the products in detail. The nanorods have good uniformity and their diameters and lengths are in the range of 200–300 and 500–700 nm through the SEM images, respectively. The formation of the nanorods was studied by taking SEM images after different aging time. The experimental results indicate that CTAB plays a crucial role in the formation of the silica nanorods. The luminescence of Eu³⁺-doped SiO₂ nanorods is dominated by red-emission around 612 nm due to intra-atomic 4f → 4f (⁵D₀ → ⁷F₂₎ transition of Eu³⁺ ions. Furthermore, the effect of doping concentrations of Eu³⁺ ions on the luminescence was investigated.     

Sonochemical synthesis of mass single-crystal PbS nanobelts

Based on sonochemical technique, large-scale PbS nanobelts are successfully synthesized in the mixed solution of PbCl₂ and Na₂S₂O₃. These nanobelts are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), selected area electronic diffraction, energy dispersive X-ray spectroscopy, and high-resolution TEM. The as-synthesized PbS nanobelts have width of about 80 nm, length up to several millimeters, and width-to-thickness ratio of about 5. In addition, the growth mechanism of PbS nanobelts is suggested.     

Synthesis and Characterization of Lead Sulfide Nanoparticles in Zirconia-Silica-Urethane Thin Films Prepared by the Sol-Gel Process

PbS nanocrystals (NCs) ranging between 4–8 nm were incorporated into Zirconium-Silica-Urethane (ZSUR) matrix obtained by the sol-gel method. The sizes of the particles were controlled by temperature treatment and by concentration of PbS in ZSUR matrix. The sizes of PbS NCs were determined by TEM measurements. The quantum size effect could also be extracted from optical absorption and photoluminescence spectra. The new matrix allows incorporation of up to 40% PbS forming a characteristic structure of dendrite by reacting lead acetate with ammonium thiocyanate in sol-gel matrix. The sol precursors of the matrix for Zirconium-Silica-Urethane contained zirconium oxide (ZrO₂) matrix solution, tetramethoxysilane (TMOS), 3-glycid oxypropyl trimethoxysilane (GLYMO) and polyethylene urethane silane (PEUS) synthesized separately. The ZrO₂ matrix solution was obtained from zirconium n-tetrapropoxide in propanol and acetic acid was used as a chelating agent to stabilize the zirconium oxide precursor.     

Phase-controlled synthesis and characterization of nickel sulfides nanorods

Different one-dimensional nickel sulfides, NiS nanorods and Ni₉S₈ nanorods were synthesized in the presence (Route 1) and absence (Route 2) of gas CO₂. X-ray powder diffraction patterns, scanning electron microscopy and transmission electron microscopy images show that the product from Route 1 is NiS nanorods with a diameter of about 50-120 nm, while the product from Route 2 is Ni₉S₈ nanords about 70-200 nm in diameter. A molecular-template-like mechanism was proposed for the one-dimensional structures growth. The products were also investigated by Raman and photoluminescence (PL) spectroscopy.     

Synthesis and characterization of PbS nanotubes in bicontinuous microemulsion system

PbS nanotubes were successfully synthesized in bicontinuous microemulsion system containing cyclohexane, aqueous solution, n-pentanol and surfactant OP (polyethylene glycol p-octylphenyl ether). The morphology of PbS nanotubes was confirmed by the transmission electron microscopy. The crystallinity and structural features of PbS nanotubes were characterized by powder X-ray diffraction. The effect of key parameters, such as the molar ratio of water to surfactant and the reactant concentration, on the resulting product has also been investigated. The formation mechanism of PbS nanotubes and nanowires synthesized in bicontinuous microemulsion system has been discussed.