多元醇热法制备银纳米线及其在透明导电薄膜中的应用

利用多元醇热法,以乙二醇为溶剂和还原剂,聚乙烯吡咯烷酮(PVP)为表面活性剂,硝酸银为银源,讨论了温度和二氧化钛(P25)在混合体系中的添加量对银纳米线长度的影响。用扫描电子显微镜(SEM)对银纳米线的形貌进行了表征,利用X射线衍射(XRD)分析了银纳米线的晶体结构,利用紫外可见透射光谱分析了在350~1 100nm波段内的银纳米薄膜的透光性能。研究表明,当温度为140℃,且在反应体系中添加4 mg P25时,银纳米线的平均长度最长,制备的银纳米线薄膜透过率在550nm为88%时,薄膜方块电阻为12.1Ω/□。     

醇热法可控制备大长径比银纳米线的研究

使用多元醇热还原法制备出了具有大长径比的银纳米线,研究了银纳米线的生长过程并分析了其生长机制。实验选择不同的还原剂种类、不同分子量的PVP及成核控制剂进行了研究。优化了AgNO3的浓度、反应温度和时间等工艺参数,得到了乙二醇体系下制备出银纳米线的最佳实验方案,其优化工艺参数为2mmol/L硫化钠乙二醇溶液、0.19~0.25g PVP、50mmol/L硝酸银乙二醇溶液。对所得银纳米线的形貌和结构进行了系统的表征。结果表明,产物为面心立方结构的纯银纳米线,产物结晶度好、尺寸形貌均匀、长度为100~200μm、直径为60~100nm。按此方案进行放大制备,得到的银纳米线仍然保持良好的形貌尺寸,且产量高、工艺稳定,具有量产的可能。     

多元醇介导还原的银纳米线的形貌与结构调控

以硝酸银为银源、乙二醇为还原剂，采取溶剂热反应途径，制备了高长径比的银(Ag)纳米线，通过聚乙烯吡咯烷酮(PVP)的选择性晶面吸附、乙二醇的介导和无机离子的辅助作用，对Ag纳米线的物相和形貌结构进行了有效调控。详细地考察了PVP加入量、无机离子助剂摩尔配比、反应时间和温度等因素对Ag纳米线产物形貌的影响。结果表明：将PVP浓度控制在44g/L,调节等摩尔离子(Fe³⁺、Cu²⁺)助剂的总浓度为0.24mmol/L,在408K温度下进行5h溶剂热反应，可获得平均线径70nm、平均长度高于40μm的Ag纳米线，非线性副产物(如微纳米Ag晶粒)占比不超过5%,且Ag纳米线产物的纯度高、结晶度良好。     

强静磁场对溶剂热合成纳米Bi形态的影响

研究了强静磁场对溶剂热合成纳米Bi形态的影响.实验中选用乙二醇或乙二醇与乙醇的混合液作溶剂、硝酸铋作铋源.结果表明,磁场能促进Bi纳米呈各向异性生长,并诱导合成纳米线.随着磁场强度的提高,产物中纳米线的比例逐步增大;反应温度越高,产物中获得全部纳米线所对应的磁场强度越低;在150℃、磁场强度达到12T时,产物中没有得到全部纳米线,在180℃和210℃时,产物中全部纳米线所对应的磁场强度分别为12T和8T.采用乙二醇与乙醇的混合液作溶剂时,产物中纳米线所对应的磁场强度提高.最后讨论了磁场诱导合成Bi纳米线的原因.     

L-半胱氨酸诱导单晶银纳米线的快速合成及表征

采用化学还原法,以聚乙烯砒咯烷酮(PVP)为稳定剂和形貌控制剂,乙二醇为还原剂,在L-半胱氨酸诱导下,由硝酸银快速制备了银纳米线。采用紫外-可见吸收光谱、X射线衍射、扫描电子显微镜、选区电子衍射和透射电子显微镜手段对所得产物进行表征,结果表明利用L-半胱氨酸诱导可在15min内制备直径为100nm左右,长度约几百微米的银纳米线,并具有单晶结构,根据实验结果提出了可能的银纳米线快速合成机理。     

银纳米线柔性透明导电薄膜的可控制备和光、电性能

柔性电子学的高速发展,亟需开发新型高透光率、低电阻的的柔性透明导电薄膜。首先在聚乙烯吡咯烷酮(PVP)存在下,用乙二醇还原硝酸银法合成了银纳米线,并采用氯化铁(FeCl3)调节纳米线的直径和长径比,获得了直径为100nm、长度为47μm、分散均匀的银纳米线。然后将银纳米线沉积在聚对苯二甲酸乙二酯(PET)薄膜上形成银纳米线导电薄膜,研究了银纳米线沉积密度和直径对导电薄膜透光率和方阻的影响规律。研究发现,随着纳米线沉积密度的增加,导电薄膜的透过率和方阻都降低,但其品质系数(F.O.M.)增加,最高可达410。当导电薄膜的透光率为80%时,银纳米线直径为35和70nm的体系具有较低方阻,约132Ω/□。而且,该导电薄膜还表现出良好的耐弯曲性能。     

一步法合成银纳米线及应用进展

银纳米线具有优异的光学性能、机械性能、电性能,故在实际应用中具有的广阔的前景。对银纳米线近年来的研究进展与热点进行了综述,首先简单介绍了一步法制备银纳米线的合成机理,然后介绍了银纳米线合成过程中的影响因素,主要包括溶剂不同时,不同的封端剂和还原剂对银纳米线合成的影响,还包含反应温度和反应时间、控制剂、搅拌速度等因素在银纳米线合成过程中的影响,将近几年的典型成果及银纳米线的最新研究进展进行了汇总。最后,对银纳米线在相关应用领域的研究和未来的发展方向进行了展望。     

化学还原法合成均匀银纳米线的条件研究

采用化学还原法,以乙二醇为还原剂,聚乙烯砒咯烷酮(PVP K30)为表面活性剂,通过还原硝酸银(AgNO3)溶液直接制备了高浓度的Ag纳米线溶液,并研究了PVP与AgNO3溶液摩尔浓度比和AgNO3溶液浓度对Ag纳米线生长的影响.用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对纳米Ag晶体的生长形貌进行了比较,利...     

银纳米线的多元醇法制备工艺条件研究

采用多元醇法制备出均匀银纳米线,并详细讨论了温度、PVP与硝酸银物质的量比以及不同卤化物对银纳米线生长的影响。结果表明:当反应温度过低时,无法生成银纳米线,提高反应温度,银纳米线的长度增长;过高的反应温度会导致银纳米线长度不均匀,并降低银纳米线产率;适量的PVP可以促进银纳米线的生长,银纳米线的直径随PVP加入的物质的量的增加而减小;NaCl中Na~+没有去氧能力,CuCl_2中Cu~(2+)去氧能力比FeCl_3中的Fe~(3+)去氧能力强,Br~-促进了银单晶纳米立方块的生成。     

乙二醇溶剂中纳米铜镍复合粉的制备及表征

以聚乙烯吡咯烷酮(PVP)作为高分子保护剂,乙二醇为溶剂,在60℃恒温水浴中,用水合肼还原二价铜、镍盐,合成了铜镍纳米复合粉末.研究了铜镍前驱体浓度比对产物组成的影响,PVP加入量对合成铜镍复合颗粒尺寸的影响.对制得的样品用XRD,TEM进行了表征.结果表明:产物中的铜镍比随着反应物中铜镍比的增加而增加,铜镍复合纳米颗粒的粒度随着PVP浓度的增大而减小.因此,可以通过改变溶液中的Cu2 和Ni2 的比例以及PVP用量得到不同组成和粒度的铜镍复合纳米粉.     

油浴中多羟基还原法快速合成银纳米线

通过简单的油浴加热法,在没有保护气体的氛围中,利用乙二醇还原硝酸银并在聚乙烯吡咯烷酮存在的条件下合成银纳米结构材料。采用扫描电子显微镜和X射线光谱表征产物。分析讨论了聚乙烯吡咯烷酮和银离子的浓度比等对最终纳米结构产物的影响,结果表明,当它们浓度比为1时,溶液中引入微量的氯离子就可以合成出大量的银纳米线。最后探讨了纳米线的合成机理。     

Glycerol and ethylene glycol co-mediated synthesis of uniform multiple crystalline silver nanowires

The large scale synthesis of multiple crystalline silver nanowires (NWs) with uniform diameter were carried out by using glycerol and ethylene glycol (EG) as co-mediated solvents in the presence of poly(vinyl pyrrolidine) (PVP). Experimental results and structural characterizations reveal that Ag NWs are evolved from the multiple crystalline seeds initially generated by the reduction of AgNO₃ with EG and glycerol. Owing to the different reduction ability and viscosity of EG and glycerol, which play an important role for controlling the nucleation at the beginning of reaction, glycerol with high viscosity slows down the migration velocity of Ag⁰ in favor of forming the uniform Ag NWs with small diameter (40 nm) in the presence of PVP molecules selectively adsorbed on the surface of Ag seeds. The yield of the Ag NWs is dependent on the volume ratio of EG and glycerol. In the absence of EG, large amount of Ag nanoparticles (NPs) and few Ag NWs were created. In contrast, Ag nanorods and polyhedral particles are prepared in the case of no glycol added. This paper provides a new approach for the large scale synthesis of Ag NWs with uniform diameter by simply adjusting the solvent components. Furthermore, V-shaped Ag nanostructure was obtained and the possible growth mechanism was discussed.     

A modified polyol process for growing Ag nanowires and nanoplates using 2-ethoxy ethanol

A modified polyol process was proposed to prepare Ag nanowires in this study. The typical reductant, ethylene glycol, was replaced with 2-ethoxy ethanol in the presence of polyvinylpyrrolidone (PVP) to grow Ag nanowires and nanoplates. The growth of Ag nanowires was monitored by the UV–Visible spectrum, which depends on the geometry-dependent surface plasmon resonances of the Ag nanowires. The crystal phase of the Ag nanostructures was identified by X-ray diffraction. Transmission electron microscopy showed that the average dimensions of the Ag nanowires were lengths of approximately 2–10 μm and diameter of 80 nm. The PVP molecules played a key role in directing the growth of the Ag nanostructures along the (111) crystal plane, and the reduction rate of Ag⁺ at 25 °C when 2-ethoxy ethanol was used was faster than when ethylene glycol was used, which improved the growth of the Ag nanowires. When the AgNO₃-to-PVP ratio was adjusted to 2, multiple twinned particles could be observed at an initial stage of the reaction, and a higher yield of the Ag nanowires was synthesized. When the PVP drop rate was slowed, more Ag nanowires were grown. Interestingly, when the AgNO₃ and PVP molecules were initially premixed, Ag nanoplates were generated, rather than nanowires, at a higher temperature in this reduction system.     

Large-scale synthesis of defect-free silver nanowires by electrodeless deposition

We report a new method that generates high-density, long aspect ratio and large-area silver nanowire arrays within the pores of anodic aluminum oxide (AAO) membrane by reducing silver nitrate with ethylene glycol. The freestanding and defect-free silver nanowires can be obtained at high yields. In a typical procedure, the as-prepared silver nanowires have a mean diameter of ∼ 53 nm. It is found out that both temperature and reaction time are important factors in determining the morphology and aspect ratios of nanowires. Lower temperature and longer time are favorable to form polycrystalline silver nanowires with high uniformity and aspect ratios.     

Large-scale synthesis of silver nanowires via a solvothermal method

Silver nanostructures have been synthesized through a simple solvothermal method by reducing silver nitrate (AgNO₃) with ethylene glycol (EG) and using poly(vinylpyrrolidone) (PVP) as an adsorption agent. Different concentrations of ferric chloride (FeCl₃) are added into the solution. It is found that AgCl colloids formed in the initial stage greatly influence the final morphologies of the products. When a low-concentration FeCl₃ solution is used, there is a mixture of silver nanoparticles and nanowires. However, when a high-concentration FeCl₃ solution (100 μM) is used, large amounts of AgCl colloids appear, resulting in decreasing free Ag⁺ during initial formation of silver seeds and slowly releasing of Ag⁺ to the solution in the subsequent reaction. This leads to the formation of silver nanowires. Furthermore, an increase in the concentration of FeCl₃ from 100 to 300 μM results in the synthesis of silver nanowires with larger sizes. In addition, Fe(III) is reduced to Fe(II) form which in turn reacts with and removes adsorbed atomic oxygen from the surface of silver seeds. In this case, uniform silver nanowires can be obtained.     

A precursor nanowire templated route to CdS nanowires

We report the synthesis of the Cd-cysteine precursor nanowires using CdCl₂·2.5H₂O, L-cysteine and ethanolamine in the solvent of water at room temperature. The average diameter and lengths of Cd-cysteine precursor nanowires are 200 nm and several hundred microns, respectively. The precursor nanowires are used as the source materials for cadmium and sulfur and the template for the subsequent preparation of CdS nanowires using ethylene glycol as the solvent by a solvothermal method at 200 °C. The formation process of CdS nanowires is discussed. The samples are characterized using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy.     

One-step construction of silver nanowires in hexagonal mesoporous silica using the polyol process

An original one-step preparation of single-crystal silver nanowires in hexagonal mesoporous silica is presented. The silver precursor, silver nitrate, is reduced in ethylene glycol (EG). This procedure avoids thermal treatments which can lead to phase segregation. The absorbance spectrum of the resulting hybrid material exhibits a transverse resonance plasmon peak near 360 nm whereas the longitudinal oscillation is shifted to the near-infrared region at about 1500 nm.     

One step synthesis of silver nanowires used in preparation of conductive silver paste

For mass preparation of conductive silver paste, a convenient approach to synthesize silver nanowires (Ag NWs) is presented. Monodisperse Ag NWs with ca. 40 nm in diameter and over 10 μm in length were successfully obtained in high yield only by heating a mixture of AgNO₃, poly(vinyl pyrrolidone), ethylene glycol and HCl prepared previously. This method not only simplifies the conventional polyol process but also extremely improves its repeatability. More important, the patterns fabricated with the Ag NWs naturally have a high conductivity, up to ca. 13 % of bulk silver, due to the cross-linked network structure formed by accumulation of nanowires. The conductivity even can be improved to 41 % of bulk silver conductivity through a chemical sintering at room temperature, which makes us believe that the Ag NWs could be broadly applied in preparation of conductive paste.     

Synthesis of silver sulfide nanowires in ethylene glycol through a sacrificial templating route

In this study, Ag₂S nanowires were prepared in ethylene glycol using single-crystal silver nanowires as a sacrificial templating and choosing suitable sulfur sources for the sulfuration reaction. X-ray powder diffraction and a transmission electron microscope equipped with an energy dispersive X-ray analysis were used to characterize the products. The results indicated Ag₂S nanowires with diameters of about one hundred nanometers and lengths up to several micrometers could be obtained through this method. The selected area electron diffraction pattern and high-resolution transmission electron microscope imaging indicated that the Ag₂S nanowires thus formed were crystalline.