Sethi Vaishali, Sen Debasis, Ganguli Ashok K
Department of Chemistry , Indian Institute of Technology , Hauz Khas, New Delhi 110016 , India.
Solid State Physics Division , Bhabha Atomic Research Centre , Mumbai 400085 , India.
Langmuir. 2019 May 21;35(20):6683-6692. doi: 10.1021/acs.langmuir.9b00815. Epub 2019 May 7.
Self-organization of nanoparticles into one-dimensional (1D) nanochains leads to new unpredicted physiochemical properties, which are further exploited to develop photonic or electronic devices. Thus, the controlled fabrication of 1D nanochains requires nanotemplate, which acts as building blocks for the self-assembly of nanoparticles. To address this issue, we designed a hydrotrope (sodium salicylate)-based CTAB/ n-hexanol/water/heptane reverse micellar system. Hydrotrope, herein, modulates electrostatic interactions between reverse micellar droplets and paves the way for the formation of self-assembled structures. Small-angle X-ray scattering studies were performed on the CTAB/heptane reverse micellar system by varying hydrotrope concentrations and water-to-surfactant ratios (W ) The aqueous content of the reverse micellar pool is determined from the W value, where W = [HO]/[CTAB] and [CTAB] = 0.05 M. SAXS studies were performed for CTAB/heptane reverse micellar systems at three different W values, that is, 6, 12, and 16 and represented by W, W, and W, respectively. All SAXS profiles were modeled with a spherical form factor and a Baxter sticky hard sphere structure factor. The interaction between droplets was predicted in terms of stickiness parameter. The effect of W on the formation of self-assembled structures and forces governing the assembly has been discussed in detail. For the W system, the electrostatic repulsion between reverse micellar droplets decreases, resulting in the formation of the 1D chain-like assembly of nanodroplets. In the case of the W system, the dual feature of the hydrotrope has been observed, it increases the size of the reverse micellar system and reduces electrostatic repulsion between droplets because of which the formation of chain-like assemblies cannot be determined with accuracy. For the W system, the decrease in micellar size with the increase in the hydrotrope concentration has been observed. Thus, our reverse micellar templates may provide a comprehensive method for the fabrication of high aspect ratio 1D nanochains of a variety of materials and harnessing their collective properties for magnetic, catalytic, and opto-electronic applications.
纳米颗粒自组装成一维（1D）纳米链会产生新的、意想不到的物理化学性质，这些性质可进一步用于开发光子或电子器件。因此，一维纳米链的可控制备需要纳米模板，它作为纳米颗粒自组装的构建单元。为了解决这个问题，我们设计了一种基于水溶助长剂（水杨酸钠）的CTAB/正己醇/水/庚烷反胶束体系。在此，水溶助长剂调节反胶束液滴之间的静电相互作用，并为自组装结构的形成铺平道路。通过改变水溶助长剂浓度和水与表面活性剂的比例（W），对CTAB/庚烷反胶束体系进行了小角X射线散射研究。反胶束池的含水量由W值确定，其中W = [H₂O]/[CTAB]且[CTAB] = 0.05 M。对CTAB/庚烷反胶束体系在三个不同的W值，即6、12和16下进行了SAXS研究，分别用W₆、W₁₂和W₁₆表示。所有SAXS图谱都用球形形状因子和巴克斯特粘性硬球结构因子进行建模。根据粘性参数预测了液滴之间的相互作用。详细讨论了W对自组装结构形成的影响以及控制组装的力。对于W₆体系，反胶束液滴之间的静电排斥力降低，导致形成纳米液滴的一维链状组装。在W₁₂体系的情况下，观察到了水溶助长剂的双重特性，它增加了反胶束体系的尺寸并降低了液滴之间的静电排斥力，因此无法准确确定链状组装的形成。对于W₁₆体系，观察到随着水溶助长剂浓度的增加胶束尺寸减小。因此，我们的反胶束模板可能为制备各种材料的高纵横比一维纳米链并利用其集体性质用于磁性、催化和光电子应用提供一种全面的方法。
