Aqueous-based colloidal synthesis using alkyltrimethylammonium bromide (C_nTABr), a cationic surfactant, has attracted much attention recently as a simple and facile method to fabricate size- and shape-tunable metal nanoparticles. Despite the many related studies, however, the underlying synthesis mechanism and the exact role of the cationic surfactant have not yet been clarified. Here, we report how the size of Pt nanoparticles varies by using a wide range of chain lengths (n = 10, 12, 14, 16, and 18) and concentrations (0.005 to 0.18 M) of C_nTABr in aqueous-based colloidal synthesis. Highly monodisperse Pt particles with a size between 8 and 26 nm were obtained and confirmed by TEM analysis. Significantly, unlike other surfactants, when C_nTABr with a small chain length was used, the particle size increased with the concentration, which is different from the typical particle growth behavior by other surfactants. The UV-vis spectroscopy analysis results show that the chemical affinity between real precursors and micelles generated in solution is an important factor in determining the size of the Pt nanoparticles. Based on this insight, we successfully demonstrated that the particle size is also controllable by modifying the critical micelle concentration with a KBr additive. Our results provide useful guidelines for nanoparticle synthesis using cationic surfactants.

中文翻译：

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用阳离子表面活性剂C _n TABr †控制Pt纳米颗粒的尺寸

最近，使用烷基三甲基溴化铵（C _n TABr）（一种阳离子表面活性剂）的水基胶体合成作为制备尺寸和形状可调的金属纳米粒子的一种简便方法而受到了广泛关注。尽管有许多相关研究，但是，尚不清楚阳离子表面活性剂的潜在合成机理和确切作用。在这里，我们报告了水基胶体中的C _n TABr的链长范围（n = 10、12、14、16和18）和浓度（0.005至0.18 M），Pt纳米颗粒的尺寸如何变化合成。获得尺寸在8至26nm之间的高度单分散的Pt颗粒，并通过TEM分析证实。明显地，与其他表面活性剂不同，当C _n使用链长小的TABr，粒径随浓度增加而增加，这与其他表面活性剂的典型颗粒生长行为不同。紫外可见光谱分析结果表明，溶液中生成的实际前体与胶束之间的化学亲和力是决定Pt纳米粒子尺寸的重要因素。基于此见解，我们成功地证明了通过用KBr添加剂修改临界胶束浓度也可以控制粒径。我们的结果为使用阳离子表面活性剂合成纳米颗粒提供了有用的指导。