Cetyltrimethylammonium bromide (CTAB)-stabilized low-aspect ratio gold nanorods have been synthesized using seed-mediated wet chemical approach. Freshly cleaved highly oriented pyrolytic graphite (HOPG) surface is used as a substrate for the deposition of nanoparticles via the droplet drying technique. Owing to the presence of CTAB molecules in suspension, nanoparticles on the non-wetting HOPG surface get deposited in the form of a coffee-stain ring. Such deposits at various positions of the coffee-stain ring have been characterized by scanning helium ion microscopy (HIM) and atomic force microscopy (AFM). Besides the assembly of nanoparticles, AFM is specially employed to investigate the deposition of CTAB molecules. The deposition and distribution of nanoparticles are studied and quantified at various positions of the coffee-stain ring. On flat HOPG terraces, HIM shows merely the deposits of the gold nanostructures whereas AFM reveals both nanoparticles and CTAB deposits over the surface. This research study primarily focused on the nanoparticle deposits within the coffee-stain ring formed over the non-wetting HOPG terraces.

中文翻译：

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金纳米粒子在 HOPG 平台上的咖啡渍环中的沉积和分布

使用种子介导的湿化学方法合成了十六烷基三甲基溴化铵 (CTAB) 稳定的低纵横比金纳米棒。新切割的高取向热解石墨 (HOPG) 表面用作通过液滴干燥技术沉积纳米颗粒的基材。由于 CTAB 分子在悬浮液中的存在，非润湿 HOPG 表面上的纳米颗粒以咖啡染色环的形式沉积。这种在咖啡渍环不同位置的沉积物已经通过扫描氦离子显微镜 (HIM) 和原子力显微镜 (AFM) 进行了表征。除了纳米粒子的组装，AFM 还专门用于研究 CTAB 分子的沉积。在咖啡渍环的不同位置研究和量化纳米颗粒的沉积和分布。在平坦的 HOPG 平台上，HIM 仅显示金纳米结构的沉积物，而 AFM 显示表面上的纳米颗粒和 CTAB 沉积物。这项研究主要集中在非润湿 HOPG 梯田上形成的咖啡渍环内的纳米颗粒沉积物。