Naik Parrikar Vishwaraj, Boranna Rakshith, Pahal Suman, Thondagere Nataraj Chandrika, Kogravalli Jagannath Ravi Prasad, Gurusiddappa R Prashanth, Bannur Nanjunda Shivananju
Department of Electronics and Communication Engineering, National Institute of Technology Goa, Cuncolim, Goa, India.
Department of Electronics and Computer Engineering, Shree Rayeshwar Institute of Engineering and Information Technology, Shiroda, Goa, India.
Commun Chem. 2025 Jul 19;8(1):208. doi: 10.1038/s42004-025-01602-2.
Polyelectrolyte multilayer (PEM) thin films, fabricated at nano-scale by Layer-by-Layer (LbL) self-assembly techniques, have diverse nanotechnology applications. Precise thickness measurement during layer buildup is crucial in controlling the thickness. In this work, we present a novel optical measurement technique for in-situ analysis of the PEM film build-up by utilizing Etched Fiber Bragg Gratings (EFBG)-based sensors to quantify the deposited thickness. PEM films were deposited over EFBG by alternative deposition of weak polyelectrolytes Poly(allylamine hydrochloride)(PAH) and Poly(acrylic acid)(PAA) with quantitative analysis of adsorption and desorption steps at varying pH conditions. Further, the desorption process was observed in detail at the sub-nanometer scale, with PAA exhibiting a linear desorption while PAH follows an exponential desorption. This validates the inter-diffusive behavior of the low molecular weight polyelectrolytes during the PEM buildup, not only during the adsorption process but also during the desorption process. Thus, EFBG could be utilized as a precision tool to extract fundamental information during individual PEM layer build-up, thereby fine-tuning the nano-scale architecture of multilayers.
通过逐层（LbL）自组装技术在纳米尺度制备的聚电解质多层（PEM）薄膜具有多种纳米技术应用。在层堆积过程中进行精确的厚度测量对于控制厚度至关重要。在这项工作中，我们提出了一种新颖的光学测量技术，用于通过利用基于蚀刻光纤布拉格光栅（EFBG）的传感器来原位分析PEM膜的堆积，以量化沉积厚度。通过交替沉积弱聚电解质聚（烯丙胺盐酸盐）（PAH）和聚（丙烯酸）（PAA），并在不同pH条件下对吸附和解吸步骤进行定量分析，在EFBG上沉积PEM膜。此外，在亚纳米尺度上详细观察了解吸过程，PAA表现出线性解吸，而PAH遵循指数解吸。这验证了低分子量聚电解质在PEM堆积过程中的相互扩散行为，不仅在吸附过程中，而且在解吸过程中。因此，EFBG可作为一种精密工具，在单个PEM层堆积过程中提取基本信息，从而微调多层膜的纳米级结构。
