Herein, we report the development of a simple liquid crystal (LC)-based droplet sensor for the specific detection of mercury ions (Hg²⁺) in an aqueous medium, using trimethyl octadecyl ammonium bromide (OTAB) and an Hg²⁺-binding aptamer. In terms of the mechanism, the system senses the homeotropic orientation of the LCs at the LC–aqueous interface that is induced by the self-assembled monolayer of positively charged OTAB molecules. In the absence of Hg²⁺, electrostatic interactions between the positively charged OTAB and negatively charged aptamer molecules disturb the organization of the OTAB monolayer, causing the LCs to adopt a planar orientation. By contrast, an aptamer hairpin structure formed in the presence of Hg²⁺ weakens the interactions between the OTAB and aptamer molecules, causing the OTAB monolayer to self-reassemble and the LCs to consequently adopt a homeotropic orientation. These LC orientational transitions are observable under a polarized optical microscope. This sensor had a low limit of detection of 100 and 250 pM for buffer and tap water samples, respectively. Therefore, our LC-based droplet sensor is a suitable platform for the simple, specific, and convenient detection of Hg²⁺ in an aqueous medium.

在本文中，我们报告了一种基于液晶（LC）的简单液滴传感器的开发，该传感器使用三甲基十八烷基溴化铵（OTAB）和Hg ²⁺结合剂专门检测水性介质中的汞离子（Hg ²⁺）适体。就机理而言，该系统可感测LC-水界面上LC的垂直取向，该界面由带正电的OTAB分子的自组装单分子层诱导。在没有Hg ²⁺的情况下，带正电的OTAB和带负电的适体分子之间的静电相互作用会干扰OTAB单层的组织，导致LC采用平面取向。相比之下，在Hg ²⁺存在下形成适体发夹结构弱化了OTAB和适体分子之间的相互作用，导致OTAB单层自重组装，LC则采用了垂直取向。这些LC取向转变在偏振光学显微镜下可观察到。该传感器的缓冲液和自来水样品的检测下限分别为100 pM和250 pM。因此，我们基于LC的液滴传感器是用于简单，特定和方便地检测水性介质中Hg ²⁺的合适平台。