Structure of thiocyanate adlayers on Rh(111): an in situ STM study

In situ scanning tunneling microscopy (STM) was used to examine the structure of thiocyanate adlayers specifically adsorbed on Rh(111) in solutions of potassium hydroxide and perchloric acid, both containing potassium thiocyanate (KSCN). An atomically flat terrace-step structure was consistently observed on Rh(111) surfaces prepared by the flame-annealing-quenching method. The Rh(111)-(1 × 1) atomic structure was discerned on the atomically flat terrace even in the alkaline solution. High-resolution STM images disclosed two different structures of the SCN⁻ adlayers, () and (2 × 2), in the alkaline and the acidic media, respectively. In each structure, an individual adsorbed SCN⁻ ion appeared as a single spot with a constant corrugation height in STM images, suggesting that SCN⁻ ions adsorbed predominantly with their S-ends at particular bonding sites on Rh(111). The difference in the adlayer structure in the two solutions can be attributed to the interaction between adsorbed SCN⁻ and coadsorbed K⁺ in the alkaline solution, and is different from that between adsorbed SCN⁻ and H⁺ in the acidic solution. Received: 26 February 1997 / Accepted: 3 March 1997     

薄膜基荧光气体传感器中的涂层化学

近年来,高性能薄膜基气体传感器的研制备受关注,所涉及的涂层化学已经成为物理化学学科发展的一个热点。传感因分析物与敏感层(涂层)物质相互作用引起薄膜特定静态及动态物理量变化而实现,因此,薄膜传感性能势必受到敏感层物质种类和敏感层微纳结构等因素影响。就薄膜基荧光传感而言,荧光敏感物质的结构和性质对薄膜传感性能起着至关重要的作用。同时,因毛细凝结、色谱效应、尺寸效应、分子间相互作用等因素的存在,敏感层微观结构也极大地影响着薄膜的传感性能。本文结合课题组近期研究工作,简要讨论薄膜基荧光气体传感器研究中的涂层化学基本问题,以及相关薄膜基荧光传感器在隐藏爆炸物、毒品、挥发性有机污染物检测/监测等方面的应用探索。最后,文章展望了薄膜基荧光气体传感器的发展前景和所面临的主要挑战。     

Fast and Selective Luminescent Sensing by Langmuir–Schaeffer Films Based on Controlled Assembly of Perylene Bisimide Modified with A Cyclometalated AuIII Complex

Condensed films of functional luminophores dominated by the magnitude and dimensionality of the intermolecular interactions play important roles in sensing performance. However, controlling the molecular assembly and regulating photophysical properties remain challenging. In this study, a new luminophore, ortho-PBI-Au, was synthesized by anchoring a cyclometalated alkynyl-gold(III) unit at the ortho-position of perylene bisimide. An unprecedented T-type packing model driven by weak Au-π interaction and Au−H bonds was observed, laying foundation for striking properties of the luminophore. Controlled assembly of ortho-PBI-Au at the air-water interface, realized using the classical Langmuir–Schaeffer technique, afforded the obtained luminescent films with different packing structures. With an optimized film, sensitive, selective, and rapid detection of a hazardous new psychoactive substance, phenylethylamine (PEA), was achieved. The detection limit, response time, and recovery time were <4 ppb, <1 s, and <5 s, respectively, surpassing the performance of the PEA sensors known thus far. The relationship between the characters of films and the sensing performance was systematically examined by grey relational analysis (GRA). The present study suggests that designing novel molecular aggregation with definite adlayer structure is a crucial strategy to enhance the sensing performance, which could be favorable for the film-based fluorescent sensors.