中文摘要：

三聚氰胺和蜜勒胺（即三聚氰胺的三聚体）均为合成石墨型氮化碳（g-C3N4）的前驱体分子,具有与不同相g-C3N4的结构基元类似的骨架结构。本文利用低温扫描隧道显微镜（STM）对比研究了三聚氰胺与蜜勒胺在Au（111）表面上的自组装结构,并对两种分子可能形成的氢键类型进行识别。研究发现,三聚氰胺在表面上仅有一种氢键方式,形成两种组装结构;而蜜勒胺却可以形成三种类型的氢键,并组装成六种有序结构,而且不同类型的氢键在表面的比例随着分子在表面覆盖度的变化而变化。特别的,有些氢键类型之间可以在探针作用下发生转变。这些研究结果将为利用氢键构建和调控表面功能性纳米结构提供新方法,同时也为研究g-C3N4的表面原位合成及相关理化性质打下基础。

英文摘要：

Melamine and melem molecules are widely used precursors for synthesizing graphitic carbon nitride （g-C3N4）, the latter also a hot two-dimensional material with photocatalytic applications. The molecular structures of both are respectively identical to the repeating units of two distinct g-C3N, phases. In this work, the adsorption and self-assembly of melamine and melem on an Au（111） surface were investigated with low-temperature scanning tunneling microscopy （STM）. Particularly, the patterns of hydrogen bonds （HBs） in their assemblies were identified and compared. It was found that melamine can only form one type of HB and two kinds of assembly structures, whereas melem can form three types of HBs and six kinds of assembly structures in total. Moreover, the involved HBs can be transformed by tip manipulation. These findings may provide a new strategy for tuning the functionality of surface self-assemblies by manipulating intermolecular hydrogen bonds. This also paves a route for the in situ synthesis of g-C3N4 on metallic surfaces and subsequent investigations of their physicochemical properties.