NCAFM2023 Programme Booklet

Tuesday 1440 - 1500

DIRECT OBSERVATION OF WATER DIMERS INDUCING SURFACE CHIRAL INVERSION AND MISMATCHED H BONDING IN A DYNAMIC DNA BASE LAYER

Shuning, Cai (Presenting), Lauri Kurki, Chen Xu, Adam S. Foster, 1 Peter Liljeroth 1,*

1 Department of Applied Physics, Aalto University, 00076 Aalto, Finland *Corresponding author contact: peter.liljeroth@aalto.fi

Water dimers, composed of two water molecules held together by hydrogen bonds, play a crucial role in many biochemical and physical processes. Recent studies have revealed the anomalous properties of water dimers and their benchmark role in both experiment and theory. However, the observation of individual water dimers has been challenging due to the difficulty of separating and generating them at the single-molecule level. Here, we present a direct observation of water dimers within a dynamic 2D adenine layer on Ag(111) using low-temperature scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) with a CO tip. Our results show that these water dimers form spontaneously at room temperature, inducing a local surface chiral inversion in which neighboring homochiral adenine pairs become heterochiral. Additionally, a counterintuitive mismatched H-bond structure emerges, further stabilized by the linear non-planar configuration of the water dimer, as confirmed by density functional theory (DFT) calculations. This direct observation provides rare evidence of the potential role of individual water dimers in self-assembly and highlights the importance of water dimers in biological and physical systems. The ability to directly study water dimers through supramolecular networks offers insights into micro-hydration and potential applications of water dimers in various fields.

Fig. Schematic of the adsorption site change, the local chiral inversion (purple and pink color represent left and right handedness, respectively) and the counter-intuitive H-bond ’mismatch’ induced by the water dimers in a self-assembled adenine layer.

References [1] S, Cai et al., J. Am. Chem. Soc, 2022, 144 , 44, 20227

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