Adsorption of Azobenzene on Hexagonal Boron Nitride Nanomesh Supported by Rh(111).

Á Szitás,Z Kónya,T Ajtai,R Gubó,L Óvári,A Berkó,T Pásztor,K Palotás,A P Farkas

doi:10.1021/acs.jpcc.0c01725

Abstract

Adsorption properties of azobenzene, the prototypical molecular switch, were investigated on a hexagonal boron nitride (h-BN) monolayer (“nanomesh”) prepared on Rh(111). The h-BN layer was produced by decomposing borazine (B3N3H6) at 1000–1050 K. Temperature-programmed desorption (TPD) studies revealed that azobenzene molecules adsorbed on the “wire” and “pore” regions desorb at slightly different temperatures. Angle-resolved high-resolution electron energy loss spectroscopy (HREELS) measurements demonstrated that the first molecular layer is characterized predominantly by an adsorption geometry with the molecular plane parallel to the surface. Scanning tunneling microscopy (STM) indicated a clear preference for adsorption in the pores, manifesting a templating effect, but in some cases one-dimensional molecular stripes also form, implying attractive molecule–molecule interaction. Density functional theory (DFT) calculations provided further details regarding the adsorption energetics and bonding and confirmed the experimental findings that the molecules adsorb with the phenyl rings parallel to the surface, preferentially in the pores, and indicated also the presence of an attractive molecule–molecule interaction.

Highlights

The discovery of the fascinating properties of graphene, including its self-supporting nature and exceptional electronic properties,[1,2] solicited vivid interest in other two-dimensional (2D) materials as well.[3−7] Atomically thin hexagonal boron nitride (h-BN) has been thoroughly investigated.[5−7] It is isostructural and isoelectronic to graphene, but the difference in electronegativity results in an insulating character with an electronic band gap of about 6 eV
Recent studies demonstrated that h-BN alone or decorated with small Au nanoparticles is a highly selective catalyst in oxidative dehydrogenation or partial oxidation reactions.[10−12] h-BN monolayers have been “bottom-up” synthesized relatively on metal single-crystal surfaces of hexagonal symmetry[13−22] and on rectangular ones like Pd(110),[23] as well as on bcc(110) surfaces, typically using borazine (B3N3H6).[6,24]
We report on the adsorption of azobenzene (C6H5N = NC6H5), a prototypical molecular switch,[41−44] which was not yet studied on h-BN prepared on metal single crystals

Summary

Introduction

The discovery of the fascinating properties of graphene, including its self-supporting nature and exceptional electronic properties,[1,2] solicited vivid interest in other two-dimensional (2D) materials as well.[3−7] Atomically thin hexagonal boron nitride (h-BN) has been thoroughly investigated.[5−7] It is isostructural and isoelectronic to graphene, but the difference in electronegativity results in an insulating character with an electronic band gap of about 6 eV It has high chemical and thermal stability and a high predicted thermal conductivity.[8] Quite importantly, 2D hexagonal boron nitride is an excellent support and an ideal spacer for graphene-like nanoand optoelectronics.[6,9] Besides, recent studies demonstrated that h-BN alone or decorated with small Au nanoparticles is a highly selective catalyst in oxidative dehydrogenation or partial oxidation reactions.[10−12] h-BN monolayers have been “bottom-up” synthesized relatively on metal single-crystal surfaces of hexagonal symmetry[13−22] and on rectangular ones like Pd(110),[23] as well as on bcc(110) surfaces, typically using borazine (B3N3H6).[6,24] The morphology of the h-BN layer is determined by lattice mismatch and the strength of interaction between the nitride and the metal. The periodically undulating h-BN monolayer formed on Rh(111) can be used as a template for the preparation of metal nanoparticles and related heterostructures.[33−35]

Objectives

Methods

Results

Conclusion