Interactions involved in the adsorption of ethylene glycol and 2-hydroxyethoxide on the Au(111) surface: a Density Functional Theory study

Abstract

Context: The monolayers of ethylene glycol and 2-hydroxyethoxide on gold surfaces have been used in hybrid materials as biosensors. In this article, the adsorption of ethylene glycol and 2-hydroxyethoxide on the Au(111) surface was analyzed. For the first system, ethylene glycol on Au(111), there are Au $···$ O and Au $···$ H interactions. To the best of our knowledge, the Au $···$ H interaction has been overlooked until now. However, in this work, there is strong evidence that this interaction is important to stabilize the system. For the second system, the atomic interactions mentioned previously are also predicted, although there is an additional interaction between 2-hydroxyethoxide molecules. Such an interaction induces the link -O-H-O-, with high values of the electron density at the critical points of the corresponding bond path of the O-H interaction. These links suggest the forming of ethylene glycol chains.

Methods: The calculations were performed using two exchange-correlation functionals: BEEF-vdW and C09 $_x^{}$ -vdW; both functionals incorporate dispersion effects within the Kohn-Sham approach in Density Functional Theory as implemented in GPAW code and ASE computational packages. The contacts between the molecules considered in this article and the Au(111) surface were analyzed through the Quantum Theory of Atoms in Molecules implemented in GPUAM code.

Keywords: Au surface; DFT; Ethylene glycol degradation; QTAIM.

Fig. 1

Ethylene glycol adsorption on Au(111) for C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 2

Bond paths for ethylene glycol adsorption on Au(111) obtained by C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 3

Optimized structures for $\theta$=2/9 of HOCH$_2^{}$CH$_2^{}$O on Au(111) with C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 4

Bond paths for $\theta$=2/9 of HOCH$_2^{}$CH$_2^{}$O on Au(111) C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 5

Optimized structures for $\theta$=3/9 of HOCH$_2^{}$CH$_2^{}$O on Au(111) for C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 6

Bond paths for $\theta$=3/9 ML of HOCH$_2^{}$CH$_2^{}$O on Au(111) for C09$_x^{}$-vdW (left side) and BEEF-vdW (right side) exchange-correlation functionals

Fig. 7

Top view of non-covalent interactions analysis for different cover ($\theta$=2/9 ML left, $\theta$=3/9 ML right) of HOCH$_2^{}$CH$_2^{}$O with C09$_x^{}$-vdW, s=0.5 u.a