Proton Transfer Reactions on Semiconductor Surfaces

Abstract

The concept of proton affinity on semiconductor surfaces has been explored through an investigation of the chemistry of amines on the Ge(100)-2 x 1, Si(100)-2 x 1, and C(100)-2 x 1 surfaces. Multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy, temperature programmed desorption (TPD), and density functional theory (DFT) calculations were used in the studies. We find that methylamine, dimethylamine, and trimethylamine undergo molecular chemisorption on the Ge(100)-2 x 1 surface through the formation of Ge-N dative bonds. In contrast, primary and secondary amines react on the Si(100)-2 x 1 surface via N-H dissociation. Since N-H dissociation of amines at semiconductor surfaces mimics a proton-transfer reaction, the difference in chemical reactivities of the Ge(100)-2 x 1 and Si(100)-2 x 1 surfaces toward N-H dissociation can be interpreted as a decrease of proton affinity down a group in the periodic table. The trend in proton affinities of the two surfaces is explained in terms of thermodynamics and kinetics. Solid-state effects on the C(100)-2 x 1 surface and the surface proton affinity concept are discussed based on our theoretical predictions.

Attachment of Alanine and Arginine to the Ge(100)-2×1 Surface

“…The imine Ge-N dative bond length is intermediate between amine-like Ge-N dative bonds (2.13-2.18 Å) and a Ge-N covalent bond (1.7 Å). 18 The C-N a , C-N b , and C-N c bond lengths lie between the CdN double bond length (1.28 Å) and the C-N single bond length (1.4 Å) for both conformers. 12 The equivalent Figure 10.…”

“…For example, the energetics of the reactions of the common carbonyl, hydroxyl, and amine groups are almost identical to what has been calculated previously on the Si(100)-2×1 surface. 14,18 However, we also identified several mechanisms that had not been previously investigated, especially for the reactions of arginine and histidine. 12 We found that the imine group of arginine's guanidine side chain forms a strong "dative" bond where the imine lone pair acts as a Lewis base and the electrophilic "down" atom of the Si(100)-2×1 surface acts as a Lewis acid.…”

“…18,22 The amine dative bond is slightly stronger than the 21.7 kcal/mol carbonyl dative bond (Figure 3). Mui et al also reported adsorption energies for other Ge-N dative bonded states including acetonitrile, 2-propenenitrile, and 3-butenenitrile with energies of 11.1, 10.4, and 10.9 kcal/mol, respectively.…”

“…This approach has been found to reproduce experiment and the results of high level methods such as quadratic configuration interaction singles and doubles and connected triples (QCISD(T)) relatively accurately. 18 Energies reported herein are zero-point corrected. All calculations were performed using the Gaussian 03 software package.…”

First-principles study of trimethylamine adsorption on anatase TiO2 nanorod surfaces

“…A number of (mostly experimental) studies have been accomplished regarding the TMA molecular adsorption on the surfaces of several interesting materials like silicon [37][38][39][40], nickel [41], ruthenium [42] or platinum [43,44]. All these studies illustrate the tendency of the nitrogen atom in TMA to act as a Lewis base and form a dative bond with electron-withdrawing surface atoms.…”