Biofunctionalization of Si(111)7×7 by “Renewable” l-Cysteine Transitional Layer

Abstract

Surface functionalization of an inorganic surface with bio-organic molecules is often aimed at creating a "permanent" bio-organic surface with receptor functional groups. We show here that L-cysteine can be used to transform a highly reactive Si(111)7×7 surface to not just a permanent bio-organic surface but also a semipermanent (or renewable) and a temporary bio-organic surfaces by manipulating the exposure. In the early growth stage, the strong bonding between the first cysteine adlayer and the Si substrate through Si-N or Si-S linkages in unidentate or bidentate arrangement provides permanent biofunctionalization by this interfacial layer. This interfacial layer can be used to build a transitional layer (second adlayer) mediated by interlayer vertical hydrogen bonding between an amino group and a carboxylic acid group. Further exposure of cysteine eventually leads to a zwitterionic multilayer film involving electrostatic interactions between cation (-NH3(+)) and anion moieties (-COO(-)). The interlayer hydrogen bonding therefore provides temporary trapping of bio-organic molecules as the second transitional layer that is stable up to 175 °C. This transitional layer can be easily removed by annealing above this temperature and then regenerated with the same molecular layer or a different one by "renewing" the interlayer hydrogen bonds. We also illustrate coverage-dependent adsorption structures of cysteine, from bidentate to unidentate attachments and to self-assembled multimers, involving formation of intralayer horizontal N···H-O hydrogen bonds, by combining our X-ray photoemission data with the local density-of-state images obtained by scanning tunnelling microscopy.

Adsorption and self-assembly of bio-organic molecules at model surfaces: A route towards increased complexity

“…1) To maintain an acceptable length, we are not going to discuss about AA adsorption on semiconducting surfaces, for which quite a lot of literature is already present [8][9][10][11][12][13]. Indeed the study of the interface between biomolecules and semiconducting surfaces is mainly motivated by the possible applications in molecular electronics and bio-compatible electronic devices, which would make the content of the present review diverge from its central focus.…”

Interface Electronic Structures of the L-Cysteine on Noble Metal Surfaces Studied by Ultraviolet Photoelectron Spectroscopy

“…Therefore, an understanding of the interaction of L-cysteine with metal surfaces is necessary. There have been experimental and theoretical research studies that examined the behavior of L-cysteine adsorbed on different faces of gold [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], silver [20][21][22][23], and copper [24][25][26] metallic single crystals as model systems for understanding the interaction of L-cysteine with metal surfaces and also L-cysteine adsorbed on some other surfaces considering technological interests [27][28][29][30][31][32][33][34][35]. In the experimental studies, the L-cysteine sample for investigation was formed using either the self-assembly or evaporation method.…”

One-step synthesis of chiral carbon quantum dots and their enantioselective recognition

“…Four fitted peaks located at 285.1 eV, 285.7 eV, 286.6 eV and 289 eV can be ascribed to the alkylcarbon atoms in C−S and C−N moieƟes, the linkage of carbon, the carboxyl or hydroxyl oxygen and the carbonyl C in the C=O group, respectively. 38,39 Fig. 3b shows the binding energies of N 1s.…”