Preparation and Characterization of Self-Assembled Monolayers on Indium Tin Oxide

Abstract

Self-assembly of amphiphilic molecules, alkanethiols CH3(CH2) n SH (n = 15, 17), carboxylic acids CH3(CH2) n COOH (n = 16, 18) and bifunctional SH(CH2)15COOH on indium tin oxide (ITO) surfaces was investigated by X-ray photoelectron and near edge X-ray absorption fine structure spectroscopies, contact angle measurements, and atomic force microscopy. These molecules were found to form homogeneous, well-oriented monolayers on ITO. XPS indicates that at low coverages, thiol molecules adsorb as thiolates, whereas at saturation coverage ∼30% of the molecules adsorb as unbound thiols. From NEXAFS, we determined average alkyl chain tilts of 33° for thiol from the neat liquid, 44° for thiols prepared via CVD, 38° for carboxylic acids from hexadecane, and 43° for COOH(CH2)15SH from ethanol. Adsorption from a mixed hexadecane solution results in a preferred adsorption of carboxylic acids over thiol. Thus, COOH(CH2)15SH is found to bind to ITO via the carboxylic acids, forming a thiol-terminated SAM.

Modification of ITO surface using aromatic small molecules with carboxylic acid groups for OLED applications

“…Three peaks at 529.9, 531.1 and 533.6 eV are assigned to O 2− , carbonyl group (C O), and (C-O) or Sn-O, respectively [46][47][48]. In ITO films, the low binding energy O 1s component at 529.9 eV is attributed to oxygen in the form of oxide, O 2− present on ITO surface [49,50]. Carbonyl group (C O) peak is the strongest signal among them.…”

Quartz crystal microbalance in clinical application

“…They also have been used as an ideal model to investigate the effects of intermolecular interactions in the molecular assembly systems (Schertel et al, 1995;Yan et al, 2000;Himmel et al, 1997;Jung et al, 1998). SAMs have been traditionally prepared by immersing a substrate into a solution containing a ligand that is reactive to the substrate surface or by exposing the substrate to the vapor of the reactive species.…”

Comparative Study of Tetrahydrothiophene and Thiophene Self Assembled Monolayers on Au(111): Structure and Molecular Orientation

“…So far, molecular orientations of various SAMs have been determined using the polarization dependence of the NEXAFS spectra. [23][24][25][26][27] In addition, the C K-edge NEXAFS can provide information about the local unoccupied orbital structure of the carbon-containing group in a molecule. This means that the change of the electronic structure of the five-membered ring resulting from adsorption on the metal can be examined by NEXAFS spectroscopy.…”