| Three classes of chelating alkanethiols, (1) the 2-alkyl-2-methylpropane-1,3-dithiols (i.e., CH3(CH2)mC(CH3)[CH 2SH]2, where m = 7, 9, 11, 13, 15), (2) the 1,1,1-tris(mercaptomethyl)alkanes (i.e., CH3(CH2)mC[CH2SH] 3, where m = 9, 11, 13, 15), and (3) 2-hexadecylidenepropane-1,3-dithiol (i.e., CH3(CH2)14CH = C[CH2SH] 2), were synthesized and used to generate self-assembled monolayers (SAMs) on gold. The resulting monolayers were characterized by ellipsometry, contact angle goniometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). The data demonstrate that the packing density and the degree of conformational order of SAMs can be controlled in a systematic manner by manipulating the structure of the chelating alkanethiol adsorbates. Thermal desorption studies of the SAMs show that the chelate effect of these multidentate alkanethiols profoundly influences their thermal stabilities as SAMs. The use of loosely packed SAMs as intercalating hosts was explored using functionalized gold nanoparticles. |
