Binding of Glycine and l-Cysteine on Si(111)-7×7

Abstract

The adsorption of glycine and l-cysteine on Si(111)-7 x 7 was investigated using high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS). The observation of the characteristic vibrational modes and electronic structures of NH3+ and COO- groups for physisorbed glycine (l-cysteine) demonstrates the formation of zwitterionic species in multilayers. For chemisorbed molecules, the appearance of nu(Si-H), nu(Si-O), and nu(C=Omicron) and the absence of nu(O-H) clearly indicate that glycine and l-cysteine dissociate to produce monodentate carboxylate adducts on Si(111)-7 x 7. XPS results further verified the coexistence of two chemisorption states for each amino acid, corresponding to a Si-NH-CH2-COO-Si [Si-NHCH(CH2SH)COO-Si] species with new sigma-linkages of Si-N and Si-O, and a NH2-CH2-COO-Si [NH2CH(CH2SH)COO-Si] product through the cleavage of the O-H bond, respectively. Glycine/Si(111)-7 x 7 and l-cysteine/Si(111)-7 x 7 can be viewed as model systems for further modification of Si surfaces with biological molecules.

The Adsorption Configuration of Valine on Ge(100)

“…By comparison to previous results, the peaks at 531.0 and 532.0 eV were assigned to the GeÀO and the ÀC=O features, respectively. [12,14,15,28] The N 1s and O 1s core-level spectral analyses are consistent with the interpretation of the Ge 3d spectrum. Together, the spectra provide key evidence that the adsorption structure of valine on the Ge(100) surface only proceeds via the "intrarow OÀH dissociated and N dative bonded structure", which agrees with previously determined adsorption structure of glycine on the Ge(100) surface.…”

Hydrogen-bond mediated transitional adlayer of glycine on Si(111)7×7 at room temperature

“…Single-side polished Si͑111͒ chips ͑11 ϫ 2 mm 2 , 0.3 mm thick͒, with a resistivity of 0.005 ⍀ cm ͑Virginia Semiconductors͒, were cleaned by first outgassing at 400°C overnight, followed by flash annealing at 1200°C several times ͑by direct-current heating͒, until no C contaminants were detectable by XPS and large-area terraces with the 7 ϫ 7 reconstruction were observed by SPM. 1,8,10,17 Given that the corresponding binding energy of the O 1s spectrum for the 960 s deposition is found to be consistent with that of carboxylate ͑COO − ͒ ͑see below͒, this glycine film exists predominantly in the zwitterionic form, as expected for glycine in the bulk state. During evaporation, the temperature of the effusion cell was kept at 140°C, leading to a partial pressure of 5.0ϫ 10 −9 Torr for the 30 amu mass fragment ͑corresponding to the base ion NH 2 CH 2 + of glycine͒, as registered by a quadrupole mass spectrometer.…”

“…[1][2][3][4][5][6][7][8][9][10] These studies focus specifically on interfacial bonding, conformation, thermal stability, self-assembly, and chirality of the amino acid films on various metal and oxide substrates. [1][2][3][4][5][6][7][8][9][10] These studies focus specifically on interfacial bonding, conformation, thermal stability, self-assembly, and chirality of the amino acid films on various metal and oxide substrates.…”

“…Depending on the nature and temperature of the substrate, glycine could bond to the substrate in several ways: ͑a͒ through the N lone pair of the amino group, 4 ͑b͒ with the N atom after one N-H bond cleavage, 10 ͑c͒ with one of the O atoms in unidentate coordination, or ͑d͒ with both O atoms in bidentate or bridging coordination after O-H bond cleavage. However, the transition from monolayer to multilayer is not well understood.…”

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…In a comparison study of glycine (NH 2 -CH 2 -COOH) and L-cystein (NH 2 -CH(CH 2 SH)-COOH) on Si(111)-7×7, Huang et al reported that O-H dissociation was observed in both cases; however, in addition, both aminoacids showed substantial amount of N-H dissociative products. Interestingly, the -SH functionality in L-cystein remains intact on this substrate [377]. [281].…”