Physicochemical properties of interfacial water and aqueous buffer solutions on mechanical exfoliated graphene were investigated in order to evidence perturbations in the three-dimensional hydrogen-bonded network-water structure. Both optical emission spectra by laser scanning confocal microscopy and vibrational spectra by Raman spectroscopy show evidence of peak shifts for the graphene/liquid system in comparison with the graphene/air one. According to density functional theory (DFT) calculations, these spectral features are discussed in terms of the hydrogen bonding between water molecules and the one-atom-thick two-dimensional layers of sp2-bonded carbon, which induces disorder in the water clusters and interface hole transfer phenomena. Interactions between water molecules and the graphene surface result in substantial orientation of these hydrogen-bonded water molecules in the interfacial region. Moreover, DFT calculations clearly show an electron transfer from graphene to water molecules. The amount of charge increases when the number of water molecules onto surface increase. This is influenced by the presence of hydrogen bond between molecules. Calculated Raman spectra reflect the strength of interaction molecules – surface.

Water Structure and Charge Transfer Phenomena at Liquid–Graphene Interface

D'URSO, LUISA;SATRIANO, Cristina;FORTE, GIUSEPPE;COMPAGNINI, Giuseppe Romano
2012

Abstract

Physicochemical properties of interfacial water and aqueous buffer solutions on mechanical exfoliated graphene were investigated in order to evidence perturbations in the three-dimensional hydrogen-bonded network-water structure. Both optical emission spectra by laser scanning confocal microscopy and vibrational spectra by Raman spectroscopy show evidence of peak shifts for the graphene/liquid system in comparison with the graphene/air one. According to density functional theory (DFT) calculations, these spectral features are discussed in terms of the hydrogen bonding between water molecules and the one-atom-thick two-dimensional layers of sp2-bonded carbon, which induces disorder in the water clusters and interface hole transfer phenomena. Interactions between water molecules and the graphene surface result in substantial orientation of these hydrogen-bonded water molecules in the interfacial region. Moreover, DFT calculations clearly show an electron transfer from graphene to water molecules. The amount of charge increases when the number of water molecules onto surface increase. This is influenced by the presence of hydrogen bond between molecules. Calculated Raman spectra reflect the strength of interaction molecules – surface.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/111909
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