TY - JOUR
T1 - Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods
AU - Aleeva, Yana
AU - Smecca, Emanuele
AU - Condorelli, Guglielmo Guido
AU - Fragalaì, Maria Elena
AU - Aleeva, Yana
AU - Motta, Alessandro
AU - Condorelli, Guglielmo Guido
AU - Motta, Alessandro
PY - 2013
Y1 - 2013
N2 - Metal oxides are versatile substrates for the design of a wide range of SAM-based organic-inorganic materials among which ZnO nanostructures modified with phosphonic SAM are promising semiconducting systems for applications in technological fields such as biosensing, photonics, and field-effect transistors (FET). Despite previous studies reported on various successful grafting approaches, issues regarding preferred anchoring modes of phosphonic acids and the role of a second reactive group (i.e., a carboxylic group) are still a matter of controversial interpretations. This paper reports on an experimental and theoretical study on the functionalization of ZnO nanorods with monofunctional alkylphosphonic and bifunctional carboxyalkylphosphonic acids. X-ray photoelectron and infrared spectroscopies have been combined with DFT modeling to explain and understand the interactions that drive the surface anchoring of phosphonic acids on ZnO surface. It was found that both monofunctional and bifunctional acids anchor on ZnO through a multidentate bonding which involves both P=O and P-O moieties of the phosphonic group. Moreover, anchored bifunctional acids bend to the surface, promoting a further interaction between surface hydroxyl groups and carboxylic terminations. This secondary interaction can be limited by increasing the surface density of the anchored molecules.
AB - Metal oxides are versatile substrates for the design of a wide range of SAM-based organic-inorganic materials among which ZnO nanostructures modified with phosphonic SAM are promising semiconducting systems for applications in technological fields such as biosensing, photonics, and field-effect transistors (FET). Despite previous studies reported on various successful grafting approaches, issues regarding preferred anchoring modes of phosphonic acids and the role of a second reactive group (i.e., a carboxylic group) are still a matter of controversial interpretations. This paper reports on an experimental and theoretical study on the functionalization of ZnO nanorods with monofunctional alkylphosphonic and bifunctional carboxyalkylphosphonic acids. X-ray photoelectron and infrared spectroscopies have been combined with DFT modeling to explain and understand the interactions that drive the surface anchoring of phosphonic acids on ZnO surface. It was found that both monofunctional and bifunctional acids anchor on ZnO through a multidentate bonding which involves both P=O and P-O moieties of the phosphonic group. Moreover, anchored bifunctional acids bend to the surface, promoting a further interaction between surface hydroxyl groups and carboxylic terminations. This secondary interaction can be limited by increasing the surface density of the anchored molecules.
KW - ALUMINUM
KW - MOLECULAR-ORBITAL METHODS
KW - NANOPARTICLES
KW - OXIDE SURFACES
KW - POLARIZABLE CONTINUUM MODEL
KW - RAY PHOTOELECTRON-SPECTROSCOPY
KW - SELF-ASSEMBLED MONOLAYERS
KW - SENSITIZED SOLAR-CELLS
KW - SURFACE FUNCTIONALIZATION
KW - ZINC-OXIDE
KW - ALUMINUM
KW - MOLECULAR-ORBITAL METHODS
KW - NANOPARTICLES
KW - OXIDE SURFACES
KW - POLARIZABLE CONTINUUM MODEL
KW - RAY PHOTOELECTRON-SPECTROSCOPY
KW - SELF-ASSEMBLED MONOLAYERS
KW - SENSITIZED SOLAR-CELLS
KW - SURFACE FUNCTIONALIZATION
KW - ZINC-OXIDE
UR - http://hdl.handle.net/10447/97150
M3 - Article
VL - 117
SP - 5364
EP - 5372
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
ER -