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Layer‐by‐Layer Assemblies of Catechol‐Functionalized TiO 2 Nanoparticles and Porphyrins through Electrostatic Interactions
Author(s) -
Burger Alexandra,
Costa Rubén D.,
Lobaz Volodymyr,
Peukert Wolfgang,
Guldi Dirk M.,
Hirsch Andreas
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405039
Subject(s) - surface modification , zeta potential , porphyrin , nanoparticle , thermogravimetric analysis , materials science , layer by layer , dynamic light scattering , chemical engineering , contact angle , layer (electronics) , photochemistry , chemistry , nanotechnology , organic chemistry , engineering , composite material
In the current work, we present the successful functionalization and stabilization of P‐25 TiO 2 nanoparticles by means of N1,N7‐bis(3‐(4‐ tert ‐butyl‐pyridium‐methyl)phenyl)‐4‐(3‐(3‐(4‐ tert ‐butyl‐pyridinium‐methyl)phenylamino)‐3‐oxopropyl)‐4‐(3,4‐dihydroxybenzamido)heptanediamide tribromide ( 1 ). The design of the latter is aimed at nanoparticle functionalization and stabilization with organic building blocks. On one hand, 1 features a catechol anchor to enable its covalent grafting onto the TiO 2 surface, and on the other hand, positively charged pyridine groups at its periphery to prevent TiO 2 agglomeration through electrostatic repulsion. The success of functionalization and stabilization was corroborated by thermogravimetric analysis, dynamic light‐scattering, and zeta potential measurements. As a complement to this, the formation of layer‐by‐layer assemblies, which are governed by electrostatic interactions, by alternate deposition of functionalized TiO 2 nanoparticles and two negatively charged porphyrin derivatives, that is, 5,10,15,20‐(phenoxyacetic acid)‐porphyrin ( 2 ) and 5,10,15,20‐(4‐(2‐ethoxycarbonyl)‐4‐(2‐phenoxyacetamido)heptanedioic acid)‐porphyrin ( 3 ), is documented. To this end, the layer‐by‐layer deposition is monitored by UV/Vis spectroscopy, scanning electron microscopy, ellipsometry, and profilometry techniques. The resulting assemblies are utilized for the construction and testing of novel solar cells. From stable and repeatable photocurrents generated during several “on‐off” cycles of illumination, we derive monochromatic incident photo‐to‐current conversion efficiencies of around 3 %.