title: Spectroscopic and Structural Studies of a Surface Active Porphyrin in Solution and in Langmuir-Blodgett Films.
abstract: Controlling aggregation of the dual sensitizer-emitter (S-E) zinc tetraphenylporphyrin (ZnTPP) is an important consideration in solid state noncoherent photon upconversion (NCPU) applications. The Langmuir-Blodgett (LB) technique is a facile means of preparing ordered assemblies in thin films to study distance-dependent energy transfer processes in S-E systems and was used in this report to control the aggregation of a functionalized ZnTPP on solid substrates. This was achieved by synthetic addition of a short polar tail to one of the pendant phenyl rings in ZnTPP in order to make it surface active. The surface active ZnTPP derivative formed rigid films at the air-water interface and exhibited mean molecular areas consistent with approximately vertically oriented molecules under appropriate film compression. A red shift in the UV-vis spectra as well as unquenched fluorescence emission of the LB films indicated formation of well-ordered aggregates. However, NCPU, present in the solution phase, was not observed in the LB films, suggesting that NCPU from ZnTPP as a dual S-E required not just a controlled aggregation but a specific orientation of the molecules with respect to each other.
authors.affiliation: Department of Chemistry, University of Saskatchewan , 110 Science Place, Saskatoon, Saskatchewan Canada S7N 5C9.|Department of Chemistry, University of the Philippines Visayas , Miag-ao, Iloilo Philippines 5023.
authors.forename: Concepcion P
authors.initials: CP
authors.lastname: Ponce
authors.affiliation: Department of Chemistry, University of Saskatchewan , 110 Science Place, Saskatoon, Saskatchewan Canada S7N 5C9.
authors.forename: Hessamaddin Younesi
authors.initials: HY
authors.lastname: Araghi
authors.affiliation: Department of Chemistry, University of Saskatchewan , 110 Science Place, Saskatoon, Saskatchewan Canada S7N 5C9.
authors.forename: Neeraj K
authors.initials: NK
authors.lastname: Joshi
authors.affiliation: Department of Chemistry, University of Saskatchewan , 110 Science Place, Saskatoon, Saskatchewan Canada S7N 5C9.
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Steer
authors.affiliation: Department of Chemistry, University of Saskatchewan , 110 Science Place, Saskatoon, Saskatchewan Canada S7N 5C9.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Paige