Professor

B.S. (1982), Lehigh University
Ph.D. (1988) Princeton University
Postdoctoral Fellow (1988-1990) University of Rochester

OFFICE
Beury Hall 346

MAILING ADDRESS
Department of Chemistry
Beury Hall 130
1901 N. 13th Street
Philadelphia, PA 19122

PHONE
office: 215-204-5203
fax: 215-204-1532
lab: 215-204-4744

E-MAIL
spano@temple.edu

RESEARCH GROUP

http://astro.temple.edu/~spano/

Computational / Photonics / Physical

Research Interests

Optical Excitations in Conjugated Oligomer and Polymer Aggregates and Films

Optical excitations in polymers and polymer films is a robust field, with progress and advances fueled by the promising commercial applications of polymer-based or plastic optical devices such as organic light-emitting diodes. Despite an enormous amount of primarily experimental research, there are significant gaps in our understanding of how such devices absorb and emit light. The goal of this research is to unravel the influences of intermolecular or excitonic interactions, exciton-vibrational coupling and structural defects on linearly and circularly polarized absorption, photoluminescence and electroluminescence in oligomer and polymer aggregates. The current focus is on aggregates, films and crystals of polyarenes as well as substituted and unsubstituted oligomers of poly-p-phenylene vinylene (PPV), and poly-thiophene (PT), among the best candidates for optical device applications. Theoretical techniques are being developed to treat weak to strong exciton-phonon coupling involving several electronic transitions and several intramolecular vibrational modes in two dimensional herringbone and lamellar aggregates as well as one-dimensional chiral aggregates, which contain point and structural defects. The influence of intermolecular modes (lattice phonons) are also of interest in establishing temperature dependent properties. The methods developed to date have proved successful in explaining several unusual spectral features of tetracene [1] quaterthiophene [2] and distyrylbenzene [3-7] nanoaggregates, and have predicted a "recipe" for superradiant DSB aggregates [7]. Extensions to aggregates of larger oligomers and polymers are currently in progress. Plans are also underway to treat aggregates of cyano derivatives of oligo-phenylene vinylenes which have a layered packing arrangement promoting the formation of excimers.

Molecular Orientation and Quantum State Control

The ability to align or orient molecular species prior to reaction is one of the main goals in the field of chemical reaction dynamics. In a successful collaboration with A. Marjatta Lyyra in the Physics Department, our research groups investigated electromagnetically induced transparency in diatomic lithium, leading to a novel method for measuring transition dipole moments [8]. We also developed and demonstrated a three laser excitation scheme to selectively excite a target mJ level within a rovibronic level of a diatomic molecule [9]. This is equivalent to alignment of the angular momentum vector. My group is responsible for developing the theoretical machinery needed to predict new excitation schemes. The theory is based on equations of motion which describe how the multilevel molecular density matrix evolves under the influence of two or more laser fields. The theory has successfully predicted full mJ resolution in the three laser experiment [10] and is currently being applied to more general problems involving the control and manipulation of molecular eigenstates via a strong coupling laser.

[1] Sang-Hyun Lim, Thomas G. Bjorklund, Frank C. Spano and Christopher J. Bardeen, “Exciton Delocalization and Superradiance in Tetracene Thin Films and Nanoaggregates”. Phys. Rev. Lett. (in press).

[2] H. Sun, Z. Zhao, F. C. Spano, D. Beljonne, J. Cornil, Z. Shuai and J-L. Bredas, “Absorption and Emission in Quaterthienyl Thin Films,” Advanced Materials 15, 818 (2003).

[3] F. C. Spano, "The Fundamental Photophysics of Conjugated Oligomer Herringbone Aggregates", J. Chem. Phys. 118, 981 (2003).

[4] F. C. Spano, "Absorption and Emission oligo-Phenylene Vinylene Nanoaggregates: the Role of Disorder and Structural Defects", J. Chem. Phys. 116, 5877 (2002).

[5] F. C. Spano, "Absorption and Emission in Pinwheel Aggregates of oligo-Phenylene Vinylene Molecules", J. Chem. Phys. 114, 5376 (2001).

[6] F. C. Spano, "Absorption and Fluorescence in Distyrylbenzene Nanoaggregates", Syn. Met. 116, 337 (2001).

[7] F. C. Spano, "Emission from Aggregates of Oligo-phenylene vinylenes: A Recipe for Superradiant H-Aggregates", Chem. Phys. Lett. 331, 7 (2000).

[8] J. Qi, F. C. Spano, T. Kirova, A. Lazoudis, J. Magnes, L. Li, L. M. Narducci, R. W. Field, and A. M. Lyyra, “Measurement of Transition Dipole Moments in Lithium Dimers Using Electromagnetically Induced Transparency”, Phys. Rev. Lett., 88, (2002).

[9] J. Qi, G. Lazarov, X. Wang, L. Li, L. M. Narducci, A. M. Lyyra and F. C. Spano, "Autler-Townes Splitting in Molecular Lithium: Prospects for All-Optical Alignment of Nonpolar Molecules", Phys. Rev. Lett. 83 288 (1999).

[10] F. C. Spano, "Theory of Sub Doppler Autler-Townes Splitting in Molecules: Alignment and Orientation of the Angular Momentum in Nonpolar Molecules", J. Chem. Phys. 114, 276 (2001).

Selected Publications

Spano FC.; Meskers SCJ.; Hennebicq E. "Using circularly polarized luminescence to probe exciton coherence in disordered helical aggregates". Journal of Chemical Physics 129 (2): 024704 (2008).

Ahn TS.; Muller AM.; Al-Kaysi RO.; Spano FC. "Experimental and theoretical study of temperature dependent exciton delocalization and relaxation in anthracene thin films". Journal of Chemical Physics 128 (5): 054505, (2008).

Spano FC.; Silvestri L.; Spearman P. "Reclassifying exciton-phonon coupling in molecular aggregates: Evidence of strong nonadiabatic coupling in oligothiophene crystals". Journal of Chemical Physics 127 (18): 184703, (2008).

Spano FC.; Meskers SCJ.; Hennebicq E.; Beljonne D. "Probing excitation delocalization in supramolecular chiral stacks by means of circularly polarized light: Experiment and modeling". Journal of the American Chemical Society 129 (22): 7044-7054 (2007).

Clark J.; Silva C.; Friend RH.; Spano FC. "Role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene". Physical Review Letters 98 (20): 206506 (2007).

Zhao Z.; Spano FC. "Multiple mode exciton-phonon coupling: applications to photoluminescence in oligothiophene thin films".  Journal of Physical Chemistry C 111 (16): 6113-6123 (2007).

Spano FC. "Absorption in regio-regular poly(3-hexyl)thiophene thin films: Fermi resonances, interband coupling and disorder". Chemical Physics 325 (1): 22-35 (2006).

Spano FC. "Excitons in conjugated oligomer aggregates, films, and crystals". Annual Review of Physical Chemistry 57: 217-243 (2006).

Kirova T.; Spano FC . "Designing molecular eigenstates in a four-level Lambda system". Physical Review A 71 (6): Art. No. 063816 (2005).

Spano FC . "Modeling disorder in polymer aggregates: The optical spectroscopy of regioregular poly(3-hexylthiophene) thin films". Journal of Chemical Physics 122 (23): Art. No. 234701 (2005).

Zhao Z.; Spano FC . "Vibronic fine structure in the absorption spectrum of oligothiophene thin films". Journal of Chemical Physics 122 (11): Art. No. 114701 (2005).