Papanikolas Group

Ultrafast Spectroscopy and Ultrafast Microscopy

Papanikolas Group

Ultrafast Spectroscopy and Ultrafast Microscopy

Ultrafast Dynamics in Molecular Materials for Solar Energy Conversion

Recently Published

Group Members

Light-Harvesting Assemblies

Thomas Meyer

Marcey Waters

John Reynolds

Kirk Schanze

Research Highlights

Solar fuels generation requires molecular assemblies that can perform multiple functions. In collaboration with the Schanze and Reynolds groups, we have examined the excited state dynamics of a functionalized polyfluorene polymer anchored to TiO2. The evolution of the transient spectra are followed across 8 decades of time, revealing that photexcitation of the Ru(II) complexes is followed by site-to-site energy transport, electron injection, and ultimately the transfer of the oxidative equivalent to the polymer backbone. The resulting charge separated state lives for about 100 usec. <Read>

A Raman-pump frequency modulation scheme and an automated signal-processing algorithm were developed for improved collection of time-resolved FSRS spectra. Together, these two advancements remove the broad background signals endemic to FSRS measurements and retrieve signals with high sensitivity. This FM-FSRS method was applied to the characterization of ultrafast energy transport in a OPE-TBT copolymer. Ultrafast energy transfer is monitored by the decay of donor vibrational modes and simultaneous growth of acceptor modes. <Read>

Observation of Combined Light-harvesting and Charge Separation in a Functionalized Assembly Bound to TiO2

In the beginning...

Ru(II)-Loaded Polystyrene

Early work in our lab examined assemblies consisting of 20 Ru(II) complexes linked together by a polystyrene scaffold. Using ultrafast absorption and emission methods we examined energy transport, triplet-triplet annihilation.

Energy Transfer in Folded Peptide Dimers

In collaboration with the Waters group, we have examined energy transfer in a coiled-coiled peptide dimer functionalized with a Ru(II) donor and and Os(II) acceptor. <Read>

Recent Review

Observation of excited state trapping in rigid environments. Implies side chain motion matters. <Read>

Experimental observation and modeling of site-to-site energy transport by Monte Carlo and stochastic kinetic simulations. <Read>

Characterized triplet-triplet annihilation process involving the interaction of multiple excited states on a single chain. <Read>

Ultrafast Dynamics
in Assemblies with Conjugated Backbones

Two recent publications appearing in J. Phys. Chem. Lett. explore competitive energy and electron transfer processes following photoexcitation of the polymer scaffold in macromolecular assemblies based on conjugated polymers (i.e. polyfluorene and P3HT).


Competitive energy and charge separation


Formation of long-lived charge separated state


Frequency-Modulated FSRS Spectroscopy Applied to Energy Transport in a Light-Harvesting Polymer


Papanikolas Group
Department of Chemistry
University of North Carolina at Chapel Hill