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

Interfacial Dynamics

Charge separation is a key step in the conversion of sunlight into usable energy.  In the production of solar fuels by dye-sensitized photoelectrochemical cells (DSPECs), the charge separation event takes place when the photoexcited chromophore injects an electron into the conduction band of the metal oxide electrode.  We are using time-resolved spectroscopies to characterize the fundamental photophysical events  -- electron injection, energy transfer and electron transfer -- that take place following the excitation of chromophore-catalyst assemblies anchored to the surface of TiO2 and other metal oxides.  These projects involve collaborations with groups in the UNC EFRC (Meyer, Waters, Schanze and Reynolds) who are experts in the synthesis of the molecular materials.

Thomas Meyer

Marcey Waters

John Reynolds

Kirk Schanze

Research Highlights

Watching the First Photoactivation Step in a Chromophore Water-Oxidation Catalyst Assembly

We have used ultrafast absorption spectroscopy to examine the first photoactivation step in the water oxidation cycle of a chromophore-catalyst assembly bound to TiO2 using a bilayer-type architecture. Photoexcitation of the chromphore is followed by rapid excited state electron injection on the psec time scale. The oxidative equivalent is then transferred to the catalyst within 200 ps, with the charge separated state persisting for several microseconds. <Read>

Injection into Transparent Conducting Oxides

In collaboration with the Meyer group, we have examined the electron injection process into transparent conducting oxides. Application of an external bias provided control over the driving force for injection, which in turn enabled a quantitative analysis of the injection rates.

<Read>                   <Read>

Functionalized Peptides

Working with the Waters group, we have examined the excited state dynamics of two closely related oligoproline assemblies anchored to TiO2. One is a light-harvesting assembly, containing two chromophores, while the other contains a chromophore and a water oxidation catalyst. We have used time resolved spectroscopy to map out the fundamental energy and electron transfer events that follow photon absorption.

<Read>                  <Read>


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