Latest Work

1. Solar cells made of ZnO Nanowires and TiO₂ Nanotubes Electrodes.

Recent work has involved so-called one-dimensional (1-D) nanostructured metal oxide morphologies that are used to prepare new types of electrodes,including ZnO nanowires or TiO₂ nanotubes,that have the shape of nail-beds. This highly interdisciplinary work has been conducted with the groups of Lu (Rutgers-New Brunswick) and Rajeshwar (UT Arlington),respectively. Galoppini’s group designed  chromophores that can help physical chemists to better understand the electronic processes that are specific to such 1-D morphologies.

I could be demonstrated (in collaboration with Lu and Hagfeldt) in a the first study that electrons in solar cells prepared from ZnO nanowires electrodes travel faster than in electrodes prepared from spherical nanoparticles. This is an important property that had been proposed,but not demonstrated,before.The study of solar cells prepared from porphyrins bound to nanotube electrodes demonstrated the importance of dye design and pointed to key dye characteristics that can lead to increased efficiencies.

Photoelectrochemical Behavior of Polychelate Porphyrin Chromophores and Titanium Dioxide Nanotube Arrays for Dye-Sensitized Solar Cells Norma R. de Tacconi,Wilaiwan Chanmanee,Krishnan Rajeshwar,Jonathan Rochford,Elena Galoppini J. Phys. Chem. C 2009,113,2996–3006.

2. Zinc Oxide Nanowires Sensors.

Highly ordered,vertically aligned nail-bed morphologies are promising materials not only for solar energy conversion,but also for the development of new,multifunctional,miniaturized sensors.  The nature of the surface and the interactions between biomolecules,and new semiconductor layers are little understood. Lu and Galoppini have developed the first  stepwise methodology to produce stable  attachment and more clearly defined interfacial chemistry for biomolecules. In particular,a DNA strand was immobilized on ZnO nanowire sensors and hybridized with complementary DNA.

Stepwise Functionalization of ZnO Nanotips with DNA Olena Taratula,Elena Galoppini,Richard Mendelsohn,Pavel Ivanoff Reyes,Zheng Zhang,Ziqing Duan,Jian Zhong,Yicheng Lu  Langmuir 2009,25,2107-2113

3. Encapsulation Of Dyes Into A Macrocyclic Host.

More recently the Galoppini group has explored new methods to interface molecules and semiconductors.  A new approach was used to anchor a redox-active compound to the semiconductor surface,i.e encapsulation into a macrocyclic host that binds to the surface. An new generation of model dyes was designed to provide insulation from local heterogeneity and improved binding control to semiconductor surfaces. in addition,the group is designing new supramolecular vehicles for intracellular drug delivery and imaging targeted to cancer cells.

Cucurbituryl Complexes of Viologens Bound to TiO₂ Films Marina Freitag and Elena Galoppini,Langmuir,2010,26,8262–8269.

4. Synthesis of Strapped Porphyrins:Towards Insulation of the Chromophore on Semiconductor Surfaces.

Strapped porphyrins,designed to bind planar to the semiconductor surface,were synthesized as model dyes for the study of sensitization processes on metal oxide semiconductor nanoparticles surfaces (TiO₂,and ZrO₂). The strap was added to limit or prevent porphyrin-porphyrin stacking and contacts with the semiconductor,while the tether provides a constraint on the orientation of the anchoring groups.

5. Synthesis of ”Star” complexes.

With the Meyer group we are studying a series of homoleptic “star-shaped”  Ru complexes for insulation of the chromophoric unit on the surface of semiconductor. This class of compounds could shed light or the role of the iodide/triiodide  couple in solar cells.