Department of Chemistry and Biochemistry
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- Daniel W. Armstrong
- William A. Baker
- Edward Bellion
- Alejandro Bugarin
- Saiful Chowdhury
- Purnendu (Sandy) K. Dasgupta
- Rasika Dias
- Ronald L. Elsenbaumer
- Frank W. Foss
- Robert F. Francis
- Jongyun Heo
- Junha Jeon
- Kayunta Johnson-Winters
- Peter Kroll
- Carl J. Lovely
- Frederick MacDonnell
- Subhrangsu S. Mandal
- Dennis S. Marynick
- Brad S. Pierce
- Martin Pomerantz
- Laszlo Prokai
- Krishnan Rajeshwar
- Jimmy R. Rogers
- Zoltan A. Schelly
- Kevin A. Schug
- E. Thomas Strom
- Norma Tacconi (Retired)
- Seiichiro Tanizaki
- Richard B. Timmons
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- Analytical Chemistry
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- ABOUT US
Norma Tacconi (Retired)
Electrochemistry / Materials
- Semiconductor nanostructures and nanocomposites for photovoltaic energy conversion.
- Molecular photocatalysts for solar hydrogen generation and CO2 reduction
- Photocatalytic deposition of noble metal nanoparticles on carbon black for fuel cell applications
- Dye-sensitized solar cells based on semiconductor nanotubes and nanorods
Semiconductor Nanostructures and Nanocomposites
Efforts are directed to the electrochemical growth of semiconductor nanostructures (nanotubes, nanorods) and nanocomposites (metal-semiconductor and semiconductor-semiconductor). TiO2 nanotube arrays (left image) are prepared under varying waveform voltages to control nanotube dimensions (length, diameter and wall thickness). An innovative cathodic electrosynthesis of Nb2O5 hexagonal nanorods (right image) has been recently developed. These nanorods can be chemically converted to nanotubes with tailored dimensions. Semiconductor-semiconductor nanocomposites, particularly WO3-TiO2 films, are prepared with different protocols: (a) nanoparticles of one oxide component embedded in the matrix of the other oxide, (b) both oxide components grown together through pulsed electrodeposition, and (c) TiO2 nanotubes arrays as template for WO3 electrodeposition. Each strategy is optimized for a specific performance in photoelectrochemical and/or photochromic applications. Applications of all these semiconductor nanostructures are focused on dye-sensitized solar cells, light-driven H2 generation and photoreduction of CO2
Photocatalytically Generated Electrocatalysts for Polymer Electrolyte Fuel Cells (PEFCs)
We have developed a heterogeneous photocatalytic method to prepare nanocomposite electrocatalysts containing noble metal nanoparticles (Pt, Au, Pd and a combination of them) dispersed on carbon black. The method uses a small loading of TiO2 nanoparticles (5-10 wt. %) that under light irradiation instigate the photodeposition of metal nanoparticles with diameters in 3- 5 nm range (dark spot in the annexed image) on carbon black (corrugated appearance). The electrocatalytic activity and durability of these materials are optimized at the lowest metal loading. Best performance for PEFC applications is obtained with bimetallic (Au-Pt) samples consisting of Pt “raspberry-like” morphology on Au nanoclusters. Other bimetallic (Pd-Pt) and trimetallic (Au-Pd-Pt) nanoclusters also dispersed on carbon black by the photocatalytic method are under current study.
Molecular Photocatalysts for Solar Hydrogen Generation and CO2 Reduction
These molecular photocatalysts are made of three components: a chromophore (typically Ru(bpy)32+ or Ru(phen)32+), a bridging acceptor ligand and a co-catalyst coupled to the ligand. The redox processes associated with the acceptor ligand need to be finely tuned for a targeted application. Linear and bent tatpp (tetraaza-tetrapyrido-pentacene) ligands are among several multi-electron acceptors under scrutiny and when linked to one or two Ru chromophores they become potential photocatalysts for relevant processes such as solar hydrogen generation and photoconversion of CO2 to useful fuels (methanol, methane). The mechanistic aspects of multi-electron reduction and protonation are addressed by combination of electrochemical and in situ spectroelectrochemical measurements. Inclusion of an extra metal center (co-catalysts) is also being pursued in this endeavor of solar hydrogen generation.
Other research interests:
- Electro- and photo-catalytic conversion of CO2 to useful fuels
- Hydrogen production from Lignite coal electrolysis
- Novel electrodeposition strategies of compound semiconductors (BiVO4, CdSe, CdTe, ZnSe, etc)
- Water photoelectrolysis using semiconductor nanocomposites
Studies focus on the development of new methods for preparing semiconductor nanostructures and nanocomposites (metal-semiconductor, semiconductor-semiconductor, and molecular compound-semiconductor). The fabrication of nanostructures uses template-directed electrodeposition and combines the choice of the template with the design of the fabrication steps, to control the dimensions and shapes of the resulting nanostructures (nanodots, nanowires, nanorods). Ordered layers of polystyrene balls and porous alumina membranes are versatile templates for creating semiconductor nanostructure arrays and metal-semiconductor nanowires. Other templates can be generated by lithography, and attempts to prepare semiconductor nanostructures by using a combination of lithography and electrodeposition are being pursued. The goal of this research is to evaluate the performance of the resulting nanostructures in photoelectrochemical, photocatalytic, and energy storage applications. Another related interesting research is the electrochemical growth of semiconductor- semiconductor nanocomposites. Currently, our efforts are focused in WO3-TiO2 films because these composites posses superior photoelectrochemical and photoelectrochromic performances relative to the component oxides themselves. They are prepared using two main strategies: (a) nanoparticles of one oxide component are embedded in the matrix of the other oxide, and (b) both oxide components are grown together through novel pulsed electrodeposition methods. For photoelectrochemical performance, the embedding of TiO2 nanoparticles in a WO3 matrix is so far the best option. For photoelectrochromic performance, best films come from pulsed electrodeposition in highly rich WO3 precursor solutions. Other studies are focused on the growth and optical/electrochemical characterization of II‑VI semiconductor nanowires. We will use different templates and a new electrochemical strategy that we have developed. It consists of two steps: (1) the initial surface modification of a gold substrate by the electrodeposition of the Group VI element (Se, S, or Te) up to a pre-selected thickness, (2) the cathodic stripping of the Group VI element film in a solution containing adjusted doses of Group II cations (Cd2+ or Zn2+). This method generates 1:1 stoichiometric films and avoids the excess of the Group VI elemental component, an inherent problem in the classical cathodic co-electrodeposition method. Metal Hexacyanoferrates: Electrosynthesis, In Situ Characterization and Application in Photoelectrochromic and Ion-Sensing Devices These research activities are focused on the electrochemical preparation and in situ characterization of Prussian blue analogues with the generic formula AhMk[Fe(CN)6]l.mH2O, where A is an alkali metal cation and M is a transition metal. We are working on metal hexacyanoferrate (MHCF) compounds derived from Cu, Pd, In, V, Co and Ni and characterizing them by voltammetry, scanning probe microscopies, spectroelectro- chemical methods and AC impedance spectroscopy. The complexity of the redox processes depends on the particular MHCF compound, the uptake or release of alkali cation from the film structure to maintain local charge neutrality, and the number of compound stoichiometries in the film. As recently reviewed by us, all these compounds have a wide range of applications because of their electrocatalytic, electrochromic, ion-exchange, ion-sensing, and photomagnetic properties. We envision using MHCF films for the generation of nanocomposite films with oxide semiconductor nanoparticles (TiO2, WO3). Potential applications of these nanocomposites are in photochromic and ion-sensing devices. Spectroelectrochemistry of Dinuclear Ru(II) Complexes Another very interesting research area is the spectroelectrochemical characterization of the bridged ruthenium dimers P and Q. Complex P is [(phen)2Ru(tatpp)Ru(phen)2]4+and complex Q is [(phen)2Ru(tatpq)Ru(phen)2]4+ (phen is 1,10-phenanthroline, tatpp is a tetraaza tetrapyrido pentacene and tatpq is tetraaza tetrapyrido pentacene quinone). Both complexes are photochemically active and the central ligand (tatpp or tatpq) is the site of multi-electron storage. In complex P, the tatpp ligand can accept up to four electrons to form P4- in three sequential and reversible steps in organic solvents. Even more important is that these three steps are being detected also in aqueous solutions and the electrochemical behavior matches the multi-electron photochemical activity of P in water. The solution pH plays a significant role in the protonation at the three reduction stages and new species such as HP-, H2P and H3P- are now formed. For complex Q even a larger number of reduced and protonated species are expected. The coupling of reduction and protonation is an essential feature in most natural light-activated energy-storing processes and these complexes may ultimately be capable of driving proton-coupled, multi-electron transfer reaction of the type desired for facile H2 production or O2 reduction.
Over 140 publications including 3 book chapters and 9 review/tutorial papers. The most recent representative publications are:
de Tacconi, N. R.; Rajeshwar, K.; Chanmanee, W.; Valluri, V.; Wampler, W. A.; Lin, W.-Y.; Nikiel, L. “Photocatalytically Generated Bimetallic (Pt-Au/C-TiO2) Electrocatalysts for Polymer Electrolyte Fuel Cell Applications” J. Electrochem. Soc. 2010, 157, B147.
Book Chapter: Schlesinger, T.E.; Rajeshwar, K.; de Tacconi N. R. Chapter 14: “Electrodeposition of Semiconductors” in “Modern Electroplating”, 5th Edition (M. Schlesinger editor), August 2010, ISBN: 978-0-470-16778-6.
de Tacconi, N. R.; Chanmanee, W.; Rajeshwar, K.; Rochford, J.; Galoppini, E. “Photoelectrochemical Behavior of Polychelate Porphyrin Chromophores and Titanium Dioxide Nanotube Arrays for Dye-Sensitized Solar Cells” J. Phys. Chem. C 2009, 113, 2996.
Tutorial Review: Rajeshwar, K.; de Tacconi, N. R. “Solution combustion synthesis of oxide semiconductors for solar energy conversion and environmental remediation” Chem. Soc. Rev. 2009, 38, 1984.
de Tacconi, N. R.; Lezna, R. O., Chitakunye, R.; MacDonnell, F. M. “Electroreduction of the Ruthenium Complex, [(bpy)2Ru(tatpp)]Cl2, in Water: Insights on the Mechanism of Multi-electron Reduction and Protonation of the Tatpp Acceptor Ligand as a Function of pH” Inorg. Chem. 2008, 47, 8847.
de Tacconi, N. R.; Chenthamarakshan, C. R.; Rajeshwar, K., Lin, W-Y.; Carlson, T. F.; Nikiel, L.; Wamper, W. A.; Sambandam , S.; Ramani, V. “Photocatalytically Generated Pt/C-TiO2 Electrocatalysts with Enhanced Catalyst Dispersion for Improved Membrane Durability in Polymer Electrolyte Fuel Cells” J. Electrochem. Soc. 2008, 155, B1102.
Chanmanee, W.; Watcharenwong, A.; Chenthamarakshan, C. R.; Kajitvichyanukul, P.; de Tacconi, N. R.; Rajeshwar, K. “Formation and Characterization of Self-Organized TiO2 Nanotube Arrays by Pulse Anodization” J. Am. Chem. Soc. 2008, 130, 965.
Morales, W.; Cason, M.; Aina, O.; de Tacconi, N. R.; Rajeshwar, K. “Combustion Synthesis and Characterization of Nanocrystalline WO3” J. Am. Chem. Soc. 2008, 130, 6318.
de Tacconi, N. R.; Chitakunye, R.; MacDonnell, F. M.; Lezna, R. O. “The Role of Monomers and Dimers in the Reduction of Ruthenium (II) Complexes of the Redox-Active tetraazatetarpyridopentacene Ligand” J. Phys. Chem A. 2008, 112, 497-507.
Wang, L.C.; de Tacconi, N.R.; Chenthamarakshan, C.R.; Rajeshwar, K.; Tao, M. “Electrodeposited Copper Oxide Films: Effect of Bath pH on Grain Orientation and Orientation-Dependent Interfacial Behavior” Thin Solid Films 2007, 515, 3090-3095.
de Tacconi, N. R.; Chenthamarakshan, C. R.; Yogeeswaran, G.; Watcharenwong, A.; de Zoysa, R.S.; Basit, N.A.; Rajeshwar, K. “Nanoporous TiO2 and WO3 Films by Anodization of Titanium and Tungsten Substrates: Influence of Process Variables on Morphology and Photoelectrochemical Response” J. Phys. Chem. B 2006, 110, 25347.
de Tacconi, N. R.; Rajeshwar, K.; Lezna, R. O. “Electrochemical Impedance Spectroscopy and UV-Visible Reflectance Spectroelectrochemistry of Cobalt Hexacyanoferrate Films” J. Electroanal. Chem. 2006, 587, 42.
Review Article: Wouters, K. L.; de Tacconi, N. R.; Konduri, R.; Lezna, R. O.; MacDonnell, F. M. “Driving Multi-Electron Reactions with Photons: Dinuclear Ruthenium Complexes Capable of Stepwise and Concerted Multi-Electron Reductions” Photosynthesis Research 2006, 87, 41-55.
de Tacconi, N. R.; Lezna, R. O.; Konduri, R.; Ongeri, F.; Rajeshwar, K.; MacDonnell, F.M. “Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)2Ru(tatpp)Ru(phen)2]Cl4, in Water: Proton-Coupled Sequential and Concerted Multi-Electron Reduction” Chem. Eur. J. 2005, 11, 4327. A frontispiece illustrates our article.
de Tacconi, N. R.; Chenthamarakshan, C.R.; Rajeshwar, K.; Tacconi, E. J. “Selenium-Modified Titanium Dioxide Photochemical Diode/Electrolyte Junctions: Photocatalytic and Electrochemical Preparation, Characterization, and Model Simulations” J. Phys. Chem. B 2005, 109, 11960.
Konduri, R.; de Tacconi, N.R.; Rajeshwar, K.; MacDonnell, F.M. “Multi-Electron Photoreduction of a Bridged Ruthenium Dimer, [(phen)2Ru(tatpp)Ru(phen)2][PF6]4: Aqueous Reactivity and Chemical and Spectroelectrochemical Identification of the Photoproducts” J. Am. Chem. Soc. 2004, 126, 11621.
Rajeshwar, K.; de Tacconi, N.R.; Chenthamarakshan, C.R. “Spatially Directed Electrosynthesis of Semiconductors for Photoelectrochemical Applications” Current Opinion in Solid State & Materials Science 2004, 8, 173.
Somasundaram, S.; Tacconi, Nathalie; Chenthamarakshan C.R.; Rajeshwar, K.; de Tacconi, N.R. “Photoelectrochemical Behavior of Composite Metal Oxide Semiconductor Films with a WO3 Matrix and Occluded P 25 TiO2 Particles” J. Electroanal. Chem. 2005, 577, 167.
de Tacconi, N.R.; Chenthamarakshan, C.R.; Wouters, K.L.; MacDonnell, F.M.; Rajeshwar, K. “Composite WO3‑TiO2 Films Prepared by Pulsed Electrodeposition: Morphological Aspects and Electrochromic Behavior” J. Electroanal. Chem. 2004, 566, 249.
Review Article: de Tacconi, N.R.; Rajeshwar, K.; Lezna, R.O. “Metal Hexacyanoferrates: Electrosynthesis, In Situ Characterization, and Applications”, Chem. Mater. 2003, 15, 3046. The cover page of “Chemistry of Materials” illustrates our article.
de Tacconi, N.R.; Chenthamarakshan, C.R.; Rajeshwar, K.; Pauporté, T.; Lincot, D. “Pulsed Electrodeposition of WO3‑TiO2 Composite Films” Electrochem. Commumications 2003, 5, 221.
Lezna, R.O.; Romagnoli, R.; de Tacconi, N.R.; Rajeshwar, K. “Cobalt Hexacyanoferrate: Compound Stoichiometry, Infrared Spectroscopy, and Photoinduced Electron Transfer” J. Phys. Chem. B 2002, 106, 3612.
de Tacconi, N.R.; Rajeshwar, K. “Semiconductor Nanostructures in an Alumina Template Matrix: Micro- versus Macro-Scale Photoelectrochemical Behavior”, Electrochim. Acta 2002, 47, 2603.
Review Article: Rajeshwar, K.; de Tacconi, N.R.; Chenthamarakshan, C.R. “Semiconductor-Based Composite Materials: Preparation, Properties, and Performance”, Chem. Mater. 2001, 13, 2765. The cover page of Chemistry of Materials illustrates our article.
B. S. University of La Plata (UNLP), Argentina
M. S. Physical Chemistry, UNLP, Argentina
Ph.D. Electrochemistry, Institute of Physical Chemistry (INIFTA), UNLP, Argentina
Postdoctoral Fellow: University of Paris VII, France
Visiting Scientist: University of Poitiers (France);
CNRS Bellevue (France);
University of Geneva (Switzerland);
ENSCP, Paris (France).
Associate Professor of Chemistry, UNLP
Independent Senior Scientist, INIFTA and National Research Council (CONICET)
Education and Training
University of La Plata, Argentina Chemistry BS 1970 University of La Plata Physical Chemistry MS 1972 INIFTA, University of La Plata Electrochemistry PhD 1975 University of Paris VII, France Electrochemistry PDF 78-79 University of Geneva, Switzerland Electrochemistry RF 83-84
Research Associate Professor Department of Chemistry and Biochemistry, 2004-present
University of Texas at Arlington Senior Research Scientist Department of Chemistry and Biochemistry, 1992-2004
University of Texas at Arlington Chemistry Lecturer Department of Chemistry and Biochemistry, 1994-1995
University of Texas at Arlington Independent Researcher Institute of Physical Chemistry (INIFTA), 1985-1991
University of La Plata, Argentina Professor of Chemistry Department of Chemistry, 1979-1991
University of La Plata, Argentina Associate Researcher Institute of Physical Chemistry (INIFTA), 1980-1983
University of La Plata, Argentina Assistant Researcher Institute of Physical Chemistry (INIFTA), 1976-1978
University of La Plata, Argentina
130-plus peer-review articles, 2 book chapters, 7 invited review articles and 2 pending patents. Research has been featured on the cover of prestigious journals.
Reviewer of several scientific journals (Journal of Physical Chemistry (A, B and C), Journal of the American Chemical Society, Chemistry of Materials, Journal of the Electrochemical Society, Journal of Electroanalytical Chemistry, Electrochimica Acta). Worked as Symposium Chair/Co-Chair in: i) Nanotechnology, Electrochemical Society 205th Meeting, San Antonio, May 2004; ii) Photoelectrochemistry, Photocatalysis and Photoactive Materials, Electrochemical Society, Honolulu, October 1999; iii) Solar Energy Conversion and Photoelectrochemical Processes based on Solid/Liquid Interfaces, Electrochemical Society 188th Meeting, Chicago, October 1995; iv) Iberian-American Soc. Electrochemistry, XVII Meeting, April 2006, La Plata, Argentina. Served in PhD and MS committees at UTA (as Graduate Faculty Member, 2006-present). Hosted several visits of high/magnet school students to Electrochemistry lab for hands-on research. Represented UTA Science/Engineering for recruiting minority students (LSAMP program) at U.T. El Paso 2005. Member of International Scientific Advisory Board of J. Arg. Chem. Soc. Web site: www.aqa.org.ar/analesi.htm.