UT Arlington          The University of Texas at Arlington

                       Norma Tacconi

Analytical Chemistry

Research Associate Professor

Education and Experience:

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)
 

             Phone:
      (817) 272-5034

             FAX:
      (817) 272-3808

             E-Mail:
    ntacconi@uta.edu

                                                                                      
                                                                                      

Research Areas:

Semiconductor Nanostructures and 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).

Electrophoretically deposited polystyrene balls (left) and gold nanowires (right)

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.

The cover page of Chemistry of Materials, issue of 8/12/ 2003, illustrates our work on MHCF compounds.
 

 

 

 

 


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.

Publications:

Over 100 articles, 2 book chapters, and 6 review papers. The most recent representative publications are:

“Composite WO3-TiO2 Films Prepared by Pulsed Electrodeposition: Morphological Aspects and Electrochromic Behavior,” N.R. de Tacconi, C.R. Chenthamarakshan, K.L. Wouters, F.M. MacDonnell, K. Rajeshwar, J. Electroanal. Chem. 566 (2004) 249.

“Spatially Directed Electrosynthesis of Semiconductors for Photoelectrochemical Applications”, Current Opinion in Solid State & Materials Science, K. Rajeshwar, N.R. de Tacconi, C.R. Chenthamarakshan,  in press and available online 11 September 2004.

“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”, R. Konduri, N.R. de Tacconi, K. Rajeshwar, and F.M. MacDonnell, J. Am. Chem. Soc.126 (2004) 11621.

“Photoassited Deposition of Chalcogenide Semiconductors on the Titanium Dioxide Surface: Mechanistic and Other Aspects”, S. Somasundaram, C.R. Chenthamarakshan, N.R. de Tacconi, Y. Ming, K. Rajeshwar, Chem. Mater. 16 (2004) 3846.

“Pulsed Electrodeposition of WO3‑TiO2 Composite Films,” N.R. de Tacconi, C.R. Chenthamarakshan, K. Rajeshwar, T. Pauporté, D. Lincot, Electrochem. Communications 5 (2003) 221.

Review Article: “Metal Hexacyanoferrates: Electrosynthesis, In Situ Characterization, and Applications,” N.R. de Tacconi, K. Rajeshwar, R.O. Lezna, Chem. Mater. 15 (2003) 3046. This article is featured in the cover of Chemistry of Materials.

“Cathodic Electrodeposition of Mixed Oxide Thin Films,” T. Pauporté, A. Goux, A. Khan-Harari, N.R. de Tacconi, C.R. Chenthamarakshan, K. Rajeshwar, D. Lincot, J. Phys. Chem. Solids 64 (2003) 1737.

“Electrochromic Behavior of WO3, TiO2 and WO3-TiO2 Composite Films Prepared by Pulsed Electrodeposition” N.R. de Tacconi, C.R. Chenthamarakshan, K. Rajeshwar, in “Electrochromic Materials and Applications”, A. Rougier, D. Rauh, and G.A. Nazri (Eds.), Proc. Electrochem. Soc. PV 2003-17, pp. 28-39.

“Cobalt Hexacyanoferrate: Compound Stoichiometry, Infrared Spectroscopy, and Photoinduced Electron Transfer,” R.O. Lezna, R. Romagnoli, N.R. de Tacconi, K. Rajeshwar, J. Phys. Chem. B 106 (2002) 3612.

“Semiconductor Nanostructures in an Alumina Template Matrix: Micro- versus Macro-Scale Photoelectrochemical Behavior,” N.R. de Tacconi, K. Rajeshwar, Electrochim. Acta 47 (2002) 2603.

“Photoelectrochemistry of Indium Hexacyanoferrate-Titania Films,” N.R. de Tacconi, K. Rajeshwar, and R.O. Lezna, J. Electroanal. Chem. 500 (2001) 270.

Review Article: “Semiconductor-Based Composite Materials: Preparation, Properties, and Performance,” K. Rajeshwar, N.R. de Tacconi, C.R. Chenthamarakshan, Chem. Mater. 13 (2001) 2765. This article is featured in the cover of Chemistry of Materials.

“Photoelectrochemical Oxidation of Aqueous Sulfite on Ni-TiO2 Composite Film Electrodes”, N.R. de Tacconi, M. Mrkic, K. Rajeshwar, Langmuir 16 (2000) 8426.

“Surface Morphology/Composition and Photo-electrochemical Behavior of Metal-Semiconductor Composite Films”, N. R. de Tacconi, C. A. Boyle, K. Rajeshwar, Langmuir 16 (2000) 5672.

“Preparation, Photoelectrochemical Characterization, and Photoelectrochromic behavior of Metal Hexacyanoferrate-Titanium Dioxide Composite Films,” N. R. de Tacconi, K. Rajeshwar, R.O. Lezna, Electrochim. Acta 45 (2000) 3403.

“Electrosynthesis of Cadmium Selenide Films on a Selenium-Modified Gold Surface,” N. Myung, N.R. de Tacconi, K. Rajeshwar, Electrochem. Comm. 1 (1999) 42.

Book Chapter: “Semiconductor Nanocomposite Films for Photoelectrochemical Applications,” K. Rajeshwar, N.R. de Tacconi, in “ Interfacial Electrochemistry: Theory, Experiment, and Applications,” A. Wieckowski Ed., Marcel Dekker, New York, 1999, pp. 721-737.

“Photoelectrochemical Oxidation of Formate Ions on Nickel-Titanium Dioxide Nanocomposite Electrodes: Unusual High Current Doubling Yields and Manifestation of a Site Proximity Effect,” N.R. de Tacconi, H. Wenren, D. Mc Chesney, K. Rajeshwar, Langmuir 14 (1998) 2933.

“Electrosynthesis of Indium Sulphide on Sulfur-Modified Polycrystalline Gold Electrodes,” N.R. de Tacconi, K. Rajeshwar, J. Electroanal Chem. 444 (1998) 7-10.

“Photoelectrochromism in Chemically Modified Nickel-Titanium Dioxide Nanocomposite Films,” N.R. de Tacconi, J. Carmona, W. Balsam, K. Rajeshwar,  Chem. Mater. 10, (1998) 25-26.

“Chemically Modified Ni/TiO2 Nanocomposite Films: Charge Transfer from Photoexcited TiO2 Particles to Hexacyanoferrate Redox Centers within the Film and Unusual Photoelectrochemical Behavior,” N.R. de Tacconi, J. Carmona, K. Rajeshwar, J. Phys. Chem. B 101, (1997) 10151.

“Photoelectrochemical Behavior of Nanocomposite Films of Cadmium Sulfide or Titanium Dioxide and Nickel,” N.R. de Tacconi, H. Wenren, K. Rajeshwar, J. Electrochem. Soc. 144, (1997) 3159.

Book Chapter: “Electrodeposition and Characterization of Nanocrystalline Semiconductor Films,” K. Rajeshwar, N.R. de Tacconi in “Semiconductor Nanoclusters - Physical, Chemical and Catalytic Aspects”, P. V. Kamat and D. Meisel, Eds., Elsevier, Amsterdam, 1997, pp. 321-351.

 
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The University of Texas at Arlington
Arlington, Texas 76019-0065, USA

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