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Molecular control over single-crystalline GaAs(hkl) surface electronic properties by using bio-thiols

Molecular control over single-crystalline GaAs(hkl) surface electronic properties by using bio-thiols. Project : PN-II-ID-PCE-2011-3-0304 PN-II-ID-PCE-2011-3-0304 Director project : Dr. Valentina Lazarescu. Project description.

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Molecular control over single-crystalline GaAs(hkl) surface electronic properties by using bio-thiols

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  1. Molecular control over single-crystalline GaAs(hkl) surface electronic properties by using bio-thiols Project: PN-II-ID-PCE-2011-3-0304PN-II-ID-PCE-2011-3-0304 Director project: Dr. Valentina Lazarescu

  2. Project description The project aims to explore the control exerted by the adsorbed cysteine over the electronic properties of the GaAs (hkl) surfaces. Beside the thiol group that binds to substrate with high affinity, this small highly polar molecule owns carboxyl and amino functional groups whose intramolecular and intermolecular interactions with themselves or other ions present in its environment play a key role in determining adsorbate conformation and overlayer structure. The complexity of the interfacial phenomena accompanying its binding to GaAs (hkl) requires an interdisciplinary approach. This is mainly achieved by correlating the information concerning the interplay of the semiconductor surface states- and field-effects supplied by electrochemical impedance spectroscopy with that referring to the changes in the surface chemistry furnished by XPS and surface morphology provided by the fractal analysis of the AFM / STM images. UV-VIS-NIR and IR spectroellipsometry investigations on the surface morphology are also considered. Special attention will be focused on pH and doping effects as well as on the influence exerted by the metal cations (e.g. Ca2+/Mg+/ Ni2+), anions (e.g. Cl-) and redox probes (e.g. Fe(CN)63-/4- on the electrochemical properties of the self-assembled monolayer of cysteine on GaAs(hkl) electrodes. Electrochemical response of the cysteine-modified GaAs (hkl) electrodes in the presence of two important neurotransmitters (dopamine / epinephrine) will be also examined.

  3. Main milestones: • 2012: Preparation of the cysteine modified GaAs(hkl) electrodes & exploration of pH- and doping-effects on the electrochemical behavior of the cysteine adsorbed on GaAs(hkl) electrodes • 2013: Examination of the influence exerted by metal cations (e.g. Ca2+/Mg2+/Ni2+), anions (e.g. Cl-) and redox probes (e.g. Fe(CN)63-/4-) on the electrochemical properties of the self-assembled monolayers of cysteine on GaAs(hkl) electrodes • 2014: Evaluation of the electrochemical response of the cysteine-modified GaAs(hkl) electrodes in the presence of two important neuro-transmitters (dopamine / epinephrine)

  4. Estimated Budget

  5. Preparation of GaAs(hkl) electrodes from n- and p-doped wafers Chemical modification of GaAs(hkl) electrodes with self-assembled monolayers (SAM) of cysteine Microstructural (STM/AFM, VASE, fractal analysis) investigations on GaAs(hkl) substrate before and after the chemical modification with cysteine Electrochemical investigations (CV, EIS) on pH-and doping-effects at cysteine-modified GaAs(hkl) electrodes XPS investigations on the chemical composition of the cysteine-modified electrodes after the electrochemical measurements Microstructural (STM/AFM, VASE, fractal analysis) investigations on the morphology of the cysteine-modified electrodes after the electrochemical measurements 2012: Objectives

  6. 2012: Working team • Dr. Mirela Enache • Dr. Loredana Preda • Dr. Ana Maria Toader • Dr. Mihai Anastasescu • Dr. Gianina Dobrescu • Dr. Sorana Ionescu (University of Bucharest) • Hermine Stroescu (PhD student) • Cornelia Penea (Technician)

  7. 2012: Scientific cooperation • INCFM- Bucharest: Dr. Mihail F. Lazarescu; Dr. Catalin Negrila(working electrode preparation and XPS investigations) • Instituto de Quimica Fisica “Rocasolano” – Madrid (Spain) Dr. Angel Cuesta (EC-STM investigations)

  8. 2012: Scientific outcome • (a) Papers 1. Ga and As Competition for Thiolate Formation at p-GaAs (111) L. Preda, C. Negrila, M. F. Lazarescu, M. Enache, M. Anastasescu, A. M. Toader, S. Ionescu, V. Lazarescu, Electrochim. Acta 104 (2013) 1-11; impact factor: 3.83) 2. pH effects on the self-assembled monolayers of L-Cysteine on p-GaAs (100) electrodes, M. Enache, A. M. Toader, M. Anastasescu, G. Dobrescu, C. Negrila, M. F. Lazarescu, V. Lazarescu (under preparation) • (b) Communications: 1. Self-assembled monolayers of L-cysteine on GaAs(100) electrodes, M. Enache, L. Preda, M. Anastasescu, C. Negrila, M.F. Lazarescu, V. Lazarescu, Third Regional Symposium on Electrochemistry: South-East Europe RSE-SEE, May 13-17, 2012, Bucharest, Romania 2. Potential-induced conformational changes in self-assembled monolayers of L-cysteine at p-GaAs(100) electrodes, M. Enache, L. Preda, V. Lazarescu, C. Negrila, M. F. Lazarescu, 222nd ECS Meeting PRIME 2012, Honolulu (SUA) 7-12 Oct. 2012 3. Molecular self-assembling control over the surface states and field-effects at n-GaAs(100) electrodes, V. Lazarescu, M. Enache, G. Dobrescu, M. Gartner, C. Negrila, M. F. Lazarescu, 222nd ECS Meeting PRIME 2012, Honolulu (SUA) 7-12 Oct. 2012.

  9. 2013: Objectives • Electrochemical investigations (CV,EIS) on the metallic cation effects • XPS investigations on the metallic cation effects • Microstructural investigations (AFM, Fractal Analysis) on the metallic cation effects • Electrochemical investigations (CV,EIS) on the anion effects • XPS investigations on the anion effects • Microstructural investigations (AFM, Fractal Analysis) on the cation effects

  10. 2013: Working team • Dr. Mirela Enache • Dr. Loredana Preda • Dr. Ana Maria Toader • Dr. Mihai Anastasescu • Dr. Gianina Dobrescu • Cornelia Penea (Technician)

  11. 2013: Scientific cooperation • INCFM- Bucharest: Dr. Mihail F. Lazarescu; Dr. Catalin Negrila(working electrode preparation and XPS investigations) • Universität Ulm, Institut für Theoretische Chemie: Dr. Elizabeth Santos (theoretical estimation of the cysteine-thiolate bonding at GaAs(100) substrates)

  12. 2013: Scientific outcome • (a) Papers 1. EIS investigations on the L-cysteine-thiolate self-assembled monolayers formed at p-GaAs (100) electrodes, Valentina Lazarescu, Mirela Enache, Mihai Anastasescu, Gianina Dobrescu, Catalin Negrila, Mihai Florin Lazarescu ( Electrochimica Acta, in print) • (b) Communications: 1. Ion Effects on self-assembled monolayers of L-cysteine on p-GaAs (100) Electrodes, M. Enache, M. Anastasescu, C. Negrila, M.F. Lazarescu, V. Lazarescu, Fourth Regional Symposium on Electrochemistry, South East Europe (RSE-SEE), Ljubljana, Slovenia, May, 26-30, 2013 • 2. EIS Investigations on the L-Cysteine-thiolate Self-Assembled Monolayers Formed at p-GaAs (100) Electrodes, Valentina Lazarescu, Mirela Enache, Mihai Anastasescu, Gianina Dobrescu, Catalin Negrila, Mihai Florin Lazarescu, 9th International Symposium on Electrochemical Impedance Spectroscopy (EIS2013) in Okinawa, Japan, June 16-21, 2013

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