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Prof.Dr.A.Sezai S ARAÇ Istanbul Technical University

Nanoscale Surface Characterizations of Modified Carbon Fibre Microelectrodes & Electrochemical Detection of Dopamine. Prof.Dr.A.Sezai S ARAÇ Istanbul Technical University Physical Chemistry &Polymer Science & Technology. Istanbul Technical University ELECTROPOL RESEARCH GROUP

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Prof.Dr.A.Sezai S ARAÇ Istanbul Technical University

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  1. Nanoscale Surface Characterizations of Modified Carbon FibreMicroelectrodes & ElectrochemicalDetection ofDopamine. Prof.Dr.A.Sezai SARAÇ Istanbul Technical University Physical Chemistry &Polymer Science & Technology

  2. Istanbul Technical University ELECTROPOL RESEARCH GROUP • http://www.kimya.itu.edu.tr/saraca/ • http://atlas.cc.itu.edu.tr/~sarac/ • Conductive Nanosize-polymeric Thin films ,Nanomodification (The efficiency: i.e., scan rate, scan number ,solvent ,feed ratio and morphology ) • Electrocoating of Heterocyclic conjugated monomers on Carbon Fiber by cyclic voltammetry. • Surface Characterizations • Electrochemical Impedance Spectroscopy: Film &double layer capacitance& charge transfer resistance • Microsensor ve Biosensor Applications • Electrochromic Applications • Carbon Fiber-Polymer Composites

  3. Prep.& charac. of neurotransmitter sensitive carbon fiber microelectrodes by coating with conjugated polymers CF -carbon fibers 5-7μ Electrochemical surface modification Electrocoating & surface charac. Biocompatible & electrochemically reversible microbiosensor A.S. Sarac, A. Bismarck, E. Kumru, J. Springer,Synth. Met. 123 (2001) 411 E.Kumru,J.Springer,A.S.Sarac,A.Bismarck.,  Synth. Met.  123(2001)391 Sarac et.al..,J.Nanosci.and Nanotech.10,(2005) 1677–1682

  4. foton iyon elektron Surface Analysispolymeric Thin Film ~10-100nm • Functionalities • FTIR-ATR • Raman ,FIBSIMS ,EDX,XPS • Morphologic • SEM • AFM • Cyclovoltammetric • Electrochem.Impedance Spectroscopy • POLYMERIC NANOSTRUCTURES. (Book Ch)“Nanoscale Characterization of Conductive Polymer Electrocoated Carbon Fiber Surface “A.Sezai SARACEditor,H. S. Nalwa,Amer. Sci.Pub. California, USA (2006) • “Electropolymerization” ,A.Sezai SARAC,Encyclopedia of Polymer Science and Technology ,3rd Ed. Ed.H. F. Mark John Wiley & Sons, New York (2005)

  5. a)Cyclic voltammogram(CV) Electrogrowth of 10 mM PProDOT-Me2 in 0,1 M Bu4NPF6/ACN scan rate:100 mV/s scan number: 40 th cycle on CFME Q=278.1 mC b) Polymer cycled at different scan rates (in Monomer -free electrolyte) in 0,1 M Bu4NPF6/ACN scan rate: 20-400 mV/s. PProDOT-Me2/CFME

  6. PProDOT-Me2 /CFME

  7. Nyquist & Bode Phase Plots (PProDOT-Me2)Electrochemical Impedance Spectroscopy HIGH CAPACITANCE

  8. Electroactive polycarbazole(PCz) film. SARAC,A.S ,Microelectronic Eng.83( 4-9) (2006) 1534-1537 SARAC,A.S.,ATES,M.,PARLAK,E.A.,J.Appl.Electrochem.(2006) in press

  9. Polycarbazole (PCz)/CFME 0.1MNaClO4/PC ip = (2.69 x 108) n3/2 A C D1/2ν1/2 Randles Selvic

  10. Multisweep cyclovoltammogram of electrochemical PCz growthin 1 mM Cz in 0.05M TEAP/ CH2Cl2 on a CFME, at scan rate of 40 mV/s. (inset: polymer growth single CF and 10single CFs)

  11. CV of PCz in monomer -free electrolyte (Doping-dedoping)at scan rate of 20 to 100mV/s. (inset: Current density vs. square root of scan ratefor PCz )

  12. Cv of PCz on CFME in monomer- free solutionfor different thickness of thin film: 5, 7 and 10 cycles. (at 60 mV/s)

  13. Ex-situ FTIR-ATR spectra of PCz electrografted CFME by 3 to 10 cycles.

  14. Ex-situ spectroelectrochemistry (FTIR-ATR) from FTIR-ATR of PCz with different cycles (C-C,C=C ,C-N)

  15. XPS high- resolution scan Core-level XPS spectra in the region of C 1s (a);N 1s (b) for polycarbazole on CF A.S.Sarac AS, T Syed, M Serantoni, J Henry, VJ Cunnane, JB McMonagle,Appl.Surface Sci.222(2004)148

  16. Morphology-Composition For copolymer PTSP/Cz= 10:1 NaClO4 /PC

  17. P[Cz-co-PTSP] [PTSP]/ [Cz ]= 100:1 in 0.1M NaClO4 /PC

  18. PTSP/Cz= 100:1 NaClO4 /PC

  19. PTSP/Cz= 200:1 in NaClO4 /PC

  20. FTIR-ATR (copolymer) Cz/pTSP=1:1 Cz/pTSP=1:100 Cz

  21. Multisweep voltamogram P(Cz) 0.1 M TEATFB / ACN -CFME. )Polycarbazole( 1 mM Cz-TEAP/DCM) AFM images : (a) uncoated carbon fiber, (b) Polycarbazole coated CF

  22. ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY Nyquist & Bode plots PCz s/CF TEAP/CH2Cl2, [0,01Hz-100kHz]

  23. SENSORp-aminophenol , 1 μM-100nM p-Aminophenol CF JAMAL,M., MAGNER,E., SARAC,A.S., Sensors and Actuators (2004) 97,59

  24. p-aminophenol p[NVCzVBSA1] ( □); p[NVCzVBSA2] (∆ ); p[CzMeTh] (o ); p[Cz] (×); untreated (◊ ).

  25. Redox Behavior of Dopamine Redox reaction between dopamine and modified CFME2 Molecular structure of the protonated dopamine1 • Venton, B.J. and Wightman, R. M., 2003. Psychoanalytical Electrochemistry: Dopamine and Behavior, Analytical Chemistry, • 414 – 421 A. • Chen, J. and Cha, C., 1999. Detection of dopamine in the presence of a large excess of ascorbic acid by using the powder • microelectrode technique, Journal of Electroanalytical Chemistry, 463, 93–99.

  26. Oxidation of Dopamine to Dopaminequinone Dopamine is an easily oxidizablebiological compound so it is electroactive. Dopamine oxidizes in solution at working electrode. The oxidized material gives up electrons which are collected by the working electrode (CFME) and generate a current flow through it. The detection of this current is the basis of the measurement method.

  27. needle-type disk shaped PCz and P(Cz-co-pTsp) microelectrodes & Sensor behavior against Dopamine • Electroactive area of the carbon fibre • ( ca. 5-7 µm)

  28. Amperometric change (chronopotentiometry) time response • Amperometric study for Calibration Curves; • addition of Dopamine 700 mV vs Ag/AgCl

  29. Dopamine calibration curves 700 mV vs Ag/AgCl Uncoated PCz in LiClO4/ACN PTsp/Cz (100:1) LiClO4/ACN

  30. DPVs (Diferential Pulse Voltammetric Determination of Dopamine ) 40 repetitive measurements for 44 µM dopamine Uncoated PCz in LiClO4/ACN PTsp/Cz (100:1) LiCLO4/ACN

  31. DPV response for five successive additions of 100 µM ascorbic acid (blue line) and an addition of 44 µM dopamine (red line) Uncoated PCz in LiClO4/ACN PTsp/Cz (100:1) LiClO4/ACN

  32. PPy & PCz/CFME Biosensor Electrodes Monomers : Carbazole [Cz] Carbazole-N-carbonyl chloride [CzCClO] 1-(2- Cynoethyl)pyrrole [CEP]

  33. PCz thin film coated /CFMECyclovoltammetric determination of Neurotransmitters(dopamine,ephinephrine)with to response 100 μM dopamine/buffer at scan rate of 10mV/s. (inset : 0.1 μM dopamine/buffer solution at scan rate of 1000 mV/s)

  34. current density vs. square root of scan rate : 100 to 2000 mV/s The scan rate dependence of the anodic and cathodic peak currents show a linear dependence for PCEP, indicating electrochemical process is not diffusion limited and is reversible even at high scan rates.

  35. current density vs concentration ofdopamine : 100 to 500 nM.

  36. current density from CV of response to dopamine vs. current density from CV of doping(before cycled at at scan rate of 60 mV/s in monomer- free solution )

  37. PCEP thin film coated /CFME Response of poly(1-(2-Cynoethyl)pyrrole) coated carbon fiber microelectrodes in 1mM Dopaminein phosphate buffer solution at 300 mV s-1. Electrodeposition of CEP 1-(2- Cynoethyl)pyrrole [CEP] PF6ˉ by potential scanning from a 10-3 M solution of monomer in 0.1 M TBAPF6 / Acetonitrile at 100 mV s-1 on carbon fiber micro-electrodes.(electrode area = 1.0x10-3 cm2)

  38. Electropolymerization BF4ˉ • PCEP in monomer free electrolyte • at scan rate of • 120mV/s • 140mV/s • 160mV/s • 180mV/s • 200 mV/s • 20mV/s • 40mV/s • 60mV/s • 80mV/s • 100 mV/s 805 mV 453 mV 884 mV 700 mV 606 mV • 5 mM CEP in 0.1M Et4NBF4/ACN • on a CFME (area ~0.001 cm2) • at scan rate of 100 mV/s 781 mV

  39. Investigation of Optimum Conditions Dopamine Biosensor • Electrolyte effect • Overoxidation and overoxidation time • Concentration of dopamine – Calibration curves

  40. 805 mV 221 mV 453 mV 200 mV 700 mV 72 mV 835 mV 135 mV 536 mV 676 mV Electrolyte Effect • 5 mM CEP • on a CFME (area ~0.001 cm2) • at scan rate of 100 mV/s 0.1 M Potassium Perchlorate [KClO4] Response to 10 mM Dopamine E = 65 mV 0.1M Tetraethyl ammonium tetrafloraborate [Et4NBF4] /ACN Response to 10 mM Dopamine E = 149 mV

  41. Overoxidation(doping) Effect E= 148mV Response to 10 mM Dopamine 20 times higher E= 151 mV The best time for overoxidation by chronoamperometry 300 s E= 122 mV

  42. Effect of Dopamine Concentration 10 -7 – 10 -3M Dopamine in pH=7.4 Buffer Solution Calibration Curve 0.54 mA R : 0.99906 • PCEP modified CFME prepared by • 5mM CEP in 0.1 M Et4NBF4/ACN • overoxidized at 300s

  43. Effect of Dopamine Concentration 10 -7 – 10 -3M Dopamine in pH=7.4 Buffer Solution Poly (Carbazole-N-Carbonyl Chloride) modified CFME E = 151 mV E = 98 mV Polycarbazole modified CFME Electropolymerization conditions of Polycarbazole and Poly (Carbazole-N-Carbonyl Chloride) are the same to PCEP.

  44. Conclusion • The suitable conditions were investigated for more sensitive and selective dopamine biosensor CFME: Potassium Perchlorate / ACN electrolyte solution Overoxidation for 300s • The polymer modified CFMEs prepared by all monomers used in this study response to dopamine in range of 10-7 to 10-3 M (after they were overoxidized). • Electropolymerization of 1-(2-Cyanoethyl)pyrrole monomer on CFME present well defined and reversible redox processes. • The electroactivity and well defined electrochemistry of PCEP on CFME (better than Pt )make possible using these electrodes to determine up to physiological concentration level.

  45. conclusions • CV,DPV • XPS • FTIR-ATR, Raman Spectroscopy • Electrochemical: Cyclovoltammetric Methods can be applied for the Nanoscale Charac. Conjugated Nanoscale Polymeric Films on Micron Sized Carbon Fibers(& thin films). • Electrochemical Impedance Spectroscopy can be applied to such films to obtain Charge Capacity of microelectrodes (films and interface) • Substituent ,solvent & electrolyte plays an important role on final properties

  46. acknowlegements • Dr.M.Serantoni ,Dr.A.M.S.Tofail -University of Limerick, • Dr.Schulz IDM-Teltow Germany • My Students: in Polymer Sci.& Tech.Grad.Prog • M.Ates ,Ph.D • F.C.Cebeci , Ph.D. • E.Alturk Parlak,Ph.D. • E.Ayaz , Msc. • A.Gencturk,MSc.

  47. Thank You Istanbul -Bosphorous(16 th Century) sarac@itu.edu.tr http://atlas.cc.itu.edu.tr/~sarac/ http://www.kimya.itu.edu.tr/saraca/

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