Nanoscale Surface Characterizations of Modified Carbon Fibre Microelectrodes

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

Istanbul Technical University o o Ø 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 ) Ø Ø Ø • • • 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

Prep. & charac. of neurotransmitter sensitive carbon fiber microelectrodes by coating with conjugated polymers CF -carbon fibers 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 5 -7μ

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

PPro. DOT-Me 2/CFME a)Cyclic voltammogram(CV) Electrogrowth of 10 m. M PPro. DOT -Me 2 in 0, 1 M Bu 4 NPF 6/ACN scan rate: 100 m. V/s scan number: 40 th cycle on CFME Q=278. 1 m. C b) Polymer cycled at different scan rates (in Monomer -free electrolyte) in 0, 1 M Bu 4 NPF 6/ACN scan rate: 20 -400 m. V/s.

PPro. DOT-Me 2 /CFME

Nyquist & Bode Phase Plots (PPro. DOT-Me 2) Electrochemical Impedance Spectroscopy HIGH CAPACITANCE

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

Polycarbazole (PCz)/CFME 0. 1 M Na. Cl. O 4/PC Randles Selvic ip = (2. 69 x 108) n 3/2 A C D 1/2 ν 1/2

Multisweep cyclovoltammogram of electrochemical PCz growth in 1 m. M Cz in 0. 05 M TEAP/ CH 2 Cl 2 on a CFME, at scan rate of 40 m. V/s. (inset: polymer growth single CF and 10 single CFs)

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

Cv of PCz on CFME in monomer- free solution for different thickness of thin film: 5, 7 and 10 cycles. (at 60 m. V/s)

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

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

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

Morphology. Composition For copolymer PTSP/Cz= 10: 1 Na. Cl. O 4 /PC

P[Cz-co-PTSP] [PTSP]/ [Cz ]= 100: 1 in 0. 1 M Na. Cl. O 4 /PC

PTSP/Cz= 100: 1 Na. Cl. O 4 /PC

PTSP/Cz= 200: 1 in Na. Cl. O 4 /PC

FTIR-ATR (copolymer) Cz/p. TSP=1: 100 Cz

Multisweep voltamogram P(Cz) 0. 1 M TEATFB / ACN -CFME. ) Polycarbazole( 1 m. M Cz-TEAP/DCM) AFM images : (a) uncoated carbon fiber, (b) Polycarbazole coated CF

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY Nyquist & Bode plots PCz s/CF TEAP/CH 2 Cl 2, [0, 01 Hz-100 k. Hz]

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

p-aminophenol p[NVCz. VBSA 1] ( □); p[NVCz. VBSA 2] (∆ ); p[Cz. Me. Th] (o ); p[Cz] (×); untreated (◊ ).

Redox Behavior of Dopamine Redox reaction between dopamine and modified CFME 2 Molecular structure of the protonated dopamine 1 1. Venton, B. J. and Wightman, R. M. , 2003. Psychoanalytical Electrochemistry: Dopamine and Behavior, Analytical Chemistry, 414 – 421 A. 2. Chen, J. and Cha, C. , 1999. Detection of dopamine in the presence of a large excess of ascorbic acid by using the powder 3. microelectrode technique, Journal of Electroanalytical Chemistry, 463, 93– 99.

Oxidation of Dopamine to Dopaminequinone Dopamine is an easily oxidizable biological 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.

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

Amperometric change (chronopotentiometry) time response Amperometric study for Calibration Curves; Ø addition of Dopamine 700 m. V vs Ag/Ag. Cl Ø

Dopamine calibration curves 700 m. V vs Ag/Ag. Cl Uncoated PCz in Li. Cl. O 4/ACN PTsp/Cz (100: 1) Li. Cl. O 4/ACN

DPVs (Diferential Pulse Voltammetric Determination of Dopamine ) 40 repetitive measurements for 44 µM dopamine Uncoated PCz in Li. Cl. O 4/ACN PTsp/Cz (100: 1) Li. CLO 4/ACN

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 Li. Cl. O 4/ACN PTsp/Cz (100: 1) Li. Cl. O 4/ACN

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

PCz thin film coated /CFME Cyclovoltammetric determination of Neurotransmitters (dopamine, ephinephrine) with to response 100 μM dopamine/buffer at scan rate of 10 m. V/s. (inset : 0. 1 μM dopamine/buffer solution at scan rate of 1000 m. V/s)

current density vs. square root of scan rate : 100 to 2000 m. V/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.

current density vs concentration of dopamine : 100 to 500 n. M.

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

PCEP thin film coated /CFME Electrodeposition of CEP PF 6ˉ 1 -(2 Cynoethyl)pyrrole [CEP] by potential scanning from a 10 -3 M solution of monomer in 0. 1 M TBAPF 6 / Acetonitrile at 100 m. V s-1 on carbon fiber micro-electrodes. (electrode area = 1. 0 x 10 -3 cm 2) Response of poly(1 -(2 -Cynoethyl)pyrrole) coated carbon fiber microelectrodes in 1 m. M Dopamine in phosphate buffer solution at 300 m. V s-1.

Electropolymerization BF 4ˉ • PCEP in monomer free electrolyte at scan rate of 805 m. V 453 m. V 700 m. V • 20 m. V/s • 40 m. V/s • 60 m. V/s • 80 m. V/s • 100 m. V/s • 120 m. V/s • 140 m. V/s • 160 m. V/s • 180 m. V/s • 200 m. V/s 884 m. V 606 m. V • 5 m. M CEP in 0. 1 M Et 4 NBF 4/ACN • on a CFME (area ~0. 001 cm 2) • at scan rate of 100 m. V/s 781 m. V

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

Electrolyte Effect 221 m. V 805 m. V 453 m. V • 5 m. M CEP • on a CFME (area ~0. 001 cm 2) • at scan rate of 100 m. V/s 0. 1 M Potassium Perchlorate [KCl. O 4] 700 m. V 72 m. V Response to 10 m. M Dopamine E = 65 m. V 200 m. V 835 m. V 536 m. V 0. 1 M Tetraethyl ammonium tetrafloraborate [Et 4 NBF 4] /ACN Response to 10 m. M Dopamine E = 149 m. V 676 m. V 135 m. V

Overoxidation(doping) Effect E= 148 m. V Response to 10 m. M Dopamine E= 151 m. V The best time for overoxidation by chronoamperometry 300 s E= 122 m. V 20 times higher

Effect of Dopamine Concentration 0. 54 m. A 10 -7 – 10 -3 M Dopamine in p. H=7. 4 Buffer Solution Calibration Curve R : 0. 99906 • PCEP modified CFME prepared by • 5 m. M CEP in 0. 1 M Et 4 NBF 4/ACN overoxidized at 300 s

Effect of Dopamine Concentration 10 -7 – 10 -3 M Dopamine in p. H=7. 4 Buffer Solution E = 151 m. V Poly (Carbazole-N-Carbonyl Chloride) modified CFME E = 98 m. V Polycarbazole modified CFME Electropolymerization conditions of Polycarbazole and Poly (Carbazole-N-Carbonyl Chloride) are the same to PCEP.

Conclusion o o The suitable conditions were investigated for more sensitive and selective dopamine biosensor CFME: Potassium Perchlorate / ACN electrolyte solution Overoxidation for 300 s 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.

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

acknowlegements Ø Ø Ø Ø 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.

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/