Grafit elektrot üzerinde elektropolimerizasyon ile polianilin kopolimerlerinin sentezi, karakterizasyonu ve amperometrik biyosensör olarak uygulaması

HÜRKAN ÇATALKAYA

Grafit elektrot üzerinde elektropolimerizasyon ile polianilin kopolimerlerinin sentezi, karakterizasyonu ve amperometrik biyosensör olarak uygulaması

Thesis Type: Postgraduate

Institution Of The Thesis: Hacettepe Üniversitesi, Fen Bilimleri Enstitüsü, Kimya Mühendisliği A.B.D., Turkey

Approval Date: 2011

Thesis Language: Turkish

Student: HÜRKAN ÇATALKAYA

Principal Supervisor (For Co-Supervisor Theses): SELMA MUTLU

Open Archive Collection: AVESIS Open Access Collection

Abstract:

In this study, electrochemical synthesis of polyaniline derivatives providing catalytic oxidation of N,N-Dimethylaminomethyl ferrocene (DMAMFc) among mediator derivatives in neutral medium and bearing amine functionality for covalent immobilazation of enzyme is aimed. The synthesis, characterization and application as a biosensor of copolymers are presented within the scope of this thesis.For this purpose, copolymerization of aqueous solutions consisting of different proportions of orthanilic acide (o-ASA) and 2-aminobenzylamine (2-ABA) on graphite electrode has been carried out in the presence of perchloric acid electrolyte with cyclic voltammetry. Electrochemical characterization of copolymers are evaluated using obtained CV graphs. The efficiency of copolymers to catalyze redox reactions of DMAMFc in neutral media (pH7) is investigated by the obtained CV voltammograms.Comparing CV voltammograms of polyaniline and copolymer, an anodic shift is observed for the peak potential of the first redox process and cathodic shift is observed for the peak potential of the second redox process with respect to polyaniline. Besides, along with the increase of orthanilic acid concentration in synthesis medium, there has been observed an increase both in copolymerization rate and catalytic DMAMFc oxidation efficiency of obtained copolymer films. Oxidation and reduction potentials of DMAMFc on copolymer film surfaces is determined as 0.42 V and 0.30 V versus Ag/AgCl reference electrode. It is also observed that the monomer ratios used in electropolymerization medium do not cause shift in those oxidation and reduction potentials.After the immobilization of glucose oxidase (GOx) as a model enzyme, the performance of copolymer films synthesized on graphite electrode surface is examined as an anode in a glucose biosensor. It is observed that monomer ratios used in electropolymerization is directly effective both in the amount of adsorbed DMAMFc on copolymer films and in biosensor response taken against glucose. The responses taken against glucose by biosensor utilizing adsorped DMAMFc on films as mediator are measured under 0.40 V potential. Linear measurement range up to 10 mM glucose with 32.8 nA/mM sensitivity is obtained with copolymer film synthesized using high ratios of orthanilic acid. Systematically, when 2-aminobenzylamine ratio is increased and orthanilic acid is decreased, sensitivity is decreased while linear measure range is increased. It is defined as it follows: while o-ASA/2-ABA ratio is 3.1:1, linear range of measurement is 15 mM glucose with 8.2 nA/mM sensitivity and while o-ASA/2-ABA ratio is 1.18:1, linear range of measurement is 20 mM with 3.5 nA/mM sensitivity.Ultimately, the surface of prepared copolymers are characterized topographically and chemically by AFM, SEM and ATR/FT-IR techniques.In this study, it is concluded that polyanilin which is non-conductive in neutral medium can be used in biosensors via the improved conductivity in copolymers obtained from suitable aniline derivatives and the enhancement of catalytic oxidation properties of polyaniline on ferrocene derivative mediators.