Serdar Abaci

Investigation of some parameters influencing electrocrystallisation of PbO2

Abstract Optimum electrocrystallisation conditions of PbO2 have been investigated in acetonitrile by controlling experimental parameters such as water content, current density, electrolyte concentration, and acidity. It was determined that the crystallinity, conductivity and β-content of PbO2 films are highly dependent on these factors and that electrodeposition solution, which has 6 M water, 0.1 M lead perchlorate and no acid, gave the best crystalline PbO2 with 99% of β form. The conductivity value of this film was 6028 S/cm. All analyses were confirmed by XRD method

Carbon nanotube–chitosan modified disposable pencil graphite electrode for Vitamin B12 analysis

A single walled carbon nanotube-chitosan (SWCNT-chitosan) modified disposable pencil graphite electrode (PGE) was used in this study for the electrochemical detection of Vitamin B(12). Electrochemical behaviors of SWCNT-chitosan PGE and chitosan modified PGE were compared by using cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. SWCNT-chitosan modified electrode was also used for the quantification of Vitamin B(12) in pharmaceutical products. The results show that this electrode system is suitable for sensitive Vitamin B(12) analysis giving good recovery results. The surface morphologies of the SWCNT-chitosan PGE, chitosan modified PGE and unmodified PGE were characterized by using scanning electron microscopy (SEM).

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1).

Tin oxide nanoparticles-polymer modified single-use sensors for electrochemical monitoring of label-free DNA hybridization.

In this study, SnO(2) nanoparticles (SNPs)-poly(vinylferrocenium) (PVF(+)) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences.

Characterization of redox polymer based electrode and electrochemical behavior for DNA detection

Characterization of redox polymer, poly(vinylferrocenium) perchlorate (PVF+ClO4-) coated as a film on Pt electrodes, and the detection of DNA based on the electrochemical behavior of the polymer were described in this study. PVF+ClO4- modified electrodes were prepared by the electrooxidation of poly(vinylferrocene) (PVF), and DNA immobilized polymer modified electrode was then prepared. The characterization of the polymer modified electrodes were performed by scanning tunneling microscopy (STM), Raman spectroscopy and alternating current (AC) impedance. The effects of DNA concentration, pH, and polymer films in various thicknesses based on the electrode response were also investigated. The electrochemical behavior of DNA modified polymer electrode by using double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) was compared. DNA hybridization was also investigated.

Determination of Hg2+ on poly(vinylferrocenium) (PVF+)-modified platinum electrode.

A new surface based on poly(vinylferrocenium) (PVF(+))-modified platinum electrode was developed for determination of Hg(2+) ions in aqueous solutions. The polymer was electrodeposited on platinum electrode by constant potential electrolysis as PVF(+)ClO(4)(-). Cl(-) ions were then attached to the polymer matrix by anion exchange and the modified electrode was dipped into Hg(2+) solution. Hg(2+) was preconcentrated at the polymer matrix by adsorption and also complexation reaction with Cl(-). Detection of Hg(2+) was carried out by differential pulse anodic stripping voltammetry (DPASV) after reduction of Hg(2+). Mercury ions as low as 5 x 10(-10)M could be detected with the prepared electrode and the relative standard deviation was calculated as 6.35% at 1 x 10(-6)M concentration (n=6). Interferences of Ag(+), Pb(2+) and Fe(3+) ions were also studied at two different concentration ratios with respect to Hg(2+). The developed electrode was applied to the determination of Hg(2+) in water samples.

Electrosynthesis of 4,4′-dinitroazobenzene on PbO2 electrodes

Parameters which affect the electrosynthesis of 4,4′-dinitroazobenzene from p-nitroaniline on platinum and PbO2 electrodes were investigated and optimum conditions were determined. Maximum conversion efficiency for electrosynthesis was 95% with a pure β-PbO2 electrode. It was found that the electrocatalytic activity of a PbO2 electrode depends upon its α/β ratio and its degree of crystallinity. The effects of the added base and water on the conversion efficiency were also elucidated.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability.

Peptide nanoparticles (PNPs) modified disposable platform for sensitive electrochemical cytosensing of DLD-1 cancer cells

A novel diphenylalaninamid (FFA) based peptide nanoparticles (PNPs) modified pencil graphite electrodes (PGEs) for construction of electrochemical cytosensor was demonstrated for the first time in this study. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed the spherical nanostructure of the synthesized FFA based PNPs while attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectra provided information about the structure and conformation of proteins in their structure. Self-assembly of PNPs on PGE surface and adhesion of DLD-1 cancer cells on this surface was also characterized by electrochemical measurements. PNP/PGEs acted as a sensitive platform for simple and rapid quantification of low concentration of DLD-1 cancer cells in early diagnosis using the electrochemical impedance method (EIS). The offered cytosensor demonstrated outstanding performance for the detection of DLD-1 cells by the EIS method. The impedance of electronic transduction was associated with the amount of the immobilized cells ranging from 2 × 102 to 2.0 × 105 cellsmL-1 with a limit of detection of 100 cellsmL-1. The efficient performance of the cytosensor was attributed to the well-defined nanostructure and biocompability of PNPs on the substrate.

Electrochemical characterization of redox polymer modified electrode developed for monitoring of adenine

Electrochemical characterization of redox polymer for monitoring of adenine was described in this study using poly(vinylferrocenium) (PVF(+)) modified platinum (Pt) electrode. Scanning electron microscope (SEM) was used for the surface characterization. The electrochemical behaviors of polymer modified and adenine immobilized polymer modified electrodes were investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In order to obtain more sensitive and improved electrochemical signals, analytical parameters such as the effects of polymeric film thickness, immobilization time of adenine, pH and adenine concentration were examined on the response of the polymer modified electrode. Alternating current (AC) impedance spectroscopy was used for the characterization of polymer modified and adenine immobilized polymer modified electrodes. The effect of possible interferents on the response of the electrode was examined.