Browsing by Author "Isildak, Ibrahim"

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Electrochemiluminescence Methods Using Cds Quantum Dots in Aptamer-Based Thrombin Biosensors: a Comparative Study
(Springer Wien, 2020) Isildak, Ibrahim; Navaeipour, Farzaneh; Afsharan, Hadi; Kanberoglu, Gulsah Soydan; Agir, Ismail; Ozer, Tugba; Khalilzadeh, Balal
The detection of thrombin by using CdS nanocrystals (CdS NCs), gold nanoparticles (AuNPs) and luminol is investigated in this work. Thrombin is detected by three methods. One is called the quenching method. It is based on the quenching effect of AuNPs on the yellow fluorescence of CdS NCs (with excitation/emission wavelengths of 355/550 nm) when placed adjacent to CdS NCs. The second method (called amplification method) is based on an amplification mechanism in which the plasmonics on the AuNPs enhance the emission of CdS NCs through distance related Forster resonance energy transfer (FRET). The third method is ratiometric and based on the emission by two luminophores, viz. CdS NCs and luminol. In this method, by increasing the concentration of thrombin, the intensity of CdS NCs decreases, while that of luminol increases. The results showed that ratiometric method was most sensitive (with an LOD of 500 fg.mL(-1)), followed by the amplification method (6.5 pg.mL(-1)) and the quenching method (92 pg.mL(-1)). Hence, the latter is less useful.
Flow Injection Potentiometric Determination of Silver(I) in Photographic Film Developing Solution Samples by Polyvinylchloride Membrane Silver(I) Selective Electrode
(Chem Soc Pakistan, 2016) Topcu, Cihan; Coldur, Fatih; Andac, Muberra; Cubuk, Osman; Kanberoglu, Gulsah Saydan; Caglar, Bulent; Isildak, Ibrahim
A polyvinylchloride (PVC) membrane silver(I) selective electrode was developed for the determination of silver(I) ions in photographic film developing solutions. The electrode was embedded into a home-made flow cell and successfully used as a potentiometric detector in a flow injection potentiometric (FIP) system. Under the optimized flow injection conditions, the electrode exhibited a non-Nernstian slope of 67.20 +/- 0.80 mV in the linear range from 1.0x10(-5) to 1.0x10(-1) mol/L (R-2 = 0.9961) and the lowest value for limit of detection (LOD) was calculated as 7.1x10(-6) mol/L. The electrode displayed good sensitivity, selectivity, repeatable and rapid response towards silver(I) ions. Lifetime of the electrode was determined as at least two months in FIP system. The electrode was also successfully applied for the potentiometric determination of silver(I) ions in photographic film developing solution samples in FIP system. The results attained from FIP system were compared with the atomic absorption spectrophotometry (AAS) results by using student's t-test at 95 % confidence level and relative deviation (RD) between the two methods was < 8 %.