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KAHRAMAN, MEMET VEZİR

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KAHRAMAN

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MEMET VEZİR

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2022 - 20232
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Subject: Doğa Bilimleri Genel ×

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Now showing 1 - 2 of 2
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    PublicationOpen Access
    A novel polymeric fluorescence sensor based on acrylated citric acid for detection of melamine adulteration: Application in milk powder
    (2022-06-18) KÖK YETİMOĞLU, ECE; KAHRAMAN, MEMET VEZİR; ÇUBUK, SONER; Taşci N., Çubuk S., Yetimoğlu E. K., Kahraman M. V.
    Melamine selective acrylate citric acid (ACA) based polymeric membrane sensor was prepared by radical polymerization method and the sensor was characterized. The sensor showed a selective fluorescent response to melamine (λex/λem=388/425 nm). The sensor response is linear in the concentration range of 3.96x10-9 to 7.93x10-8 mol L-1, the optimum pH value is 6.0 and response time is less than 1 minute. Limit of detection (LOD) and limit of quantification (LOQ) were calculated as 2.32 x 10-10 mol L-1 and as 7.74 x 10-10 mol L-1, respectively. The sensor showed great selectivity towards melamine in the presence of a large number of molecules and ions. The performance of sensor was also confirmed by determining of melamine in milk powder sample and the results were compared with HPLC results and acceptable results were obtained. As a conclusion, the results revealed that the proposed sensor is an interesting alternative for melamine determination. Keywords: Adulteration; Fluorimetric sensor; Melamine; Milk powder; Polymeric sensor.
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    Computational study on radical-mediated thiol-epoxy reactions
    (2023-09-01) KAHRAMAN, MEMET VEZİR; Nallbani B. G., Kahraman M. V., Degirmenci I.
    Radical-mediated thiol-epoxy reactions were elucidated for analyzing the overlap problem of the thiol–ene/thiol–epoxy systems using computational approaches. Nine epoxy model molecules were evaluated to mimic the chemical structures and reactivity of some industrial epoxy molecules. Modeling reaction mechanisms was conducted through density functional theory (DFT) calculations using the M06-2X/6-31+G(d,p) level at 1.0 atm and 298.15 K. An analog thiol–ene mechanism was proposed for radical-mediated thiol–epoxide reactions. Unlike the thiol–ene reactions, the addition reaction to epoxides is relatively slow (rate constants <10–4 M–1 s–1). However, the chain transfer, which paves the way for the overlapping of dual curing systems, is quite fast (rate constants >101 M–1 s–1). High stability of thiyl radicals, epoxy ring strain, and the instability of formed alkoxy radical from addition reaction were emphasized as the main driving forces for the reaction energetics and kinetics. Control of temperature and using certain thiols are strongly recommended to avoid curing step overlap based on the findings in this study.