A biochar-modified carbon paste electrode

The present work examıned the use of biochar derived from tea waste as a novel electrode material. For the fabrication of the biochar electrode, suitable amounts of biochar and graphite were mixed with mineral oil for the first time. The electrochemical performance of the biochar-modified carbon paste electrode (BCPE) was measured by various cyclic voltammetric reactions for several redox systems. The factors affecting the electrode kinetics of BCPE surfaces were examined and optimized. The BCPE was applied as transducer in a glucose biosensor. The results reflect the effective properties of composite electrodes and the electrochemical properties of biochar showing that the BCPE could be used for various electrochemical applications

Construction of gold porowplate electrode and its application for iodine determination

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.ABSTRACT CONSTRUCTION OF THE GOLD POROUS PLATE ELECTRODE AND ITS APPLICATION FOR IODINE DETERMINATION KIRGOZ ANIK, Ulku Master Thesis in Chemistry Supervisor: Prof. Dr. Hüseyin Tural January 1998, 45 pages. In this thesis, a home made porous Au plate electrode was planned to construct and used in the determination of I2. An alloy which consists of gold and silver metals were used as the electrode material. Ag elements in the alloy were eliminated by means of dissolution process and by this way, a porous electrode was aimed to construct. Dissolution process was made both chemically (with acid) and electrochemically (by anodic oxidation). With this Au porous plate electrode, the parameters for iodine determination was examined. Saturated I2 solution was prepared by dissolving solid I2 in pure water. From this stock solution, a series of dilute solutions were prepared and voltammograms were recorded where HCIO4 solution was used as a supporting electrolyte. By plotting current values against concentrations, a current-concentration curve was obtained. From this curve, it can be seen that the linear variation range of current values lasted up to 2,8. 10"4 M I2 concentration and the detection limit was equal to 2,18.10"5 M. The reproducibility of determination was tested by taking seven consecutive voltammograms of 2.1 0"4 M I2 solution. The result was calculated in relative standard deviation form and found as %2,39. The sensitivity of the electrode was compared with G.C.E, smooth Au and platinised Pt electrode by measuring the current density of each electrode. As a result the best result was obtained from the Au porous plate electrode. Keywords: Au porous plate electrode, determination of iodine.IV ÖZET POROZ ALTIN ELEKTROD YAPIMI VE İYOD TAYİN KOŞULLARININ ARAŞTIRILMASI KIRGÖZ ANIK, Ülkü Yüksek Lisans Tezi, Kimya Bölümü Tez Yöneticisi: Prof. Dr. Hüseyin Tural Ocak 1998, 45 sayfa Bu tezde, laboratuar koşullarında poroz altın elektrot yapımı planlanmış ve bununla I2 tayininin gerçekleştirilmesi amaçlanmıştır. Elektrot materyali olarak altın ve gümüş metallerinden oluşan bir alaşım kullanılmıştır. Oluşturulan alaşımdan gümüş elementi çözündürülerek poroz bir elektrot elde edilmeye çalışılmıştır. Çözündürme işlemi hem kimyasal (asitle), hem de anodik yükseltgemeyle sağlanmıştır. Oluşturulan poroz altın elektrotla iyodun saptanabilme koşulları araştırılmıştır. Bunun için katı iyottan yola çıkılarak iyodun sudaki doygun çözeltisi hazırlanmış ve bu doygun çözeltiden yola çıkarak hazırlanan seyreltik I2 çözeltilerinin HClO4'lü ortamda voltamogramları alınmıştır. Bu voltamogramlardan gidilerek derişim-akım eğrileri elde edilmiştir. Bu eğrilerden, oluşan akımın, 2,8.10^ M h derişimine kadar derişimle çizgisel değiştiği ve saptama alt sınırının 2, 18.1 0"5 M olduğu saptanmıştır. Aynı derişimle yinelenen ölçmelerle tayinin tekrarlanabilirliği bağıl standart sapma cinsinden hesaplanmış ve bu değer %2,39 olarak bulunmuştur. Elektrodun duyarlığı, akım yoğunluğu cinsinden camsı karbon, düzgün altın ve platinlenmiş platin elektrotla kıyaslanmış ve en iyi sonucu poroz altın levha elektrodun verdiği gözlenmiştir

Centri-voltammetric determination of Pb(II) by using Al(OH)3 and amberlite XAD-7 resin as carrier precipitate

Bu tezde Sentri-Voltammetri yöntemi geliştirilerek santrifüjle önderiştirme tekniği gerçekleştirilmiştir. Bu amaçla taşıyıcı çökelek olarak Al(OH)3 ve Amberlite XAD-7 Reçinesi kullanılmış ve bu sayede Pb(II) tayini gerçekleştirilmiştir. Bu amaçla, öncelikle taşıyıcı miktarı, adsorpsiyon zamanı, çökelek oluşum süresi, pH, santrifüj zamanı ve santrifüj süresi, tarama hızı, reçine büyüklüğü ve boyutu gibi parametreler optimize edilmiş daha sonra da Pb(II) ölçümüne ilişkin tekrarlanabilirlik ve belirtme alt sınırı hesaplanmıştır. Ayrıca bazı iyonların girişim etkisi de incelenmiştir. Belirtme alt sınırı ve RSD Al(OH)3 için sırasıyla 2.2 x 10-9 M ve % 5.40 olarak bulunurken Amberlit XAD-7 için bu değerler 5.20 x 10-9 M ve % 7.76 olarak hesaplanmıştır. Ayrıca yöntem uygulanmadan ve uygulandıktan sonra akımda yaklaşık olarak 100-170 katlık bir artış gözlenmiştir

Graphene-metallic nanocomposites as modifiers in electrochemical glucose biosensor transducers

anik, ulku/0000-0002-3607-7208; Tepeli Buyuksunetci, Yudum/0000-0002-4717-7933WOS: 000397826400001Graphene sheets and three different graphene-metallic nanocomposites including graphene-copper (graphene-Cu), graphene-nickel (graphene-Ni) and graphene-platinum (graphene-Pt) were prepared and characterized in the first place. Then the electrochemical performances of these nanocomposites were tested in glucose biosensor transducers, which were formed by combining these metallic nanocomposites with glucose oxidase enzyme and glassy carbon paste electrode (GCPE). This is the first work that includes the usage of these graphene-Me nanocomposites as a part of glucose biosensor transducer. Fabricated amperometric biosensors linear ranges were obtained as follow: For the plain graphene, the linear range was found in the concentration range between 50 mu Mand 800 mu Mwith the RSD (n= 3 for 50 mu M glucose) value of 12.86% and LOD value of 7.2 mu M. For graphene-Pt modified glucose biosensor, the linear range was between 10 mu M and 600 mu M with the RSD (n= 3 for 50 mu M glucose) value of 3.45% and LOD value of 3.06 mu M. in the case of graphene-Ni modified glucose biosensor, the values were 25 mu M to 600 mu M with the RSD (n= 3 for 50 mu M glucose) value of 8.76% and LOD value of 24.71 mu M and for graphene-Cu modified glucose biosensor linear range was 25 mu M to 400 mu M with the RSD (n= 3 for 50 mu M glucose) value of 3.93% and LOD value of 2.87 mu M

Oxidase mimicking Co/2Fe MOF included biosensor for sialic acid detection

A facile amperometric biosensor that included oxidase mimicking Co/2Fe metal-organic framework (MOF) for sialic acid (SA) detection was prepared. Amperometric SA biosensor was constructed on a gold screen-printed electrode via immobilization of Co/2Fe MOF and N-acetylneuraminic Acid Aldolase (NANA-Aldolase) enzyme, respectively. NANA-Aldolase enzyme converts free SA into pyruvate and N-acetyl-D-mannosamine. After this conversion, oxidase mimicking Co/2Fe bimetallic MOF converts pyruvate into acetylphosphate and O2 into H2O2. Investigation of analytical characteristics resulted with the linear range of 0.02 mM-1.00 mM of SA concentration with limit of detection value of 0.026 mM. Sample application studies with developed SA biosensor were carried out with GD3 ganglioside and HeLa cancer cell lines which have high SA concentrations while A549 cell lines were also used as control group. Before detecting free SA, the bound SA was freed from SA sources where every step was monitored via electron impedance spectroscopy. Then, free SA was successfully detected with the amperometric SA biosensor and as a result, more practical and accurate system was developed.The grant from The Scientific and Technological Research Council of Turkey (TUBITAK) with Project No: 119R064 in the frame of COST Action (CA18103) was greatefully acknowledged.Scientific and Technological Research Council of Turkey (TUBITAK) [119R064, CA18103