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Öğe Application of half-sandwich metal-phosphinite compounds to biological activities: Determine the energies of the HOMO and LUMO levels(Wiley-V C H Verlag Gmbh, 2023) Meriç, Nermin; Rafikova, Khadichakhan; Zazybin, Alexey; Güzel, Remziye; Kayan, Cezmi; Karakas, Duygu Elma; Dündar, Abdurrahman; Aydemir, MuratMononuclear transition metal complexes 1-(furan-2-yl)ethyldiphenyl[dichloro(eta(6)-p-cymene)ruthenium(II)]phosphinite, (2), 1-(furan-2-yl)ethyldiphenyl[dichloro(eta(6)-benzene) ruthenium(II)] phosphinite (3), 1-(furan-2-yl)ethyldipheny[chloro(eta(4)-1,5-cyclooctadiene)rhodium(I)]phosphinite (4), 1-(furan-2-yl)ethyldiphenyl[dichloro (eta(5)pentamethylcyclopentadienyl)iridium (III)] phosphinite (5) were synthesized and characterized by microanalysis, infrared, MS, and NMR spectroscopy. The biological activities of the complexes were also tested. Compounds 2 and 5 were the best complexes at DPPH radical scavenging and reducing power activity at 73.27 % and 0.41 at 200 mu g/mL, respectively. The highest antimicrobial activity exhibited by complex 3 as 14 mm inhibition zone against S. aureus. All of the complexes have cleaved the DNA from the double-strand and exhibited three bands on gel electrophoresis. Moreover, cyclic voltammetry studies of the phosphinite complexes were carried out to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical and some electronic properties.Öğe Bitki ve hayvanlarda üreme, büyüme ve gelişme ünitesinin değerlendirme sürecinde kullanılan oyunlaştırma etkinliğinin öğrencilerin fen bilimleri dersindeki başarılarına etkisi(Dicle Üniversitesi Ziya Gökalp Eğitim Fakültesi, 2018) Karayılan, Mehtap; Çakmak, Gonca; Güzel, RemziyeBu araştırmanın amacı “Bitki ve Hayvanlarda Üreme, Büyüme ve Gelişme” ünitesinin değerlendirme sürecinde kullanılan oyunlaştırma etkinliğinin öğrencilerin fen bilimleri dersindeki başarılarına etkisini incelemektir. Araştırmada eşitlenmemiş kontrol gruplu yarı deneysel desen kullanılmıştır. Bu araştırma 6.sınıfta öğrenim gören 63 öğrenci ile yürütülmüştür. Kontrol grubunda 33 öğrenci, deney grubunda ise 30 öğrenci bulunmaktadır. Araştırma 5 hafta sürmüştür. Kontrol grubuna çoktan seçmeli bir ön ve son başarı testi uygulanmıştır. Deney grubuna ise kontrol grubuna uygulanan ön ve son başarı testinin aynısı plickers uygulamasıyla yapılmıştır. Araştırmada elde edilen veriler SPSS paket programı kullanılarak analiz edilmiştir. Verilerin analizinde Bağımsız Örneklem T-Testi, Mann Whitney U testi, Wilcoxon İşaretli Sıralar Testi ve Bağımlı Örneklem T-Testi kullanılmıştır. Araştırmanın sonuçlarına göre deney ve kontrol grubundaki öğrencilerin uygulama sonrasında başarılarında deney grubu lehine anlamlı farkın olduğu görülmüştür.Öğe Çeşitli flotasyon atıklarının değerlendirilmesi ve cevherden çıkılarak Se, Te, Sb, As uzaklaştırılması ve selenyum ile Tellür'ün saflaştırılması(2017) Güzel, Remziye; Ziyadanoğulları, RecepBu çalışma; flotasyon atıklarının değerlendirilmesi ve bakır cevherinden Se, Te, Sb ve As uzaklaştırılması amacıyla yapılmıştır. Çalışmanın birinci aşamasında Elazığ Maden Bakır İşletmelerinin üç farklı noktasından temin edilen ve oksitli bakır cevherinin flotasyonunda atık olarak atılan pirit atıkları kullanılmıştır. Bu numuneler -100 mesh'in altına kadar öğütülüp 110 0C'de kurutulmuştur. Numunelerin analizi sonucunda; kollektif pirit atığının % 0,64 Cu, % 0,021 Co ve % 7,79 S içerdiği, selektif pirit atığının % 0,59 Cu, % 0,28 Co ve % 39,53 S içerdiği, kollektif ve selektif pirit atığının birleştiği noktadan alınan örneğin ise % 1,17 Cu, % 0,07 Co ve % 7,26 S içerdiği tespit edilmiştir. Kollektif ve selektif pirit atıklarından bakır ve kobalt kazanılması için örnekler kapalı sistemde kavurma işlemine tabi tutulmuştur. Kapalı sistemde kavurma işlemine tabi tutulan numunelerden alınan 10'ar gramlık örneklerin 600 0C'de hava atmosferinde kavrulmaları sonucu bakır ve kobalt çözeltiye alınmıştır. İkinci bir işlem olarak pirit atığı sülfürleme işlemine tabi tutulmuş, sülfürlenen numune flotasyonla zenginleştirilip elde edilen konsantre 600 0C'de kavrulup, kavurma sonucu elde edilen örneklerden bakır ve kobaltın çözeltiye alınması şeklinde bir yol izlenmiştir. Konsantrenin doğrudan kavrulması sonucu istenilen verim elde edilememiş, ancak özel koşullar altında yapı değişikliği sağlanarak yapılan kavurma sonucunda bakır ve kobaltın % 100'e yakın verimlerle çözeltiye alınması sağlanmıştır. Çalışmanın ikinci kısmında Hatay İline bağlı Kisecik Köyünden temin edilen bakır cevherinden Se, Te, Sb ve As'nin uzaklaştırılmasına çalışılmıştır. Temin edilen numune -150 mesh'in altına kadar öğütülüp 110 0C'de kurutulmuştur. Numunenin analizi neticesinde 14,1 ppm Se, 5,3 ppm Te, 19,4 ppm Sb, % 5,83 As ve % 10,72 S içerdiği tespit edilmiştir. Hatay yöresinden temin edilen cevherin uygun yüzey ve kristal yapısı elde edildikten sonra uygun flotasyon koşulları sağlanarak elde edilen konsantreden bakır ve kobalt kazanımından önce uygun görülen ön işlemle cevherden Se, Te, Sb ve As uzaklaştırılması ile ilgili çalışmalar yapılmıştır. Konsantreden Se, Te, Sb ve As uzaklaştırılırken, geriye kalan örneğin kavurma işlemine tabi tutulması sonucu bakır ve kobaltın istenilen düzeyde çözelti ortamına alınması amaçlandığından üç farklı işlem yapılmıştır. Birinci işlemde, flotasyonla zenginleştirilen konsantreye değişik miktarlarda ham pirit ilave edilerek homojen bir karışım oluşturulduktan sonra ön işleme tabi tutularak konsantreden uzaklaştırılan Se, Te, Sb ve As değerleri tespit edilmiştir. İkinci işlemde, flotasyonla zenginleştirilmiş konsantreden Se, Te, Sb ve As uzaklaşması için ortama değişik miktarlarda elementel kükürt konularak ön işleme tabi tutulmuştur. Üçüncü işlemde, konsantreye değişik miktarlarda elementel demir tozu ilave edilerek homojen bir karışım oluşturulmuş ve karışım ön işleme tabi tutulmuştur. Son aşamada konsantreden uzaklaştırılan Se, Te, Sb ve As içerikli numuneden bu elementlerin birbirinden ayrılmasına çalışılmıştır. Elde edilen numunenin analizi sonucu 690 ppm Se, 220 ppm Te, 390 ppm Sb, % 30,5 As ve % 65,4 S içerdiği saptanmıştır.Öğe The comparative reactions of 2-cis-4-ansa and spiro cyclotetraphosphazenes with difunctional ligands: Structural and stereogenic properties, electrochemical, antimicrobial and cytotoxic activity studies(Wiley, 2021) Okumuş, Aytuğ; Elmas, Gamze; Kılıç, Zeynel; Binici, Arzu; Ramazanoğlu, Nagehan; Açık, Leyla; Çoşut, Bünyemin; Güzel, Remziye; 0000-0002-2169-5695; 0000-0003-4877-3697; 0000-0003-1061-8122; 0000-0001-7470-4156; 0000-0003-0541-9129; 0000-0002-3672-8429; 0000-0001-6530-0205; 0000-0002-5781-6049In this study, two kinds of compounds, namely, mono-ferrocenyl-2-cis-4-dichloro-ansa- (2,4-ansa; 3) and mono-ferrocenyl-spiro- (spiro; 4) hexachlorocyclotetraphosphazenes, were obtained by the Cl replacement reaction of N4P4Cl8 (1) with an equimolar amount of sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (2). The reactions of 2,4-ansa (3) with excess diamines and dialkoxides resulted in the formation of ansa-cyclotetraphosphazenes (3a-3e). Spiro (4) was reacted with excess diamines and dialkoxides to give the mono-ferrocenyl-spiro-cyclotetraphosphazenes (4a-4d). Although 2,4-ansa (3) produced the dispiro (3a) with N-(4-fluorobenzyl)-N '-methylethane-1,2-diamine, it afforded both monospiro (3b) and dispiro (3c) with N-(4-fluorobenzyl)-N '-methylpropane-1,3-diamine. However, spiro (4) yielded a trispiro (4a) with N-(4-fluorobenzyl)-N '-methylethane-1,2-diamine and 2,6-dispiro (4b) with N-(4-fluorobenzyl)-N '-methylpropane-1,3-diamine. The structures of the phosphazenes were elucidated by FTIR, ESI-MS and/or HRMS, spectroscopic and crystallographic (for 3f and 4b) data. Furthermore, the electrochemical findings of cyclotetraphosphazenes exhibited electrochemically reversible one-electron oxidation of Fe-redox centre. As an example, the chirality of 3c was investigated by P-31 NMR spectroscopy on the addition of (R)-(+)-2,2,2-trifluoro-1-(9 '-anthryl)-ethanol, chiral solvating agent (CSA). The circular dichroism (CD) (for 3d and 3e), HPLC (for 3d, 3e and 3f) and X-ray (for 3f) display that these compounds have chirality (RS ' or SR ') in the solution and solid state. This paper also focuses on the antimicrobial activities, the interactions with pBR322 DNA, in vitro anticancer activity against L929 fibroblast and MCF7 breast cells, and antituberculosis activity against Mycobacterium tuberculosis H37Rv of the cyclotetraphosphazenes.Öğe Comparative study of the quantitative resolution of paracetamol and methocarbamol mixture by spectrophotometry with wavelet transform and UPLC techniques(Springer, 2022) Güzel, Remziye; Ertekin, Zehra Ceren; Ziyadanoğulları, Berrin; Dinç, Erdal; Ziyadanoğulları, RecepThe aim of this study was to develop a new simple and cost-effective spectrophotometric method to be used as an alternative to chromatography for the analysis of paracetamol and methocarbamol (PAR-MET) combination. In this regard, a comparative study on the quantitative resolution of PAR and MET mixture using continuous wavelet transform (CWT) and ultra-performance liquid chromatography (UPLC) techniques was performed. In interpretation of the spectrophotometric data, three different wavelet families Biorthogonal3.5 (Bior3.5), Mexican Hat Function (Mexh), and Symlets5 (Sym5) were found suitable to get better transform of zero-order spectra of the samples containing PAR and MET. The concentrations of PAR and MET in the working range of 4.0 - 20.0 mu g/mL and 5.0 - 45.0 mu g/mL, respectively, were proportional to the wavelet amplitudes. This mathematical relationship was used to construct calibration curves for each compound. After validation of the CWT method, analyses of commercial tablets were successfully performed. A new UPLC method was developed and validated in order to compare the results with those obtained by the CWT method and the data were found comparable. The analysis of results obtained from experimental trials showed that the proposed CWTmethod is suitable for the quality control and quantitative assessment of both active substances in tablet formulations.Öğe Çözeltiden kurşun ve kadmiyumun uzaklaştırılması(2016) Güzel, Remziye; Ziyadanoğulları, RecepÇevre sorunlarının oldukça büyük boyutlara ulaştığı günümüzde, bu konu ile ilgili çalışmaların da önemi bir hayli artmıştır. Bu alanda yapılan çalışmaların önemli bir kısmım gerek içme sularında ve gerekse bir çok atık sularda ağır elementlerin giderilmesi oluşturmaktadır. Gelişen endüstrileşme ile birlikte özellikle suların ağır elementler bakımından kirlenmesi, zamanla artan bir problem olarak ortaya çıkmaktadır. Bu elementlerden kurşun ve kadmiyum önemli bir yer tutmaktadır. Bu çalışmada, çeşitli konsantrasyonlarda hazırlanmış olan kurşun ve kadmiyumun ayrı ayrı ve birlikte bulundukları çözeltilerinin kalker, kalsit, dolomit, magnezit (kalsit ve kuvars içeren) ile dolomit ve magnezitin bitümlü şist külleriyle çeşitli şekillerde elde edilen karışımlarının işleme sokulmalarıyla çözeltiden uzaklaştırılan bu elementlerin değerleri saptanmıştır. Çalışmalar sonucunda oldukça etkili ayırma işlemlerinin yapıldığı da ortaya çıkmıştır.Öğe Fabrication of an electrochemical E. coli biosensor in biowells using bimetallic nanoparticle-labelled antibodies(Wiley-V C H Verlag Gmbh, 2015) Ekşi, Haslet; Güzel, Remziye; Güven, Burcu; Boyacı, İsmail Hakkı; Solak, Ali Osman; 0000-0003-1333-060XAn electrochemical biosensor was developed for the determination of Escherichia coli (E. coli) in water. For this purpose, silver-gold core-shell (Ag@Au) bioconjugates and anti-E. coli modified PS-microwells were designed in a sandwich-type format in order to obtain higher sensitivity and selectivity. Ag@Au bimetallic nanoparticles were synthesized by co-reduction method. The core-shell formation was analyzed by using UV-Vis spectroscopy and transmission electron microscopy. Biotin labeled anti-E. coli antibodies were coupled with Ag@Au nanoparticles to form bioconjugates. The electrochemical immunosensor was prepared by immobilizing anti-E. coli on polystyrene (PS)-microwells via chemical bonding. These modified microwells were identified with X-ray photoelectron spectroscopy and surface enhanced Raman spectroscopy. E. coli was sandwiched between Ag@Au bioconjugates and anti-E. coli on PS-microwells at different concentrations. The relationship between the E. coli concentration and stripping current of gold ions (Au3+) were investigated by square wave anodic stripping voltammetry at pencil graphite electrode. The proposed method can provide some advantages such as lower detection limit and shorter detection time. The electrochemical response for the immunosensor was linear with the concentration of the E. coli in the range of 10(1) and 10(5) cfu/mL with a limit of detection 3 cfu/mL. The procedure maintains good sensitivity and repeatability and also offers utility in the fields of environmental monitoring and clinical diagnosis.Öğe Half-sandwich ruthenium(II) and iridium(III) complexes of imidazole based phosphinite ligands: antioxidant and antibacterial activities as well as electrochemical properties(John Wiley and Sons Inc, 2024) Işık, Uğur; Rafikova, Khadichakhan; Meriç, Nermin; Güzel, Remziye; Kerimkulova, Aygül; Akimbek, Arailym; Okumuş, Veysi; Durap, Feyyaz; Kayan, Cezmi; Aydemir, MuratRuthenium(II) and iridium(III) complexes of phosphinites including imidazole moiety were synthesized and characterized by microanalysis, IR, MS, and NMR spectroscopies. Antibacterial activity against Gram-positive and Gram-negative bacterial strains was assessed in all complexes. The highest radical scavenging (72.2 %) was obtained for [3-(3-chloro-2-({[dichloro(η6-benzene)ruthenium]diphenylphosphanyl}oxy)propyl)-1-butyl-1H-imidazol-3-ium chloride], 4 at 200 μg/mL concentration, while [3-(3-chloro-2-({[dichloro(η5-pentamethylcyclopentadienyl)-iridium]diphenylphosphanyl}oxy)pro-pyl)-1-butyl-1H-imidazol-3-ium chloride], 6 demonstrated the highest antibacterial activity as 13 mm inhibition zone against E. hirea. Furthermore, optical and electrochemical featured of metal complexes containing imidazole phosphinite were investigated utilizing UV–vis absorption and cyclic voltammetry techniques. Consequently, all complexes can be proposed as metal-based charge convertible phosphinite complexes which may be employed as new generation and synergistic Dye-Sensitized Solar Cell (DSSC) materials.Öğe A New application of PARAFAC model to UPLC dataset for the quantitative resolution of a tri-component drug mixture(Oxford University Press, 2021) Güzel, Remziye; Ertekin, Zehra Ceren; Dinç, ErdalIn the presented work, a three-way analysis of ultra-performance liquid chromatography-photodiode array (UPLC-PDA) dataset was performed by parallel factor analysis (PARAFAC) for quantitatively resolving a ternary mixture containing paracetamol and methocarbamol with indapamide selected as an internal standard in their co-eluted chromatographic conditions. Paracetamol and methocarbamol were quantified in the working range between 3-24 and 5-50 mu g/mL by applying PARAFAC decomposition to UPLC-PDA data array obtained under unresolved chromatographic peak conditions. To compare the experimental results provided by co-eluted UPLC-PARAFAC method, an ordinary UPLC method was developed ensuring proper separation of the peaks. The performance of both PARAFAC and ordinary UPLC methods were assessed by quantifying independent test samples, intra- and inter-day samples and spiked samples of pharmaceutical preparations. Then, both methods were applied for quantitative estimation of the related drugs in a commercial pharmaceutical preparation. In this study, PARAFAC method was proved to be a very powerful alternative for the quality control of pharmaceutical preparations containing paracetamol and methocarbamol even in their co-eluted chromatograms with high precision and accuracy in a short chromatographic runtime of 1.2 min.Öğe New voltammetric approach to the quantitative estimation of sildenafil citrate in tablets using disposable pencil graphite electrode(American Scientific Publishers, 2014) Güzel, Remziye; Ekşi, Haslet; Dinç, Erdal; Solak, Ali OsmanThe voltammetric behavior of sildenafil citrate (SC) was studied through differential pulse stripping voltammetry. The best sensitivity, optimal experimental conditions and settings for the voltammetric method development were obtained by applying experimental design and optimization methodology to the designed sample runs at different accumulation times, accumulation potentials and pHs. The linearity over the concentration range 1 × 10-7 M-8 × 10-6 M for SC was determined and the limit of detection (LOD) was 3.1 × 10-8 M. For the method ability and validity, mean recovery result and relative standard deviation were found to be 99.3% and 2.19%, respectively. The method was applied to the determination of SC in pharmaceutical and plasma samples.Öğe Phosphorus-nitrogen compounds. Part 72. Bisspiro(N/N)cyclotri-phosphazenes with 4-chlorobenzyl and ferrocenyl pendant arms: Synthesis, structural characterization, dye-sensitized solar cell fabrication and antituberculosis activity studies(Elsevier B.V., 2024) Berberoğlu, İpek; Cemaloğlu, Reşit; Binici, Arzu; Yakut, Mehtap; Asmafiliz, Nuran; Kılıç, Zeynel; Güzel, Remziye; 0000-0002-2802-0754; 0000-0001-7470-4156; 0000-0002-9335-4101In this study, dichlorobisspiro(N/N)cyclotriphosphazenes with 4-chlorobenzyl and ferrocenyl-pendant arms were prepared to investigate their spectroscopic and crystallographic characterizations, and antituberculosis activities. The chlorine replacement reactions of tetrachloro(4-chlorobenzyl)spiro(N/N)cyclotri-phosphazenes with ferrocenyldiamines (4 and 5) lead to dichlorobispiro(N/N)cyclotriphosphazenes, containing unsymmetrical diaminospirorings. All cyclotriphosphazenes were characterized by mass spectrometry, FTIR and 31P NMR spectroscopies. Two different stereogenic P-centers are present in the unsymmetrically substituted inorganic-organic fused hybrid rings. These compounds may be in the form of racemic mixtures (RR'/SS' and RS'/SR'). The molecular and crystal structures of trans (6a and 7a) and cis (6b and 7b) isomers were elucidated by single-crystal X-ray structural crystallography. The space groups of trans-6a, cis-6b, trans-7a and cis-7b are centrosymmetric P -1, P bca, P 21/n and P bca, respectively. Therefore, the crystal lattices contain both enantiomers. The absolute configurations of P2 atoms of 6a, 6b, 7a and 7b are R, R, S and S, respectively. It was determined that the most effective compound was 6b against Mycobacterium tuberculosis H37Rv (ATCC 27,294) strain among the phosphazenes 6a, 6b and 10b. Among the compounds, In the reversible cyclic voltammograms of ferrocenyl-dispirophosphazenes, only one oxidation–reduction wave was observed. The HOMO energy values of the compounds were figured out using the oxidation potential (Eox). Whereas, the LUMO energy values were figured out from the optical band gap values using Tauc plots. In addition, it was determined that the most effective compound that can be used in dye-sensitized solar cells (DSSCs) is cis-11b.Öğe Phosphorus-nitrogen compounds: Part 76. design and syntheses of dispiro- and trispiro(N/N)cyclotriphosphazenes: Conformational and structural analyses, chirality, electrochemical, dye-sensitized solar cells, and bioactivity studies(American Chemical Society, 2024) Cemaloğlu, Reşit; Asmafiliz, Nuran; Tümer, Yasemin; Hökelek, Tuncer; Kılıç, Zeynel; Çelik, Nejla Nur; Açık, Leyla; Güzel, Remziye; Erdal, Gülbahar GüzelThe reactions of monospirocyclotriphosphazenes (1 and 2) with N-methyl-1,3-diaminopropane gave unsymmetrical cis-(3 and 5) and trans-(4 and 6) dispirocyclotriphosphazenes. Trans-cis-trans (tct) (7 and 11), cis-cis-cis (ccc) (8 and 12), trans-trans-cis (ttc) (9 and 13), and cis-trans-trans (ctt) (14) trispirocyclotriphosphazenes were obtained from the reactions of 3 and 5 and 4 and 6 with N-methyl-1,3-diaminopropane. cis-Dispirocyclotriphosphazenes (3 and 5) exist as “pseudomesoracemates”, while trans-dispirocyclotriphosphazenes (4 and 6) are in “racemates”. The existences of cis-3 and trans-4 as “pseudomesoracemate” and “racemate” were confirmed by 31P NMR spectra recorded by the addition of “chiral solvating agent (CSA)”. X-ray crystallography proved that the absolute configurations of each enantiomer of cis-5 and trans-6 are SS′ and RS′. Trispirocyclotriphosphazenes tct, ttc, ccc, and ctt exist as racemates, pseudomesoracemate, and meso forms. Furthermore, Hirshfeld surface analysis of the crystal structures of cis-5 and trans-6 revealed that the most significant contribution to crystal packing comes from H···H (58.2 and 57.6%, respectively). An oxidation-reduction wave was detected in the reversible cyclic voltammograms of the phosphazenes. The highest power conversion efficiency in dye-sensitized solar cell studies was obtained with cis-5. Additionally, trans-6 exhibited the lowest minimal inhibitory concentration value (78.1 μM) against Candida tropicalis, and it was observed to cleave pBR322 plasmid DNA.Öğe Synthesis, characterization and structure effects on extractability and selectivity of N,N′-bis(salicylaldehydene) - 1,4-bIS-(m-ami̇nophenoxy) butane towards some divalent cations(Wiley-V C H Verlag Gmbh, 2007) Ziyadanoğulları, Berrin; Ceviziçi, Deniz; Temel, Hamdi; Güzel, Remziye; 0000-0002-9004-8993The extraction of copper(II), nickel(II) and cobalt(II) from the aqueous phase with N,N'-bis(saticylaldehydene)-1,4-bis-(in-aminophenoxy)butane (NIAS), which was synthesized from 1,4-bis(m-aminophenoxy)butane and salicylaldehyde, was studied. Microanalytical data, elemental analysis, UV-visible H-1 and C-13 n.m.r. spectra and IR-spectra were used to confirm the structures. The extractability and selectivity of divalent cations were evaluated as a function of relationship between distribution ratio of the metal and pH or ligand concentration. Cu+2 showed the highest extractability and selectivity at pH 6.0, whereas Ni+2 and Co+2 showed at pH 9.2. The stoichiometries of the compounds formed were estimated to be CuL, CoL, NiL, where L is N,N'-bis(salicylaldehydene)-1,4-bis-(m-aminophenoxy)butane. It was concluded that MAS can effectively be used in solvent extraction of copper(II), nickel(II) and cobalt(II) from the aqeous phase to the organic phase.Öğe Synthesis, characterization, and application of silver nanoparticle-thiophenol nanocomposite film on the glassy carbon surface(Wiley, 2013) Güzel, Remziye; Ekşi, Haslet; Üstündağ, Zafer; Solak, Ali OsmanIn this study, 4-thiophenol modified glassy carbon electrode was prepared by the reduction of 4-diazothiophenol tetrafluoroborate salt. Silver nanoparticles were attached to the thiophenol modified surface to prepare a thiophenol-silver nanoparticle composite film. 4-Aminothiopenol molecules were deposited by self-assembling technique to form multi-layered nanofilms of TP/SNP/PhNH2 on glassy carbon substrate. These surfaces were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, reflectance-absorption infrared spectroscopy, and ellipsometry at each multilayer film growth process. Atomic force microscopic images of GC/TP/SNP/PhNH2 surfaces were also acquired. The characterization methods show that the amine group containing surface permits the subsequent modification by a variety of coupling reactions for the immobilization of more complex systems. An application of the electrode modification for the determination of uric acid with a significantly lower detection limit is described. Copyright (c) 2013 John Wiley & Sons, Ltd.Öğe Well designed iridium-phosphinite complexes: Biological assays, electrochemical behavior and density functional theory calculations(Elsevier B.V., 2024) Khadichakhan Rafikova; Meriç, Nermin; Binbay, Nil Ertekin; Okumuş, Veysi; Erdem, Kemal; Belyankova, Yelizaveta; Güzel, RemziyeMononuclear phosphinite Iridium complexes based on ferrocene group have been prepared and characterized by various spectroscopic techniques. The complexes were subjected to cyclic voltammetry studies in order to determine the energies of HOMO and LUMO levels and to estimate their electrochemical and some electronic properties. Organic complex-based memory substrates were immobilized using TiO2-modified ITO electrodes, and the memory functions of phosphinite-based organic complexes were verified by chronoamperometry (CA) and open-circuit potential amperometry (OCPA). Extensive theoretical and experimental investigations were directed to gain a more profound understanding of the chemical descriptors and the diverse electronic transitions taking place within the iridium complexes, as well as their electrochemical characteristics. The quantum chemical calculations were carried out for the iridium complexes at the DFT/CAM-B3LYP level of theory in the gas phase. Furthermore, the antioxidant, antimicrobial, DNA binding, and DNA cleavage activities of the complexes were tested. Complex 2 exhibited the highest radical scavenging activity (67.5 ± 2.24 %) at 200.0 mg/L concentration. It was observed that the complexes formed an inhibition zone in the range of 8–15 mm against Gram + bacteria and in the range of 0–13 mm against Gram – bacteria. The agarose gel electrophoresis method was used to determine the DNA binding and DNA cleavage activities of the complexes. All of the tested complexes had DNA binding activity; however, complexes 1, 2, and 8 showed better binding activity than the others.
