Browsing by Author "Karakoyun, Necdet"

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Biochar-Embedded Soft Hydrogel and Their Use in Ag Nanoparticle Preparation and Reduction of 4-Nitro Phenol
(Taylor & Francis As, 2013) Sahiner, Nurettin; Karakoyun, Necdet; Alpaslan, Duygu; Aktas, Nahit
The authors report the synthesis of a composite hydrogel based on acrylamide-chicken biochar(AAm)-CBand its use as a template in the preparation of silver metal nanoparticles. Moreover, we demonstrate the efficient utilization of p(AAm)-CB composite hydrogel as a reactor vessel in the reduction of an organic contaminant 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Experimental parameters affecting 4-NP reduction rate were investigated. The kinetics of the reduction reaction under different reaction conditions were also evaluated to determine the activation parameters. Activation energy for the reduction of 4-NP was 15.25kJmol1 and p(AAm)-CB-Ag composites possessed 99.45% activity after five repetitive uses.
Hydrogel-Biochar Composites for Effective Organic Contaminant Removal From Aqueous Media
(Elsevier, 2011) Karakoyun, Necdet; Kubilay, Senol; Aktas, Nahit; Turhan, Omer; Kasimoglu, Murat; Yilmaz, Selahattin; Sahiner, Nurettin
In this study, p(acrylamide)-chicken biochar (p(AAm)-CB), p(acrylamide)-wood biochar (p(AAm)-WB), and p(acrylamide)-tire biochar (p(AAm)-TB) hydrogel composites were prepared using acrylamide (AAm) as monomer with the corresponding biochars, with N,N'-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. P(AAm)-CB, p(AAm)-WB, and p(AAm)-TB were used as adsorbents to remove phenol from aqueous environments. The synthesized p(AAm)-CB, p(AAm)-WB, p(AAm)-TB and p(AAm) hydrogel composites had swelling values of 1112, 1045, 847, and 623%, respectively in distilled water. The prepared hydrogel biochar material compositions were examined using an elemental analyzer. Absorption of phenol into p(AAm)-WB was studied at different pHs to determine the optimum pH for maximum removal of phenol. The ionic strength of the medium was varied between 0.01 and 1 mol L-1 to determine the effect of salt (NaCl) on the absorption characteristics and it was found that the absorption of phenol increased with a decrease in the amount of salt. Langmuir and Freundlich isotherms were applied to describe the absorption characteristics and the Langmuir isotherm describes the absorption phenomena in this study much better than the Freundlich isotherm. Pseudo-first-order and pseudo-second-order kinetic studies were also applied to determine absorption characteristic. (C) 2011 Elsevier B.V. All rights reserved.
Investigation of the Aromaticity of Mono, Di, Tri and Tetraazaphenanthrene Derivatives
(Walter de Gruyter Gmbh, 2020) Ozturk, Erhan; Irak, Zeynep Turhan; Karakoyun, Necdet; Gumus, Aysegul; Gumus, Selcuk
In this chapter mono, di, tri and tetraaza substituted phenanthrene derivatives have been investigated computationally with B3LYP/6-31 + G(d,p) level of theory. Substitution of carbon atom of the main structure with nitrogen obviously disturbs the aromaticity, indeed it decreases it. Thus, the idea of regaining of the aromaticity back by using electron withdrawing groups came across. As a result of the computational calculations, energetically most unfavored structures have been found to be those where aza substitutiona are vicinal. Secondly, the aromaticities of the present species depend on the position of the centric substituent. In addition, the effect position of the side substituent has been considered. The system becomes more aromatic (possess greater negative NICS values or smaller HOMA value) when the electron withdrawing atoms or groups are adjacent to the centrically substituted heteroatoms.
Magnetically Separable Pd(0)-Polymer Brush on Rgo for Efficient Nitrophenols Reduction
(Wiley-v C H Verlag Gmbh, 2025) Karakoyun, Necdet; Zengin, Adem; Karagoz, Mustafa Hamdi
In this study, a facile and effective method is reported for the fabrication of a polydopamine/polyacrylamide co-deposited on magnetic reduced graphene oxide (PDOPA/PAAm@mag-rGO) composite, which offers a new host material for dispersing palladium nanoparticles (Pd NPs) for catalytic reduction of nitrophenols. PDOPA/PAAm was grafted onto mag-rGO through one-step dopamine-triggered polymerization in a short time (45 min) at room temperature. PDOPA/PAAm@mag-rGO not only was used as support but also supplied compatibility and stabilizing Pd N Ps deposition, which enhanced the catalytic properties. The catalytic efficiency of the Pd-PDOPA/PAAm@mag-rGO was carried out with the reduction of 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol by using NaBH4 as a reducing agent at room temperature. The reduction rate of the aforementioned nitrophenols was as follows: 4-nitrophenol>2-nitrophenol>2,4-dinitrophenol. Moreover, the catalyst showed high stability and catalytic efficiency over five sequential uses in the reduction reaction. Magnetic analysis reveals that the as-prepared catalyst had superparamagnetic properties, which allow the easy recovery of the catalyst from the reaction medium via an external magnet. This study also indicates that polymer brushes and noble metal nanoparticles combined with magnetic reduced graphene oxide can play an efficient composite material for the fabrication of multifunctional and multi-component graphene-based materials for diverse catalytic applications.
Molecularly-Imprinted Pumice as a Selective Solid-Phase Extraction Adsorbent for Kojic Acid Determination in Cosmetic Samples
(Pergamon-elsevier Science Ltd, 2025) Zengin, Adem; Karakoyun, Necdet; Demir, Derya Cay; Bilici, Mustafa
Herein, a highly sensitive molecularly-imprinted pumice (MIP-PMC) was tailored by employed the surface imprinting method and utilized as a solid-phase extraction (SPE) adsorbent for the fast and selective separation of kojic acid (KA) from cosmetic samples. The MIP-PMC was characterized in a systematic manner and found it to be a well-grown polymer layer on the PMC. The adsorption capacity of MIP-PMC was 89.9 mg/g, with an equilibrium adsorption time of 30 min. Moreover, the imprinting factor of MIP-PMC towards KA was found to be 3.28, which further demonstrated its evident selectivity for KA. Under optimized conditions, KA was successfully isolated from cosmetic products using MIP-PMC and quantified via ultraviolet-visible (UV-vis) spectrophotometry. Method validation demonstrated excellent linearity within the range of 0.04-400 mg/L, satisfactory precision (less than 5 %), and high recoveries (98.0-100.4 %). Furthermore, the method exhibited a low limit of detection (LOD) of 12.8 mu g/L with a preconcentration factor of 4. Moreover, the sensitivity of the developed method was also checked by using HPLC and the method has comparable analytical performance. The findings indicate that the integration of MIP-PMC based SPE with UV-vis spectrophotometry offers a highly efficient approach for sample pretreatment and the accurate determination of KA in real samples.
Pirimidin-5-karbonitril Türevlerinin ve Farklı Şekilde İkame Edilmiş Karbazollerin Işık Yayan Özellikleri: Teorik Bir Hesaplama
(2022) Karakoyun, Necdet; Erkan, Sultan
Bu çalışmada 4,6-Di (9H-karbazol-9-il) pirimidin-5-karbonitril (C1), 4,6-bis (3,6-di-tert-butil-9H-karbazol-9-il ) pirimidin-5-karbonitril (C2), 4,6-bis (3,6-dimetoksi-9H-karbazol-9-il) pirimidin-5-karbonitril (C3) bileşikleri B3LYP / 6-31G (d ) seviyesi. Sınır moleküler orbitallerin enerji yoğunlukları moleküler özellikleri incelenmiştir. Dikey iyonlaşma potansiyelleri (IPv), adyabatik iyonizasyon potansiyeli (IPa) (eV cinsinden), dikey elektron afinitesi (EAv), adyabatik elektron afinitesi (EAa), delik yeniden organizasyon enerjisi (h) ve elektron yeniden organizasyon enerjisi (e) hesaplandı (eV cinsinden) C1, C2 ve C3 bileşikleri için. C1 ve C3 bileşiklerinin e değerleri 0.29 ve 0.30 eV ve h değeri sırasıyla 0.18 ve 0.20 eV'dir. C1 ve C3 bileşiklerinin e değerleri 0,276 eV'den büyük ve h değeri 0,290 eV'den küçük olduğu için elektron taşıyan tabakalar (ETL) malzemesi olarak uygun olmadığı söylenebilir, bu nedenle delik yatak katmanları (HTL) için uygun bir malzemedir. C2 bileşiği hem ETL hem de HTL malzemeleri için uygundur.
Preparation of Carbon-Supported Nico Alloy Nanoparticles and Evaluation of Their Catalytic Activity in the Methanolysis of Ammonia Borane
(Elsevier Sci Ltd, 2023) Top, Tuba; Yurderi, Mehmet; Bulut, Ahmet; Karakoyun, Necdet; Ceylan, Esra; Zahmakiran, Mehmet
The present work reported the development of carbon-supported bimetallic NiCo nanoparticles for H2 production in the methanolysis of AB for electricity generation from fuel cells. It was investigated by powder X-ray diffraction (P-XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic properties of the Ni0.19Co0.81/C catalyst were carefully evaluated in terms of catalytic performance, such as different temperatures, metal [NiCo] loadings, substrate [AB] concentrations, and recyclability in 10 runs. The resulting N0.19Co0.81/C catalyst exhibits good catalytic activity with a high initial TOF of 136.65 min-1 and activation energy of 33.38 kJ mol- 1 for AB methanolysis. Moreover, in the recyclability test, the Ni0.19Co0.81/C catalyst maintained 95 % of its initial activity with 100 % conversion after ten runs.
Preparation of Magnetic Gel-Polymer Brush Metal Nanoparticle Hybrid Materials for Catalytic Degradation of Some Organic Dyes
(2023) Shallal, Mohammed Abdulkareem Shallal; Zengın, Adam; Karakoyun, Necdet
ÖZET BAZI ORGANİK BOYALARIN KATALİTİK BOZUNMASINA YÖNELİK MANYETİK JEL-POLİMER FIRÇA/METAL NANOPARÇACIK HİBRİT MALZEMELERİN HAZIRLANMASI sayfa Bu çalışmada, tekrar tekrar kullanılabilecek bir Pd@Polymer@CoFe₂O₄ katalizörü yapmak için birlikte çöktürme yöntemi kullanıldı. XRD analizi, Pd@Polymer@CoFe₂O₄ katalizörünün kristal yapısını ortaya çıkardı ve bileşimini ve saflığını doğruladı. SEM ve EDX analizleri sırasıyla numunenin morfolojisi ve element bileşimi hakkında ayrıntılı bilgi sağladı. Faz Co, Fe ve Pd elementlerini içerir. XRD analizi, kristal boyutu 3,2 nm olan tek fazlı bir nanoürün sentezini doğruladı. VSM ölçümleri ürünün üstün manyetik özelliklerini gösterdi; bu, ürünün manyetik ayırma proseslerinde veya manyetik olarak tahrik edilen reaksiyonlarda katalizör olarak potansiyel uygulamalara sahip olduğunu göstermektedir. Katalitik çalışmalar Pd@Polymer@CoFe₂O₄'nın metil turuncu (MO), metilen mavisi (MB) ve 4-nitrofenol (4-NP) gibi organik boyaların indirgenmesini katalize edebildiğini gösterdi. Üstelik manyetik katalizör birkaç döngüden sonra yeniden kullanım özellikleri gösterdi. Bu nedenle Pd@Polymer@CoFe₂O₄, organik kirleticilerin atık su arıtımına uygulanması için potansiyel bir adaydır. Anahtar k SHALLAL, Mohammed Yüksek Lisans , Kimya Mühendisliği Anabilim Dalı Danışman: Doç. Dr. Adam ZENGIN İkinci Danışman: Dr. Öğr. Üyesi Necdet KARAKOYUN 2023, 92elimeler: manyetik partikül, metal nanopartikül, jel-polimer fırça, boya bozunumu, heterojen kataliz.
Reusable Soft Hydrogels for Gold Recovery From Acidic Environments
(Taylor & Francis inc, 2013) Sahiner, Nurettin; Karakoyun, Necdet; Sahan, Tekin; Butun, Sultan; Aktas, Nahit
In this study, poly((N-(hydroxymethyl) acrylamide) co-1-allyl-2-thiourea) hydrogels were synthesized by free radical crosslinking copolymerization of N-(hydroxymethyl) acrylamide monomer with the addition of a co-monomer 1-allyl-2-thiourea, and N, N'-methylenebisacrylamide as the crosslinker. The copolymer, poly((N-(hydroxymethyl) acrylamide) co-1-allyl-2-thiourea), was used as a specific sorbent for the recovery of gold. The characteristics of the hydrogels were examined by elemental analyzer and swelling experiments. The effect of pH on the absorption of gold, and the separation and recovery of gold ions from ore samples were investigated. Measurement of absorbed gold was determined by using F-AAS and GF-AAS.
Selective and Sensitive Determination of Neopterin in Biological Fluids Using Magnetic Silica-Supported Molecularly-Imprinted Polymers
(Elsevier, 2025) Zengin, Adem; Karakoyun, Necdet; Bilici, Mustafa
Neopterin (NPT) is a key biomarker of immune system activation and holds significant importance in the diagnosis and monitoring of various clinical conditions. In this study, a novel magnetic silica-supported molecularly imprinted polymer (MIP-MS) was synthesized via surface imprinting and integrated with UV-vis spectrophotometry for the selective extraction and quantification of NPT in human serum and artificial cerebrospinal fluid. Comprehensive characterization was carried out and the results confirmed the successful fabrication of the MIP layer with well-defined structural and surface properties. Adsorption kinetics and isotherm studies were best fitted by the pseudo second-order (R2 = 0.9997) and Langmuir model (R2 = 0.9987), respectively and the results revealed the presence of specific recognition sites on the MIP-MS for NPT, resulting in adsorption capacity of 98.3 mg/g and imprinting factor of 4.77. Additionally, the MIP-MS exhibited outstanding reusability, retaining its performance over 10 adsorption-desorption cycles. The developed method demonstrated excellent sensitivity, with a wide linear range (3-300 nM), a detection limit of 1.18 nM and a recovery range of 97.6 %-100.4 %, accompanied by a relative standard deviation below 5.0 %. The findings suggest that the proposed MIP-MS coupled with UV-vis spectrophotometry provides a cost-effective, rapid, and highly selective alternative for NPT detection in biological samples.
Synthesis of New Mono and Bis-Triazol Derivativescomputational Chemistry Applications
(2019) Karakoyun, Necdet; Gümüş, Selçuk; Gümüş, Ayşegül
1,2,3-triazol bileşikleri biyolojik sistemlerde önemli bir yer oynar. İlaç kimyasında anti-HIV, antialerjik, antifungal ve antimikrobiyal olarak, koordinasyon kimyasında, kemosensörlerde, materyal ve polimer kimyasında ve daha pek çok alanda uygulanabilirliğe sahip çok önemli bileşiklerdir. Organik kimyada tek-kap çoklu adım (birden fazla tepkimenin tek bir reaktörde art arda gerçekleştiği) içeren sentetik yöntemler kompleks molekül sentezinde zaman ve maliyeti düşürdüğü için büyük önem kazanmıştır. 'Click' kimyası güvenilir, hızlı ve yüksek seçici tepkimeleri bir arada bulundurur. Azid ve alkinlerin Cu(I)-katalizörlü 1,3-dipolar siklokatılmasıyla 1,4- disübstitüe 1,2,3-triazollerin sentezi en yaygın olanıdır. Bu çalışmada yeni mono ve bis triazol türevlerinin sentezi yapılmış ve Gaussian09 paket programı kullanılarak metal koordinasyon karakteristikleri incelenmiştir. Sonuç olarak mono triazollere nazaran daha fazla koordinasyon noktası içeren bis triazollerin daha kuvvetli kompleksler oluşturduğu gözlemlenmiştir. Bilgisayarlı hesaplamalar B3LYP/LanL2DZ hesap seviyesi kullanılarak gerçekleştirilmiştir.
The Recovery of Valuable Metals From Aqueous Media by p(n-HMA-ko-ATU) Hydrogels
(2012) Karakoyun, Necdet; Aktaş, Nahit
Bu çalışmada, p (n-Hidroksimetil-Akrilamit-ko-1-Alil-2-tiyoüre), p (n-HMA-ko-ATU) hidrojelleri, n-Hidroksimetil-Akrilamit (n-HMA) monomeri ile ko-monomeri olan 1-Alil-2-Tiyoüre (ATU) ve çapraz bağlayıcı olarak N,N-Metilenbisakrilamit (MBA) eklenerek serbest radikal çapraz bağlanma kopolimerizasyonu ile sentezlenmiştir. p(n-HMA-ko-ATU) kopolimerleri, altın kazanımında sorbent olarak kullanılması çalışıldı. Elementel analiz ile kükürt (S) içeriği ve şişme deneyleri ile hidrojellerin karakteristik şişme davranışları incelenmiştir. Çözelti pH'ın altın absorpsiyonuna etkisi ve maden filizi örneklerinden altın iyonlarının kazanımı için çalışmalar incelenmiştir. Çözeltiden altın ölçümleri için Grafit Fırın Atomik Absorbsiyon Spektroskopisi (GF-AAS) ve Alev Atomik Absorbsiyon Spektroskopisi (FAAS) kullanıldı.Anahtar sözcükler: Hidrojel; Soft materyaller; altın kazanımı, ekstraksiyon, ayırma ve saflaştırma
The Theoretical Description for Psilocin Electrochemical Determination Over Cobalt Oxyhydroxide
(Univ Federal Mato Grosso Sul, dept Quimica, 2023) Tkach, Volodymyr V.; Kucher, Mykhailo M.; Kushnir, Marta, V; Ivanushko, Yana G.; Akinay, Yuksel; Karakoyun, Necdet; Kormosh, Zholt O.
The possibility of psilocin electrochemical determination and electropolymerization over cobalt (III) oxyhydroxide-modified anode is evaluated from the mathematical point of view. This process may be aimed for rapid and sensitive psilocin electrochemical determination method and for psilocin conversion to a green conducting polymer composite. Psilocin is thereby oxidized yielding either micro-or macromolecular product, being both of them important for the economical and green conducting polymer composite for electrocatalysis, electroanalysis and energy conversion. The analysis of the correspondent mathematical model confirms, that, despite of the high probability of the oscillatory behavior, the electrochemical process is efficient from both analytical and synthetical point of view.[GRAPHIC]