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  • Küçük Resim
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    Combustion Characteristics of r-GO/g-C3N4/LaFeO3 Nanohybrids Loaded Fuel Droplets
    (Taylor and Francis Ltd., 2023) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Sert, Buse; Yontar, Ahmet Alper; Harputlu, Ersan; Ocakoğlu, Kasım
    Graphene oxide (GO), reduced graphene oxide (r-GO) and graphitic carbon nitride (g-C3N4) are two-dimensional carbon-based nanosheets that show promise in reducing emissions with their superior catalytic activity in capturing species such as NOx and CO2 thanks to their oxygen- based functional groups and active edges on their surfaces. These active surfaces also provide a scheme for the substitution of materials with high calorific value or high catalytic activity for combustion. This study focuses on the fabrication of functional nanohybrid structures customized for combustion with LaFeO3 metal oxide nanoparticles substituted on these nanosheets and their effect on the combustion behavior of gaso-line. The fabrication of r-GO/g-C3N4/LaFeO3 nanohybrid structures was carried out by a two-step hydrothermal method. The structural character-izations of the samples were confirmed by SEM and XRD analyses and their chemical states were confirmed by Raman and XPS techniques. Combustion experiments were carried out by droplet scale combustion of gasoline-based nanofuel droplets containing dilute (0.2 wt.%) and high (0.7 wt.%) concentrations of GO, r-GO, g-C3N4, g-C3N4/LaFeO3 and r-GO/g- C3N4/LaFeO3 nanoparticles. The experimental process was recorded with a high-speed camera and a thermal camera. The nanofuel droplets con-taining 0.2 wt.% g-C3N4/LaFeO3 nanohybrid structures had the highest maximum flame temperature of 519 K, and the nanofuel droplets con-taining 0.7 wt.% r-GO/g-C3N4/LaFeO3 particles had the highest maximum aggregate temperature of 1177 K. The ignition delay time decreased for all droplets with 0.2 wt.% and 0.7 wt.% particle loadings. At 0.2 wt.% concentration, g-C3N4 doped fuel droplets exhibited the lowest extinction time, while at 0.7 wt.% concentration, the lowest extinction time was measured for r-GO/g-C3N4/LaFeO3 doped fuel droplets. Fuel droplets containing g-C3N4 particles had the highest burning rate and were the fastest extinguishing fuel droplets in the electric field. In this study, it has been demonstrated that the combustion rate and energy value of hydro-carbon fuels can be increased and soot formation can be reduced at the same time with the new generation of graphene-based functional mate-rials to be created, and thus, many combustion problems can be solved simultaneously with these functional particles.
  • Küçük Resim
    Öğe
    Combustion Characteristics of r-GO/g-C3N4/LaFeO3 Nanohybrids Loaded Fuel Droplets
    (Taylor and Francis Ltd., 2023) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Sert, Buse; Yontar, Ahmet Alper; Harputlu, Ersan; Ocakoğlu, Kasım
    Graphene oxide (GO), reduced graphene oxide (r-GO) and graphitic carbon nitride (g-C3N4) are two-dimensional carbon-based nanosheets that show promise in reducing emissions with their superior catalytic activity in capturing species such as NOx and CO2 thanks to their oxygen-based functional groups and active edges on their surfaces. These active surfaces also provide a scheme for the substitution of materials with high calorific value or high catalytic activity for combustion. This study focuses on the fabrication of functional nanohybrid structures customized for combustion with LaFeO3 metal oxide nanoparticles substituted on these nanosheets and their effect on the combustion behavior of gasoline. The fabrication of r-GO/g-C3N4/LaFeO3 nanohybrid structures was carried out by a two-step hydrothermal method. The structural characterizations of the samples were confirmed by SEM and XRD analyses and their chemical states were confirmed by Raman and XPS techniques. Combustion experiments were carried out by droplet scale combustion of gasoline-based nanofuel droplets containing dilute (0.2 wt.%) and high (0.7 wt.%) concentrations of GO, r-GO, g-C3N4, g-C3N4/LaFeO3 and r-GO/g-C3N4/LaFeO3 nanoparticles. The experimental process was recorded with a high-speed camera and a thermal camera. The nanofuel droplets containing 0.2 wt.% g-C3N4/LaFeO3 nanohybrid structures had the highest maximum flame temperature of 519 K, and the nanofuel droplets containing 0.7 wt.% r-GO/g-C3N4/LaFeO3 particles had the highest maximum aggregate temperature of 1177 K. The ignition delay time decreased for all droplets with 0.2 wt.% and 0.7 wt.% particle loadings. At 0.2 wt.% concentration, g-C3N4 doped fuel droplets exhibited the lowest extinction time, while at 0.7 wt.% concentration, the lowest extinction time was measured for r-GO/g-C3N4/LaFeO3 doped fuel droplets. Fuel droplets containing g-C3N4 particles had the highest burning rate and were the fastest extinguishing fuel droplets in the electric field. In this study, it has been demonstrated that the combustion rate and energy value of hydrocarbon fuels can be increased and soot formation can be reduced at the same time with the new generation of graphene-based functional materials to be created, and thus, many combustion problems can be solved simultaneously with these functional particles.
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    Development of a Cr2AlC MAX phase/g-C3N4 composite-based electrochemical sensor for accurate cabotegravir determination in pharmaceutical and biological samples
    (Springer, 2024) Bouali, Wiem; Genc, Asena Ayse; Erk, Nevin; Kaya, Gul; Sert, Buse; Ocakoğlu, Kasım
    A highly sensitive electrochemical sensor is reported that employs a modified electrode for the precise measurement of cabotegravir, a potent anti-HIV drug. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were utilized for this purpose. Electrode modification involved the immobilization of Cr2AlC MAX phase/g-C3N4 onto a glassy carbon electrode (GCE) to enhance its electrocatalytic activity and selectivity for cabotegravir detection. Under the optimal experimental conditions, the working potential (vs. Ag/AgCl) was to 0.93 V. The developed sensor exhibited a good linear relationship in the range 0.05 µM to 9.34 µM with a low limit of detection of 4.33 nM, signifying its exceptional sensitivity. Additionally, it demonstrated successful cabotegravir detection in pharmaceutical formulations and biological samples, achieving an RSD below 3.0%. The recoveries fell within the range 97.7 to 102%, confirming the sensor's potential for real-sample applications. This innovative electrochemical sensor represents a significant advancement, providing a simple, reliable, and sensitive tool for the accurate measurement of cabotegravir. Its potential applications include optimizing drug dosages, monitoring treatment responses, and supporting the development of cabotegravir-based pharmaceutical products, thereby contributing to advancements in HIV therapy and prevention strategies.
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    Evaluating the simultaneous electrochemical determination of antineoplastic drugs using LaNiO3/g-C3N4@RGH nanocomposite material
    (Elsevier, 2024) Bouali, Wiem; Erk, Nevin; Sert, Buse; Harputlu, Ersan
    A novel electrochemical sensor based on LaNiO3/g-C3N4@RGH nanocomposite material was developed to simultaneously determine Ribociclib (RIBO) and Alpelisib (ALPE). Ribociclib and Alpelisib are vital anticancer medications used in the treatment of advanced breast cancer. The sensor exhibited excellent electrocatalytic activity towards the oxidation of RIBO and ALPE, enabling their simultaneous detection. The fabricated sensor was characterized using various techniques, including energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), which confirmed the successful synthesis of the LaNiO3/g-C3N4@RGH composite material. Electrochemical characterization revealed enhanced conductivity and lower resistance of the modified electrode compared to the bare electrode. The developed sensor exhibited high repeatability, reproducibility, stability, and selectivity toward RIBO detection. Furthermore, the sensor displayed high sensitivity with low detection limits of 0.88 nM for RIBO and 6.1 nM for ALPE, and linear ranges of 0.05–6.2 μM and 0.5–6.5 μM, respectively. The proposed electrochemical sensor offers a promising approach for simultaneously determining RIBO and ALPE in pharmaceutical formulations and biological samples with recovery data of 98.7–102.0 %, providing a valuable tool for anticancer drug analysis and clinical research.
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    Grafitik karbon nitrür ve bor nitrür içeren kompozit yapıların hazırlanması; çevre ve enerji uygulamaları
    (2022) Sert, Buse
    Yarı iletken nanokompozit malzemeler son yıllarda çevresel iyileĢtirme ve enerji uygulamaları için yoğun ilgi görmektedir. Bu tez çalıĢması kapsamında nanamalzeme katkılı membranlar ve süperkapasitörler üretilmiĢtir. Yüksek termal stabilitesi ve iyi dağılabilirlik, kimyasal kararlılık, elektriksel yalıtım özellikleri ve toksik olmamaları sebebiyle grafitik karbon nitrür (g-C3N4) ve bor nitrür kuantum noktalar (BNKN) bu uygulamalarda nanokompozit malzemelerin esas bileĢenleri olarak kullanılmıĢtır. g-C3N4 ve BNKN üretimi sırasıyla sinterleme ve hidrotermal iĢlem ile gerçekleĢtirilmiĢtir. Nanomalzemelerin çevresel uygulamalarında, ağırlıkça % 0.5, % 1.0 ve % 2.0 g-C3N4 veya BNKN içeren polietersülfon (PES) membranlar (gC3N4@PES, BNKN@PES) bir döküm ünitesinde üretilmiĢtir. Membranların saf su akı geçirgenlik performansı ile birlikte membran tıkanıklığını önleme ve kirlilik çalıĢmaları da araĢtırılmıĢtır. Hibrit membranların, saf PES membrandan daha iyi temizleme özelliği sergilediği görülmüĢtür. Enerji uygulamalarında kullanılmak üzere, g-C3N4 veya BNKN içeren grafen elektrotlar hazırlanmıĢtır. Bu kapsamda, farklı miktarlarda alınan g-C3N4 veya BNKN (15 mg / 30 mg / 60 mg), indirgenmiĢ grafen oksit (rGO) (30 mg) ile hidrotermal iĢleme tabii tutularak, süperkapasitör uygulamalarında kullanılabilecek elektrotlar (gC3N4@rGOH ve BNKN@rGOH) hazırlanmıĢ ve uygun tekniklerle (XRD, SEM, CV, BET, ZETA) karakterize edilmiĢtir. Bu hibrit yapılardan üretilen elektrotların spesifik kapasitans değerleri, empedans eğrileri ve Ģarj/deĢarj performansları elektrokimyasal teknikler ile analiz edilmiĢtir. g-C3N4@rGOH (30 mg/15 mg oranlarında) hazırlanan elektrotun 157.4 F g -1 spesifik kapasitans değeri ile en yüksek performansa sahip olduğu bulunmuĢtur. EĢit oranlarda hazırlanan BNKN@rGOH (30 mg/30 mg oranlarında) ii hibrit yapısından ise 207.25 F g-1 spesifik kapasitans değeri ile en yüksek performansa sahip olduğu bulunmuĢtur. Bu tez çalıĢmasından elde edilen sonuçlara göre; üretilen hibrit yapıların, çevre ve enerji uygulamalarında gelecek vaad ettiği görülmektedir.
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    Immobilization of Alpha-Amylase onto Ni2+ Attached Carbon Felt: Investigation of Kinetic Parameters from Potato Wastewater
    (Wiley, 2023) Acet, Ömür; İnanan, Tülden; Öndül Koç, Eda; Sert, Buse; Önal Acet, Burcu; Odabaşı, Mehmet; Ocakoğlu, Kasım; Dizge, Nadir
    α-amylase is an important enzyme for textile, food, paper, and the pharmaceutical industrial areas. In this study, Ni2+ attached carbon felt structures with nitrogen active site (Ni2+-N-ACF) are produced. The surface morphologies of the N-ACF and Ni2+-N-ACF are investigated by means of scanning electron microscopy (SEM) analysis. Ni2+ ions binding on the N-ACFs are determined by energy dispersive X-ray (EDX) analysis and a graphite furnace atomic absorption spectrometer (AAS). The effect of pH, ionic strength, initial α-amylase concentration, and temperature parameters is investigated for α-amylase immobilization on Ni2+-N-ACF structures. In addition, pH and temperature effect on the activities of the free and the immobilized amylase, kinetic parameters, storage, and operational stabilities are made. Lastly, starch degradation in potato waste water is tested on Ni2+-N-ACF. The obtained results show that α-amylase immobilized Ni2+-N-ACF can be used for starch degradation on an industrial scale.
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    A New Design to Enhance the Enzyme Activities: Investigation of L-Asparaginase Catalytic Performance by IMAC Effect on g-C3N4 Nanolayers
    (Springer Link, 2024) Sert, Buse; Acet, Ömür; Noma, Samir Abbas Ali; Osman, Bilgen; Odabaşı, Mehmet; Ocakoğlu, Kasım
    Recently, graphite carbon nitride (g-C3N4) has come to the fore as a new material with its carbon-based two-dimensional structure, simple preparation procedure, and excellent physicochemical stability properties. This study aims to investigate the activity and kinetic studies of the L-asparaginase enzyme via immobilized metal ion affinity chromatography (IMAC) process of g-C3N4 nanolayers. Firstly, g-C3N4 nanolayers were synthetized and Ni2+ ions were binded their surfaces. The synthesized samples were investigated by SEM, ICP-MS, XRD, and FTIR. The highest L-ASNase adsorption on Ni2+-g-C3N4 nanostructures was 444.1 mg/g, at 3 mg/mL L-ASNase concentration. Optimal medium conditions for L-ASNase adsorption occurred at pH 8.0 and 25 °C. The immobilized enzyme showed improved stability relating to the soluble enzyme in extreme situations. On the other hand, the storage stability and reusability of the immobilized enzyme were found to be approximately 64 and 53% of the original activity after 29 days at room temperature and 10 cycles, respectively. From the Michaelis–Menten constants Km and Vmax, both of them decreased after immobilization compare to the free one. The obtained outcomes showed that the g-C3N4 is a suitable matrix for L-asparaginase immobilization with ideal catalytic efficiency and improved stability.
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    Synthesis of PES membranes modified with polyurethane–paraffin wax nanocapsules and performance of bovine serum albumin and humic acid rejection
    (IWA Publishing, 2023) Sert, Buse; Kaya, Gul; Ozay, Yasin; Alterkaoui, Aya; Ocakoglu, Kasım; Dizge, Nadir
    Membrane fouling is a serious handicap of membrane-based separation, as it reduces permeation flux and hence increases operational and maintenance expenses. Polyurethane–paraffin wax (PU/PW) nanocapsules were integrated into the polyethersulfone membrane to manufacture a composite membrane with higher antifouling and permeability performance against humic acid (HA) and bovine serum albumin (BSA) foulants. All manufactured membranes were characterized by scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and contact angle. The contact angle of the pristine polyethersulfone (PES) membrane was measured 73.40 + 1.32. With the embedding of nanocapsules, the contact angle decreased to 64.55 + 1.23 for PES/PU/PW 2.0 wt%, and the pure water flux of all composite membranes increased when compared to pristine PES. The pristine PES membrane also has shown the lowest steady-state fluxes at 45.84 and 46.59 L/m2 h for BSA and HA, respectively. With the increase of PU/PW nanocapsule ratio from 0.5 to 1.0 wt%, steady-state fluxes increased from 51.96 to 71.61 and from 67.87 to 98.73 L/m2 h, respectively, for BSA and HA. The results depicted that BSA and HA rejection efficiencies of PU/PW nanocapsules blended PES membranes increased when compared to pristine PES membranes