Researcher:
Eroğlu, Zafer

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Zafer

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Eroğlu

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    Publication
    Solar-light-driven photocatalytic hydrogen evolution activity of gCN/WS2 heterojunctions incorporated with the first-row transition metals
    (Elsevier Science Sa, 2023) Acar, Eminegul Genc; Aslan, Emre; Patir, Imren Hatay; Department of Chemistry; Department of Chemistry; Yılmaz, Seda; Eroğlu, Zafer; Metin, Önder; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences
    The design of semiconductor-based heterojunctions is an effective strategy to build highly active photo-catalyst systems. In this study, tungsten disulfide (WS2) modified graphitic carbon nitride (gCN) hetero-junction (gCN/WS2) is incorporated with Co and Ni (gCN/WS2-Co and gCN/WS2-Ni) to enhance the photocatalytic hydrogen evolution reaction (HER) activity of gCN/WS2 via performing a chemical reduction method and characterized by advanced analytical techniques. The photocatalytic HER activities of gCN, gCN/ WS2, gCN/WS2-Ni and gCN/WS2-Co were measured as 0.126, 0.221, 0.237 and 0.249 mmol g-1h-1, respec-tively, under the visible light irradiation. The improvement of photocatalytic activity and stability of gCN/ WS2-Ni and gCN/WS2-Co nanocomposites could be attributed to the 2D/2D heterojunction structure, ex-tended light harvesting ability, increased electron-hole lifetime and decreased recombination rate of the charge carriers. Moreover, mechanistic studies revealed that a S-scheme heterojunction is attributed to the enhanced photocatalytic HER by the gCN/WS2-Ni and gCN/WS2-Co photocatalysts, which provides pro-moted efficiency by photocarrier transfer and separation.
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    PublicationOpen Access
    Black phosphorus/WS2-TM (TM: Ni, Co) heterojunctions for photocatalytic hydrogen evolution under visible light illumination
    (MDPI, 2023) Acar, Emineguel Genc; Çekceoglu, Ilknur Aksoy; Aslan, Emre; Patir, Imren Hatay; Department of Chemistry; Department of Chemistry; Yılmaz, Seda; Eroğlu, Zafer; Metin, Önder; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences
    Black phosphorus (BP) has recently emerged as a versatile photocatalyst owing to its unique photophysical properties and tunable bandgap. Nonetheless, the rapid recombination of the photogenerated charges of pristine BP samples has significantly hindered its practical applications in photocatalysis. Herein, we report, for the first time, the effect of transition metal nanoparticles (Ni and Co) as co-catalysts on the photocatalytic activity of BP/tungsten disulfide (WS2) binary heterojunctions (BP/WS2-TM (TM: Ni, Co)) in the hydrogen evolution reaction (HER) under visible light irradiation (& lambda; > 420 nm). Ternary heterojunctions named BP/WS2-TM (TM: Ni, Co) were synthesized via a chemical reduction method, leading to the formation of an S-scheme heterojunction, in which BP acts as a reduction catalyst and WS2 serves as an oxidation catalyst. BP/WS2-Ni and BP/WS2-Co performed substantial amounts of hydrogen generation of 9.53 mmol h(-1)g(-1) and 12.13 mmol h(-1)g(-1), respectively. Moreover, BP/WS2-Co exhibited about 5 and 15 times higher photocatalytic activity compared to the binary BP/WS2 heterojunctions and pristine BP, respectively. The enhanced photocatalytic activity of the heterojunction catalysts is attributed to the extended light absorption ability, enhanced charge separation, and larger active sites. This study is the first example of photocatalytic hydrogen evolution from water by using Ni- and Co-doped binary BP/WS2 heterojunctions.
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    Publication
    Immune compatibility of 2D bismuthene nanosheets for future combined magnetic hyperthermia and photothermal therapy
    (Mary Ann Liebert, Inc, 2023) Giro, Linda; Gurcan, Cansu; Gazzi, Arianna; Ekim, Okan; Ceylan, Ahmet; Unal, Mehmet Altay; Ari, Fikret; Cinar, Ozge Ozgenc; Besbinar, Omur; Yilmazer, Acelya; Delogu, Lucia Gemma; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Sündü, Buse; Metin, Önder; Koç University Surface Science and Technology Center (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering
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    Bismuthene nanosheets as a photodynamic and photothermal antibacterial agent under NIR light illumination
    (Elsevier Inc., 2024) Cekceoglu, Ilknur Aksoy; Patir, Imren Hatay; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Kubanaliev, Temirlan; Metin, Önder; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering
    Bacterial infections remain a significant public health burden due to the emergence of antibiotic resistance and their non-specific cytotoxic effects, leading to the search for novel antibacterial agents. Two-dimensional (2D) pnictogens, which stand out with their advantegeous properties such as large surface areas, compatibility with biological systems, and permeability across biological membranes, have emerged as potential materials in the fight against bacterial infections. By considering all these advantages, here for the first time, the antibacterial activity of 2D bismuth (Bismuthene, Biene) on Gram-negative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), Gram-positive Staphylococcus aureus (S. aureus) and Methicillin-Resistant Staphylococcus aureus (MRSA) were examined under NIR light illumination. A growth curve analysis was conducted with a concentration of 256 mu g*mL-1 of exfoliated Biene nanosheets to assess the inhibition effect and corresponding antibacterial effect (%) against each bacterial strain. The photodynamic theraphy (PDT) and photothermal therapy (PTT)-mediated antibacterial mechanisms were explored by analyzing the generation of reactive oxygen species (ROS) via Glutathione (GSH) oxidation assay while a photothermal camera monitored temperature dynamic changes during irradiation. The high specific surface area-dependent membrane damage ability of Biene and morphological changes of the bacteria were visualized by field emission scanning electron microscope (FESEM). The exciting growth inhibition activity of Biene nanosheets for all bacterial strains was increased during irradiation, and breathtakingly the inhibition rate reached up to >= 99.1 % for P. aeruginosa, S. aureus, and MRSA. Besides, S. aureus and MRSA are more susceptible to Biene than E. coli and P. aeruginosa.
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    Nitrogen-based imperfections in graphitic carbon nitride - new trend for enhancing photocatalytic activity?
    (Wiley, 2024) Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Özer, Melek Sermin; Metin, Önder; College of Sciences
    This review comprehensively explores the engineering of nitrogen vacancies (N-vacancies) in polymeric carbon nitride (CN) and uncovering their profound impact on the photocatalytic applications of CN. The intentional creation of N-vacancies in CN obtained by removing the targeted N atoms emerges as a crucial strategy for fine-tuning its photo(catalytic)physical properties. Defect-centric investigations illuminate enlarged surface areas, increased substrate interactions and spotlight the correlation between N-vacancy and photoredox transformations. Key N-vacancies (NHx, N2C, N3C) play exceptional roles in elevating the photocatalytic activity of CN. Besides comprehensively navigating the competitive literature of CN research, this review highlights the controlled manipulation of N-vacancies in CN as an instrumental avenue for customized property tailoring. Additionally, it provides a perspective on the generation of N-vacancies considering temperature, time, and reaction atmosphere by inspecting available synthesis strategies, particularly thermal treatments, along with advanced characterization techniques shedding light on the profound influence of N-vacancies on the structural and electronic properties of CN. Moreover, this review underlines the impact of defects in CN on its photocatalytic performance, tuning bandgaps, midgap state formation, and creating active sites within the lattice. The versatile strategy employed in vacancy engineering within CN shows great potential for designing new-generation photocatalysts with tailored functionalities. This review provides a perspective for researchers in the relevant field by depicting the challenges, providing an insightful perspective, and exploring future directions aimed at catalyzing advances in the field of N-vacancy CN for various photocatalytic applications.
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    Reduced graphene oxide/few-layer phosphorene binary heterojunctions as metal-free photocatalysts for the sustainable photoredox C-H arylation of heteroarenes
    (American Chemical Society, 2024) Turbedaroglu, Özge; Kılıç, Haydar; Department of Chemistry; Department of Chemistry; Kubanaliev, Temirlan; Alemdar, Sıla; Eroğlu, Zafer; Metin, Önder; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences
    Herein, we report the fabrication of few-layer phosphorene (FLP)/reduced graphene oxide (rGO) binary heterojunctions as metal-free photocatalysts for the direct C-H arylation of heteroarenes under visible light irradiation. The FLP/rGO heterojunctions were prepared by mixing the solutions of well-exfoliated rGO and FLP nanosheets in an ultrasonic bath, resulting in a well-coupled structure between rGO and FLP. Characterization revealed enhanced stability, charge separation efficiency, and extended charge transfer ability in the heterojunction compared to the pristine materials. Studying different FLP to rGO mass ratios helped to find the optimum synergy where the materials exhibited the highest photocatalytic activity, and the optimized FLP/rGO catalyst with 30% FLP yielded the desired products with the highest photocatalytic efficiency in the C-H arylation of aryl diazonium salts and heteroarenes (24 examples in total). Notably, aryl diazonium salts with electron-withdrawing groups achieved high yields in the range of 68-90%. The FLP/rGO heterojunctions were successfully applied in synthesizing dantrolene, a commercially available drug, yielding 41% yield for C-H arylation and 90% yield for subsequent synthesis. The heterojunctions demonstrated excellent reusability, maintaining high catalytic activity over five cycles with only a 6% decrease in their initial activity. Mechanistic studies suggest a plausible single electron transfer mechanism wherein photogenerated electrons are transferred from FLP/rGO to aryl diazonium salts, forming biaryl radical intermediates and subsequent products. Overall, the FLP/rGO binary heterojunctions have been demonstrated to be efficient and sustainable metal-free photocatalysts for C-H arylation reactions, showcasing a broad substrate scope and potential applications in synthetic chemistry and pharmaceutical synthesis.
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    Publication
    Superb photo-antibacterial/antibiofilm activities of BP/WS2 and BP/MoS2 nanocomposites under near-infrared irradiation
    (American Chemical Society, 2024) Cekceoglu, Ilknur Aksoy; Acar, Eminegul Genc; Aslan, Emre; Patir, Imren Hatay; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Metin, Önder; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences
    The development of multifunctional antibacterial materials based on semiconductor materials has become the focus of treatment in the field of antibiotic-resistant bacteria. Here, for the first time, the superb photocatalytic/photothermal antibacterial activity of BP/MoS2 and BP/WS2 nanocomposites against both E. coli and S. aureus under near-infrared (NIR) or light-emitting diode (LED) illumination was demonstrated. Characterization studies using advanced instrumental techniques confirmed the successful formation of BP/WS2 and BP/MoS2 S-scheme heterojunctions with distinct structural, morphological, and compositional features. Moreover, it was verified that the enhanced photo-antibacterial activity of both heterojunctions compared to their pristine analogs was demonstrated to be due to the synergistic interactions at the atomic level elucidated by Mo/W-S-P via a sulfur atom bridge in X-ray photoelectron spectroscopy analysis, which improves the charge flow and enhances the photocatalytic performance. Optical density measurements were performed to obtain bacterial growth over 4 h, where BP/WS2 (congruent to 88%) and BP/MoS2 (congruent to 83%) showed higher NIR light-driven antibacterial activity compared to the pristine analogs (BP nanosheets, WS2 or MoS2 nanostructures), which is attributed to the S-scheme heterojunctions formed between BP and MS2 that enhance the production of ROS by promoting the use of light-induced carriers. The photo-antibacterial activities of BP/WS2 and BP/MoS2 heterojunctions reached 93% and 98%, respectively. The bacterial mechanical rupture effect of BP/WS2 and BP/MoS2 heterojunctions was monitored using SEM and E. coli was found to be more resistant to damage than S. aureus. The ability of BP/WS2 and BP/MoS2 to generate reactive oxygen species (ROS) was better than that of pristine BP nanosheets, as demonstrated by a glutathione (GSH) oxidation assay. The photothermal activities of the nanocomposites were investigated to explain the photoinduced antibacterial mechanism. In addition, the photo-antibiofilm activities of BP/WS2 and BP/MoS2 heterojunctions were also investigated and the biofilm structure of S. aureus was almost completely eradicated under LED light irradiation.
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    Femtosecond laser-mediated preparation of HfNbTaTiZr refractory high-entropy alloy nanoparticles for photothermal therapy applications: influence of solvent and fluence
    (Elsevier, 2023) Guo, Sheng; Department of Physics; Department of Physics; N/A; Department of Chemistry; Department of Chemistry; N/A; N/A; Department of Physics; Department of Chemistry; Sennaroğlu, Alphan; Morova, Yağız; Alamdari, Armin Asghari; Eroğlu, Zafer; Metin, Önder; Motallebzadeh, Amir; Jahangiri, Hadi; Faculty Member; Researcher; PhD Student; Researcher; Faculty Member; Researcher; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 23851; N/A; N/A; N/A; 46962; N/A; N/A
    Nanoparticles (NPs) have become popular photothermal therapy (PTT) photosensitizers because they can be targeted to cancer tissues and deliver a chemotherapeutic medication. Pulsed laser ablation in liquid media (PLAL) can produce stable colloidal NPs without any stabilizing agents. The stability, size distribution, and morphology of the produced colloids are influenced by the nature of NPs, laser parameters such as laser power, laser frequency repetition, ablation rate, and the specific ionic effects from the solvent. In this work, HfNbTaTiZr refractory high entropy alloy (RHEA) NPs were prepared by PLAL method in different solvents, including distilled water, ethanol, and n-hexane. The experiments were performed by irradiating a HfNbTaTiZr target with a femtosecond laser outputting 120-fs pulse at varying levels of ablation fluence (0.1, 0.16, 0.23 mJ/cm2). The elemental and structural characteristics of the prepared HfNbTaTiZr NPs were elucidated by using several advanced analytical techniques. The XRD pattern of NPs revealed that the liquid medium significantly affects the type of crystallized phases and the surface composition. The surface composition was studied by XPS, indicating that the fabricated NPs were oxidized. SEM and TEM analysis have evidenced the generation of NPs with an average diameter of less than 50 nm. The results revealed that the higher ablation fluence resulted in the formation of NPs with a larger average diameter. The highest intrinsic photothermal conversion efficiency and 12 °C time-dependent solvent heating produced in ethanol at 640 nm irradiation after 20 min were demonstrated.
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    A NIR-light-driven black phosphorus based nanocomposite for combating bacteria
    (Wiley-V C H Verlag Gmbh, 2022) Çekçekoğlu, İlknur Aksoy; Sevgi, Fatih; Ersöz, Mustafa; Patır, İmren Hatay; Department of Chemistry; N/A; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Küçükkeçeci, Hüseyin; Metin, Önder; Researcher; Researcher; Faculty Member; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 46962
    Nanocomposites of semiconducting two-dimensional (2D) materials provide advantageous for combating bacterial infections to overcome antibiotic resistance. In this study, the nanocomposites of 2D black phoshorus (BP) and silver nanoparticles (NPs) were prepared by anchoring as-synthesized Ag NPs on few-layer BP nanosheets via liquid self-assembly method and used as a NIR-light-driven antibacterial agent against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and Gram-positive bacteria (Enterococcus faecalis and Bacillus cereus). The BP/Ag nanocomposites showed excellent photothermal effect and oxidative stress ability to inhibit the initial logarithmic growth phase of E. faecalis and B. cereus. According to the bacterial growth curve, agar plate assay and live/dead viability test, as-synthesized BP/Ag nanocomposites were found to be more effective antibacterial agent for Gram-positive bacteria than Gram-negative bacteria. The presented NIR-light-driven BP-based nanoplatform can open a new avenue for avoiding bacterial resistance and combating pathogenic bacteria and also broad-spectrum disinfection applications.
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    Expanding the scope of 2D black phosphorus catalysis to the near-infrared light initiated free radical photopolymerization
    (Amer Chemical Soc, 2021) Kocaarslan, Azra; Yilmaz, Gorkem; Yagci, Yusuf; Department of Chemistry; Department of Chemistry; Department of Chemistry; Eroğlu, Zafer; Metin, Önder; Researcher; Faculty Member; College of Sciences; College of Sciences; N/A; 46962
    In the drive toward the development of efficient and stable inorganic semiconductor materials with broadband solar absorption ability to induce various photochemical processes is a highly attractive research field. In this study, two-dimensional (2D) few-layer black phosphorus (BP) exfoliated in a solvent is utilized as photocatalyst to initiate the polymerization of various monomers under visible and near-IR (NIR) light irradiation. Upon the light exposure, few-layer BP generates excited electrons and holes, which undergo electron transfer reactions with the onium salts to form free radicals capable of initiating free radical polymerization. Among the onium salts tested, aryldiazonium salt was found to be the most efficient in the photopolymerization process owing to its favorable reduction potential with the conduction edge potential of BP. The presented strategy also provides the possibility for the in situ preparation of BP-polymer composite materials.