Yazar "Unlu, C. Gokhan" seçeneğine göre listele

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    Bimodal functionality of highly conductive nanostructured silver film towards improved performance of photosystem I-based graphene photocathode
    (Elsevier Science Sa, 2025) Szalkowski, Marcin; Kiliszek, Malgorzata; Harputlu, Ersan; Izzo, Miriam; Unlu, C. Gokhan; Mackowski, Sebastian; Ocakoglu, Kasim
    We present the novel design of photosystem I (PSI)-based biosolar cell, whereby conductive transparent electrode materials, such as ITO or FTO, are replaced with glass covered with silver island film. This nanostructured metallic layer combines high electric conductance with enhancing the absorption efficiency of the PSI biocatalyst via the plasmonic effect. We demonstrate strong enhancement of the photocurrent generated in the biohybrid electrode composed of oriented layers of PSI reaction centers due to plasmonic interactions of the PSI fluorophores and redox centres with the conductive silver island film.
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    Influence of silane coating and graphene oxide integration on the magnetothermal Behaviors of La1-xSrxMnO3 nanoparticles
    (Elsevier, 2025) Sert, Buse; Kaya, Gul; Cicek, Sinem; Harputlu, Ersan; Simsek, Telem; Tekgul, Atakan; Unlu, C. Gokhan
    In this study, La1-xSrxMnO3 (x = 0.27, 0.3, 0.33) magnetic nanoparticles (MNPs) were synthesized and then these nanoparticles synthesized in the core-shell structure were coated with silane for potential magnetic hyperthermia applications. In order to provide support material for the coated magnetic nanoparticles, silane-coated hybrid magnetic nanoparticles were obtained by producing graphene oxide (GO) nanoflakes. The structural and magnetic properties and magnetothermal properties of these structures were investigated. It was observed that the structure of the silane-coated magnetic nanoparticles remained intact and did not show any degradation compared to the uncoated materials. In addition, the highest saturation magnetization (MS) value was observed in the sample doped with x = 0.30. This value indicated that the heating power would be higher than the other doped samples in the specific absorption ratio (SAR) measurements. In this context, the heating amount in the silane-coated samples showed a slight decrease compared to the uncoated samples. Despite the decrease in the SAR values of the integrated samples by incorporating GO into the coated MNPs, it is anticipated that effective results will be obtained for practical applications with the advantage of increasing the thermal conductivity of GO.
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    Investigating the effect of coating and synthesis parameters on La1-xSrxMnO3 based core-shell magnetic nanoparticles
    (Elsevier, 2025) Sert, Buse; Kaya, Gul; Tataroglu, Aleyna Akcay; Harputlu, Ersan; Simsek, Telem; Tekguel, Atakan; Unlu, C. Gokhan
    Magnetic nanoparticles are an important class of functional materials that have unique magnetic properties due to their reduced size (<100 nm) and have the potential for use in many fields. In the preparation of magnetic nanoparticles, factors such as intrinsic magnetic properties, surface coating, size and shape of the particles, surface charge and stability are very important. In this regard, carefully determining the synthesis parameters of magnetic nanoparticles and particle coating materials is of critical importance in the application area chosen for the material. In this study, La1-xSrxMnO3 (x = 0.27, 0.30, 0.33) magnetic nanoparticles (MNPs), carbon-coated magnetic nanoparticles in core-shell structure (C@MNP) and their derivatives integrated into graphene oxide (GO-C@MNP) were synthesized and their properties were investigated in detail for their use in possible future application studies. The crystal structure of perovskite compounds with Pbnm symmetry remains unchanged after carbon coating but shrinks in volume due to its amorphous structure. The magnetic behavior of the uncoated and coated materials is almost identical, but the Curie temperature of the compounds shifts to a higher temperature. In the specific absorption ratio (SAR) measurements performed, it was found that the best SAR value for carbon-coated MNPs was 12.9 W/g at x = 0.27. By integrating the MNPs into graphene oxide, heat is easily distributed regionally, and this shows that the structures can be ideal candidates for applications such as hyperthermia, drug carriers, tissue repair, and cellular therapy including cell labeling and targeting. Perovskite-structured manganite materials were selected for their suitability in controlled production, where the Curie temperature can be tuned near the therapeutic temperature by adjusting the doping levels, making them ideal for magnetic hyperthermia applications. In this study, for the first time, the nanoparticle surfaces were coated with carbon, which was chosen not only due to carbon's non-magnetic nature but also because it provides an ideal platform for future combined biomedical applications such as drug delivery systems.
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    Investigation of in vitro biological activities of hollow mesoporous carbon nanoparticles bearing D-NMAPPD on human lung adenocarcinoma cells
    (Elsevier, 2022) Ugur, Naz; Harputlu, Ersan; Sezer, Canan Vejselova; Demirdogen, Ruken Esra; Ince, Mine; Unlu, C. Gokhan; Yurt, Fatma
    The uniformly dispersed hollow mesoporous carbon nanoparticles (HMCNPs) were successfully synthesized by hard-template methods, and D-NMAPPD (B13) was successfully loaded onto the nanoparticle surface for the first time. Structural properties of bare and B13 loaded HMCNPs (HMCNs-B-13) were investigated by Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission-Scanning Electron Microscopy (FE-SEM), Thermal Gravimetric Analysis (TG). The amount of drug released was determined via in vitro drug release studies at 37 degrees C in SBF through UV-Vis spectrometric and thermal analyses. TG data revealed that the proportion of loaded B-13 was 33.60%. Their ability to induce apoptosis in cultures of A549 human lung adenocarcinoma cells was investigated, and the inhibitory effect of HMCNPs-B-13 on lung cancer cell proliferation was determined in vitro. The IC50 values determined after application periods of 24 and 48 h were found to be 16.13 mu g/mL and 12.96 mu g/mL, respectively. The role of HMCNPs-B-13 on the morphology and ultrastructure of A549 cells was also investigated by confocal microscopy and Transmission electron microscopy (TEM) studies.
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    Molecular mechanism of direct electron transfer in the robust cytochrome-functionalised graphene nanosystem
    (Royal Soc Chemistry, 2021) Jacquet, Margot; Kiliszek, Malgorzata; Osella, Silvio; Izzo, Miriam; Sar, Jaroslaw; Harputlu, Ersan; Unlu, C. Gokhan
    Construction of green nanodevices characterised by excellent long-term performance remains high priority in biotechnology and medicine. Tight electronic coupling of proteins to electrodes is essential for efficient direct electron transfer (DET) across the bio-organic interface. Rational modulation of this coupling depends on in-depth understanding of the intricate properties of interfacial DET. Here, we dissect the molecular mechanism of DET in a hybrid nanodevice in which a model electroactive protein, cytochrome c(553) (cyt c(553)), naturally interacting with photosystem I, was interfaced with single layer graphene (SLG) via the conductive self-assembled monolayer (SAM) formed by pyrene-nitrilotriacetic acid (pyr-NTA) molecules chelated to transition metal redox centers. We demonstrate that efficient DET occurs between graphene and cyt c(553) whose kinetics and directionality depends on the metal incorporated into the bio-organic interface: Co enhances the cathodic current from SLG to haem, whereas Ni exerts the opposite effect. QM/MM simulations yield the mechanistic model of interfacial DET based on either tunnelling or hopping of electrons between graphene, pyr-NTA-M2+ SAM and cyt c(553) depending on the metal in SAM. Considerably different electronic configurations were identified for the interfacial metal redox centers: a closed-shell system for Ni and a radical system for the Co with altered occupancy of HOMO/LUMO levels. The feasibility of fine-tuning the electronic properties of the bio-molecular SAM upon incorporation of various metal centers paves the way for the rational design of the optimal molecular interface between abiotic and biotic components of the viable green hybrid devices, e.g. solar cells, optoelectronic nanosystems and solar-to-fuel assemblies.
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    Plasmonic enhancement of photocurrent generation in a photosystem I-based hybrid electrode
    (Royal Soc Chemistry, 2020) Szalkowski, Marcin; Harputlu, Ersan; Kiliszek, Malgorzata; Unlu, C. Gokhan; Mackowski, Sebastian; Ocakoglu, Kasim; Kargul, Joanna
    We experimentally demonstrate that oriented assembly of red algal photosystem I (PSI) reaction centers on a plasmonically active Silver Island Film (SIF) leads to strong enhancement of both the fluorescence intensity and photocurrent generated upon illumination. PSI complexes were specifically attached to a monolayer of graphene deposited on the SIF layer. The results of comprehensive fluorescence microscopy point to the critical role of the SIF layer in enhancing the optical response of PSI, as we observe increased emission intensity. Hence, importantly, the strong increase of photocurrent generation demonstrated for the biohybrid electrodes can be directly associated with the plasmonic enhancement of the optical and electrochemical functionalities of PSI. The results also indicate that the graphene layer is not diminishing the influence of the plasmonic excitations in SIF on the absorption and emission of PSI.