Browsing by Author "Doger, Hilal"

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Citation - WoS: 7
Citation - Scopus: 8
Ag-Intercalation of Tm3+/Er3+ Co-Doped Layered Perovskites and Their Exfoliated 2d Nanosheets With an Enhanced Antibiofilm and Antibacterial Activity
(Elsevier, 2022) Gunay, Bensu; Doger, Hilal; Karagonlar, Zeynep Firtina; Saglam, Ozge
There is a significant demand for antibiofilm and antimicrobial materials in the medical device industry. It is well established that Ag-based compounds have a high antimicrobial efficiency. Without being in a lattice, silver's antimicrobial action is mainly mediated by the release of Ag+ ions from the compound. These ions at high levels are toxic to most bacterial species. However, rapidly released Ag+ ions tend to aggregate and lose their anti-bacterial effect over time. Thus, utilizing a new approach for using silver as an antimicrobial agent based on imparting the antimicrobial action through contact, rather than releasing Ag+ ions could be beneficial. Here we report that Ag+ ions intercalation of Tm/Er co-doped layered perovskites and their 2D nanosheets exhibit antibacterial and antibiofilm activities against the human opportunistic pathogens Escherichia coli and Bacillus subtilis. Specifically, flocculation of nanosheets with Ag+ ions had efficient antibacterial and antibiofilm activity at 100 mu g/mL. In addition, the flocculated product demonstrated low in vitro cytotoxicity against the Huh7 hepatocellular carcinoma cell line and HEK 293 embryonic kidney cell line. Our results indicate that Ag-intercalated layered perovskites and the flocculation of the nanosheets hold great promise to be used for anti-microbial and antibiofilm purposes in biomedical engineering applications.
Citation - WoS: 6
Citation - Scopus: 6
Nanolitography Based on Electrospun and Etched Nanofibers
(Elsevier, 2021) Noori, Aileen; Doger, Hilal; Demirhan, Yasemin; Ozdemir, Mehtap; Ozyuzer, Lutfi; Aygun, Gulnur; Saglam, Ozge
In this study, we propose a new type of nanolithography procedure to fabricate orderly patterned metallic nanostructures using the electrohydrodynamic method and the reactive ion etching process. The electrohydrodynamic process parameters were tuned so as to create patterning with precision, and fibers in nanoscale on silver-coated substrates. We also studied reactive ion etching with different durations on the well-patterned samples. The experiments show that applying a voltage of 400 V resulted in straight patterned fibers with a diameter of 208.7 ? 30.3 nm. The statistical analysis on scanning electron microscope (SEM) images showed a significant difference in the diameter of the fibers fabricated at 400 V compared to those at 500 V and 600 V. We also confirm that the etching process has no affect on the fiber diameter. Moreover, electron dispersive X-Ray spectrometer (EDX) results suggest that an etching duration of 7 min is sufficient to remove the silver coating that is not covered with the fibers, and protect the silver nanostructures underneath the fibers. Utilizing a lowcost nanolithography procedure, we obtain the orderly patterned silver nanostructures for possible integration into miniaturized devices.
Citation - WoS: 6
Citation - Scopus: 6
Synthesis of Upconverting Nanosheets Derived From Er-Yb and Tm-Yb Co-Doped Layered Perovskites and Their Layer-By Assembled Films
(Elsevier, 2022) Gunay, Bensu; Suer, Ozge; Doger, Hilal; Arslan, Ozlem; Unal, Ugur; Saglam, Ozge
Here, we investigated the structure and upconversion (UC) properties of new-type of single oxide nanosheets, derived from the Er3+/Yb3+ and Tm3+/Yb3+ co-doped Ruddlesden-Popper type layered perovskites, and their layer-by-layer (LBL) self-assembled nanofilms. The single oxide nanosheets, obtained by exfoliation of the proton-exchanged K2La2Ti3O10, had the thickness in the range of 2-3 nm indicating good consistency with the theoretical thickness and lateral size from 500 nm up to 2 mu m. Er3+/Yb3+, Tm3+/Yb3+ and Tm3+/Er3+co-doped nanosheets were used as building blocks of the multilayer films deposited by layer-by-layer procedure. The LBL films composed of 2.5 % Er3+ + 5 % Yb3+, 2.5 % Tm3+ + 20 % Yb3+, 2.5 % Tm3+ + 20 % Er3+ after 60 sequences have shown a white emission confirmed by the CIE chromaticity diagram. The possible UC energy transfer of LBL films fabricated after 30 sequences using the nanosheets derived from the 2.5 % Er3+ + 5 % Yb3+ co-doped layered perovskites was also suggested. The number of photons participating in the UC process was confirmed as two-photon for both green and red UC emissions due to the F-4(9/2) -> I-4(15/2) and H-2(11/2), S-4(3/2) -> I-4(15/2) transitions, respectively.