Researcher:
Çavuşlar, Özge

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PhD Student

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Özge

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Çavuşlar

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Çavuşlar, Özge

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2018 - 201912020 - 20224

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Researcher Of Publications: search.filters.isAuthorOfPublication.cfa2b628-5ca7-432e-a562-2d32521bf196

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    pH and molecular weight dependence of auric acid reduction by polyethylenimine and the gene transfection efficiency of cationic gold nanoparticles thereof
    (Royal Society of Chemistry (RSC), 2018) N/A; N/A; N/A; N/A; Department of Chemistry; N/A; Department of Chemistry; Çavuşlar, Özge; Celaloğlu, Çağnur; Duman, Fatma Demir; Konca, Yeliz Utku; Yağcı, Mustafa Barış; Acar, Havva Funda Yağcı; PhD Student; Undergraduate Student; PhD Student; Teaching Faculty; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; College of Sciences; College of Sciences; N/A; N/A; N/A; N/A; 111280; N/A; 178902
    Small, cationic gold nanoparticles (GNP) are produced by the direct reduction of auric acid in a non-reducing solvent, water, with branched polyethylenimine (bPEI) in a broad pH range (3.0-9.0). Basic pH, which is studied for the first time, emerged as a favorable condition to achieve good reducing power and surface passivation simultaneously, providing smaller particles (hydrodynamic size ca. 6 nm) with enhanced long-term stability and a sharper surface plasmon peak (SPP). This synthetic method produces colloidal GNPs with bPEI in a broad molecular weight range (0.6, 1.8, 10 and 25 kDa). The molecular weight did not influence the crystal size much but did affect the hydrodynamic size and the stability. 0.6 kDa bPEI provides the largest GNPs (ca. 100 nm aggregates) which lack long term stability. 1.8 kDa bPEI provides small particles (hydrodynamic size ca. 7 nm) with the sharpest SPP. The GNPs prepared with 25 and 1.8 kDa bPEI show no significant cytotoxicity in HEK 293T cells and PEI25-Au transfects green fluorescent protein (GFP) into HEK 293T cells more efficiently (82%) than FuGENE (R) (50%). This simple one pot synthesis of cationic GNPs in water is a valuable, simple alternative for the generation of new cationic GNPs in water with even low molecular weight PEI.
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    Gold nanoparticle decorated carbon nanotube nanocomposite for dye-sensitized solar cell performance and stability enhancement
    (Elsevier, 2021) Mohammadnezhad, Mahyar; Selopal, Gurpreet Singh; Barba, David; Durmusoglu, Emek G.; Wang, Zhming M.; Lopinski, Gregory P.; Stansfield, Barry; Zhao, Haiguang; Rosei, Federico; N/A; Department of Chemistry; Çavuşlar, Özge; Acar, Havva Funda Yağcı; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Science; N/A; 178902
    Improving the conversion efficiency of dye-sensitized solar cells (DSSCs) requires enhancing the photogeneration of charge carriers as well as facilitating their transport to electrodes before charge recombination or quenching can occur. Here we describe a simple, fast and large-area scalable procedure for the preparation of a nanocomposite made of functional gold nanoparticles (AuNPs) and multiwall carbon nanotubes (MWCNTs) to improve the performance of DSSCs. We fabricated AuNP/MWCNT inlaid mesoporous TiO2 films as photoanodes in DSSCs, to improve crucial factors including light absorption, charge-carrier generation, collection and transport. By using a AuNP/MWCNT nanocomposite directly inlaid in TiO2 as the working electrode, a power conversion efficiency (PCE) of 6.61% and short-circuit photocurrent density (Jsc) of 12.26 mA cm-2 were obtained, representing an enhancement of -31% in PCE and -19% in Jsc compared to a control cell based on TiO2 alone. In addition, DSSCs based on the TiO2/AuNP/MWCNT photoanode remained remarkably stable compared with the control device, retaining 92% of the initial PCE value after ten days of continuous illumination.
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    IgG-Conjugated gold nanoparticles restore blood-brain barrier damage in both in vitro and in vivo models of sepsis
    (Wiley, 2022) Esen, Figen; Orhun, Gunseli; Ozcan, Perihan Ergin; N/A; N/A; Department of Chemistry; N/A; N/A; N/A; N/A; N/A; N/A; Akcan, Uğur; Çavuşlar, Özge; Acar, Havva Funda Yağcı; Temizyürek, Arzu; Bakbak, Haşim; Altunsu, Deniz; Ayvaz, Ecem; Ahıshalı, Bülent; Kaya, Mehmet; PhD Student; PhD Student; Faculty Member; Other; Doctor; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; School of Medicine; Graduate School of Health Sciences; Graduate School of Health Sciences; School of Medicine; School of Medicine; N/A; N/A; N/A; N/A; Koç University Hospital; N/A; N/A; N/A; N/A; N/A; N/A; 178902; 357912; N/A; N/A; N/A; 9509; 10486
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    PublicationOpen Access
    Synthesis of stable gold nanoparticles using linear polyethyleneimines and catalysis of both anionic and cationic azo dye degradation
    (Royal Society of Chemistry (RSC), 2020) Abkenar, Sirous Khabbaz; Ow-Yang, Cleva W.; N/A; Department of Chemistry; Çavuşlar, Özge; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902
    Reduction of auric acid with polyethyleneimine (PEI) provides a simple, low-cost alternative for the production of cationic gold nanoparticles (GNPs). However, linear PEI (lPEI) failed to produce small, colloidally stable GNPs, so far. Since lPEI is a polyelectrolyte, pH should be an important factor both in reduction and stabilization of GNPs and may be optimized to produce small and stable lPEI/GNPs. Cationic GNPs were produced by the direct reduction of auric acid in water with lPEI utilizing two different methods to dissolve the polymer: by protonation or at high temperature. The influence of pH on the particle formation and properties was studied over a wide pH range (3.5 to 10). The impacts of the PEI/Au mass ratio, polymer molecular weight (2.5 and 25 kDa) and post-synthetic pH on the particle properties were also studied. Best is to dissolve lPEI by protonation and to clean the GNPs via controlled centrifugal precipitation. The MW did not influence the hydrodynamic size, stability or particle shape, but low MW lPEI provided faceted particles. This simple one pot synthesis of small, stable cationic GNPs in water is a valuable, simple alternative for producing new cationic GNPs with even low molecular weight lPEI. Additionally, these GNPs were evaluated as catalysts in the degradation of methyl orange (MO) (anionic-zwitterionic) and methylene blue (MB) (cationic) azo dyes at different pH values. The fastest degradation of MO and MB was recorded at pH 7.5 and 3.5, respectively. Overall, this is a rare case where a single catalyst quickly and effectively catalyzes the degradation of both cationic and anionic dyes.
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    PublicationOpen Access
    Synergistic effect of plasmonic gold nanoparticles decorated carbon nanotubes in quantum Dots/TiO2 for optoelectronic devices
    (Wiley, 2020) Selopal, Gurpreet Singh; Mohammadnezhad, Mahyar; Besteiro, Lucas, V.; Liu, Jiabin; Zhang, Hui; Navarro-Pardo, Fabiola; Liu, Guiju; Wang, Maorong; Sun, Shuhui; Zhao, Haiguang; Wang, Zhiming M.; Department of Chemistry; N/A; Acar, Havva Funda Yağcı; Çavuşlar, Özge; Durmuşoğlu, Emek Göksu; Faculty Member; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; 178902; N/A; N/A
    Here, a facile approach to enhance the performance of solar-driven photoelectrochemical (PEC) water splitting is described by means of the synergistic effects of a hybrid network of plasmonic Au nanoparticles (NPs) decorated on multiwalled carbon nanotubes (CNTs). The device based on TiO2–Au:CNTs hybrid network sensitized with colloidal CdSe/(CdSexS1−x)5/(CdS)1 core/alloyed shell quantum dots (QDs) yields a saturated photocurrent density of 16.10 ± 0.10 mA cm−2 [at 1.0 V vs reversible hydrogen electrode (RHE)] under 1 sun illumination (AM 1.5G, 100 mW cm−2), which is ≈26% higher than the control device. The in-depth mechanism behind this significant improvement is revealed through a combined experimental and theoretical analysis for QDs/TiO2–Au:CNTs hybrid network and demonstrates the multifaceted impact of plasmonic Au NPs and CNTs: i) hot-electron injection from Au NPs into CNTs and TiO2; ii) near-field enhancement of the QDs absorption and carrier generation/separation processes by the plasmonic Au NPs; iii) enhanced photoinjected electron transport due to the highly directional pathways offered by CNTs. These results provide fundamental insights on the properties of QDs/TiO2–Au:CNTs hybrid network, and highlights the possibility to improve the performance of other solar technologies.