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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access Emergence of near-infrared photoluminescence via ZnS shell growth on the AgBiS2 nanocrystals(American Chemical Society, 2024) Department of Chemistry; Department of Electrical and Electronics Engineering; Önal, Asım; Kaya, Tarık Safa; Metin, Önder; Nizamoğlu, Sedat; Department of Chemistry; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of EngineeringAgBiS2 nanocrystals (NCs), composed of nontoxic, earth-abundant materials and exhibiting an exceptionally high absorption coefficient from visible to near-infrared (>105 cm(-1)), hold promise for photovoltaics but have lack of photoluminescence (PL) due to intrinsic nonradiative recombination and challenging shell growth. In this study, we reported a facile wet-chemical approach for the epitaxial growth of ZnS shell on AgBiS2 NCs, which triggered the observation of PL emission in the near-infrared (764 nm). Since high quality of the core is critical for epitaxial shell growth, we first obtained rock-salt structured AgBiS2 NCs with high crystallinity, nearly spherical shape and monodisperse size distribution (<6%) via a dual-ligand approach reacting Ag-Bi oleate with elemental sulfur in oleylamine. Next, a zincblende ZnS shell with a low-lattice mismatch of 4.9% was grown on as-prepared AgBiS2 NCs via a highly reactive zinc (Zn(acac)(2)) precursor that led to a higher photoluminescence quantum yield (PLQY) of 15.3%, in comparison with a relatively low reactivity precursor (Zn(ac)(2)) resulting in reduced PLQY. The emission from AgBiS2 NCs with ultrastrong absorption, facilitated by shell growth, can open up new possibilities in lighting, display, and bioimaging.Publication Open Access Protocol on synthesis and characterization of copper-doped InP/ZnSe quantum dots as ecofriendly luminescent solar concentrators with high performance and large area(Elsevier, 2021) Department of Electrical and Electronics Engineering; N/A; N/A; Department of Chemistry; Nizamoğlu, Sedat; Sadeghi, Sadra; Eren, Güncem Özgün; Shahzad, Mehwish; Faculty Member; PhD Student; Department of Electrical and Electronics Engineering; Department of Chemistry; College of Engineering; Graduate School of Sciences and Engineering; 130295; N/A; N/A; N/ALuminescent solar concentrators (LSCs) are simple and cost-effective solar energy-harvesting devices. Indium phosphide (InP)-based colloidal quantum dots (QDs) are promising QDs for efficient LSC devices due to their environmentally benign nature. One major challenge in LSC devices is reabsorption losses. To minimize the reabsorption, Stokes shift engineering is a critical process to designing the QD material. Here, we present a protocol that contains the preparation of structurally engineered copper-doped InP/ZnSe QDs and their LSC application.Publication Open Access Cationic [6]helicenes: tuning (chir)optical properties up to the near infra-red(Elsevier, 2022) Labrador, Geraldine M.; Jacquemin, Denis; Lacour, Jerome; Department of Chemistry; Bosson, Johann; Department of Chemistry; College of SciencesThe intramolecular condensation of ortho substituents of triaryl carbenium ions can lead to the formation of cationic helicenes. These chiral and configurationally stable molecules exhibit extended optical properties reminiscent of their parent methylium ions. Among them, cationic [6]helicenes are particularly interesting as orthogonal late-stage functionalization strategies allow the introduction of a variety of auxochromes with different regiochemistry. Intense chiroptical properties can thus be tailored in the far red and up to the near infra-red (NIR) spectral windows. A wealth of applications can be foreseen, in particular in material sciences.Publication Open Access Hydrogen-bonded multilayers of micelles of a dually responsive dicationic block copolymer(Royal Society of Chemistry (RSC), 2012) Tuncer, Cansel; Bütün, Vural; Department of Chemistry; Erel-Göktepe, İrem; Karahan, Hüseyin Enis; Demirel, Adem Levent; PhD Student; Faculty Member; Department of Chemistry; College of Sciences; N/A; N/A; 6568We report the fabrication of hydrogen-bonded multilayers of micelles of a dually responsive, dicationic block copolymer, poly[2-(N-morpholino)ethyl methacrylate-block-2-(diisopropylamino)ethyl methacrylate] (PMEMA-b-PDPA). By taking advantage of the difference in the hydrophilicity of PMEMA and PDPA blocks, micelles with a PMEMA-corona and a PDPA-core were obtained above pH 6.5 and were assembled layer-by-layer at the surface with tannic acid (TA) at pH 7.4 through hydrogen bonding interactions between morpholino units of PMEMA and hydroxyl groups of TA. Destruction of PMEMA-b-PDPA micelles/TA films could be controlled at both acidic and basic conditions. At basic pH (pH = 8.75), multilayers disintegrated due to ionization of TA and disruption of hydrogen bonding interactions between layers of micelles and TA. At moderately acidic pH values, partially dissolved PMEMA-b-PDPA micelles and monomers underwent a restructuring with TA molecules and remained adsorbed at the surface. Complete dissolution of the multilayers occurred at around pH 3.6 due to further protonation of the tertiary amino groups on both blocks of PMEMA-b-PDPA, resulting in a charge imbalance between PMEMA-b-PDPA and TA layers followed by disintegration of the films. We have also encapsulated pyrene in the micellar cores and found that pyrene released from PMEMA-b-PDPA micelles/TA films increased 1.5- and 2.5-fold when the pH was decreased from 7.5 to 6 and 5, respectively. Such an increase in the amount of pyrene released was due to pH-controlled dissolution of the micellar cores. We have also found that at pH 7.5, increasing the temperature to 40 degrees C enhanced the release of pyrene by approximately 2-fold. Such an increase is due to lower critical solution temperature (LCST) behaviour of coronal PMEMA chains leading to temperature-induced conformational changes on the coronal chains, facilitating the release of pyrene through the coronal chains into the solution. Hydrogen bonded multilayers of micelles of a dicationic block copolymer are interesting due to the response of both multilayers and micellar cores at different pH paving the way for multiple pH-controlled delivery of functional molecules from surfaces.Publication Open Access Locked and loaded: ?-galactosidase activated photodynamic therapy agent enables selective imaging and targeted treatment of glioblastoma multiforme cancer cells(American Chemical Society (ACS), 2022) Elmazoğlu, Z.; Atakan, G.; Kepil, D.; Aykent, G.; Günbaş, G.; Department of Chemistry; Kölemen, Safacan; Almammadov, Toghrul; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); College of Sciences; 272051; N/ASelective detection and effective therapy of brain cancer, specifically, the very aggressive glioblastoma multiforme (GBM), remains one of the paramount challenges in clinical settings. While radiotherapy combined surgery is proposed as the main treatment course, it has several drawbacks such as complexity of the operation and common development of recurrent tumors in this course of patient care. Unique opportunities presented by photodynamic therapy (PDT) offer promising, effective, and precise therapy against GBM cells along with simultaneous imaging opportunities. However, activatable, theranostic molecular systems in PDT modality for GBM remained scarce. Specifically, even though elevated fi-galactosidase (fi-gal) activity in glioblastoma cells is well-documented, targeted, activatable therapeutic PDT agents have not been realized. Herein, we report a fi-galactosidase (fi-gal) activatable phototheranostic agent based on an iodinated resorufin core (RB-1) which was realized in only three steps with commercial reagents in 29% overall yield. RB-1 showed very high singlet oxygen (1O2) quantum yield (54%) accompanied by a remarkable turn-on response in fluorescence upon enzymatic activation. RB-1 was tested in different cell lines and revealed selective photocytotoxicity in U-87MG glioblastoma cells. Additionally, thanks to almost 7% fluorescence quantum yield (phi F) despite extremely high 1O2 generation yield, RB-1 was also demonstrated as a successful agent for fluorescence imaging of U-87MG cells. Due to significantly lower (fi-gal) activity in healthy cells (NIH/3T3), RB-1 stayed in a passive state and showed minimal photo and dark toxicity. RB-1 marks the first example of a fi- gal activatable phototheranostic agent toward effective treatment of glioblastoma.Publication Open Access Bosonic helium droplets with cationic impurities: onset of electrostriction and snowball effects from quantum calculations(American Institute of Physics (AIP) Publishing, 2007) Coccia, E.; Bodo, E.; Marinetti, F.; Gianturco, F. A.; Yıldırım, E.; Yurtsever, M.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Variational Monte Carlo and diffusion Monte Carlo calculations have been carried out for cations such as Li(+), Na(+), and K(+) as dopants of small helium clusters over a range of cluster sizes up to about 12 solvent atoms. The interaction has been modeled through a sum-of-potential picture that disregards higher order effects beyond atom-atom and atom-ion contributions. The latter were obtained from highly correlated ab initio calculations over a broad range of interatomic distances. This study focuses on two of the most striking features of the microsolvation in a quantum solvent of a cationic dopant: electrostriction and snowball effects. They are discussed here in detail and in relation with the nanoscopic properties of the interaction forces at play within a fully quantum picture of the cluster features.Publication Open Access RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells(Dove Medical Press, 2012) N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Nazlı, Caner; Ergenç, Tuğba İpek; Yar, Yasemin; Acar, Havva Funda Yağcı; Kızılel, Seda; PhD Student; Undergraduate Student; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 178902; 28376The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy.Publication Open Access Balanced intersystem crossing in iodinated silicon-fluoresceins allows new class of red shifted theranostic agents(American Chemical Society (ACS), 2021) Elmazoğlu, Zübeyir; Karaman, Osman; Günbaş, Görkem; Department of Chemistry; Çetin, Sultan; Kölemen, Safacan; Gündüz, Hande; PhD Student; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; 272051; N/AIodination of the silicon-fluorescein core revealed a new class of highly cytotoxic, red-shifted and water-soluble photosensitizer (SF-I) which is also fairly emissive to serve as a theranostic agent. Singlet oxygen generation capacity of SF-I was evaluated chemically, and up to 45% singlet oxygen quantum yield was reported in aqueous solutions. SF-I was further tested in triple negative breast (MDA MB-231) and colon (HCT-116) cancer cell lines, which are known to have limited chemotherapy options as well as very poor prognosis. SF-I induced efficient singlet oxygen generation and consequent photocytotoxicity in both cell lines upon light irradiation with a negligible dark toxicity while allowing cell imaging at the same time. SF-I marks the first ever example of a silicon xanthene-based photosensitizer and holds a lot of promise as a small-molecule-based theranostic scaffold.Publication Open Access Ultrasonically-assisted synthesis of CeO(2) within WS(2) interlayers forming type II heterojunction for a VOC photocatalytic oxidation(Elsevier, 2023) Hassandoost, R.; Yousef Tizhoosh, N.; Esmat, M.; Guselnikova, O.; Hussein N Assadi, M.; Khataee, A.; Department of Chemistry; Doustkhah, Esmail; Researcher; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of SciencesHere, we investigate the band structure, density of states, photocatalytic activity, and heterojunction mechanism of WS2 with CeO2 (CeO2@WS2) as a photoactive heterostructure. In this heterostructure, CeO2's growth within WS2 layers is achieved through ultrasonicating WS2 and intercalating CeO2's precursor within the WS2 interlayers, followed by hydrothermal treatment. Through a set of density functional calculations, we demonstrate that CeO2 and WS2 form an interface through a covalent bonding that can be highly stable. The electrochemical impedance spectroscopy (EIS) found that the CeO2@WS2 heterostructure exhibits a remarkably higher conductivity (22.23 mS cm(-2)) compared to either WS2 and CeO2, assignable to the interface in CeO2@WS2. Furthermore, in a physically mixed CeO2-WS2 where the interaction between particles is noncovalent, the resistance was significantly higher (0.67 mS cm(-2)), confirming that the heterostructure in the interface is covalently bonded. In addition, Mott-Schottky and the bandgap measurements through Tauc plots demonstrate that the heterojunction in CeO2 and WS2 is type II. Eventually, the CeO2@WS2 heterostructure indicated 446.7 mu mol g(-1) CO2 generation from photocatalytic oxidation of a volatile organic compound (VOC), formic acid, compared to WS2 and CeO2 alone.Publication Open Access Stability trends in ono-metallic 3d layered double hydroxides(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Mohammadi, Saeedeh; Esmailpour, Ayoub; Assadi, Mohammad Hussein Naseef; Department of Chemistry; Doustkhah, Esmail; Teaching Faculty; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); School of SciencesLayered double hydroxides (LDHs) constitute a unique group of 2D materials that can deliver exceptional catalytic, optical, and electronic performance. However, they usually suffer from low stability compared to their oxide counterparts. Using density functional calculations, we quantitatively demonstrate the crucial impact of the intercalants (i.e., water, lactate, and carbonate) on the stability of a series of common LDHs based on Mn, Fe, and Co. We found that intercalation with the singly charged lactate results in higher stability in all these LDH compounds, compared to neutral water and doubly charged carbonate. Furthermore, we show that the dispersion effect aids the stability of these LDH compounds. This investigation reveals that certain intercalants enhance LDH stability and alter the bandgap favourably.