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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Open Access
A high-performance metal-free hydrogen-evolution reaction electrocatalyst from bacterium derived carbon
(Royal Society of Chemistry (RSC), 2015) Wei, Li; Karahan, Hüseyin Enis; Goh, Kunli; Jiang, Wenchao; Yu, Dingshan; Jiang, Rongrong; Chen, Yuan; Department of Chemistry; Birer, Özgür; Researcher; Department of Chemistry; College of Sciences
We report a sustainable approach to obtain carbon materials with nitrogen and phosphorus dual functionalities from a common bacterium strain (S. aureus) as a highly efficient hydrogen-evolution reaction (HER) catalyst. With mesoporous structure introduced by ZnCl2 salt and cathodic activation, it demonstrates an onset overpotential as low as 76 mV, a Tafel slope of 58.4 mV dec(-1) and a large normalized exchange current density of 1.72 x 10(-2) mA cm(-2), which are comparable to those of hitherto best metal-free and well-fabricated metallic HER catalysts
Open Access
A near-infrared benzothiazole-based chemodosimeter for rapid and selective detection of hydrogen sulfide
(Turkish Chemical Society / Türkiye Kimya Derneği, 2021) Department of Chemistry; Kölemen, Safacan; Faculty Member; 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
Hydrogen sulfide (H2S) is a biologically relevant gaseous molecule, which involves in a wide variety of physiological and pathological processes. Thus, detection of H2S is highly valuable in order to clarify its complex roles. In this study, a new benzothiazole-based donor-acceptor type H 2S selective chemodosimeter (HP-1) was synthesized and its H2S detection capabilities were investigated in aqueous solutions. HP-1 exhibited a red-shifted absorption signal at 530 nm and a near-infrared (NIR) fluorescence peak at 680 nm as a result of enhanced intramolecular charge transfer (ICT) in the presence of H2S, which enabled a selective and very rapid ratiometric fluorescent detection. HP-1 was also showed to be highly sensitive toward H2S with a very low limit of detection value.
Open Access
A new class of porous materials for efficient CO2 separation: ionic liquid/graphene aerogel composites
(Elsevier, 2021) Department of Chemical and Biological Engineering; N/A; Department of Chemistry; Zeeshan, Muhammad; Yalçın, Kaan; Keskin, Seda; Uzun, Alper; Öztuna, Feriha Eylül Saraç; Ünal, Uğur; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; 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 Engineering; College of Sciences; N/A; N/A; 40548; 59917; N/A; 42079
Here, we report a new post-synthesis modification strategy for functionalizing reduced graphene aerogels (rGAs) towards an exceptional CO2 separation performance. 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was impregnated on a rGA, prepared by reducing GA at 700 degrees C, at various ionic liquid (IL) loadings of 5, 10, 30, and 50 wt%. The resulting composites were characterized in deep detail by X-ray photoelectron spectroscopy, X-ray diffraction, N-2 physical adsorption measurements, scanning electron microscopy, Fourier transform infrared and Raman spectroscopies, and thermogravimetric analysis. Results indicated the presence of interactions between the rGA surface and the anion of the IL, potentially improving the CO2 affinity. Volumetric gas adsorption measurements using these materials showed that the deposition of [BMIM][PF6] on rGA surface at an IL loading of 50 wt% boosts the CO2/CH4 selectivity by more than 20-times, exceeding an absolute value of 120, a remarkably higher CO2/CH4 selectivity compared to that of other functionalized materials under similar operating conditions. Tunability of both the IL structure and the surface characteristics of rGA offer a tremendous degree of flexibility for the rational design of these IL/rGA composites towards high performance in gas separation applications.
Open Access
A new type of microphotoreactor with integrated optofluidic waveguide based on solid-air nanoporous aerogels
(Royal Society of Chemistry (RSC), 2018) Jonas, Alexandr; Department of Chemistry; Department of Electrical and Electronics Engineering; Department of Physics; Özbakır, Yaprak; Erkey, Can; Kiraz, Alper; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; Department of Electrical and Electronics Engineering; Department of Physics; College of Engineering; College of Sciences; N/A; 29633; 22542
In this study, we developed a new type of microphotoreactor based on an optofluidic waveguide with aqueous liquid core fabricated inside a nanoporous aerogel. To this end, we synthesized a hydrophobic silica aerogel monolith with a density of 0.22 g cm(-3) and a low refractive index of 1.06 that-from the optical point of view-effectively behaves like solid air. Subsequently, we drilled an L-shaped channel within the monolith that confined both the aqueous core liquid and the guided light, the latter property arising due to total internal reflection of light from the liquid-aerogel interface. We characterized the efficiency of light guiding in liquid-filled channel and-using the light delivered by waveguiding-we carried out photochemical reactions in the channel filled with aqueous solutions of methylene blue dye. We demonstrated that methylene blue could be efficiently degraded in the optofluidic photoreactor, with conversion increasing with increasing power of the incident light. The presented optofluidic microphotoreactor represents a versatile platform employing light guiding concept of conventional optical fibres for performing photochemical reactions.
Open Access
A young male patient presented with dyspnea, cough, and lilateral pulmonary infiltrations: what is your siagnosis?
(Aves, 2016) Department of Chemistry; İliaz, Sinem; Yurtsever, İsmail Ersin; Çağlayan, Benan Niku; Doctor; Department of Chemistry; College of Sciences; Koç University Hospital; 168584; 7129; N/A
Open Access
Ab initio quantum dynamics with very weak van der Waals interactions: structure and stability of small Li-2((1)Sigma(+)(g))-(He)(n) clusters
(American Institute of Physics (AIP) Publishing, 2004) Bodo, E.; Sebastianelli, F.; Gianturco, F.A.; Yurtsever, M.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129
The potential energy surface (PES) for the interaction between Li-2((1)Sigma(g)(+)) and He-4 has been computed using an accurate, post-Hartree-Fock quantum calculation for its ground electronic state. The orientational anisotropy of the forces and the interplay between repulsive and attractive effects within the PES are analyzed to extract information on the possible existence of bound states in the triatomic system. The structures of a few of the Li-2(He)(n) small clusters are examined by comparing a classical approach with a full quantum one to generate bound configurations and to extract information on the possible spatial arrangements of the smaller clusters via a vis the location of the Li-2 dopant. Some significant consequences on the Li-2 behavior in larger clusters and droplets are drawn from the above findings.
Open Access
Acetic acid conversion to ketene on Cu2O(1 0 0): reaction mechanism deduced from experimental observations and theoretical computations
(Elsevier, 2021) Tissot, H.; Halldin Stenlid, J.; Wang, C.; Brinck, T.; Sassa, Y.; Johansson, F. O. L.; Weissenrieder, J.; Department of Chemistry; N/A; Kaya, Sarp; Panahi, Mohammad; Faculty Member; PhD Student; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Sciences; Graduate School of Sciences and Engineering; 116541; N/A
Ketene, a versatile reagent in production of fine and specialty chemicals, is produced from acetic acid. We investigate the synthesis of ketene from acetic acid over the (3,0;1,1) surface of Cu2O(1 0 0) through analysis of the adsorption and desorption characteristics of formic and acetic acids. The results allow us to establish a reaction mechanism for ketene formation. Observations from x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy, and temperature programmed desorption (TPD), supported by a comparison with formic acid results, suggest that acetic acid reacts with Cu2O through deprotonation to form acetate species coordinated to copper sites and hydroxylation of nearby surface oxygen sites. For formic acid the decomposition of adsorbed formate species results in desorption of CO2 and CO while, for acetic acid, high yields of ketene are observed at temperature >500 K. Modeling by density functional theory (DFT) confirms the strong interaction of acetic acid with the (3,0;1,1) surface and the spontaneous dissociation into adsorbed acetate and hydrogen atom species, the latter forming an OH-group. In an identified reaction intermediate ketene binds via all C and O atoms to Cu surface sites, in agreement with interpretations from XPS. In the vicinity of the adsorbate the surface experiences a local reorganization into a c(2 × 2) reconstruction. The total computed energy barrier for ketene formation is 1.81 eV in good agreement with the 1.74 eV obtained from TPD analysis. Our experimental observations and mechanistic DFT studies suggests that Cu2O can operate as an efficient catalyst for the green generation of ketene from acetic acid.
Open Access
Activity-based photosensitizers with optimized triplet state characteristics toward cancer cell selective and image guided photodynamic therapy
(American Chemical Society (ACS), 2022) Elmazoğlu, Zübeyir; Kepil, Dilay; Etienne, Thibaud; Marion, Antoine; Günbaş, Görkem; Department of Chemistry; Kılıç, Eda; Almammadov, Toghrul; Kölemen, Safacan; Researcher; Faculty Member; 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); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 272051
Activity-based theranostic photosensitizers are highly attractive in photodynarnic therapy as they offer enhanced therapeutic outcome on cancer cells with an imaging opportunity at the same time. However, photosensitizers (PS) cores that can be easily converted to activity-based photosensitizers (aPSs) are still quite limited in the literature. In this study, we modified the dicyanomethylene-4H-chromene (DCM) core with a heavy iodine atom to get two different PSs (DCMo-I, I-DCMo-Cl) that can be further converted to aPS after simple modifications. The effect of iodine positioning on singlet oxygen generation capacity was also evaluated through computational studies. DCMo-I showed better performance in solution experiments and further proved to be a promising phototheranostic scaffold via cell culture studies. Later, a cysteine (Cys) activatable PS based on the DCMo-I core (DCMo-I-Cys) was developed, which induced selective photocytotoxicity along with a fluorescence turn-on response in Cys rich cancer cells.
Open Access
Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy
(American Institute of Physics (AIP) Publishing, 2016) Erdem, Emre; Repp, Sergej; Weber, Stefan; N/A; Department of Chemistry; Bateni, Ali; Somer, Mehmet Suat; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178882
Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites. Published by AIP Publishing.
Open Access
An in vitro study on the cytotoxicity and genotoxicity of silver sulfide quantum dots coated with meso-2,3-dimercaptosuccinic acid
(Galenos Yayınevi, 2019) N/A; Department of Chemistry; Gözüaçık, Devrim; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences
Objectives: Silver sulfide (Ag2S) quantum dots (QDs) are highly promising nanomaterials in bioimaging systems due to their high activities for both imaging and drug/gene delivery. There is insufficient research on the toxicity of Ag2S QDs coated with meso-2,3-dimercaptosuccinic acid (DMSA). In this study, we aimed to determine the cytotoxicity of Ag2S QDs coated with DMSA in Chinese hamster lung fibroblast (V79) cells over a wide range of concentrations (5-2000 mu g/mL). Materials and methods: cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and neutral red uptake (NRU) assays. The genotoxic and apoptotic effects of DMSA/Ag2S QDs were also assessed by comet assay and real-time polymerase chain reaction technique, respectively. Results: cell viability was 54.0 +/- 4.8% and 65.7 +/- 4.1% at the highest dose (2000 mu g/mL) of Ag2S QDs using the MTT and NRU assays, respectively. Although cell viability decreased above 400 mu g/mL (MTT assay) and 800 mu g/mL (NRU assay), DNA damage was not induced by DMSA/Ag2S QDs at the studied concentrations. The mRNA expression levels of p53, caspase-3, cospose-9, Box, Bcl-2, and survivin genes were altered in the cells exposed to 500 and 1000 mu g/mL DMSA/Ag2S QDs. Conclusion: the cytotoxic effects of DMSA/Ag2S QDs may occur at high doses through the apoptotic pathways. However, DMSA/Ag2S QDs appear to be biocompatible at low doses, making them well suited for cell labeling applications. / Amaç: Gümüş sülfür (Ag2 S) kuantum noktaları (QD), hem görüntüleme hem de ilaç/gen hedefleme için büyük aktiviteleri nedeniyle biyo-görüntüleme sisteminde oldukça gelecek vaad eden nanomalzemelerdir. Mezo-2,3-dimerkaptosüksinik asit (DMSA) ile kaplanmış Ag2 S QD’lerin toksisitesi hakkında yeterli çalışma yoktur. Bu çalışmada Çin hamster akciğer fibroblast (V79) hücrelerinde DMSA ile kaplanmış Ag2 S QD’lerin geniş bir konsantrasyon aralığında (5-2000 µg/mL) sitotoksisitesini belirlemeyi amaçladık. Gereç ve yöntemler: hücre canlılığı 3-(4,5-dimetiltiyazol-2-il)-2,5-difeniltetrazolium bromid (MTT) ve nötral kırmız alım (NRU) deneyleri ile belirlendi. DMSA/Ag2 S QD’lerin genotoksik ve apoptotik etkileri sırasıyla komet analizi ve gerçek zamanlı polimeraz zincir reaksiyonu tekniği ile değerlendirildi. Bulgular: Ag2 S QD’lerin en yüksek dozlarında hücre canlılığı MTT ve NRU deneylerinde sırasıyla 54.0±4.8% ve 65.7±4.1% olarak bulundu. Ancak hücre canlılığı 400 µg/mL (MTT deneyi) ve 800 µg/mL (NRU deney) üzerinde azalmıştır. İncelenen konsantrasyonlarda DNA hasarının DMSA/Ag2 S QD’ler tarafından indüklenmediği belirlenmiştir. P53, kaspaz-3, kaspaz-9, Bax, Bcl-2 ve survivin genlerinin mRNA ekspresyon düzeyleri 500 ve 1000 µg/mL DMSA/Ag2 S QD’lere maruz kalan hücrelerde değişmiştir. Sonuç: DMSA/Ag2 S QD’lerin yüksek dozlarda sitotoksik etkilerinin apoptotik yollarla ortaya çıkabileceği görülmektedir. Bununla birlikte, DMSA/ Ag2 S QD’ler, düşük dozlarda biyolojik olarak uyumlu görünmektedir, bu da onları hücre görüntüleme uygulamaları için uygun kılmaktadır.
Open Access
An integrated computational-experimental hierarchical approach for the rational design of an IL/UiO-66 composite offering infinite CO2 selectivity
(Wiley, 2022) Department of Chemical and Biological Engineering; Department of Chemistry; Zeeshan, Muhammad; Gülbalkan, Hasan Can; Durak, Özce; Haşlak, Zeynep Pınar; Ünal, Uğur; Keskin, Seda; Uzun, Alper; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; 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); College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; 42079; 40548; 59917
Owing to the possibility of generating theoretically unlimited numbers of ionic liquid (IL)-metal-organic framework (MOF) combinations, experimental studies on IL/MOF composites for gas separation applications are mostly conducted on a trial-and-error basis. To address this problem, an integrated computational-experimental hierarchical approach is presented for selecting the best IL-MOF combination for a target gas separation application. For this purpose, UiO-66 and pyrrolidinium-based ILs are chosen as the parent MOF and IL family, respectively, and three powerful computational tools, Conductor-like Screening Model for Realistic Solvents calculations, density functional theory calculations, and grand canonical Monte Carlo simulations, are integrated to identify the most promising IL-UiO-66 combination as 1-n-butyl-1-methylpyrrolidinium dicyanamide/UiO-66, [BMPyrr][DCA]/UiO-66. Then, this composite is synthesized, characterized in deep detail, and tested for CO2/N-2, CO2/CH4, and CH4/N-2 separations. Results demonstrate that [BMPyrr][DCA]/UiO-66 offers an extraordinary gas separation performance, with practically infinite CO2 and CH4 selectivities over N-2 at 15 degrees C and at low pressures. The integrated hierarchical approach proposed in this work paves the way for the rational design and development of novel IL/MOF composites offering exceptional performance for any desired gas separation application.
Open Access
Angular-momentum-driven chaos in small clusters
(American Physical Society (APS), 1998) Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129
The effects of the rotational motion on the chaotic behavior of triatomic Lennard-Jones clusters are studied. A set of initial momentum distributions with tunable parameters is chosen to correspond to various rigid-body rotations around symmetry axes of the cluster. By smoothly varying the direction of the initial kicks given to the cluster, periodic transitions between regular and chaotic regimes are obtained. A study of initial conditions leading up to such transitions shows that the major factor that determines the extent of the chaotic behavior is the initial partitioning of the kinetic energy between the rotational and vibrational motion. From the analysis of the time evolution of various properties it is concluded that the basic role of this initial partitioning is to control the energy transfer between the kinetic and the potential energy.
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/A
Iodination 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.
Open Access
Blue TiO2 nanotube arrays as semimetallic materials with enhanced photoelectrochemical activity towards water splitting
(TÜBİTAK, 2020) Department of Chemistry; Peighambardoust, Naeimeh Sadat; Aydemir, Umut; Researcher; Faculty Member; Department of Chemistry; Koç University AKKİM Boron-Based Materials _ High-technology Chemicals Research _ Application Center (KABAM) / Koç Üniversitesi AKKİM Bor Tabanlı Malzemeler ve İleri Teknoloji Kimyasallar Uygulama ve Araştırma Merkezi (KABAM); College of Sciences; N/A; 58403
In the past years there has been a great interest in self-doped TiO2 nanotubes (blue TiO2 nanotubes) compared to undoped ones owing to their high carrier density and conductivity. In this study, blue TiO2 nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO2 nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO2 nanotubes. The annealing temperature of undoped TiO2 nanotubes was tuned before cathodic polarization, revealing that annealing at 500 degrees C improved the photoresponse of the nanotubes significantly. Further optimization of the blue TiO2 nanotubes was achieved by adjusting the cathodic polarization parameters. Blue TiO2 nanotubes obtained at the potential of -1.4 V (vs. SCE) with a duration of 10 min exhibited twice more photocurrent response (0.39 mA cm(-2)) compared to the undoped TiO(2 )nanotube arrays (0.19 mA cm(-2)). Oxygen vacancies formed through the cathodic polarization decreased charge recombination and enhanced charge transfer rate; therefore, a high photoelectrochemical activity under visible light irradiation could be achieved.
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; 7129
Variational 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.
Open Access
Broad spectrum antibacterial photodynamic and photothermal therapy achieved with indocyanine green loaded SPIONs under near infrared irradiation
(Royal Society of Chemistry (RSC), 2020) N/A; Department of Physics; Department of Chemistry; Bilici, Kübra; Ataç, Nazlı; Muti, Abdullah; Toker, Işınsu Baylam; Doğan, Özlem; Sennaroğlu, Alphan; Can, Füsun; Acar, Havva Funda Yağcı; Researcher; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; College of Sciences; N/A; N/A; N/A; N/A; 170418; 23851; 103165; 178902
Antimicrobial photodynamic therapy (aPDT) and antimicrobial photothermal therapy (aPTT) are promising local and effective alternative therapies for antibiotic resistant bacterial infections and biofilms. A combination of nanoparticles and organic photosensitizers offers a great opportunity to combine PDT and PTT for effective eradication of both planktonic bacteria and their biofilms. In this work, photo-induced antibacterial activity of indocyanine green (ICG), 3-aminopropylsilane coated superparamagnetic iron oxide nanoparticles (APTMS@SPIONs) and ICG loaded APTMS@SPIONs was evaluated on planktonic cells and biofilms of Gram-negative (E. coli,K. pneumoniae,P. aeruginosa) and Gram-positive (S. epidermis) bacteria. A relatively low dose of ICG (25 mu g mL(-1)) and SPIONs (0.425 mu g mL(-1)nanoparticle) in combination with single, short (10 min) laser irradiation at 808 nm with a power of 1150 mW was used in this study. No dark toxicity of the agents or antibacterial effect of the laser irradiation was observed. The charge of the particles did not provide a significant difference in their penetration to Gram-negativeversusGram-positive bacterial strains or their biofilms. APTMS@SPION/laser treatment completely eliminatedP. aeruginosaand provided 7-log reduction in the colony forming unit (CFU) ofE. Coli, but was not effective on the other two bacteria. This is the first example for antibacterial phototoxicity of this nanoparticle. ICG/laser and ICG-APTMS@SPION/laser treatments provided complete killing of all planktonic cells. Successful eradication of all biofilms was achieved with ICG/laser (3.2-3.7 log reduction in CFUs) or ICG-APTMS@SPION/laser treatment (3.3-4.4 log reduction in CFUs). However, an exceptionally high, 6.5-log reduction as well as a dramatic difference between ICGversusICG/APTMS@SPION treatment was observed inK. pneumoniaebiofilms with ICG-APTMS@SPION/laser treatment. Investigation of the ROS production and increase in the local temperature of the biofilms that were subjected to phototherapy suggested a combination of aPTT and aPDT mechanisms for phototoxicity, exhibiting a synergistic effect when ICG-APTMS@SPION/laser was used. This approach opens an exciting and novel avenue in the fight against drug resistant infections by successfully utilizing the antimicrobial and antibiofilm activity of low dose FDA approved optically traceable ICG and relatively low cost clinically acceptable iron oxide nanoparticles to enable effective aPDT/aPTT combination, inducedviashort-duration laser irradiation at a near-infrared wavelength.
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 Sciences
The 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.
Open Access
CdTe quantum dot sensitized hexaniobate nanoscrolls and their photoelectrochemical properties
(Royal Society of Chemistry (RSC), 2012) Department of Chemistry; Öztuna, Feriha Eylül Saraç; Akkaya, Ceren Yılmaz; Acar, Havva Funda Yağcı; Ünal, Uğur; PhD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; N/A; N/A; 178902; N/A
We have constructed hybrid quantum dot-layered niobate films with an electrophoretic deposition method. The structure and photoelectrochemical behaviour were demonstrated.
Open Access
Cetuximab-Ag2S quantum dots for fluorescence imaging and highly effective combination of ALA-based photodynamic/chemo-therapy of colorectal cancer cells
(Royal Society of Chemistry (RSC), 2021) Mohammad Hadi, Layla; Yaghini, Elnaz; Loizidou, Marilena; MacRobert, Alexander J.; Department of Chemistry; N/A; Department of Physics; Acar, Havva Funda Yağcı; Bayır, Ali; Hashemkhani, Mahshid; Demirci, Gözde; Muti, Abdullah; Sennaroğlu, Alphan; Researcher; PhD Student; Master Student; PhD Student; Faculty Member; Department of Chemistry; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering; 178902; N/A; N/A; N/A; N/A; 23851
Colorectal cancer (CRC) has a poor prognosis and urgently needs better therapeutic approaches. 5-Aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) based photodynamic therapy (PDT) is already used in the clinic for several cancers but not yet well investigated for CRC. Currently, systemic administration of ALA offers a limited degree of tumour selectivity, except for intracranial tumours, limiting its wider use in the clinic. The combination of effective ALA-PDT and chemotherapy may provide a promising alternative approach for CRC treatment. Herein, theranostic Ag2S quantum dots (AS-2MPA) optically trackable in near-infrared (NIR), conjugated with endothelial growth factor receptor (EGFR) targeting Cetuximab (Cet) and loaded with ALA for PDT monotherapy or ALA/5-fluorouracil (5FU) for the combination therapy are proposed for enhanced treatment of EGFR(+) CRC. AS-2MPA-Cet exhibited excellent targeting of the high EGFR expressing cells and showed a strong intracellular signal for NIR optical detection in a comparative study performed on SW480, HCT116, and HT29 cells, which exhibit high, medium and low EGFR expression, respectively. Targeting provided enhanced uptake of the ALA loaded nanoparticles by strong EGFR expressing cells and formation of higher levels of PpIX. Cells also differ in their efficiency to convert ALA to PpIX, and SW480 was the best, followed by HT29, while HCT116 was determined as unsuitable for ALA-PDT. The therapeutic efficacy was evaluated in 2D cell cultures and 3D spheroids of SW480 and HT29 cells using AS-2MPA with either electrostatically loaded, hydrazone or amide linked ALA to achieve different levels of pH or enzyme sensitive release. Most effective phototoxicity was observed in SW480 cells using AS-2MPA-ALA-electrostatic-Cet due to enhanced uptake of the particles, fast ALA release and effective ALA-to-PpIX conversion. Targeted delivery reduced the effective ALA concentration significantly which was further reduced with codelivery of 5FU. Delivery of ALA via covalent linkages was also effective for PDT, but required a longer incubation time for the release of ALA in therapeutic doses. Phototoxicity was correlated with high levels of reactive oxygen species (ROS) and apoptotic/necrotic cell death. Hence, both AS-2MPA-ALA-Cet based PDT and AS-2MPA-ALA-Cet-5FU based chemo/PDT combination therapy coupled with strong NIR tracking of the nanoparticles demonstrate an exceptional therapeutic effect on CRC cells and excellent potential for synergistic multistage tumour targeting therapy.
Open Access
Chaotic behavior of triatomic clusters
(American Physical Society (APS), 1997) Elmacı, N.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129
The dynamics of triatomic clusters is investigated employing two-body Lennard-Jones and three-body Axilrod-Teller potential functions. Lyapunov exponents are calculated for the total energy range of -2.70 epsilon <E< -0.72 epsilon. The effects of the initial geometry of the cluster, its angular momentum, and the magnitude of three-body interactions are analyzed. It has been found that the dominating factor for the extent of chaotic behavior is the energy assigned to vibrational modes. The introduction of the rotational motion regularizes the dynamics in spite of a higher degree of nonlinearity. The three-body terms in the potential function affect the extent of the chaos in different manners depending on the initial geometry of the cluster. Finally, the time evolution of heterogeneous clusters generated by varying the size, mass, and the interaction strength of a single atom is observed. Their Lyapunov exponent spectra show that the additional nonlinearity reduces the chaotic behavior of the system in most of the cases.