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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Photocatalytic performance of disordered titanium-based hollow nanosheet metal-organic frameworks in wastewater treatment(Elsevier, 2024) Hassandoost, Ramin; Khataee, Alireza; Department of Chemistry; Doustkhah, Esmail; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of SciencesBackground: The low long-range order in the crystallinity of metal-organic frameworks (MOFs), commonly known as disordered MOFs, can lead to critical property variations. However, controlling the synthesis conditions for a reproducible outcome is somehow cumbersome, especially if this control is accompanied by morphology engineering to be utilized in photocatalysis where band structure, band gap, surface area, and porosity matter. Methods: Here, we report a crystal and structure-directing approach for the morphology engineering of NTU-9-like MOF aggregated particles (Ti-DHTA(AP)) (composed of Ti4+ and 2,5-dihydroxyterephthalic acid (DHTA)) into a hollow nanosheet (Ti-DHTA(HNS)) morphology. Triethylamine (TEA), here, acts as a structure-directing agent (SDA), and monodispersed polystyrene (PS) as a hard template. The three obtained Ti-DHTAs were eventually investigated in the photocatalytic removal of organic contaminants (dye and pharmaceuticals) and comprehensively characterized by (photo)electrochemical approaches. Significant Findings: The hollow nanosheet-architected Ti-DHTA(HNS) with a superior photocatalytic activity than the other morphologies also exhibits an overall photocatalytic removal (synergic adsorption-photodegradation) of similar to 6.5-fold higher than the commercial TiO2 (P25) under the visible light irradiation, with a degradation turnover (dTON) of 27 mmol h(-1) g(cat)(-1). Ti-DHTA(HNS) also shows promising results in the photocatalytic removal of dye and pharmaceutical wastewater. Photoelectrocatalytic characterizations were provided to compare the photocatalytic performance of synthesized Ti-DHTAs (e.g., in cyclic chronoamperometry (CA), 6-fold higher photoresponse than Ti-DHTA(AP)). Nyquist plots further exhibit that the charge transfer resistance (R-ct) of the unmodified Ti-DHTA(AP) is similar to 10-fold higher than Ti-DHTA(HNS) under visible light illumination. Furthermore, the actual water samples and the reusability of Ti-DHTA(HNS) were investigated. The addition of the radical scavenger agent can confirm the presence of varoius active radicals during the degradation, and hence, the formation of hydroxyl radicals was probed by adding o-phenylenediamine as a trapping agent. During methylene blue (MB) photodegradation, the LC-MS analysis exhibits acetoacetic acid formation (m/z = 102.03) as the dominant intermediate.Publication Metadata only Collision-induced state-changing rate coefficients for cyanogen backbones NCN 3Σ− and CNN 3Σ− in astrophysical environments(Royal Society of Chemistry, 2023) González-Sánchez, Lola; de la Fuente, Jorge Alonso; Sanz-Sanz, Cristina; Wester, Roland; Gianturco, Francesco A.; Department of Chemistry; Department of Chemistry; College of SciencesWe report quantum calculations involving the dynamics of rotational energy-transfer processes, by collision with He atoms in interstellar environments, of the title molecular species which share the presence of the CN backbone and are considered of importance in those environments. The latter structural feature is taken to be especially relevant for prebiotic chemistry and for its possible role in the processing of the heterocyclic rings of RNA and DNA nucleobases in the interstellar space. We carry out ab initio calculations of their interaction potentials with He atoms and further obtain the state-to-state rotationally inelastic cross sections and rate coefficients over the relevant range of temperatures. The similarities and differences between such species and other similar partners which have been already detected are analyzed and discussed for their significance on internal state populations in interstellar space for the two title molecular radicals.Publication Metadata only Rotational state-changes in C5N− by collisions with He and H2(Oxford University Press, 2023) Biswas,R.; Giri,K.; González-Sánchez,L.; Gianturco,F.A.; Lourderaj,U.; Sathyamurthy,N.; Veselinova,A.; Wester,R.; Department of Chemistry; Department of Chemistry; College of SciencesThe anion C5N− is one of the largest linear (C, N)-bearing chains detected in the interstellar medium. Here we present and discuss the general features of new ab initio potential energy surfaces describing the interaction of this linear anion with He and H2. We employ a Legendre Polynomials expansion representation for the former and an artificial neural network fit for the latter. We then carry out quantum scattering calculations to yield rotationally inelastic cross-sections for collisions with He and H2, using relative translational energy values in the range of 0.1-300 cm−1. We then obtained the corresponding inelastic rate coefficients as a function of temperature covering the range from 1 to 100 K. The results for these two systems are compared with each other, as well as with the earlier results on the C3N− colliding with the same partners. We found that the final inelastic rate coefficients for this anion are all fairly large, those from collisions with H2 being the largest. The consequences of such findings on their non-equilibrium rotational populations in interstellar environments are discussed in our conclusions.Publication Metadata only Solar-light-driven photocatalytic hydrogen evolution activity of gCN/WS2 heterojunctions incorporated with the first-row transition metals(Elsevier Science Sa, 2023) Acar, Eminegul Genc; Aslan, Emre; Patir, Imren Hatay; Department of Chemistry; Yılmaz, Seda; Eroğlu, Zafer; Metin, Önder; 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 SciencesThe design of semiconductor-based heterojunctions is an effective strategy to build highly active photo-catalyst systems. In this study, tungsten disulfide (WS2) modified graphitic carbon nitride (gCN) hetero-junction (gCN/WS2) is incorporated with Co and Ni (gCN/WS2-Co and gCN/WS2-Ni) to enhance the photocatalytic hydrogen evolution reaction (HER) activity of gCN/WS2 via performing a chemical reduction method and characterized by advanced analytical techniques. The photocatalytic HER activities of gCN, gCN/ WS2, gCN/WS2-Ni and gCN/WS2-Co were measured as 0.126, 0.221, 0.237 and 0.249 mmol g-1h-1, respec-tively, under the visible light irradiation. The improvement of photocatalytic activity and stability of gCN/ WS2-Ni and gCN/WS2-Co nanocomposites could be attributed to the 2D/2D heterojunction structure, ex-tended light harvesting ability, increased electron-hole lifetime and decreased recombination rate of the charge carriers. Moreover, mechanistic studies revealed that a S-scheme heterojunction is attributed to the enhanced photocatalytic HER by the gCN/WS2-Ni and gCN/WS2-Co photocatalysts, which provides pro-moted efficiency by photocarrier transfer and separation.Publication Metadata only Meso-2,3-dimercaptosuccinic acid-based macromers for ph-sensitive degradable hydrogelsa(Amer Chemical Soc, 2023) Guven, Melek Naz; Demirci, Gozde; Avci, Duygu; Department of Chemistry; Acar, Havva Funda Yağcı; Department of Chemistry; College of SciencesOne way of tailoring the properties of hydrogels is using functional cross-linkers. In this study, four highly watersoluble and degradable carboxylated diacrylate and diacrylamide macromeric cross-linkers were designed as precursors to prepare pH-sensitive and degradable hydrogels. The macromers were synthesized from thiol-Michael addition reaction of meso-2,3dimercaptosuccinic acid (DMSA) with poly(ethylene glycol) diacrylate (PEGDA, M-n = 575 g/mol) or N,N '-methylene bis(acrylamide) (MBA) in the presence of triethyl amine or sodium hydroxide. They were used as cross-linkers in fabrication of 2-hydroxyethyl methacrylate (HEMA)-based hydrogels, whose swelling strongly depended on pH, macromer structure, and hydrogel composition. The degradabilities of the hydrogels were greatly enhanced by increasing the concentration of the cross-linkers. The mechanical properties of the hydrogels can be tuned by tailoring the cross-linking macromer. The hydrogels were proven to have metal chelating ability in the context of Fe3+ ions, and upon this chelation, Young's modulus was also observed to increase significantly. In vitro cytotoxicity evaluations against U-2 OS human bone osteosarcoma epithelial cells and C2C12 mouse myoblast cells showed that the PEGDA functional macromers are not toxic.Publication Metadata only Disulfonated polyarylene ether sulfone membrane for graphitic carbon nitride/zinc oxide based photo-supercapacitors(Pergamon-Elsevier Science Ltd, 2023) Altaf, Cigdem Tuc; Colak, Tuluhan Olcayto; Erdem, Emre; Misirlioglu, Feray Bakan; Condorelli, Guglielmo Guido; Sankir, Nurdan Demirci; Sankir, Mehmet; Department of Chemistry; Ünal, Uğur; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of SciencesPhoto-supercapacitors (PSCs) are environmentally friendly devices that directly convert and store solar energy into electricity and have a high potential to eliminate the need for grid electricity for a sustainable future. In this study, lithiated (Li+) biphenol-based disulfonated poly (arylene ether sulfone) random copolymer (BPS) mem-brane has been successfully integrated into graphitic carbon nitride/zinc oxide nanowire composite-based PSC to increase the efficiency and to offer simpler and more cost-effective designs. It has been observed that after UV illumination specific capacitance (C-p) and energy density (E-d) increased 2.8 and 2.7-fold, respectively, indicating that the PSC with BPS-Li(+)performs approximately 3 times better under illumination than dark conditions. Furthermore, at elevated temperatures and 100% relative humidity C-p and E-d of the PSC increased to 23.61 Fg(-1) and 47.22 Whkg(-1) at 85 degrees C, respectively. This enhancement can be linked to the temperature-boosted ionic conductivity of the membrane.Publication Metadata only Bulk MgB2 superconductor for levitation applications fabricated with boron processed by different routes(Elsevier Science Sa, 2023) Savaskan, B.; Ozturk, U. K.; Guner, S. B.; Abdioglu, M.; Bahadir, M. V.; Acar, S.; Ionescu, A. M.; Locovei, C.; Enculescu, M.; Badica, P.; Department of Chemistry; Somer, Mehmet Suat; Department of Chemistry; College of SciencesBulk MgB2 discs were prepared by an in situ route from mixtures of magnesium and boron powders. The boron powders were produced by two methods. The first one consisted of a self-propagating high tem-perature magnesiothermic synthesis (SHS) process followed by acid and fluorine cleaning and a heat treatment in inert atmosphere. This approach produced boron with purities between 86 % and 97 %, where the main impurity was Mg. Depending on the final heat treatment, these boron powders were amorphous or crystalline. In the second route, high purity nano powders (99 %) of boron were obtained by a diborane pyrolysis process. Bulks of MgB2 were characterized by structural, microstructural, and magnetic mea-surements. Critical current density, pinning force aspects and levitation force (including guiding force) details were assessed. Amorphous lower purity boron (86-97 %) obtained by the first processing route was found to promote the largest levitation forces of the MgB2 bulks and, among these samples, the best le-vitation results were recorded when using boron with a purity of 95-97 %. Use of a lower purity boron that decreases the cost of MgB2 promotes large scale production at industrial level of bulk MgB2 super-conducting magnets for levitation applications and enhances the applicability potential of MgB2 super-conductor. The relationship between levitation force and specific features of the samples such as pinning force details are discussed.Publication Metadata only Optical imaging probes for selective detection of butyrylcholinesterase(Royal Soc Chemistry, 2024) Chan, Jefferson; Department of Chemistry; Dırak, Musa; Kölemen, Safacan; Department of Chemistry; Graduate School of Sciences and Engineering; College of SciencesButyrylcholinesterase (BChE), a member of the human serine hydrolase family, is an essential enzyme for cholinergic neurotransmission as it catalyzes the hydrolysis of acetylcholine. It also plays central roles in apoptosis, lipid metabolism, and xenobiotic detoxification. On the other side, abnormal levels of BChE are directly associated with the formation of pathogenic states such as neurodegenerative diseases, psychiatric and cardiovascular disorders, liver damage, diabetes, and cancer. Thus, selective and sensitive detection of BChE level in living organisms is highly crucial and is of great importance to further understand the roles of BChE in both physiological and pathological processes. However, it is a very complicated task due to the potential interference of acetylcholinesterase (AChE), the other human cholinesterase, as these two enzymes share a very similar substrate scope. To this end, optical imaging probes have attracted immense attention in recent years as they have modular structures, which can be tuned precisely to satisfy high selectivity toward BChE, and at the same time they offer real time and nondestructive imaging opportunities with a high spatial and temporal resolution. Here, we summarize BChE selective imaging probes by discussing the critical milestones achieved during the development process of these molecular sensors over the years. We put a special emphasis on design principles and biological applications of highly promising new generation activity-based probes. We also give a comprehensive outlook for the future of BChE-responsive probes and highlight the ongoing challenges. This collection marks the first review article on BChE-responsive imaging agents. Butyrylcholinesterase (BChE) is a human serine hydrolase, which plays critical roles in various physiological and pathological states. Here, we summarized the optical probes that can selectively monitor the BChE activity in different biological models.Publication Metadata only Bismuthene nanosheets as a photodynamic and photothermal antibacterial agent under NIR light illumination(Elsevier Inc., 2024) Cekceoglu, Ilknur Aksoy; Patir, Imren Hatay; Department of Chemistry; Eroğlu, Zafer; Kubanaliev, Temirlan; Metin, Önder; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and EngineeringBacterial infections remain a significant public health burden due to the emergence of antibiotic resistance and their non-specific cytotoxic effects, leading to the search for novel antibacterial agents. Two-dimensional (2D) pnictogens, which stand out with their advantegeous properties such as large surface areas, compatibility with biological systems, and permeability across biological membranes, have emerged as potential materials in the fight against bacterial infections. By considering all these advantages, here for the first time, the antibacterial activity of 2D bismuth (Bismuthene, Biene) on Gram-negative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), Gram-positive Staphylococcus aureus (S. aureus) and Methicillin-Resistant Staphylococcus aureus (MRSA) were examined under NIR light illumination. A growth curve analysis was conducted with a concentration of 256 mu g*mL-1 of exfoliated Biene nanosheets to assess the inhibition effect and corresponding antibacterial effect (%) against each bacterial strain. The photodynamic theraphy (PDT) and photothermal therapy (PTT)-mediated antibacterial mechanisms were explored by analyzing the generation of reactive oxygen species (ROS) via Glutathione (GSH) oxidation assay while a photothermal camera monitored temperature dynamic changes during irradiation. The high specific surface area-dependent membrane damage ability of Biene and morphological changes of the bacteria were visualized by field emission scanning electron microscope (FESEM). The exciting growth inhibition activity of Biene nanosheets for all bacterial strains was increased during irradiation, and breathtakingly the inhibition rate reached up to >= 99.1 % for P. aeruginosa, S. aureus, and MRSA. Besides, S. aureus and MRSA are more susceptible to Biene than E. coli and P. aeruginosa.Publication Metadata only In-situ surface enhanced Raman spectroscopy investigations on surface transformations of oxide derived copper electrodes during CO2RR(Academic Press Inc Elsevier Science, 2023) Department of Chemistry; Tafazoli, Saeede; Yusufoğlu, Muhammed; Balkan, Timuçin; Kaya, Sarp; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of SciencesWe investigated the catalytic activity and C2 selectivity in electrochemical carbon dioxide reduction reac-tion (CO2RR) on two distinguished electrodeposited Cu oxides with distinct morphologies and structures. The electrode with a compact structure exhibited two times higher faradaic efficiencies of C2 products (40%). Through utilizing electrochemical surface-enhanced Raman spectroscopy (SERS), it was realized that the formation of a metastable phase (malachite) on electrode surfaces by consumption of HCO3- could cause a shift in local pH. The analysis of SERS indicated a strong correlation between the presence of the malachite phase and strongly-adsorbed CO on electrode surfaces, preventing dimerization and fur-ther reduction. This malachite phase terminating the surface can hinder the charge exchange and inter-fere with further reductions in C2 products.