Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
Browse
32 results
Filters
Settings
Search Results
Article Citation - Scopus: 1A Perspective on the State-Of Functionalized 2d Materials(American Institute of Physics, 2023) Duran, Tuna; Yayak, Yankı Öncü; Aydın, Hasan; Peeters, François M.; Yağmurcukardeş, MehmetTwo-dimensional (2D) ultra-thin materials are more crucial than their bulk counterparts for the covalent functionalization of their surface owing to atomic thinness, large surface-to-volume ratio, and high reactivity of surface atoms having unoccupied orbitals. Since the surface of a 2D material is composed of atoms having unoccupied orbitals, covalent functionalization enables one to improve or precisely modify the properties of the ultra-thin materials. Chemical functionalization of 2D materials not only modifies their intrinsic properties but also makes them adapted for nanotechnology applications. Such engineered materials have been used in many different applications with their improved properties. In the present Perspective, we begin with a brief history of functionalization followed by the introduction of functionalized 2D materials. Our Perspective is composed of the following sections: the applications areas of 2D graphene and graphene oxide crystals, transition metal dichalcogenides, and in-plane anisotropic black phosphorus, all of which have been widely used in different nanotechnology applications. Finally, our Perspectives on the future directions of applications of functionalized 2D materials are given. The present Perspective sheds light on the current progress in nanotechnological applications of engineered 2D materials through surface functionalization. © 2023 Author(s).Article Citation - WoS: 4Citation - Scopus: 4Identification of a Magnetic Phase Via a Raman Spectrum in Single-Layer Mnse: an Ab Initio Study(Elsevier, 2022) Yayak, Yankı Öncü; Şahin, Hasan; Yağmurcukardeş, MehmetMotivated by the recent experimental realization of single-layer two-dimensional MnSe [ACS Nano2021, 15, 13794-13802], structural, magnetic, elastic, vibrational, and electronic properties of single-layer MnSe are investigated by using density functional theory-based calculations. Among four different magnetic phases, namely, ferromagnetic (FM) and Nẽel-, zigzag-, and stripy-antiferromagnetic (AFM) phases, the Nẽel-AFM structure is found to be the energetically most favorable phase. Structural optimizations show the formation of in-plane anisotropy within the structures of zigzag- and stripy-AFM phases in single-layer MnSe. For the dynamically stable four magnetic phases, predicted Raman spectra reveal that each phase exhibits distinctive vibrational features and can be distinguished from each other. In addition, the elastic constants indicate the mechanical stability of each magnetic phase in single-layer MnSe and reveal the soft nature of each phase. Moreover, electronic band dispersion calculations show the indirect band gap semiconducting nature with varying electronic band gap energies for all magnetic phases. Furthermore, the atomic orbital-based density of states reveals the existence of out-of-plane orbitals dominating the top valence states in zigzag- and stripy-AFM phases, giving rise to the localized states. The stability of different magnetic phases and their distinct vibrational and electronic properties make single-layer MnSe a promising candidate for nanoelectronic and spintronic applications.Article Citation - WoS: 2Citation - Scopus: 31-Octanol Is a Functional Impurity Modifying Particle Size and Photophysical Properties of Colloidal Zncdsse/Zns Nanocrystals(American Chemical Society, 2021) Sevim Ünlütürk, Seçil; Çağır, Ali; Varlıklı, Canan; Özçelik, SerdarImpurities in trioctylphophine (TOP) strongly affect nanocrystal synthesis. 1-Octanol among other contaminants in TOP is identified for the first time as a functional impurity by H-1 NMR. The deliberate addition of 1-octanol into trioctylphosphine reduced particle size and modified photophysical properties of ZnCdSSe/ZnS colloidal nanocrystals. NMR analysis furthermore revealed that 1-octanol is bonded to the nanocrystal surfaces. The ratio of integrals for the O-CH2 protons of 1-octanol, which is the lowest compared to the other ligands, suggests that 1-octanol plays a critical role to tune the particle size of nanocrystals. The increased amount of 1-octanol added into TOP reduces the particle size from 9.8 to 7.2 nm, causing a progressive blue shift in the UV-vis and PL spectra but leaving the alloy composition unaffected. The rate of nonradiative processes is enhanced with the amount of 1-octanol added into TOP, correlating with higher dislocation density observed in the nanocrystals. As a conclusion, 1-octanol is proposed as a functional impurity that varies particle size and nonradiative photophysical processes in the ZnCdSSe/ZnS colloidal nanocrystals.Article Citation - WoS: 3Citation - Scopus: 4Enhanced Thermostability of the Immobilized Thermoalkalophilic Esterase Onto Magnetic-Cornstarch Nanoparticle(Wiley, 2022) Öz, Yasin; Sürmeli, Yusuf; Şanlı Mohamed, GülşahThe immobilization of the biocatalysts onto magnetic nanoparticles has been extensively applied as the external magnetic field facilitates the enzyme recovery from the reaction mixture. In the present study, glutaraldehyde-modified magnetite-cornstarch nanoparticles (MCNs) were successfully synthesized, elaborately characterized by ZetaSizer and surface-enhanced Raman spectroscopy, and used for the immobilization of a thermoalkalophilic esterase from Geobacillus sp. The optimal immobilization conditions were obtained at 65 degrees C, 2:3 molar ratios of Fe2+:Fe3+, and 1 g cornstarch resulted in approximately 90 nm magnetic particles in size. Also, immobilization yield and immobilization efficiency of the esterase were found as 74% and 82%, respectively. Scanning electron microscopy micrographs showed that MCNs were uniform, spherical in shape, and well dispersed and esterase immobilized MCNs displayed similar morphology as free MCNs. The maximum activity of free and immobilized esterase was obtained at 65 degrees C and pH 9. Immobilization onto glutaraldehyde-modified MCNs significantly enhanced the esterase thermostability. Additionally, the immobilized esterase kept its residual activity of 75% after three sequential cycles, suggesting that it has favorable operational stability.Article Citation - WoS: 7Citation - Scopus: 8Thermoalkalophilic Recombinant Esterase Entrapment in Chitosan/Calcium Beads and Its Characterization(Wiley, 2021) Tercan, Cisem; Sürmeli, Yusuf; Şanlı Mohamed, GülşahBACKGROUND Esterases (EC 3.1.1.1), a class of hydrolases, degrade the ester bonds of lipids into alcohol and carboxylic acids and synthesize carboxylic ester bonds. They are used in a variety of biotechnological, industrial, environmental, and pharmaceutical applications due to their many valuable properties. Particularly, extremophilic esterases with many superior properties are of great interest for various reactions. Immobilization of enzymes may provide some advantages over free enzymes not only to improve the properties of enzymes but also to increase the reusability of biocatalyst in industrial applications. Therefore, many different immobilization applications for enzymes have been reported in various studies. To our knowledge, a thermophilic esterase has not so far been immobilized by entrapment using chitosan/calcium/alginate-blended beads. Here, we reported the immobilization of thermoalkalophilic recombinant esterase by entrapment using chitosan/calcium/alginate-blended beads, and then the entrapped esterase was characterized biochemically in details. RESULTS In the present study, a thermophilic recombinant esterase was immobilized by entrapment in chitosan/calcium/alginate-blended beads for the first time. The 0.5 mg mL(-1) purified recombinant esterase was entrapped in 1% chitosan, 2% alginate, and 0.7 M CaCl2 blended beads. The results showed that immobilization yield and entrapment efficiency of the entrapped esterase were 69.5% and 80.4%, respectively. SEM micrograph showed that the surface of the beads resembled a mesh and very compact structures. Chitosan/calcium/alginate-blended beads exhibited an 18.8% swelling ratio and had a moderate porous structure. The entrapment technique highly enhanced the thermostability of the esterase and shifted its optimum temperature from 65 to 80 degrees C. The immobilized esterase was very stable in a wide range of pH (8.5-11) displaying maximum activity at pH 9. ZnCl2 slightly increased the activity of immobilized esterase whereas several metal ions reduced the enzyme activity. When the enzyme was immobilized in chitosan/calcium/alginate-blended beads, its K-m increased about 2 times and V-max value decreased almost 1.5 times. Immobilization allowed repeated uses of the esterase having good operational stability in a continuous process. CONCLUSION The results revealed that the immobilization of a thermophilic recombinant esterase by entrapment in chitosan/calcium/alginate-blended beads exhibited considerably better compared to other immobilization processes with various entrapment strategies. (c) 2021 Society of Chemical Industry (SCI).Article Citation - WoS: 5Citation - Scopus: 6Toward Single-Layer Janus Crystals: Off-Balance Materials From Synthesis To Nanotechnology Applications(American Institute of Physics, 2021) Oğuztürk, H. Esra; Sözen, Yiğit; Akyol, Cansu; Özkendir İnanç, Dilce; Yıldız, Ümit Hakan; Şahin, HasanThe existence of things is directly related to their structural symmetry in a broad framework ranging from atoms to crystalline materials and from simple cells to complex organisms like humans. However, structural imbalance that occurs through natural or artificial means can provide completely different advantages. Molecules, crystals, and complex structures with structural imbalance constitute the family of Janus-type materials. This perspective provides a comprehensive discussion on the synthesis techniques of Janus-type materials, their use in fields from biology to materials science, and very recent studies on the family of 2D ultrathin graphene-like structures. We believe that, thanks to the advances in experimental techniques, the few-atom-sized off-balanced materials will be indispensable parts of the nanotechnology products that soon will be used in our daily lives.Article Citation - WoS: 27Citation - Scopus: 28Biocomposite Scaffolds for 3d Cell Culture: Propolis Enriched Polyvinyl Alcohol Nanofibers Favoring Cell Adhesion(John Wiley and Sons Inc., 2021) Bilginer, Rumeysa; Özkendir İnanç, Dilce; Yıldız, Ümit Hakan; Arslan Yıldız, AhuThe objective of this work is generation of propolis/polyvinyl alcohol (PVA) scaffold by electrospinning for 3D cell culture. Here, PVA used as co-spinning agent since propolis alone cannot be easily processed by electrospinning methodology. Propolis takes charge in maximizing biological aspect of scaffold to facilitate cell attachment and proliferation. Morphological analysis showed size of the electrospun nanofibers varied between 172-523 nm and 345-687 nm in diameter, for non-crosslinked and crosslinked scaffolds, respectively. Incorporation of propolis resulted in desired surface properties of hybrid matrix, where hybrid scaffolds highly favored protein adsorption. To examine cell compatibility, NIH-3T3 and HeLa cells were seeded on propolis/PVA hybrid scaffold. Results confirmed that integration of propolis supported cell adhesion and cell proliferation. Also, results indicated electrospun propolis/PVA hybrid scaffold provide suitable microenvironment for cell culturing. Therefore, developed hybrid scaffold could be considered as potential candidate for 3D cell culture and tissue engineering.Article Citation - WoS: 3Citation - Scopus: 4Lipid Bilayer on Wrinkled-Interfaced Graphene Field Effect Transistor(Elsevier Ltd., 2021) Özkendir İnanç, Dilce; Çelebi, Cem; Yıldız, Ümit HakanThis study describes lipid bilayer-based sensor interface on SiO2 encapsulated graphene field effect transistors (GFET). The SiO2 layer was utilized as a lipid compatible surface that drives bilayer formation. The two types of surface morphologies i) wrinkled morphology by thermal evaporation (TE) and ii) flat morphology by pulsed electron deposition (PED) were obtained. The sensing performance of wrinkled and flat interfaced-GFETs were investigated, pH sensitivity of wrinkled interfaced-GFETs were found to be ten fold larger than the flat ones. The enhanced sensitivity is attributed to thinning of the oxide layer by formation of wrinkles thereby facilitating electrostatic gating on graphene. We foresee that described wrinkled SiO2 interfaced-GFET holds promise as a cell membrane mimicking sensing platform for novel bioelectronic applications. © 2020Article Citation - WoS: 6Citation - Scopus: 8Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator(American Chemical Society, 2019) Gökbulut, Belkıs; İnanç, Arda; Topçu, Gökhan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa Muammer; İnci, Mehmet NaciIn this paper, CdTe quantum dots (QDs)-doped single electrospun polymer nanofibers are partially coated with gold nanoparticles to form distinct hybrid photonic-plasmonic nanoresonators to investigate the critical role of the cavity-confined hybrid mode on the modification of the spontaneous emission dynamics of the fluorescent emitters in low-Q photonic cavities. A total enhancement factor of 11.2 is measured via a time-resolved experimental technique, which shows that there is an increase of about three times in the spontaneous emission rate for the QDs-doped gold nanoparticle-decorated nanofibers as they are compared with those uncoated ones. The physical mechanism affecting the spontaneous emission rate of the encapsulated QDs in such a hybrid photonic-plasmonic nanoresonator is explained to be due to regeneration of the mode field in the nanofiber cavity upon the interaction of the dipoles with the surface plasmons of distinctive gold nanoparticles that surround the outer surface of the nanofiber.Article Citation - WoS: 15Citation - Scopus: 17Improved Activity of Alpha-L From Geobacillus Vulcani Gs90 by Directed Evolution: Investigation on Thermal and Alkaline Stability(John Wiley and Sons Inc., 2019) Sürmeli, Yusuf; İlgü, Hüseyin; Şanlı Mohamed, Gülşahalpha-L-Arabinofuranosidase (Abf) is a potential enzyme because of its synergistic effect with other hemicellulases in agro-industrial field. In this study, directed evolution was applied to Abf from Geobacillus vulcani GS90 (GvAbf) using one round error-prone PCR and constructed a library of 73 enzyme variants of GvAbf. The activity screening of the enzyme variants was performed on soluble protein extracts using p-nitrophenyl alpha-L-arabinofuranoside as substrate. Two high activity displaying variants (GvAbf L307S and GvAbf Q90H/L307S) were selected, purified, partially characterized, and structurally analyzed. The specific activities of both variants were almost 2.5-fold more than that of GvAbf. Both GvAbf variants also exhibited higher thermal stability but lower alkaline stability in reference to GvAbf. The structural analysis of GvAbf model indicated that two mutation sites Q90H and L307S in both GvAbf variants are located in TIM barrel domain, responsible for catalytic action in many Glycoside Hydrolase Families including GH51. The structure of GvAbf model displayed that the position of L307S mutation is closer to the catalytic residues of GvAbf compared with Q90H mutation and also L307S mutation is conserved in both variants of GvAbf. Therefore, it was hypothesized that L307S amino acid substitution may play a critical role in catalytic activity of GvAbf. (C) 2018 International Union of Biochemistry and Molecular Biology, Inc.