12 results
Search Results
Now showing 1 - 10 of 12
Publication Embargo Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures(Springer, 233 Spring St, New York, Ny 10013 Usa, 2012-11-28) Erol, Ayşe; Akalın, Elif; Sarcan, Fahrettin; Dönmez, Ömer; Arıkan, Mehmet Çetin; Puustinen, Janne; Guina, Mircea; AKYÜZ, SEVİM; TR54563; TR1362; TR108291; TR46357; TR150431; TR10127The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga1 -aEuro parts per thousand x In (x) N (y) As1 -aEuro parts per thousand y /GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.Publication Metadata only FT-IR spectroscopy and multivariate analysis as an auxiliary tool for diagnosis of mental disorders: Bipolar and schizophrenia cases(Pergamon-Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1Gb, England, 2016-01-05) Arslan, M.; Ünsalan, Ozan; Araujo-Andrade, C.; Kurt, Ethan; Karatepe, Hasan Turan; Yılmaz, Ayberk; Bölükbaşı Yalçınkaya, Olcay; Herken, Hasan; ILDIZ, GÜLCE ÖĞRÜÇ; 107326; 106111; 242682; 175748; 123240In this study, a methodology based on Fourier-transform infrared spectroscopy and principal component analysis and partial least square methods is proposed for the analysis of blood plasma samples in order to identify spectral changes correlated with some biomarkers associated with schizophrenia and bipolarity. Our main goal was to use the spectral information for the calibration of statistical models to discriminate and classify blood plasma samples belonging to bipolar and schizophrenic patients. IR spectra of 30 samples of blood plasma obtained from each, bipolar and schizophrenic patients and healthy control group were collected. The results obtained from principal component analysis (PCA) show a clear discrimination between the bipolar (BP), schizophrenic (SZ) and control group' (CG) blood samples that also give possibility to identify three main regions that show the major differences correlated with both mental disorders (biomarkers). Furthermore, a model for the classification of the blood samples was calibrated using partial least square discriminant analysis (PLS-DA), allowing the correct classification of BP, SZ and CG samples. The results obtained applying this methodology suggest that it can be used as a complimentary diagnostic tool for the detection and discrimination of these mental diseases. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only FT-IR and FT-Raman spectroscopic investigations of adsorption of 2,2′-biquinoline by smectite group clay minerals from Anatolia(Elsevier, 2000-02) Davies, J. Eric D.; AKYÜZ, ZEKİ TANIL; AKYÜZ, SEVİM; 10127The sorption of 2,2′-biquinoline onto natural and ion-exchanged montmorillonite (Fe-, Co- or Cu-montmorillonite) and saponite from Anatolia have been investigated using FT-IR and FT-Raman Spectrometry. The intercalation of 2,2′-biquinoline within natural and ion-exchanged montmorillonite and saponite has been shown by X-ray diffraction to increase the interlayer spacing. The difference of basal spacing of air-dried clays and biquinoline treated ones shows monolayer arrangement. Raman spectroscopy was particularly useful for investigation of clay-organic interaction. Vibrational spectroscopy indicates that intercalated 2,2′-biquinoline molecules are coordinated to exchangeable cations (directly and indirectly through water bridges) and/or Lewis acid sites or as bidentate ligand.Publication Metadata only Adsorption Of 3-And 4-Aminopyridine On Loughlinite-An IR Spectroscopic Study(Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands, 2010-05-26) AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR10127; TR111424In this study adsorption of 3- and 4-aminopyridine on loughlinite (Na-sepiolite) have been investigated by FT-IR spectroscopy. Spectroscopic results indicate that sorbed aminopyridine molecules onto loughlinite are coordinated to Lewis acidic centers, zeolitic/bound water molecules, and surface silanol groups by hydrogen bonding interaction through pyridine ring nitrogen lone pairs. Some of the adsorbed molecules coordinate to Bronsted acidic centers and aminopyridinium cationic surface species are also generated. (C) 2010 Elsevier B.V. All rights reserved.Publication Metadata only Archaeometric investigations of terra-cotta sarcophages from the excavations at einos (Enez) Turkey: An EDXRF Study(Asian Journal Of Chemistry, 11/100 Rajendra Nagar, Sector 3,, Sahibabad 201 005, Ghaziabad, India, 2011-07) Kurap, Gülnur; Başaran, Sait; Uçar Çakan, Banu; Özsait Kocabaş, Işıl; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR10127; TR111424; TR136713; TR53588; TR122283In this study 11 clazomenian type sargophagi, found in ancient Ainos, one of the important archaeological site of Turkey, were investigated by EDXRF spectroscopy. The elemental composition of the painted parts and body samples of the sarcophagi were determined and the pigments used in the decorated parts were identified. Chemometric treatment of the XRF data was performed and principle component analysis revealed presence of 3 distinct groups.Publication Metadata only Vibrational Spectroscopic Investigation of 2,2 '-Bipyridine Adsorbed on Loughlinite from Aqueous Suspensions(Asian Journal Of Chemistry, 11/100 Rajendra Nagar, Sector 3,, Sahibabad 201 005, Ghaziabad, India, 2010-01) AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR111424; TR10127The adsorption of 2,2'-bipyridine onto loughlinite (Na-sepiolite) has been investigated by FT-IR and micro-Raman spectroscopy. Spectroscopic results indicate the formation of monoanionic surface species. Most of the adsorbed molecules are incorporated in the channels of the clay structure and coordinated to Lewis acidic centers directly or indirectly through water molecules.Publication Metadata only FT-IR spectroscopic investigation of adsorption of 3-aminopyridine on sepiolite and montmorillonite from Anatolia(Elsevier, 2001-05-30) Yakar, A. E.; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; 10127The adsorption of 3-aminopyridine by natural sepiolite and montmorillonite from Eskisehir (Anatolia) was investigated in the temperature range from 20 to 125°C by infrared spectrometry using a variable temperature unit. The spectroscopic results indicate that the 3-aminopyridine molecules adsorbed on sepiolite are coordinated to Lewis acidic sites and/or surface hydroxyls by H-bonding interaction through pyridine ring nitrogen lone pairs. Surface Bronsted acid strength of sepiolite is weak and 3-aminopyridinium is not detected under the conditions applied in this study. It must be noted that the adsorption of aminopyridine affected the hydroxyl group vibrations of sepiolite. The intercalation of 3-aminopyridine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacing. IR spectroscopy indicates that sorbed 3-aminopyridine molecules by montmorillonite are mostly coordinated to exchangeable cations directly or indirectly through water bridges. The formation of 3-aminopyridinium cation is also detected at elevated temperatures.Publication Metadata only Conformational Analysis And Vibrational Spectroscopic Investigation Of L-Proline-Tyrosine (L-Pro-Tyr) Dipeptide(Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands, 2011-05-03) Kecel, Serda; Özel, Ayşen; Çelik, Sefa; Agaeva, Gulshen; AKYÜZ, SEVİM; TR110526; TR110745; TR10127; TR110147In this study the conformational properties of the drug based dipeptide L-proline-L-tyrosine (Pro-Tyr) in its monomeric and dimeric forms, have been investigated by molecular mechanic and ab initio calculations. The energy calculations on Pro-Tyr dipeptide as a function of side chains torsion angles, enable us to determine their energetically preferred conformations. One-hundred and eight possible conformations of Pro-Tyr dipeptide have been investigated by conformational analysis and the low energy conformations of dipeptide have been determined by using the Ramachandran maps. Afterwards, the geometrical parameters of obtained stable conformations were used as starting parameters for quantum chemical calculations. The molecular structure of Pro-Tyr dipeptide, in the ground electronic state (in vacuum) was optimized by density functional theory method with B3LYP functional and using 6-31G(d,p) and 6-31++G(d,p) basis sets. The dimeric forms of the dipeptide were also formed and energetically preferred conformations of dimers were investigated using the same method and the same level of theory by using 6-31G(d,p) basic set. The fundamental vibrational wavenumbers, IR intensities and Raman activities of the global conformation of monomeric and dimeric forms of the dipeptide were calculated and compared with the experimental vibrational spectra of solid Pro-Tyr dipeptide. The total energy distributions (TED) of the vibrational modes were calculated by using Scaled Quantum Mechanical (SQM) analysis. Vibrational assignment was performed on the basis of calculated total energy distribution (TED) of the modes. (C) 2011 Elsevier B.V. All rights reserved.Publication Metadata only FT-IR spectroscopic investigations of benzidine and bipyridyls adsorbed on diatomite from Anatolia(Elsevier, 2001-05-30) Özer, N. M.; AKYÜZ, ZEKİ TANIL; AKYÜZ, SEVİM; 10127FT-IR spectra of benzidine (bnz), 2,2′-bipyridyl (2,2′-bpy) and 4-4′-bipyridyl (4-4′-bpy) adsorbed on natural diatomite from Kutahya-Alayunt (Anatolia, Turkey) have been investigated. Vibrational results indicate the presence of chemisorbed species. No physical sorbed species has been detected. Bnz and 2,2′-bpy treated diatomite samples were found to be coloured, whereas 4,4′-bpy treated diatomite was not altered in colour. The formation of cationic (bnz+ and bnz2+) or anionic (2,2′-bpy−) surface species has also been detected in the case of bnz or 2,2′-bpy treated diatomite, respectively.Publication Metadata only Vibrational Spectroscopic Investigation of Tetracyanopalladate Bridged Two Dimensional Coordination Polymer Compounds of Pyrimidine(Asian Journal Of Chemistry, 11/100 Rajendra Nagar, Sector 3,, Sahibabad 201 005, Ghaziabad, India, 2013-11) Akkaya, Yasemin; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; 175409; 10127; 111424The two dimensional layered polymer compounds, M(PM)(2)Pd(CN)(4) {where M = Mn, Zn or Cd; PM = pyrimidine} have been prepared for the first time and their FT-IR (4000-400 cm(-1)) and Raman (4000-50 cm(-1)) spectra are reported. The compounds built up of [M(PM)(2)](2+) cations and square-planar [Pd(CN)(4)](2-) anions, which are linked by the bridging mu(2)-CN- groups. Pyrimidine was coordinated to M(II) through one of the nitrogen atom of its heterocyclic ring, as monodentate ligand. Vibrational assignments are given for the bands arising from the tetracyanopalladate layers and coordinated pyrimidine. The main bands of the vibrational spectra in the low frequency region were assigned to the stretching and deformational vibrations {nu(Pd-C), delta(PdCN), pi(PdCN), delta(CPdC)} originating from the host lattices.