Fizik Bölümü / Department of Physics
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Publication 5-Methylhydantoin: From isolated molecules in a low-temperature Aaon matrix to solid state polymorphs characterization(2017-12) Nogueira, Bernardo.A.; Canotilho J.; Eusébio MES; Henriques MSC; Paixão JA; Fausto R.; ILDIZ, GÜLCE ÖĞRÜÇThe molecular structure, vibrational spectra and photochemistry of 5-methylhydantoin (C4H6N2O2; 5-MH) were studied by matrix isolation infrared spectroscopy and theoretical calculations at the DFT(B3LYP)/6-311++G(d,p) theory level. The natural bond orbital (NBO) analysis approach was used to study in detail the electronic structure of the minimum energy structure of 5-MH, namely the specific characteristics of the σ and π electronic systems of the molecule and the stabilizing orbital interactions. UV irradiation of 5-MH isolated in argon matrix resulted in its photofragmentation through a single photochemical pathway, yielding isocyanic acid, ethanimine, and carbon monoxide, thus following a pattern already observed before for the parent hydantoin and 1-methylhydantoin molecules. The investigation of the thermal properties of 5-MH was undertaken by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM) and Raman spectroscopy. Four different polymorphs of 5-MH were identified. The crystal structure of one of the polymorphs, for which it was possible to grow up suitable crystals, was determined by X-ray diffraction (XRD). Two of the additional polymorphs were characterized by powder XRD, which confirmed the molecules pack in different crystallographic arrangements.Publication A comparative study of the yellow dent and purple flint maize kernel components by Raman spectroscopy and chemometrics(2019-05-15) Kabuk, Hayrunnisa Nur; Kaplan, Ekin Su; Halimoğlu, Gökhan; Fausto, Rui; ILDIZ, GÜLCE ÖĞRÜÇIn this investigation the potential of micro-Raman spectroscopy, coupled to a simple, standard chemometric method (principal component analysis, PCA), as a fast, cheap, field method to investigate maize kernel components (endosperm, germ and peel) is demonstrated. Particular emphasis was given to the determination of the relative protein and amylose/amylopectin contents in maize endosperm of yellow dent and purple flint corn species, the two major maize varieties produced in Turkey. It is shown that the studied yellow dent corn type has a comparatively larger content of protein (3.4%) and a higher amylopectin/amylose ratio in the endosperm than the studied purple flint variety (a 11% decrease of amylopectin was found in going from the studied yellow dent to the purple flint corn), while the germs of the two species differ mostly by the presence of a slightly larger amount of starch in the case of the yellow dent corn, the oil composition of both species being identical within the resolution of the used method of analysis. The spectra of the maize peels reveal essentially the presence of cellulose and lignin in similar amounts in the two types of corn. (C) 2019 Elsevier B.V. All rights reserved.Publication A Multi-Technique Approach to The Study of Hydantoins: From Isolated Molecules to Polymorphs(2019-07-22) ILDIZ, GÜLCE ÖĞRÜÇ; 107326Hydantoins have remarkable interest from the chemical and biological perspectives, and they have also been shown to receive widespread applications in medicine, agriculture and chemical industry. They have been clinically used as antiepileptic and antibacterial drugsand for cancer and AIDS treatments, and are also used currently as herbicides and fungicides. In this talk, 1 will present recent data on a series of simple hydantoins, obtained using a multi-technique approach that allowed characterizing the single molecules of these compounds in relation to their structure, vibrational spectra and photochemistry, and also to determine the spectroscopic and thermal properties oftheir neat condensed phases (with emphasis given to polymorphism). The main technique used for the investigation of the isolated molecules was matrix isolation infrared spectroscopy, complemented by up-to-date quantum chemical calculations. For the investigation of the condensed phases, differential scanning calorimetry (DSC), polarized-light thermomicroscopy, X-ray diffraction, and infrared and Raman spectroscopies were used. The used multidisciplinary methodology allowed to attain a considerably broad understanding of the structural, vibrational, photochemical and thermal properties of the hydantoin moiety, which may be seen as a gateway for assessing the reactivity and biological activity of this type of compounds.Publication Benchmarking the Anisotropy of Nitroxyl Radical Solvation With IR Spectroscopy(The Royal Society of Chemistry, 2024) Bras, Elisa M.; Zimmermann, Charlotte; FAUSTO, RUI; Suhm, Martin A.Two simple nitroxyl radicals, di-tert-butyl nitroxyl (DTBN) and 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) are solvated by one or two water, methanol, tert-butyl alcohol or phenol molecules. The resulting low temperature IR spectra of the vacuum-isolated microsolvates in the OH stretching range are assigned based on harmonic DFT predictions for closed shell solvent dimers and trimers and their offset from experiment, to minimise theory-guided assignment bias. Systematic conformational preferences for the first and second solvent molecule are observed, depending on the conformational rigidity of the radical. These assignments are collected into an experimental benchmark data set and used to assess the spectral predicting power of different DFT approaches. The goal is to find inexpensive computational methods which provide reliable spectral predictions for this poorly explored class of microsolvates.Publication Composition analysis of soybean salt resistant mutants by raman spectroscopy and chemometrics(2019) Yılmaz, Ayberk; Kabuk, Hayrunnisa Nur; Kaygısız, Ersin; Fausto, Rui; MERİÇ, SİNAN; AYAN, ALP; ATAK, ÇİMEN; ÇELİK, ÖZGE; ILDIZ, GÜLCE ÖĞRÜÇ; 107326; 6653; 175748; 185510; 219257; 113987Soya seeds belonging to fourth generation mutants (MPublication Conformational Analysis and Photochemistry of 2-Chloro-6-fluorobenzoic Acid Monomers in Solid Xenon(2019-11) Fausto, Rui; ILDIZ, GÜLCE ÖĞRÜÇ; 107326In this study, the conformational space of 2-chloro-6-fluorobenzoic acid (CFBA) has been investigated theoretically using density functional theory, with the B3LYP functional and the 6-311++G(d,p) basis set, and experimentally by matrix isolation infrared spectroscopy. The calculations allowed identification of 3 different non-planar conformers of the compound, the lowest energy form (I) exhibiting the carboxylic acid group in the cis arrangement (O=C- O-H dihedral equal to ~0°), and the two higher energy forms (II and III) bearing a trans carboxylic group (O=C-O-H dihedral equal to ~180°) (see Figure). The energies of conformers II and III are larger than that of the most stable conformer I by 17.07 and 17.31 kJ mol-1 , respectively. The considerably large energy difference between the two trans conformers and the cis form implies that only this last species should exist significantly populated in the room temperature gas phase conformational equilibrium. In consonance with the theoretical predictions, only conformer I could be trapped from the room temperature vapor of the compound into low temperature (10 K) solid xenon. The theoretical vibrational characterization of all 3 conformers of CFBA and the assignment of the experimental IR spectrum of conformer I were undertaken.The matrix-isolated monomers of the compound were then irradiated z/7 situ using narrowband UV light with L = 235 nm. The major observed reaction channel was decarboxylation, leading to production of CO2 and l-chloro-3-fluorobenzene. Carbon monoxide was also detected in the infrared spectra of the photolysed solid Xc matrices of the compound, indicated that UV- induced decarbonylation of CFBA takes also place in some extent, though the expected accompanying photoproduct (2-chloro-6-fluorophenol) could not be experimentally sensed.Publication Crystallization Kinetics: Relationship Between Crystal Morphology and the Cooling Rate-Applications for Different Geological Materials(MDPI, 2023-01-24) Aysal, Namık; Kurt, Yiğit; ILDIZ, GÜLCE ÖĞRÜÇ; Öztürk, Hüseyin; Yeşiltaş, Mehmet; Laçin, Davut; Öngen, Sinan; Nikitin, Timur; FAUSTO, RUICrystal morphology is controlled by several physicochemical parameters such as the temperature, pressure, cooling rate, nucleation, diffusion, volatile composition, and viscosity. The development of different crystal morphologies is observed as a function of the cooling rate in many different rock types (i.e., glassy volcanic rocks, and archeometallurgical slags). Crystallization is a two-stage kinetic process that begins with the formation of a nucleus and then continues with the accumulation of ions on it. The shapes of the crystals depend on the degree of undercooling (& UDelta;T), and euhedral crystals, having characteristic forms that reflect their crystallographic internal structure, that grow just below their liquidus temperature. In this study, crystal morphologies in different minerals (e.g., quartz, sanidine, olivine, pyroxene, magnetite, etc.) that had developed in silicic volcanic rocks (spherulites) and slags from ancient mining were investigated and characterized using optical microscopy, X-ray diffraction, and Fourier-transform infrared (FTIR), Raman, and scanning electron microscope-energy dispersive X-ray fluorescence (SEM-EDX) spectroscopic techniques. Depending on the increase in the cooling rate, quartz, feldspar, olivine, pyroxene, and magnetite minerals were found to crystallize in subhedral, skeletal, dendritic, spherical, bow-tie and fibrous forms in glassy volcanic rocks and archeometallurgical slags.Publication Enez Kazısından Çıkartılan Bazı Arkeolojik Seramik ve Killerin FTIR, Mikro-Raman, EDXRF, XRD ve Kemometrik Yöntemler ile Analizi(2019-09) Çelik, Sefa; E.Özel, Ayşen; Başaran, Sait; AKYÜZ, SEVİM; 10127; 110147; 110745Potteries are the most abundant findings among the archeological artifacts. These findings, whose main raw material is clay, give important information about the civilization, culture, technology and trade of that period. Clay minerals undergo chemical and structural changes during the firing; e.g. during thermal treatment the structural collapse due to loss of structural hydroxyls, transformation to different mineral structures due to reaction with calcite in the structure and phase changes. For this reason, investigation of the mineral structures of the ancient potteries gives information about the firing temperature and firing conditions. Since XRD provides information mineral phases only in crystalline state, in combination to XRD the FTIR and Raman spectroscopic investigations and the determination of elemental contents by EDXRF allow us to determine the firing- temperature and -conditions in more detail. In this study, pottery fragments belonging to 4th-6th century BC, excavated in Enez- Turkey, were analyzed by different analytical techniques, in comparison with those of the local clays unearthed during the excavations. The firing temperatures and firing conditions were estimated. The XRD analysis of the raw clay found in the excavation area showed that it contained montmorillonite, illite and muscovite. The comparative FTIR and micro-Raman spectroscopic, EDXRF and XRD analyzes of the terracotta remains allowed to determine the chemical and mineralogical contents of the ceramic fragments. Moreover, chemometric techniques were applied on FTIR results in order to determine similarities and dissimilarities between archaeological findings and to reveal the distinct groups. Principal component analysis and cluster analysis techniques were used.Publication Glimmmerring Light of Transcendence(2011) Sezgin, ErkutPhenomenology differs from the traditional epistemological ontological theories in that theorizing with words are given up for elucidating the signifying phenomena in the weave of which intentionality are structured to operate with words used as means to describe ends, in which means are described as "words and descriptions", "language" as such; and ends are described as "the reality", "objects", "things", "events", "world" as such. Such way of using language in theories of subject object epistemologies is a form of expression of an intentionality the modalities of which are operationally structured with learning and operating with the rules of pictures held fast as standards, rules of criteria of the truth beliefs in identifying what is "true" and "real" in language. Failure of awareness of manifest internal connections of signifying phenomena expressive of intentionality and truth beliefs in connection with the use of pictures and rules of language manifests with its own doxa in the form of attributing or denying essential qualities as to subject object descriptions and as to their interactions, in contrast to an awareness that is capable of tracing back and forth the historical structuring of intentionality operational with pictures and rules of historical languages. The latter only clarifies manifest phenomena expressive of intentionality in internal connections operating and using signs as means and ends without presupposing or introducing entities by means of projecting pictures of language. That clarification works by elucidating the identities and differences attributed to entities in terms of the uses of pictures or signs in internal connection with the uses of other signs the rules of which are kept fast and change by the changing paradigms of cultural-conventional-historical language-games. Here transcendence amounts to the trans-historical dimension of awareness which unknots the knots of operational thinking habits with rules and pictures of historical languages; which are habits that otherwise so chain thinking with the historical intentionality of a historical epoch and systems of beliefs as not to respond and communicate anymore with the self-illuminating light of awareness as characterized by Plato's cave metaphor.Publication Hydantoins and mercaptoimidazoles: Vibrational spectroscopy as a probe of structure and reactivity in different environments, from the isolated molecule to polymorphs(2019) Fausto, Rui; Brás, E.M.; Nogueira, Bernardo A.; ILDIZ, GÜLCE ÖĞRÜÇIn this chapter, we highlight the power of vibrational spectroscopy as central technique to investigate the structure and reactivity of two relevant families of nitrogen-containing heterocyclic molecules: hydantoins and mercaptoimidazoles. Infrared spectroscopy is used in connection with the matrix isolation technique to investigate the structures of the isolated molecules and their photochemistry, while both infrared and Raman spectroscopies, supplemented by thermodynamics, microscopy, and diffraction techniques, are used to investigate neat condensed phases of the compounds and transitions between these phases. The experimental studies are supported by extensive computational studies, which include several approaches for detailed analysis of the electron density.Publication In silico analysis of Sulpiride, synthesis, characterization and in vitro studies of its nanoparticle for the treatment of schizophrenia(2019-06-27) Keçel Gündüz, S.; Budama Kilinç, Y.; Çakır Koç, R.; Zorlu, T.; Bıçak, B.; Kökçü, Y.; Kaya, Z.; Özel, A.E.; AKYÜZ, SEVİMBackground: Sulpiride,which has selectively dopaminergic blocking activity, is a substituted benzamide antipsychotic drug plays a prominent role in the treatment of schizophrenia, more selective and primarily blocks dopamine D2 and D3 receptor. Objective: This study has two main objectives, firstly; the molecular modeling studies (MD and Docking, ADME) were conducted to define the molecular profile of sulpiride and sulpiride-receptor interactions. The another aim of this study was to synthesize polymeric nanoparticles with chitosan, having the advantage of slow/controlled drug release, to improve drug solubility and stability, enhances utility, and reduces toxicity. Method: Molecular dynamic simulation was applied to determine the conformational change and stability (in water) of the drug and the binding profile to D3 dopamine receptor was performed by molecular docking calculations. The pharmacological properties of the drug were revealed by ADME analysis. The ionic gelation method was used to prepare sulpiride loaded chitosan nanoparticles (CS NPs). The Dynamic Light Scattering (DLS), UV–vis absorption (UV), Scanning Electron Microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy techniques were carried out to characterize the nanoparticles. In vitro cell cytotoxicity experiments examined with MTT assay on mouse fibroblast (L929), human neuroblastoma (SH-SY5Y) and glioblastoma cells (U-87). The statistical evaluations were produced by ANOVA. Results: The residues (ASP-119, PHE-417) of D3 receptor provided a stable docking with the drug, and the important pharmacological values (blood brain barrier, cacao2 permeability and human oral absorption) were also determined.The average particle size, PdI and zeta potential value of sulpiride-loaded chitosan NPs having a spherical morphology were calculated as 96.93 nm, 0.202, and +7.91 mV. The NPs with 92.8% encapsulation and 28% loading efficiency were found as an slow release profile with 38.49% at the end of the 10th day. Due to the formation of encapsulation, the prominent shifted wavenumbers were also identified. Mitochondrial activity of U87, SHSY-5Y and L929 cell line were assayed and evaluated using the SPSS program. Conclusion: To provide more efficient use of Sulpiride having a low bioavailability of the gastrointestinal tract, the nanoparticle formulation with high solubility and bioavailability was designed and synthesized for the first time in this study for the treatment of schizophrenia. In addition to all pharmacological properties of drug, the dopamine blocking activity was also revealed. The toxic effect on different cell lines have also been interpreted.Publication In Silico design of AVP (4-5) peptide and synthesis, characterization and in vitro activity of chitosan nanoparticles(2020-01) Kecel-Gunduz, Serda; Budama-Kilinc, Yasemin; Çakır Koç, Rabia; Zorlu, Tolga; Bicak, Bilge; Kökçü, Yağmur; Özel, Aysen E.; AKYÜZ, SEVİM; 110526; 22705; 277135; 10127Background Arginine-vasopressin (AVP) is a neuropeptide and provides learning and memory modulation. The AVP (4-5) dipeptide corresponds to the N-terminal fragment of the major vasopressin metabolite AVP (4-9), has a neuroprotective effect and used in the treatment of Alzheimer's and Parkinson's disease. Methods The main objective of the present study is to evaluate the molecular mechanism of AVP (4-5) dipeptide and to develop and synthesize chitosan nanoparticle formulation using modified version of ionic gelation method, to increase drug effectiveness. For peptide loaded chitosan nanoparticles, the synthesized experiment medium was simulated for the first time by molecular dynamics method and used to determine the stability of the peptide, and the binding mechanism to protein (HSP70) was also investigated by molecular docking calculations. A potential pharmacologically features of the peptide was also characterized by ADME (Absorption, Distribution, Metabolism and Excretion) analysis. The characterization, in vitro release study, encapsulation efficiency and loading capacity of the peptide loaded chitosan nanoparticles (CS NPs) were performed by Dynamic Light Scattering (DLS), UV-vis absorption (UV), Scanning Electron Microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy techniques. Additionally, in vitro cytotoxicity of the peptide on human neuroblastoma cells (SH-SY5Y) was examined with XTT assay and the statistical analysis was evaluated. Results The results showed that; hydrodynamic size, zeta potential and polydispersity index (PdI) of the peptide-loaded CS NPs were 167.6 nm, +13.2 mV, and 0.211, respectively. In vitro release study of the peptide-loaded CS NPs showed that 17.23% of the AVP (4-5)-NH2 peptide was released in the first day, while 61.13% of AVP (4-5)-NH2 peptide was released in the end of the 10th day. The encapsulation efficiency and loading capacity were 99% and 10%, respectively. According to the obtained results from XTT assay, toxicity on SHSY-5Y cells in the concentration from 0.01 mu g/mu L to 30 mu g/mu L were evaluated and no toxicity was observed. Also, neuroprotective effect was showed against H2O2 treatment. Conclusion The experimental medium of peptide-loaded chitosan nanoparticles was created for the first time with in silico system and the stability of the peptide in this medium was carried out by molecular dynamics studies. The binding sites of the peptide with the HSP70 protein were determined by molecular docking analysis. The size and morphology of the prepared NPs capable of crossing the blood-brain barrier (BBB) were monitored using DLS and SEM analyses, and the encapsulation efficiency and loading capacity were successfully performed with UV Analysis. In vitro release studies and in vitro cytotoxicity analysis on SHSY-5Y cell lines of the peptide were conducted for the first time.Publication Investigation of the Neolithic Potteries of 6th Millennium BC from GöytepeAzerbeijan by Spectroskopic and Chemometric Methods(2019-08) Guliyev, Ferhad; Çelik, Sefa; E.Özel, Ayşen; Alakbarov, Valeh; AKYÜZ, SEVİM; 10127Publication Investigations of the Neolithic potteries of 6th millennium BC from Goytepe-Azerbaijan by vibrational spectroscopy and chemometric techniques(ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2019-11) Guliyev, Ferhad; Çelik, Sefa; E.Özel, Ayşen; Alakbarov, Valeh; AKYÜZ, SEVİMThis article presents the results of the vibrational spectroscopic and chemometric analyses of Neolithic pottery remains excavated in Goytepe (Azerbaijan), a typical Shomutepe-Shulaveri culture settlement. Fifty-five pottery fragments, that were unearthed in the excavations of Goytepe during the 2009-2013 years, were investigated using Fourier Transform Infrared (FTIR) and micro-Raman spectroscopy. X-Ray Diffraction (XRD) was used as a complementary technique. The firing-temperature and -conditions were inferred from the mineral phases obtained from the vibrational spectra of the samples and were estimated to be between 600 degrees C and 750 degrees C in oxidizing atmosphere. As chemometrics, Principal Component Analysis (PCA) followed by Linear Discriminant Analysis (LDA), were applied to the FTIR spectral data, in order to examine the possible classification of those findings, and to extract the most discriminant features. Pottery fragments were identified and characterized, depending on the excavation levels, by PCA-LDA analysis.Publication The Meta and Para OH Substitution Effect on C-Phenyl-Nitrilimine Bond-Shift Isomers(Wiley-VCH Verlag GmbH, 2023) Ferreira, Gil A.; Nunes, Claudio M.; Jesus, A. J. Lopes; FAUSTO, RUIThe geometric and electronic structure of 1,3-dipolar species, in particular of nitrile imines, can be surprisingly intricate. A particular example is the C-phenyl-nitrilimine, which exists as two energy minima that constitute bond-shift isomers. To examine the effect of substituents in the phenyl ring, here we investigate the meta and para OH substituted derivatives. These two nitrile imines were generated in an argon matrix by UV-irradiation of 2H-tetrazole precursors and found to photoisomerize to carbodiimides via 1H-diazirines. The different effects of the OH substitution in meta and para positions on the bond-shift isomerism are rationalized with the support of Natural Resonance Theory and Hirshfeld atomic charges. The understanding of how substitution affects the structural characteristics of C-phenyl-nitrilimines, opens a door to modulate the chemistry of those compounds (e. g. in cycloaddition reactions) by appropriate tuning of their substitution (substituent type and position).Publication Molecular and Crystal Structure, Spectroscopy, and Photochemistry of a Dispiro Compound Bearing the Tetraoxane Pharmacophore(Wiley-VCH Verlag GmbH, 2023) Amado, Patricia S. M.; Lopes, Susy; Bras, Elisa M.; Paixao, Jose A.; Takano, Ma-aya; Abe, Manabu; FAUSTO, RUI; Cristiano, Maria L. S.The molecular structure and photochemistry of dispiro[cyclohexane-1,3 & PRIME;-[1,2,4,5]tetraoxane-6 & PRIME;,2 & PRIME;& PRIME;-tricyclo[3.3.1.1(3,7)]decan]-4-one (TX), an antiparasitic 1,2,4,5-tetraoxane was investigated using matrix isolation IR and EPR spectroscopies, together with quantum chemical calculations undertaken at the DFT(B3LYP)/6-311++G(3df,3pd) level of theory, with and without Grimme's dispersion correction. Photolysis of the matrix-isolated TX, induced by in situ broadband (& lambda;>235 nm) or narrowband (& lambda; in the range 220-263 nm) irradiation, led to new bands in the infrared spectrum that could be ascribed to two distinct photoproducts, oxepane-2,5-dione, and 4-oxohomoadamantan-5-one. Our studies show that these photoproducts result from initial photoinduced cleavage of an O-O bond, with the formation of an oxygen-centered diradical that regioselectivity rearranges to a more stable (secondary carbon-centered)/(oxygen-centered) diradical, yielding the final products. Formation of the diradical species was confirmed by EPR measurements, upon photolysis of the compound at & lambda;=266 nm, in acetonitrile ice (T=10-80 K). Single-crystal X-ray diffraction (XRD) studies demonstrated that the TX molecule adopts nearly the same conformation in the crystal and matrix-isolation conditions, revealing that the intermolecular interactions in the TX crystal are weak. This result is in keeping with observed similarities between the infrared spectrum of the crystalline material and that of matrix-isolated TX. The detailed structural, vibrational, and photochemical data reported here appear relevant to the practical uses of TX in medicinal chemistry, considering its efficient and broad parasiticidal properties.Publication Nanoscale Study of the Polar and Electronic Properties of a Molecular Erbium(III) Complex Observed via Scanning Probe Microscopy(MDPI, 2023) Ivanov, Maxim; Grempka, Arkadiusz; Buryakov, Arseniy; Nikitin, Timur; Justino, Licinia L. G.; FAUSTO, RUI; Vilarinho, Paula M.; Paixao, Jose A.We successfully synthesized millimeter-sized single crystals of the molecular erbium(III) complex Er(acac)(3)(cphen), where acac = acetylacetonate and cphen = 5-chloro-1,10-phenanthroline. The novelty of this work stems from the exhaustive examination of the polar and electronic properties of the obtained samples at the macro-, micro-, and nanoscale levels. The single crystal X-ray diffraction method demonstrates the monoclinic (noncentrosymmetric space group P2(1)) crystallographic structure of the synthesized samples and scanning electron microscopy exhibits the terrace-ledge morphology of the surface in erbium(III) crystals. By using the piezoelectric force microscopy mode, the origin of the polar properties and the hyperpolarizability in the synthesized samples were assigned to the internal domain structure framed by the characteristic terrace-ledge topography. The direct piezoelectric coefficient (similar to d33) was found to be intensely dependent on the local area and was measured in the range of 4-8 pm/V. A nanoscale study using the kelvin probe force and capacitance force (dC/dz) microscopy modes exposed the effect of the Er ions clustering in the erbium(III) complex. The PFM method applied solely to the Er ion revealed the corresponding direct piezoelectric coefficient (similar to d33) of about 4 pm/V. Given the maximum piezoelectric coefficient in the erbium(III) complex at 8 pm/V, we highlight the significant importance of the spatial coordination between the lanthanide ion and the ligands. The polar coordination between the lanthanide ion and the nitrogen and oxygen atoms was also corroborated by Raman spectroscopy supported by the density functional theory calculations. The obtained results can be of paramount importance for the application of molecular erbium(III) complex crystals in low-magnitude magnetic or electric field devices, which would reduce the energy consumption and speed up the processing switching in nonvolatile memory devices.Publication Sandwich-Type Double-Layer Piezoelectric Nanogenerators Based on One- and Two-Dimensional ZnO Nanostructures With Improved Output Performance(Nature Research, 2023) Fakhri, Parisa; Eaianli, Naeimeh; Bagherzadeh, Roohollah; Jaleh, Babak; Kashfi, Mohammad; FAUSTO, RUIPiezoelectric nanogenerators (PENGs) have attracted great interest owing to their broad range application in environmental mechanical energy harvesting to power small electronic devices. In this study, novel flexible and high-performance double-layer sandwich-type PENGs based on one-dimensional (1-D) and two-dimensional (2-D) zinc oxide (ZnO) nanostructures and Ni foam as the middle layer have been developed. The morphology and structure of 1- and 2-D ZnO nanostructures have been studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). To investigate the effect of structural design on the piezoelectric performance, single-layer PENGs were also fabricated. The piezoelectric output of all prepared PENGs were evaluated under different human impacts at various forces and frequencies. The double-layer designed PENGs showed a two times larger voltage output compared to the single-layer PENGs, and the use of Ni foam as middle-layer and of 2-D ZnO nanosheets (compared to 1-D nanorods) was also found to increase the performance of the designed PENGs. The working mechanism of the prepared PENGs is also discussed. The design of nanogenerators as double-layer sandwich structures instead of two integrated single-layer devices reduces the overall preparation time and processing steps and enhances their output performance, thus opening the gate for widening their practical applications.Publication Solid-Liquid Phase Equilibrium: Alkane Systems for Low-Temperature Energy Storage(Springer/Plenum Publishers, 2024) Sequeira, Maria C. M.; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio P.; Fareleira, Joao M. N. A.; FAUSTO, RUIThe thermal characterization of two binary systems of n-alkanes that can be used as Phase Change Materials (PCMs) for thermal energy storage at low temperatures is reported in this work. The construction of the solid-liquid binary phase diagrams was achieved using differential scanning calorimetry (DSC) and Raman spectroscopy. The solidus and liquidus equilibrium temperatures were determined using DSC for thirty-nine different samples, three for the pure n-alkanes and the remaining for binary mixtures at selected molar compositions and used to acquire the corresponding solid-liquid phase diagrams. The two binary systems of n-octane/n-decane (C8/C10) and n-decane/n-dodecane (C10/C12) are characterized by a eutectic behavior at low temperatures. The eutectic temperature for the system C8/C10 was found at 211.95 K and the eutectic composition appeared at the molar fraction xoctane = 0.87. For the system C10/C12, the eutectic temperature was found at 237.85 K, and the eutectic composition appeared for the molar fraction xdecane = 0.78. This work aims to fulfill the lack of available data in the existing literature, considering the potential application of these systems for low-temperature thermal energy storage. Raman spectroscopy was used to complement the DSC data for the construction of the solid-liquid phase equilibrium diagrams, enabling the identification of the solid and liquid phases of the system. Additionally, the liquidus curve of the phase diagram was successfully described using a modified freezing point depression curve as fitting equation, the absolute root mean square deviation for the data correlation of the C8/C10 and C10/C12 systems being 2.56 K and 1.22 K, respectively. Ultimately, the fitting procedure also enabled a good prediction of the eutectic point for both studied systems.