F. Salehli - Academia.edu (original) (raw)
Papers by F. Salehli
Journal of Applied Polymer Science, 2000
Until the gel point, the length scale within the system is determined by the largest clusters. It... more Until the gel point, the length scale within the system is determined by the largest clusters. It increases with time and diverges at the gel point. At this point there is no length scale. Beyond the gel point, the length scale is determined by the size of the voids and the length of unattached ...
Crystals, 2020
Diphenylalanine microtubes have remarkable physical properties that allow one to use them in elec... more Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature changes were minimal, which required a significant improvement in the resolution and stability of Raman measurements. The anomalies in the behaviour of the spectra at about 178 K, 235 K, 255 K, 278 K, 296 K, 398 K and 412 K were observed. The structural phase transition at 398 K is irreversible. This transition is associated with the release of water molecules from nanochannels. The irreversible phase transition has a temperature range of about 10 K.
Journal of Physics-condensed Matter, 2008
Dielectric spectroscopy of liquid crystalline cyanobiphenyl polyacrylates (CBPA6) with six methyl... more Dielectric spectroscopy of liquid crystalline cyanobiphenyl polyacrylates (CBPA6) with six methylene groups in the side chain has been investigated in the frequency range of 30 Hz-13 MHz and in the temperature interval from 100 to 470 K. From the temperature dependence of ε'(T), the anomalies corresponding to sequential phase transitions of liquid crystalline mesophases were revealed. The observed alpha- and
Materials & Design
In this work we report macroscopic integration of reduced graphene oxide decorated by nickel nano... more In this work we report macroscopic integration of reduced graphene oxide decorated by nickel nanoparticles (rGO/Ni) with self-assembled diphenylalanine (FF) peptide microtubes (PMTs). The rGO/Ni nanocomposite forms planar electrode-like structure on the FF PMT surface and improves its mechanical and physical characteristics, as evidenced by the electron and scanning probe microscopy techniques. In particular, the enhancement of helical structural stability and stiffness of PMTs in the presence of rGO/Ni has been found. The interaction between rGO/Ni and FF PMTs modifies electromechanical properties of the microtubes, so that a large radial piezoresponse untypical of the pristine FF PMTs appears. Furthermore, the introduction of rGO/Ni enhances electrical conductivity of FF PMTs. The energy diagram of the PMT/rGO/Ni structure suggests an easy path for the optical conversion and light energy harvesting. The technical approach considered in this work opens up a new
Applied Physics Letters, 2016
The natural ability of peptides and proteins to self-assemble into elongated fibrils is associate... more The natural ability of peptides and proteins to self-assemble into elongated fibrils is associated with several neurogenerative diseases. Diphenylalanine (FF) tubular structures that have the same structural motif as in Ab-amyloid peptide (involved in Alzheimer's disease) are shown to possess remarkable physical properties ranging from piezoelectricity to electrochemical activities. In this work, we also discover a significant pyroelectric activity and measure the temperature dependence of the pyroelectric coefficient in the temperature range of 20 100 C. Pyroelectric activity decreases with temperature contrary to most ferroelectric materials and significant relaxation of pyrocurrent is observed on cooling after heating above 50 C. This unusual behavior is assigned to the temperature-induced disorder of water molecules inside the nanochannels. Pyroelectric coefficient and current and voltage figures of merit are estimated and future applications of pyroelectric peptide nanostructures in biomedical applications are outlined. Published by AIP Publishing.
Journal of Non-Crystalline Solids, 2007
Clear evidence of the existence of fractional kinetics containing the complex power-law exponents... more Clear evidence of the existence of fractional kinetics containing the complex power-law exponents were obtained by conductivity measurements of polymerization reaction of polyvinylpyrrolidone (PVP) performed inside a dielectric cell. We established the relationship between the Fourier image R(jx) of the complex memory function K(t) and the time-dependent mean square displacement hr 2 (t)i. This relationship helps to understand the origin of the different power-law exponents appearing in the real part of complex conductivity Re[r(x)] and find a physical/geometrical meaning of the power-law exponents that can form the complex-conjugated values. The complex-conjugated values of the power-law exponents leading to oscillating behavior of conductivity follows from the fractional kinetics suggested by one of the authors (R.R.N.). The relationships [R(jx) () Re[r(x)] () hr 2 (t)i] are becoming very efficient in classification of different types of collective motions belonging to light and heavy carriers involved in the relaxation/transfer process. The conductivity data obtained for Re[r(x)] during the whole polymerization process of the PVP at different temperatures (80, 90, 100°C) are very well described by the fitting function that follows from the suggested theory. Original fitting procedure based on the application of the eigencoordinates (ECs) method helps to provide a reliable fitting procedure in two stages and use the well-developed and statistically stable linear least square method (LLSM) for obtaining the correct values of the fitting parameters that describe the behavior of Re[r(x, T r)] in the available frequency range for the current time of the chemical reaction T r measured during the whole process of polymerization. The suggested theory gives a unique possibility to classify the basic types of motions that take place during the whole polymerization process.
Physics of The Solid State, 2009
The temperature dependences of the permittivity of TlInS2(1 −x)Se2x solid solutions have been exp... more The temperature dependences of the permittivity of TlInS2(1 −x)Se2x solid solutions have been experimentally investigated in the temperature range including the points of structural phase transitions in the solid solutions. It has been established that the isovalent substitution of selenium for sulfur in the anion sublattice of the TlInS2(1 − x)Se2x solid solutions shifts the phase transition temperatures T i
Journal of Non-crystalline Solids, 2007
Real time dielectric spectroscopy was used for monitoring the dynamics during liquid glass transi... more Real time dielectric spectroscopy was used for monitoring the dynamics during liquid glass transition in radical bulk polymerization of n-vinyl pyrrolidone. Two different relaxation mechanisms were identified. Initially segmental α-relaxation was dominant. Subsequently, contribution from slower motions became more significant and ε′(tr,ω) underwent maxima in all frequency bands up to 10MHz. Peak amplitude increased and the occurring time was delayed
The Journal of Chemical Physics, 2006
Dielectric spectroscopy measurements of conductivity were applied for understanding the change in... more Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide ͑PAAm͒ hydrogels during the swelling process. For the first time four distinct peaks ͑each corresponding to a different swelling stage͒ in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions ͑they are defined as the "blobs"͒ appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent SO 3 − groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re͓͔͑͒ by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re͓͑ , m / m 0 ͔͒ in the available frequency range ͑30 Hz-13 MHz͒ and for all values of the relative masses ͑volumes͒ measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels.
Polymer, 2010
We have performed a dielectric spectroscopy study of four homologous cyanobiphenyl polyacrylates ... more We have performed a dielectric spectroscopy study of four homologous cyanobiphenyl polyacrylates with long side chains. The aand d-relaxation times were found to be sensitive to the sequential transformations between mesophases. The s d in the isotropic phase exhibits the characteristics that obeys VFT relation and depend strongly on spacer length. The relaxation times, s d , for the crossover from short range intermolecular interactions to long range LC ordering, decreases with increasing side chain length, implying that the cooperative motions of mesogenic dipoles arrange long range order at shorter time scales, as the spacer length is increased. In the SmA mesophases of CBPAn compounds with n ¼ 8, 9
Physics of the Solid State, 2009
The experimental data on memory effects in an incommensurate phase are analyzed both in undoped l... more The experimental data on memory effects in an incommensurate phase are analyzed both in undoped layered TlInS 2 crystals selected from different technological batches and in TlInS 2 : La. Various types of unusual memory effect are detected. It is shown that the observed memory effects are due to pinning of the soliton superstructure by a defect density wave in the internal field of the electret state.
Physica B: Condensed Matter, 2007
The theoretical generalization of the Jonscher's relationship for the complex conductivity of car... more The theoretical generalization of the Jonscher's relationship for the complex conductivity of carriers moving in self-similar medium is derived. It is shown that the correction derived enters to more general expression, which, in turn, we define as the generalized Jonscher's relationship. The basic idea which was used for the derivation of the relationship is based on the supposition that disordered medium has self-similar property. The derived relationship is confirmed on dielectric spectroscopy data related to sodium nitrite embedded to porous glasses. Based on new relationship there is a possibility to extract additional information about relaxation processes of a system of dipoles from the processes related to conductivity. It is important in the cases when the contribution to relaxation peaks is small and unnoticeable on the background of essential domination of processes related to conductivity.
Journal of Non-Crystalline Solids, 2002
Ethyl methacrylate, ethylene glycol dimethacrylate free radical crosslinking co-polymerization re... more Ethyl methacrylate, ethylene glycol dimethacrylate free radical crosslinking co-polymerization reaction is studied by dielectric spectroscopy at various temperatures. A maximum in the dielectric constant was observed during the gelation reaction. At the same point, the dielectric loss switched from a linear decrease to a relatively constant behavior. Parallel experiments, performed with a magnetic stirrer, showed that this maximum is consistent with the gel-point. In the ethyl methacrylate homopolymerization reactions the dielectric constant did not go through a maximum but decreased monotonically. The evolution of the dielectric constant is found to depend on the extent of the reaction, but not on time and temperature separately. Ó
The Journal of Chemical Physics, 2006
Dielectric spectroscopy measurements of conductivity were applied for understanding the change in... more Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide ͑PAAm͒ hydrogels during the swelling process. For the first time four distinct peaks ͑each corresponding to a different swelling stage͒ in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions ͑they are defined as the "blobs"͒ appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent SO 3 − groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies.
Journal of Applied Polymer Science, 2000
Until the gel point, the length scale within the system is determined by the largest clusters. It... more Until the gel point, the length scale within the system is determined by the largest clusters. It increases with time and diverges at the gel point. At this point there is no length scale. Beyond the gel point, the length scale is determined by the size of the voids and the length of unattached ...
Journal of Applied Polymer Science, 2000
Until the gel point, the length scale within the system is determined by the largest clusters. It... more Until the gel point, the length scale within the system is determined by the largest clusters. It increases with time and diverges at the gel point. At this point there is no length scale. Beyond the gel point, the length scale is determined by the size of the voids and the length of unattached ...
Crystals, 2020
Diphenylalanine microtubes have remarkable physical properties that allow one to use them in elec... more Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature changes were minimal, which required a significant improvement in the resolution and stability of Raman measurements. The anomalies in the behaviour of the spectra at about 178 K, 235 K, 255 K, 278 K, 296 K, 398 K and 412 K were observed. The structural phase transition at 398 K is irreversible. This transition is associated with the release of water molecules from nanochannels. The irreversible phase transition has a temperature range of about 10 K.
Journal of Physics-condensed Matter, 2008
Dielectric spectroscopy of liquid crystalline cyanobiphenyl polyacrylates (CBPA6) with six methyl... more Dielectric spectroscopy of liquid crystalline cyanobiphenyl polyacrylates (CBPA6) with six methylene groups in the side chain has been investigated in the frequency range of 30 Hz-13 MHz and in the temperature interval from 100 to 470 K. From the temperature dependence of ε'(T), the anomalies corresponding to sequential phase transitions of liquid crystalline mesophases were revealed. The observed alpha- and
Materials & Design
In this work we report macroscopic integration of reduced graphene oxide decorated by nickel nano... more In this work we report macroscopic integration of reduced graphene oxide decorated by nickel nanoparticles (rGO/Ni) with self-assembled diphenylalanine (FF) peptide microtubes (PMTs). The rGO/Ni nanocomposite forms planar electrode-like structure on the FF PMT surface and improves its mechanical and physical characteristics, as evidenced by the electron and scanning probe microscopy techniques. In particular, the enhancement of helical structural stability and stiffness of PMTs in the presence of rGO/Ni has been found. The interaction between rGO/Ni and FF PMTs modifies electromechanical properties of the microtubes, so that a large radial piezoresponse untypical of the pristine FF PMTs appears. Furthermore, the introduction of rGO/Ni enhances electrical conductivity of FF PMTs. The energy diagram of the PMT/rGO/Ni structure suggests an easy path for the optical conversion and light energy harvesting. The technical approach considered in this work opens up a new
Applied Physics Letters, 2016
The natural ability of peptides and proteins to self-assemble into elongated fibrils is associate... more The natural ability of peptides and proteins to self-assemble into elongated fibrils is associated with several neurogenerative diseases. Diphenylalanine (FF) tubular structures that have the same structural motif as in Ab-amyloid peptide (involved in Alzheimer's disease) are shown to possess remarkable physical properties ranging from piezoelectricity to electrochemical activities. In this work, we also discover a significant pyroelectric activity and measure the temperature dependence of the pyroelectric coefficient in the temperature range of 20 100 C. Pyroelectric activity decreases with temperature contrary to most ferroelectric materials and significant relaxation of pyrocurrent is observed on cooling after heating above 50 C. This unusual behavior is assigned to the temperature-induced disorder of water molecules inside the nanochannels. Pyroelectric coefficient and current and voltage figures of merit are estimated and future applications of pyroelectric peptide nanostructures in biomedical applications are outlined. Published by AIP Publishing.
Journal of Non-Crystalline Solids, 2007
Clear evidence of the existence of fractional kinetics containing the complex power-law exponents... more Clear evidence of the existence of fractional kinetics containing the complex power-law exponents were obtained by conductivity measurements of polymerization reaction of polyvinylpyrrolidone (PVP) performed inside a dielectric cell. We established the relationship between the Fourier image R(jx) of the complex memory function K(t) and the time-dependent mean square displacement hr 2 (t)i. This relationship helps to understand the origin of the different power-law exponents appearing in the real part of complex conductivity Re[r(x)] and find a physical/geometrical meaning of the power-law exponents that can form the complex-conjugated values. The complex-conjugated values of the power-law exponents leading to oscillating behavior of conductivity follows from the fractional kinetics suggested by one of the authors (R.R.N.). The relationships [R(jx) () Re[r(x)] () hr 2 (t)i] are becoming very efficient in classification of different types of collective motions belonging to light and heavy carriers involved in the relaxation/transfer process. The conductivity data obtained for Re[r(x)] during the whole polymerization process of the PVP at different temperatures (80, 90, 100°C) are very well described by the fitting function that follows from the suggested theory. Original fitting procedure based on the application of the eigencoordinates (ECs) method helps to provide a reliable fitting procedure in two stages and use the well-developed and statistically stable linear least square method (LLSM) for obtaining the correct values of the fitting parameters that describe the behavior of Re[r(x, T r)] in the available frequency range for the current time of the chemical reaction T r measured during the whole process of polymerization. The suggested theory gives a unique possibility to classify the basic types of motions that take place during the whole polymerization process.
Physics of The Solid State, 2009
The temperature dependences of the permittivity of TlInS2(1 −x)Se2x solid solutions have been exp... more The temperature dependences of the permittivity of TlInS2(1 −x)Se2x solid solutions have been experimentally investigated in the temperature range including the points of structural phase transitions in the solid solutions. It has been established that the isovalent substitution of selenium for sulfur in the anion sublattice of the TlInS2(1 − x)Se2x solid solutions shifts the phase transition temperatures T i
Journal of Non-crystalline Solids, 2007
Real time dielectric spectroscopy was used for monitoring the dynamics during liquid glass transi... more Real time dielectric spectroscopy was used for monitoring the dynamics during liquid glass transition in radical bulk polymerization of n-vinyl pyrrolidone. Two different relaxation mechanisms were identified. Initially segmental α-relaxation was dominant. Subsequently, contribution from slower motions became more significant and ε′(tr,ω) underwent maxima in all frequency bands up to 10MHz. Peak amplitude increased and the occurring time was delayed
The Journal of Chemical Physics, 2006
Dielectric spectroscopy measurements of conductivity were applied for understanding the change in... more Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide ͑PAAm͒ hydrogels during the swelling process. For the first time four distinct peaks ͑each corresponding to a different swelling stage͒ in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions ͑they are defined as the "blobs"͒ appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent SO 3 − groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re͓͔͑͒ by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re͓͑ , m / m 0 ͔͒ in the available frequency range ͑30 Hz-13 MHz͒ and for all values of the relative masses ͑volumes͒ measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels.
Polymer, 2010
We have performed a dielectric spectroscopy study of four homologous cyanobiphenyl polyacrylates ... more We have performed a dielectric spectroscopy study of four homologous cyanobiphenyl polyacrylates with long side chains. The aand d-relaxation times were found to be sensitive to the sequential transformations between mesophases. The s d in the isotropic phase exhibits the characteristics that obeys VFT relation and depend strongly on spacer length. The relaxation times, s d , for the crossover from short range intermolecular interactions to long range LC ordering, decreases with increasing side chain length, implying that the cooperative motions of mesogenic dipoles arrange long range order at shorter time scales, as the spacer length is increased. In the SmA mesophases of CBPAn compounds with n ¼ 8, 9
Physics of the Solid State, 2009
The experimental data on memory effects in an incommensurate phase are analyzed both in undoped l... more The experimental data on memory effects in an incommensurate phase are analyzed both in undoped layered TlInS 2 crystals selected from different technological batches and in TlInS 2 : La. Various types of unusual memory effect are detected. It is shown that the observed memory effects are due to pinning of the soliton superstructure by a defect density wave in the internal field of the electret state.
Physica B: Condensed Matter, 2007
The theoretical generalization of the Jonscher's relationship for the complex conductivity of car... more The theoretical generalization of the Jonscher's relationship for the complex conductivity of carriers moving in self-similar medium is derived. It is shown that the correction derived enters to more general expression, which, in turn, we define as the generalized Jonscher's relationship. The basic idea which was used for the derivation of the relationship is based on the supposition that disordered medium has self-similar property. The derived relationship is confirmed on dielectric spectroscopy data related to sodium nitrite embedded to porous glasses. Based on new relationship there is a possibility to extract additional information about relaxation processes of a system of dipoles from the processes related to conductivity. It is important in the cases when the contribution to relaxation peaks is small and unnoticeable on the background of essential domination of processes related to conductivity.
Journal of Non-Crystalline Solids, 2002
Ethyl methacrylate, ethylene glycol dimethacrylate free radical crosslinking co-polymerization re... more Ethyl methacrylate, ethylene glycol dimethacrylate free radical crosslinking co-polymerization reaction is studied by dielectric spectroscopy at various temperatures. A maximum in the dielectric constant was observed during the gelation reaction. At the same point, the dielectric loss switched from a linear decrease to a relatively constant behavior. Parallel experiments, performed with a magnetic stirrer, showed that this maximum is consistent with the gel-point. In the ethyl methacrylate homopolymerization reactions the dielectric constant did not go through a maximum but decreased monotonically. The evolution of the dielectric constant is found to depend on the extent of the reaction, but not on time and temperature separately. Ó
The Journal of Chemical Physics, 2006
Dielectric spectroscopy measurements of conductivity were applied for understanding the change in... more Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide ͑PAAm͒ hydrogels during the swelling process. For the first time four distinct peaks ͑each corresponding to a different swelling stage͒ in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions ͑they are defined as the "blobs"͒ appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent SO 3 − groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies.
Journal of Applied Polymer Science, 2000
Until the gel point, the length scale within the system is determined by the largest clusters. It... more Until the gel point, the length scale within the system is determined by the largest clusters. It increases with time and diverges at the gel point. At this point there is no length scale. Beyond the gel point, the length scale is determined by the size of the voids and the length of unattached ...