| 1. |
- Andersson, Per, et al.
(författare)
-
Thermal conductivity, heat capacity and phase diagrams of the trichloroethanes under pressure : II. 1,1,2-trichloroethane
- 1981
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 69:1-2, s. 157-166
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity, λ, the heat capacity per unit volume, ρcp, and the phase diagram of 1,1,2-trichloroethane have been investigated in the temperature range 115 to 300 K and at pressures up to 2.5 GPa. The transient hot-wite method was used for the simultaneous measurement of λ and ρcp. Only solid phases I and II were detected, in agreement with the known phase diagram. A phase I-II transition was detected at about 200K and 0.1 GPa, which are conditions under which it had not priviously been observed. It was doubtful whether phase I could be retained metastably to low temperatures at low pressures with the most rapid cooling rate we were able to employ. The thermal resistivity of phase I was proportioned to temperature. The thermal resistivity of phase II contained an additional constant term, which we inferred to be a residual contribution associated with static structural imperfection in this phase.
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| 2. |
- Basavoju, Srinivas, et al.
(författare)
-
Pharmaceutical salts of fluoroquinolone antibacterial drugs with acesulfame sweetener
- 2012
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 562:1, s. 254-264
-
Tidskriftsartikel (refereegranskat)abstract
- Novel organic salts of norfloxacin and ciprofloxacin with artificial sweeteners such as saccharin and acesulfame were prepared. The two salts 1 and 2 were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Finally, the crystal structures were solved by single crystal X-ray diffraction data and the structures were analyzed in terms of supramolecular synthons. In norfloxacin acesulfamate 1, two norfloxacin cations and two acesulfame anions form an eight membered cyclic tetramer supramolecular synthon. The salt, ciprofloxacin acesulfamate 2, has a similar structure as salt 1. This study contributes the importance of crystal engineering and supramolecular chemistry to the pharmaceutical applications in terms of interactions and structural correlations in the design of new solid phases. Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.
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| 3. |
- Caillaud, B., et al.
(författare)
-
Safe and ergonomic welding masks by fast liquid crystals
- 2008
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1563-5287 .- 1542-1406. ; 494, s. 195-204
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments in welding technology, in particular the high intensity pulsed welding arc, have sharpened the requirements on speed and adjustable attenuation for safe and ergonomic operations. With this advent the conventional welding helmets based on nematic liquid crystals are facing difficulties because the nematics are not responding fast enough to stroboscopically follow the changing intensity of the arc during pulsed welding. We propose here a new generation of welding shutters based on smectic (ferroelectric or antiferroelectric) liquid crystals which are fast enough to be synchronized to follow pulsed arc regimes and hence permitting a better visibility of the object under work. The two varieties of smectic materials used are polymer-stabilized in order to make the device shock-proof, to prevent the formation of specific defects such as stripes and chevrons, and to reduce the back-relaxation time in the antiferroelectric case.
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| 4. |
- Cifelli, M., et al.
(författare)
-
NMR investigation of a thermotropic liquid crystal showing isotropic-isotropic'-(columnar)-cubic phase transitions
- 2017
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor and Francis Inc.. - 1542-1406 .- 1563-5287. ; 649:1, s. 20-30
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we report a first detailed study of the mesophasic behaviour of the calamitic liquid crystal, a (4,4′-bis(4″-carboxybelzyloxy)biphenyl derivate, labelled 9/2 RS/RS, showing an isotropic-isotropic-(columnar)-cubic phase behaviour on cooling. 1H NMR diffusometry allowed to distinguish between the two isotropic phases in terms of diffusion characterized by different Arrhenius activation energy, while 13C NMR static measurements and 2H NMR investigations were of help in understanding the orientational ordering properties of the metastable columnar phase and confirmed the isotropic state of the sample in the cubic phase.
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| 5. |
- Cifelli, M., et al.
(författare)
-
Study of Translational Diffusion Anisotropy of Ionic Smectogens by NMR Diffusometry
- 2015
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 614:1, s. 30-38
-
Tidskriftsartikel (refereegranskat)abstract
- Thermotropic ionic liquid crystals are considered very promising for a wide range of applications, such as anisotropic conductors as well as electrolytes in dye-synthesized solar cells. Their potential comes from the unique combination of ionic conductivity and high polarizability. In this paper we present a study of the diffusional properties of the ionic smectic A phase formed by the cationic smectogen, N-docecyl-N'-methyl-imidazolium (C12mim), with two different counter ions. Experimental translational diffusion data measured by NMR diffusometry are collected both for cations and anions and discussed in terms of their different anisotropy.
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| 6. |
- Dannetun, Per, et al.
(författare)
-
New Results on Metal-Polymer Interfaces
- 1993
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Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287. ; 228:1, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- New results on studies of the early stages of formation of the aluminum-poly(p-phenylenevinylene) interface are presented.
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| 7. |
- de Jong, Michel P, et al.
(författare)
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Ultraviolet photoelectron spectroscopy of polymers
- 2006
-
Ingår i: MOLECULAR CRYSTALS AND LIQUID CRYSTALS. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 455, s. 193-203
-
Tidskriftsartikel (refereegranskat)abstract
- During the past three decades, ultraviolet photoelectron spectroscopy of polymer films has evolved from a sort of appearance-potential ( valence band edge) measurement, into a tool for studying the full valence band region of thin polymer films, including insulating polymers, semiconducting polymers and electrically conducting polymers. Progress may be loosely divided into several categories: (A) the melding of thin polymer film technology with ultra high vacuum technology and the widespread use of helium resonance lamps for studies of solid surfaces, (B) the combined approach of measurements and appropriate theoretical-computational methods, and (C) the advent of synchrotron radiation resulting in multi-photon spectroscopies, nominally in the area of the near UV. A coincident discovery of electrically conducting polymers, and especially the evolution of applications of semiconducting polymers, added technologically driven emphasis to this development of UPS for polymer materials. This contribution traces a limited number of highlights in the evolution of UPS of polymers, from the '70' s through to 2005.
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| 8. |
- Fesenko, Olean, et al.
(författare)
-
Metal-graphene nanostructures for SEIRA spectroscopy
- 2020
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1563-5287 .- 1542-1406. ; 701:1, s. 106-117
-
Tidskriftsartikel (refereegranskat)abstract
- Infrared spectroscopy is widely used technique for observing bioorganic materials, but sometimes scientist have to work with small amount of investigated materials and infrared light interacts poorly with nanometric size molecules. Taking into account unique electro-optical properties of graphene and metal we demonstrated possibility to use metal-graphene nanostructures for label-free detection of thymine. It was shown that IR spectra of thymine adsorbed on the composite nanostructures, such as Au "nanostars" with graphene, is more enhanced than whenthese nanoparticles are used without graphene. The enhancement in IR absorption for complex thymine/Au/graphene depends on size of Au nanoparticlesand thymine's molecular group.
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| 9. |
- Filippelli, Luigi, et al.
(författare)
-
Metastability of Multi-Lamellar Vesicles in a Nonionic System
- 2009
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1543-5318 .- 1563-5287. ; 500, s. 166-181
-
Konferensbidrag (refereegranskat)abstract
- Nuclear magnetic resonance spectroscopy and rheological analysis have been used to investigate the stability of mechanically induced tri-ethylene-glycol-mono-n-decyl-ether (C10E3)/deuterium oxide (D2O) multi-lamellar vesicles (MLVs) and the transition from MLVs to planar lamellae. It was found that MLVs prepared by vortex stirring, relax back to the lamellar phase in a few hours while the relaxation of the shear induced MLVs takes days. Pulsed gradient spin echo and water self-diffusion coefficient experiments, revealed that the MLVs texture, obtained by vortex stirring, is composed of large size structures. These data indicate that the kinetics of lamellar re-formation depend on the MLVs number density.
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| 10. |
- Galli, G., et al.
(författare)
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Design of siloxane liquid crystals forming a de Vries SmA* phase
- 2005
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 439, s. 2111-2123
-
Tidskriftsartikel (refereegranskat)abstract
- We designed and synthesized new SmA* liquid crystals with different molecular architectures based on the chiral mesogen MR11, which was unsubstituted, or attached at one end and at both ends of a trisiloxane segment in the monosubstituted MSi3-MR11 and disubstituted DSi3-MR11 siloxanes, respectively. We studied the critical divergence of the magnetic susceptibility by measurements of the induced tilt angle theta(ind) at the SmA*-SmC* transition. While all three SmA* liquid crystals presented a de Vries character, this was quite distinctive for DSi3-MR11 for which the critical exponent gamma = 1.87 was maximal. X-ray diffraction experiments confirmed that the SmA*-SmC* transition occurred with essentially no layer shrinkage.
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| 11. |
- Gulbinas, V, et al.
(författare)
-
Nonlinear exciton relaxation in ladder-type poly (para-phenylene)
- 2007
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1543-5318 .- 1542-1406 .- 1563-5287. ; 467, s. 47-57
-
Tidskriftsartikel (refereegranskat)abstract
- Nonlinear exciton relaxation processes, exciton-exciton annihilation, and amplified spontaneous emission were investigated in thin films of ladder-type poly(para-phenylene) under excitation by femtosecond light pulses. Both processes become apparent at similar excitation intensities, however their properties are very different. They cause different exciton relaxation kinetics and their intensity dependences are different.
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| 12. |
- Hibner-Kulicka, Paulina, et al.
(författare)
-
Influence of P3HT preaggregation process on performance of the P3HT:C60-PCBM solar cells
- 2019
-
Ingår i: Molecular Crystals and Liquid Crystals. - : TAYLOR & FRANCIS LTD. - 1542-1406 .- 1563-5287. ; 693:1, s. 82-96
-
Tidskriftsartikel (refereegranskat)abstract
- The bulk heterojunction based created by poly(3-hexyltiophene-2,5-diyl) (P3HT phenyl-C61-butyric acid methyl ester (C60-PCBM) it is well-known system used in organic solar cells. As the performance of such solar cells are very sensitive to the processing conditions of the active layers, we have focused attention to preaggregation process of P3HT in the aged solutions, which can be one of the reasons behind the different values of the reported efficiencies for this solar cell system. In this work, we present a systematic study of the influence of aging time of solutions mixture of P3HT:C60-PCBM in different solvents on the performance of the photovoltaic cells. The highest efficiency values were obtained from devices based on active layer dissolved in 1,2-dichlorobenzene. These values were stable even after 120 h of aging solutions, which means that the solution ageing process does not affect the final device properties. While, in chloroform and toluene solvents, efficiency of solar cells decreases within aging process. Our processing approach allows to better understanding the relationship between morphology of P3HT:C60-PCBM layer and device performances.
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| 13. |
- Kim, Woo Sik, et al.
(författare)
-
Film Structure-Induced Resonant Oscillation Changes in a Poly Acrylic Acid Modified Quartz Crystal Sensor
- 2008
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 492, s. 221-228
-
Tidskriftsartikel (refereegranskat)abstract
- A poly acrylic acid (PAA) film has been fabricated on a quartz crystal microbalance to study the dynamic property changes induced by different pH values. The experiment has been performed by a two-step. First, using the self-assembly procedure, the gold surface of quartz crystal was chemically modified to allow the graft copolymerization with PAA. Secondly, the resonant frequency response of the PAA-modified QCM was investigated by varying the pH values. The result shows an interesting oscillation property change nearby pH 5.5, and a possible mechanism for the change is proposed considering the oscillation properties of quartz crystal and the physical properties of PAA. Finally, a polymer film complex of PAA/collagen was also used to confirm the proposed mechanism.
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| 14. |
- Komitov, Lachezar, 1944
(författare)
-
Molecular Shape Related Effects in Liquid Crystals
- 2015
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 608:1, s. 246-257
-
Tidskriftsartikel (refereegranskat)abstract
- Liquid crystals are organic materials constituting of molecules characterized by strong shape anisotropy. Many studies unambiguously showed that some important physical effects observed in liquid crystals are strongly dependent on the shape anisotropy of their molecules. In this talk, some of the molecular shape related effects in liquid crystals, which have a potential for applications in liquid crystal displays (LCDs) and photonic devices, was overviewed. Photo-induced alignment transition from planar to vertical, flexoelectric polarization in short pitch cholesteric liquid crystals, alignment of bent core nematics as well as field driven transition from birefringent to optically isotropic state in these materials are among those effects on which this talk was focused. The role of the molecular shape was discussed with focus on the impact, which it has on the anchoring, flexoelectric, optical and electro-optical properties of the liquid crystals.
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| 15. |
- Kunstelj, K, et al.
(författare)
-
Switching of Electrically Commanded Alignment Layers Probed by Optical Second Harmonic Generation
- 2006
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1563-5287 .- 1542-1406 .- 1058-7276. ; 450:1, s. 127/[327] - 139/[339]
-
Tidskriftsartikel (refereegranskat)abstract
- Optical second harmonic generation (SHG) was used to probe the response of a 200 nm thick electrically commanded alignment layer made of ferroelectric liquid crystal polymer (FLCP) film to an external DC electric field. The results show that for the field magnitudes in the range 0-2 V/ m the field induced reorientation effects represent only a relatively minor structural perturbation of the film. The switching process is monostable and shows characteristics of the "V-shaped" switching. The response time of the SHG signal is relatively longer than what is measured for the bulk FLCP. Several mechanisms are considered as possible reasons for that.
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| 16. |
- Lagerwall, Sven, 1934
(författare)
-
Linear and Non-Linear Polar Effects in Liquid Crystals
- 2011
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1563-5287 .- 1542-1406. ; 543, s. 3-47
-
Tidskriftsartikel (refereegranskat)abstract
- In cholesterics and chiral smectics there are linear electro-optic modes of considerable interest. As they are fast-switching and have a natural gray scale we will discuss their future potential, in general for active matrix addressing. In spite of differences in physical origin they are all dielectric effects (even in the smectic C* phase) and are generically related by symmetry. This leads to the common feature that there is only one time constant involved (not one oONo and another oOFFo as for effects related to dielectric anisotropy). Furthermore this time constant is independent on the applied electric field. We will also see that cholesterics and chiral smectics have more in common - but seldom pointed out - than just being chiral. In surface-stabilized tilted chiral smectics there are instead strongly non-linear effects one of which may achieve a more or less perfect memory (bistability). If, in addition, the liquid crystal is polymer-stabilized, the cell can be made monostable with a continuous gray scale. As the effects are very fast they were originally successfully developed for passive matrix addressing. Industrial interest in these modes (ferroelectric and antiferroelectric) declined, nevertheless, in the late 1990s. This was not because other types of liquid crystals had been discovered but rather because a cost-effective thin-film-transistor (TFT) technology had been developed. With a TFT matrix every liquid crystal pixel is addressed individually and needs neither to have memory nor to switch at higher speed than can be achieved with nematics. As, however, active-matrix addressing is now commonplace there is naturally a renewed interest in these modes, especially for the future transfer from displays with color filters to displays in which the full color is generated by modulating the red, green and blue LEDs in the time domain.
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| 17. |
- Lagerwall, Sven, 1934, et al.
(författare)
-
The Orientational order in So-Called de Vries Materials
- 2009
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1563-5287 .- 1542-1406. ; 510, s. 1282-1291
-
Tidskriftsartikel (refereegranskat)abstract
- There is a great interest in smectic materials that show no layer shrinkage (NLS) in the transition from smectic A to smectic C. Such materials are often discussed in terms of ode Vries materialso or ode Vries behavioro after A. de Vries, who proposed different mechanisms for this NLS behavior, involving a significant tilt of the individual molecules in the smectic A phase. According to the original proposition of de Vries, the molecules are already tilted in this kind of smectic A phase, with a large constant tilt and the same tilt direction in each layer but random tilt direction between different layers. Despite the individual molecular tilt the smectic A phase remains uniaxial and the transition to the biaxial smectic C state is seen as a global ordering in the tilt directions. The model thus ad hoc predicts that there is zero layer shrinkage at the A - C transition. We refer to this model as the ohollow cone distributiono. As later pointed out by de Vries there are, however, other possible models for describing a tilt disorder (thermodynamically unavoidable) in the A phase. Nevertheless, the hollow cone has been a widely accepted model in the literature and is repeatedly referred to in discussing de Vries behavior or even taken as a basis for theories describing it. We discuss different smectic A orientational distribution functions that could be related to de Vries behavior or de Vries transitions. We find that two opposite models have comparable predictive power but only one gives a consistent picture together with existing data. Our conclusion is that the smectic A - smectic C transition can have a continuously changing character from a opure tilto to a opure de Vrieso, and we illustrate the orientational distribution functions in the A and C phases for these two limiting cases. We find that de Vries behavior is not related to any exotic distribution of hollow cone or similar kind in the A phase, but instead to an unusual combination of low nematic order and high smectic order in the de Vries smectic A. As the technical interest in such materials is considerable, a directed effort toward the synthesis of new optimized materials would be important.
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| 18. |
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| 19. |
- Larsson-Brelid, P., et al.
(författare)
-
Ecobuild a center for development of fully biobased material systems and furniture applications
- 2008
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 484, s. 623-630
-
Tidskriftsartikel (refereegranskat)abstract
- There is a great incentive and motivation in the building and wood research communities as well as in the industry to develop more eco-efficient and durable wood-based products with better performances. In this context, eco-efficient products refer to "green" sustainable products where both economical and ecological aspects have to be balanced. This presentation will give the general strategies within the newly formed Swedish Institute Excellence Center, EcoBuild. The conceptual idea for this competence centre is a conversion of biomass into innovative, eco-efficient and durable wood based products. The vision is that EcoBuild will, through the formation of a university-institute-industry cooperation, act as an international leading innovation, research and technology development platform within the wood science and technology field. The research projects within the centre are guided by a group of about 30 industry partners and also by end-user demands (Fig. 1). Types of materials in focus are: modified solid wood such as heat treated, furfurylated and acetylated wood, biobased binders and coatings, and biocomposites. A top priority is to develop fully biobased products, i.e., all raw materials should preferably be biobased, including chemicals for modification, adhesives, and surface treatment. Aspects and initial results regarding some of the EcoBuild activities will also be presented. Examples of research projects already started are: 1) Novel bio-based board resins; 2) UV-resistant clear coatings for exterior use; 3) Highly durable WPCs for outdoor use based on modified wood particles; 4) Modification of hardwood for exterior applications; 5) Fundamental understanding of the mechanisms involved in the durability of modified wood.
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| 20. |
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| 21. |
- Nageeb, Mohamad, et al.
(författare)
-
Bone Engineering by Biomimetic Injectable Hydrogel
- 2012
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 555:1, s. 177-188
-
Tidskriftsartikel (refereegranskat)abstract
- Osteoporosis is a multifactorial bone disease characterized by low bone mineral density (BMD) and deterioration of micro-architecture of cancellous bone leading to bone fragility and risk of fractures. In the current work, a novel tissue engineering strategy was experimented to enhance bone architecture in the risk areas via local injection of a biomimetic/osteoinductive injectable hyaluronan based hydrogel loaded with nano-hydroxyapatite crystals (Hya/HA) with/without bone morphogenetic protein (BMP-2), in distal femur of normal and ovariectomized New Zealand white rabbits. Our results revealed the osteoinductive effect of the Hya/HA composite that enhanced bone density and architecture of the rabbit distal femur.
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| 22. |
- Pitsevich, G. A., et al.
(författare)
-
Some useful correlations for H-bonded systems
- 2020
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 696:1, s. 15-28
-
Tidskriftsartikel (refereegranskat)abstract
- Structure and spectral characteristics of eight compounds with hydrogen bonds of different strength were calculated at the B3LYP/cc-pVTZ level of theory. A wide range of variation of the hydrogen bond strength in the analyzed compounds allowed us to obtain correlation dependences between the structural characteristics of the hydrogen bridge, the calculated values of the frequencies of stretching vibrations of donor hydroxyl groups, the values of the force constants of hydroxyl and hydrogen bonds, and the dissociation energies of hydrogen bonds. The obtained correlations can be used to evaluate a number of characteristics in compounds with hydrogen bonds.
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| 23. |
- Pozhidaev, E. P., et al.
(författare)
-
Light Scattering of Short Helix Pitch Ferroelectric Liquid Crystal
- 2009
-
Ingår i: MOLECULAR CRYSTALS AND LIQUID CRYSTALS. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 510, s. 12-20
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Tidskriftsartikel (refereegranskat)abstract
- Two new light scattering modes have been discovered in short helix pitch (p0 ≅ 350 nm) ferroelectric liquid crystal (FLC). One of the modes arises because of a special kind of the FLC structure non-uniformity that originates inherently as a new phenomenon if the helix pitch is very small. Another mode relates to the helix twisting after the driving voltage switching off.
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| 24. |
- Ross, Russell G., et al.
(författare)
-
Thermal conductivity, heat capacity and phase diagram of tetrahydrofuran under pressure
- 1981
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 78:1, s. 35-40
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity, Λ, and the heat capacity per unit volume, pcp , have been measured for tetrahydrofuran (THF) using the transient hot-wire method in the temperature range 130-300 K and at pressures up to 2 GPa. Most of the data relate to the single solid phase which was found to exist over these ranges of the variables. The liquidus curve was determined roughly up to the maximum pressure, and we estimated the density of the solid phase at the normal melting point using the Clausius-Clapeyron relation. We inferred from the measurements that solid THF was a normal crystal phase in which three-phonon umklapp processes provided the only significant source of thermal resistivity. There was evidence for the effect of thermal expansion on Λ, and this effect decreased under pressure.
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| 25. |
- Ross, Russell G., et al.
(författare)
-
Thermal conductivity, heat capacity and phase diagrams of the trichloroethanes under pressure : I. 1,1,1-trichloroethane
- 1981
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 69:1-2, s. 145-156
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ, the heat capacity per unit volume ρcp, and the phase diagram of 1,1,1-trichloroethane have been investigated in the temperature range 115 to 350 K and at pressures up to 2 GPa. The Transient hot-wire method was used for the simultaneous measurement of λ and ρcp. Of the stable phases only Ib and II were detected, and not phases III and IV which had been reported in our range of measurement by some previous investigators. Furthermore, metastable phase Ia was roughly proportional to temperature. Such behaviour is consistent with regarding phase Ib as a plastic crystal phase and phase II as a normal crystal phase, which is in agreement with other work.
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| 26. |
- Shamsuddin, L., et al.
(författare)
-
Perovskite solar cells using polymer electrolytes
- 2017
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 655:1, s. 181-194
-
Tidskriftsartikel (refereegranskat)abstract
- This study deals with the characterization of methylammonium lead iodide (MAPbI3) material and the fabrication of perovskite solar cells using gel polymer electrolyte as the charge transport medium. The crystalline lead–based perovskite has been verified by x-ray diffraction (XRD). The [100], [200], [210], [211], [220], [300] and [222] reflection planes can be observed at 2θ angles of 14.10°, 28.35°, 31.90°, 34.95°, 40.40°, 43.15° and 50.20°, indicating a cubic crystal symmetry for CH3NH3PbI3. EDX spectrum showed a Pb:I ratio of approximately 1:3 as in CH3NH3PbI3. The band gap for lead-based perovskite is 1.45eV estimated from UV-Vis absorption spectroscopy. The nanocrystalline MAPbI3 have been observed using field emission scanning electron microscopy (FESEM), where the average cuboid size of perovskite nanocrystals is 380nm. The cell have been fabricated using gel polymer electrolyte with composition 17.02wt.% PVA–13.93wt.% TBAI–0.96wt.% I2– 68.09wt.% DMF. The cell exhibits a power conversion efficiency (PCE) of 1.28% with open circuit voltage (Voc) 0.58mV, short circuit current density (Jsc) 3.74mA cm−2 and fill factor (FF) 59.18%.
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| 27. |
- Solomenko, Anastasiia G., et al.
(författare)
-
Deformation-induced band gap variation in phosphorene: tight-binding model vs. first-principles simulations
- 2024
-
Ingår i: Molecular Crystals and Liquid Crystals. - : TAYLOR & FRANCIS LTD. - 1542-1406 .- 1563-5287.
-
Tidskriftsartikel (refereegranskat)abstract
- We focus on estimating the influences of uniaxial tensile and shear strains on a band gap in the electronic structure of monolayer black phosphorus. To study numerically the dependence of the band gap on the deformation type and strength, we apply two approaches: the tight-binding model (with the exponential and inversely quadratic strain-induced bond-length-dependent hoppings) and the density-functional-theory-based calculations. Both approaches corroborated that phosphorene as a direct semiconductor in the unstrained state can become a semimetal at certain types and strengths of deformations. The critical values of the semiconductor-semimetal transition are different depending on approximations and model parameters.
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| 28. |
- Viveka, Shivapura, et al.
(författare)
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Synthesis, characterization, single crystal X-ray diffraction and DFT studies of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate
- 2016
-
Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; , s. 135-145
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Tidskriftsartikel (refereegranskat)abstract
- The present study describes the synthesis, spectroscopic, and single crystal X-ray structural analysis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate. The pyrazole ester of formula [C13H14N2O2] was prepared from the three-component one-pot condensation reaction of ethyl acetoacetate, N,N-dimethyldimethoxymethanamine, and phenyl hydrazine. The product was crystallized by using ethanol as solvent. The structure of the compound was confirmed by elemental analysis, Fourier transforms infrared (IR), thermogravimetric analysis, UV-visible (UV-Vis), 1H NMR, and single-crystal X-ray diffraction studies. The gas-phase molecular geometry and the electronic structure-property of the molecule were calculated at the density functional theory. The frontier molecular orbitals, theoretical UV-Vis, and IR stretching vibrations were also reported. The compound crystallizes in the monoclinic system with the space group P21/c and Z = 4. The unit cell parameters are a = 12.141(3) Å, b = 13.934(4) Å, c = 7.2777(18) Å, and β = 97.816(14)0. The structure is stabilized by an intermolecular interaction of type C-H···O and the structure also involves C-H···π interactions
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| 29. |
- Wang, N., et al.
(författare)
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Topological capillarity in a phase separated liquid crystal system
- 2023
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Ingår i: Molecular Crystals and Liquid Crystals. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 757:1, s. 22-32
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Tidskriftsartikel (refereegranskat)abstract
- Emulsions of isotropic liquids have spherical phase boundaries. Liquid crystals have elastic forces associated with the director distortions and preferred boundary conditions that can also play a role in defining the phase boundary shape. Here we show a liquid crystal in liquid crystal emulsion where a chemically distinct guest phase resides in the topological disclinations of the host phase. These disclinations act as effective capillaries and various meniscus and droplet phenomena are observed. This “topological capillary emulsion” shows that additional forces associated with anisotropic molecules can play a critical role in determining the shape and properties of a phase boundary.
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| 30. |
- Wigren, J., et al.
(författare)
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Thermal conductivity and heat capacity of adamantane and hexamethylenetetramine under pressure
- 1980
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Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 59:1-2, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- We have used the transient hot-wire technique to measure simultaneously the thermal conductivity and the heat capacity per unit volume of solid adamantane and hexamethylenetetramine. Data were obtained over the temperature range 115 K to 445 K, and at pressures up to 2.5 GPa. The thermal conductivity of plastic crystalline adamantane is much less temperature dependent than those of normal crystalline adamantane and hexamethylenetetramine. The volume dependence of the thermal conductivity of plastic crystalline adamantane is considerably smaller than those of the normal crystalline phases, and thus more similar to that of a liquid. The molar heat capacities for the different phases and substances were found to change very little with pressure. We discuss the temperature and volume dependences of the thermal properties in relation to available theoretical models.
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| 31. |
- Yamane, H., et al.
(författare)
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Hole-vibration coupling in the uppermost valence band photoemission of pentacene monolayer on graphite
- 2006
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Ingår i: MOLECULAR CRYSTALS AND LIQUID CRYSTALS. - : Informa UK Limited. - 1542-1406 .- 1563-5287. ; 455, s. 235-240
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Tidskriftsartikel (refereegranskat)abstract
- The hole-vibration coupling of the highest occupied state in pentacene thin films on graphite was studied by high-resolution ultraviolet photoemission spectroscopy. It was found that vibration satellites in the film are more intense than that in the gas phase and the vibrational energy in the film is slightly lower than that in the gas phase. This demonstrates that the reorganization energy (hole mobility) in the pentacene thin film is slightly larger (smaller) than that expected from the photoemission spectrum of free pentacene molecules.
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| 32. |
- Kozachenko, Andriy, et al.
(författare)
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Influence of the surfaces on the nucleation process during the cholesteric –nematic transition
- 2004
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Ingår i: Mol.Cryst.Liq.Cryst.. - 1542-1406. ; 412
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Tidskriftsartikel (refereegranskat)abstract
- The nucleation phenomenon in short pitch cholesteric liquid crystals (LC), taking place during the relaxation from the electric field-induced cholesteric-nematic (CN) transition, has been investigated for various boundary conditions. The dynamic hysteresis properties have been studied by direct optical methods. For the first time it is shown the strong evidences that the nucleation is not exceptionally a bulk phenomenon and the supporting solid surfaces may act as nucleation sites. It is confirmed also that the nucleation velocity is not a function of the type of molecular alignment at the liquid crystal/solid interface rather than it depends on the uniformity of the surface interactions with liquid crystal molecules. This result is of importance for time scale optimization in modern fast driving schemes for cholesteric LCDs.
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