Supersolubility Curves Research Articles

Characterization of α-phenyl-4′-(diphenylamino)stilbene single crystal and its anisotropic conductivity

Presently, organic-semiconductor electronics suffer from low performance owing to their amorphous nature. Improving their crystallinity, and thus the charge transport properties is a crucial endeavor. Accordingly, this study aims to elucidate the conductivity mechanism of a novel triphenylamine-derivative single crystal. We successfully synthesized an α-phenyl-4′-(diphenylamino)stilbene (TPA) single crystal via a solution method employing the solubility and supersolubility curves of TPA in the tetrahydrofuran (THF) solvent. Its crystal structure was determined via single-crystal X-ray diffraction (SCXRD), which revealed that the obtained single crystal contains not only TPA but also THF. The molecular ratio of TPA to THF was found to be 2:0.74. We further analyzed the hole transport property in three directions of the single crystal, and the anisotropic conductivity was observed. Based on the results of the observed molecular packing and charge transport property, we confirm that the observed anisotropic conductivity is determined based on the orientation of the triphenylamine unit in each direction of the TPA single crystal. Overall, the findings can help in guiding the design of high-mobility organic semiconductors for realizing more effective organic electronic devices.

Hole Transport Property of α-phenyl-4'-(diphenylamino)stilbene Single Crystal Prepared Based on Solubility and Supersolubility Curves

Hole Transport Property of α-phenyl-4'-(diphenylamino)stilbene Single Crystal Prepared Based on Solubility and Supersolubility Curves

Crystal structure oriented carrier transport characteristic of triphenylamine derivative single crystal

Organic electronic materials used in organic photoreceptors for electrophotography are expected to be employed in many functional organic devices. Regarding the inferior mobility compared to inorganic semiconductors, in this study, an organic single crystal was prepared at a high rate and characterized. First, solubility and supersolubility curves of α-phenyl-4’-[(4-methoxyphenyl)phenylamino]stilbene (TPA) were measured. According to the data, the rapid crystal growth has been succeeded. Polarization microscope observation and XRD result confirmed that a single crystal is obtained. The results of a cyclic voltammogram and molecular orbital calculations showed that hole transport takes place in the crystal. On the surface of the obtained single crystal, Au parallel electrodes were vacuum deposited to measure its electric conductivity. Higher currents were observed on the long and short axes of the single crystal than that of the amorphous layer. Moreover, an anisotropic conductivity, in which the current in the long axis is greater than that in the short axes, was remarked. Consequently, the molecular stack of the crystal clarified by an XRD analysis and molecular electronic structure assessed by molecular orbital calculation well explain the anisotropic conductivity of the crystal.

Effect of Seed Loading and Temperature of Seeding on Carbamazepine-Saccharin Co-Crystal

Objectives: In pharmaceutical industries, the properties of desired final crystal can be modified by seeding process. Seeding activities depend on seed loading, seed size, seed quality and the temperature of supersaturated solution at the time of seed addition. The effect of amount of seed and temperature of seeding on crystallisation and size distribution of carbamazepine-saccharin (CBZ-SAC) co-crystals have been investigated. Methods/Statistical Analysis: 0.5, 1.0 and 1.5 wt% seeds of constant size were added to the metastable zone width region during cooling crystallisation at seeding temperatures of 38.45, 40.35, 42.25, 44.15 and 46.05 oC. Findings: During the crystallisation process of CBZ-SAC co-crystal, nucleation occurred faster when seeding is close to the super solubility curve which is at the highest supersaturation. Crystal size distribution (CSD) results showed more fine particles formed at 38.45oC seed temperature. On the other hand, nucleation occurred slower when seeding is close to the solubility curve, which is at low supersaturation and therefore resulted in less number of fine particles formed. Application: Nucleation of CBZ-SAC co-crystals can be controlled easily by seeding, in which the addition of seed expedites the crystallisation process by providing the surface area for crystals to grow. The size and characteristic of the desired crystal can be adjusted via seeding application.

Effect of Seed Loading and Temperature of Seeding on Carbamazepine-Saccharin Co-Crystal

Objectives: In pharmaceutical industries, the properties of desired final crystal can be modified by seeding process. Seeding activities depend on seed loading, seed size, seed quality and the temperature of supersaturated solution at the time of seed addition. The effect of amount of seed and temperature of seeding on crystallisation and size distribution of carbamazepine-saccharin (CBZ-SAC) co-crystals have been investigated. Methods/Statistical Analysis: 0.5, 1.0 and 1.5 wt% seeds of constant size were added to the metastable zone width region during cooling crystallisation at seeding temperatures of 38.45, 40.35, 42.25, 44.15 and 46.05 oC. Findings: During the crystallisation process of CBZ-SAC co-crystal, nucleation occurred faster when seeding is close to the super solubility curve which is at the highest supersaturation. Crystal size distribution (CSD) results showed more fine particles formed at 38.45oC seed temperature. On the other hand, nucleation occurred slower when seeding is close to the solubility curve, which is at low supersaturation and therefore resulted in less number of fine particles formed. Application: Nucleation of CBZ-SAC co-crystals can be controlled easily by seeding, in which the addition of seed expedites the crystallisation process by providing the surface area for crystals to grow. The size and characteristic of the desired crystal can be adjusted via seeding application.

Hole Transfer Property at Single Crystal Prepared from Triphenylamine-Derivative Based on Solubility and Supersolubility Curves

In this report, we describe anisotropic hole transport in a triphenylamine-derivative single crystal prepared by a solution method with solubility and supersolubility curves. Triphenylamine derivatives are commonly used as a hole-transport material for organic devices. In the electrophotographic photoconductors, the materials are used in an amorphous form, in which charge carrier mobility is in the order of ~104 cm2V-1s-1. For realizing a further high mobility as an organic semiconductor, preparation of a single crystal seems to be a promissing way. In this study, a single crystal of a trihenylamine derivative (TPA : α-Phenyl-4'-[(4-methoxyphenyl)phenylamino]stilbene) was prepared and its anisotropic hole transport property was measured. Firstly, solubility and supersolubility curves were measured employing a tetrahydrofuran (THF) as a solvent. Based on the results, a single crystal preparation was conducted using 45 wt.% TPA solution with a cooling rate of 0.125 °Ch-1 started from 35°C for 48 h, resulted in a crystal of 8 x 0.8 x 0.4 mm. A polarizing microscope observation demonstrated an extinction angle, which ensures that the TPA single crystal is obtained. Next, current-voltage properties of the TPA single crystal were measured in a vacuum chamber connected to a source meter (Keythley 2612A). For the measurement, A set of Au parallel electrodes with a distance of 20 μm were vacuum deposited on the crystal. From the results, long-axis (direction of 8 mm at TPA single crystal) current is larger than the short-axis (direction of 0.8 mm at TPA single crystal) current, which reveals anisotropic hole transport in the crystal is observed. This can be well explained by a molecular orientation of the crystal structure. Figure 1

Anisotropic surface hole-transport property of triphenylamine-derivative single crystal prepared by solution method

This paper reports the anisotropic hole transport at the triphenylamine-derivative single crystal surface prepared by a solution method. Triphenylamine derivatives are commonly used in a hole-transport material for organic photoconductors of laser-beam printers, in which the materials are used as an amorphous form. For developing organic photovoltaics using the photoconductor’s technology, preparation of a single crystal seems to be a specific way by realizing the high mobility of an organic semiconductor. In this study, a single crystal of 4-(2,2-diphenylethenyl)-N,N-bis(4-methylphenyl)-benzenamine (TPA) was prepared and its anisotropic hole-transport property measured. First, the hole-transport property of the TPA was investigated based on its chemical structure and electrochemical redox characteristics. Next, a large-scale single crystal formation at a high rate was developed by employing a solution method based on its solubility and supersolubility curves. The grown TPA was found to be a single crystal based on the polarization micrograph observation and crystallographic analysis. For the TPA single crystal, an anisotropic surface conduction was found, which was well explained by its molecular stack structure. The measured current in the long-axis direction is one order of magnitude greater than that of amorphous TPA.

The Role of Diastereomer Impurity in Oiling-Out during the Resolution of trans-4-Methyl-2-piperidine Carboxylic Ethyl Ester Enantiomers by Crystallization

Isolating enantiomers by crystallization via diastereomer salt formation is widely used in the pharmaceutical industry. Unfortunately, we found that, when some diastereomer impurity exists, oiling-out will take place and significantly decrease the resolution efficiency. To identify the role of impurities in oiling-out, three series of chiral resolution of trans-4-methyl-2-piperidine carboxylic ethyl ester (trans-4MPE) with different levels of diastereomer impurity were performed. Using process analytical technologies (PAT) technologies, the demixing region was identified by measuring TL–L curves and supersolubility curves for different series. It was found that a series with a higher level of impurity has a higher TL–L point and a wider demixing region. Besides, it seems that the resolution efficiency through oiling-out, as well as the crystallization kinetics, was significantly decreased. Here we initially put forward this particular diastereomer purification problem, where the impurity has a positive effect on oiling-out. To reduce or eliminate oiling-out, an efficient prepurification strategy must be ensured.

Nucleation and growth kinetics of struvite in a fluidized bed reactor

Kinetics of struvite crystallization were studied to gain a better understanding of intentional struvite formation in fluidized bed reactors. Mechanisms controlling nucleation were studied in the laboratory by induction time experiments. pH monitoring proved to be an effective method of induction time determination, during the induction period. The induction period, when nucleation was the controlling process for struvite crystal formation, was found to be primarily reaction controlled, with minor transport influence. The metastable region for struvite was explored in this study. The solubility and supersolubility curves, which are the boundaries of the metastable region, were observed to be almost parallel straight lines in the concentration range studied. The growth rate of struvite determined in a fluidized bed reactor was mainly transport controlled. With the determination of the mass-transfer coefficient and surface-reaction coefficient for a specified condition, a two-step linear growth rate model for struvite growth determination in a fluidized bed reactor has been proposed.

Systematic Improvement of Protein Crystals by Determining the Supersolubility Curves of Phase Diagrams

A systematic approach for improving protein crystals by growing them in the metastable zone using the vapor diffusion technique is described. This is a simple technique for optimization of crystallization conditions. Screening around known conditions is performed to establish a working phase diagram for the crystallization of the protein. Dilutions of the crystallization drops across the supersolubility curve into the metastable zone are then carried out as follows: the coverslips holding the hanging drops are transferred, after being incubated for some time at conditions normally giving many small crystals, over reservoirs at concentrations which normally yield clear drops. Fewer, much larger crystals are obtained when the incubation times are optimized, compared with conventional crystallization at similar conditions. This systematic approach has led to the structure determination of the light-harvesting protein C-phycocyanin to the highest-ever resolution of 1.45 Å.

Crystallogenesis studies on yeast aspartyl-tRNA synthetase: use of phase diagram to improve crystal quality.

Aspartyl-tRNA synthetase (AspRS) extracted from yeast is heterogeneous owing to proteolysis of its positively charged N-terminus; its crystals are of poor quality. To overcome this drawback, a rational strategy was developed to grow crystals of sufficient quality for structure determination. The strategy is based on improvement of the protein homogeneity and optimization of crystallization, taking advantage of predictions from crystal-growth theories. An active mutant lacking the first 70 residues was produced and initial crystallization conditions searched. The shape and habit of initial crystals were improved by establishing a phase diagram of protein versus crystallizing-agent concentrations. Growth of large well faceted crystals takes place at low supersaturations near the isochronic supersolubility curve. Further refinement led to reproducible growth of two crystalline forms of bipyramidal (I) or prismatic (II) habit. Both diffract X-rays better than crystals previously obtained with native AspRS. Complete data sets were collected at 3 A resolution for form I (space group P41212) and form II (space group P3221) and molecular-replacement solutions were found in both space groups.

Croissance cristalline des deux formes de LiIO 3

The existence conditions of hexagonal and tetragonal LiIO 3 in aqueous solution are investigated from experimental solubility and supersolubility curves. This study establishes the growth conditions for both structures. X ray diffraction measurements show that an irreversible transformation from hexagonal into tetragonal structure occurs at the temperature T c = 255 ± 1° C.

Supersolubility Curves for Copper Sulfate Pentahydrate Solutions

The authors carried out experiments similar to the work of Tin and McCabe. Tin and McCabe found two groups of supersolubility curves for MgSO4·E7H20 in continuously cooled, stirred, and seeded solutions. The location of these curves wa shown as dependent on several factors, but no attempt was made to derive any quantitative relations among them.In our experiments, unseeded and seeded solutions of copper sulfate were allowed to cool in a batch agitating vessel with cooling jacket at constantstirring speed. The flow rate of cooling water was kept constant, without contrriling the cooling rate.The ranges of experimental variables were as follows:Stirring speed in r. p. m. 140-780Rate of cooling water (w) in g/sec 10-80g. of seed crystals (CuSO4·5H20) per 100g. soln.(S) 0-10Initial sat'd. concn. of anhydrate in wt. per cent 22-32Corresponding initial sat'd. temperature in °C 38-70Observations were made on the point where the first nucleus appeared and the point where sudden crystallization took place, while simultaneously, the relations of time with temperature and concentration were determined.The point where temperature and concentration producedthe first appearance of crystals was named“first supersaturation point” and the point wheresudden crystallization occurred was called“second supersaturation point.”The temperature and concentration values at these points were determined from an analysis of the curves and the results of observation obtained under experimental conditions. The first supersaturation point thus obtained was plotted in Fig. 4, and the second supersaturation point in Figs. 2 to 3e.Fig. 4 shows an unique supersolubility curve which is obviously independent of the variables tested here. This fact differs from the results of Tin and McCabe. On the contrary, Figs. 2 to 3e indicate clearly the effects of stirring speed, theamount of seed crytals and the flow rate of cooling water. This shows a coincidence with their work qualitatively.The authors, therefore, attempted to correlate the data of the second supersaturation point, and obtained an experimental but dimensionless relation, as follows:CII′/CSII′=1.18(wcw/UAk)0.1·exp.(-0.028S)where CII′ and CsII′ are the second supersaturated and the saturated concentrations of CuSO4 at the same temperature, U is the over-all heat transfer coefficient, Ah, is the heat transfer area of agitated vessel, and cw, , is the heat capacity of cooling water, respectively.It is shown in Fig. 7 that the above relation coincides with the results of experiments within an accuracy of 10 per cent.

光学異性体の直接分割に関する研究 (第2報)

Crystallization temperature of aqueous solutions of dl-, d-, and l-threo-1-p-nitrophenyl-2-amino-1, 3-propanediols was measured in various concentrations and respective supersolubility curves approximately parallel to ordinary solubility curves were obtained. It was thereby found that these substances tended to form a stable supersaturated solution and that this tendency was especially strong in the racemic compound. The direct resolution of optical isomers proposed by Amiard was elucidated from this supersolubility curves and the solubility curves reported in the preceding paper, and its reason was clarified. These results provided fundamental data for a more theoretically advantageous procedure.

ジフェニルヒダントインナトリウムの過溶解度

The aqueous solution of diphenylhydantoin sodium does not easily precipitate out the crystals even in the state of supersaturation at temperatures below solid-liquid equilibrium. In a sealed tube, it was difficult to find the temperature at which the crystals precipitate out from the state of supersaturation. When such a solution is cooled under agitation in an unsealed vessel, reproducible results were obtained as to the temperature of crystal precipitation. The curve obtained by plotting such a temperature against the concentration of a solution was designated as the supersolubility curve, which was approximately parallel to the solubility curve.

Ar<sub>1</sub>變態の機構について(第1報)

The beginning temperatures of separation of α or Fe3C from austenite are represented by super-solubility curves G0S0 and E0S0 respectively and not by solubility curves. The idea of super-solubility curves were discussed and applied to explain the Ar1 transformation mechanism and the following results were obtained: When the steel was cooled from austenite range so show that the equilibrium state is established, (1) eutectoid reaction occurs not at the point S but at a temperature lower than S, which is the point of intersection of the lines GS and E0S0 (2) pearlite is produced from Fe3C nucleus, (3) pearlitic structure appears only in hypo-eutectoid steel and not in hyper-eutectoid. steel, (4) “abnormal structure” appears only in hyper-eutectoid steel and it is an intermediale structure, which appears when the temperature was lowered before the equilibrium was established in the temperature range between PSK and P0S0K0.

The Undercooling of some Aluminium Alloys

ALTHOUGH the undercooling of pure metals was observed by Roberts-Austen so long ago as 1898, no experiment have so far been published regarding the super of although explanations of certain structte have been based on their existence particularly regard to eutectics. The recent May Lecture of Sir Henry to the Institute of Metals o.n The Growth of Crystals in Supersaturated Liquids is now followed by a paper by Dr. Marie L. V. Gayler, delivered before the Institute of Metals on Sept. 7, on the effects of undercooling in some alloys of aluminium, in par-ticular with silicon. The work was carried out for the Engineering Research Board at the National Physical Laboratory under the supervision of Dr. W. Rosenhain and breaks entirely new ground. For the first time the supersolubility curves for an alloy system are available, and with their aid an explanation of the structures of the aluminium-silicon alloys can be offered with a considerable degree of certainty.

On the spontaneous crystallisation and the melting and freezing point curves of mixtures of two substances which from mixed crystals and posses a minimum or eutectic freezing point. —Mixtures of azobenzene and benzylaniline

The behaviour of mixtures of naphthalene and β-naphthol has already been investigated, and the freezing and melting point curves and the curve of spontaneous crystallisation for these mixtures described.* These substances were found to form a continuous series of mixed crystals, on a curve of Roozeboom’s Type 1, the melting and freezing points of all the mixtures lying between the melting points of the pure substances. The behaviour of mixtures of monochloracetic acid and naphthalene was also investigated, for it was stated by Cady that these substances form mixed crystals of Roozeboom’s Type 5, whose melting and freezing point curves exhibit a minimum or eutectic freezing point. Experiments were therefore made with these substances with the object of determining the form of the curve of spontaneous crystallisation, or supersolubility curve, for mixtures of this type. No sign of the formation of any mixed crystals was observed, however, in a lengthy series of experiments, and it was shown that naphthalene and monochloracetic acid give the ordinary V-shaped freezing point curve for the solutions of two substances in each other, similar to that already obtained for mixtures of salol and betol,§ the only new feature being introduced by the existence of three modifications of monochloracetic acid. The monochloracetic acid and naphthalene mixtures having thus failed as an example of mixed crystals possessing a minimum or eutectic freezing point, another attempt was made to obtain a pair of substances with convenient melting points which form mixed crystals and possess the melting and freezing point curves with minimum eutectic point characteristic of Roozeboom’s Type 5.

Societies and Academies

Societies and Academies

XIV. On the spontaneous crystallisation of monochloracetic acid and its mixtures with naphthalene

Our previous papers on spontaneous crystallisation have dealt with the supersolubility curves, firstly, of pure substances; secondly, of mixtures of two or more substances which do not form mixed crystals; and, finally, with naphthalene and β -naphthol; the last form mixed crystals of the type (l) of Roozeboom, in which the freezingpoints of all mixtures lie between the freezing-points of the pure components. The object for which the present investigation was undertaken was to study the spontaneous crystallisation of two substances which form mixed crystals and possess a minimum or eutectic freezing-point.