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  • 1.
    Aisling, Lynch
    et al.
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Mat & Surface Sci Inst, Dept Chem & Environm Sci, Limerick, Ireland..
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. Synthesis and Solid State Pharmaceutical Centre, Department of Chemical and Environmental Science, University of Limerick, Limerick, Ireland.
    Crystal Growth of Single Salicylamide Crystals2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 12, p. 7230-7239Article in journal (Refereed)
    Abstract [en]

    Growth of single salicylamide crystals was investigated in a nonstirred growth cuvette and on a rotating disk. In the growth cuvette the crystal growth rates were measured for both primary nucleated crystals and seed crystals manually inserted into the cuvette. In the rotating disk experiments multiple seed crystals were attached to a disk that was rotated in a supersaturated solution. The crystal growth rates in the length and width direction were precisely measured in situ for each individual crystal, and growth rates were also extracted for a specific crystal facet, that is, (200). In all cases, the growth rate was considerably faster in the rotating disk experiments, shown to be governed by surface integration. Solvent was found to impact the growth rates of the crystal facets in part by creating different surface features. The influence of the supersaturation on the crystal growth rate depended on the solvent; in general, an increasing trend was observed. At relatively low supersaturations, it was discovered that the growth process will focus on repairing morphological defects. Within the range of experimental conditions, the growth kinetics were strongly affected by the temperature as was further indicated by the relatively high activation energy values obtained. The crystal seed quality was found to have a substantial impact on the growth rate, with rougher crystals leading to quicker growth. A wide growth rate dispersion was obtained for both crystal growth methods, found to be reduced by using seed crystals with high quality, lower supersaturations, and also within certain solvents.

  • 2. Codan, L.
    et al.
    Casillo, S.
    Bäbler, Matthäus U.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Mazzotti, M.
    Phase diagram of a chiral substance exhibiting oiling out. 2. Racemic compound forming ibuprofen in water2012In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 11, p. 5298-5310Article in journal (Refereed)
    Abstract [en]

    This work investigates the ternary phase behavior of the two enantiomers of ibuprofen and water. The two enantiomers crystallize as a racemic compound and exhibit a thermodynamically stable liquid-liquid phase separation (LLPS), which extends over the entire enantiomeric composition range. First, the generic phase behavior of racemic compound forming systems exhibiting a stable LLPS is derived by exploiting the consolidated knowledge of conglomerate forming systems obtained in the first part of this series. Below the onset temperature of the LLPS, the system behaves like a typical racemic compound forming system. As for conglomerate forming systems, the onset of the LLPS is found to occur through a ternary monotectic equilibrium, where a new, solute-rich liquid phase emerges inside each solid-solid-liquid phase region. Then, the ternary phase diagram of the ibuprofen/water system in the temperature range from 40 to 82 °C is presented together with the outcome of a thorough experimental investigation. Our theoretical considerations are in excellent agreement with experimental results.

  • 3. Codan, Lorenzo
    et al.
    Bäbler, Matthäus
    Institute of Process Engineering, ETH Zurich.
    Mazzotti, Marco
    Phase Diagram of a Chiral Substance Exhibiting Oiling Out in Cyclohexane2010In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 9, p. 4005-4013Article in journal (Refereed)
    Abstract [en]

    This work investigates the ternary phase diagram of the enantiomers of ethyl-2-ethoxy-3-(4-hydroxyphenyl)propanoate (EEHP) in cyclohexane. The enantiomers of EEHP form aconglomerate, and both the pure enantiomer and the racemic mixture exhibit stable oilingout in cyclohexane. Our analysis shows that the ternary phase diagram of such a system assumes a unique structural evolution around the onset temperature of oiling out; that is, we found that the onset of oiling out strictly occurs through the emergence of a second liquid phase of racemic composition. Furthermore, we found that the further evolution of the ternary phase diagram, i.e., above the onset temperature of oiling out, is dictated by the properties of the phase diagrams pure enantiomer/solvent and racemic mixture/solvent. Our theoretical considerations are in excellent agreement with experimental measurements of EEHP in cyclohexane. 

  • 4. Croker, D. M.
    et al.
    Davey, R. J.
    Rasmuson, Åke Christoffer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. Univ Limerick, Mat & Surface Sci Inst, Dept Chem & Environm Sci.
    Seaton, C. C.
    Nucleation in the p-toluenesulfonamide/triphenylphosphine oxide co-crystal system2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 8, p. 3754-3762Article in journal (Refereed)
    Abstract [en]

    Nucleation has been studied in pure co-crystal and mixed co-crystal phase regions of the ternary phase diagram (TPD) in acetonitrile at 20 C using cooling crystallization experiments. Direct nucleation of each of the co-crystal phases in this system was independently observed in regions of the TPD where each is stable. In mixed regions, regions where either a co-crystal and a coformer, or both co-crystals, are stable, the phase that initially nucleated was a function of the mass composition in that region. The relative amount of each phase nucleating could be controlled by adjusting the relative mass fraction of each component. The kinetic return to equilibrium was also observed as the systems were held over time, with the selected mass fractions always returning to the equilibrium dictated by the TPD after 24 h

  • 5.
    Croker, Denise
    et al.
    Chemical and Environmental Science, University of Limerick, Ireland.
    Foreman, Michael
    University of Cork, Ireland.
    Hogan, Bridget
    University of Cork, Ireland.
    Maguire, Nuala
    University of Cork, Ireland.
    Curtis, Elcoate
    University of Cork, Ireland.
    Hodnett, Kieran
    Chemical and Environmental Science, University of Limerick, Ireland.
    Maguire, Anita
    University of Cork, Ireland.
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena. Univ Limerick, Ireland.
    Lawrence, Simon
    University of Cork, Ireland.
    Understanding the p-toluenesulfonamide / triphenylphosphine oxide crystal chemistry: a new 1:1 cocrystal and ternary phase diagram2012In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 2, p. 869-875Article in journal (Refereed)
    Abstract [en]

    A novel 1:1 cocrystal between p-toluenesulfonamide and triphenylphosphine oxide has been prepared and structurally characterized. This 1:1 cocrystal was observed to form during solid state grinding experiments, with subsequent formation of a known 3:2 cocrystal in the presence of excess sulfonamide. Both cocrystals are stable in the solid state. The ternary phase diagram for the two coformers was constructed in two different solvents: acetonitrile and dichloromethane. Examination of these diagrams clarified solution crystallization of both the newly discovered 1:1 cocrystal and the previously reported 3:2 cocrystal, and identified regions of stability for each cocrystal in each solvent. The choice of solvent was found to have a significant effect on the position of the solid state regions within a cocrystal system.

  • 6.
    Doe, Maofeng
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Department of Physics, University of Oslo, Norway .
    Analysis of the Semi local States in ZnO-InN Compounds2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 10, p. 4937-4943Article in journal (Refereed)
    Abstract [en]

    ZnO alloys are extensively explored for the developments of optoelectronics. In this work we analyze the rather unconventional type of ZnO-based compound ZnOX (ZnO)(1y)Xy with X = InN. The compound forms alloy with ZnO and/or assembles cluster structures in the ZnO host. Importantly, this type of alloy benefits from being isovalent which implies a more stable crystalline structure, and at the same time it benefits from the oxynitride anion-alloying that alters the optoelectronic properties. Theoretical studies reveal that incorporating InN in ZnO strongly narrows the fundamental band gap energy Eg. For example, the (ZnO)(0.875)(InN)(0.125) alloy has the gap energy E-g = 2.20 eV = E-g(ZnO) 1.14 eV. The origin of this effect is a hybridization of the anion N 2p-like and O 2p-like orbitals. Intriguingly, the presence of InN nanoclusters enhances this effect and narrows the gap further, and moreover, the nanostructured configurations show more disperse energy distribution of the hybridized anion states compared with the random alloy. Nanoclustering affects the ZnO host more compared to structures with more random distribution of the InN dimers. On the basis of the different characters of the alloys and the nanostructures, we conclude that fine-tuned synthesizing of the (ZnO)(1-y)(InN)(y) alloys can be beneficial for a variety of novel nanosystems for optoelectronic and photoelectrochemical applications.

  • 7. Gamidi, R. K.
    et al.
    Rasmuson, Åke Christoffer
    University of Limerick.
    Estimation of melting temperature of molecular cocrystals using artificial neural network model2017In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 17, no 1, p. 175-182Article in journal (Refereed)
    Abstract [en]

    quantitative structure-activity relationship model has been constructed by artificial neural networks for estimation of melting temperature (T-m) of molecular cocrystals (CCs). On the basis of a literature, analysis using SciFinder and Cambridge Structural Database softwares, a database has been created of CCs for four active pharmaceutical ingredients, namely, caffeine, theophylline (THP), nicotinamide (NA), and isonicotinamide (INA). In total, of 61 CCs were included: 14-CAF, 9-THP, 29-INA, and 9-NA. A good correlation was obtained with ANNs to quantify the T-m of the CCs with respect to various coformers. The training process was completed with an average relative error of 2.38%, whereas the relative error for the validation set was 2.89%.

  • 8.
    Gracin, Sandra
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Polymorphism and Crystallization of p-Aminobenzoic Acid2004In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 4, no 5, p. 1013-1023Article in journal (Refereed)
    Abstract [en]

    p-Aminobenzoic acid (PABA) crystallizes in two different polymorphic forms: the alpha-polymorph, which is the commercially available form and appears as long, fibrous needles, and the beta-polymorph, which appears in the form of prisms. The thermodynamic stability and crystallization from different solvents have been studied experimentally. The system is found to be enantiotropic with a transition temperature of 25degreesC, below which the beta-form is the stable polymorph. The compound has been crystallized from 13 different solvents, either by slow cooling after which the product is allowed to mature in suspension, or by rapid cooling followed by immediate isolation. Needles were obtained from all solvents by both methods. In water and in ethyl acetate, at slow cooling below 20degreesC, the prismatic beta-form is obtained, however, often together with the needles. The beta-form crystals usually needed hours or days to grow at the very slow cooling used, while needles usually appeared in seconds. By careful control of supersaturation and temperature, cooling crystallization can be performed to produce the pure beta-form in water and in ethyl acetate. The influence of the solvent is explained by analysis of the crystal structures versus the possible interaction of the solvent molecules with the solute in solution. The alpha-form structure is governed by carboxylic acid dimers and is kinetically favored since it is believed that the corresponding dimers easily form in the solution, especially in less polar solvents.

  • 9.
    Gracin, Sandra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Uusi-Penttilä, Marketta
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Influence of ultrasound on the nucleation of polymorphs of p-aminobenzoic acid2005In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 5, no 5, p. 1787-1794Article in journal (Refereed)
    Abstract [en]

    p-Aminobenzoic acid crystallizes in two different polymorphic forms: the alpha-form and the beta-form. The alpha-form crystals are needle-shaped, while the beta-form crystals have a more favorable prismatic shape. The system is enantiotropic with the transition temperature at approximately 25 degrees C. Below the transition temperature, the beta-form is the thermodynamically stable polymorph but can only be produced at very slow supersaturation generation either in water or in ethyl acetate. In the present work, the influence of ultrasound on the nucleation of p-aminobenzoic acid polymorphs has been investigated by use of several different sonication intensities and schemes. It is shown that sonication significantly reduces the induction time for nucleation. By using controlled sonication, we were able to more reproducibly crystallize the beta-form at more reasonable cooling rates. In addition, sonication is found to quite selectively favor the appearance of the beta-polymorph. It is even possible to produce the pure beta-form above the transition temperature where it is the metastable form and impossible to produce without sonication. The alpha-form structure is based on centro symmetric dimers formed by the association of carboxylic acid groups, while the beta-form contains four-membered hydrogen-bonded rings of alternating amino and carboxylic acid groups. It is suggested that ultrasound disturbs the building up of the dimers in the solution and thus favors the crystallization of the beta-polymorph.

  • 10.
    Gustafsson, Stefan
    et al.
    Department of Applied Physics, Chalmers University of Technology.
    Fornara, Andrea
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Petersson, Karolina
    Imego AB.
    Johansson, Christer
    Imego AB.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Olsson, Eva
    Department of Applied Physics, Chalmers University of Technology.
    Evolution of Structural and Magnetic Properties of Magnetite Nanoparticles for Biomedical Applications2010In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 5, p. 2278-2284Article in journal (Refereed)
    Abstract [en]

    We have investigated the evolution of microstructure and magnetic properties of thermally blocked magnetite nanoparticles, aimed for immunoassay applications, during their synthesis. High-resolution transmission electron microscopy (HRTEM) investigations of the size, size distribution, morphology, and crystal structure of particles reveal that particles at an early stage of the reaction process are either single crystals or polycrystals containing planar faults and they grow via a combination of reactant (monomer) consumption and oriented attachment at specific crystallographic surfaces because of the strong dipolar character of the < 111 > surfaces of magnetite. At a later stage of the synthesis reaction, the magnetic attraction strives to align contacting particles with their < 111 > axis of easy magnetization in parallel and this may also be an active driving force for crystal growth. At latter stages, the crystal growth is dominated by Ostwald ripening leading to smoother crystalline particles with a mean diameter of 16.7 +/- 3.5 nm and a narrow size distribution. The magnetic properties of the particles measured using static and dynamic magnetic fields are consistent with the evolution of particle size and structure and show the transition from superparamagnetic to thermally blocked behavior needed for magnetic relaxation-based immunoassay applications.

  • 11. Heffernan, C.
    et al.
    Ukrainczyk, M.
    Zeglinski, J.
    Hodnett, B. K.
    Rasmuson, Åke Christoffer
    Synthesis and Solid State Pharmaceutical Centre, Department of Chemical Sciences, Bernal Institute, University of Limerick.
    Influence of Structurally Related Impurities on the Crystal Nucleation of Curcumin2018In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, no 8, p. 4715-4723Article in journal (Refereed)
    Abstract [en]

    In this work, the influence of the structurally related impurities, demethoxycurcumin (DMC) and bisde-methoxycurcumin (BDMC) on the primary nucleation of curcumin (CUR) has been investigated in propan-2-ol. The induction time for nucleation was measured at different CUR driving forces and impurity concentrations 0.10 mmol.dm(-3), 0.30 mmol.dm(-3), and 0.60 mmol.dm(-3) and the results are analyzed by the classical nucleation theory (CNT). The nucleation rate for the impure systems was noticeably lower than the nucleation rate of the pure system, and the times of growth to visibility were much longer for the impure systems. The pre-exponential factors are clearly lower for the impure system compared to the pure CUR system, while the increase in the solid-liquid interfacial energy is small. Density functional theory and metadynamic molecular modeling reveal that the 1:1 bonding between CUR and an impurity molecule is stronger than to another CUR molecule, thus suggesting that the developing CUR nucleus has to overcome a certain energy barrier in order to remove the impurity molecules from their surface, which may explain why nucleation of CUR is more difficult in the presence of the structurally related impurities, DMC and BDMC.

  • 12. Hu, Y.
    et al.
    Erxleben, A.
    Hodnett, B. K.
    Li, B.
    McArdle, P.
    Rasmuson, Åke Christoffer
    Materials and Surface Science Institute, Department of Chemical and Environmental Sciences, University of Limerick.
    Ryder, A. G.
    Solid-state transformations of sulfathiazole polymorphs: The effects of milling and humidity2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 8, p. 3404-3413Article in journal (Refereed)
    Abstract [en]

    The effect of milling on the transitions of sulfathiazole polymorphs in the absence and presence of solvent and excipients was monitored by X-ray powder diffraction (XRPD), attenuated total reflectance infrared (ATR-IR), and near-infrared (NIR) spectroscopy. Sulfathiazole forms FII-FV undergo a transformation toward the metastable FI, which involves an intermediate amorphous stage upon milling at ambient temperature. Milling the commercial form (FC) with catalytic amounts of solvent converts it to pure FIV or to mixtures of FI and FIV depending on the solvent used. Pure FIV can be easily prepared from FC by this method. The physical stability of nonmechanically activated pure sulfathiazole forms in the presence of different levels of relative humidity (RH) was also investigated. At low RH, all sulfathiazole forms are kinetically stable, but at RH levels above 70% FII, FC and FIV remain stable, while FI and FV transform to mixtures of FII and FIV without any apparent change in the external form of the crystals. Comilling FC with a range of excipients gave results that depended on the excipient used, and comilling with cellulose gave samples that had an amorphous content that was stable at 10% RH for at least nine months at ambient temperature.

  • 13. Jayakumar, O. D.
    et al.
    Sudakar, C.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Sudarsan, V.
    Sakuntala, T.
    Naik, R.
    Tyagi, A. K.
    1D Morphology Stabilization and Enhanced Magnetic Properties of Co: ZnO Nanostructures on Codoping with Li: A Template-Free Synthesis2009In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 9, no 10, p. 4450-4455Article in journal (Refereed)
    Abstract [en]

    ID natiostructures of Zn1-xCoxO (x = 0, 0.03 and 0.05) and Co and Li codoped ZnO (Zn0.85Li0.10Co0.05O) were prepared by a soft chemical method. We report a very interesting observation of morphological control and transformation of ZnO nanorods to spherical particles induced by Co substitution. It is also remarkable to note that the morphology completely reverts back to rod shape by Li incorporation. In addition to this unusual observation, the Li incorporation enhances the room-temperature ferromagnetic (RTFM) properties. These experimental observations are well-supported by theory work as well. These results are significant, as the I D RTFM will have implications in spintronic devices.

  • 14.
    Jia, Lijun
    et al.
    University of Limerick, Ireland.
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland.
    Crystal Growth of Salicylic Acid in Organic Solvents2017In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 17, no 6, p. 2964-2974Article in journal (Refereed)
    Abstract [en]

    The crystal growth rate of salicylic acid has been determined by seeded isothermal desupersaturation experiments in different organic solvents (methanol, acetone, ethyl acetate, and acetonitrile) and at different temperatures (10, 15, 20, and 25 °C). In situ ATR-FTIR spectroscopy and principal component analysis (PCA) were employed for the determination of solution concentration. Activity coefficient ratios are approximately accounted for in the driving force determination. The results show that the dependence of the growth rate on the solvent at equal driving force varies with temperature; e.g., at 25 °C, the growth rate is highest in ethyl acetate and lowest in acetonitrile, while at 15 °C the growth rate is highest in acetonitrile. The growth rate data are further examined within the Burton Cabrera Franck (BCF) and the Birth and Spread (B+S) theories, and the results point to the importance of the surface diffusion step. Interfacial energies determined by fitting the B+S model to the growth rate data are well-correlated to interfacial energies previously determined from primary nucleation data.

  • 15. Kuhs, Manuel
    et al.
    Zeglinski, Jacek
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Influence of History of Solution in Crystal Nucleation of Fenoxycarb: Kinetics and Mechanisms2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 3, p. 905-915Article in journal (Refereed)
    Abstract [en]

    Nearly 1800 induction time experiments have been performed on crystal nucleation of fenoxycarb in isopropanol to investigate the influence of solution pretreatment. For each preheating temperature and preheating time, at least 80 experiments were performed to obtain statistically valid results. The relationship between the inverse of the induction time and the preheating time can be reasonably described as an exponential decay having time constants ranging up to days depending on the temperature. This dependence on the preheating temperature corresponds to an activation energy of more than 200 kJ/mol. Given sufficiently long preheating time and high temperature, the solution appears to reach a steady-state where the "memory" effect has disappeared. Density functional theory modeling suggests that the molecular packing in the crystal lattice is not the thermodynamically stable configuration at the level of simple dimers in solution, while modeling of the first solvation shell reveals that solute aggregation must exist in solution due to the low solvent-to-solute molecular ratio. It is thus hypothesized that the dissolution of crystalline material at first leaves molecular assemblies in solution that retain features of the crystalline structure which facilitates subsequent nucleation. However, the longer the solution is kept at a temperature above the saturation temperature and the higher the temperature, the more these assemblies disintegrate and transform into molecular structures less suited to form critical nuclei.

  • 16.
    Lankinen, A.
    et al.
    Optoelectronics Laboratory, Helsinki University of Technology.
    Tuomi, T.
    Optoelectronics Laboratory, Helsinki University of Technology.
    Karilahti, M.
    Optoelectronics Laboratory, Helsinki University of Technology.
    Zytkiewicz, Z. R.
    Institute of Physics, Polish Academy of Sciences.
    Domagala, J. Z.
    Institute of Physics, Polish Academy of Sciences.
    McNally, P. J.
    Research Institute for Networks and Communications Engineering, Dublin City University.
    Sun, Yan-Ting
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Crystal Defects and Strain of Epitaxial InP Layers Laterally Overgrown on Si2006In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, no 5, p. 1096-1100Article in journal (Refereed)
    Abstract [en]

    Defects in epitaxial laterally overgrown (ELO) InP layers are examined by high-resolution X-ray diffraction and synchrotron X-ray back-reflection and transmission topography. X-ray diffraction maps produce information about the overall crystal quality of the epitaxial layers in the InP ELO sample. The topographs show small angle boundaries, and the associated dislocations are located at the boundaries between the crystallites; allowing for their relative tilt, the maximum value for this is 0.06 degrees. No defects inside the crystallites can be seen in the topographs, except for a small bending of 0.04 degrees at most, of the ELO lattice planes. The section topographs show deformed X-ray interference fringes resulting from the large strain of the silicon lattice below the seeding areas.

  • 17.
    Liu, Jin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Influence of agitation and fluid shear on primary nucleation in solution2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 10, p. 4385-4394Article in journal (Refereed)
    Abstract [en]

    The influence of mechanical energy on primary nucleation of butyl paraben has been investigated through 1320 cooling crystallization experiments. The induction time has been measured at different supersaturations, temperatures, and levels of mechanical energy input, in two different flow systems. There is an overall tendency in the experiments that primary nucleation is promoted by increased input of mechanical energy. In small vials agitated by magnetic stir bars, the induction time was found to decrease with increasing agitation power input raised to 0.2 in the low agitation region. However, further increase in agitation leads to an increase again in the induction time. In a concentric cylinder apparatus of Taylor-Couette flow type, the induction time is inversely related to the shear rate. By fitting the parameters of the classical nucleation theory to experimental data, it is shown that the results can be explained as an influence on the pre-exponential factor. The treatment behind the pre-exponential factor is extended to account for the contribution of forced convection in a solution exposed to agitation and fluid shear. However, the analysis cannot verify that increased rate of mass transfer can explain the results. Alternative mechanisms are discussed based on a comprehensive review of the relevant literature. Shear-induced molecular alignment and in particular agitation-enhanced cluster aggregation are mechanisms that appear to deserve further attention.

  • 18.
    Liu, Jin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland .
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland .
    Influence of agitation and fluid shear on nucleation of m-Hydroxybenzoic acid polymorphs2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 11, p. 5521-5531Article in journal (Refereed)
    Abstract [en]

    The influence of agitation and fluid shear on nucleation of m-hydroxybenzoic acid polymorphs from 1-propanol solution has been investigated through 1160 cooling crystallization experiments. The induction time has been measured at different supersaturations and temperatures in two different crystallizer setups: small vials agitated by magnetic stir bars, for which experiments were repeated 4080 times, and a rotating cylinder apparatus, for which each experiment was repeated five times. The nucleating polymorph has in each case been identified by FTIR spectroscopy. At high thermodynamic driving force for nucleation, only the metastable polymorph (form II) was obtained, while at low driving force both polymorphs were obtained. At equal driving force, a higher temperature resulted in a larger proportion of form I nucleations. The fluid dynamic conditions influence the induction time, as well as the polymorphic outcome. Experiments in small vials show that the agitation rate has a stronger influence on the induction time of form II compared to form I. The fraction of form I nucleations is significantly lower at intermediate agitation rates, coinciding with a reduced induction time of form II. In experiments in the rotating cylinder apparatus, the induction time is found to be inversely correlated to the shear rate. The difference in polymorphic outcome at different driving force is examined in terms of the ratio of the nucleation rates of the two polymorphs, calculated by classical nucleation theory using determined values of the pre-exponential factor and interfacial energy for each polymorph. A possible mechanism explaining the difference in the influence of fluid dynamics on the nucleation of the two polymorphs is based on differences between the two crystal structures. It is hypothesized that the layered structure of form II is comparatively more sensitive to changes in shear flow conditions than the more isotropic form I structure.

  • 19.
    Liu, Jin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland.
    Influence of Agitation on Primary Nucleation in Stirred Tank Crystallizers2015In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 15, no 9, p. 4177-4184Article in journal (Refereed)
    Abstract [en]

    The influence of agitation on nucleation of butyl paraben and m-hydroxybenzoic acid polymorphs has been investigated through 330 cooling crystallization experiments. The induction time has been measured at different supersaturations and temperatures in three parallel jacketed vessels equipped with different overhead stirring agitators. In each case, the nucleating polymorph of m-hydroxybenzoic acid has been identified by infrared spectroscopy. The influences of agitation rate, impeller type, impeller diameter, impeller to bottom clearance, and the use of baffles have been investigated. A general trend in all of the experiments is that the induction time decreases with increasing agitation rate. Across all experiments with different fluid mechanics for the butyl paraben system, the induction time is correlated to the average energy dissipation rate raised to the power -0.3. It is shown that this dependence is consistent with a turbulent flow enhanced cluster coalescence mechanism. In experiments with m-hydroxybenzoic acid, the metastable form II was always obtained at higher nucleation driving force while both polymorphs were obtained at lower driving force. In the latter case, form I was obtained in the majority of experiments at low agitation rate (100 rpm) while form II was obtained in all experiments at higher agitation rate (>= 300 rpm).

  • 20.
    Lynch, Aisling
    et al.
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick, Ireland..
    Jia, Lijun
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick, Ireland..
    Svärd, Michael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick, Ireland.
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick, Ireland..
    Crystal Growth of Salicylamide in Organic Solvents2018In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, no 12, p. 7305-7315Article in journal (Refereed)
    Abstract [en]

    Salicylamide was used as a model active pharmaceutical compound to investigate the crystal growth process and its associated kinetics. The impact of organic solvent, supersaturation, and temperature on the crystal growth was studied. The multiparticle crystal growth kinetics were determined using the seeded isothermal desupersaturation method and modeled using several growth rate equations, using different representations of the driving force. The results showed that crystal growth is significantly influenced by experimental conditions. Within the range of experimental conditions, the growth kinetics was affected strongly by the temperature and to a lesser degree by solvent choice. Comparison of the growth order parameter reveals a surface integration controlled growth. Higher than expected activation energies indicate desolvation as a governing process. A comparison of the influence of the solvent on the crystal growth of salicylamide against previously published approximate data at much higher supersaturation shows good agreement, but the influence on the interfacial energy is opposite to that observed for crystal nucleation. In a detailed comparison with crystal growth data of salicylic acid, there is a consistency in the influence of the solvent on the crystal growth of the two compounds. Salicylamide growth kinetics is more strongly affected by increasing temperature than salicylic acid.

  • 21.
    Munroe, Aina
    et al.
    Chemical and Environmental Science, University of Limerick, Ireland.
    Rasmuson, Åke Christoffer
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Hodnett, Kieran
    Chemical and Environmental Science, University of Limerick, Ireland.
    Croker, Denise
    Chemical and Environmental Science, University of Limerick, Ireland.
    The Preparation, Characterisation and Stability of the Five Polymorphs of SulphathiazoleIn: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505Article in journal (Other academic)
  • 22. Nordström, Fredrik L
    et al.
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Malmberg, Baldur
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Influence of Solution Thermal and Structural History on the Nucleation of m-Hydroxybenzoic Acid Polymorphs2012In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 9, p. 4340-4348Article in journal (Refereed)
    Abstract [en]

    The influence of solution pretreatment on primary nucleation of m-hydroxybenzoic acid has been investigated through 550 cooling crystallization experiments. The metastable zone width has been determined at constant cooling rate, and the time and temperature of the preceding superheating step have been varied. m-Hydroxybenzoic acid has two polymorphs, and the influence of the polymorph used to prepare the solutions has also been investigated. There is an overall tendency in the experiments for the solution to exhibit a larger metastable zone width if it is superheated for a longer time and at a higher temperature, but under the investigated conditions this tendency is not very strong. The results show that the metastable form II preferentially crystallizes in all experiments and in particular when the solution has been more strongly superheated for several hours. However, when the time and/or the temperature of superheating is reduced, there is an increasing tendency to obtain the stable form I. This is most clearly found for solutions prepared by dissolving form I. When the solutions are prepared by dissolution of form II, this tendency is weaker in what appears to be a systematic way. It is hypothesized that, unless the solution is strongly superheated for several hours, it will contain for a significant period of time clusters of solute molecules that can retain some degree of structure from the dissolved crystal. This leads to "memory" effects in the solution, which may influence subsequent nucleation. The work includes a comprehensive review of previous published work on the influence of thermal history on nucleation in solutions and melts.

  • 23. Ohtsuka, T.
    et al.
    Tsai, Yen-Hsi Richard
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA. University of Texas at Austin, TX, United States.
    Giga, Y.
    Growth Rate of Crystal Surfaces with Several Dislocation Centers2018In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, no 3, p. 1917-1929Article in journal (Refereed)
    Abstract [en]

    We studied analytically and numerically the growth rate of a crystal surface growing by several screw dislocations. We observed some discrepancy between the growth rates computed by our level set method (J. Sci. Comput. 2015, 62.

  • 24.
    O'Mahony, Marcus
    et al.
    Chemical and Environmental Sciences, University of Limerick, Ireland.
    Maher, Anthony
    Chemical and Environmental Sciences, University of Limerick, Ireland.
    Croker, Denise
    Chemical and Environmental Sciences, University of Limerick, Ireland.
    Rasmuson, Åke Christoffer
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Hodnett, Kieran
    Chemical and Environmental Sciences, University of Limerick, Ireland.
    Examining Solution and Solid State Composition for the Solution Mediated Polymorphic Transformation of Carbamazepine and Piracetam2012In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505Article in journal (Refereed)
    Abstract [en]

    Solution-mediated polymorphic transformations (SMPT) of the pharmaceutical compounds carbamazepine and piracetam have been investigated. Seeded transformation experiments were performed, and the solution concentration was monitored by in situ infrared spectroscopy using a calibration free method. Solid samples were also taken over time, and the percentage of metastable and stable polymorphic phases were determined using off line quantitative powder X-ray diffraction analysis. Solution and solid state data were compared for each compound. In the case of carbamazepine, the SMPT from FI to FIII was identified as being controlled by the growth of the stable FIII polymorph. For piracetam, the SMPT was also identified as being controlled by growth of the stable polymorph, but with a more considerable induction time for nucleation of the stable phase. This paper demonstrates how the rate determining steps of the SMPT can be identified if both solution and solid phase data are recorded. The results are compared with other studies reported in the literature and rationalized into four principal scenarios.

  • 25.
    Pino-Garcia, Osvaldo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of additives on nucleation of vanillin: Experiments and introductory molecular simulations2004In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 4, no 5, p. 1025-1037Article in journal (Refereed)
    Abstract [en]

    Nucleation of vanillin (VAN) in 2-propanol/water in the presence of additives, viz., acetovanillone (AVA), ethyl vanillin (EVA), guaiacol (GUA), guaethol (GUE), 4-hydroxyacetophenone (HAP), 4-hydroxybenzaldehyde (HBA), and vanillic acid (VAC) is investigated experimentally and by molecular simulations. In the experimental work, the induction time for nucleation is measured at different temperatures and levels of supersaturation using a multicell apparatus. A large variation in the experimental data is observed, and this variation is analyzed by statistical methods. By classical nucleation theory, the induction time data are used to estimate the solid-liquid interfacial energy of vanillin for each VAN-additive system. At 1 mol %, the interfacial energy becomes lower in the presence of AVA, EVA, HAP, and VAC, while it becomes higher in the presence of the other additives. As the additive concentration increases from 1 to 10 mol %, the interfacial energy also increases. The interfacial energy ranges from 6.9 to 10.1 mK m(-2). Molecular modeling, implemented in the program Cerius2, is used to simulate and examine the surface chemistry of the likely crystal growth faces of VAN (i.e., {001} and {100}). To evaluate the additive-crystal face interaction energy, two approaches are used: the surface adsorption method and the lattice integration method. Both experimental and molecular simulation results indicate that the additives studied are potential modifiers of the nucleation of VAN. However, a simple and clear relationship between the experimental values of interfacial energy and the calculated interaction energies for the most important crystal faces of VAN cannot be identified. The modeling does not concern the actual nucleation but rather the conditions of a growing surface and are based on several severe simplifications. Obviously, this simplistic approach does not sufficiently capture the influence of additives on the nucleation of vanillin.

  • 26. Profir, V. M.
    et al.
    Furusjo, E.
    Danielsson, L. G.
    Rasmuson, Åke C.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Study of the crystallization of mandelic acid in water using in situ ATR-IR spectroscopy2002In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 2, no 4, p. 273-279Article in journal (Refereed)
    Abstract [en]

    Different aspects related to the separation of enantiomers of mandelic acid by direct crystallization are explored. Solubility, nucleation, and solid-phase transformation in aqueous solutions are investigated. Results show that a metastable conglomerate can be formed for a substance known to appear as a racemic compound. After a time-lag, the conglomerate transforms into the stable racemic compound. The time-lag ranges from a few minutes to 8 h depending on the operation conditions. The time-lag decrease's at increasing concentration/temperature and in the presence of micrometer-sized particles. In situ attenuated total reflectance infrared (ATR-IR) spectroscopy and a partial least squares (PLS) calibration model are used to record the concentration of dissolved mandelic acid. Since no sampling is required and the calibration set, which is used on both racemic and enantiomerically pure solutions, can be built using the cheaper racemate, the technique should be of particular interest in applications involving chiral substances.

  • 27. Profir, V. M.
    et al.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Crystallization of stable and metastable phases of phenylsuccinic acid2006In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, no 5, p. 1143-1153Article in journal (Refereed)
    Abstract [en]

    In the crystallization of a racemic mixture, formation of a conglomerate, i.e., a mechanical Mixture of enantiomerically pure crystals, is the basic requirement for separation of enantiomers by preferential crystallization. Phenylsuccinic acid (PSA) is in the literature reported as a system forming a racemic compound, i.e., each crystal is an ordered mixture of the two enantiomers. In the present work, the properties of PSA were explored, with the underlying ambition of finding a conglomerate. Racemic PSA was crystallized by unseeded batch cooling crystallization in water, in acetic acid, and in 2-propanol (IPA). The corresponding data on solubility and the metastable limits were determined. Crystallization of racemic PSA in seven different solvents generated racemic PSA solvates with 2-propanol and with dioxane, respectively. The solubility of the (RS)-PSA.IPA solvate was determined, and the transition temperature between the solvated and the ansolvate (RS)-PSA I was found to be 16.5 degrees C. In addition to the solution crystallization investigation, an extensive thermal analysis of the racemate and of pure (S)-PSA was performed. A metastable racemate was produced by melt crystallization but was never obtained in Solution crystallization, although unusually high cooling rates combined with different levels of concentration and stirring conditions were used. Throughout this work, the solution concentration and the crystal modification type obtained upon nucleation were determined by in situ ATR-FTIR spectroscopy coupled with multivariate Partial Lease Squares (PLS) calibrations. The work suggests that for a system reported to be forming a racemic compound, there are at least three opportunities to find a conglomerate that should be explored: (i) a conglomerate that may be the stable modification at a different higher or lower temperature; (ii) a metastable conglomerate that may have a sufficient stability for a separation to be performed; (iii) a solvated conglomerate, either more or less stable than the ansolvate.

  • 28.
    Profir, Veronica M.
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Influence of solvent and the operating conditions on the crystallization of racemic mandelic acid2004In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 4, no 2, p. 315-323Article in journal (Refereed)
    Abstract [en]

    The crystallization of racemic mandelic acid is studied in unseeded batch cooling experiments in four solvent systems. Apart from the thermodynamically stable racemic compound, a metastable modification of the racemic compound is also found to initially form upon nucleation. The metastable racemate is characterized by thermal analysis (MDSC), FTIR spectroscopy, and X-ray powder diffraction (XRPD). The experiments show that the type of crystal modification that is formed upon nucleation is strongly influenced by the operating conditions such as filtration, cooling rate, and stirring rate, as well as by the solvent. The solvent effect can be related to the characteristics of the crystal structures of the two modifications, and to the hydrogen bonding properties of the solvent. The crystal structure of the metastable modification of the racemic compound is very similar to that of the pure enantiomer, which explains the similarity of the FTIR spectra, the XRPD diffraction pattern, and the thermodynamic stability.

  • 29.
    Soroka, Inna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Norrfors, Knapp Karin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Swedish Univ Agr Sci, Dept Soil & Environm, SLU, Lennart Hjelms Vag 9, S-75651 Uppsala, Sweden..
    Tarakina, Nadezda, V
    Queen Mary Univ London, Sch Engn & Mat Sci, Mile End Rd, London E1 4NS, England.;Max Planck Inst Colloids & Interfaces, Muhlenberg 1, D-14476 Potsdam, Germany..
    Nonconvex Morphology of Metallic Copper Obtained via Nonclassical Crystallization of Copper Hydride2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 9, p. 5275-5282Article in journal (Refereed)
    Abstract [en]

    Copper particles with a desert rose morphology and high surface area were obtained via decomposition of a copper hydride whose particles possesses a similar shape. Copper hydride was synthesized by the reaction between copper sulfate and hypophosphorous acid at 50 degrees C. The different reaction steps of the copper hydride formation were monitored by two time-dependent techniques: in situ photon cross-correlation spectroscopy and ex -situ transmission electron microscopy. At the initial stage of the reaction, emulsion droplets of a particular size were formed, followed by the growth and agglomeration of copper hydride crystallites in the confinement of these droplets. The final structure consists of roselike shaped particles with an average size of about 217 +/- 53 nm arranged into chains. The surface area of these particles was estimated to be 41 +/- 8 m(2)/g. The nucleation and growth of the copper hydride occur via a nonclassical crystallization pathway.

  • 30.
    Soto, Rodrigo
    et al.
    Univ Limerick, Dept Chem & Environm Sci, Synth & Solid State Pharmaceut Ctr SSPC, Bernal Inst, Limerick V94 T9PX, Ireland..
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena. Univ Limerick, Dept Chem & Environm Sci, Synth & Solid State Pharmaceut Ctr SSPC, Bernal Inst, Limerick V94 T9PX, Ireland.
    Crystal Growth Kinetics of Piracetam Polymorphs in Ethanol and Isopropanol2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 8, p. 4273-4286Article in journal (Refereed)
    Abstract [en]

    The crystal growth kinetics of two different polymorphs of Piracetam have been investigated in ethanol and isopropanol. Isothermal seeded desupersaturation experiments were carried out at supersaturation ratios below 1.2 within the range of temperature 283-308 K. Liquid concentration was determined by in situ ATR-FTIR spectroscopy by a calibration-free method using principal component analysis. The power law equation and the BCF and B+S models were fitted to the experimental desupersaturation data by nonlinear optimization. The growth rates ranged 10(-7)-10(-8) m/s, the growth rate order is clearly higher than unity, and the activation energies are in the range 39-66 kJ/mol for all the systems studied suggesting surface integration control. The growth of the metastable polymorph is faster than that of the stable form in both solvents. The crystal growth proceeds faster in ethanol than in isopropanol for both polymorphs. The solid-liquid interfacial energy is lower for the metastable form and is for both forms lower in ethanol than in isopropanol. The surface diffusion mass transfer rate is higher for the metastable form compared to the stable form and higher in ethanol than in isopropanol.

  • 31.
    Svärd, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Nordström, Fredrik L.
    Jasnobulka, Tanja
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Thermodynamics and Nucleation Kinetics of m-Aminobenzoic Acid Polymorphs2010In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 1, p. 195-204Article in journal (Refereed)
    Abstract [en]

    The polymorphism of m-aminobenzoic acid has been investigated. Two polymorphs have been identified and characterized by X-ray powder diffraction (XRPD), Fourier transform IR (FTIR), microscopy, and thermal analysis. The melting properties and isobaric heat capacities of both polymorphs have been determined calorimetrically, and the solubility of each polymorph in several solvents at different temperatures has been determined gravimetrically. The solid-state activity (i.e., the Gibbs free energy of fusion) of each polymorph has been determined through a comprehensive thermodynamic analysis based on experimental data. It is found that the polymorphs are enantiotropically related, with a stability transition temperature of 156.1 °0C. The published crystal structure belongs to the polymorph that is metastable at room temperature. Energytemperature diagrams of both polymorphs have been established by determining the free energy, enthalpy, and entropy of fusion as a function of temperature. A total of 300 cooling crystallizations have been carried out at constant cooling rate using different saturation temperatures and solvents, and the visible onset of primary nucleation was recorded. The results show that for this substance the polymorph that will nucleate depends chiefly on the solvent. In water and methanol solutions, the stable form I was obtained in all experiments, whereas in acetonitrile, a majority of nucleation experiments resulted in the isolation of the metastable form II. It is shown how this can be rationalized by analysis of solubility, solution speciation, and nucleation relationships. The importance of carrying out multiple experiments at identical conditions in nucleation studies of polymorphic systems is demonstrated.

  • 32.
    Svärd, Michael
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. University of Limerick, Ireland.
    m-Hydroxybenzoic Acid: Quantifying Thermodynamic Stability and Influence of Solvent on the Nucleation of a Polymorphic System2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 3, p. 1140-1152Article in journal (Refereed)
    Abstract [en]

    Nucleation of m-hydroxybenzoic acid crystals in different pure solvents has been investigated, and the thermodynamic interrelationship between two polymorphs was analyzed. The melting properties and specific heat capacities of both polymorphs have been determined by differential scanning calorimetry, and the solubility in several solvents at different temperatures was measured gravimetrically. Absolute values of the Gibbs free energy, enthalpy and entropy of fusion, and the activity of the polymorphs have been determined as functions of temperature. It is established that the polymorphs are monotropically related, with differences in enthalpy and Gibbs free energy of approximately 1 kJ/mol at room temperature. In a total of 539 nucleation experiments, in six solvents and with different cooling rates, the visible onset of nucleation was recorded and the nucleating polymorph was isolated. It is found that the degree of supersaturation required for nucleation and the polymorphic outcome depend strongly on the solvent. The metastable polymorph is kinetically favored under all evaluated experimental conditions, and for most of the conditions it is also statistically the most probable outcome. Nucleation of the stable polymorph is increasingly promoted in solvents of increasing solubility. It is shown how this can be rationalized by analysis of solubility and rate of supersaturation generation.

  • 33. Tierney, T. B.
    et al.
    Guo, Y.
    Beloshapkin, S.
    Rasmuson, Åke Christoffer
    University of Limerick.
    Hudson, S. P.
    Investigation of the Particle Growth of Fenofibrate following Antisolvent Precipitation and Freeze-Drying2015In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 15, no 11, p. 5213-5222Article in journal (Refereed)
    Abstract [en]

    Submicron to small-micron-sized particles of the hydrophobic drug, fenofibrate, were prepared by controlled crystallization in order to influence its dissolution behavior. An antisolvent precipitation process successfully generated particles (200−300 nm) which matched the size and dissolution behavior of a commercial wet-milled formulation of the drug. Although the preparation of submicron-sized particles was straightforward, retaining their size in suspension and during isolation was a challenge. Additives were employed to temporarily stabilize the suspension, and extend the time window for isolation of the submicron particles. Precipitated particles were isolated primarily by immediate freeze−drying, but drying stresses were found to destabilize the fragile submicron system. The growth pathway of particles in suspension and during oven and freeze−drying were compared. Although the growth pathways appeared considerably different from a visual morphological perspective, an investigation of the electron diffraction patterns and the inner-particle surfaces showed that the growth pathways were the same: molecular addition by Ostwald ripening. The observed differences in the time-resolved particle morphologies were found to be a result of the freeze−drying process.

  • 34.
    Usman, Rabia
    et al.
    Southeast Univ, Sch Chem & Chem Engn, Nanjing 211189, Jiangsu, Peoples R China..
    Khan, Arshad
    Southeast Univ, State Key Lab Bioelect, Nanjing 210096, Jiangsu, Peoples R China..
    Wang, Mingliang
    Southeast Univ, Sch Chem & Chem Engn, Nanjing 211189, Jiangsu, Peoples R China..
    Luo, Yi
    Southeast Univ, Sch Mat Sci & Engn, Jiangsu Key Lab Adv Metall Mat, Nanjing 211189, Jiangsu, Peoples R China..
    Sun, Weiwei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Sun, Hao
    Southeast Univ, Sch Chem & Chem Engn, Nanjing 211189, Jiangsu, Peoples R China..
    Du, Cunbin
    Southeast Univ, Sch Chem & Chem Engn, Nanjing 211189, Jiangsu, Peoples R China..
    He, Nongyue
    Southeast Univ, State Key Lab Bioelect, Nanjing 210096, Jiangsu, Peoples R China..
    Investigation of Charge-Transfer Interaction in Mixed Stack Donor-Acceptor Cocrystals Toward Tunable Solid-State Emission Characteristics2018In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 18, no 10, p. 6001-6008Article in journal (Refereed)
    Abstract [en]

    The formation of three mixed binary charge transfer (CT) cocrystals with tunable photoluminescence behavior featuring both CT interaction and directional hydrogen bonding is presented. Our strategy consists of the CT induced cocrystallization of three polycyclic (naphthalene, anthracene, and pyrene) carrying a-cyanostilbene (CS) derivatives, namely, 3-(naphthalene-2-yl)-2-(p-tolyl) acrylonitrile (NPA), 3-(anthracene-9-yl)-2-phenylacrylonitrile (APA), and 2-(4-methoxyphenyl)-3-(pyrene-I-yl) acrylonitrile (MPA) as donors (D) with 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor (A). The as prepared cocrystals were probed in detail by various analytical techniques, namely, X-ray diffraction data, vibrational spectroscopy, diffuse reflectance absorption spectroscopy, fluorescence properties, and fluorescence quantum yields and lifetimes, affirming the formation of CT complexes. Complex IA features a mixed stack arrangement (D-A-D-A-D), while IIA and IIIA revealed (DAD-DAD) stack arrangement. The CT products showed distinct tunable emission colors and photoluminescence characteristics, which is closely associated with the CT interactions between the donor and acceptor moiety, and ionization potential or the it pi-electron rich character of the polycyclic moiety of the donor molecule. This research demonstrates the development of new hybrid CT functional materials with enhanced optical properties such as absorption, fluorescence emissions, and lifetimes compared to the pristine donors, which is important for the exploration of new solid-state luminescent materials.

  • 35.
    Valavi, Masood
    et al.
    University of Limerick, Ireland.
    Svärd, Michael
    University of Limerick, Ireland.
    Rasmuson, Åke C.
    University of Limerick, Ireland.
    Improving Estimates of the Crystallization Driving Force: Investigation into the Dependence on Temperature and Composition of Activity Coefficients in Solution2016In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 16, no 12, p. 6951-6960Article in journal (Refereed)
    Abstract [en]

    The influence of temperature and composition on solution activity coefficients has been investigated. Under most conditions, the temperature dependence of the activity coefficient is much weaker than the composition dependence. A novel and more accurate approach to estimate crystallization driving forces is proposed, where, rather than neglecting the activity coefficient ratio, it can be estimated from solid−liquid equilibrium data.

  • 36.
    Yang, Huaiyu
    et al.
    Loughborough Univ, Dept Chem Engn, Loughborough, Leics, England.;Imperial Coll London, Dept Chem Engn, London, England..
    Huang, Lei
    Imperial Coll London, Dept Chem Engn, London, England..
    Zhang, Fan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Karde, Vikram
    Imperial Coll London, Dept Chem Engn, London, England..
    Yang, Zhongqiang
    Tsinghua Univ, Dept Chem, Minist Educ, Key Lab Organ Optoelect & Mol Engn, Beijing, Peoples R China..
    Heng, Jerry Y. Y.
    Imperial Coll London, Dept Chem Engn, London, England.;Imperial Coll London, Inst Mol Sci & Engn, London, England..
    Gravity on Crystallization of Lysozyme: Slower or Faster?2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 12, p. 7402-7410Article in journal (Refereed)
    Abstract [en]

    With the increase in applications of protein-based medicines approved and developed, downstream manufacturing of biopharmaceuticals has challenges of finding cost-effective and reliable routes. Biocrystallization and centrifugation have both been used to isolate and purify macromolecules, such as therapeutic protein and other functional proteins. However, the centrifugation cannot perfectly separate biomolecules, and the biocrystallization mainly focuses on structure determination on a scale of microliters or below. In this work, protein crystallization of lysozyme, with a concentration of 35-45 mg/mL, and sodium chloride, with a concentration of 45-55 mg/mL in the solution, on a scale of milliliters was performed under centrifugation. Different gravity levels of 1-20000g and centrifugation durations have been investigated during the nucleation and crystal growth process. There were no obvious influences of low gravity (<100g) and short duration (<5 min) of centrifugation on the crystallization process: i.e., on the changes in concentrations. With continuous centrifugation (>30 min), high gravity (>1000g) hindered the nucleation, i.e., it reduced the drop in concentration at the nucleation stage; however, it accelerated the crystal growth process, i.e. enhanced a at the crystal growth stage.

  • 37.
    Yang, Huaiyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Limerick University.
    Nucleation of butyl paraben in different solvents2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 10, p. 4226-4238Article in journal (Refereed)
    Abstract [en]

    The primary nucleation induction time of butyl paraben in pure solvents: acetone, ethyl acetate, methanol, ethanol, and propanol and in 70% and 90% ethanol aqueous mixtures has been determined. At each condition, about 100 experiments have been performed in 5 mL scale to capture the statistics of the nucleation process. The induction times at each condition show a wide variation. The data has been evaluated within the framework of the classical nucleation theory using several of the current approaches. Overall, the data obtained from the different methods of evaluation are surprisingly consistent. At comparable driving forces, nucleation is clearly fastest in acetone and slowest in propanol, with methanol, ethyl acetate, and ethanol in between. Adding water to the ethanol leads to a clear reduction in the nucleation rate. The solid-solution interfacial energy of butyl paraben in the different solvents decreases in the order: 70% ethanol > 90% ethanol > propanol > ethanol > ethyl acetate > methanol > acetone, which is surprisingly well-correlated to a decreasing solvent boiling point. It is shown that the same trend can be found for other systems in the literature. With the assumption that the stronger the bonding in the bulk phases, the higher the interfacial energy becomes, this observation is paralleled by the fact that a metastable polymorph has a lower interfacial energy than the stable form and that a solid compound with a higher melting point appears to have a higher solid-melt and solid-solution interfacial energy.

  • 38.
    Yang, Huaiyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Strathclyde Institute of Pharmacy and Pharmaceutical Sciences, University of Strathclyde3, United Kingdom .
    Svärd, Michael
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Department of Chemical and Environmental Science, Materials and Surface Science Institute, University of Limerick, Ireland .
    Zeglinski, Jacek
    Rasmuson, Åke
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena. Department of Chemical and Environmental Science, Materials and Surface Science Institute, University of Limerick, Ireland .
    Influence of Solvent and Solid-State Structure on Nucleation of Parabens2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 8, p. 3890-3902Article in journal (Refereed)
    Abstract [en]

    In the present work, the induction time for nucleation of ethyl paraben (EP) and propyl paraben (PP) in ethanol, ethyl acetate, and acetone has been measured at different levels of supersaturation. The induction time shows a wide variation among repeat experiments, indicative of the stochastic nature of nucleation. The solid-liquid interfacial energy and the size of the critical nucleus have been determined according to the classical nucleation theory. Combined with previous results for butyl paraben (BP), the nucleation behavior is analyzed with respect to differences in the solid phase of the three pure compounds, and with respect to differences in the solution. The results indicate that the difficulty of nucleation in ethanol and acetone increases in the order BP < PP < EP but is approximately the same in ethyl acetate. For each of the three parabens, the difficulty of nucleation increases in the order acetone < ethyl acetate < ethanol. The Gibbs energy of melting increases in the order BP < PP < EP, but the crystal structures are quite similar resulting in the basic crystal shape being very much the same. The solid-liquid interfacial energy is reasonably well correlated to the solvation energy, and even better correlated to the deformation energy, of the solute molecule within the first solvation shell as obtained by density functional theory calculations.

  • 39.
    Zeglinski, Jacek
    et al.
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick V94 T9PX, Ireland..
    Kuhs, Manuel
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick V94 T9PX, Ireland..
    Devi, K. Renuka
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick V94 T9PX, Ireland..
    Khamar, Dikshitkumar
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick V94 T9PX, Ireland..
    Hegarty, Avril C.
    Univ Limerick, Dept Math & Stat, MACSI, Limerick, Ireland..
    Thompson, Damien
    Univ Limerick, Synth & Solid State Pharmaceut Ctr, Bernal Inst, Dept Chem Sci, Limerick V94 T9PX, Ireland.;Univ Limerick, Dept Phys & Energy, Limerick, Ireland..
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena.
    Probing Crystal Nucleation of Fenoxycarb from Solution through the Effect of Solvent2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 4, p. 2037-2049Article in journal (Refereed)
    Abstract [en]

    Induction time experiments, spectroscopic and calorimetric analysis, and molecular modeling were used to probe the influence of solvent on the crystal nucleation of fenoxycarb (FC), a medium-sized, flexible organic molecule. A total of 800 induction times covering a range of supersaturations and crystallization temperatures in four different solvents were measured to elucidate the relative ease of nucleation. To achieve similar induction times, the required thermodynamic driving force, RT In S, increases in the order: ethyl acetate < toluene < ethanol < isopropanol. This is roughly matched by the order of interfacial energies calculated using the classical nucleation theory. Solvent solute interaction strengths were estimated using three methods: solvent-solute enthalpies derived from calorimetric solution enthalpies, solvent-solute interactions from molecular dynamics simulations, and the FTIR shifts in the carbonyl stretching corresponding to the solvent solute interaction. The three methods gave an overall order of solvent solute interactions increasing in the order toluene < ethyl acetate < alcohols. Thus, with the exception of FC in toluene, it is found that the nucleation difficulty increases with stronger binding of the solvent to the solute.

  • 40.
    Zhang, Shuo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Thermodynamics and Crystallization of the Theophylline-Glutaric Acid Cocrystal2013In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 13, no 3, p. 1153-1161Article in journal (Refereed)
    Abstract [en]

    This work investigates the thermodynamics and crystallization of the theophylline glutaric acid 1:1 cocrystal. It is found that the cocrystal physically decomposes at 120 degrees C (i.e., in the range between the melting points of the two pure compounds). The solubility of the cocrystal and pure compounds has been determined in chloroform and acetonitrile. In chloroform, the theophylline concentration of the saturated solution over the cocrystal is clearly higher than that in the saturated solution over pure theophylline I/II, while for glutaric acid the situation is the opposite. With the solubility data, the Gibbs free energy of the formation of the cocrystal from solid theophylline II and solid beta-glutaric acid at 30 degrees C can be estimated to -0.39 kJ mol(-1). The work reveals that polymorphism in the pure components of a cocrystal can dramatically influence the phase diagram and shift an incongruently dissolving case into a kinetically stabilized congruent case. In chloroform, the cocrystal dissolves incongruently with respect to the stable form I of theophylline but congruently with respect to the metastable theophylline II. However, the cocrystal is stable in a stoichiometric solution for more than 2 weeks. Given sufficient time, the system should transform into a solid phase being a mixture of cocrystal and stable theophylline I, in equilibrium with a solution that has the composition of the corresponding invariant point. In acetonitrile, where the glutaric acid solubility is much higher than that of theophylline II, the cocrystal dissolves, clearly incongruently. The region where the cocrystal is the only solid stable phase is clearly shifted toward the glutaric acid side and is fairly narrow. In both solvents the cocrystal can readily be produced by isothermal slurry conversion crystallization to a reasonable level of productivity, as long as the process is operated in a region of the phase diagram where the cocrystal is the only stable (or reasonably metastable) solid phase.

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