Crystal Solution Research Articles

Two-step nucleation and growth of crystals in a metastable solution with mass exchange with the environment

Two-step nucleation and growth of crystals in a metastable solution with mass exchange with the environment

Polymerization-induced ultrafast and massive growth of colloidal photonic crystals on hydrogel surface

Structural color materials based on colloidal photonic crystals (CPCs) have been extensively investigated since they can be prepared efficiently. Commonly, photonic hydrogels are prepared by a polymerizing pre-gel solution, in which colloids are self-assembled by passive methods. Except for magnetic colloids, the process of forming colloidal photonic crystals in a pre-gel solution requires hours to days, and it is almost impossible to assemble the colloids directly in hydrogels. Here, we present a mild strategy to prepare hydrogels with surface structural color, ordered colloidal arrays are formed at the air-hydrogel interface actively during the polymerization process, and bright structural color forms in minutes on a large scale. Polymer exclusion is the key driving force for the assembly of the colloids, other factors, such as evaporation flux, can also promote the colloids to assemble. Significantly, heterogeneous structural color patterns can be produced easily by exposing the hydrogel surface to air sequentially using a mask during the polymerization process. The simple and fast method provides a general route for preparing structural colored surfaces, which may be suitable for various applications.

Sustainable separation of molybdenum from mixed mineral acids generated as semiconductor industry waste streams using tributyl phosphate (TBP) by effects of hybrid machine learning models

This study explores the separation and optimization of molybdenum (Mo) from mixed mineral acids derived from semiconductor industry waste streams with tributyl phosphate (TBP) by implementing machine learning (ML) models. Considerable experimental tests were performed to evaluate the impact of various operational variables on the effectiveness of Mo extraction and stripping. The support vector regression (SVR) paired with harmony search algorithm (HSA), genetic algorithm (GA), and shuffled frog leaping algorithm (SFLA) were employed for enhancement in the separation process and structural optimization. The SVR-SFLA model yielded the most meticulous predictions, identifying optimal extraction conditions with a TBP concentration, mixing time, temperature, and O/A ratio of 50%, 30 min, 25 °C, and 1, respectively, achieving 77.8% efficiency. The derived results from the SVR-SFLA model, in tandem with the McCabe-Theil diagram, indicated a four-stage counter-current extraction process required to achieve a yield exceeding 99%. For the stripping process, the hybrid model indicated optimal conditions with 3 M NH4OH and an A/O ratio of 0.5 at 50 °C for 20 min, requiring two counter-current stages for nearly complete stripping. Feature importance analysis using a random forest algorithm (RFA) highlighted the NH4OH concentration and phase ratio as the most significant factors, contributing 40.3% and 29.1%, respectively, to the stripping from the loaded TBP phase. The final product, obtained after crystallization and thermal decomposition of the strip solutions, was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), revealing 99.74% purity for molybdenum trioxide.

[formula omitted] Affects the crystalline calcium silicate hydrate minerals synthesized by fly ash-based silicon extraction solution and lime milk

When extracting amorphous silicon from fly ash using a strong alkaline solution, other elements such as Al also enter the silicon extraction solution in the form of AlOH4−. To systematically investigate the impact of AlOH4− on the synthesis of typical calcium silicate hydrate crystals in a silicon extraction solution, a specific amount of AlOH4− was added to the silicon extraction solution, and calcium silicate was hydrothermally synthesized at 90℃ and 230℃. Scanning electron microscopy (SEM) and Brunner−Emmet−Teller (BET) analysis revealed that with the increasing in AlOH4− content, microporous calcium silicate gradually loses its microporous morphology. While the specific surface area shows no significant change, the median pore diameter first increases from 1.47 nm to 1.58 nm and then decreases to 1.55 nm. The xonotlite fibers underwent a gradual refinement, diminishing from 0.28 to 0.15 µm. Simultaneously, the specific surface area increases from 28.87 to 56.8 m2/g. At an AlOH4− concentration of 3 mol/L, the microscopic morphology transforms into a sheet-like structure. X-ray diffraction (XRD) analysis reveals that AlOH4− promotes the formation of tobermorite while inhibiting the further development of calcium silicate. Additionally, Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance indicate that Al can replace Si in the calcium silicate hydrate system, primarily substituting positions the Q2 and Q3 sites. Qualitatively, it is suggested that with the increasing incorporation of Al, the polymerization degree of the silicon-oxygen tetrahedra decreases. According to experimental results, the concentration of AlOH4− should be below 0.05 mol/L when synthesizing microporous calcium silicate hydrate and less than 0.2 mol/L when synthesizing fibrous xonotlite-type calcium silicate hydrate.

Study on the Performance of a Novel Double-Section Full-Open Absorption Heat Pump for Flue Gas Waste Heat Recovery

Open absorption heat pumps are considered one of the most promising methods for efficiently utilizing low-grade waste heat, reducing energy consumption, and lowering greenhouse gas emissions. However, traditional heat pumps have significant limitations in the range of flue gas temperatures they can recover, and their relatively low system performance further restricts practical applications. In this study, we propose a novel double-section full-open absorption heat pump driven by flue gas from the desulfurization tower. By designing the absorber with a double-layer structure, the system can recover more latent and sensible heat from the flue gas, significantly enhancing its thermal recovery capability. Additionally, replacing the traditional LiBr/H2O working pair with LiCl/H2O significantly reduces the risks of solution crystallization and equipment corrosion. Through comprehensive research, the strengths and weaknesses of the system were explored. The results indicate that this system effectively recovers flue gas waste heat within the temperature range of 30–70 °C. Specifically, at a flue gas temperature of 70 °C and a flow rate of 3 kg/s, the system achieves a COP of 1.838, along with a heating capacity of 158.83 kW and a ROI of 34.1%. These metrics demonstrate that the system not only delivers high performance but also exhibits excellent economic viability. Additionally, when the solution temperature is lowered to 10 °C, the system’s maximum COP reaches 1.96, reflecting a significant 30.67% improvement over traditional heat pumps. These findings highlight the system’s potential for application in coal-fired power plants, where varying levels of power output can benefit from enhanced thermal recovery and efficiency.

Exact analytical solution of the equations for a quasiequilibrium two-phase domain: permeability and interdendritic spacing

This study is concerned with the theoretical description of a quasi-stationary process of directional crystallization of binary melts and solutions in the presence of a quasi-equilibrium two-phase region. The quasi-equilibrium process is ensured by the fact that the system supercooling is almost completely compensated by heat released during the phase transformation. Quasi-stationarity of the process determining constancy of the crystallization rate is ensured by given temperature gradients in the solid and liquid phases. The system of heat and mass transfer equations and boundary conditions to them under these assumptions is dependent on a single spatial variable in the reference frame moving with the crystallization rate relative to a laboratory coordinate system. Exact analytical solutions to the formulated problem in parametric form are obtained. The parameter of the solution is the solid phase fraction in a two-phase region. The distributions of temperature and impurity concentration in the solid, liquid and two-phase regions of the crystallizing system, the rate of solidification, and the spatial coordinate in the two-phase region depending on the solid phase fraction in it are found. An algebraic equation for the solid phase fraction at the interface between the solid material and the two-phase region is derived. Exact analytical solutions show that the impurity concentration in the two-phase layer increases as the solid phase fraction increases. Moreover, the solid phase fraction at the interface solid phase — two phase region and its thickness increase as the temperature gradient in the solid phase and the solidification rate increase. The developed theory allows us to determine analytically the permeability of the two-phase region and a characteristic interdendritic spacing in it. Analytical solutions show that the relative permeability in the two-phase region increases from a certain value at the interface with the solid phase to unity at the interface with the liquid phase. The selection theory of stable dendritic growth allows us to determine analytically a characteristic interdendritic distance in the two-phase layer that decreases as the temperature gradient in the solid phase increases. An increase of impurity in the molten phase gives a decrease in the interdendritic spacing within a two-phase region.

Crystallization ripening and erosion of calcium oxalate under the effect of bacteria and a polymer materials surface.

As typical examples of pathological biomineralization, urinary stones and stent encrustation have been associated with bacteria, yet the underlying mechanisms remain unclear. In this study, the effect of Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus on the nucleation and growth of calcium oxalate crystals both in solution and on material surfaces in vitro was investigated. Both bacteria can promote calcium oxalate crystallization, and E. coli shows a prominent ability to boost the nucleation and growth rate. Interestingly, we discovered an Ostwald ripening phenomenon after the initial nucleation on the material surfaces, where larger particles emerge upon the disappearance of small nuclei particles, evident in the case of S. aureas. Over an extended period of time, erosion and disintegration of the crystals was observed when bacteria were involved. Based on these understandings, we developed a new functional surface by synthesizing an antibacterial polypeptoid in-house and utilizing polyurethane as the substrate material. This surface exhibits a synergistic effect that inhibits the formation of calcium oxalate crystals. This study helps to elucidate the role of bacteria in calcium oxalate biomineralization and supports further development of treatment approaches such as anti-encrustation polymer materials.

Single‐Luminophore Molecular Engineering for Rapidly Phototunable Solid‐State Luminescence

Smart materials enabling emission intensity or wavelength tuning by light stimulus attract attention in numerous cutting‐edge fields. However, due to the generally dense molecular stacking against photoresponsivity in solid states, especially in crystals, developing rapidly phototunable solid‐state luminescent systems remains challenging. Herein, we propose a new luminophore that serves as both a photoresponsive unit and a luminescent group, while possessing enhanced conformational freedom to provide a solution. Namely, photoexcitation‐induced molecular conformational change of an ionized persulfurated arene based on weak intermolecular aliphatic C–H···π interaction was employed. On these basis, rapidly enhanced phosphorescence upon irradiation can be observed in a series of phase states, like solution state, crystal, and amorphous state, especially with a high photoresponsive rate of 0.033 s‐1 in crystal state that is superior to the relevant reported cases. Moreover, a rapidly phototunable afterglow effect is achieved by extending this molecule into some polymer‐based doping systems, endowing the system with unique dynamic imaging and fast photopatterning capabilities. Such a single‐luminophore molecular engineering and the underlying mechanism have implications for building different condensed functional materials, principally for those with stimuli responses in solid states.

Scaling behavior of cation exchange membrane induced by Ca2+ during the electrodialysis for enriching lithium-containing solutions

Membrane fouling, particularly Ca2+-induced scaling on cation exchange membranes (CEM), hinders the application of electrodialysis in lithium extraction. This study investigated the fouling mechanisms of Ca2+ coexisting with Cl− and SO42− on sulfonated CEM, using CaCl2 and CaSO4 solution as the targeted foulants. The conductivity, pH, turbidity, particle size distribution, chemical composition and morphology of the membrane surface were monitored to verify the evolution of the bulk solution and the membrane during the Ca2+-induced fouling. Online detection of conductivity and pH revealed distinct trends in fouling solutions containing Ca2+-Cl- and Ca2+-SO42-. Noticeable changes in turbidity and particle distribution were observed in the concentrated chamber of the highly saturated Ca2+-SO42- solution, whereas the concentrated chamber of the Ca2+-Cl- solution showed turbidity and particle size distribution similar to the initial values. SEM showed that there are different morphologies of scaling crystals in the two types of solution. These fundamental differences are the root cause of the distinct fouling mechanisms between the Ca2+-Cl- solution and Ca2+-SO42- solution. To further investigate the fouling mechanisms, the electrochemical impedance spectroscopy (EIS) was employed to differentiate the impedance of the electric double layer and diffusion layer, providing insights into the characteristics of the CEM-solution interfaces fouled by different lithium-containing solutions. Additionally, adsorption experiments, quartz crystal microbalance with dissipation (QCM-D) and computational simulations (COMSOL, DFT) were conducted to provide detailed insights into the effects of fouling solutions on the properties of the desalted solution, the probability of crystal precipitation, and particularly the interaction between Ca2+ and the functional sites on the CEM. Finally, the Ca2+-induced scaling mechanism of CEM for enriching the lithium-containing solutions with and without SO42− was proposed, elucidating the synergistic effects of Ca2+-induced crystallization in the bulk solution and Ca2+ adsorption on the CEM surface. The research results could offer theoretical guidance for developing pollution control strategies.

Excipient effects on supersaturation, particle size dynamics, and thermodynamic activity of multidrug amorphous formulations

Multidrug formulations enhance patient compliance and extend the life cycle of pharmaceutical products. To overcome solubility challenges for multidrug combinations, amorphous formulations are commonly used. However, the excipients for creating amorphous formulations are often selected without an understanding of their effects on the bioavailability of the drugs. In this context, we investigated the impact of three types of excipients (polymers, surfactants and amino acids) on the supersaturation and thermodynamic activity of multidrug amorphous formulations. Additionally, we studied the particle size dynamics of the colloidal phase formed as a result of liquid–liquid phase separation. The amorphous solubility of two drugs, atazanavir and ritonavir, was determined in solutions containing predissolved excipients and the particle size dynamics of the colloidal particles was measured by dynamic light scattering. Dissolution experiments of atazanavir and ritonavir were conducted in predissolved sodium dodecyl sulfate (SDS), an anionic surfactant, and alanine solutions under non-sink conditions. Membrane transport of the drugs was evaluated using a MicroFLUX setup. The polymers had only minor effects on the amorphous solubility, but SDS significantly increased the solubilities of both drugs. In contrast, the other non-ionic surfactants and amino acids reduced the solubility of atazanavir but had no negative effect on ritonavir. Polymers were effective in maintaining supersaturation and preventing the coarsening of the colloidal particles. Conversely, alanine was neither able to inhibit the solution crystallization nor increase the flux of either drug. Despite the increase in the amorphous solubility of both drugs in SDS, flux was reduced. These results highlight the importance of properly selecting excipients for supersaturating amorphous formulations. The choice of excipient impacts the thermodynamic activity, the phase behaviour of the drugs and hence, the resulting absorption after oral intake.

Study on water-salt phase transition of saline soils during freezing

As the temperature decreases, when the freezing temperature is reached, the solution in the pores of saline soil undergoes ice crystallization and salt crystallization phenomena. Theoretical and experimental studies have been carried out in order to investigate the behaviour of water-salt phase transitions within the pores of saline soils. Firstly, the theoretical expression for the initial crystallization radius is given from the thermodynamic theory by considering the interphase chemical potential equilibrium and the Young-Laplace equation, and the relationship between the initial crystallization radius and temperature as well as the initial salt content is analyzed. Then, a theoretical model to predict the pore solution content and crystal content was developed in conjunction with the Van Genuchten soil-water characteristic curve model, and the water-salt phase transition behaviour of saline soils was analyzed by numerical calculations. Finally, the validity of the theoretical model was verified by a saline soil freezing test. The results show that the water-salt phase transition behaviour of the solution within the pores of saline soils is affected by temperature and initial salt content, and the water-salt phase transition behaviour mainly occurs at the early stage of freezing. Salt lowers the freezing temperature of the soil; the higher the salt content, the lower the freezing temperature, and the presence of salt inhibits the growth of ice crystals. As the temperature decreases, the precipitation of ice salt crystals during the phase transition of the soil pore solution reduces the soil porosity and decreases the channels for ion migration, resulting in a gradual increase in the soil pore volume ratio.

Unveiling spectroscopic behaviour and molecular features (DFT studies) of Exemestane-maleic acid cocrystal as model multicomponent system

The present study aimed to investigate the Exemestane - maleic acid (Ex-Mal) cocrystal using Fourier-transform Raman (FT-Raman), Fourier-transform Infrared (FT-IR), Powder X-ray Diffraction (PXRD) and Differential Scanning Calorimeter (DSC) experimental techniques and quantum chemical calculations. Exemestane (Ex) is an irreversible aromatase inhibitor, clinically used for the treatment of postmenopausal women having primary or advanced breast cancer. Maleic acid (Mal), a dicarboxylic acid is found in many vegetables and fruits and is used as a food additive and sweetener. Solution crystallization of Ex and Mal was done in the generation of Ex-Mal cocrystal (1:1). PXRD and DSC analysis confirmed the successful generation of Ex-Mal Cocrystal. Intermolecular hydrogen bonding (O4-H12···O13 & C8-O3···H36) also suggested the formation of a multi-component system, Ex-Mal cocrystal (1:1), as the respective modes shifted in the vibrational (Raman & IR) spectra of cocrystal than the Ex. Further, the quantum theory of atoms in molecules (QTAIM) has been done to analyze the strength and nature of inter-/intra molecular hydrogen bonding. Natural bond orbital (NBO) analysis was performed to check the stabilization energy of the system. The frontier molecular orbital (FMO) analysis predicted that Ex-Mal cocrystal is more reactive and less stable than Ex. Molecular electrostatic potential (MEP) surface showed that electrophilic (C16-H36)/(O4-H12), and nucleophilic (C8=O3)/(C17=O13) reactive groups in Ex/Mal and Mal/Ex, respectively, neutralized after the formation of Ex-Mal cocrystal, confirming the presence of hydrogen bonding interactions (C16-H36∙∙∙O3=C8) and (C17=O13∙∙∙H12-O4). Molar Refractivity (MR) was calculated to check the drug-likeness behaviours of Ex-mal cocrystal. This study provided a comparison of experimental and theoretical results to understand the hydrogen bonding interactions and structural activity of the system.

Prevention of Crystal Agglomeration: Mechanisms, Factors, and Impact of Additives

Crystal agglomeration is a common phenomenon for most chemicals and pharmaceuticals. The formation of agglomerates usually lowers product purity and generates a broad particle size distribution. This review focuses on preventing agglomeration in solution crystallization, the storage of crystals, and pharmaceutical preparation processes. The agglomeration mechanisms in these stages are analyzed and the effects of operating parameters are summarized. Furthermore, effective control means related to the crystallization environment are elaborated, including solvents, ultrasound, and additives. Special attention is paid to the influence of additives in preventing the aggregation of both suspensions and dried powders. Besides additives used in solution crystallization, the roles of anti-caking agents, stabilizers of nanosuspensions, and excipients of solid dispersions are also discussed. The additive type and properties like hydrophilicity, hydrophobicity, ionic strength, viscosity, the steric hindrance effect, and intermolecular interactions between additives and crystals can greatly affect the degree of agglomeration.

What matters for drug delivery to tumor by nanoparticles: Gaining insights from PBPK/PD simulation of drug nanocrystals

Background and purpose: In our previous studies, drug nanocrystals were directly prepared by solution crystallization, possessing uniform particle size and morphology suitable for intravenous (IV) injection. These nanocrystals accumulated in a small percentage of their injected dose in tumor-bearing mice but showed similar anti-tumor effectiveness and much-reduced side effects compared with current commercial solubilized and encapsulated delivery systems. Experimental approach: In this study, we aimed to delineate possible controlling factors for the pharmacokinetics (PK) and biodistribution behaviors of paclitaxel (PTX) nanocrystals tested in mice by applying physiologically based pharmacokinetics (PBPK) modeling, coupled with pharmacodynamics (PD) simulation, to the data. Key Results: Our results show that clearance of the drug plays a significant, if not the most important, role in determining tissue distribution, including tumor accumulation of PTX nanocrystals. Surface treatment of drug nanocrystals with polymeric surfactants also appeared to affect PK profiles and PD outcomes. Importantly, when scaled to model human parameters, our PK/PD simulations suggest that drug distribution in humans, as opposed to animal models, was significantly influenced by tissue partitioning rather than drug clearance. This finding could facilitate the design and development of future drug delivery systems. Conclusion: Drug nanocrystals deposited in tissues, including tumors, could therefore act as depots, releasing the drug back into the circulation, possibly contributing to extended treatment, as well as any detrimental effects.

Unexpected tunable photoluminescence and emission mechanism during the gradual increase of cyclic glucose units

Excitation-dependent (λex-dependent) emission is one of the most common emission characteristics of nonconventional luminophores. Previously, we have reported D-xylose crystals has an obvious λex-dependent color tunable persistent room temperature phosphorescence (p-RTP) from blue to green, but its p-RTP emission at long wavelength is very weak. To further explore this attractive multicolor p-RTP behavior, and to enhance its tunability, the photoluminescence (PL) behavior of three common cyclodextrins (CDs), namely α-CD, β-CD and γ-CD, including solution and single crystals, were studied. Their single crystals demonstrate λex-dependent multicolor p-RTP properties in the order of β-CD>α-CD>γ-CD, rather than the strongest with the least glucose units (α-CD). Among them, the λex-dependent tunable p-RTP of β-CD and α-CD is superior to that of D-(+)-xylose single crystal. The above unexpected phenomena could be explained reasonably through detailed single crystal structure analysis and theoretical calculations. The emission behavior of solution and single crystals of CDs can be reasonably explained by the clustering-triggered emission (CTE) mechanism. Furthermore, CD-based covalent organic frameworks (COF) and supramolecules are readily fabricated, which own significantly enhanced p-RTP emission. Due to the intriguing PL property as well as hydrophilic rim and low biotoxicity of CDs, successful imaging of HCT116 cells and encryption applications were demonstrated. It is believed that the intrinsic PL properties of CDs, especially their regularly adjustable multicolor p-RTP that varies with the number of glucose units, have significant guidance for the development of a series of multicolor luminescent materials.

Biomimetic Synthesis of Calcium Carbonate in Bile in the presence of Amino Acids

Thermodynamic and experimental modeling of calcium carbonate crystallization in a model solution of human bile has been carried out. The process of calcium carbonate (calcite and vaterite) crystallization from solutions containing bile has been studied. It is shown that differences in the phase and group composition of the samples arise depending on the synthesis parameters. It has been established that in the presence of 1 wt. % bile, calcite is formed, and an increase in the concentration of bile in the initial solution from 5 to 100 wt. % contributes to the crystallization of vaterite. It is shown that the mass of the solid phase increases with an increase in the concentration of bile in the initial solution. The dissolution of the synthesized samples was performed in 0.9 wt. % NaCl solution and 0.05 M EDTA solution. It was found that the presence of bile components in the composition of solid samples reduces the rate of their dissolutions.

Unprecedented Packing Polymorphism of Oxindole: An Exploration Inspired by Crystal Structure Prediction.

Crystal polymorphism, characterized by different packing arrangements of the same compound, strongly ties to the physical properties of a molecule. Determining the polymorphic landscape is complex and time-consuming, with the number of experimentally observed polymorphs varying widely from molecule to molecule. Furthermore, disappearing polymorphs, the phenomenon whereby experimentally observed forms cannot be reproduced, pose a significant challenge for the pharmaceutical industry. Herein, we focused on oxindole (OX), a small rigid molecule with four known polymorphs, including a reported disappearing form. Using crystal structure prediction (CSP), we assessed OX solid-state landscape and thermodynamic stability by comparing predicted structures with experimentally known forms. We then performed melt and solution crystallization in bulk and nanoconfinement to validate our predictions. These experiments successfully reproduced the known forms and led to the discovery of four novel polymorphs. Our approach provided insights into reconstructing disappearing polymorphs and building more comprehensive polymorph landscapes. These results also establish a new record of packing polymorphism for rigid molecules.

Unprecedented Packing Polymorphism of Oxindole: An Exploration Inspired by Crystal Structure Prediction

AbstractCrystal polymorphism, characterized by different packing arrangements of the same compound, strongly ties to the physical properties of a molecule. Determining the polymorphic landscape is complex and time‐consuming, with the number of experimentally observed polymorphs varying widely from molecule to molecule. Furthermore, disappearing polymorphs, the phenomenon whereby experimentally observed forms cannot be reproduced, pose a significant challenge for the pharmaceutical industry. Herein, we focused on oxindole (OX), a small rigid molecule with four known polymorphs, including a reported disappearing form. Using crystal structure prediction (CSP), we assessed OX solid‐state landscape and thermodynamic stability by comparing predicted structures with experimentally known forms. We then performed melt and solution crystallization in bulk and nanoconfinement to validate our predictions. These experiments successfully reproduced the known forms and led to the discovery of four novel polymorphs. Our approach provided insights into reconstructing disappearing polymorphs and building more comprehensive polymorph landscapes. These results also establish a new record of packing polymorphism for rigid molecules.

Nucleation Control and Isolation of Polymorphic Forms of Aspirin through an Efficient Template‐Assisted Swift Cooling Process

AbstractAspirin, a commonly used pharmaceutical therapeutic pharmacological substance, exhibits cross‐nucleation (intergrowth or overgrowth) of stable polymorphic Form‐I over the preferably required metastable polymorphic Form‐II, which creates a bottleneck issue in the solution crystallization of aspirin in most organic solvents and their mixtures. Controlling the overgrowth phenomenon is a key factor for designing the pharmaceutical drug material aspirin with desired properties. Hence, our present work chose a novel template‐assisted swift cooling crystallization with selected templates like copper‐wire and nylon 6/6 polymer, and also N‐N‐Dimethylformamide (DMF) as a solvent. The pure solution in the absence and the presence of a nylon 6/6 template in all the experimental supersaturation ranges achieves only thermodynamically stable polymorphic Form‐I of aspirin with slightly different morphologies. Contrarily, the presence of a copper‐wire template induces both stable and metastable polymorphs of aspirin depending on the level of supersaturation in the mother solution. The effect of templates on the nucleation kinetics of aspirin polymorphs is estimated using classical nucleation theory, and the determined values exactly match with experimental results. The polymorphic nature of the grown crystals is ascertained by powder X‐ray diffraction (PXRD), single crystal X‐ray diffraction (SCXRD), and differential scanning calorimetry (DSC) analyses.

A New Polymorphic Form of Maltol: Crystallization and Structure Refinement

AbstractA new polymorph of maltol, a food and intermediate pharmaceutical material, is discovered through solution crystallization process using a mixed solvent of water and ethanol with l‐menthol as an additive. It belongs to monoclinic crystal system with lattice parameters: a = 7.136(8) Å, b = 24.23(3) Å, c = 7.020(8) Å, and β = 106.22(3)°, volume = 1165 (2) Å3 and the refinement factor is R = 6.64%. With single crystal X‐ray diffraction (SCXRD) data as input, the intermolecular interactions between the new polymorph of maltol is investigated through Hirshfeld surface analysis, the higher percentage of overall interaction between the polymorph (H…H) interaction, and the (O…H) interaction contributes more to the generation of new polymorph. The 2D finger print plot depicts the interactions are mainly due to the hydrogen bonds.