Glycine Crystals Research Articles

Controlling Characteristics of Glycine Crystals by Reactalyzer

Continuous crystallization is the next step of manufacturing especially at the production of pharmaceutical ingredients. We have developed small-scale continuous taylor-vortex crystallizer that is suitable for research in laboratory. But there was a problem that rotating inner cylinder at high-speed range causes much frictional heat and it raises the temperature of the solution, that may spoil the effort of controlling characteristics of crystals. So, we have developed new taylor-vortex crystallizer that has inner cooling system. We conducted several examinations of anti-solvent crystallization of glycine, which aims to obtain unstable crystal polymorph of glycine continuously. The new crystallizer showed the advantage of crystallizing unstable crystal polymorph.

Effects of Alizarin green dye in the growth, optical, mechanical and dielectric properties of glycine crystals

Effects of Alizarin green dye in the growth, optical, mechanical and dielectric properties of glycine crystals

Orientation-controlled crystallization of γ-glycine films with enhanced piezoelectricity.

Glycine, the simplest amino acid, is considered a promising functional biomaterial owing to its excellent biocompatibility and strong out-of-plane piezoelectricity. Practical applications require glycine films to be manufactured with their strong piezoelectric polar 〈001〉 direction aligned with the film thickness. Based on the recently-developed solidification approach of a polyvinyl alcohol (PVA) and glycine aqueous solution, in this work, we demonstrate that the crystal orientation of the as-synthesized film is determined by the orientation of glycine crystal nuclei. By controlling the local nucleation kinetics via surface curvature tuning, we shifted the nucleation site from the edge to the middle of the liquid film, and thereby aligned the 〈001〉 direction vertically. As a result, the PVA-glycine-PVA sandwich film exhibits the highest aver-age piezoelectric coefficient d33 of 6.13 ± 1.13 pC N-1. This work demonstrates a promising kinetic approach to achieve crystallization and property control in a scalable biocrystal manufacturing process.

Growth, structural, thermal and dielectric studies of a-glycine single crystals grown under the influence of potassium iodide for nonlinear optical applications

Glycine has the simplest structure among all amino acids. Many attempts have been made to grow different derivative crystals of glycine. However, the title compound was not investigated thoroughly to understand the usability of the crystal for its device application. In the present investigation, using slow evaporation solution growth technique, single crystals of glycine have been grown in the presence of potassium iodide. Detailed investigations were made on structural and thermal properties of the grown crystals. Structural analysis was carried out by X-ray diffraction method, Fourier Transform Infrared, FT-Raman and Nuclear Magnetic Resonance spectral methods to conform the grown crystals. Thermal stability of the grown crystals was studied by Thermogravimetric (TG) and Differential Thermal analysis (DTA) and it was found that the crystal is stable up to 113°C. UV-Vis spectral analysis has been carried out and the crystal has not any significant absorbance in the entire visible region. Dielectric studies for the grown samples have also been studied. Nonlinear optical property has been confirmed by Kurtz powder technique and found that the grown crystal has nearly fifty percentage of SHG efficiency as that of standard KDP sample. The observed properties have confirmed that the grown crystal is suitable for nonlinear optical applications. Copyright © 2017 VBRI Press.

Raman scattering and luminescence in single crystals of the amino acid glycine C2H5NO2 with an admixture of croconic acid C5H2O5

Single crystals of the amino acid glycine (Gly) C2H5NO2 doped with croconic acid (CA) C5H2O5 were synthesized by evaporation from an aqueous solution. The crystals grow in the form of hexagonal pyramids or thin plates. Analysis of polarized Raman scattering spectra (excitation wavelength of 532 nm) measured at room temperatures showed that crystals in the form of pyramids corresponded to γ-polymorph (γ-Gly), and crystals in the form of plates to α-polymorph of glycine (α - Gly). The presence of croconic acid molecules in the crystals is confirmed by the change in their color from white in pure Gly crystals to light or dark yellow, characteristic of CA crystals, as well as the presence of weak lines corresponding to CA in the Raman spectra. In single crystals of both Gly:CA polymorphs, strong green luminescence significantly exceeding the intensity of Raman scattering is observed in the range 400 - 700 nm with a maximum at 510 nm (2.44 eV) upon excitation at λ= 325 nm.

Monitoring Crystallization Processes in Confined Porous Materials by Dynamic Nuclear Polarization Solid-State Nuclear Magnetic Resonance.

Establishing mechanistic understanding of crystallization processes at the molecular level is challenging, as it requires both the detection of transient solid phases and monitoring the evolution of both liquid and solid phases as a function of time. Here, we demonstrate the application of dynamic nuclear polarization (DNP) enhanced NMR spectroscopy to study crystallization under nanoscopic confinement, revealing a viable approach to interrogate different stages of crystallization processes. We focus on crystallization of glycine within the nanometric pores (7–8 nm) of a tailored mesoporous SBA-15 silica material with wall-embedded TEMPO radicals. The results show that the early stages of crystallization, characterized by the transition from the solution phase to the first crystalline phase, are straightforwardly observed using this experimental strategy. Importantly, the NMR sensitivity enhancement provided by DNP allows the detection of intermediate phases that would not be observable using standard solid-state NMR experiments. Our results also show that the metastable β polymorph of glycine, which has only transient existence under bulk crystallization conditions, remains trapped within the pores of the mesoporous SBA-15 silica material for more than 200 days.

Understanding the Salt-Dependent Outcome of Glycine Polymorphic Nucleation.

The salt-dependent polymorphs of glycine crystals formed from bulk solutions have been a longstanding riddle. In this study, in order to shed fresh light, we studied the effects of seven common salts on primary nucleation of the metastable α-glycine and the stable γ-glycine. Our nucleation experiments and in-depth data analyses enabled us to reveal that (NH4)2SO4, NaCl and KNO3, in general, promote γ-glycine primary nucleation very significantly while simultaneously inhibiting α-glycine primary nucleation, thereby explaining why these three salts induce γ-glycine readily. In comparison, Ca(NO3)2 and MgSO4 also promote γ-glycine and inhibit α-glycine primary nucleation but not sufficiently to induce γ-glycine. More interestingly, Na2SO4 and K2SO4 promote not only γ-glycine but also α-glycine primary nucleation, which is unexpected and presents a rare case where a single additive promotes the nucleation of both polymorphs. As a result, the promoting effects of Na2SO4 and K2SO4 on γ-glycine do not enable γ-glycine nucleation to be more competitive than α-glycine nucleation, with γ-glycine failing to appear. These observations help us to better understand salt-governed glycine polymorphic selectivity.

Evolving NLO effect, mechanical, thermal, and dielectric study of N-Benzoyl glycine doped L-Threonine

Single Crystals of N-benzoyl glycine doped L-Threonine organic nonlinear optical materials was grown by slow evaporation technique at room temperature. The X-ray diffraction analysis confirms that crystals belong to the orthorhombic structure. The UV–Visible absorption spectra study was performed to reveal the optical behavior of the grown crystals. The bonding structures were analyzed and also the functional groups present in crystals were identified using FTIR spectrum. Kurtz-Perry powder technique employing Nd-YAG laser was utilized to find the SHG efficiency of grown crystals, which is compared with that of KDP. The dielectric constant and dielectric loss are measured as a function of frequency. The Vickers micro hardness test and TGA study gives the mechanical and thermal behavior of the material.

Ethanol-free antisolvent crystallization of glycine by liquefied dimethyl ether

Liquefied dimethyl ether (DME) was employed as an antisolvent to crystallize glycine from its aqueous solution. The proposed method can be performed at 20–25 °C and has the potential to reduce the energy consumption of drying or crystallizing using ethanol. α-Glycine crystals were successfully obtained from glycine aqueous solutions by mixing in liquefied DME, which was easily removed from the crystals by decompression. Contact with a liquefied DME/water mixture and small γ-glycine crystals resulted in the α-glycine converting to γ-glycine. This was only observed for saturated glycine solutions. We speculated that this conversion occurs via a solution-mediated transition. Pure liquefied DME is not capable of promoting solvent-mediated transitions, so saturated glycine solutions treated with the pure antisolvent can give α-glycine as the sole product.

Exploiting the Surface Properties of Graphene for Polymorph Selectivity.

Producing crystals of the desired form (polymorph) is currently a challenge as nucleation is yet to be fully understood. Templated crystallization is an efficient approach to achieve polymorph selectivity; however, it is still unclear how to design the template to achieve selective crystallization of specific polymorphs. More insights into the nanoscale interactions happening during nucleation are needed. In this work, we investigate crystallization of glycine using graphene, with different surface chemistry, as a template. We show that graphene induces the preferential crystallization of the metastable α-polymorph compared to the unstable β-form at the contact region of an evaporating droplet. Computer modeling indicates the presence of a small amount of oxidized moieties on graphene to be responsible for the increased stabilization of the α-form. In conclusion, our work shows that graphene could become an attractive material for polymorph selectivity and screening by exploiting its tunable surface chemistry.

Investigation of Metastable Zones and Induction Times in Glycine Crystallization across Three Different Antisolvents

Experimental data on the effects that different antisolvents and antisolvent addition strategies have on nucleation behavior in antisolvent crystallization is very limited, and our understanding of...

Synthesis of γ-Glycine-NLO active single crystals via assisted of lithium iodide and L-Proline template and determination of micro-structural and optical parameters

The crystallization of glycine using distinctive inorganic salts of lithium iodide (Li) and L-Proline (amino acids) template on solution-intermediate polymorphic conversion from metastable α-glycine to firm γ-glycine was studied. The presence of L-Proline with minimal content of Li salts expedites γ-glycine nucleation to a large degree in slow evaporation technique. The structural parameter of γ-glycine was confirmed by single crystal XRD and its microstructure was investigated via powder XRD. UV spectrum exhibits the high transparency at visible and near IR range and their optical constant values also analysed. The second harmonic generation measurements perceived owning NLO efficiency as 0.75 & 1.1 times that of KDP and hence it can be a potential material for the frequency doubling process.

Comments on “Investigation on novel bulk size single crystal of Glycine with metal ions grown by solution growth method for photonic applications”

The authors of the title paper (Materials Letters 257 (2019) 126674) report to have grown a glycine potassium dichromate (GPDC) single crystal by slow evaporation of an aqueous solution containing equimolar quantities of glycine and potassium dichromate. In this comment, many points of criticism, concerning the crystal growth and experimental data for this so-called GPDC crystal are discussed to prove that it is a dubious material.

Development of quantifying supersaturation to determine the effect of the anti-solvent on precipitation in liquid-liquid interfacial crystallization

Abstract Crystallization has been used in various industries to separate solid materials from solutions. The transition from the liquid phase to the solid phase occurs because the solubility decreases upon cooling, evaporation, and the addition of anti-solvents. Properties of solid materials are generally controlled by changing the driving force or supersaturation, which can be freely changed by operating factors such as the cooling rate and addition rate of anti-solvent. Recently, spherical crystallization has been developed as a new process for creating functional particles. In spherical crystallization, counter-diffusion between anti-solvent and water increases supersaturation and promotes crystallization. However, the supersaturation during spherical crystallization is particularly difficult to control because quantifying the rate of mass transfer between two liquids is difficult. The present work proposes a calculation method for quantifying the supersaturation in spherical crystallization. NaCl and glycine crystals were prepared with organic solvents, and the amount of precipitation was measured. The effect of the anti-solvent on the amount of precipitation was investigated. These results revealed that the amount of NaCl and glycine precipitation can be described by the supersaturation distribution inside the droplets in comparison with numerical calculations.

Effect of alcohol/water on glycine crystal transition

Glycine has three crystalline polymorphs (unstable β-type, metastable α-type and stable γ-type). Since glycine crystals have different physical properties such as solubility and stability depending on polymorphism, and the control of polymorphic selectivity is required in the manufacturing process of pharmaceuticals and foods. In this study, the unstable β-type crystals obtained by anti-solvent crystallization was focused as a starting material. Liquid phase water mixed with alcohol was brought into contact with β-type crystals, and the effect of the mixing ratio of water with alcohol around the crystals on the transition was investigated. As a result, it is clarified that the proportion of water in liquid phase alcohol/water has a large influence on the polymorphic selectivity of glycine crystals.

Fast Continuous Non-Seeded Cooling Crystallization of Glycine in Slug Flow: Pure α-Form Crystals with Narrow Size Distribution

Glycine has been widely used as pharmaceutical excipients and synthesis reagents, and commercial glycine has a significant amount of aggregation and wide particle size distribution. A simple but reproducible process for generating uniform glycine crystals is always desired for both product quality and process efficiency purposes. Continuous cooling crystallization of glycine has been carried out in air-liquid slug flow in millimeter ID tubing, starting from solution without using seeds. Slugs were formed by combining air and liquid streams, then went through the crash cooling zone of varying lengths (tubing length in contact with ice bags). The operational boundaries of crash cooling times were evaluated: natural cooling (lower bound, no crash cooling), maximum cooling time for pure α-form without aggregation (upper bound), and beyond upper bound. Non-aggregating pure α-form glycine crystals were continuously generated within ~ 10 min, feasible from multiple conditions (combinations of crashing cooling time and starting concentration). When crash cooling time further increases (while maintaining the starting concentration), crystal aggregations and/or γ-form crystals could appear. Reducing starting concentration can allow longer crash cooling time without widening product crystal size distribution or reducing crystalline form purity. At proper conditions, even natural cooling in slugs can nucleate and grow non-aggregated pure α-form crystals. All cooling conditions carried out in slug flow generally minimize needle-shaped crystals compared with corresponding batches. Glycine crystals of α-form and narrow size distribution can be continuously generated within 10 min from cooling crystallization in millimeter-sized slug flow, without using external seeds nor adding solvent/additives. And, the operational boundaries of crash cooling time (at proper starting concentrations) for pure α-form non-aggregating product crystals are identified.

Glycine-Chitosan-Based Flexible Biodegradable Piezoelectric Pressure Sensor.

This paper presents flexible pressure sensors based on free-standing and biodegradable glycine–chitosan piezoelectric films. Fabricated by the self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of a stable spherulite structure of β-glycine (size varying from a few millimeters to 1 cm) embedded in an amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms formation of a pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent-casting method can be used to prepare a biodegradable β-glycine/chitosan-based piezoelectric film with sensitivity (∼2.82 ± 0.2 mV kPa–1) comparable to those of nondegradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range from 0.26 to 0.12 nF at a frequency range from 100 Hz to 1 MHz, and its dielectric constant and loss factor are 7.7 and 0.18, respectively, in the high impedance range under ambient conditions. The results suggest that the glycine–chitosan composite is a promising new biobased piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.

Potential Prebiotic Relevance of Glycine Single Crystals Enclosing Fluid Inclusions: An Experimental and Computer Simulation with Static Magnetic Fields

Glycine crystallizes into three different polymorphs called α, β and γ under standard physicochemical conditions. They have different features depending on their structural variations. The possible interaction of glycine with magnetic minerals in meteorites and comets or in the ancient Earth, paves the way to study the self-assembly and molecular behavior under irradiation and magnetic conditions. The magnetic field might induce the formation of a specific polymorph of glycine. To gain insight on the consequences of gamma irradiation with a gradient of static magnetic fields (0.06 T, 0.3 T, 0.42 T and 0.6 T) on the self-assembly of single macroscopic glycine crystals, we gamma irradiated the powdered amino acid and then assembled single crystals from water solutions. The preliminary results showed a stable formation of fluid inclusions in the single crystals and no straightforward effect on the self-assem- bly process after glycine gamma irradiation and interaction with static magnetic fields. The α glycine polymorph single crystals formed at 55° from the magnetic longitudinal axis and seemed to be enhanced by gamma radiation. The γ-glycine single crystals presented L and D circular dichroism signals, whereas the irradiated samples presented no circular dichroism bands. Com- puter simulations suggest different catalytic properties from α and γ glycine crystals.

Polymorph evolution during crystal growth studied by 3D electron diffraction.

3D electron diffraction (3DED) has been used to follow polymorph evolution in the crystallization of glycine from aqueous solution. The three polymorphs of glycine which exist under ambient conditions follow the stability order β < α < γ. The least stable β polymorph forms within the first 3 min, but this begins to yield the α-form after only 1 min more. Both structures could be determined from continuous rotation electron diffraction data collected in less than 20 s on crystals of thickness ∼100 nm. Even though the γ-form is thermodynamically the most stable polymorph, kinetics favour the α-form, which dominates after prolonged standing. In the same sample, some β and one crystallite of the γ polymorph were also observed.

New stable phases of glycine crystals

A Density Functional Theory (DFT) study of the electronic, energetic, dynamical, and mechanical properties of new glycine molecular crystals is presented here. Our search of the potential energy surface (PES) reproduces the previously reported structures for α-, β-, and γ-glycine with P21/n,P21,P31 symmetries, respectively. In addition, we report three new orthorhombic (o), tetragonal (t), and monoclinic (m) crystals with P212121,P43, and P21 symmetries. The crystals have wide band gaps, classifying them in the range of insulators. All three new phases have low mechanical hardness (< 3.2 GPa), characterizing them as soft crystals. Topological and local energetic properties of the electronic densities for the new crystalline phases of glycine have been calculated using the tools provided by the quantum theory of atoms in molecules (QTAIM) under periodic conditions. Typical NH⋯O, OH⋯O as well as secondary CH⋯O hydrogen bonds (HBs), act as the stabilizing factors resulting in large cohesive energies for the new phases of glycine crystals. Without exception, all types of HBs, for all new phases, perfectly fit the attractive region of a Lennard-Jones potential.