Research

20 pages, 45017 KiB

Open AccessArticle

Maleic Acid as a Co-Former for Pharmaceutically Active GABA Derivatives: Mechanochemistry or Solvent Crystallization?

by Daniel Komisarek, Ebru Taskiran and Vera Vasylyeva

Materials 2023, 16(6), 2242; https://doi.org/10.3390/ma16062242 - 10 Mar 2023

Cited by 1 | Viewed by 1483

In this study, we compare the mechanochemical and classical solvent crystallization methods for forming maleates of GABA and its pharmaceutically active derivatives: Pregabalin, Gabapentin, Phenibut, and Baclofen. Common characterization techniques, like powder and single crystal X-ray diffraction, IR-spectroscopy, differential scanning calorimetry, thermogravimetric analysis [...] Read more.

In this study, we compare the mechanochemical and classical solvent crystallization methods for forming maleates of GABA and its pharmaceutically active derivatives: Pregabalin, Gabapentin, Phenibut, and Baclofen. Common characterization techniques, like powder and single crystal X-ray diffraction, IR-spectroscopy, differential scanning calorimetry, thermogravimetric analysis and ¹H-NMR spectroscopy, are used for the evaluation of structural and physicochemical properties. Our work shows that maleate formation is possible with all investigated target compounds. Large increases in solubility can be achieved, especially for Pregabalin, where up to twentyfold higher solubility in its maleate compared to the pure form can be reached. We furthermore compare the mechanochemical and solvent crystallization regarding quickness, reliability of phase production, and overall product quality. A synthetic route is shown to have an impact on certain properties such as melting point or solubility of the same obtained products, e.g., for Gabapentin and Pregabalin, or lead to the formation of hydrates vs. anhydrous forms. For the GABA and Baclofen maleates, the method of crystallization is not important, and similarly, good results can be obtained by either route. In contrast, Phenibut maleate cannot be obtained pure and single-phase by either method. Our work aims to elucidate promising candidates for the multicomponent crystal formation of blockbuster GABA pharmaceuticals and highlight the usefulness of mechanochemical production routes. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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12 pages, 24486 KiB

Open AccessArticle

Structural Insights into Layered Tetrahalocuprates(II) Based on Small Unsaturated and Cyclic Primary Ammonium Cations

by Edi Topić and Mirta Rubčić

Materials 2023, 16(6), 2236; https://doi.org/10.3390/ma16062236 - 10 Mar 2023

Viewed by 907

Abstract

Layered hybrid halometallates represent a promising class of multifunctional materials, yet with many open challenges regarding the interaction between building blocks. In this work, we present a synthetic and analytical methodology for the efficient synthesis and structural analysis of a series of novel [...] Read more.

Layered hybrid halometallates represent a promising class of multifunctional materials, yet with many open challenges regarding the interaction between building blocks. In this work, we present a synthetic and analytical methodology for the efficient synthesis and structural analysis of a series of novel tetrahalocuprate(II) hybrids based on small alkylammonium cations. Observed robustness in geometrical motifs provided a platform for crystal structure determination, even from the complex laboratory powder diffraction data. The slight differences in inorganic layer geometry and severe differences in organic bilayer packing are quantified using well-established descriptors for these materials, and dependences of geometric parameters on anion and cation choice are accounted for. Temperature dependence of structural parameters for one of the tetrachlorocuprate hybrids that was chosen as a model unveils a possible geometrical origin of thermochromism in these materials. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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17 pages, 6818 KiB

Open AccessArticle

Determination of Particle Size Distributions of Bulk Samples Using Micro-Computed Tomography and Artificial Intelligence

by Stefan Höving, Laura Neuendorf, Timo Betting and Norbert Kockmann

Materials 2023, 16(3), 1002; https://doi.org/10.3390/ma16031002 - 21 Jan 2023

Cited by 3 | Viewed by 1560

Abstract

The knowledge of product particle size distribution (PSD) in crystallization processes is of high interest for the pharmaceutical and fine chemical industries, as well as in research and development. Not only can the efficiency of crystallization/production processes and product quality be increased but [...] Read more.

The knowledge of product particle size distribution (PSD) in crystallization processes is of high interest for the pharmaceutical and fine chemical industries, as well as in research and development. Not only can the efficiency of crystallization/production processes and product quality be increased but also new equipment can be qualitatively characterized. A large variety of analytical methods for PSDs is available, most of which have underlying assumptions and corresponding errors affecting the measurement of the volume of individual particles. In this work we present a method for the determination of particle volumes in a bulk sample via micro-computed tomography and the application of artificial intelligence. The particle size of bulk samples of sucrose were measured with this method and compared to classical indirect measurement methods. Advantages of the workflow are presented. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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22 pages, 9199 KiB

Open AccessArticle

Features of the Defect Structure and Luminescence of Nominally Pure Lithium Niobate Crystals Produced Using Different Technologies

by Maxim Smirnov, Diana Manukovskaya, Nikolay Sidorov and Mikhail Palatnikov

Materials 2023, 16(1), 255; https://doi.org/10.3390/ma16010255 - 27 Dec 2022

Cited by 4 | Viewed by 1103

Abstract

We have established that luminescence in lithium niobate crystals both congruent and near-stoichiometric (R ≈ 1) is due to point defects in the cationic sublattice and intraconfigurational transitions in the oxygen-octahedral NbO₆ clusters. We have also determined that the main contribution to [...] Read more.

We have established that luminescence in lithium niobate crystals both congruent and near-stoichiometric (R ≈ 1) is due to point defects in the cationic sublattice and intraconfigurational transitions in the oxygen-octahedral NbO₆ clusters. We have also determined that the main contribution to the luminescence in the visible and near IR regions is made by luminescence centers with the participation of Nb_Li defects: the Nb_Li-Nb_Nb bipolaron pair and the Nb_Li-O defect in a congruent crystal. The minimum intensity of bipolaron luminescence has been observed in stoichiometric crystals obtained using different technologies. Weak luminescence of the Nb_Li-Nb_Nb bipolaron pair indicates a small number of Nb_Li defects in the crystal structure. The number of Nb_Li defects in the crystal structure indicates a deviation of the crystal composition from stoichiometry. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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14 pages, 3477 KiB

Open AccessArticle

Analysis of SAW Temperature Properties in KTiOPO₄ Single Crystal

by Rinat Taziev and Victor Atuchin

Materials 2023, 16(1), 69; https://doi.org/10.3390/ma16010069 - 21 Dec 2022

Cited by 3 | Viewed by 1043

Abstract

The surface acoustic wave (SAW) properties of potassium titanyl phosphate (KTiOPO₄, KTP) single crystal were evaluated by numerical methods. The phase velocity, electromechanical coupling coefficient, power flow deflection angle, and temperature coefficient of delay (TCD) were determined for different crystal cuts [...] Read more.

The surface acoustic wave (SAW) properties of potassium titanyl phosphate (KTiOPO₄, KTP) single crystal were evaluated by numerical methods. The phase velocity, electromechanical coupling coefficient, power flow deflection angle, and temperature coefficient of delay (TCD) were determined for different crystal cuts of KTP. It was shown that SAW has the electromechanical coupling coefficient of 0.59% and the TCD of 62 ppm/°C on the Z-cut and wave propagation direction along the crystal X + 70°-axis. For the Z-cut and wave propagation direction along the X-axis, the pseudo-surface wave (PSAW) is characterized by the coupling coefficient of 0.46% and the TCD value of 57 ppm/°C. The Bleustein–Gulyaev (BG) wave has the TCD value of 35 ppm/°C and 41 ppm/°C on the Y- and X-cuts of KTP, respectively. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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17 pages, 4906 KiB

Open AccessArticle

Silver Itaconate as Single-Source Precursor of Nanocomposites for the Analysis of Chloride Ions

by Tatiana S. Kolesnikova, Anastasiya O. Zarubina, Marina O. Gorbunova, Vladimir A. Zhinzhilo, Gulzhian I. Dzhardimalieva and Igor E. Uflyand

Materials 2022, 15(23), 8376; https://doi.org/10.3390/ma15238376 - 24 Nov 2022

Cited by 1 | Viewed by 1535

Abstract

At present, conjugated thermolysis of metal-containing monomers is widely used as single-source precursors to obtain new metal- and metal oxide-containing nanocomposites. In this study, a detailed analysis of the main stages of conjugated thermolysis of silver itaconate was carried out. The obtained nanocomposites [...] Read more.

At present, conjugated thermolysis of metal-containing monomers is widely used as single-source precursors to obtain new metal- and metal oxide-containing nanocomposites. In this study, a detailed analysis of the main stages of conjugated thermolysis of silver itaconate was carried out. The obtained nanocomposites containing silver nanoparticles are evenly distributed in a stabilizing carbon matrix. The structural characteristics and properties of the resulting nanomaterials were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). We have developed a method of test analysis of chlorides using paper modified with the obtained silver-containing nanocomposites. The analysis technique is based on the in situ conversion of chlorides to molecular chlorine, its dynamic release, and colorimetric detection using NP-modified paper test strips. A simple installation device is described that allows this combination to be realized. The proposed approach seems promising for nanoparticle-based determinations of other analytes that can be converted into volatile derivatives. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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8 pages, 3581 KiB

Open AccessArticle

X-ray Diffuse Scattering from Ca₃NbGa₃Si₂O₁₄ Single Crystal under External Electric Field Application

by Dmitrii Irzhak and Dmitry Roshchupkin

Materials 2022, 15(21), 7692; https://doi.org/10.3390/ma15217692 - 01 Nov 2022

Viewed by 1107

Abstract

X-ray diffuse scattering from the Ca₃NbGa₃Si₂O₁₄ (CNGS) crystal was measured with a triple axis X-ray diffractometer under the conditions of an external electric field. It is found that the nature of the intensity distribution of the [...] Read more.

X-ray diffuse scattering from the Ca₃NbGa₃Si₂O₁₄ (CNGS) crystal was measured with a triple axis X-ray diffractometer under the conditions of an external electric field. It is found that the nature of the intensity distribution of the asymmetrical part of diffuse scattering depends on the value of the applied electric field. This phenomenon is apparently associated with different piezoelectric characteristics of defect regions and the rest of the single crystal. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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11 pages, 2519 KiB

Open AccessArticle

Effect of Fe-Doping on Thermal Expansion and Stability of Bismuth Magnesium Tantalate Pyrochlorere

by Nadezhda A. Zhuk, Maria G. Krzhizhanovskaya, Sergey V. Nekipelov, Viktor N. Sivkov and Danil V. Sivkov

Materials 2022, 15(21), 7668; https://doi.org/10.3390/ma15217668 - 31 Oct 2022

Cited by 1 | Viewed by 1023

Abstract

A continuous series of solid solutions (Bi_1.5Mg_0.75−xFe_xTa_1.5O_7±Δ (x = 0–0.75)) with the pyrochlore structure were synthesized with the solid-phase method. It was shown that iron, like magnesium, is concentrated in the structure in the [...] Read more.

A continuous series of solid solutions (Bi_1.5Mg_0.75−xFe_xTa_1.5O_7±Δ (x = 0–0.75)) with the pyrochlore structure were synthesized with the solid-phase method. It was shown that iron, like magnesium, is concentrated in the structure in the octahedral position of tantalum. Doping with iron atoms led to an increase in the upper limit of the thermal stability interval of magnesium-containing pyrochlore from 1050 °C (x = 0) up to a temperature of 1140 °C (x = 1). The unit cell constant a and thermal expansion coefficient (TEC) increase uniformly slightly from 10.5018 Å up to 10.5761 Å and from 3.6 up to 9.3 × 10⁻⁶ °C⁻¹ in the temperature range 30–1100 °C. The effect of iron(III) ions on the thermal stability and thermal expansion of solid solutions was revealed. It has been established that the thermal stability of iron-containing solid solutions correlates with the unit cell parameter, and the lower the parameter, the more stable the compound. The TEC value, on the contrary, is inversely proportional to the cell constant. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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10 pages, 3742 KiB

Open AccessEditor’s ChoiceArticle

Ultra-Short Polarization Rotator Based on Flat-Shaped Photonic Crystal Fiber Filled with Liquid Crystal

by Rui Liu, Tiesheng Wu, Yiping Wang, Zhihui Liu, Weiping Cao, Dan Yang, Zuning Yang, Yan Liu and Xu Zhong

Materials 2022, 15(21), 7526; https://doi.org/10.3390/ma15217526 - 27 Oct 2022

Cited by 1 | Viewed by 1070

Abstract

In this study we demonstrate a high-performance polarization rotator (PR) based on flat-shaped photonic crystal fiber. The flat surfaces of the fiber are plated on gold films as electrodes, and the core of the structure is filled with liquid crystal. The polarization rotation [...] Read more.

In this study we demonstrate a high-performance polarization rotator (PR) based on flat-shaped photonic crystal fiber. The flat surfaces of the fiber are plated on gold films as electrodes, and the core of the structure is filled with liquid crystal. The polarization rotation characteristics of the flat-shaped fiber can be effectively adjusted by applying external voltage. The optical properties are analyzed using the finite element method (FEM). The results show that the magnitude of the modulation voltage is closely related to the thickness of the flat fiber. When the fiber thickness is 20 μm, only 100 V is required to achieve the highest PR performance. In the wavelength of the 1.55 μm band (~200 nm bandwidth), the conversion length of the PR is only 3.99 μm, the conversion efficiency is close to 100%, and the minimum crosstalk value is −26.2 dB. The presented PR, with its excellent performance, might enable promising applications in the communication system and the photonic integrated circuits. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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9 pages, 3575 KiB

Open AccessArticle

Eco-Friendly Approach for Graphene Oxide Synthesis by Modified Hummers Method

by Néstor Méndez-Lozano, Francisco Pérez-Reynoso and Carlos González-Gutiérrez

Materials 2022, 15(20), 7228; https://doi.org/10.3390/ma15207228 - 17 Oct 2022

Cited by 11 | Viewed by 2686

Abstract

The aim of this study is to produce graphene oxide using a modified Hummers method without using sodium nitrate. This modification eliminates the production of toxic gases. Two drying temperatures, 60 °C and 90 °C, were used. Material was characterized by X-Ray Diffraction, [...] Read more.

The aim of this study is to produce graphene oxide using a modified Hummers method without using sodium nitrate. This modification eliminates the production of toxic gases. Two drying temperatures, 60 °C and 90 °C, were used. Material was characterized by X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and Scanning Electron Microscopy. FTIR study shows various functional groups such as hydroxyl, carboxyl and carbonyl. The XRD results show that the space between the layers of GO60 is slightly larger than that for GO90. SEM images show a homogeneous network of graphene oxide layers of ≈6 to ≈9 nm. The procedure described has an environmentally friendly approach. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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19 pages, 11074 KiB

Open AccessEditor’s ChoiceArticle

Electronic Band Structure and Surface States in Dirac Semimetal LaAgSb₂

by Marcin Rosmus, Natalia Olszowska, Zbigniew Bukowski, Paweł Starowicz, Przemysław Piekarz and Andrzej Ptok

Materials 2022, 15(20), 7168; https://doi.org/10.3390/ma15207168 - 14 Oct 2022

Cited by 5 | Viewed by 1959

Abstract

LaAgSb

_{2}

is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the

Γ

–M direction. This paper is devoted to a [...] Read more.

LaAgSb

_{2}

is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the

Γ

–M direction. This paper is devoted to a complex analysis of the electronic band structure of LaAgSb

_{2}

by means of ARPES and theoretical studies within the ab initio method as well as tight binding model formulation. To investigate the possible surface states, we performed the direct DFT slab calculation and the surface Green function calculation for the (001) surface. The appearance of the surface states, which depends strongly on the surface, points to the conclusion that LaSb termination is realized in the cleaved crystals. Moreover, the surface states predicted by our calculations at the

Γ

and X points are found by ARPES. Nodal lines, which exist along the X–R and M–A paths due to crystal symmetry, are also observed experimentally. The calculations reveal other nodal lines, which originate from the vanishing of spin–orbit splitting and are located at the X–M–A–R plane at the Brillouin zone boundary. In addition, we analyze the band structure along the

Γ

–M path to verify whether Dirac surface states can be expected. Their appearance in this region is not confirmed. Full article

(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)

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