Crystal Research and Technology最新文献

Nucleation control and separation of ethyl maltol polymorphs Form-II and Form-III from mixed water (W) and ethanol (E) solutions with nine different mixing ratios, ranging from 90W:10E to 10W:90E, is reported for the first time using conventional slow evaporation crystallization method. Solutions with compositions of 90W:10E to 60W:40E induced Form-II, while the remaining five compositions resulted in the nucleation of Form-III. Solubility, refractive index, and pH are determined for these solutions. Form-II nucleated with prismatic-like morphology whereas Form-III exhibited platy-like morphology, as observed through in situ optical microscopy. Structural confirmation, thermal behavior, and possible polymorphic phase transformation are analyzed using powder X-ray diffraction and differential scanning calorimetry.

The authors of a recent paper (Cryst. Res. Technol. 2022, 57, 2100130) report to have grown crystals of triglycine acetate (TGAc) by slow evaporation of an aqueous solution containing glycine and acetic acid in 3:1 molar ratio. The infrared spectrum and unit cell data of the so-called TGAc crystal confirm that it is, in fact, α-glycine. The non-formation of any TGAc is due to no chemical reaction occurring between glycine and acetic acid. Another publication (Cryst. Res. Technol. 2022, 57, 2100262) describes the growth and characterization of a so-called triglycine oxalate (TGO) crystal. The unit cell data and infrared spectrum of the TGO crystal reveal that the crystal grown is, in fact, the well-known glycinium hydrogen oxalate. A critical analysis of the publications reporting on the growth of triglycine phosphate (TGP) and triglycine formate (TGF) crystals reveals that these are not what the authors claim them to be. Despite their names, the TGAc or TGP or TGO or TGF crystals are not analogs of the triglycine sulfate (TGS) crystal but serve as examples to highlight the importance of single-crystal structure refinement to avoid improper characterization.

The unique morphology and structure significantly enhance the performance of photoelectric detection. Herein, titanyl phthalocyanine (TiOPc) coarse crystal and microspheres are obtained by a simple physical vapor deposition (PVD) method designed to produce TiOPc structures that undergo significant changes in the crystal structure. The photoelectric experimental results show that the photocurrent of TiOPc coarse crystal and microspheres increases with the increase of voltage and exhibits better stability compared to the raw materials. Under a bias voltage of 10 V, the photoresponsivity of microspheres reaches the maximum, which is 77 times that of raw materials. Under different monochromatic lights, the raw materials are most sensitive to red light (850 nm), with a photocurrent of 1.3556 × 10⁻⁶ mA, but the coarse crystal/microspheres are most sensitive to blue light (455 nm) with photocurrents of 1.281 × 10⁻⁵ mA/2.609 × 10⁻⁵ mA, respectively. It is worth mentioning that although the photocurrent and responsivity of coarse crystal are slightly lower than those of microspheres, the response speed is faster, with a rise/fall time is 271 and 194 ms, respectively. The good photoelectric properties indicate the potential research value of TiOPc coarse crystal and microspheres in the field of photoelectric detection.

β-Ga₂O₃ is a promising wide band gap material for power device and solar-blind photodector applications. With continuous contribution to the crystal growth of β-Ga₂O₃, it is important to conclude the progress of crystal growth techniques and the remaining problems of the materials propel the next generation of the power device industry. The size of single crystals becomes larger, the quality of epitaxial films is gradually improved, and the performance of devices has become better. β-Ga₂O₃ is an oxide semiconductor with a large bandgap width of 4.7–4.9 eV and a high breakdown electric field of ≈8 MV cm⁻¹. In this review, the structure, thermal properties, optical properties, and electronic properties of β-Ga₂O₃ are introduced first. Then, the growth methods of bulk β-Ga₂O₃ single crystals are introduced, including the Verneuil method, Czochralski (CZ) method, optical-floating zone (OFZ) method, edge-defined film-fed growth (EFG) method, vertical Bridgman (VB) method, casting method, and the oxide crystal growth from cold crucible (OCCC) method. Crystal growth mechanisms and their respective advantages and disadvantages are discussed. The effects of doping elements on the crystal growth have been highlighted in each method. Finally, the prospect of the growth of large β-Ga₂O₃ single crystals is discussed.

The flexibility and adaptability of low-dimensional halide perovskites make them ideal candidates for a wide range of cutting-edge technologies. In addition to their primary applications in photovoltaics, they have recently attracted attention for their potential use in switchable technologies such as smart windows, encrypted messages, and sensors. The interest stems from their switchable properties, which enable them to change their physical properties, in particular photoluminescence and crystal color, in response to external stimuli such as heat, light, pressure, and humidity. This review examines their switchable properties and explores their practical applications in a number of emerging chromic technologies. This paper also provides an in-depth analysis of the reversibility, switchable optical and electrical properties of low-dimensional halide perovskites, and the switching mechanisms involved in the transformations they undergo. In addition, the paper is classified according to different switching mechanisms. To assist the research community in developing new designs for new switchable low-dimensional perovskites, some basic criteria for effective switching materials are outlined here. Finally, the current challenges facing these emerging materials are discussed, and an outlook on future developments and potential breakthroughs in this promising area of research is provided.

Lead sulfide (PbS) nanoparticles are used in gas sensing for which it is necessary to achieve smaller PbS crystallite sizes. However, the operating conditions to produce the minimum size of PbS nanoparticles do not seem to be reported so far. In this light, this article discusses the synthesis of PbS nanoparticles using the Response Surface Methodology (RSM) choosing the face-centered central composite design (FC-CCD) for which a total of 20 (twenty) experiments are required to be conducted. X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are used for synthesized PbS samples’ characterization. The smallest PbS crystallite size, as reveals from XRD analysis, is 14.11 nm. All samples' FTIR spectra verified the distinctive peaks of PbS phase. PbS nanoparticle formation is visible in the SEM images. A reduced quadratic polynomial model as obtained from the optimization is found to be accurate. An experiment carried out under optimum conditions confirms the model’s validity in obtaining PbS nanoparticles' crystallite size of 15.62 nm (deviation = + 3.24 %). It can be concluded that the methodology demonstrated in this article could can be applied to synthesize PbS nanoparticles with a minimum crystallite size for use as gas sensors.

The active form of vitamin D₃, cholecalciferol, is one of the essential constituents that allows most cells to develop and differentiate, and also critical for parathyroid regulation and immune system improvement. Reducing the size of cholecalciferol can offer several benefits, such as improved surface area, enhanced biological activity, and better penetrating power. In this context, antisolvent crystallization is utilized to decrease the particle size of cholecalciferol. The solvent and antisolvent selections are made using Hansen solubility parameters (HSP). The effect of various factors like ratio of antisolvent to solvent (1:1–20:1, v/v), rate of addition (5–40, mL h⁻¹), stirring speed (200–500 rpm), concentration of cholecalciferol (2.5–15, mg mL⁻¹), and temperature (15–30 °C) is assessed using parametric study. The individual and interaction effects are studied using the central composite design (CCD) followed by model formulation and optimization. The lowest particle size (111.6 nm) is obtained at 2.5 mg mL⁻¹ concentration of cholecalciferol, 25 mL h⁻¹ rate of addition, 10:1 (v/v) antisolvent to solvent ratio, 20 °C temperature, and stirring speed of 300 rpm.

The rapid advancement of terahertz (THz) technology has driven an increasing demand for efficient THz sources and detectors, particularly in applications such as spectroscopy, imaging, and wireless communications. Organic (NLO) crystals, renowned for their high nonlinear coefficients, tunability, and flexible molecular design, have emerged as highly promising materials for THz generation. This article highlights the latest progress in the design, synthesis, and investigation of novel organic NLO crystals demonstrating exceptional THz activity, with a focus on recent breakthroughs in ionic and molecular crystals. The discussion delves into the pivotal roles of crystal packing, molecular engineering, and functional group modification in optimizing nonlinear optical properties. Furthermore, the article explores strategies for performance enhancement through molecular engineering and functional group modification, offering insights into the mechanisms driving these advancements. Based on cutting-edge research on advanced NLO crystals, this study examines future research directions and potential applications, emphasizing the critical need for improved crystal growth techniques, refined theoretical modeling, and enhanced material stability. By providing a comprehensive review of the current state of organic THz optical crystals, this article aims to illuminate the challenges and opportunities within this rapidly evolving field, paving the way for future innovations.