Stable Crystals Research Articles

Accelerated Crystallization and Preferred Formation of a Thermally Stable Crystal Phase in Enantiomeric Blends of Long-Spaced Chiral Polyesters

Accelerated Crystallization and Preferred Formation of a Thermally Stable Crystal Phase in Enantiomeric Blends of Long-Spaced Chiral Polyesters

Response Matching for Generating Materials and Molecules.

Diffusion models have recently emerged as powerful tools for the generation of new molecular and material structures. The key insight is that the noise in these models is related to the response of the atoms to displacement, and the denoising step is thus analogous to the geometry relaxation of atomistic systems starting from a random structure. Building on this, we present a generative method called Response Matching (RM), which leverages the fact that each stable material or molecule exists at the minimum of its potential energy surface. Any perturbation induces a response in energy and stress, driving the structure back to equilibrium. Matching this response is closely related to score matching in diffusion models. Another important aspect of state-of-the-art diffusion models is the incorporation of physical symmetries such as translation, rotation, and periodicity. RM employs a machine learning interatomic potential and random structure search as the denoising model, inherently respecting these symmetries and exploiting the locality of atomic interactions. RM handles both molecules and bulk materials under the same framework. Its efficiency and generalization are demonstrated on three systems: a small organic molecular data set, stable crystals from the Materials Project, and one-shot learning on a single diamond configuration.

Rigidity‐Driven Structural Isomers in the NaCl–Ga2S3 System: Implications for Energy Storage

Alternative energy sources require the search for innovative materials with promising functionalities. Systems with unusual chemical properties represent an insufficiently explored domain, concealing unexpected features. Using diffraction and Raman spectroscopy over a wide temperature range, supported by first‐principles simulations, a rare phenomenon is unveiled: phase‐dependent chemical interactions between binary components in the NaCl–Ga2S3 system. In this unique occurrence, previously intact binary crystalline species transform upon melting into mixed liquid structural isomers, forming bonds with new partners. The chemical combinatorics appears to be fully reversible for stable crystals and liquids. Despite this, rapidly frozen glasses out of thermodynamic equilibrium remain in a metastable isomeric state, offering remarkable properties, particularly a high room‐temperature Na+ conductivity, comparable to the best sodium halide superionic conductors and therefore encouraging for sodium solid‐state batteries and energy applications. A rigidity paradigm is responsible for the observed phenomenon, as the extremely constrained Ga2S3 crystal lattice does not survive viscous flow, breaking up at a short‐range level. The removal of rigidity constraints and dense packing leads to a significant increase in empty space, which is the origin of high sodium diffusivity. Broadly, the rigidity‐driven structural isomerism opens up an inspiring path to the discovery of atypical materials.

Mixing screw design and high density polyethylene toughening modification for recycled polypropylene based on screw 3D printing

AbstractThe recycling of waste plastics primarily involves physical modification and the addition of modifiers, often utilizing equipment such as twin‐screw extruders for miscible modification. Considering the widespread use of single‐screw 3D printing, improving the mixing efficiency of the single‐screw is crucial to achieve a “one‐stop” recycling modification that is suitable for 3D printing. This paper introduces a 3D printer equipped with a mixing screw (MS) and compares it with a conventional screw (CS). We conduct numerical simulations to investigate the pressure build‐up capacity, velocity streamline distribution, and the mixing effect of the MS. The mechanical properties, thermal characteristics, and molecular orientation of the recycled Polypropylene (rPP) and high density polyethylene (HDPE) mixture are investigated through experiments. The results show that the MS provides more effective elongational flows compared to the CS by breaking down the reinforcing materials into smaller particles. Additionally, toughening and modification experiments are performed on rPP and HDPE. The composites treated with the MS showed improved elongation at break (increased by ~111%), a stable melt crystallization temperature, and an enhanced mixing effect. This study on single‐screw 3D printers lays the groundwork for streamlining the plastic recycling process and increasing the reuse rate of recycled plastics.

Solvent‐free crystallization for fractionation of virgin coconut oil: Effect of process conditions on kinetics and crystal properties

AbstractThis research was aimed to conduct solvent‐free crystallization and fractionation of virgin coconut oil (VCO). This study investigated the effect of surface contact area‐to‐volume ratio and mixing conditions on crystal characteristics. Commercially available VCO samples, extracted by different methods, were analyzed for fatty acid and triacylglycerol composition using GC–MS and UPLC–ELSD. VCO extracted through enzyme and chilling–thawing cycles exhibited higher medium chain fatty acids and medium chain triacylglycerols, which was selected for crystallization studies. Isothermal crystallization of VCO at 21°C assessed the effect of scale of crystallizer tube on cooling rate using Newton's law of cooling equation. The smaller tube (20 mm diameter) with a higher surface contact area‐to‐volume ratio produced 4.1‐fold faster cooling and a higher crystallization yield (44%) compared to the 80 mm diameter tube when no agitation was applied. Whereas mixing with a magnetic stirrer produced a large number of nuclei, generating intense crystallization heat, and rendering the crystals inseparable from liquid fraction. The process of VCO crystallization was also studied for kinetics and crystal growth mechanism using the Avrami model employing angled rotation of sample tube during non‐isothermal crystallization. Angled rotary mixing produced stable crystals and significantly increased the crystallization rate (t1/2 = 26.86 min) with polyhedral or spherulitic crystal growth (n = 3.25) compared to non‐mixing condition (t1/2 = 161.87 min) with restricted linear growth (n = 1.64). DSC analysis of VCO and its fractions obtained after crystallization using the 20 mm tube with angled rotary mixing indicated shifts in their thermogram peaks, suggesting differences in triacylglycerol compositions.Practical applicationsVirgin coconut oil (VCO) is well recognized for its health‐beneficial properties, yet its application is limited due to its complex triglyceride composition. The solvent‐free crystallization method facilitates VCO fractionation into phases with different melting points without hazardous solvents. The efficacy of this process is highly dependent on temperature, cooling rate, and agitation, which affects crystal morphology and growth kinetics. This study addresses these challenges in the scarcely investigated area of VCO crystallization. The resulting fractions can be customized for specific applications based on their altered functional properties in producing baking and confectionery coatings, salad dressings, and so on. The olein fraction obtained in this study can be utilized in nutraceutical formulations targeting digestive and cognitive health, as it is reported to be rich in medium chain triglycerides. This research optimizes process conditions, suggesting an efficient method for dry‐fractionating VCO, which is significantly associated with the food and pharmaceutical industries.

Wide‐Bandgap RBa3(B3O6)3 (R = Nd, Sm, Tb, Dy, and Er) Single Crystals for Ultraviolet Nonlinear Optics

AbstractDiscovery of new materials with enhanced optical properties in the visible and UV‐C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates, RBa3(B3O6)3 (R = Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X‐ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetric P space group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid‐IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type‐I and Type‐II SHG phase matchability, with the highest effective phase‐matched SHG coefficient of 1.2 pm V−1 at 800‐nm fundamental wavelength (for DyBa3(B3O6)3), comparable to β‐BaB2O4 (phase‐matched d22 ≈ 1.9 pm V−1). Laser‐induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm−2, which is four to five times higher than that of β‐BaB2O4, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba‐site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications.

Crystal growth and characterization of Fe1+δSe1-xTex (0.5 ≤ x ≤ 1) from LiCl/KCl flux

An eutectic LiCl/KCl flux method in a horizontal configuration has been used to grow a series of homogeneous Fe1+δSe1-xTex single crystals of high quality with 0.5 ≤ x ≤ 1. Compared with previously used melt-growth method, the stable crystallization process in LiCl/KCl flux below their peritectic temperatures results in better homogeneity and crystalline perfection identified by energy dispersive spectrometer and x-ray diffraction. The interstitial Fe value δ remains small within 0.5 ≤ x ≤ 0.85 where the superconducting temperature TC is not sensitive to the Te content with sharp superconducting transition widths ΔTC < 1 K and a maximum of TC = 14.3 K at x = 0.61. The value δ starts to increase quickly accompanied by a deviation of linear behavior of crystal lattice parameters as well as the broadening of ΔTC = 2.1 K at x = 0.91, then suddenly rises up to δ > 0.1 followed by the disappearance of superconductivity and emergence of antiferromagnetic order at x ≥ 0.96. We also observed a metallic to semiconducting transition in the normal state resistivity of Fe1+δSe1-xTex with increasing Te content which is related to a localized electronic state induced by the interstitial Fe. The interstitial Fe value δ might be a key physical parameter to understand various properties of Fe1+δSe1-xTex system.

Highly selective and efficient Pb2+ capture using PO4-loaded 3D-NiFe layer double hydroxides derived from MIL-88A

Lead (Pb) contamination in water requires improved decontamination technologies. The addition of phosphate to precipitate Pb2+ is a widely used method for remediating Pb in soil and water, though it has certain limitations. This study focuses on novel 3D mesoporous layered double hydroxide (LDH) sorbents functionalized with phosphate anions for Pb2+ removal from contaminated waters. Our innovative strategy involves converting a sacrificial template metal-organic frameworks (MOFs) structure (MIL-88A(Fe)) into NixFe LDH, followed by an anion exchange reaction with phosphate anions. This process preserves the 3D microrod architecture of MIL-88A and prevents deleterious LDH particle aggregation. The synthesis results in stable microrod crystals, 1–2 μm long, composed of 3D assemblies of NixFe-PO4 LDH nanoplatelets with a specific surface area exceeding 110 m2/g. The novel LDH materials display fast adsorption kinetics (pseudo-second order model) and remarkably high Pb2+ removal performances (Langmuir isotherm model) with a capacity of 538 mg/g, surpassing other reported adsorbents. LDH-PO4 exhibits high selectivity for Pb2+ over competing ions like Ni2+ and Cd2+ (selectivity order is: Pb2+ > Ni2+ > Cd2+). Removal of Pb2+ from NixFeLDH/88A-PO4 involves various mechanisms, including surface complexation and surface precipitation of lead phosphate or lead hydroxide phases as revealed by structural characterization techniques.

Piezoelectric properties and microstructural changes of smart asphalt-based composites containing electroactive polymer and carbon black

The requirements for smart asphalt pavement with piezoelectric properties are becoming necessary as the demand for clean energy and intelligent transportation are increased. To develop asphalt-based composite with electroactive performance for pavement electricity generation and to recycle battery waste, carbon black was first added to polyvinylidene fluoride-hexafluoropropylene to prepare electroactive polymer modifier (EPM) with high content of electroactive crystalline phases. Then carbon black and EPM were added into asphalt to prepare asphalt-based composites containing electroactive polymer (ACEP). The Output voltage, environmental scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and basic performance tests were conducted to study the piezoelectric properties, microstructural changes, electroactivity generation mechanism and basic performance of ACEP. The result shows that 5 % EPM has good dispersion, and stable crystallization rate of about 26 % and considerable electroactive crystalline phase content in asphalt, but more holes and defects inside ACEP appears when EPM is excessive. Also, the addition of EPM can slightly improve low-temperature property and thermal stability of ACEP. This is because the F element in EPM can interact with the polar groups in the gum and asphaltene. The 5 % ACEP sample with a thickness of 5 mm can output a voltage of about 260 mV. The penetration, ductility and softening point of 5 % ACEP were 55.2 dmm, 285 mm and 62.3°C, respectively. It is found that ACEP has a good combination of piezoelectric and basic pavement properties and can be used to build smart asphalt pavement with piezoelectric properties. This also provides a way to recycle battery waste.

Dielectric and magnetic properties of thermally stable crystals of cobalt dimandelate

Dielectric and magnetic properties of thermally stable crystals of cobalt dimandelate

Electrically‐Triggered Oblique Helicoidal Cholesterics with a Single‐Layer Architecture for Next‐Generation Full‐Color Reflective Displays

AbstractElectrically‐induced oblique helicoidal cholesterics (ChOH) are attractive for use in reflective displays due to tunable photonic band gap (PBG) in a broad spectral range and natural eye‐friendly feature. However, the lack of a stable liquid crystal (LC) material system with a wide temperature range and unknown driver architecture hinder the implementation of the ChOH‐based reflective displays. Here, a prototype for a full‐color reflective display device based on electrically‐tunable ChOH‐LC is demonstrated. In the comparison of ChOH‐S1, S2 and S3 samples, the electric‐field‐induced ChOH in the ChOH‐S3 exhibits intense Bragg reflection and a tunable PBG in the extended temperature range from 19.5 °C to 30 °C. Particularly, the resulting device exhibits a lower driving voltage and a relatively larger color gamut for the full‐color reflective displays. On this basis, the display patterns with variable colors are demonstrated via the direct addressing mode. Furthermore, a proof‐of‐concept of the full‐color reflective display is demonstrated with red‐green‐blue pixeled images serving as the active panels. Ultimately, by regulating the electric field strength dependent on the ambient temperature, a stable and vivid effect of the ChOH device on the actual environment is shown. This work provides valuable insight for the development of ChOH‐based reflective displays.

Chelating Dual Interface for Efficient and Stable Crystal Growth and Iodine Defect Management in Sn-Pb Perovskite Solar Cells.

Suppressing Sn2+ oxidation and rationally controlling the crystallization process of tin-lead perovskite (Sn-Pb PVK) films by suitable bonding methods have emerged as key approaches to achieving efficient and stable Sn-Pb perovskite solar cells (PSCs). Herein, the chelating coordination is performed at the top and bottom interfaces of Sn-Pb PVK films. The chelation strength is stronger toward Sn2+ than Pb2+ by introducing oligomeric proanthocyanidins (OPC) at the bottom interface. This difference in chelation strength resulted in a spontaneous gradient distribution of Sn/Pb within the perovskite layer during crystallization, particularly enhancing the enrichment of Sn2+ at the bottom interface and facilitating the extraction and separation of photogenerated charge carriers in PSCs. Simultaneously, this top-down distribution of gradually increasing Sn content slowed down the crystallization rate of Sn-Pb PVK films, forming higher-quality films. On the top interface of the PVK, trifluoroacetamidine (TFA) was used to inhibit the generation of iodine vacancies (VI) through chelating with surface-uncoordinated Pb2+/Sn2+, further passivating defects while suppressing the oxidation of Sn2+. Ultimately, the PSCs with simultaneous chelation at both top and bottom interfaces achieved a power conversion efficiency (PCE) of 23.31% and an open-circuit voltage (VOC) exceeding 0.90 V. The stability of unencapsulated target devices in different environments also improved.

Sulfone‐functionalized stable molecular single crystals for photocatalytic hydrogen evolution

AbstractHighly crystalline organic semiconductors are ideal materials for photocatalytic hydrogen evolution in water splitting. However, the instability and complex synthesis processes of most reported organic molecule‐based photocatalysts restrict their applications. In this study, we introduce benzo [1,2‐b:4,5‐bʹ] bis [1] benzothiophene‐3,9‐dicarboxylic acid, 5,5,11,11‐tetraoxide (FSOCA), a highly crystalline, stable molecular crystal that is easy to synthesize and serves as an efficient photocatalyst for the hydrogen evolution reaction. FSOCA exhibits high efficiency in sacrificial hydrogen evolution reaction (760 µmol h−1, 76 mmol g−1 h−1 at 330 mW cm−2; 570 µmol h−1, 57 mmol g−1 h−1 at 250 mW cm−2), and FSOCA remains stable during photocatalysis for up to 400 h. Experiments and theoretical studies confirmed the presence of hydrogen bonds between the sulfone group and the sacrificial agent (ascorbic acid). This interaction significantly improved the oxidation reaction kinetics and boosted the photocatalytic performance. This study presents a scalable and convenient approach to synthesize highly crystalline, active, and stable organic photocatalysts with potential applications in large‐scale photocatalysis.

Flexible, Photonic Films of Surfactant‐Functionalized Cellulose Nanocrystals for Pressure and Humidity Sensing

Most paints contain pigments that absorb light and fade over time. A robust alternative can be found in nature, where structural coloration arises from the interference of light with submicron features. Plant‐derived, cellulose nanocrystals (CNCs) mimic these features by self‐assembling into a cholesteric liquid crystal that exhibits structural coloration when dried. While much research has been done on CNCs in aqueous solutions, less is known about transferring CNCs to apolar solvents that are widely employed in paints. This study uses a common surfactant in agricultural and industrial products to suspend CNCs in toluene . Surprisingly, a stable liquid crystal phase is formed within hours, even with concentrations of up to 50 wt%. Evaporating the apolar CNC suspensions results in photonic films with peak wavelengths ranging from 660 to 920 nm. The resulting flexible films have variable mechanical properties with surfactant content, allowing for an optical response with applied force. The films also act as humidity sensors, with increasing relative humidity swelling the films, yielding a redshift in the reflected wavelength. With the addition of a single surfactant, CNCs can be made compatible with existing production methods of industrial coatings, while improving the strength and responsiveness of structurally colored films to external stimuli.

Yield enhancement and phase behaviors of cyclic peptide drug crystallization in the presence of polyethylene glycol additive

Crystallization of peptide drugs typically requires a lengthy period to attain reasonable yields due to slow crystallization kinetics of macromolecules. Herein we investigated the use of polyethylene glycol (8 kDa) (PEG 8k) as an additive to enhance the yield of salting-out crystallization of cyclic peptide drug vancomycin (Van). Our preliminary study showed the addition of PEG 8k increased the 24-h yield from 46 wt% to 70 wt% attributed to the polymer’s volume-exclusion effects. PEG 8k addition, however, resulted in modified Van crystal habits, thereby phase behavior study was performed at different pH, salt, polymer, and Van concentrations. The phase behavior study showed PEG 8k and salt concentrations must be meticulously determined to produce stable Van crystals because their excessive concentrations resulted in heavy precipitates. Different crystal habits (e.g., acicular, blade-like) were produced with PEG 8k additive depending on the pH, distinct from octahedral crystals produced without additive. Bulk crystallization with PEG 8k additive resulted in platy Van crystals with higher crystallinity, lower thermal stability and purity, but with similar dissolution rates compared to octahedral crystals prepared without PEG 8k. PEG 8k addition had catalytic effects on the salting-out yield whereby lower salt concentration was needed. In short, PEG 8k addition enhanced the yield without compromising Van crystals’ qualities.

Mitigation of arsenic and zinc toxicity in municipal sewage sludge through co-pyrolysis with zero-valent iron: A promising approach for toxicity reduction of sewage sludge

Abstract The co-pyrolysis (at 300°C and 600°C) of municipal sewage sludge (SS) with zero-valent iron (Fe0: 1.5% and 3%) was investigated to reduce the toxicity of arsenic (As) and zinc (Zn) in SS. The BCR sequential extraction method, desorption kinetic analysis, and material characterization techniques (Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, X-ray diffraction) were used to evaluate the effects of the treatments on Zn and As behavior. The results showed that co-pyrolysis significantly reduced the acid-soluble fraction (18–43% for Zn; 83–95% for As) and mobility factor (45–85% for Zn; 86–96% for As) of Zn and As compared to untreated SS. Desorption experiments indicated a significant reduction in Zn and As release in treated samples, particularly in the co-pyrolysis sample at 600°C and Fe0 3% (67% for Zn; 88% for As) in comparison with untreated SS. Co-pyrolysis of Fe0 and SS led to the formation of new functional groups (Si–O, aromatic), a more porous surface morphology, and highly stable chemical crystals (ferric arsenate, zinc arsenide), which played a crucial role in Zn and As stabilization. The findings of this study suggest that co-pyrolysis is a promising approach for mitigating As and Zn toxicity in SS. However, additional field testing with plant-based systems is necessary for confirmation.

Two-step modification of pullulanase and transglucosidase: A novel way to improve the gel strength and reduce the digestibility of rice starch

The multiscale structure, gel strength and digestibility of rice starch modified by the two-step modification of pullulanase (PUL) pretreatment and transglucosidase (TG) treatment for 6, 12, 18 and 24 h were investigated. The debranching hydrolysis of PUL produced some linear chains, which rearranged to form stable crystalline structures, reducing the digestible starch content, but weakening the gel strength. TG treatment connected some short chains to longer linear chains via α-1,6-glycosidic bonds, generating the structures of linear chain with fewer branches. The short branches promoted the interaction between starch molecules to form a more compact three-dimensional gel network structure, showing higher hardness and springiness. Moreover, these chains could form more stable crystals, reducing the digestible starch content, and the increase of branching degree inhibited digestive enzyme hydrolysis, reducing the digestion rate. The multiscale structure of starch tended to stabilize after TG treatment for 18 h, which could form a gel with stronger strength and lower digestibility than native starch gel. Therefore, the two-step modification of PUL and TG was an effective way to change the structure of rice starch to improve the gel strength and reduce the digestibility.

Green and stable synthesis of MCM-56 zeolite by using choline chloride as template

It is desirable to develop eco-friendly structure-directing agents as an alternative to the highly toxic templates during the synthesis process of many zeolites. In this work, a MWW type zeolite (denoted as CC-MCM-56) was stably synthesized with ITQ-1 seed assistance by using a green and nuisance-less choline chloride (CC) as organic structure-directing agents instead of the conventional toxic (HMI) template. The CC-MCM-56 zeolite exhibited similar physicochemical properties to the conventional MCM-56 (HMI), including acid properties, high specific surface area, especially high external specific surface area and mesoporous volume, which performed an excellent result in the liquid-phase alkylation reaction of benzene with long-chain olefins. Our findings reveal that the synergistic effect of ITQ-1 seed and CC molecule enable a longer and more stable crystallization period during the synthesis process of MCM-56 zeolite. The SAXS result coupled with other techniques indicate that ITQ-1 seed is firstly dissolved to form more structural units which could interact with CC molecules, making more CC molecules attached to the surface half cup of the MWW lamellae and promoting the stable synthesis of CC-MCM-56 zeolite with thinner-layer structure. Finally, the synthesized CC-MCM-56 zeolite showed high reactivity and the conversion of 1-hexane and 1-dodecene achieved 90.5% and 90.6% respectively.

Self-trapping of vortex crystals via competing nonlinearities.

We investigate the existence of self-trapped nonlinear waves with multiple phase singularities. Working with the cubic-quintic nonlinear Schrödinger equation, we focus on configurations with an antivortex surrounded by a triangular arrangement of vortices within a hosting soliton. We find stationary patterns that can be interpreted as stable self-trapped vortex crystals, constituting the first example of a configuration of this sort with space-independent potentials. Their stability is linked to their norm, transitioning from unstable to stable as their size increases, with an intermediate region where the structure is marginally unstable, undergoing a remarkable and puzzling self-reconstruction during its evolution.

Oiling-Out: Insights from Gibbsian Surface Thermodynamics by Stability Analysis.

The crystallization process is a significant stage in the pharmaceutical industry. During the process of crystallization with cooling, it is possible for a secondary liquid phase to appear before the formation of crystals. This phenomenon is called "oiling out" or liquid-liquid phase separation (LLPS). In this article, we explore the oiling-out phenomenon in a binary system of water and vanillin using stability analysis based on Gibbsian surface thermodynamics. To obtain the full picture of oiling out, we investigated three cases: droplet-solute-lean liquid equilibrium (DLE), crystal-solute-rich liquid equilibrium (CL'E), and crystal-solute-lean liquid equilibrium (CLE). The phase diagram of the system is plotted using the NRTL model for activity coefficients, along with considering the effect of the interfacial curvature on the phase diagram. From the phase boundaries and free-energy diagram of each case, we showed that the occurrence of the oiling-out phenomenon is justified based on the lower energy barrier of the droplet formation compared to that of the crystal formation. However, the energy level of a stable crystal is significantly lower and hence more stable than that of a stable droplet. Finally, we have determined different regions for droplet and crystal formation in the metastable phase diagram based on their supersaturation and provide insight for the oiling-out phenomenon.