Control Of Crystal Growth Research Articles

Structure–Activity Relationships of Hydroxyapatite-Binding Peptides

Elucidating the structure-activity relationships between biomolecules and hydroxyapatite (HAP) is essential to understand bone mineralization mechanisms, develop HAP-based implants, and design drug delivery vectors. Here, four peptides identified by phage display were selected as model HAP-binding peptides (HBPs) to examine the effects of primary amino acid sequence, phosphorylation of serine, presence of charged amino acid residues, and net charge of the peptide on (1) HAP-binding affinity, (2) secondary conformation, and (3) HAP nucleation and crystal growth. Binding affinities were determined by obtaining adsorption isotherms by mass depletion, and the conformations of the peptides in solution and bound states were observed by circular dichroism. Results showed that the magnitude of the net charge primarily controlled binding affinity, with little dependence on the other HBP features. The binding affinity and conformation results were in good agreement with our previous molecular dynamics simulation results, thus providing an excellent benchmark for the simulations. Transmission electron microscopy was used to explore the effect of these HBPs on calcium phosphate (Ca-PO4) nucleation and growth. Results indicated that HBPs may inhibit nucleation of Ca-PO4 nanoparticles and their phase transition to crystalline HAP, as well as control crystal growth rates in specific crystallographic directions, thus changing the classical needle-like morphology of inorganically grown HAP crystals to a biomimetic plate-like morphology.

α-CsPbI3 Nanocrystals by Ultraviolet Light-Driven Oriented Attachment.

Size and crystallinity of building units in the perovskite layer are of great significance to photovoltaic performance. Thus, to fabricate large-grain-size perovskite materials with the advantage of good crystallinity is quite necessary. The oriented attachment strategy has been proofed as an efficient method to control crystal growth. Herein, we reported on oriented attachment of α-CsPbI3 quantum dots (QDs) into a large-grain-size nanocrystal under moderate ultraviolet (UV) light. By virtue of atomic-resolution TEM and X-ray absorption fine structure (XAFS) spectroscopy, we observed the UV-directed structure-evolution and growth process. This is trigged by UV-light illumination (7 W, 365 nm), which drives the oriented assembly of QDs into a large nanoparticle along {110} facets. Moreover, we also visualized a damage process of the α-CsPbI3 QDs to photoinactive-δ-phase ones and finally into PbI2 under high-power UV-light (100 W, 365 nm) exposure. The findings provide a prototype for fabricating large-size perovskite nanostructures with promising properties.

Control of crystal growth of intermetallic compounds in Aluminum alloys and their application to novel high thermal conductivity heat sink products

Control of crystal growth of intermetallic compounds in Aluminum alloys and their application to novel high thermal conductivity heat sink products

Crystal growth control of rod-shaped ε-Fe2O3 nanocrystals.

Herein we report crystal growth control of rod-shaped ε-Fe2O3 nanocrystals by developing a synthesis based on the sol–gel technique using β-FeO(OH) as a seed in the presence of a barium cation. ε-Fe2O3 nanocrystals are obtained over a wide calcination temperature range between 800 °C and 1000 °C. A low calcination temperature (800 °C) provides an almost cubic rectangular-shaped ε-Fe2O3 nanocrystal with an aspect ratio of 1.4, whereas a high calcination temperature (1000 °C) provides an elongated rod-shaped ε-Fe2O3 nanocrystal with an aspect ratio of 3.3. Such systematic anisotropic growth of ε-Fe2O3 is achieved due to the wide calcination temperature in the presence of barium cations. The surface energy and the anisotropic adsorption of barium on the surface of ε-Fe2O3 can explain the anisotropic crystal growth of rod-shaped ε-Fe2O3 along the crystallographic a-axis. The present work may provide important knowledge about how to control the anisotropic crystal shape of nanomaterials.

Nucleation and crystal growth control for scalable solution-processed organic–inorganic hybrid perovskite solar cells

In this review, we provide an in-depth overview of perovskite film formation mechanism and highlight the important role of nucleation/crystal growth in perovskite photovoltaics by using scalable solution deposition techniques.

The diquaternary ammonium surfactant-directed synthesis of single-unit-cell nanowires of ZSM-5 zeolite.

Hierarchical ultrathin ZSM-5 zeolite samples with controllable crystal growth directions were realized by designing bifunctional soft templates with different hydrophobic alkyl chain groups. MFI-type crystal growth along the a-c plane and stacking along the b-axis could be controlled to form nanowires of ZSM-5, which exhibited better catalytic activity for phenol hydroxylation than nanosheets of ZSM-5.

Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al–Si alloy

In this paper, the principle of “plain materials” was attempted to advancing silicon (Si) purity, i.e., controlling solid-liquid interface and Si crystal growth pattern to enhance impurities removal from Si in directional solidification refining with Al–Si alloy. The relationship between Si crystal growth and impurity removal was established, and it was found that the removal ratio of metal impurities (less than 95% to more than 99%) gradually decreased with the order evolution of Si crystal from bulk Si, porous Si, acicular Si to Al–Si eutectic alloy. More than 99.5% of metallic impurities could be removed in the case of bulk silicon. However, the removal of boron (B) and phosphorus (P) showed the opposite trend. According to the principle of constitutional supercooling, the crystal Si growth and interface morphology were evaluated based on the conservation of mass of silicon atoms at the solidification interface, which was also used to explain the mechanism of impurities removal. Control of silicon crystal growth was achieved by changing the temperature gradient (lowering rate), Si alloy composition (Si content) and the heat transfer mode of solid-liquid interface that was expressed in terms of the effective heat transfer area ratio between wall and bottom of crucible (LA). A more stable and flat liquid-solid interface and 45% bulk Si was obtained at a lowering rate of 0.05 mm/min when the value of LA was 0.1, which can greatly enhance the removal of impurities.

Hematite microcube decorated TiO2 nanorods as heterojunction photocatalyst with in-situ carbon doping derived from polysaccharides bio-templates hydrothermal carbonization

The novel in-situ formation of a heterojunction photocatalyst consisting of C-doped TiO2 nanorods decorated on the surface of C-doped α-Fe2O3 microcubes was successfully achieved using a one-pot hydrothermal carbonization synthesis. In this work, the treated kapok fibers (t-KF) used as a polysaccharide bio-template provided a dual function for crystal growth control and in-situ carbon doping of the heterojunction photocatalyst. It was found that the α-Fe2O3 precursor concentration plays an essential role in the unique and well-developed C-doped TiO2/α-Fe2O3 heterojunction formation. Assessment of photocatalytic activity of all samples indicated that the sample prepared with 0.25 M of α-Fe2O3 precursor concentration (BT-TF-0.25) exhibited the most efficient bisphenol A photodegradation in aqueous solution. The highest photocatalytic activity of BT-TF-0.25 under simulated solar irradiation was mainly associated with C-doping and favorable heterojunction formation between C-doped TiO2 and C-doped α-Fe2O3. Excellent charge carrier and separation were confirmed from the photocurrent response and photoluminescence spectroscopy analysis. Overall, this study is expected to contribute to the development of more efficient visible light active heterojunction photocatalyst systems, as well as demonstrating the versatility of polysaccharide materials as a green and low-cost bio-templates.

The Direct Solution‐Process Crystallization of π‐Conjugated Small Molecules In‐Situ Integrated Planar Electrodes

Organic electronic devices have seen a new enthusiasm in flexible electronics. Indeed, they know new applications and improved performances even fabricated at low temperatures by low‐cost solution‐process and printing technologies. Nonetheless, some critical aspects remain to be improved, such as organic semiconductor (OSC) patterning and the control and alignment of organic crystal growth in the desired location and direction. Herein, a new controlled OSC solution‐growth processing, which directly occurs within planar electrodes patterning, is reported. A capillary‐driven flow occurs in air‐opened microchannels and then confines the OSC solution before growing these crystals in the desired region and direction. 1) The modeling, 2) fabrication, 3) experimental functionality of such capillary‐driven flow techniques, and 4) growth of OSC single‐colored crystals in situ integrated planar device electrodes are reported. Polarized optical images show large crystal growth (i.e., >100 μm) of typical π‐conjugated small molecules (diF‐TES‐ADT and C8‐BTBT). By such a technology, benefits from both 1) the meniscus‐guided coating mechanisms and 2) advantages of maskless and noncontact digital printing technologies are taken. Finally, these results visualize the directional control of OSC single‐crystal growth in a printing‐compatible (dispensing, inkjet) route in a reliable and reproducible way.

Effect of Dipotassium Hydrogen Phosphate and Calcium Nitrate on Strength and Microstructural Properties of Geopolymer Mortar

Adoption of coal fly ash (Class C) as the main source material for geopolymers would cause rapid setting to the fresh geopolymer mortar or concrete. This behaviour explained the limited application of this material in the construction industry. On the other hand, calcium nitrate (Ca (NO3)2) and dipotassium hydrogen phosphate (K2HPO4) are alternative admixtures that known to extend the setting time of fresh geopolymers. However, their effect on the strength and microstructural properties remain unclear due to the limitation of relevant literature from previous studies. Therefore, this study aims to investigate the effect of these admixtures in fly ash based geopolymer system, particularly to its strength performance. The effects of adding Ca (NO3)2 and K2HPO4 were evaluated at dosages of 0.5%, 1.5%, and 2.5% (by fly ash weight) in the geopolymer mixture, and samples were cured at room temperature. Hardened geopolymer specimens were measured for their compressive strength, porosity, and microstructural characteristic. The inclusion of 0.5% of alternative chemical reagents was found as the optimum proportion and able to enhance the compressive strength of the geopolymer mixtures. However, efflorescence was detected on the surface of the hardened specimen when K2HPO4 was included in its mixture. This phenomenon is influenced by the presence of monovalent and trivalent anions in the system namely nitrates and phosphates. In this study, each anion had a particular role in each stage of geopolymerisation, and determined the quality via crystal growth control and influenced the development of aluminosilicate structures.

Osteoporosis-related variations of trabecular bone properties of proximal human humeral heads at different scale lengths

Osteoporosis (OP) is a skeletal disorder responsible for the weakening of the bone structure and, consequently, for an increased fracture risk in the elderly population. In the past, bone mineral density (BMD) variation was considered the best OP indicator, but recently the focus has shifted toward the variation of microstructural bone parameters. This work is based on the characterisation of 8-mm cylindrical biopsies harvested from proximal humeral heads belonging to healthy and osteoporotic patients, in order to assess the OP-related variations of bone properties at different scale lengths. In particular, bone biopsies underwent micro-computed tomography analysis to study the most relevant features of bone architecture and extrapolate the tissue mineral density (TMD) value of bone trabeculae. Compression tests and nanoindentations were performed to investigate the macro- and micromechanical properties of bone biopsies, respectively. In addition, XRD analyses were performed to obtain the mean hydroxyapatite (HA) crystallite size, while Raman spectroscopy investigated the collagen secondary structure. Thermogravimetric analysis was performed to evaluate the ratio between organic and inorganic phases.From the obtained results, OP samples showed a more anisotropic and less interconnected structure responsible for reduced compression strength. From this, it can be supposed that OP caused an alteration of bone structure that led to inferior macroscopic mechanical properties. Furthermore, OP samples possessed higher TMD and bigger HA crystals that are correlated to an increase of the hardness value obtained by means of nanoindentation. This less controlled HA crystal growth is probably due to an alteration of the organic matrix structure, as revealed by the increase of the random coil contribution in the Raman spectra of the OP bone. This higher crystal content led to an increase in trabecular density and hardness. In conclusion, the obtained data showed that OP affects bone properties at different scale lengths causing an alteration of its morphological, structural and mechanical features.

Facile and Controllable Fabrication of High‐Performance Methylammonium Lead Triiodide Films Using Lead Acetate Precursor for Low‐Threshold Amplified Spontaneous Emission and Distributed‐Feedback Lasers

Organic–inorganic lead halide perovskites have emerged rapidly as the most attractive materials for photovoltaics in the last 10 years. Intense research has been done on crystal growth and morphology control to improve their power conversion efficiencies. Furthermore, perovskites also show great potential for optical amplification and lasing. Despite the numerous reports on how processing conditions affect the perovskite light‐harvesting properties, effects on amplified spontaneous emission (ASE) or lasing performance have attracted considerably less attention. Herein, a detailed study on the ASE performance of methylammonium lead triiodide (MAPbI3) films, processed with lead acetate (Pb(Ac)2) as lead source following a one‐step spin‐coating method and exposed to different post‐deposition conditions, is presented. It is found that the use of Pb(Ac)2 instead of lead iodide (PbI2) accelerates the crystal growth and simplifies the fabrication procedure. Even very thin MAPbI3 films (≈70 nm) can sufficiently support optical amplification and lasing in surface‐emitting distributed‐feedback (DFB) cavities. The facile and highly controllable MAPbI3 film formation observed with Pb(Ac)2 as precursor makes it a preferred choice with respect to PbI2 for future perovskite laser diodes.

Tuning crystal structure in a micro-scale reactive flow

In many industrial applications, ranging from chemical reactions to transport of suspensions, colloids can be produced and deposited within the processing equipment leading to significant fouling and clogging issues. Here, a continuous-flow reactor for the production of pharmaceutically relevant arylamines through the Buchwald-Hartwig synthesis is coupled to a microfluidic channel to investigate the complex interplay among fluid dynamics, crystallization, reaction and surface chemistry. The process of wall deposition and crystal formation under flow is studied in situ by fragmenting to the micron-scale the particles coming from the reactor and using glass microchannels. Tuning the flow rate, a dramatic change in crystal morphology and composition is found, from dendritic needle-like potassium tert-pentoxide structures to irregular colloidal clusters mainly made of potassium bromide. The results are characterized in terms of dimensionless parameters and provide novel insights for an improved understanding and control of fouling and crystal growth under flow.

Activating cadmium sulfide/bio-structured carbon composites by tuning (002) crystal plane for enhanced hydrogen evolution property

The Cadmium sulphide/bio-structured carbon composites are synthesized by a novel combination of calcination method and hydrothermal method. The purpose of converting the exposed face of the material from the (101) crystal to the (002) crystal plane is achieved by adding EDTA to the solution system during the hydrothermal process. The results show that the resulting composites retain the special structure of the original templates and the CdS of different exposed surfaces is significantly different in geometry. According to TEM and XRD phase analysis, the method of adding EDTA can effectively control the growth of exposed crystal faces in CdS. Photoluminescence spectroscopy demonstrates that the introduction of bio-structured carbon can improve the efficiency of photogenerated electron-hole pair separation. After 6 h of illumination, the photocatalytic decomposition of the surface-controlled composite material produced about 300 μmol of hydrogen, which is superior to the hydrogen production of the control material. In addition, combined with experimental data analysis and related literature, the mechanism of the combination of materials and the control of crystal growth is proposed, respectively.

Development of Methods for Controlling Crystal Growth Using Thermal Effect on Melt

The influence of low-energy thermal effects on the structural and concentration inhomogeneities in gallium-doped germanium single crystals, grown by directional solidification, has been investigated. A correlation of the thermal effects with the character of dopant distribution and interface shape change in grown crystals is established.

Constructing hierarchically hydrophilic/superhydrophobic ZIF-8 pattern on soy protein towards a biomimetic efficient water harvesting material

Inspired by the Stenocara beetle that can collect water from moist air in the Namib desert, here, we propose a simple dynamic control of crystal growth of ZIF on a natural polymer, soy protein. By adjusting the precursor concentration as well as the crystal growth time, hierarchical micro-/nano-crystals are constructed on the protein film surface. Taking advantage of the size difference of such crystals, selectively hydrophobic modification with a low surface-energy agent, stearic acid, can be performed on the surface, creating controllably hydrophilic/superhydrophobic patterns in favor of efficient water harvesting from fog. The effects of the as-prepared patterns on the water condensation behavior and collection efficiency are investigated; the maximum water collection efficiency, notably, can reach as high as 917.6 mg·cm−2·h−1. The results suggest that the biomimetic films hold a potential application in atmospheric water collection and the simple pattern-constructing approach is helpful to develop functional surface-patterned materials.

Control of ice crystal growth and its effect on porous structure of chitosan cryogels

We presented an improved preparation method to generate cryogels with controllable pore size. It included 5 stages: pre-cooling, pre-crystallization, crystal growth, freezing, and thawing (PPCFT); crystal growth was the key step. Chitosan (CS) cryogels with uniform and honeycomb-like structures were prepared with the method, and then the properties of these cryogels were studied. The results demonstrated that the mean pore diameters of CS cryogels were successfully controlled in a wide range (approximately 60–240 μm, by scanning electron microscope) by simply varying the temperature and time of crystal growth. The crystal growth law of this process was described by an empirical equation based on the classical theory for Ostwald ripening by Lifshitz, Slyozov, and Wagner (LSW). Furthermore, the hydrodynamics performance (permeability and column efficiency) of CS cryogel columns clearly varied with crystal growth conditions, while both the accessible porosity and water absorption ratio remained at a high level.

Solution-processed organic phototransistors based on controllable crystal growth of rubrene thin films with polymer-assisted layer

Crystalline rubrene films were fabricated by polymer-assisted layer in a sequential solution deposition process. Controllable crystal growth was achieved through varying the solution concentration of the polystyrene layers of the bilayer thin films. And the transitions from dendrites to spherulites were observed. The formation mechanism of rubrene crystals was proposed. Phototransistors based on rubrene thin film modified by PS-assisted layer showed a mobility of 1.67 × 10−3 cm2/Vs, a photoresponsivity of 4.7 μA/W, and a photosensitivity of 6900 under 200 mW/cm2 light power conditions. This process provides a valuable platform for studying the organic crystal growth and its photoelectric properties.

Artificial Compound Eyes Prepared by a Combination of Air-Assisted Deformation, Modified Laser Swelling, and Controlled Crystal Growth

This study presents the manufacturing process of bioinspired compound (BIC) eyes. The hierarchical eyes were accomplished by a combination of (i) modified laser swelling, (ii) air-assisted deformation, and (iii) controlled crystal growth. The results show that the addition of nanostructures on the surface effectively improved the water repellent performance with a contact angle (CA) of ∼160° and generally decreased the reflection by ∼25% in the wavelength range of 400-800 nm than the planar surface. Apart from these properties, the BIC eyes showed good optical performance. The convex structure has a circular shape and aspherical profile; this provides optical uniformity and constant resolution (full width at half-maximum = 1.9 μm) in all the directions. Furthermore, the BIC eyes reduced the imaging distortion by 1.5/3.4 and 2.3/3.1 times along the x and y axes, respectively, under 10° and 20° incident lights than a single lens. In the light acceptance range, the image displays almost no distortion.

Preparation of uniform newberyite crystal in nonaqueous system

Newberyite (MgHPO4·3H2O) is an important component of magnesium phosphate materials and has significant potential foreground in biomaterial field due to its high chemical stability, biocompatibility and biodegradability. However, newberyite has received lesser attention compare with other magnesium phosphate materials. Nonaqueous synthetic routes to oxide and phosphate materials provide certain advantages, such as a better control of nucleation and crystal growth and higher crystallinity at low temperature. To the best of our knowledge, newberyite synthesized in nonaqueous system has no relevant literature record. Therefore, we report a new method to synthesis newberyite, using MgCl2·6H2O as magnesium source and H3PO4 as phosphorous source in nonaqueous system. The method is facile, convenient and without surfactant. The products have a widespread prospect for applying in biomaterial field, such as tissue engineering and bone replacement.