Colloid Chemistry Research Articles

Assembly of planar chiral superlattices from achiral building blocks

The spontaneous assembly of chiral structures from building blocks that lack chirality is fundamentally important for colloidal chemistry and has implications for the formation of advanced optical materials. Here, we find that purified achiral gold tetrahedron-shaped nanoparticles assemble into two-dimensional superlattices that exhibit planar chirality under a balance of repulsive electrostatic and attractive van der Waals and depletion forces. A model accounting for these interactions shows that the growth of planar structures is kinetically preferred over similar three-dimensional products, explaining their selective formation. Exploration and mapping of different packing symmetries demonstrates that the hexagonal chiral phase forms exclusively because of geometric constraints imposed by the presence of constituent tetrahedra with sharp tips. A formation mechanism is proposed in which the chiral phase nucleates from within a related 2D achiral phase by clockwise or counterclockwise rotation of tetrahedra about their central axis. These results lay the scientific foundation for the high-throughput assembly of planar chiral metamaterials.

Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability.

Increasing demand for effective energy conversion materials and devices has renewed interest in semiconductors comprised of earth-abundant and biocompatible elements. Alkaline-earth sulfides doped with rare earth ions are versatile optical materials. However, relatively little is known about controlling the dimensionality, surface chemistry, and inherent optical properties of the undoped versions of alkaline-earth mono- and polychalcogenides. We describe the colloidal synthesis of alkaline-earth chalcogenide nanocrystals through the reaction of metal carboxylates with carbon disulfide or selenourea. Systematic exploration of the synthetic phase space allows us to tune particle sizes over a wide range using a mixture of commercially available carboxylate precursors. Solid-state NMR spectroscopy confirms the phase purity of the selenide compositions. Surface characterization reveals that bridging carboxylates and amines preferentially terminate the surface of the nanocrystals. While these materials are colloidally stable in the mother solution, the selenides are susceptible to oxidation over time, eventually degrading to selenium metal through polyselenide intermediates. As part of these investigations, we have developed the colloidal syntheses of barium di- and triselenides, two among few reported nanocrystalline alkaline-earth polychalcogenides. Electronic structure calculations reveal that both materials are indirect band gap semiconductors. The colloidal chemistry presented here may enable the synthesis of more complex, multinary chalcogenide materials containing alkaline-earth elements.

Fabrication, characterization and optimization of industrial alpha alumina powders based ceramic membrane supports and its applicative potential for CO2/N2 separation

In this investigation, an economically feasible strategy has been proposed for the fabrication of good quality membrane support by utilizing low-cost industrial-grade alumina powders, coded as A-16SG and CT-1200SG with an average particle size of 0.44 and 1.41 µm, respectively. Herein, the meticulous alteration of the processing parameters and the targeted utilization of industrial grade powders with distinctive particle morphologies have shown promising aspect towards governing the overall sintering and densification behavior, pore morphology and the microstructural facets of the sintered alumina compacts. More precisely, while connecting the structure-property relationship aspect, the broader particle size distribution and the higher quartile ratio of CT-1200SG powders lends to originate relatively higher average pore size and wider pore size distribution in the as-optimized sintered membrane support system in comparison to the narrow particle sized and low quartile ratio comprising A-16SG powder. Additionally, the near surface morphology of the intermediate layers deposited over the two distinctive membrane support systems via implementing differential colloidal chemistry of the respective sols have also been demonstrated for the precise understanding of the role of particle morphology on the progressive perseverance of pore characteristics of the overall asymmetric graded membrane substrate. Finally, the performance evaluation of the alumino-silicate membrane layer assembled on the tailor-made multilayered graded cost-competent alumina support system has been executed which revealed comparable CO2/N2 gas permeance of 46.44GPU and 534.25GPU along with the selectivity of 12.5 and 1.9 for the respective A-16SG and CT-1200SG powders based individual support systems under nearly identical flue gas separation conditions.

Viscoelastoplastic classification of cementitious suspensions: transient and non-linear flow analysis in rotational and oscillatory shear flows

Rheological modeling of special concretes such as ultra-high performance concretes (UHPCs), self-compacting concretes (SCCs), or environmentally friendly concretes with low clinker contents but containing many fine particles increases model complexity because high amounts of colloidal and fine particles and complex chemistry result in strongly non-Newtonian rheological behavior. Straight-forward viscoplastic rheological models such as the well-known Bingham- or Herschel-Bulkley approach do not fit the flow behavior on a large scale at and lead to boundary value problems in numerical flow simulations. Increased viscoelastic properties due to chemical admixtures are not described by pure viscoplasticity analysis methods. To fill this gap, our research presents viscoplastic and viscoelastic linear and non-linear rheological characterization methods for common and strongly non-Newtonian cement pastes and combines the methods for a comprehensive viscoelastoplastic modeling of cementitious building materials. We illustrate and discuss the benefits and boundaries of each measurement technique in dependence of cementitious paste complexity. Three solid volume fractions from phi = 0.45 to 0.55 and three different flowability ranges, adjusted through varying superplasticizer amounts, were investigated in respect of steady-state and transient yield stress, viscosity, and non-linear viscoelastic material properties. Our results reveal that with increasing solid volume fraction and polymer amount, viscoelastoplastic modeling describes rheological flow on a large flow scale more appropriately than common viscoplastic methods. The results show a new approach for a full quantitative and qualitative rheological classification of cementitious building materials and thus improve the understanding of densely packed colloidal cementitious suspensions. The findings serve as prospective guideline to model complex cementitious building materials both at low and high shear rates, and to find an appropriate rheological description at the boundaries of flow.Graphical abstract

Halide perovskites as disposable epitaxial templates for the phase-selective synthesis of lead sulfochloride nanocrystals

Colloidal chemistry grants access to a wealth of materials through simple and mild reactions. However, even few elements can combine in a variety of stoichiometries and structures, potentially resulting in impurities or even wrong products. Similar issues have been long addressed in organic chemistry by using reaction-directing groups, that are added to a substrate to promote a specific product and are later removed. Inspired by such approach, we demonstrate the use of CsPbCl3 perovskite nanocrystals to drive the phase-selective synthesis of two yet unexplored lead sulfochlorides: Pb3S2Cl2 and Pb4S3Cl2. When homogeneously nucleated in solution, lead sulfochlorides form Pb3S2Cl2 nanocrystals. Conversely, the presence of CsPbCl3 triggers the formation of Pb4S3Cl2/CsPbCl3 epitaxial heterostructures. The phase selectivity is guaranteed by the continuity of the cationic subnetwork across the interface, a condition not met in a hypothetical Pb3S2Cl2/CsPbCl3 heterostructure. The perovskite domain is then etched, delivering phase-pure Pb4S3Cl2 nanocrystals that could not be synthesized directly.

The role of reverse micelles and metal-surfactant interactions in the synthesis of gold ink in reverse emulsions stabilized by AOT, Tergitol NP-4 and Span 80

The development of advanced methods for the synthesis of metal-containing solvent ink is important for 2 and 3D printing as well as for obtaining composites of nanoparticles with hydrophobic polymers. The formation mechanism of gold organosols in reverse emulsions stabilized by the widely used surfactants AOT, Tergitol NP-4 or Span 80 was investigated. It was found that the main factors promoting the successful synthesis are the presence of small size reverse micelles in a dispersion medium and the occurrence of interaction of a surfactant with the complex anion AuCl4–. The interaction provides a rapid transfer of gold ions from the micron size emulsion droplets to nanometer micelles. After that, the micelles play their conventional role of nanoreactors, limiting the growth and stabilizing a nanoparticle during the reduction of AuCl4– by hydrazine. After destruction of the emulsion and separation of the aqueous phase, the sols were subjected to additional electrophoretic concentration. It was demonstrated that the obtained concentrate can be used as the solvent ink to form conductive films and composites of nanoparticles with hydrophobic polymers like polystyrene, where nanoparticles retain the properties of plasmonics. The novelty and significance of the study in terms of colloidal and surface chemistry consist in the fundamental and experimental substantiation of the new and promising application of such a classical colloid as reverse emulsions.

МЕТОДИЧНІ АСПЕКТИ ВИКЛАДАННЯ ДИСЦИПЛІНИ «ФІЗИЧНА І КОЛОЇДНА ХІМІЯ» ДЛЯ МАЙБУТНІХ ВЧИТЕЛІВ ХІМІЇ

Teaching would-be teachers of Chemistry disciplines should be specific due to the necessity of practice aimed training of would be professional teachers. Wholesome methodological training of professional Chemistry teachers can be provided by strengthening professional and pedagogical aiming of studying fundamental Chemistry disciplines. Implementation of this idea means development of the methods of professionally oriented studies of the courses of Chemistry disciplines and the course of Physical and Colloid Chemistry in particular. This approach provides shaping would be Chemistry teacher’s professionally significant competences, contributes to training professionals beginning with the freshmen years. From the point of view of would be Chemistry teacher training not only student professional competences should be shaped but also attention should be paid to methodological aiming in teaching it. While studyingbases of Physical and Colloid Chemistry, along with classical teaching methods special attention is paid to teaching methods, which are professionally aimed, which makes it possible to shape both competences in the field of the studied discipline and methodological competences necessary for would be Chemistry teachers. In the article key, general professional, special subject and subject methodological competences are identified, which are shaped at competence aimed teaching of Physical and Colloid Chemistry. Examples are given of shaping methodological competences in the lecture course, laboratory practice as well as during extracurricula work. Attention is paid to the application of the technology of tutor accompaniment of students, or mutual teaching principle, while doing the course of Physical and Colloid Chemistry, tasks for the tutor are offered, which are clearly professionally and methodologically aimed. Professional and methodological aiming of the course of Physical and Colloid Chemistry accompanied by fundamental training creates conditions for more successful development of professional competences. At the same time it promotes wholesome, system training of students, makes it possible for them to master the Methods of Chemistry material better and to feel at ease during school teaching practice.

Heterostructured Nanoscale Photocatalysts via Colloidal Chemistry for Pollutant Degradation

With the further acceleration in the industrialization process, organic pollutants and gas pollution in the environment have posed severe threats to human health. It has been a global challenge regarding achieving an efficient solution to pollutant degradation. In such a context, photocatalysts have attracted researchers’ attention for their simplicity, efficiency, cleanliness and low cost. However, the single photocatalyst is facing a research bottleneck owing to its narrow light absorption spectrum and high photocarrier recombination rate. Given that heterojunctions can achieve efficient separation of photogenerated carriers in space, constructing heterostructured photocatalysts has become the most perspective method to improve the performance of photocatalysts. Furthermore, nanoparticles prepared through colloidal chemistry have the characteristics of high dispersion, stability and adsorption, further enhancing the degradation efficiency of heterostructured photocatalysts. This article reviews the primary methods for preparing heterostructured photocatalysts through colloidal chemistry, classifies the heterojunction types by transport routes of photogenerated carriers and summarizes the recent progress of heterostructured photocatalysts in pollutant degradation. To implement environmental remediation, it is crucial to explore economical and efficient photocatalysts for practical applications. It is hoped that this review will stimulate further exploration of colloidal heterostructured photocatalysts for pollutant degradation.

Formation of a Giant Anisotropically Ordered Assembled Structure of Inorganic Nanosheets through an Optically Induced Stream.

Formation of a desirable submillimeter-scaled assembled structure of particles in the colloid is a difficult subject in colloidal chemistry. Herein, a submillimeter-scaled ordered assembled structure consisting of highly anisotropic two-dimensional plate-like particles, niobate nanosheets, was obtained through an optical manipulation technique that was assisted by a scattering-force-induced stream. A 532 nm continuous wave laser beam with a power of 400 mW was used to illuminate a liquid crystalline niobate nanosheet colloid from the bottom side of a sample cell, inducing the stream of oriented nanosheets toward the upper side of the sample cell. As a result, a 200 μm ordered assembled structure consisting of oriented nanosheets was formed. The assembled structure was also characterized by two-dimensional anisotropy, reflecting that the highly anisotropic morphologies of each nanosheet and the shape of that structure were dependent on the polarization of incident illumination. This study has revealed a new noncontact and on-demand way to obtain submillimeter-scaled ordered anisotropic colloidal assembled structures of nanosized particles such as nanosheets, contributing to fundamental materials science and expanding the utilities of nanosheets.

Solid–Solution–Solid (SSS) phase transitions for Gram-Scale and High-Throughput synthesis of noble metal nanoparticles in deep eutectic solvents

Modern colloidal chemistry has enabled the controlled synthesis of various noble metal nanoparticles with unique physical and chemical properties. However, solution-based synthesis still suffers from limited productivity, particularly in industrial applications. We have developed the gram-scale synthesis of gold nanoparticles (AuNPs) using a polymerizable deep eutectic solvent (DES) via solid–solution–solid phase transitions. The DES plays two important roles, as a designer solvent. First, the solvating power of the DES allows the precursors to dissolve easily, even at high concentrations. Second, the concomitant polymerization of the DES with the synthesis of highly concentrated AuNPs and their consequent fixation in the polymer matrix is crucial for their stabilization. This rapid one-pot synthesis provides the highest productivity, among the other previously reported gram-scale syntheses of AuNPs. The procedure can be easily extended to conduct multiple reactions in a high-throughput manner. The chemical and physical properties and synthesis mechanisms of the AuNPs are thoroughly investigated. The synthesis of other noble metal (Pd, Ag, Au) nanoparticles, which are mono- and bimetallic, has also been demonstrated using the DES. As a practical application, a large-area transparent display is demonstrated using AuNPs synthesized in the DES, implying the scope for further industrial applications.

Space-confined growth of 2D MOF sheets between GO layers at room temperature for superior PDMS membrane-based ester/water separation

Expanding the metal–organic frameworks (MOFs) category using room-temperature colloidal chemistry route with regular crystal structure is challenging, but important for reducing energy consumption and realizing an economically viable application in industry. Herein, we developed a novel advanced copper terephthalate MOF (CuBDC) between graphene oxide (GO) layers using a simple space-confined growth strategy at room temperature. The inclusion of CuBDC@GO can realize high filler loadings while maintaining uniform dispersion throughout PDMS matrix. The paralled arranged CuBDC sheets created 1D inner vertical channels, along with the enlarged GO interlayer space for rapid molecule permeselective transport. The resultant mixed matrix membranes (MMMs) with 30 wt% CuBDC@GO loading improved the separation factor from 190.6 to 576.3, and simultaneously increased the total flux from 575.2 to 1357.4 g m-2 h-1 for separating 0.5 wt% butyl acetate at 40 °C. The transport mechanism was explained by adjusting the CuBDC content in composites to examine the significant increase in membrane permeability (from 12.5 to 58.3) and selectivity (from 0.7 to 2.0). Compared to alcohol or ketone, the larger size strip-like butyl acetate molecules are ideal for rapid transport through the CuBDC-supported 1D continuous inner channels, and effectively inhibit the movement of water molecules, ultimately resulting in the largest pervaporation performance improvement in butyl acetate/water separation. This CuBDC@GO prepared by a simple, green and room-temperature synthesis route can be widely applied to prepare defect-free membranes with excellent performance for sustainable applications. We also anticipate that this advanced space-confined growth strategy can be extended to various other MOFs and applications.

Introducing Video-Recorded Lab Experiments into Assignments for Surface and Colloid Chemistry Students

This communication describes our initial experience modifying traditional (written and calculation-based) assignments in the surface and colloid chemistry course given as a part of the chemical engineering program. The new exercises contain a more relatable context that is easier to understand and remember in terms of future challenges in student’s professional career. These modified exercises deepen the level of the exercise by adding the working principle of the measurement and visualization of a lab experiment, instead of simply requiring the student to solve a set of problems. All videos were made and edited using in-house instrumentation and easily accessible tools (tripods, mobile phones, etc.). Analysis of the result of these new assignments showed that the average score was slightly below the means for the other exercises; interestingly, however, the students needed fewer attempts to solve these, which was possibly a sign of a better initial understanding of the questions. Furthermore, through a postassignment survey, we found that many students had a positive attitude toward this new form of introducing exercises and, in general, found them more engaging. Still, some comments pointed out a few shortcomings of the new type of exercises, which will be considered while continuously improving the existing exercises and formulating new ones. Overall, encouraged by the feedback, we plan to continue modifying the content of the assignments using this approach and consider other use of the prepared videos, for example, for instrument training purposes or promotional materials for the research group.

Self-assembled bilosomes with stimuli-responsive properties as bioinspired dual-tunable nanoplatform for pH/temperature-triggered release of hybrid cargo

The rapid development of colloid chemistry has raised the possibility of using nanocarriers for the targeted delivery and the controlled drug release at predictable locations to reduce side effects and enhance therapeutic efficacy. In the present work, we focused on the influence of temperature and pH upon in vitro controlled phytochemical/dye-release from a modified bilosome. Drug molecules can affect the properties of nanocarriers, so the effect of encapsulated bioactive compounds on nanoparticle structure has been investigated. The self-assembly process of bioinspired components (i.e., phospholipids, bile salts, and cholesterol), and biocompatible polymeric triblock materials, made it possible to receive structures with a size below 100 nm, demonstrated good capacity for active cargo encapsulation. Differential scanning calorimetry studies showed the possibility of the payloads’ interaction with the bilosomes structure. A highly lipophilic compound, such as curcumin, can weaken hydrophobic interactions between the acyl chains of phospholipids, leading to a more flexible membrane. The in vitro release profiles have proved that both solubilities of the therapeutic substances and various environmental conditions affect the release rate of the hybrid cargo. Overall, the obtained double-loaded bilosomes represent a promising bioinspired nanoplatform for oral, intravenous, and topical drug delivery in future biomedical applications.

Pengembangan E-Modul pada Materi Koloid untuk Meningkatkan Kemampuan Berpikir Kreatif Peserta Didik

This study is a research and development that aims to develop electronic modules using Flip PDF Professional on colloid material to improve students' creative thinking skills that are valid, practical, and effective to be used. The development model used refers to the ADDIE development model which consists of 5 stages, namely analysis, design, development, implementation, and evaluation. The electronic module developed using Flip PDF Professional software had been validated by material expert and media expert and had gone through a trial phase to produce a valid, practical, and effective Colloid Chemistry electronic module. The Colloid Chemistry E-module product made with Flip PDF Professional is attractively designed because it contains colloid learning video and animation, and is practical in its use because students can easily access it on their respective androids without having to use additional applications. The subjects in this study were students of grade XI MIPA 3 at UPT SMAN 2 Parepare City. The results show that the Colloid Chemistry electronic module developed using Flip PDF Professional software obtained 88.5% validity by material expert and 86.12% validity percentage by media expert, so the validator criteria for the electronic module obtained as valid. The Colloid Chemistry electronic module developed using Flip PDF Professional software is stated to be practical because the practicality test obtained an average of 3.625 with practical criteria from the results of teacher’s responses and an average of 3.772 from students’ responses with practical criteria. The electronic product of the Colloidal Chemistry module also meets the effectiveness criteria based on the test result of students' creative thinking skills after using the developed colloid chemistry module, where students' creative thinking skills are dominated at level 3, namely creative.

油水界面上表面活性剂的脱附动力学及其离子调控

<p indent="0mm">The oil-water interface plays a crucial role in daily life and many industrial processes (such as oil extraction, emulsion preparation, material assembly, drug transportation, etc.). With the development of scientific research and engineering applications, the structures and properties of the oil-water interfaces are becoming the focus and the advanced subjects of multiphase flow, colloid and interface chemistry, microfluidics, material assembly and many other fields, and are more difficult to be predicted and described via the existing methods and theories. Surfactants, which are amphiphilic molecules, can spontaneously adsorb at the oil-water interfaces and have been proved to be effective materials for regulating the structures, mass transfer and mechanics of the oil-water interface. It is of great significance to investigate the surfactant kinetics at the oil-water interface for revealing the interfacial adsorption and regulation mechanisms of surfactants. The adsorption/desorption process is the rate-limiting step of surfactant kinetics at the oil-water interface. However, many studies focus on the relaxation process of surfactant adsorption, and the effects of ions in the aqueous phase on the surfactant adsorption/desorption kinetics are scarcely investigated. In this paper, by combing the coarse-grained molecular dynamics simulations and the umbrella sampling method, we study the desorption process of SDS surfactants from the decane-water interface and reveal the mechanisms of ions affecting the desorption kinetics and interfacial tension by analyzing the surfactant desorption kinetics via the desorption free energy and desorption time. The results show that ionic species and concentration have great influence on the ionic number density and SDS-ion interaction near the interface, but show little effects on the number density and molecular conformation of surfactants at the interfaces. Based on the umbrella sampling simulation and Smoluchowski equation, we give an accurate and quantitative description of the surfactant desorption from the interfaces, and obtain the desorption free energy and desorption time of surfactants. The desorption free energy and desorption time decrease with SDS adsorption number or interfacial concentration increasing, indicating that the enhanced interaction between SDS molecules promotes the desorption. Both the desorption free energy and the desorption time increase with ionic concentration increasing and we attribute this variation trend to the electrostatic shielding induced by ions. The ions shield the interaction between SDS molecules and thus inhibit the desorption of surfactants from the oil-water interfaces. Calcium ion with stronger electrostatic shielding has stronger inhibition effects. By analyzing the desorption kinetics of surfactants and oil-water interfacial tension, we obtain that the desorption ability of SDS is negatively correlated with its ability to reduce interfacial tension. The ions can weaken the ability of SDS to reduce interfacial tension by inhibiting the desorption kinetics of SDS from interfaces, and the weaken effect of calcium ion on SDS reducing interfacial tension is more significant. The results show that the adsorption/desorption kinetics of surfactants at interfaces as well as the interfacial tension can be effectively regulated by changing the ion species and concentrations properly, which provide a theoretical basis for the development of oil-water interfacial characteristics regulation technologies based on the coupling of ions and interfacial active components.

Artificial nanomotors: Fabrication, locomotion characterization, motion manipulation, and biomedical applications

AbstractArtificial nanomotors are nanoscale machines capable of converting surrounding other energy into mechanical motion and thus entering the tissues and cells of organisms. They hold great potential to revolutionize the diagnosis and treatment of diseases by actively targeting the lesion location, though there are many new challenges that arise with decreasing the size to nanoscale. This review summarizes and comments on the state‐of‐the‐art artificial nanomotors with advantages and limitations. It starts with the fabrication methods, including common physical vapor deposition and colloidal chemistry methods, followed by the locomotion characterization and motion manipulation. Then, the in vitro and in vivo biomedical applications are introduced in detail. The challenges and future prospects are discussed at the end.

Exploring the surfactant structure efficacy in controlling growth and stability of HgS nanoparticles in aqueous medium

Surfactants exhibit many inherent properties, one of the properties is their favorable capacity to absorb at the interface or surface in which surfactant molecules are transferred from bulk phase of solution to the interface. With the evolution in the synthesis routes of nanoparticles (NPs) via colloidal chemistry approaches, now the adsorption capacity of surfactants is being exploited concerning the stabilization of the NPs. In present research work, colloidal mercuric sulfide nanoparticles (HgS NPs) have been synthesized with effective sizes below 15 nm in aqueous solutions of various surfactants through facile chemical precipitation technique. Different head groups and hydrophobic chain length moieties have been tested for various cationic and anionic surfactants. These surfactants have been demonstrated to produce dispersed spherical configured HgS NPs, in which the composition of surfactant has controlled growth assessment. Although, the NPs in the pulverized form exhibit β-HgS form except of the surfactant opted. Surfactant adsorption at the surface of NP has been shown due to change in inter-particle potential and prevents the self-aggregation of NPs. Additionally, it has been demonstrated that the surfactants (stabilizers) have some favorable chemical moiety which promotes the binding at NP surface, generates an adequate size of particles and eventually inhibits their unlimited growth. The kinetics of nucleation and growth of surfactant stabilized HgS NPs follows the first-order rate law in all the surfactants. However, the first order rate constant has shown prominent surfactant dependence.

Laser-Induced Morphological and Structural Changes of Cesium Lead Bromide Nanocrystals.

Metal halide perovskite nanocrystals, an emerging class of materials for advanced photonic and optoelectronic applications, are mainly fabricated with colloidal chemistry routes. On the quest for new properties according to application needs, new perovskite systems of various morphologies and levels of doping and alloying have been developed, often also involving post-synthesis reactions. Recently, laser irradiation in liquids has been utilized as a fast method to synthesize or transform materials and interesting laser-induced transformations on nanocrystals were induced. These studies in general have been limited to small nanocrystals (~15 nm). In the case of halide perovskites, fragmentation or anion exchange have been observed in such laser-based processes, but no crystal structure transformations were actually observed or deliberately studied. Nanocrystals are more sensitive to light exposure compared to the corresponding bulk crystals. Additional factors, such as size, morphology, the presence of impurities, and others, can intricately affect the photon absorption and heat dissipation in nanocrystal suspensions during laser irradiation. All these factors can play an important role in the final morphologies and in the time required for these transformations to unfold. In the present work, we have employed a 513 nm femtosecond (fs) laser to induce different transformations in large nanocrystals, in which two phases coexist in the same particle (Cs4PbBr6/CsPbBr3 nanohexagons of ~100 nm), dispersed in dichlorobenzene. These transformations include: (i) the exfoliation of the primary nanohexagons and partial anion exchange; (ii) fragmentation in smaller nanocubes and partial anion exchange; (iii) side-by-side-oriented attachment, fusion, and formation of nanoplatelets and complete anion exchange; (iv) side-by-side attachment, fusion, and formation of nanosheets. Partial or complete Br-Cl anion exchange in the above transformations was triggered by the partial degradation of dichlorobenzene. In addition to the detailed analysis of the various nanocrystal morphologies observed in the various transformations, the structure–photoluminescence relationships for the different samples were analyzed and discussed.

Highly Stable 3D Supercuboids to 2D ZnSe Nanosheets: Formation for a High-Efficiency Catalysis System.

Assembling into desired and higher-ordered superstructures makes nanocrystals superior candidates in a wide range of applications. Herein, we report a facile but robust colloidal chemistry method to obtain three-dimensional (3D) supercuboids from two-dimensional (2D) ZnSe nanosheets. It is well-defined that the formation mechanism of the supercuboids is based on the interaction among ligands on the ZnSe nanosheets. The highly stable supercuboids are composed of nanosheets with thickness of approximately ∼1.4 nm, and the spacing between two nanosheets in the supercuboid is revealed as ∼1.2 nm. Importantly, 2D nanosheets are readily regained by an exfoliation process of 3D supercuboids in a high-temperature solvothermal process. Furthermore, the Au@ZnSe heteronanosheets could be obtained by Au nanoparticles (NPs) decorated on 2D nanosheets. As a proof-of-concept application, the ZnSe nanosheets are applied in the catalysis of the aldol condensation reaction, which shows the high isolated yield of chalcone up to 80%.

THE X-RAY DIFFRACTION ANALYSIS OF A COMPLEX OXIDE CATALYST OF 50%Cu3(PO4)2•50%Ni3(PO4)2

Preparation of initial orthophosphates of Copper (II) and Nickel (II) and a complex catalytic system based on them 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 was carried out according to the methods developed at the Department of Physical and Colloid Chemistry, of Uzhhorod National University. The synthesized system was investigated by X-ray phase analysis. Experimental diffraction patterns show that air-dry samples of the initial components and the intermediate sample of 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O are very different from each other. This gives grounds to assume that the air-dry phosphate of the catalytic system 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O can be characterized as a new phase. Annealing of the obtained air-dry complex sample in the temperature range 120-700ºС leads to the corresponding physicochemical transformations. Experimental data show that the structure of the formed intermediate air-dry sample after heat treatment undergoes significant changes. At the same time, heat treatment leads to gradual partial or complete dehydration of a complex catalytic system. When 600ºC is reached, the dry X-ray amorphous catalyst begins to crystallize. This is due to the gradual dehydration of the catalyst at lower temperatures with the loss of much of the chemically bound water and the transition to the amorphous state. The process of forming the crystal structure of the dehydrated complex sample is significantly intensified when reaching 700ºC. Thus, the calcination of the synthesized phosphate phase in the specified temperature range allows not only to carry out its complete dehydration, but also, to a large extent, promotes the gradual crystallization of the dehydrated phase. In turn, this causes the formation on the surface of the synthesized complex copper-nickel phosphate catalyst system of 50%Cu3(PO4)2∙3H2O•50%Ni3(PO4)2∙8H2O acid active centers of appropriate strength. It was also found that if necessary to obtain a fully dehydrated and crystallized copper-nickel-phosphate sample, the duration of calcination at a final temperature of 700ºC should be carried out more than 1 hour.&#x0D; Keywords: X-Ray Diffraction (XRD) analysis; catalysts; сopper (II) orthophosphate; nickel (II) orthophosphate; catalytic 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 system.