Structure Memory Effect Research Articles

Electrostatic self-assembly of hydrotalcite-based g-C3N4 composites for adsorption and photocatalytic degradation of aqueous norfloxacin

Norfloxacin, a quinolone antibiotic pollutant, posed a significant threat to environment and human being health. In this study, hydrotalcite-based g-C3N4 composites were produced using electrostatic self-assembly and the structural memory effect of hydrotalcite to optimize their adsorption-degradation of norfloxacin under visible-light illumination. Optimized hydrotalcite and g-C3N4 composite (750°C, 40 wt% of g-C3N4) exhibited a highest photo-degradation rate constant of 1.8×10−2 min−1 with 83.98 % norfloxacin degradation achieved within 1.5 h under visible-light, surpassing that of bare g-C3N4 and hydrotalcite photocatalysts. The synergistic effects of the composite, such as uniform flower-like micro-morphology and rich mesoporous structure, resulted in a large specific surface area (58.67 m2/g), abundant active sites, and good photo-generated charge separation efficiency. All these facilitated both sorption (7.95 mg/g) and subsequent visible-light degradation of norfloxacin. Furthermore, the superior photocatalytic performance observed in the degradation of norfloxacin under visible-light illumination was assigned to the effective transport of photogenerated electrons and holes between hydrotalcite and g-C3N4 components. The work highlights the potentials of hydrotalcite and g-C3N4 composites as an excellent photocatalyst for environment remediation and water treatment.

Employing dolomite as magnesium source to prepare calcined layered double hydroxides for chromium contaminated soil treatment: Exploring the influence of temperature, bioavailability, and microbial diversity

Layered double hydroxides (LDH-D) and their calcined counterparts, using dolomite as a source of magnesium, were utilized for the immobilization of chromium (Cr(VI)) in soil. The results indicate that LDH-D, both with and without varying calcination temperatures, can effectively immobilize Cr(VI) in soil. Among the different calcination temperatures tested, LDH-D subjected to calcination at 500 °C (LDH-D-500) showed particularly high efficacy. Long-term TCLP experiments demonstrated the inhibition of soil-to-plant transmission of Cr(VI), thereby highlighting the long-lasting immobilization capacity of LDH-D and its calcined derivatives. Furthermore, the analysis of the microbial community's adaptation in post-remediation soil confirmed the durability and bioavailability of LDH-D-500 for Cr immobilization. Examination of the material's morphology and structure after immobilization shed light on the mechanism of immobilization in soil. The results revealed that interlayer anion exchange and surface adsorption were the main factors responsible for the effective immobilization of LDH-D and LDH-D-300. On the other hand, LDH-D-900, with a dominant spinel (MgAl2O4) structure, faced challenges in returning to its original layered configuration, making surface adsorption the primary mechanism for immobilization. LDH-D-500 primarily relied on the structure memory effects of LDHs to immobilize Cr(VI) through structural recovery processes, facilitated by electrostatic attraction and surface adsorption. It is also important to note that CaCO3 plays an important role in adsorption. Additionally, a portion of Cr(VI) was converted to Cr(III) through phenomena such as isomer substitution and complexation adsorption. The proficiency of LDH-D-500 in immobilizing Cr, its ability for instantaneous separation, and the potential for regeneration make it a promising material for remediation of heavy metal-contaminated soil. The investigations suggest that the use of dolomite to create hydrotalcite and calcining it at 500 °C could effectively render environmental Cr inactive, thereby optimizing resource utilization.

Development of high-dispersion CLDH/carbon dot composites to boost chloride binding of cement

Chloride-induced corrosion of steel reinforcement significantly contributes to the durability deterioration for reinforced concrete (RC) structures. Calcined layered double hydroxide (CLDH) possesses a distinctive structure memory effect to adsorb anions and a nucleation effect to facilitate cement hydration, thereby demonstrating a promising potential for chloride binding enhancement of cementitious materials. However, CLDH suffers from severe agglomeration in cement composites, limiting its performance efficacy. To tackle this problem, novel high-dispersity CLDH/carbon dots (CDs) composites (CC) only at small dosages are applied to greatly improve the chloride binding behavior of cement pastes for the first time. In detail, the specific surface area of CC synthesized by simply stirring CDs and CLDH improves by 166.4 % than that of pure CLDH. Remarkably, cement pastes containing CC display a preferable chloride binding capacity; And the chloride binding substantially increases by 52.41 % when the incorporation of CC (by weight of cement) is 0.8 wt%. More importantly, according to the phase composite and microstructure analyses, the chloride binding enhancement mechanism of CC-containing cement pastes is reasonably ascribed to two effects of CC: providing nucleation sites to accelerate cement hydration and exerting the inherent chloride adsorption capacity. This boosts the formation of C–S–H gels and improves the structure memory effect and anions exchange-induced chloride adsorption, thus significantly strengthening the chloride binding of cement. This work provides a novel approach to improve the dispersity of CLDH, effectively strengthening the chloride binding of cement, thereby conductive to prolonging the service life of RC structures.

Switchable surface and loading/release of target molecules in hierarchically porous PLA nonwovens based on shape memory effect.

In this work, hierarchically porous PLA (polylactic acid) shape memory nonwovens were prepared by electrospinning its blend solution with PEO (polyethylene oxide) and subsequent water etching. Based on shape memory effect resulting from tiny crystals and the amorphous matrix of PLA, the switch between compact and porous surfaces has been achieved via cyclical hot-pressing and recovery in a hot water bath. After hot-pressing, the disappearance of hierarchical pores contributes to compact surface, enabling embedding of the target molecule in PLA nonwoven (i.e., CLOSE state). Upon exposure to heat, PLA nonwoven recovers to its permanent shape and exhibits a porous surface, providing a penetrative diffusion pathway for small molecules (i.e., OPEN state). The hierarchically porous structure and shape memory effect endow PLA nonwoven with the capability of rapid release. Our results provide a good candidate for some potential applications, such as temperature-controlled quick-release of catalysts and drugs.

NO reduction with CO on metal nanoparticles/layered double hydroxides heterostructures obtained via the structural memory effect

Nitrogen oxides are notorious air pollutants and the catalytic reduction of NOx by CO for removing NOx has attracted extensive attention. Herein, we present a series of ZnCu-layered double hydroxides (LDH) decorated with nanoparticles of metals (Me: In, Zn or Au) and the derived oxides as novel catalysts for NO reduction by CO. MeNP/ZnCu heterostructures were successfully prepared by taking advantage of the structural reconstruction of ZnCu LDH, via the structural memory effect, in the aqueous solutions of Me salts. X-ray diffraction (XRD), FTIR spectroscopy, H2-Temperature programmed reduction (H2-TPR), transmission electron microscopy TEM, X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy have been used to characterize the structural, chemical composition, optical and nano/micromorphology of MeNP/ZnCu catalysts and the mixed oxides derived after the thermal treatment. Results indicate that on MeNP/ZnCu the reduction of NO by CO was 3 times higher than that of ZnCu while CO conversion was above 90%. Further, MeNP/ZnCu and the derived oxides demonstrated good stability in subsequent catalytic cycles while NO conversion was influenced by the molar ratio O2/CO. These findings indicate that the memory effect of the LDH can be effective as a simple strategy in the development of novel LDH-based heterostructured catalysts.

In-situ constructed ultrathin hydrotalcite derivative supported PtIn catalyst for isobutane direct dehydrogenation

The stable and ultrathin hydrotalcite nanosheets with thickness of ca. 1.0 nm have been built on the surface of Al2O3 by sharing Al element and using layer growth inhibitor formamide. Based on the topological transformation characteristics of hydrotalcite and the structural memory effect of calcined product, the supported PtIn bimetallic catalyst was achieved by stepwise incipient wetness impregnation method followed by calcination and reduction, and evaluated in isobutane direct dehydrogenation (IDH) to isobutene. The derived ultrathin bimetallic catalyst possesses excellent IDH activity under extreme conditions, in which the isobutane conversion and isobutene selectivity can remain above 63% and 92% respectively, and the turnover frequency is as high as 13.45 s−1. The excellent activity can be attributed to the formation of ultrathin hydrotalcite precursor, which can greatly enhance the specific surface area, interaction among metal components, surface acidity of weak- and medium-acid sites and surface In3+/In0 ratio, and further effectively inhibit carbon deposition and improve dispersion and stability of active Pt species in the corresponding derivative.

Thermally induced structural transitions and temperature memory effect in a luminescent vitrified film of an anisometric europium(III) β-diketonate complex

• Vitrified Eu(DK12-14)3phen film (sandwiched between quartz plates) has been fabricated. • Performed weeklong monitoring revealed temperature memory effect. • Proposed model indicates thermally-induced transitions between two local states of film. • These two states are most likely close to crystalline and amorphous local structures. • Effect could be utilized in designing photonic materials equipped with memory function. We report on a temperature memory effect, which is highly unusual for known film-type materials based on lanthanide(III) β-diketonate complexes. It was observed in a 20 µm thick vitrified film fabricated by cooling the melt of a powder of an anisometric europium(III) β-diketonate complex between two quartz plates. The excitation of the film with light in the wavelength range of 280-425 nm causes a bright orange-red emission of Eu 3+ ions (due to efficient ligand-to-metal energy transfer). The memory effect shows itself as ability of the film to be in different states with their own luminescence decay time at the same temperature. In order to study the effect we carried out a weeklong experiment to monitor the evolution of the luminescence decay time in series of temperature treatments (alternating keeping the film at 370 K and storage in the dark at room temperature). We proposed a simple two-state model to simulate the results of the spectroscopic measurements. This made it possible to reveal the memory effect mechanism, which is thermally induced transitions between two different local states of the film. They are most likely in their nature close to crystalline and amorphous local structures. The obtained and analyzed data clearly indicate that the memory effect observed in the film opens broad perspectives in designing of new type luminescent photonic materials having memory function.

Microstructure, martensitic transformation and shape memory effect of novel Cu–Al-Ga based shape memory single crystals

In this study, the shape memory effect of novel iron-alloyed Cu–Al-Ga shape memory single crystals were reported for the first time. The microstructure, crystal structure, martensitic transformation and shape memory effect of Cu–10Al-6Ga (master alloy), Cu–10Al-6Ga-3Fe, Cu–12Al-4Ga-3Fe and Cu–14Al-4Ga-3Fe (wt.%) were investigated. All studied alloys consist of dominant martensite and fine bcc nanoparticles with richer Fe content and poorer Cu content except master alloy. The martensitic transformation start temperatures are 241.3 °C, 251.3 °C and 71.9 °C for Cu–10Al-6Ga-3Fe, Cu–12Al-4Ga-3Fe and for Cu–14Al-4Ga-3Fe alloys, respectively. For master alloy, the martensitic transformation disappears resulted from the precipitation of a large amount of α-Cu during heating. In addition, the shape memory effects clearly increase as a result of increase of the pre-strains. The Cu–14Al-4Ga-3Fe single crystal obtains a maximum shape memory effect of 6.8% with 100% strain recovery when 10% pre-strain is applied.

Light-induced reversible reorganizations in closed Type II reaction centre complexes: physiological roles and physical mechanisms.

The purpose of this review is to outline our understanding of the nature, mechanism and physiological significance of light-induced reversible reorganizations in closed Type II reaction centre (RC) complexes. In the so-called 'closed' state, purple bacterial RC (bRC) and photosystem II (PSII) RC complexes are incapable of generating additional stable charge separation. Yet, upon continued excitation they display well-discernible changes in their photophysical and photochemical parameters. Substantial stabilization of their charge-separated states has been thoroughly documented-uncovering light-induced reorganizations in closed RCs and revealing their physiological importance in gradually optimizing the operation of the photosynthetic machinery during the dark-to-light transition. A range of subtle light-induced conformational changes has indeed been detected experimentally in different laboratories using different bRC and PSII-containing preparations. In general, the presently available data strongly suggest similar structural dynamics of closed bRC and PSII RC complexes, and similar physical mechanisms, in which dielectric relaxation processes and structural memory effects of proteins are proposed to play important roles.

Facile synthesis of Zn/Cu and PANI modified layered double hydroxides with insights into structural memory effect property

Facile synthesis of Zn/Cu and PANI modified layered double hydroxides with insights into structural memory effect property

A Comprehensive Review of Layered Double Hydroxide-Based Carbon Composites as an Environmental Multifunctional Material for Wastewater Treatment

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials.

Layered double hydroxide (LDH) for multi-functionalized corrosion protection of metals: A review

• A comprehensive review of LDH in corrosion protection was presented. • The synthesizing methods of both LDH powders and films were summarized. • The discussion of the present proposed formation mechanism was shown. • Crucial effects of LDH on corrosion protection were elucidated in details. • Applications of LDH in concrete, coating and biological environments were reviewed. Layered double hydroxide (LDH) has been widely developed in the field of corrosion and protection in recent years based on its unique characteristics including anion capacity, anion exchange ability, structure memory effect, and barrier resistance. This paper comprehensively reviews recent work on the preparations, properties of LDH in the forms of powder and film and their applications in different environments in corrosion and protection. Some novel perspectives are also proposed at the end of the review for future research in corrosion and protection field.

Preface

The Fourth international conference “Shape Memory Alloys” (SMA 2021) continues the tradition of regular scientific events on shape memory alloys held in various cities of the Soviet Union: Kiev (1980, 1991), Voronezh (1982), Tomsk (1985), Novgorod (1989), Kosov (1991), St. Petersburg (1995). These days, the First conference “Shape Memory Alloys: properties, technologies, and prospects” was held in 2014 in Vitebsk (Belarus), the Second one – in 2016 in St. Petersburg, the Third one – in 2018 in Chelyabinsk. The aim of the conference is to review modern research and development directions in the field of shape memory alloys and related phenomena: from studying their structure, physical, mechanical, and functional properties to mathematical modeling of the shape memory materials’ behavior and their applications. The conference schedule comprised oral and poster presentations in the framework of three parallel sections:• Structure, martensitic transformations and shape memory effects in alloys.• The theory of martensitic transformations and shape memory effect: modeling and calculations.• Novel materials. The manufacturing technology and application of shape memory alloys. Editors of Proceedings: Sergey Prokoshkin, Natalia Resnina, Sergey Dubinskiy, Yulia Zhukova, Vadim Sheremetyev, Victor Komarov, Kristina PolyakovaList of Organizers, Program committee, Local Organizing Committee are available in this pdf.

Thermally Induced Structural Transitions and Temperature Memory Effect in a Luminescent Vitrified Film of an Anisometric Europium(Iii) Β-Diketonate Complex

Thermally Induced Structural Transitions and Temperature Memory Effect in a Luminescent Vitrified Film of an Anisometric Europium(Iii) Β-Diketonate Complex

Alloy Ti – 50.2 at.% Ni for Actuators: Evolution of Structure and Shape Memory Effects During Post-Deformation Annealing. Part 2. Influence of Structure and Phase Transformation Special Features on Shape Memory Effects

Alloy Ti – 50.2 at.% Ni for Actuators: Evolution of Structure and Shape Memory Effects During Post-Deformation Annealing. Part 2. Influence of Structure and Phase Transformation Special Features on Shape Memory Effects

Local structure memory effects in the polar and nonpolar phases of MoTe2

We use total scattering to study the reversible transition between the polar $1{T}^{\ensuremath{'}}$ and nonpolar ${T}_{d}$ phases of layered $\mathrm{Mo}{\mathrm{Te}}_{2}$ taking place at 240 K. Whereas, macroscopically, the transition appears to be first order, locally, it is not. In particular, a great deal of the stacking sequence of Te-Mo-Te layers characteristic of the polar $1{T}^{\ensuremath{'}}$ phase persists locally in the nonpolar ${T}_{d}$ phase, and vice versa, over a broad temperature range extending about 100 K both below and above the transition. The intermixing ratio for the two sequences evolves gradually across the transition temperature, consistent with a second-order transition behavior. The presence of coexisting local polar and nonpolar regions and the resulting variety of internal interfaces where the spatial inversion symmetry is broken may be behind some of the unusual electronic properties of ${T}_{d}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{Te}}_{2}$, including its putative type-II Weyl semimetal state.

Structural Memory Effects in Gold-4,4'-Bipyridine-Gold Single-Molecule Nanowires.

We study the vulnerability of single-molecule nanowires against a temporary disconnection of the junction. To this end, we compare the room and low-temperature junction formation trajectories along the opening and closing of gold–4,4′-bipyridine–gold single-molecule nanowires. In the low-temperature measurements, the cross-correlations between the opening and subsequent closing conductance traces demonstrate a strong structural memory effect: around half of the molecular opening traces exhibit similar, statistically dependent molecular features as the junction is closed again. This means that the junction stays rigid and the molecule remains protruding from one electrode even after the rupture of the junction, and therefore, the same single-molecule junction can be reestablished if the electrodes are closed again. In the room-temperature measurements, however, weak opening–closing correlations are found, indicating a significant rearrangement of the junction after the rupture and the related loss of structural memory effects.

Synthesis, Crystallization, Structure Memory Effects, and Molecular Dynamics of Biobased and Renewable Poly(n-alkylene succinate)s with n from 2 to 10

In this article, we synthesize five poly(n-alkylene succinate)s, PnASs, with n = 2, 4, 6, 8, and 10 via multi-step polycondensation methods. Next, we comparatively investigate these renewable and biobased polyesters from the points of view of structure, crystallinity, and molecular mobility, employing 1H nuclear magnetic resonance spectroscopy, size-exclusion chromatography, viscometry, X-ray diffraction, differential scanning calorimetry (DSC, conventional and temperature modulation modes), polarized optical microscopy (POM), and broadband dielectric relaxation spectroscopy (BDS). Next to the successful synthesis of the materials, we evaluate the characteristics of crystallization (temperature and fraction); moreover, we explore for the first time, on the same type of succinic polyesters, the impact of n on the structure memory related to crystal nucleation as well as the changes in the semicrystalline morphology. We demonstrate that the structure/crystal memory is stronger for the lower n (shorter alkylene succinate monomers) because of more chain–chain associations, the result being independent from the overall length of the polymer chain (molar mass, Mn 13–80 kg/mass). The crystalline fraction (CF ∼ 12–34%) increases with n, also independently from Mn; however, the chain length affects directly the nucleation rate as Tc increases with Mn. The direct effects of n, in the inter-/intrachain interactions, as well as the indirect ones, on the CF and distribution of crystallites were found to be responsible for the alternations in the static glass transition temperature in DSC (lowering of Tg with n) and the dynamic glass transition (α, αc relaxations in BDS). For the sum of these PnASs, the molecular dynamics mapping is shown here, also for the first time. With increasing n, segmental dynamics accelerates, whereas, interestingly, the cooperativity drops (elimination for n = 10). Comparing these results with the recorded alternations in the semicrystalline morphology (POM), we conclude spatial confinement to be imposed on the mobile amorphous polymer by the tightly distributed crystallites when n increases. Overall, these data provide proofs for the potential for tuning of the final polymer properties connected with crystallization (mechanical performance and permeability), envisaging future biomedical, packaging, and other application for these PnASs.

Synthesis and characterization of hydrocalumite for removal of fluoride from aqueous solutions.

Fluoride can cause some diseases to humans when ingested in large quantities and for a long time. Due to this, it is necessary to remove or reduce the amount of fluoride in effluents before release into the water bodies. This work aimed to evaluate the ability of hydrocalumites synthesized by two different methodologies and calcined hydrocalumite in reducing the content of fluoride in aqueous solutions. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 physisorption, thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The removal capacity of fluoride ions ranged from 14.9 to 189.6mgF- g-1. The removal mechanisms by hydrocalumites were ion exchange and adsorption at low concentrations, while at high concentrations were adsorption and precipitation of calcium fluoride. In relation to the use of calcined hydrocalumite, the removal mechanisms were ion exchange and reconstruction of structure (memory effect) in low concentrations. By the adsorption tests, it was observed that the results fit better the Langmuir isotherm model.

Hybrid stochastic fractional-based approach to modeling bacterial quorum sensing

Bacterial communication is a complex process, which can be formalized by a deterministic approach and then explored by means of methods of mathematical modeling and computer simulation. To describe bacterial cooperative behavior in the special case of quorum sensing we propose a new mathematical model based on a hybrid stochastic fractional concept that is found examining self-similar dynamic processes of bacterial nucleation and growth. The mathematical model is specified as an initial-boundary value problem for a system of fractional order partial differential equations. We derive a numerical algorithm based on the combination of an implicit finite difference scheme for solving fractional partial differential equations and Monte-Carlo simulation of bacterial dynamics. The computational experiments are performed to simulate reaction-diffusion processes in biological systems related to the self-similar behavior of heterogeneous structure and time memory effect.