Crystalline Structure Research Articles

Effects of various pyrolysis temperatures on the physicochemical characteristics of crop straw-derived biochars and their application in tar reforming

As a by-product of the rapid pyrolysis of biomass, biochar not only plays an important role in the biomass conversion process but also holds significant potential value in the catalytic conversion field. This study aimed to evaluate the physicochemical properties changes of biochars at different pyrolysis temperatures and their potential application in tar reforming. Biochars derived from three feedstocks of maize straw (MS), rice husk (RH), and cotton straw (CS) were achieved by fast pyrolysis within a broad temperature range of 300~900 °C, respectively. The results showed that the pyrolysis temperature exerted a pronounced influence on the structural characteristics of biochar. With increasing temperature, the H/C and O/C ratios progressively decreased, accompanied by a significant reduction in oxygen-containing structures. In addition, elevated pyrolysis temperatures contributed favorably to the formation of the crystalline structure of biochar. Raman analysis unveiled a correlation between the fused aromatic ring system and H/C ratios, validating the aromatization progress of biochar. In the tar catalytic reforming process, the three representative biochars, under the effect of MS-600 (standing for MS biochar derived at 600 °C), RH-600, and CS-600 catalysts, exhibited outstanding catalytic performance with tar conversion efficiencies of 73.26%, 68.51%, and 71.43%, respectively. This study provided systematic support for the high-value use of biochar from crop straw.

The effects of adding various starches on the structures of restructured potato-based dough and the oil uptake of potato chips.

The material composition significantly influences the oil absorption and quality characteristics of fried food products. The oil absorption of restructured potato chips is highly dependent on the structural properties of the restructured potato-based dough produced prior to frying. In this study, three types of starch were added to modify the structure of the restructured potato-based dough, allowing the production of potato chips with less oil absorption. Distinct differences were observed among the three types of starch in terms of amylose content, chain length distribution, swelling power, solubility, crystalline structure, and pasting properties. The addition of wheat starch, corn starch, and tapioca starch changed the rheological properties, water distribution, and the strength of the restructured dough. Importantly, adding wheat starch and corn starch significantly lowered the oil content of potato chips by 7.94% and 13.06%, respectively. The reduction in oil absorption by potato chips was attributed to the increased strength of the starchy gel network of the dough, a slower rate of water evaporation, and a limitation of dough expansion during frying. Adding wheat starch or corn starch to the restructured potato-based dough resulted in a decrease in the oil absorption of potato chips by creating a stronger starchy gel network in the dough. This study could guide the development of suitable material compositions, which are important for producing fried food products with lower oil content. This article is protected by copyright. All rights reserved.

Extrusion and chlorogenic acid treatment increase the ordered structure and resistant starch levels in rice starch with amelioration of gut lipid metabolism in obese rats.

Dietary interventions are receiving increasing attention for maintaining host health and diminishing disease risk. This study endeavored to elucidate the intervention effect of chlorogenic acid coupled with extruded rice starch (CGA-ES) in mitigating lipid metabolism disorders induced by a high-fat diet (HFD) in rats. First, a significant increase in resistant starch (RS) and a decrease in the predicted glycemic index (pGI) were observed in CGA-ES owing to the formation of an ordered structure (Dm, single helix, and V-type crystalline structure) and partly released CGA. Compared to a physical mixture of starch and chlorogenic acid (CGA + S), CGA-ES showed a more potent effect in alleviating lipid metabolism disorders, manifesting as reduced levels of blood glucose, serum total cholesterol (TC), triglycerides (TG), aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (AKP), as well as body weight. It is correlated with an improvement in the gut microecology, featuring bacteria known for cholesterol reduction and butyrate production (Butyricicoccus, Bifidobacterium, Fusicatenibacter, Turicibacter, and Enterorhabdus), along with bile acid, butyrate and PG (PG (17:0/16:0) and PG (18:1/16:0)). The RS fraction of CGA-ES was found to be the main contributor. These findings would provide evidence for future studies to regulate lipid metabolism disorders, and even obesity using CGA-ES.

Enhanced DSSC efficiency through integration of red-emitting MgAl2O4: Eu3+ phosphor within TiO2 layer

The main objective of this paper was to enhance the absorption and charge carrier generation rates of DSSC. The functional property of the Eu3+ ion (red light) when infused with the MgAl2O4 host was combined with TiO2 nanoparticles and the results obtained through various studies are elaborated. The host and the nanoparticles were prepared through solid-state and sol-gel routes, respectively, with their crystalline structure and surface morphology identified by X-ray diffraction and field emission scanning electron microscope. The optical characteristics of the sample were studied through photoluminescence (PL) excitation (394 nm) and PL emission spectral analysis. The MgAl2O4: Eu3+ phosphor utilized in DSSC for the light down-conversion process converts high-energy incident light into low-radiation light, which further excites the N719 dye to emit charge carriers, thus increasing the conversion efficiency of the dye-sensitized solar cells. The overall conversion efficiency was observed a 4.80 % when 0.9 MW % Eu3+: MgAl2O4 was added to the TiO2 nanoparticle with an enhanced DSSC performance.

Characteristics of in-situ automated fiber placement carbon-fiber-reinforced low-melt polyaryl ether ketone laminates part 1: Manufacturing influences

This study presents an investigation into mechanical and thermal properties, as well as the microstructure of Automated Fiber Placement-manufactured laminates using a novel carbon fiber-reinforced low-melt polyaryl ether ketone polymer material. The material’s lower melting temperature and lower melt viscosity as compared to established high-temperature thermoplastic materials as PEEK, promises favourable characteristics for the Automated Fiber Placement process. This work aims at in-situ consolidation and the influence of a heated tooling and a post process tempering step, which both turned out to be promising in previous investigations. Laminates were manufactured using a cold tooling, a heated tooling configuration, a cold tooling with a subsequent tempering process step and a hot-pressed reference laminate. Differential Scanning Calorimetry showed that crystallinity values more than doubled for the heated tooling and post process tempering configurations, compared to the cold tooling, reaching 24% and 30%, respectively. Mechanical strength values showed an increase in interlaminar shear strength and compression strength but did not increase to the same extent as was expected from the increase in crystallinity. With Scanning Electron Microscopy differences in the microscopic structure of the polymer matrix could be detected. While the post process tempering step leads to a mostly lamellar crystalline structure, the heated tooling configuration and the post process hot pressing induce a predominance of crystalline spherulites, which might positively affect the mechanical performance. Computed Tomography scans revealed a high amount of porosity in the in-situ-manufactured samples and unprocessed tape material, which likely mitigated the positive effect of increased crystallinity.

Effects of carbonization temperature and time on the characteristics of carbonized sludge

Abstract To investigate the influence of carbonization process parameters on the characteristics of municipal sludge carbonization products, this study selected carbonization temperatures of 300–700 °C and carbonization times of 0.5–1.5 h to carbonize municipal sludge. The results showed that with an increase in temperature and carbonization time, the sludge was carbonized more completely, and the structure and performance characteristics of the sludge changed significantly. Organic matter was continuously cracked, the amorphous nature of the material was reduced, its morphology was transformed into an increasing number of regular crystalline structures, and the content of carbon continued to decrease, from the initial 52.85 to 38.77%, while the content of inorganic species consisting continued to increase. The conductivity was reduced by 87.8%, and the degree of conversion of salt ions into their residual and insoluble states was significant. Natural water absorption in the sludge decreased from 8.13 to 1.29%, and hydrophobicity increased. The dry-basis higher calorific value decreased from 8,703 to 3,574 kJ/kg. Heavy metals were concentrated by a factor of 2–3, but the content of the available state was very low. The results of this study provide important technological support for the selection of suitable carbonization process conditions and for resource utilization.

Structural investigation, molecular docking, X‐ray studies, and in vitro biological activities of new transition metal complexes based isoleucine‐pyridyl hybrid Schiff base

One significant class of chemotherapeutic medicines with the ability to overcome drug resistance is metal‐based medications. The creation of novel therapeutic medications with distinct modes of action is required due to the rise in drug resistance, treatment failures, and the scarcity of available treatments. The amino acid isoleucine interacts with the arylidene (synthesized from isatin and 2,6‐diamino‐pyridine) forming the HL Schiff base ligand, which then interacts with some transition metal ions to form the metal complexes. Thermal analysis, spectroscopy (1H‐NMR, IR, mass, and ultraviolet–visible), solid reflectance, magnetic moment, molar conductivity, and elemental analyses were employed for examining the synthesized HL and resultant complexes. Mass spectra besides elemental analyses studies verified the formulae of the Schiff base ligand and metal complexes. All the complexes, except for the Fe(III) complex which is non‐electrolyte, exhibited electrolytic behavior as indicated by their molar conductivity values. The obtained complexes exhibited octahedral geometrical shapes, except for the complexes of Co(II), Ni(II), and Zn(II), which displayed tetrahedral geometry. Thermal analysis showed that the complexes consistently release organic ligands and anionic components following the initial loss of water molecules of hydration. The conducted X‐ray diffraction patterns elucidated their lattice dynamics and not only confirmed the purity of the samples, but also demonstrated that the ligand and complexes of Cr(III), Fe(III), Mn(II), Cu(II), Zn(II), and Cd(II) have a crystalline structure in addition to determination of average size of the crystallites. Scanning electron microscope (SEM) was investigated for Schiff base ligand and Co(II) complex. The complexes demonstrated superior efficacy than HL towards fungal and bacteria organisms against Aspergillus fumigatus and Candida albicans, Salmonella Sp., Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. The MCF‐7 cancer cell was subjected to investigation by synthesized complexes and IC50 values ranged from 12 to 23.1 μg/ml. Molecular docking studies define and anticipate the inhibitory potential and binding mode of the generated ligand with the 1GS4, 2HQ6, 3DJD, and 5JPE receptors.

Green synthesis of silver deposited on copper ferrite nanoparticles for the photodegradation of dye and antibiotics

Wastewater remediation is a prominent concern that should be addressed, as it is a critical problem that damages natural resources and has a negative impact on living organisms. In this study, the synthesis of copper ferrite and silver doped-copper ferrite nanoparticles named CuFe2O4 and AgXCuFe2O4 using Monsonia burkeana (M. burkeana) as a fuel and their photocatalytic performance against the textile pollutant, Methylene blue (MB) and the pharmaceutical pollutant, sulfisoxazole (SSX) was reported. The physical, optical, spectroscopic, and surface analyses of the as-prepared nanoparticles were characterized using various techniques. XRD confirmed the crystalline structure of Ag-CuFe2O4 and the incorporation of silver on the surface of the nanoferrites. FTIR analysis indicated the formation of a single-phase spinel crystalline structure with two sub-lattices (Td and Oh). UV–Vis absorption spectra of silver-substituted copper ferrite revealed that the band gap energy (Eg) decreased with increasing crystallite size. Upon testing their degradation efficiency, at pH 12, the highest degradation of 99 % after 60 min for the 7 % AgCuFe2O4 was reported, and the rate of the reaction was found to be 0.09769 min−1. The 7 % Ag-CuFe2O4 catalyst could be reused more than 4 times with a minimal loss in photostability and the e− and •O2- were the primary species responsible for MB degradation. The photocatalyst 7 %Ag-CuFe2O4, showed a 60 % decomposition for the antibiotic after 120 min of UV-radiation. The 7 % Ag-CuFe2O4 photocatalyst displayed superior magnetic recovery capability under the action of the external magnetic field. These developments in this study offer wide promising applications in water environmental remediation.

Effect of nucleating agents on crystalline silicon textured structure: From upright pyramid to analogous inverted pyramid

For further improving the efficiency of solar cells, it is one of the mainstream approaches to obtain a novel textured surface structure with lower reflectivity, without affecting the existing industry processes. However, the current rapid texturing methods used in the industry can only achieve an upright pyramid structure. This study first analyzed how the rapid texturing process is achieved through texturing additives. Subsequently, based on this principle, we investigated the core component of the texturing additives—nucleating agent—and examined how its concentration influences the surface structure, leading to the development of an analogous inverted pyramid structure with advantageous reflectivity. To remove the damage layer generated at the top edges of the analogous inverted pyramid due to insufficient etching, a two-step texturing process was proposed. This process aims to protect the structure while effectively removing the damage layer. Ultimately, we applied the two-step texturing process to fabricate heterojunction solar cells with the analogous inverted pyramid textured surface, achieving an efficiency of 25.43 %, which is 0.19 % higher than conventional upright pyramid structure cells.

First-principle investigation of lead-free double perovskites Cs2MScCl6 (M = Na, K) for optoelectronic and thermoelectric applications

Double perovskite optoelectronic devices are gaining popularity due to their advantageous features, such as an efficient and easy-to-manage crystalline structure. In this study, we looked into the optoelectronic, mechanical, and thermoelectric attributes of Cs2MScCl6 (with M being Na or K) using density functional theory. The obtained results show that both compounds can exist stably in cubic double perovskite structure, space group Fm3¯m . The electronic band structures of Cs2NaScCl6 and Cs2KScCl6 demonstrate a direct semiconducting band gap of 3.829 eV and 3.996 eV, respectively. As the pressure rises up to 200 GPa, Cs2KScCl6 reveals extraordinary tunability along with an indirect band gap of 2.000 eV. Moreover, optical analysis—comprising dielectric constant calculations, absorption coefficient measurements, refractive indices checks, reflectivity assessments, energy loss estimations, and electrical conductivity appraisals—shows promising results too. Specifically, the absorption coefficient and conductivity predominantly fall within the ultraviolet range under normal atmospheric pressure. The thermoelectric characteristics suggest a noteworthy Seebeck coefficient, low thermal conductance and good figure of merit implying it could be used in the domain of sustainable energy.

Modulation of Phase Separation Morphology by Configuration Engineering in Bulk Heterojunction Organic Solar Cells

For bulk‐heterojunction organic solar cells (OSCs), molecular structure design to control molecular stacking is crucial to obtain ideally phase‐separated morphology and high device performance. Herein, the investigation focuses on two polythiophene‐quinoxaline (PTQ) derivatives (PTQ8 and PTQ10) blended with Y6, utilizing coarse‐grained molecular dynamics simulations based on the Lennard–Jones static potential (LJSP) method. The study reveals that the diminished photovoltaic efficiencies of PTQ8:Y6 blends, compared to PTQ10:Y6 blends, are not solely attributed to reduced driving forces. The introduction of fluorine‐substituted sites in the thiophene group of PTQ polymer is identified as a significant factor. This alteration causes PTQ polymers in PTQ8:Y6 blends to coil, compromising the crystalline structure. PTQ8's bifluorine group induces a repulsive effect on the quinoxaline group, leading to a coiled‐chain structure that hinders chain stacking. Conversely, PTQ10 exhibits a straighter chain conformation. Additionally, PTQ8's high solubility in chloroform prevents effective aggregation, further impeding suitable morphology formation. Coarse‐grained simulations employing LJSP prove effective in precisely exploring the morphology of OSCs, offering crucial insights for materials in this field.

Manipulating the diffusion energy barrier at the lithium metal electrolyte interface for dendrite-free long-life batteries.

Constructing an artificial solid electrolyte interphase (SEI) on lithium metal electrodes is a promising approach to address the rampant growth of dangerous lithium morphologies (dendritic and dead Li0) and low Coulombic efficiency that plague development of lithium metal batteries, but how Li+ transport behavior in the SEI is coupled with mechanical properties remains unknown. We demonstrate here a facile and scalable solution-processed approach to form a Li3N-rich SEI with a phase-pure crystalline structure that minimizes the diffusion energy barrier of Li+ across the SEI. Compared with a polycrystalline Li3N SEI obtained from conventional practice, the phase-pure/single crystalline Li3N-rich SEI constitutes an interphase of high mechanical strength and low Li+ diffusion barrier. We elucidate the correlation among Li+ transference number, diffusion behavior, concentration gradient, and the stability of the lithium metal electrode by integrating phase field simulations with experiments. We demonstrate improved reversibility and charge/discharge cycling behaviors for both symmetric cells and full lithium-metal batteries constructed with this Li3N-rich SEI. These studies may cast new insight into the design and engineering of an ideal artificial SEI for stable and high-performance lithium metal batteries.

Efficient and environmentally friendly separation and recycling of cathode materials and current collectors for lithium-ion batteries by fast Joule heating

Spent Li-ion batteries(LIBs) cathodes possess high recycling value. To improve subsequent recovery efficiency and product purity, separating the cathode materials from the aluminum foil is critical. However, traditional separation methods are characterized by high energy consumption, low recycling efficiency, and environmental pollution. This research presents a novel method that involves injecting Joule heat directly into the aluminum foil in the air, resulting in the melting and slight thermal decomposition of the PVDF binder, which reduces its adhesive properties. Owing to the difference in thermal expansion coefficients between the binder and aluminum foil, an instantaneous thermal stress was generated at the interface of the cathode materials and aluminum foil, resulting in a peeling force. This method enabled a rapid and efficient separation of lithium iron phosphate (LFP) and ternary Li-ion (NCM) battery cathode materials. The optimal separation conditions, separation mechanism, and properties of the recovered products were investigated thoroughly using high-speed camera imaging, temperature rise calculations, and microscopic characterization. This chemical-free method avoids the generation of wastewater and gas emissions. Under optimal experimental parameters, the separation efficiency and purity of cathode material reached 99 % and 99.7 %, respectively. Additionally, this method preserves both the structural integrity of the aluminum foil and the crystalline structure of the cathode materials, offering a new pathway for sustainable recycling of end-of-life LIBs.

Constructing molecular junction in covalent organic frameworks for efficient uranium(VI) photoreduction

Constructing heterojunction photocatalysts is widely regarded as an effective strategy to improve photocatalytic reduction efficiency of U(VI) to U(IV). However, the traditional heterojunctions fabricated by the multiphase hybridization generally present inhomogeneous junction distribution and low connectivity, which is not beneficial for the migration of photogenerated charges. Here, Cu-N cluster as oxidative site and Ti-O cluster as reductive site are covalently coupled to fabricate Cu3-Ti6-COF molecular junction. Importantly, the resulting Cu3-Ti6-COF not only possesses high connectivity but also exhibits well-defined crystalline structure and monophasic periodic distribution, thus effectively boosting the directed transport and separation of charge carriers. As a result, the excellent photocatalytic performance is achieved with the U(VI) removal efficiency of up to 94.8 % without any sacrificial reagents. As far as our knowledge, this is the first work about constructing COF molecular junction for photoreduction U(VI), which may simulate the exploration of novel COFs photocatalysts toward photoinduced radionuclide removal.

Polyurea/Aminopropyl Isobutyl Polyhedral Oligomeric Silsesquioxane-Functionalized Graphene Nanoplatelet Nanocomposites for Force Protection Applications.

Herein, the development of new nanocomposite systems is reported based on one-part polyurea (PU) and aminopropyl isobutyl polyhedral oligomeric silsesquioxane (POSS)-functionalized graphene nanoplatelets (GNP-POSS) as compatible nanoreinforcements with the PU resin. GNP-POSS was effectively synthesized via a two-step synthesis protocol, including ultrasonication-assisted reaction and precipitation, and carefully characterized with respect to its chemical and crystalline structure, morphology, and thermal stability. FTIR and XPS spectroscopy analyses revealed that POSS interacts with the residual oxygen moieties of the GNPs through both covalent and noncovalent bonding. The X-ray diffraction pattern of GNP-POSS further revealed that the crystallinity of the GNPs was not altered after their functionalization with POSS. GNP-POSS was successfully incorporated in PU at contents of 1, 3, 5, and 10 wt % to yield PU/GNP-POSS nanocomposite films. An ATR-FTIR analysis of these films confirmed the presence of strong interfacial interactions between the urea groups of PU and the GNP-POSS functionalities. Moreover, the PU/GNP-POSS nanocomposite films exhibited enhanced thermal stability and mechanical properties compared to those of the neat PU film. The quasi-static tensile testing of the PU/GNP-POSS samples revealed remarkable enhancements in the tensile strength (from 7.9 for the neat PU to 25.1 MPa for PU/GNP-POSS) and Young's modulus (238-617 MPa), while elongation at break and toughness also showed 14 and 125% improvements, respectively. Finally, the effects of GNP-POSS content on the morphological, quasistatic tensile, and high-strain-rate dynamic behavior of the PU/GNP-POSS nanocomposite films were also investigated. Overall, the tests performed using a split-Hopkinson pressure bar setup revealed a large increase in the film strength (from 147.6 for the neat PU film to 199 MPa for the PU/GNP-POSS film) and a marginal increase in the energy density of the film (38.1-40.8 kJ/m3). These findings support the suitability of the PU/GNP-POSS nanocomposite films for force protection applications.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

Dipole moment regulation for enhancing internal electric field in covalent organic frameworks photocatalysts

Covalent organic frameworks (COFs) have recently emerged as a kind of promising photocatalytic platform in addressing the growing threat of trace pollutants in aquatic environments. Along this, we propose a strategy of constructing internal electric field (IEF) in COFs through the dipole moment regulation, which intrinsically facilitates the separation and transfer of photogenerated excitons. Two COFs of BTT-TZ-COF and BTT-TB-COF are developed by linking the electron-donor of benzotrithiophene (BTT) block and the electron-acceptor of triazine (TZ) or tribenzene (TB) block, respectively. DFT calculations demonstrate TZ block with larger dipole moment can achieve more efficient IEF due to the stronger electron-attractive force and hence narrower bandgap. Moreover, featuring the highly-order crystalline structure for accelerating photo-excitons transfer and rich porosity for facilitating the adsorption, BTT-TZ-COF exhibited an excellent universal performance of photocatalytic degradations of various dyes. Specifically, a superior photodegradation efficiency of 99% Rhodamine B (RhB) is achieved within 20 min under the simulated sunlight. Therefore, this convenient construction approach of enhanced IEF in COFs through rational regulation of the dipole moment can be a promising way to realize high photocatalytic activity.

Processing of Thin Films Based on Cellulose Nanocrystals and Biodegradable Polymers by Space-Confined Solvent Vapor Annealing and Morphological Characteristics.

L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate-co-hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers with cellulose nanocrystal fillers and further processing the resulting materials via space-confined solvent vapor annealing. Cellulose was previously obtained from renewable biomass and further converted to cellulose nanocrystals by hydrolysis with the lactic acid. The solutions of biodegradable polymers were spin-coated onto solid substrates before and after the addition of cellulose nanocrystals. The obtained thin film composites were further processed via space-confined solvent vapor annealing to eventually favor their crystallization and, thus, to alter the final microstructure. Indeed, atomic force microscopy studies have revealed that the presence of cellulose nanocrystals within a biodegradable polymer matrix promoted the formation of large crystalline structures exhibiting fractal-, spherulitic- or needle-like morphologies.

Highly Efficient and Reproducible Sonochemical Synthesis of ZnO Nanocrystals.

Sonochemical synthesis can be a facile, fast, efficient, versatile and economical way to prepare a large variety of conventional or novel nanostructured materials (metallic, magnetic, semiconducting, polymeric, etc.). In this work, zinc oxide nanocrystals were synthesized by irradiating and heating at 90 °C in a commercial ultrasonic bath a water solution of zinc nitrate hexahydrate and ammonia solution or hexamethylenetetramine as base catalysts. The evolution of the powder morphology and its crystalline structure were investigated at different times of ultrasonic irradiation (0-9 hours) and compared with those of samples obtained by only heating the solutions in a muffle furnace in order to enlighten the growth mechanism. It resulted that: i) the crystal morphology depends on the selected base, ii) for samples obtained by using ultrasounds, the homogeneity of the powders depends on the irradiation time, iii) by comparing all samples obtained at 7 hours of heating, the aspect ratio of the crystals is higher for those that also underwent to ultrasounds.

Characterization of the optical gain at 1550 nm of erbium-oxalate single crystals

Erbium is well-recognized as a key element for optical amplification at the 1550 nm operation band. However, the limited solubility of this material in vitreous matrices sets a critical constraint to the achievable optical gain, which limits its applicability in photonic integrated platforms. One of the solutions to increase the concentration of erbium is to employ a crystalline structure instead of a glass. In this paper, we characterize samples of erbium and erbium-ytterbium oxalate single crystals synthesized using the gel diffusion method. X-ray diffraction spectra and thermogravimetric analyses reveal that the synthesis method indeed generated the expected compound, and the pump-and-probe experiments demonstrate an on-off gain coefficient of ≈ 6.5 dB/mm, making this material a high-potential candidate for the implementation of integrated optical amplifiers.