Increasing Synthesis Temperature Research Articles

The Influence of Temperature and Stoichiometry on the Optical Properties of CdSe Nanoplatelets

Colloidal quasi-two-dimensional cadmium chalcogenide nanoplatelets have attracted considerable interest due to their narrow excitonic emission and absorption bands, making them promising candidates for advanced optical applications. In this study, the synthesis of quasi-two-dimensional CdSe NPLs with a thickness of 3.5 monolayers was investigated to understand the effects of synthesis temperature on their stoichiometry, morphology, and optical properties. The NPLs were synthesized using a colloidal method with temperatures ranging from 170 °C to 210 °C and optimized precursor ratios. Total reflection X-ray fluorescence (TXRF) analysis was employed to determine stoichiometry, while high-resolution transmission electron microscopy (HRTEM) and UV-Vis spectroscopy and photoluminescence spectroscopy were used to analyze the structural and optical characteristics. The results showed a strong correlation between increasing synthesis temperature and the enlargement of nanoscroll diameters, indicating dynamic growth. The best results in terms of uniformity, stoichiometry, and optical properties were achieved at a growth temperature of 200 °C. At this temperature, no additional optical bands associated with secondary populations or hetero-confinement were observed, indicating the high purity of the sample. Samples synthesized at lower temperatures exhibited deviations in stoichiometry and optical performance, suggesting the presence of residual organic compounds.

Changes of magnetic configurations in MnCo2O4 caused by synthesis temperature

The synthesis temperature of the sample is a key parameter that not only affects the occupancy of cations, but also has a significant impact on the magnetic configuration. In this study, we synthesized pure phase MnCo2O4 powder using a solid-phase reaction method and studied the change of its magnetic configuration with synthesis temperature. Due to the Jahn-Teller distortion caused by octahedral Co2+ and Mn3+ ions, magnetic interactions between octahedral cations dominate in all the samples. When the synthesis temperature is low, some octahedral Co3+ is reduced to Co2+. The appearance of antiferromagnetic interaction between octahedral Co2+ makes the antiferromagnetic characteristics in the sample more prominent. The magnetic configuration in the MnCo2O4 powders synthesized at low temperature undergoes a transition from collinear to non-collinear as the test temperature decreases. As the synthesis temperature increases, a stable collinear magnetic structure is formed, and the ferromagnetic phase gradually becomes dominant. The defined saturation magnetization reaches its maximum at a synthesis temperature of 700°C, with the Neel temperature of the sample close to the ideal value.

Inverted Red Quantum Dot Light-Emitting Diodes with ZnO Nanoparticles Synthesized Using Zinc Acetate Dihydrate and Potassium Hydroxide in Open and Closed Systems

We developed inverted red quantum dot light-emitting diodes (QLEDs) with ZnO nanoparticles synthesized in open and closed systems. Wurtzite-structured ZnO nanoparticles were synthesized using potassium hydroxide and zinc acetate dihydrate at various temperatures in the open and closed systems. The particle size increases with increasing synthesis temperature. The ZnO nanoparticles synthesized at 50, 60, and 70 °C in the closed system have an average particle size of 3.2, 4.0, and 5.4 nm, respectively. The particle size is larger in the open system compared to the closed system as the methanol solvent evaporates during the synthesis process. The surface defect-induced emission in ZnO nanoparticles shifts to a longer wavelength and the emission intensity decreases as the synthesis temperature increases. The inverted red QLEDs were fabricated with a synthesized ZnO nanoparticle electron transport layer. The driving voltage of the inverted QLEDs decreases as the synthesis temperature increases. The current efficiency is higher in the inverted red QLEDs with the ZnO nanoparticles synthesized in the closed system compared to the devices with the nanoparticles synthesized in the open system. The device with the ZnO nanoparticles synthesized at 60 °C in the closed system exhibits the maximum current efficiency of 5.8 cd/A.

EFFECTS OF SYNTHESIS TEMPERATURE ON THE STRUCTURAL AND OPTICAL PROPERTIES OF CaAl2O4: Eu2+, Dy3+NANOPARTICLES

Calcium aluminate phosphor nanomaterials co-doped with europium and dysprosium (CaAl2O4: Eu2+, Dy3+) were prepared using a facile solution combustion technique. The structural and optical properties were investigated. The X-ray diffraction (XRD) results confirmed the presence of the monoclinic phase in all the samples, with few impurity phases in the samples synthesized at 300°C and 400°C. The Fourier-transform infrared analysis gave the expected chemical combustion results of the final product with few traces of Ca3Al2O6 impurities at low and very high synthesis temperatures. The XRD patterns displayed diffraction angles of the major peaks shifting to higher 2 theta as the synthesis temperature increased. This is attributed to an increase in particle sizes, which led to an increase in lattice parameters. The intensity of the prominent peak increased up to 500°C due to improved crystal quality. The crystallite sizes of the as-prepared samples were determined using the Debye-Scherrer equation. It was noted that there is variation in the crystallite sizes with synthesis temperature. The UV-Vis graph shows that absorption edges also shifted to lower wavelengths with an increase in synthesis temperature. It was noted that the band gap increased with an increase in synthesis temperature up to 500°C, but at temperature of 1000°C, the band gap was observed todecrease. Scanning electron microscope micrographs showed that the samples had irregular shapes with pores and cracks. The study provides a simple route to synthesize CaAl2O4: Eu2+, Dy3+ phosphors with optimum synthesis temperature, producing the most crystalline sample for use in lighting devices.

Effect of Synthesis Conditions on the Composition, Local Structure and Electrochemical Behavior of (Cr,Fe,Mn,Co,Ni)3O4 Anode Material

AbstractDisordered high entropy spinels (HES) (Cr,Fe,Mn,Co,Ni)3O4 were obtained by solid‐state synthesis and co‐precipitation using various powder precursors. They were characterized by a complex of physico‐chemical methods and investigated as anode materials for lithium‐ion batteries (LIBs). According to XRD and TEM data, the materials are single‐phase. The structural characterization of the samples obtained at 773, 973, and 1273 K was determined using Raman and Mössbauer spectroscopy, and magnetic measurements. The degree of spinel inversion and lattice distortion (microstrains) decrease with increasing synthesis temperature, while the crystallite size increases. The insufficient nickel content in the samples ensures a more uniform distribution of iron cations in both sublattices, which leads to an increase in the lattice parameters and has a positive effect on the de‐/lithiation. Repeated ball‐milling of HES material, prepared by co‐precipitation, increases its specific capacity from 284 mAh g−1 to 492 mAh g−1 at a current density of 100 mA g−1 after 25 cycles. Besides, the smaller crystallite size reduces the volume changes in the materials during de‐/lithiation.

Preparation and properties of Ta fiber reinforced high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC composite ceramics

High-entropy boride ceramics are expected to be widely used in aerospace, automotive turbines, and armor protection due to their advantages of high melting point, high hardness, adjustable performance, high-temperature stability, and good oxidation resistance. However, it is urgent to solve the problem of low fracture toughness before application. Therefore, in this paper, a single-phase high-purity (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 powder was prepared by boron/carbon thermal reduction method using a vacuum furnace. The effects of synthesis temperature and C content on the powder were studied. Secondly, HEB ((Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2) powder, SiC powder, and chopped Ta fiber were mixed uniformly, and Ta fiber toughened HEB-SiC composite ceramics were prepared by spark plasma sintering (SPS). The effects of Ta fiber content on the phase composition, microstructure, mechanical properties, and oxidation resistance of the composite ceramics were investigated. The results show that with the increase in synthesis temperature, the HEB powder gradually dissolves, and the solid solution is completely formed at 1700 °C. As the C content increases, the oxygen content and particle size of the powder gradually decrease. Single-phase high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 powders with high purity were prepared at 1700 °C for 1 h with 6 wt% C content. The addition of C will promote the boron/carbon thermal reduction method, reduce the oxygen content, and inhibit grain growth. With the increase of Ta fiber content, the density of HEB-SiC-Taf composite ceramics increased first and then decreased. The hardness gradually decreased, and the fracture toughness gradually increased. When the Ta fiber content was 7 vol%, the fracture toughness was the highest, reaching 5.12 ± 0.39MPa⋅m1/2, which was nearly 45 % higher than that of the composite ceramics without Ta fiber. This is because of the synergistic toughening mechanism of metal toughening and fiber toughening, such as crack deflection, crack bridging, fiber debonding, and fiber pullout, which improves the fracture toughness of the composite ceramics. With the increase in oxidation temperature, B2O3, SiO2, Ta2O5, and various metal oxides appear on the surface of HEB-SiC-Taf composite ceramics. The oxidation depth and weight gain per unit area gradually increase. When the Ta fiber content is 5 vol%, the composite ceramics exhibit the best high temperature stability and oxidation resistance. This is due to the Ta2O5 formed by the oxidation of Ta fibers, which dissolves into the B2O3 glass phase, increasing viscosity and improving high temperature stability while reducing the oxygen diffusion rate.

Controlling the structure of nitrogen-doped zeolite-templated carbon for CO2 capture based on the synthesis conditions

The surface chemistry and the textural properties of nitrogen-doped zeolite-templated carbon materials (N-ZTC) are decisive for their functionality in CO2 capture. This study analyses how the synthesis conditions affect the structure, formation of N-containing functional groups, thermal stability and CO2 capture of N-ZTC in comparison with nitrogen-free ZTC. Faujasite as a hard template and chemical vapour depositions (CVD) with propene and acetonitrile were used for the synthesis of ZTC and N-ZTC, respectively. XRD, SEM, N2 and CO2 sorption, XPS and TG/DSC analyses showed that the structural ordering and microporous volume in N-ZTC increases with increasing synthesis temperature. Conversely, at higher temperatures, the content of basic pyridinic groups in N-ZTC decreases in favour of stable graphitic nitrogen. The Lewis acid−base interaction of CO2 with the pyridinic groups provides the highest adsorption heats, the highest affinity for CO2 compared to N2 and enhances CO2/N2 selectivity (CO2/N2 selectivities of 127, 95, 89, and 66 for N-ZTC750°C, N-ZTC800°C, N-ZTC850°C and ZTC, respectively). The maximum adsorption capacity was achieved for N-ZTC800°C still yielding a high content of basic groups and a larger micropore volume compared to N-ZTC750°C. The decisive factor for the selectivity is thus the presence of basic centers attainable in N-ZTC at a lower synthesis temperature. The maximum adsorption capacity is associated with a large microporous volume and basic centers in N-ZTC synthesized at medium temperatures. The energy of CO2 adsorption by Lewis acid−base interactions and well-developed micropores are decisive for high selectivity and large adsorption capacity for efficient CO2 capture using N-ZTC materials.

Fabrication and performance investigation of high entropy perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 IT-SOFC cathode material

The high-entropy oxide (HEO) concept expands the design space of solid oxide fuel cell (SOFC) cathode materials. There is great potential for the development of HEO cathode materials that has not been fully explored, and the relationship between their chemical composition, grain size, and electrochemical performance is not yet fully understood. This experimental design involved the preparation of single-phase perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 HEO SOFC cathode materials, and we systematically studied the effects of synthesis temperature and microstructure on their electrochemical performance. The results show that as the synthesis temperature increases, structural transformations from multiphase to single-phase perovskite HEO can be observed. It exhibits excellent conductivity and electrochemical performance (the minimum polarization resistance reaches 0.033 Ω∙cm2, and the maximum power density is 664 mW∙cm−2). The single-phase perovskite HEO sample exhibits higher electrochemical performances compared to those of multiphase perovskite. Furthermore, it exhibits outstanding ability to suppress Sr segregation, chemical compatibility with Ce0.8Sm0.2O1.9(SDC), and CO2 tolerance performance. The Distribution of relaxation time(DRT) analysis shows that as the synthesis temperature (1000–1150 ℃) increase, HEO single-phase formed and the oxygen atom reduction ability of the SBBLP samples was improved; and the adsorption of gas oxygen on the electrode surface is limited with porosity decreases. The work shows it is interesting and valuable to optimize the performance of SOFC cathode materials using a high entropy design.

Synthesis and functionalization of carbon nanostructures in a single‐step CVD process through the implementation of a recycled precursor

AbstractBackgroundRecycled materials are a major research topics of the new era to relieve pressure on raw material extraction from our planet and reduce its pollution levels. This has helped us to reinvent our relationship with nature, and to commit ourselves to a sustainable economic and social reconstruction. An excellent option to add value to waste while protecting the environment is the synthesis of carbon nanostructures (CNSs) using a recycled material as a precursor. In this research, the synthesis and functionalization of CNSss in a single‐step chemical vapour deposition (CVD) process was carried out using a recycled precursor. The methanol fraction is waste from the distillation process in the production of alcoholic beverages. The synthesis temperatures were 750, 800 and 850 °C.ResultsAs a result, carbon nanotubes, carbon nanoribbons and carbon nanobeads with diameters <100 nm and widths <500 nm were obtained. The crystal size of CNSs decreased with increasing synthesis temperature, from 20 to 12 nm. RAMAN spectra revealed the high degree of graphitization and the presence of different types of nanostructures. Carbonyl (CO) and hydroxide (‐OH) stretching of the carboxylic acid were present in all samples.ConclusionThe results obtained shown that the CNSs synthetized are functionalized in a single‐step CVD process using the methanolic fraction as a precursor. © 2024 Society of Chemical Industry (SCI).

High-Power-Density and Excellent-Flexibility Thermoelectric Generator Based on All-SWCNTs/PVP Composites.

Flexible polymer/single-wall carbon nanotube (SWCNT) composites are a vital component for wearable/portable electronics, but the development of their n-type counterpart is laggard. Furthermore, little attention is paid to the interaction between SWCNT and polymers, especially the unconjugated polymers, as well as the conversion mechanism of conduction characteristics. Here, the n-type flexible SWCNTs/Polyvinyl Pyrrolidone (PVP) films are successfully fabricated, where the oxygen atoms in PVP interacted with SWCNT via hydrogen bonds, which can lower the energy barrier of electron tunneling, providing the pathway for the electron transfer. Furthermore, with the increasing synthesis temperature, the hydrogen bonds strengthened and the thermal activation energy further improved, both of which enhanced the electron-donating ability of PVP, resulting in a high-power-factor value of 260µW m-1K-2. Based on the optimized SWCNTs/PVP films, a thermoelectric module is assembled, which achieved a power density of 400µWcm-2 at a temperature difference of 56K, coupled with excellentflexibility, showing a less than 1% variation of resistance after 5000 bending cycles. It shows the highest output-performance and the best flexibility among the reported SWCNT-based thermoelectric modules. This work provides significant insights into the interaction mechanism and performance optimization of hybrid thermoelectric composites, based on SWCNTs/unconjugated polymers.

Synthesis of Calcium Phosphate by Microwave Hydrothermal Method: Physicochemical and Morphological Characterization.

Bone loss in the alveolar ridge is a factor widely studied by dentists in implant surgeries, as it poses a major challenge for aesthetic and functional recovery in patients with large maxillary bone defects. Synthetic biomaterials function as grafts designed to replace and remodel bone tissue. Calcium phosphate is a biomaterial that has good properties such as biocompatibility and bioactivity, making it a reference in bone replacement treatments. A synthetic biomaterial such as calcium phosphate can be obtained by various synthesis techniques. The microwave hydrothermal method (HTMO) is a pathway that allows changes in synthesis parameters and significantly increases the transmission efficiency of materials such as synthetic calcium phosphate derivatives. The study proposes obtaining a biomaterial for bone grafting based on calcium phosphate by the microwave HTMO and evaluating its microstructural and physicochemical characteristics. The parameters tested in this process were temperature and reaction time. The calcium phosphate particulates were obtained by the microwave HTMO at temperatures of 110°C and 130°C for 60 min and calcined at 300°C, 500°C, and 700°C. Microstructural and physicochemical characterization analyses were carried out using scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The results obtained showed the presence of more than one calcium phosphate biological interest phase, as hydroxyapatite (HA), tricalcium phosphate (β-TCP), and octacalcium phosphate (OCP), highlighting with increasing calcination temperature, the β-TCP phase becomes evident. The proposed synthesis method was efficient in obtaining a biomaterial with suitable physical and chemical characteristics, with an association of crystalline phases of biological interest related to the increase in synthesis temperature and calcination temperature.

Understanding the effect of Mn2+ on Yb3+/Er3+ co-doped NaYF4 upconversion and obtaining the optimal combination of these tridoping

In this work, we investigated in detail the upconversion properties of several types of nanoparticles, including NaYF4:5%Yb3+/30%Mn2+, NaYF4:40%Mn2+/x%Yb3+ (x% = 1, 5, 10, 20, 30, and 40), NaYF4:2%Er3+/x%Mn2+ (x% = 20, 30, 40, 50, 60, and 70), NaYF4:40%Mn2+/x%Er3+ (x% = 1, 2, 5, and 10), and NaYF4:40%Mn2+/1%Yb3+/x%Er3+ (x% = 0, 2, 5, and 10). We studied their upconversion emission under 980 nm excitation in both pulsed and continuous wave modes at different synthesis temperatures. The nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The doping of Yb3+ and Mn2+ ions resulted in the nanoparticles assuming cubic and hexagonal crystal structures. The emission intensity increased (106.4 (a.u.*103) to 334.4(a.u.*103)) with increasing synthesis temperature from 120 to 140 °C, while a sharp decrease was observed when the synthesis temperature was increased to 200 °C. The gradual decrease in peak intensity with increasing Mn2+ concentration from 20 to 70% was attributed to energy transfer from Mn2+ to Yb3+. In NaYF4:Mn2+/Yb3+/Er3+ UCNPs, increasing the Er3+ concentration from 0 to 10% led to the disappearance of the blue, orange, and green emission bands. The intense upconversion luminescence pattern with high spatial resolution indicates excellent potential for applications in displays, biological sensors, photodetectors, and solar energy converters.

Synthesis and Characterization of Cr-Doped Pb2Fe2O5 Thin Films by Reactive Magnetron Sputtering

Multiferroic materials, which exhibit simultaneous ferroelectricity, ferromagnetism, and ferro-elasticity, have attracted significant attention due to their multifunctional properties. Coupling between ferroelectric and magnetic properties has led to the development of non-volatile memory devices, transducers, magnetic field sensors, and other applications. Pb2Fe2O5 (PFO) is a promising multiferroic material due to it simultaneously exhibiting ferroelectricity and ferromagnetism at room temperature. Doping with aliovalent ions, such as Cr3+, has been proposed as an effective method for enhancing the ferroelectric and magnetic properties, consequently leading to the enhancement of multiferroic properties. The investigation shows that the lead ferrite phase (220) was present in all samples, but its abundance reduced with increasing synthesis temperature due to lead desorption. Dielectric measurements revealed that PFO films with highest Cr concentration had the highest polarization (Pr) of 72.2 μC cm−2. The study also found that the magnetization of PFO films was up to 9.5·10−7 μAm2 at an ambient temperature of 5 K, and the magnetic ordering temperature was 363 K, corresponding to the magnetic ordering temperature of chromium oxides. The morphology of Cr doped PFO films changed with increasing chromium content, resulting in a reduction in grain size and an increase in the film density.

Electromagnetic interference shielding of graphene/PMMA composites depending on growth temperature of CVD-graphene

The research on graphene, driven by its exceptional mechanical, electrical, and thermal properties, has garnered significant attention, making it a promising multi-functional material for electronics. In this study, we investigated the effect of the synthesis temperature on the crystalline quality and the electromagnetic interference (EMI) shielding performance of graphene. We performed graphene synthesis on Cu foil at different temperatures (from 900° to 1050°C) and subsequently analyzed the samples using Raman spectroscopy. The results showed that the crystalline quality of graphene increased with increasing synthesis temperature. We then fabricated a 100-layer graphene/poly(methyl methacrylate) (PMMA) composite (GPC) and evaluated its electrical, mechanical properties, and EMI shielding effectiveness (SE). Our findings revealed the GPC with high crystalline graphene had a higher electrical conductivity and tensile strength than the GPC with defective graphene. In addition, the GPC with high crystalline graphene had a higher EMI SE, with a total SE of 14.16 dB, which is 140 % higher than that value for a defective graphene structure.

Elucidating the role of synthesis conditions on Zr-MOF properties and yield

Metal-organic frameworks (MOFs) are a new type of ultra-high surface area porous materials with applications in catalysis, energy storage, and gas adsorption. Compared to other MOFs, Zirconium-based MOFs (Zr-MOFs) demonstrate improved stability due to strong bonds between tetravalent zirconium and carboxylate ligands, making them applicable in real world conditions. This study aims to investigate optimal synthesis conditions for the solvothermal fabrication of Zr-MOFs by looking at two promising tetratopic ligand-based MOFs, Zr-TCPP and Zr-TPTC. By systematically investigating the impact of synthesis parameters on yield, crystallinity, and morphological characteristics, both general and specific trends were determined. The present work demonstrated that the ideal reactant ratio was twice the actual Zr:ligand ratio in the final structure. Stronger acid modulators were found to produce more crystalline samples for MOFs with flexible ligands (Zr-TPTC), where formic acid use resulted in more crystalline samples compared to acetic acid; however, this lowered the yield. The effect of temperature on yield was non-linearly dependent on the reactant ratio used for synthesising flexible Zr-TPTC. For MOFs with rigid ligands (Zr-TCPP), increasing synthesis temperature did not affect yield but decreased crystallite size and improved phase selectivity. Stability tests in water and acid were performed on both MOFs to assess the effect on crystallinity and morphology and the results showed expected trends for Zr-MOFs. The optimized synthesis parameters for Zr-TCPP resulted in a superior method of producing PCN-222 with higher yield and crystallinity. On the other hand, a new Zr-TPTC MOF with high yield and crystallinity was synthesised using the optimized parameters. This study thus elucidates the role of synthesis parameters on Zr-MOF properties and yield and furthers the understanding of MOF synthesis mechanisms, expanding the potential for their applicability in industry.

Preparation and Performance of Building Fire Protection and Insulation Materials

In this paper, a series of calcium silicate thermal insulation materials were prepared by hydrothermal method, and their structure, mechanical properties and thermal insulation properties were systematically studied by adjusting their preparation process, aiming to develop a new type of calcium silicate thermal insulation material with excellent performance. We found that the product gradually changed from a dense flocculent substance on the surface to a loose needle rod substance, and the grain grew, and the crystallinity increased with the increase of synthesis temperature. As the initial calcium silicon ratio increases, the surface pores of the product increase, and the surface gradually becomes loose from dense, resulting in the appearance of tobermorite and xonotlite phases.

Çevre Dostu Karbon Nano Fiberlerin Kimyasal Buhar Biriktirme Tekniği Kullanılarak Metanol ile Sentezlenmesi

This study aims to investigate the suitability of methanol as a carbon source for the synthesis of carbon nanofibres (CNFs), currently used in wastewater, water, and air purification systems, by chemical vapor deposition (CVD) in the presence of NiO catalyst. Experimental studies were carried out in a tube furnace under isothermal conditions. Catalyst particles were loaded onto silicon wafers with orientation by dip coating to grow CNFs. The reduction behavior of nickel oxide powder at 1000 K under non-isothermal and isothermal conditions was investigated before CNF synthesis studies. The percentage reduction of nickel oxide powder under non-isothermal conditions was 82.03%. The percentage reduction under isothermal conditions for 30 min was 78.03%. The experimental result obtained is very close to the theoretical value (78.57%). During CNF synthesis experiments, it was observed that CNF formation was not achieved at temperatures of 1000 - 1100 K due to the poor thermal decomposition of methanol. Pyrolysis of methanol increased with increasing synthesis temperature (1200 K), which promoted the synthesis of CNFs. SEM analysis revealed morphologically dense CNF formation under isothermal conditions for 20 min at 1300K synthesis temperature.

A Series of Novel 3D Coordination Polymers Based on the Quinoline-2,4-dicarboxylate Building Block and Lanthanide(III) Ions-Temperature Dependence Investigations.

A series of novel 3D coordination polymers [Ln2(Qdca)3(H2O)x]·yH2O (x = 3 or 4, y = 0-4) assembled from selected lanthanide ions (Ln(III) = Nd, Eu, Tb, and Er) and a non-explored quinoline-2,4-dicarboxylate building block (Qdca2- = C11H5NO42-) were prepared under hydrothermal conditions at temperatures of 100, 120, and 150 °C. Generally, an increase in synthesis temperature resulted in structural transformations and the formation of more hydrated compounds. The metal complexes were characterized by elemental analysis, single-crystal and powder X-ray diffraction methods, thermal analysis (TG-DSC), ATR/FTIR, UV/Vis, and luminescence spectroscopy. The structural variety of three-dimensional coordination polymers can be ascribed to the temperature effect, which enforces the diversity of quinoline-2,4-dicarboxylate ligand denticity and conformation. The Qdca2- ligand only behaves as a bridging or bridging-chelating building block binding two to five metal centers with seven different coordination modes arising mainly from different carboxylate group coordination types. The presence of water molecules in the structures of complexes is crucial for their stability. The removal of both coordinated and non-coordinated water molecules leads to the disintegration and combustion of metal-organic frameworks to the appropriate lanthanide oxides. The luminescence features of complexes, quantum yield, and luminescent lifetimes were measured and analyzed. Only the Eu complexes show emission in the VIS region, whereas Nd and Er complexes emit in the NIR range. The luminescence properties of complexes were correlated with the crystal structures of the investigated complexes.

L and S band microwave absorption properties of Z-type hexaferrite Ba3Co2Fe24O41 synthesized at low temperature

The L-band and S-band electromagnetic waves are widely utilized in radar and satellite communications. This paper reports the successful synthesis of 85.8% content Ba3Co2Fe24O41 (Co2Z) at a relatively low temperature of 1150 °C using the solid-phase method with BaFe12O19 (BaM) and Ba2Co2Fe12O22 (Co2Y) as precursors. The Co2Z samples were confirmed to have been successfully synthesized using X-ray diffraction (XRD) and thermogravimetry/differential scanning calorimetry (TG-DSC) spectra. Scanning electron microscopy (SEM) images revealed that the sintered samples exhibited large grains (>10 µm). Vibrating-sample magnetometry (VSM) data indicated that the synthesized Co2Z samples possessed distinct soft magnetic properties. X-ray photoelectron spectroscopy (XPS) results showed that the Fe3+ content decreased with the increase in synthesis temperature. The samples synthesized at 1110 °C − 1280 °C had a permeability of 10–20, a cut-off frequency of approximately 1 GHz, and a dielectric constant of 10–30. When the thickness of the sample synthesized at 1150 °C was 3.9 mm, the frequency range of the reflection loss (RL)< −10 dB was 2.55 GHz (0.98–3.53 GHz), with 1.77 GHz as the center frequency, and RLmin was − 57.8 dB. This observation indicates that the effective absorption bandwidth of the samples covers the entire L and S bands, which significantly satisfies practical applications within the military and civilian sectors.

Phase-Dependent Dual Discrimination of MoSe2/MoO3 Composites Toward N,N-Dimethylformamide and Triethylamine at Room Temperature.

Herein, we present, a chemiresistive-type gas sensor composed of two-dimensional 1T-2H phase MoSe2 and MoO3. Mixed phase MoSe2 and MoSe2/MoO3 composites were synthesized via a facile hydrothermal method. The structure analysis using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy revealed the formation of different phases of MoSe2 at different temperatures. With increase in synthesis temperature from 180 to 200 °C, the relative percentage of 1T and 2H-MoSe2 phases changed from 80 to 48%. On the other hand, at 220 °C, 2H-MoSe2 was obtained as a major component. The gas sensing properties of individual MoSe2 and composites were investigated at room temperature toward various analytes. The obtained results revealed that composites possess improved sensing features as compared with individual MoSe2 or MoO3. Data also revealed that the composite with dominating 1T-phase exhibits relatively higher response (10%, at 10 ppm) for dimethylformamide (DMF) compared to triethylamine (TEA) (3%, at 10 ppm). In contrast, the composite with larger 2H-phase exhibited affinity toward TEA and had a relative response of about 2%. Therefore, selectivity of a sensor device can be tuned by an appropriately designed MoSe2/MoO3 composite. These results signify the importance of MoO3-based composites with dual-phase MoSe2 for successfully discriminating between DMF and TEA at room-temperature.