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Trace-level detection of isopropanol is important for human health monitoring and air quality surveillance. In this work, we report synthesis of high surface area two-dimensional (2D) nanoflakes of CuAl 2 O 4 using surfactant-assisted hydrothermal process and its application in ppb level detection of isopropanol. X-ray diffraction revealed the polycrystalline nature of the spinel and a nano crystallite size of 42 nm. The 2D morphology of CuAl 2 O 4 was confirmed using field emission scanning electron microscope whereas BET revealed the mesoporous nature and a high surface area of 41.8 m2g-1. The surface oxidation states of the material were found through X-ray photoelectron spectroscopy. The 2D CuAl 2 O 4 demonstrated excellent sensing towards isopropanol with its response varying from 11.8 to 84.5 % (500 ppb–10 ppm) at 300 °C. The limit of detection of the spinel was found to be 56 ppb at its optimum operating temperature of 300 °C. In addition, the sensing layer was found to have response times in range 1101 s for 500 ppb to 168 s for 10 ppm and recovery times in the range 300 s for 500 ppb to 570 s for 10 ppm. [ABSTRACT FROM AUTHOR]

The woven carbon fibers (WCF) fabrics were functionalized by growing copper-oxide (CuO) nanostructures using Seed-assisted hydrothermal technique. The effective growth of CuO on surface hydrolyzed WCF samples were achieved by seeding followed by growth treatment in the prepared precursor solution. The impact of hydrothermal process parameters such as number of seeding cycles, duration of growth treatment and molar concentration of growth solution were studied by performing 96 set of experiments with three repetitions. In this work detailed analysis of structural, morphological, and elemental attributes of the CuO-coated WCF fabrics samples have been done. The WCF fabrics were uniformly coated with monoclinic CuO nanostructures having nanopellets, nanoflakes, nanowires, and nanoflowers morphologies. Different characterization techniques such as field emission scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR spectroscopy and thermo-gravimetric analyzer were used to study different attributes of CuO-modified WCF samples. The number of seeding treatments and the length of growth treatment had a significant impact on growth of CuO nanostructures on WCF. The detailed analysis exhibits that the developed CuO-modified WCF samples may enhance interfacial surface area, bonding capacity and reduce void content by allowing nanostructures to cross-link together and with polymer matrix while fabricating composite materials. [ABSTRACT FROM AUTHOR]

N-butanol, a volatile organic compound prevalent in numerous industrial processes, poses significant risks to human health and the environment if not properly monitored. Consequently, the development of high-sensitivity n-butanol sensors is imperative. For this reason, NdFeO 3 nanoparticles were successfully synthesized by hydrothermal method and used for the detection of n-butanol. They were fully analyzed using characterization techniques such as XRD, BET, EDX, SEM, TEM and XPS. The test results revealed that the prepared samples exhibited a granular structure with an average diameter of approximately 65 nm. The specific surface area measured 15.415 m2/g, and the pore size was determined to be 16.638 nm. The NdFeO 3 sensor responds up to 441 for 100 ppm n-butanol at 260 °C, response and recovery times were 33 s and 7 s respectively. The response value of the NdFeO 3 sensor is still 4.3 for 1 ppm n-butanol with a minimum detection limit of 0.024 ppm. Simultaneously, the NdFeO 3 sensor has excellent selectivity, stability and moisture resistance. These good sensing properties indicate that this work provides a possible strategy for developing an economical and repeatable high performance gas sensor for the detection of n-butanol. [ABSTRACT FROM AUTHOR]

ZnO is a promising thermoelectric ceramic material, but the low electrical conductivity and high thermal conductivity restrict its satisfactory thermoelectric performance. Chemical doping is an effective way to improve the thermoelectric properties of ZnO. Due to the valence states and similar ionic radii of Fe3+ and Zn2+, Fe was selected as the effective dopant for ZnO. In this work, Fe-doped ZnO samples were prepared using hydrothermal synthesis and microwave sintering technology under oxygen-depleted conditions. The electrical conductivity of sintered Fe-doped ZnO was greatly improved owing to the energy band adjustment. The maximum power factor of 3108 μW/mK2 at 800 K was obtained from Zn 0.997 Fe 0.003 O, which is about 4.4 times greater than that of pure ZnO. Meanwhile, the small grain size (300–500 nm) and residual pores resulted from microwave rapid sintering in an oxygen-depleted environment, as well as the point defects caused by Fe3+ substituting for Zn2+, significantly reduced the thermal conductivity. Finally, the highest ZT value of 0.91 has been achieved in Zn 0.997 Fe 0.003 O at 800 K. [ABSTRACT FROM AUTHOR]

Employment of yeasts as bio-templates to obtain hollow structured microspheres is recognized as a promising strategy in the view of resource utilization and sustainable development. In this study, carbon modified Bi 2 MoO 6 /Bi 2 S 3 hollow microspheres with rich oxygen vacancies were successfully prepared via in situ hydrothermal synthesis instead of removing yeast templates by calcination. As-obtained samples were characterized using SEM, EDS, TEM, XRD, XPS, EPR and UV–vis DRS analysis. It was shown that carbon modified Bi 2 MoO 6 /Bi 2 S 3 hollow microspheres, with a diameter of 2.2 μm, inherited the ellipsoidal shape from primitive yeast templates. In situ hydrothermal synthesis not only resulted in the integration of yeast-derived carbon into the Bi 2 MoO 6 structure through Bi–O–C and Mo–O–C bonds, but also produced oxygen vacancy defects in the sample. Under visible light irradiation, the carbon modified Bi 2 MoO 6 /Bi 2 S 3 photocatalyst exhibited an excellent degradation efficiency, achieving 87.0 % removal of methylene blue (MB) within 100 min. With photoelectric tests and active species trapping experiments, the potential mechanism for the remarkable photocatalytic performance of carbon modified Bi 2 MoO 6 /Bi 2 S 3 was discussed preliminarily. This work explored an economical, simple and feasible approach for the multi-strategy modification of photocatalysts, and provided a new cognition on the versatile application of biological templates in material design and fabrication. [ABSTRACT FROM AUTHOR]

The study proposes the utilization of microwave-assisted methods for converting neutralization slag (NS) into hydroxyapatite (HAP), offering an alternative to the conventional hydrothermal method. The microwave-assisted approach addresses the challenges encountered in hydrothermal reactions, such as particle agglomeration, reduced specific surface area, prolonged reaction time, high temperature requirements, and inadequate saturation adsorption capacity. By employing the response surface methodology with a Box-Behnken design, the study found that the microwave-assisted method significantly reduced the synthesis time from 90 to 25 min and the temperature from 120 °C to 56 °C. Furthermore, the microwave method consumed only 1/43 of the energy utilized in hydrothermal synthesis. To assess the performance of the synthesized HAP, various detection methods were utilized, including XRD, SEM-EDS, FTIR, Zeta potential, and ICP, which analyzed the crystal structure, crystallinity, morphology, chemical composition, and surface charge of HAP. The BET method was used to measure the specific surface area, further confirming the successful synthesis of HAP. The HAP synthesized through this microwave-assisted method exhibited a saturation adsorption capacity of up to 98.4 mg/g of fluoride ions from vanadium industrial raffinate. This study demonstrates that the microwave-assisted method provides a viable solution for reducing energy consumption and enhancing HAP synthesis efficiency for wastewater treatment in the vanadium industry. [Display omitted] [ABSTRACT FROM AUTHOR]

Quartz glass powder is a type of silicon-rich industrial waste. Accumulation of this waste has led to resource wastage and environmental pollution. In this paper, quartz glass powder is used as raw material for preparing xonotlite through hydrothermal synthesis. The effects of Ca/Si (C/S) molar ratio, liquid/solid ratio, reaction temperature, and reaction time on the conversion of quartz are studied. The phase and structural changes of glass powder are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Based on this, the conversion mechanism of quartz in glass powder is explained. The dissolution rate of quartz in an alkaline solution is a critical factor that restricts hydrothermal reactions. The conversion rate of quartz can be effectively increased by raising reaction temperature and extending reaction time. When the reaction temperature is 240 °C and the reaction time reaches 14 h, the conversion of quartz can reach 94.5 wt%. This study reveals the conversion mechanism of quartz in hydrothermal reactions and provides a theoretical basis for the efficient utilization of glass powder. [ABSTRACT FROM AUTHOR]

This study aims to enhance electrochemical energy storage in supercapacitors by optimizing the synthesis temperature of MoO 3 nanostructures using a hydrothermal technique. MoO 3 nanostructures were synthesized using a hydrothermal technique, with reaction temperatures ranging from 140 to 230 °C for 24 h. The materials were analyzed using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The findings indicate that at 200 °C, a pure hexagonal phase of MoO 3 was obtained, while different temperatures resulted in a combination of orthorhombic and hexagonal phases. The SEM analysis demonstrated that the morphology of the MoO 3 nanostructures varied depending on the synthesis temperature. These variations encompass the particles, spherical planar structures, and nanorods. The prepared samples were subjected to electrochemical analysis to explore their electrochemical properties, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD). The electrochemical performances of the prepared samples varied depending on the temperature at which the MoO 3 samples were prepared, resulting in different morphologies. The sample prepared at 220 °C exhibited the highest specific capacitance (C S) of 330 F/g, a minimal charge-transfer resistance (R CT) of 1800 Ω, an energy density of 16.50 Wh/kg, and a power density of 150 W/kg with symmetric and asymmetric device C S values of 125 and 115 F/g, respectively, compared to the other prepared samples. The observed outcomes can be attributed to the diverse morphology of MoO 3 nanostructures and the high electrochemical active surface area (ECSA) of 7.43 × 10−5 F/cm2 that were synthesized at different hydrothermal temperatures. This diversity in morphology and ECSA leads to the presence of active surface area sites, thereby enhancing electrochemical activity. These findings highlight the effect of synthesis temperature on the morphology, crystal structure, and electrochemical performance of MoO 3 nanostructures for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Strategies to make more efficient use of sunlight have been developed. Different synthesis parameters have been studied for the production of multiphase photocatalysts. In this work, for the first time, the performance of a one-step nitrogen-assisted hydrothermal synthesis of TiO 2 using TiO 2 –P25 as a Ti precursor was investigated for the degradation of methylene blue under visible light irradiation. Urea and ethylenediamine (EDA) were evaluated as nitrogen sources. The produced photocatalysts had a rod-like nanostructure with the formation of mesopores. The resulting phase was a heterojunction of anatase, TiO 2 (B), and rutile, which enhanced charge separation. The presence of nitrogen during the hydrothermal reaction altered the morphology of TiO 2 , impacting the crystallite size. The U photocatalyst (urea source) achieved the best result for visible light with prior adsorption, degrading around 11 % of methylene blue in 5 h. This shows that it is possible to obtain a photocatalyst with superior performance to TiO 2 –P25 under both ultraviolet and visible light. This study presents an efficient strategy for improving the optical response of TiO 2 by using nitrogen during a hydrothermal reaction, which has potential for industrial applications. • TiO 2 was synthesized by a one-step hydrothermal reaction with nitrogen. • Urea and ethylenediamine were used as nitrogen sources. • The nitrogen sources altered the morphology of the TiO 2. • Adsorption affected the photocatalytic activity and kinetic constants. • The best photocatalytic performance was for the urea-assisted reaction. [ABSTRACT FROM AUTHOR]

Concerning environmental issues, including global warming and the reduction of hydrocarbon assets, the utilization of environmentally sustainable energy production is imperative nowadays. In this regard, water electrolysis is considered the most prominent and ecologically sustainable technique for the production of hydrogen. However, owing to its sluggish OER, designing electrode materials with remarkable efficiency becomes crucial for boosting the functioning of water electrolysis. In the present investigation, we successfully developed the SnSe catalyst incorporated into graphitic carbon nitride (g-CN) via a simple hydrothermal approach. The various approaches were used to characterize g-CN/SnSe nanocomposite. Meanwhile, g-CN/SnSe nanocomposite demonstrated exceptional catalytic properties for OER under 1.0 M alkaline electrolyte (KOH), which exhibited low overpotential (241 mV) to obtain ideal j (10 mA cm−2) and an exceptional stability (20 h). It also demonstrated a low onset potential (1.27 V), a significant electrochemical active surface area (ECSA) of 592.5 cm2 and an impressive Tafel value (38 mV dec−1), significantly superior to the pure SnSe nanomaterial. The observed improved performance can be attributed to enhanced morphological properties and significant surface area. The above-reported nanocomposite (g-CN/SnSe) shows great potential for OER and other electrochemical systems because of its numerous active sites, faster electron transfer process, exceptional durability and good electrical conductivity. [ABSTRACT FROM AUTHOR]

Owing to their flexibility and high thermal resistance, para-aramid based Kevlar™ fabric substrates are an ideal candidate for obtaining flexible gas sensors for new-generation wearable technologies. The morphology of the surface of the substrate where the target gas comes into contact directly affects the important features of the sensor such as detection limit, selectivity, and response. In this context, a feasible technique is introduced to enhance the efficiency of flexible gas sensors utilizing ZnO/Kevlar™, entailing the modification of ZnO morphology. ZnO based gas sensing layers were deposited on Kevlar™ fabric substrates by a two-stage method. Initially, seed layer was produced on Kevlar™ fabric using the ultrasonic bath method, with five different seed layer processing times ranging from 1 min to 20 min. In the nucleation, all nanostructured layers were deposited by hydrothermal method with constant parameters and under the same conditions. As the seeding time was increased, nanorods (1D) formed on the surface became flakes (2D), leading to considerable improvement in NH3 gas sensing properties. The sensor with a 5-min seeding time showed a sensitivity of 49 % at an optimal operating temperature of 190 °C, while the sensor produced in 20 min showed the best response performance with 169 % at 130 °C for 50 ppm NH3 gas. The increase in seeding time not only reduced the operating temperature of the gas sensor through the conversion from 1D nanostructure to 2D, but also significantly increased the sensor response. Under constant hydrothermal conditions and solution concentration, the density per unit area increases. However, after 10 min of seeding, the length of nanorods shortens and turn into a rod-flake hybrid morphology. A superior sensor performance was demonstrated for the samples examined. The obtained results also showed that flexible Kevlar™ fabric could be a feasible and interesting substrate for nanostructured ZnO-based NH3 gas sensors. [Display omitted] [ABSTRACT FROM AUTHOR]

A hydrothermal method was employed to synthesize the precursor of nano-zirconium carbide, which was subsequently heat treated at high temperatures under vacuum to obtain finely dispersed nanometer-sized zirconium carbide powder through a carbothermic reduction reaction. Scanning Electron Microscopy (SEM) was utilized to examine the microstructure of the precursors obtained under different hydrothermal conditions and carbon contents. The effects of different heat treatment temperatures on the microstructure of the products were analyzed. Transmission Electron Microscopy (TEM) confirmed the boundary coating structure of the hydrothermal precursor and provided insights into the phase structure of the nanometer-sized zirconium carbide. The reaction mechanism and temperature involved in the carbothermic reaction process were determined through calculations. Furthermore, the energy, phase and microstructure of the reaction were investigated using Thermogravimetric Analysis (TG-DSC) and X-ray Diffraction (XRD) at different temperatures. The obtained results revealed that the zirconium carbide precursor was synthesized via the hydrothermal method exhibited a core-shell structure with a boundary coating, which not only ensured uniform contact between C and ZrO 2 particles but also facilitated the formation of zirconium carbide. The results show that the most suitable process parameters are Zr/C 1: 7, 240 °C and 24 h. The thermodynamic calculation results show that ZrO 2 combines with carbon to form CO and ZrC when the temperature reaches 1656.56 °C. As the temperature rises, CO reacts with ZrO 2 to form ZrC and CO 2. TG-DSC shows that the carbothermal reduction reaction starts at 1100 °C and reaches its peak at 1418 °C. XRD analysis confirms that when the temperature reached 1450 °C ZrC appeared. At 1600 °C, the phase transition of ZrC is basically completed. TEM images showed that the synthesized zirconium carbide particles were about 30 nm. [ABSTRACT FROM AUTHOR]

Hydrogen zirconium phosphate (HZP) is a ceramic material with the formula HZr 2 (PO 4) 3 that can potentially offer anhydrous protonic conductivity, with thermostability for the intrinsic protons up to 650 °C, and good chemical stability in aqueous environments or acid gases. Despite the attraction of these features for electrolyte applications, such as gas separation, fuel cells or electrolysers, work on this material remains in its infancy. A possible reason for this lack of attention may be related to the complexity to obtain the HZP material as a pure phase. For this reason, the current article examines a new hydrothermal synthesis method to produce the ammonium precursor, NH 4 Zr 2 (PO 4) 3 , in its phase pure form, and consequently a refined overall route to produce the desired HZP target material. In the synthesis of the ammonium precursor, we underscore the precise control of reaction conditions that are necessary to obtain the pure NH 4 Zr 2 (PO 4) 3 material, both in its cubic and hexagonal structural polymorphs. For reaction times of 10 h, the cubic phase is obtained by employing a hydrothermal temperature of 150 °C and an aqueous ammonia volume of 2.1 mL, while the hexagonal phase is obtained for a hydrothermal temperature of 200 °C and an aqueous ammonia volume between 2.3 and 2.4 mL. Subsequently, we investigate the required conditions to convert hexagonal NH 4 Zr 2 (PO 4) 3 fully to hexagonal HZr 2 (PO 4) 3 via thermal treatment at 600 °C for 5 h, assessed by a combination of X-ray diffraction and infrared spectroscopy. In this way this article aims to open up further research on this interesting HZP material by documenting a robust route for its preparation. [ABSTRACT FROM AUTHOR]

It is prominent and imperative to synthesize gas-sensitive materials using energy-efficient and environmentally friendly methods to enhance their properties. The current paper employs hydrothermal method porous reduced graphene oxide (P-rGO) and zinc oxide (ZnO) with flower-like structure complexes (PGZ) to detect the acetone gas. The gas sensitivity of the PGZ sensor demonstrate a response of 30.38 for 50 ppm acetone, accompanied by a rapid response recovery time of 5 s/7 s at operating temperature of 240 °C. Moreover, the remarkable long-term stability (<15 % fluctuation over 9 cyclic response cycles and 7 weeks of intermittent testing) of the PGZ gas sensor ensures its suitability for practical applications. The P-rGO enlarges the specific surface area of the material, which is conducive to accelerating the electron transfer in the reaction as well as the adsorption and desorption of the target gas, resulting in a rapid response recovery time. The porous structure can also effectively inhibit the agglomeration and growth of ZnO nanoparticles, thus improving long-term stability. Consequently, our study provides a new strategy for the application of 2D materials in gas sensing. [ABSTRACT FROM AUTHOR]

In this work, a simple one-step hydrothermal synthesis of La doped SnO 2 nanocomposites was studied. The structure, morphology, specific surface area, and chemical composition were determined by XRD, SEM, BET, and XPS techniques. The gas sensing performance of SnO 2 and La/SnO 2 nanocomposites with varied La doping dosages on n-butanol gas was systematically investigated. The results manifested that under the testing environment (50 % relative humidity and 30 °C), La doped SnO 2 nanocomposite sensor presented high response (69), excellent selectivity, good repeatability and long-time stability to n-butanol gas at 160 °C. Especially, the 7 mol% La doped SnO 2 sensor displayed a 5.9 times higher response to 50 ppm n-butanol than the SnO 2 sensor. In comparison with bare SnO 2 , La doping increased the band gap value of 7 mol% La/SnO 2 nanocomposite by 6.23 %, decreased particle size by 11.83 %, and increased the oxygen defect concentration by 6.07 %. Due to the synergistic effect of the above factors, the gas sensing performance of La doped SnO 2 nanocomposites towards n-butanol gas was enhanced. Therefore, La doped SnO 2 nanocomposites might be a potential gas sensing material for monitoring n-butanol gas at relatively high humidity. [ABSTRACT FROM AUTHOR]

A solid-liquid composite lubrication coating capable of controlling friction and wear has received widespread attention among researchers. Here, a novel self-lubricating ceramic coating was created through a combination of thermal spraying, hydrothermal reactions, and vacuum impregnation. Its mechanical properties, tribological performance, and self-lubrication mechanism were thoroughly analyzed. The results indicate that the thermally sprayed ceramic coating contained carbon spheres and perfluoropolyether. As a result of the in-situ synthesis of carbon spheres, the coating exhibited enhanced mechanical properties. Compared to the single solid lubricant coating, the solid-liquid composite coating decreased the coefficient of friction by 46.7% to 0.112 and decreased the wear rate from 1.25 × 10−6 mm3/m N to 3.70 × 10−7 mm3/m N. It is proposed in this work that solid-liquid composite coatings can be prepared by utilizing the defects such as pores and microcracks inherent in thermal spray coatings for introducing solid lubricating phases and liquid lubricating phases. This strategy addresses the issue of degradation of the mechanical properties of conventional ceramic-based self-lubricating coatings due to their tribological design. [ABSTRACT FROM AUTHOR]

We present a study on the hydrothermal synthesis of BaTiO 3 utilizing NaTi 3 O 6 (OH)- (H 2 O) 2 nanowires, which was conducted by controlling temperature, alkalinity and time. Initially, increased temperature has promoted the synthesis of BaTiO 3 and induce a change in the morphology. When the temperature increases within the range of 90 °C–210 °C, the morphology of the product transitions from nanoparticle to spindle-shaped to nanowires. Then, a time-dependent experiment was conducted to investigate the mechanisms involved in the transformation of the morphology. The formation of nanoparticle occurs through the process of dissolution-crystallization, while the formation of BaTiO 3 nanowires is attributed to hydrothermal ion exchange. Also, the hydrothermal process is characterized by grain aggregation and grain growth. By investigating the synthesis and morphology evolution of BaTiO 3 , this work holds significant potential for the synthesis of BaTiO 3 nanowires or other perovskite-type MTiO 3 employing titanate as a precursor. [ABSTRACT FROM AUTHOR]

This work presents for the first time one-step ultrafast (precursor-free) synthesis of 1D MnFe 2 O 4 (MFO) nanorods and soft magnetic colloidal nanoparticles (NPs) using microwave-assisted hydrothermal (MAH) methods, with or without citric acid (CA) as a surfactant (in situ synthesis), respectively. The mechanism of growth of spinel MFO nanostructures during the MAH synthesis was studied by varying synthesis duration (3–6 h) and temperature (180–200 °C). An increase in both the duration and temperature improved the purity of the samples, up to 97%. On the other hand, a temperature increase by 20 °C notably shortened the formation time of MFO nanorods, which have an average diameter and length of less than 20 nm and 350 nm, respectively, as observed at 200 °C after 6 h. All the fabricated MFO NPs with spherical and rod-like morphologies manifested high saturation magnetization in the range of 54–64 emu/g. The chelation of lattice metal ions by CA resulted in the formation of a stable colloid comprising 100% pure spinel MFO NPs with a size of ≤32 ± 10 nm (mean ± SD) and featuring very soft magnetic properties. This colloid was generated by the MAH synthesis at 175 °C within 30 min. Notably, an increase in synthesis duration from 30 min to 3 h diminished MFO phase purity from 100% to 52% and saturation magnetization from 43.4 ± 0.7 to 33.9 ± 2.0 emu/g for CA-functionalized MFO NPs owing to CA degradation increasing during the in situ MAH synthesis with longer duration. This study indicates good potential of ultrafast MAH synthesis for the development of 1D magnetic spinel nanostructures with controllable morphology, size, magnetic properties, and colloidal stability, thereby offering a wide range of applications within the fields of adsorption, catalysis, electronics, and biomedicine. [ABSTRACT FROM AUTHOR]

In the last decade, mesoporous hydroxyapatite (HA) materials have received much attention regarding environmental applications (including adsorption of soil and water contaminants, films for lithium batteries, catalysts, and support systems for catalysis) and open up ample opportunities regarding biomedical devices and structures. Molybdenum ions may strongly influence catalytic and sorption properties of materials. The present study shows an influence of hydrothermal-synthesis conditions (including temperature and duration of the treatment) on phase composition, textural properties, and morphology of molybdate-containing HA. Powders with high crystallinity manifested Brunauer–Emmett–Teller specific surface area up to 55 m2/g with a pore volume of 0.33 cm3/g. The molybdate-containing HA powders were investigated by chemical analysis, X-ray diffraction, Fourier-transform IR spectroscopy, and transmission electron microscopy. Their specific surface area, pore volume, and pore size distributions were determined by low-temperature nitrogen adsorption measurements, zeta potential was quantified, and electron paramagnetic resonance spectroscopy was performed. The concentration of MoO 4 2− preserving the one-phase state was found, and the impact of hydrothermal treatment mode was analyzed by machine learning using artificial neural networks. [Display omitted] [ABSTRACT FROM AUTHOR]

Here in the present work, simple, eco-friendly and economical method of synthesis has been approached known as hydrothermal synthesis that allowed easy doping of Fe ions into the ZnS host lattice. A unique approach was adopted for the first time to prepare ZnS material where thioglycolic acid (TGA) was used as a source for sulfur in addition to a reducing and capping agent. Properties of the nanostructures were explored using different techniques. The X-ray diffraction (XRD) results indicated formation of single phase hexagonal ZnS material where inclusion of Fe2+ ions into the ZnS lattice have no influence on the crystal phase of the material. Probably almost identical sizes of Zn2+ and Fe2+ ions made this possible that indicated Fe2+ ions take Zn2+ vacant sites by substitution of Zn2+ ions by Fe2+ ions. Chemical analysis (X-ray photoelectron spectroscopy) performed discovered that Zn and Fe ions were present in +2 oxidation states whereas S is in −2 state. Anisotropic growth of the nanostructures is reported where irregular shaped nanostructures of varying dimensions were formed that agglomerated as doping concentration was increased to form spherical microstructures. Inclusion of Fe ions into the host material modified magnetic behavior of the nanostructures converting diamagnetic ZnS into a ferromagnetic material. Optical properties were also influence by the doping resulting in photon absorption at different wavelengths. The band gap got reduced from 3.2 eV to 2.7 eV making the ZnS nanostructures visible light active. The nanostructures with band gap 2.7 eV exhibited good photocatalytic activity against methylene blue (MB) dye under visible light illumination degrading 94% of the dye in just 2 h. The scavenging experiments performed showed hydroxyl free radicals play an active role in mineralizing the dye. Reusability and post photocatalytic properties of the photocatalysts determined their stability and potential ability for possible commercialization. [ABSTRACT FROM AUTHOR]

In this work, distinct-morphological Co 3 O 4 /Nickel foams were prepared through a simple hydrothermal method and a subsequent heat treatment process. The morphology of Co 3 O 4 can be efficiently modulated from hexagonal nanosheets to nanobunches and urchin-like microspheres by manipulating the NH 4 F concentration. For the urchin-like Co 3 O 4 /Nickel foam composites, the minimum reflection loss (RL min) value can reach −42.53 dB at a matching thickness of 2.7 mm. Theoretical analysis shows that the enhanced microwave absorption intensity is mainly originated from dielectric losses including significant interfacial polarization of the abundant interfaces, intrinsic dipoles of Co 3 O 4 and magnetic losses containing natural resonance and eddy current loss are favorable for the impedance matching. Simultaneously, multiple scattering occurring within the 3D Ni network skeleton are considered to promote the microwave absorption performance. Furthermore, a quadrilateral cone array of the resultant urchin-like Co 3 O 4 /Nickel foam composites has a RL min of −56.7 dB and an effective absorption bandwidth can achieve 9.44 GHz. This work could be beneficial for exploiting high-efficient magnetic-dielectric microwave absorption materials via the microstructural design. [ABSTRACT FROM AUTHOR]

Doping and particle size controlling are two important approaches to improve the electrochemical performance of LiMn x Fe 1−x PO 4 cathode materials. By employing a straightforward hydrothermal method and utilizing cost-effective lithium phosphate (Li 3 PO 4) as the precursor, we successfully synthesized high Mn-content LiMn 0.79 Fe 0.2 Mg 0.01 PO 4 /C composites. The results reveal that the minute amount of Mg substantially enhances the electrochemical performance. In the subsequent mechanism study using Li 3 PO 4 precursors with different particle size, we found that the nucleation process, dependent on specific surface area and diffusion rate, is likely to play a critical role for the size and morphology of formed LiMn 0.79 Fe 0.2 Mg 0.01 PO 4. LiMn 0.79 Fe 0.2 Mg 0.01 PO 4 /C (LMFP-1), synthesized from initially smaller-sized and less agglomerated Li 3 PO 4 (LPO-1), exhibited the most diminutive average particle size coupled with the highest specific surface area, which further facilitated electrolyte interfacial interaction and promoted Li+ diffusion kinetics. At 1C, LMFP-1 displayed a specific capacity of 110.7 mAh g−1, with 97.07% capacity retention after 200 cycles. This study provides pivotal insights for the synthesis of high-performance LiMn x Fe 1−x PO 4 materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2) nanocrystalline materials are of great interest as for modern electronics and photonics as well as for energy saving technologies. Nevertheless, there still remains a challenge to realize their controllable synthesis, as evidenced by the low rate of implantation of existing technologies into mass production. Here, a hydrothermal reaction in a water-ethylene glycol (EG) solution has been coupled with the post-deposition annealing, yielding a range of phase-pure vanadium dioxide nanostructures on single-crystal r-sapphire substrate. A directed change in the viscosity of the precursor solution by using a change in the EG : H 2 O ratio makes it possible to control the nucleation rate and thus form VO 2 isolated nanocrystals, as well as their ordered ensembles with regular distribution and uniform films on the substrate. The obtained nanostructures were extensively characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy combined with energy-dispersive X-ray spectroscopy. Continuous VO 2 nanostructures demonstrated a metal-insulator transition (MIT) with a jump in resistivity of about 103–104, as well as a giant terahertz (THz) modulation depth up to 86 % (in the range from 0.3 to 2.0 THz), which confirms their high-quality and the possibility of their use in the creation of functional electronic and THz optical devices. [ABSTRACT FROM AUTHOR]

A wet chemical synthesis of a novel 2D/3D hierarchical Z-scheme that utilizes manganese oxide decorated 2D Ti 3 C 2 MXene (MnO 2 @MXene), which is designed for effective utilization in environmentally sustainable applications, is presented in this study. The synergistic role of 20 nm thick MnO 2 nanopetals (NPTs) and MXene sheets, which inhibited the electron/hole pair recombination and improved the surface activity, enhanced the catalytic properties of the material. This was facilitated by the unique 3D/2D structural characteristics of MnO 2 NPTs and MXene. The MnO 2 nanopetals NPTs integrated the MXene-based photocatalyst, which was synthesized using the ultrasonication approach, removed ∼99 % of the methylene blue dye (MB) and 75 % of the phenol within 30 min. The antibacterial test of the as-prepared MnO 2 @MXene simultaneously confirmed its admirable antibacterial efficacy. The recyclability test verified that the synthesized material can be recycled multiple times without a significant loss, which was only a 3 % loss in this case, in photocatalytic activity. The results imply that MnO 2 @MXene has significant promise as an eco-friendly material that is suitable for utilization in photocatalytic and antibacterial applications. [ABSTRACT FROM AUTHOR]

Barium titanate (BT) nanoparticles were prepared using both microwave- and conventional oven-assisted hydrothermal syntheses with varying reaction times (1 h, 3 h, and 6 h). In the case of the conventional oven-assisted hydrothermal syntheses, 16 h, 24 h, 48 h and 72 h reaction times were also studied. Structural and morphological evolution of BT particles were investigated. Microwave-assisted hydrothermal synthesis allowed for the rapid formation of nearly pure barium titanate (BT) phase in just 1 h at 200 °C. On the other hand, using a conventional oven as the heat source required at least 6 h of synthesis to achieve a similar material. When the different BT powders were pelletized and sintered at 1300 °C, ceramics with over 95 % density were obtained. The room-temperature (RT) dielectric permittivity exceeded 1750 for BT particles prepared over 6 h using both heating methods. However, a significant distinction emerged when comparing the piezoelectric coefficient (d 33) values. The BT pellet obtained through the sintering of BT synthesized in the conventional oven for 6 h exhibited a notably higher d 33 value, approximately 171 pC/N, as opposed to the 146 pC/N value observed in BT ceramics resulting from the microwave synthesized powders. Among the ceramic BT variations, the one derived from the best-crystallized tetragonal BT particles (CON_72h) displayed the lowest d 33 value at 79 pC/N. These findings underscore the immense potential of microwave- and conventional oven-assisted hydrothermal syntheses in the sustainable production of BT nanomaterials, which can then be sintered to enable the preparation of ceramics with enhanced ferroelectric and piezoelectric properties. [ABSTRACT FROM AUTHOR]

Developing heterostructure electrocatalysts is a possible route to discovering cost-effective and effectual catalysts for the oxygen evolution reaction. Er 2 O 3 –NiO nanoparticles have been created by successive drop cost method on nickel form. The produced Er 2 O 3 , NiO, and Er 2 O 3 –NiO electrocatalytic performances have been assessed, showing increased OER (185 mV@10 mA/cm2) activities compared to the single component. Furthermore, the three-electrode system (Er 2 O 3 –NiO) has remarkable OER properties, requiring only 1.37 V to reach 10 mA/cm2. Er 2 O 3 –NiO 's synergistic effect, which helps to cause lattice change into the fine structure of the crystal, activates the evolution of surface partial oxygen atoms and enables the lattice oxygen process, is principally responsible for its excellent catalytic performance and stability. This research contributes to a more profound knowledge of the synergistic interaction between various material oxides in heterostructure catalysts. It offers recommendations for future research and development of nanomaterials in sustainable energy conversion technologies. [ABSTRACT FROM AUTHOR]

Carbon dots with a size of 5 nm were synthesized through hydrothermal synthesis by recycling discarded coffee powder. In the Raman signal, the typical D (1364 cm−1) and G (1563 cm−1) bands of Sp 2 carbon were detected, and when excited at 324 nm, a blue, wide-range emission spectrum signal was detected. The synthesized carbon dots were mixed with a solution containing 10 ppm of Pb, Cr, and Cd to be used in the field of detecting metal ions in a solution state. Carbon dots that reacted with metal ions lost their unique blue luminescent color and showed that they could be used as metal ion detection sensors. In addition, spherical particle CaWO 4 :Eu3+ phosphor powder was synthesized and prepared by coprecipitation at room temperature. The synthesized phosphor had a tetragonal structure, and a strong signal from the (112) plane, the main peak, was detected in the XRD pattern, showing excellent crystallinity. When excited at 267 nm, a strong red emission signal of 613 nm was detected, and when the synthesized carbon dots were impregnated and made into a composite, an emission spectrum was observed in a wide range from blue to red, showing white color. This composite was mixed with PDMS to make a flexible sheet and applied to a UV-LED chip, suggesting that it could be used as a white light-emitting device. [ABSTRACT FROM AUTHOR]

This study aims to explore the effects of various hydroxyapatite (HA) doping techniques in depth. For this purpose, two ions with comparable sizes, namely Mn2+ and Cu2+, were selected based on their suitability as dopants for HA in biomedical applications. Moreover, their paramagnetic properties enable sample characterization through electron paramagnetic resonance (EPR) spectroscopy. Two different approaches were employed: (I) ion-substituted α-TCP was used as starting material; (II) foreign ions presented in the solution during the transformation of undoped α-TCP to HA. The foreign ions influenced the hydrolysis process of α-TCP, altering the phase purity and morphology of the products. Doped α-TCP showed a weaker effect, while adding ions to the synthesis solution had substantial impact. Mn-doped α-TCP transformed into plate-like HA particles while Mn2+ ions present in the solution led to the formation of both plate- and rod-shaped particles. In contrast, Cu2+ ions induced the formation of rod-like particles independently of the doping process. Plate-like particles demonstrated higher Brunauer–Emmet–Teller surface area (S BET) than rod-like HA. Each sample exhibited a combination of mesopores and macropores, with mesopores in the range of 15–17 Å being dominant. EPR investigations revealed that Mn2+ and Cu2+ are excellent paramagnetic probes to monitor synthesis reactions of HA and determine the localisation of foreign ions in the material. [ABSTRACT FROM AUTHOR]

The paper proposes an original one-stage method using spark plasma sintering technology (SPS) of manufacturing the ionizing radiation source (IRS) of closed type with a non-dispersible ceramic core based on pollucite obtained using aluminosilicate raw materials saturated (24.3 wt%) with cesium, and doped with 10–40 wt% CsCl. According to the XRD, EDX, AAS and DTA-TG data, optimal conditions for hydrothermal synthesis zeolite NaA were established, the consolidation kinetics and phase transformations into ceramic pollucite under SPS conditions were studied. The ceramics had a relative density of 99.8 % and mechanical strength up to 732 MPa, a low rate of cesium leaching 10−7 g/cm2 day and thermal resistance in air up to 1000 °C. It was confirmed by SEM and EDX that the destruction and deformation of pollucite ceramics in the composition with CsCl and steel at the boundary of their contact in the design of the IRS product was absent and diffusion of cesium outside the ceramics did not occur. The achieved cesium content in the ceramic core of the resulting the ionizing radiation source, which meets high quality and regulatory requirements, is 44.3 wt%. The results of the study may be promising for the manufacture of industrial products. [ABSTRACT FROM AUTHOR]

This study focuses on the hydrothermal synthesis of Bi(Ti x Mn (1-x))O 3 (x = 0.3–0.9) perovskite nanorods on fluorine-doped tin oxide glass substrates and investigates the influence of Ti4+ on their morphological, structural, optical properties, and photocatalytic behavior. The high-resolution XPS spectra results have proved that Ti has been properly substituted into the Bi(Ti x Mn (1-x))O 3 nanorods. The characterization of morphology reveals a decrease in average diameter from 222 to 115 nm as the Ti concentration increases, while the band-gap energy experiences a slight reduction from 3.158 to 3.132 eV. X-ray and Raman spectroscopy analyses of the Bi(Ti x Mn (1-x))O 3 nanorods indicate that Ti ions substitute not only Mn3+ but also Bi3+ ions, leading to structural distortions in the crystal lattice. Moreover, the Bi(Ti x Mn (1-x))O 3 systems demonstrate enhanced photocurrent densities at 1.5 V potential, ranging from 3.19 to 5.54 mA/cm2, as the Ti concentration increases. This enhancement can be attributed to the combined effects of increased surface area, accelerating electron transfer at the interface of the electrode, and decreased optical band-gap energy. It is anticipated that this novel system will pave the way for further advancements in the field of photocatalytic water splitting and solar energy conversion applications. [ABSTRACT FROM AUTHOR]

ZnS hollow nanostructures have attracted much attention due to their special structural advantages and wide range of application. Exploring a convenient method for controllable synthesis of ZnS hollow nanostructures and clarifying the formation mechanisms are important prerequisites for subsequent performance regulation. In this article, we propose a facile method for controllable preparation of homogeneous ZnS hollow nanospheres and clarified the morphological evolution mechanism. ZnS hollow nanospheres with uniform size and good dispersibility were synthesized by adding PVP and excessive thiourea during the hydrothermal process. By systematically studying the influence of experimental parameters on the morphology, the influence diagram of thiourea and PVP on the product morphology was drawn. It is found that excess thiourea is the determining factor for the formation of hollow structures, and PVP plays a key role in the size uniformity and dispersion of the product. The formation mechanism is proposed in which thiourea serves as the reaction source and adsorbed molecule, while PVP serves as a dispersant, both of which worked together to the product morphology and size. The photocatalytic experiments indicate that hollow nanospheres with small size and good dispersibility exhibit a better photocatalytic degradation effect. This work elaborates on how the adsorption of thiourea molecules and the steric hindrance of PVP affect the grain aggregation and growth, which inspirational for the controllable synthesis of the required ZnS nanostructures and further research on their properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Hafnia is a novel material for optoelectronic applications, fabrication methods are focused to obtain hafnium oxide nanomaterials included thin films and nanoparticles. HfO 2 nanoparticles synthesized and studied in this work are crystalline without subsequent heat treatment and were processed by hydrothermal method at 200 °C during 1.3, 2 and 4 h. SEM and TEM analysis revealed the presence of spherical and oval nanoparticles, with range size from 60 to 70 nm and 90–110 nm for spherical and oval nanoparticles, respectively. Raman spectroscopy and X-ray diffraction confirmed that nanoparticles exhibit a stable monoclinic phase. Crystal growth is typical with the presence of the characteristic monoclinic plane (1 ‾ 11) but for reaction times of 2 and 4 h and pH over 12 it turns in the plane (220) which is perpendicular to typical growth. Cathodoluminescence measurements revealed strong blue emission intensity showing a broadband in all visible range and a maximum peak at 460 nm. The presences of V O3 and V O4 in HfO 2 crystalline structure are responsible for this inherent CL emission corroborated by photoluminescence studies. [ABSTRACT FROM AUTHOR]

Stress-induced polarization is deemed to be an important avenue for enhancing photocatalytic activity of photocatalysts, which has drawn considerable attention recently. In this report, we have experimentally and theoretically studied the piezoelectricity-enhanced photocatalytic activity and involved mechanism of Bi 2 MoO 6 nanosheets derived via a hydrothermal synthesis route. Simulated sunlight, ultrasonic and both of them were used to drive the photocatalysis, piezocatalysis and piezo-photocatalysis, respectively. It is demonstrated that, for degradation of various organic dyes and antibiotics, the Bi 2 MoO 6 nanosheets manifest a piezo-photocatalytic activity obviously larger than single photocatalytic activity and piezocatalytic activity with synergistic factor SF > 1. The piezoelectricity in the Bi 2 MoO 6 nanosheets and its enhanced photocatalytic mechanism were elucidated through density functional theory (DFT) calculations combined with finite-element method (FEM) simulations. Additionally, taking the typical organic dye — methylene blue (MB) as an example, we have also investigated the effects of various factors on its degradation efficiency, degradation pathways and mechanism, as well as toxic assessment of degradation by-products. [ABSTRACT FROM AUTHOR]

Bi 2 S 3 has been considered as a promising medium temperature thermoelectric material due to its low thermal conductivity and cost-effective features. However, the intrinsically poor electrical conductivity of Bi 2 S 3 still limits its further thermoelectric applications. In this work, we optimize the thermoelectric performance of Bi 2 S 3 using Cu doping via a facile hydrothermal method combined with spark plasma sintering. A well-tuned carrier concentration of 1.2 × 1019 cm−3 and electrical conductivity of 47 S cm−1 at 523 K was attained, which is attributed to the increased electrons by Cu doping. In addition, the appeared micro-nano pores in both Bi 2 S 3 and Cu doped Bi 2 S 3 samples after spark plasma sintering benefits the reduction of lattice thermal conductivity (κ l). The Bi 1.985 Cu 0.015 S 3 sample exhibited the lowest κ l of 0.405 W m−1 K−1 at 573 K, which is the lowest value as far as we know in the reported Cu doped Bi 2 S 3 materials at the same temperature. Finally, A maximum ZT value of 0.3 at 573 K was achieved in Bi 1.985 Cu 0.015 S 3 sample. This study provides a new strategy to achieve low κ l and high ZT value in Bi 2 S 3 -based thermoelectric materials. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis method to produce calcium hydroxyapatite (HA) of controlled morphology without the use of organic additives is developed in this study. The influence of smaller (Mg2+, Mn2+) and larger (Sr2+, Ba2+) ions on the hydrolysis of α-TCP and crystal growth of HA particles was investigated. It was revealed that both the hydrothermal synthesis conditions (temperature, time) and the nature and concentration of the foreign ion affected the phase purity and morphology of the final products. Of all the ions investigated, Mn2+ had the highest, and Sr2+ had the lowest inhibiting effect on the hydrolysis process of α-TCP. Under certain synthesis conditions, we were able to obtain samples consisting of plate-like or rod-like particles only. The dye adsorption test revealed that the adsorption of plate-like particles for cationic dyes was more efficient, possibly, due to the higher surface area (S BET). Upon normalizing the test results to S BET , it became apparent that the electrostatic attraction between HA particles and dye molecules also impacted the adsorption efficiency. Rod-like particles had a higher ratio of exposed (a,m)- planes and hence lower zeta potential, resulting in increased adsorption of the cationic dye. [ABSTRACT FROM AUTHOR]

In this paper, ZnO particles with the particle size as low as 23 nm were successfully prepared by supercritical hydrothermal synthesis technique. The particle size of nano-ZnO decreased with the increase of temperature and pressure. Nano-ZnO particles in ZnSO 4 system were spherical with smaller particle size. The discrepancy in nano-ZnO produced by different precursor of Zn(NO 3) 2 , Zn(CH 3 COO) 2 or ZnSO 4 is attributed to the anion effects and supersaturation. The particles in the KOH system (29 nm) were smaller than those in the NaOH system (44 nm). For precursor concentration, intermediate Zn(OH) 2 was generated at lower concentration, while Zn 4 SO 4 (OH) 6 ·4H 2 O was produced at higher concentration. For alkali concentration, as the gradual increase of KOH concentration, Zn(OH) 2 began to decrease and gradually transformed into Zn(OH) 3 – and [Zn(OH) 4 ]2−. When the KOH concentration reached a certain value, [Zn(OH) 4 ]2− occupied the dominance in the mixed solution. [ABSTRACT FROM AUTHOR]

Luminescent lanthanide-doped phosphates have never been introduced as potential materials for wood functionalization. Wood–ceramic composites (WCC) may enable the extensive use of wood in construction due to different functionalization. Hence, this work proposes the inorganic GdPO 4 ·H 2 O:Eu3+ compound as an alternative and innovative method to increase wood chemical resistance and confer new optical properties. Scots pine (Pinus sylvestris L.) sapwood – ceramic composite was obtained through in situ hydrothermal synthesis and compared with the untreated sapwood specimens. The enhanced characteristics of the WCC samples were demonstrated using scanning electron microscopy (SEM), x-ray computed micro-tomography (μCT), and thermogravimetric (TG) analysis. Optical properties were determined by luminescence analysis. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2) is a promising material for energy-saving smart windows due to its reversible metal-to-insulator transition near room temperature, concomitantly with a structural phase transition between monoclinic VO 2 (M) phase and rutile VO 2 (R) phase. However, the fact that VO 2 has a complex crystalline phase makes its reliable synthesis an obstacle to its practical application. Machine learning (ML), a specific subset of artificial intelligence, can be utilized to generate virtual representations of experimental conditions and outcomes for the purpose of predicting experiments. Therefore, in the paper, four machine learning models were trained to perform optimization of the VO 2 hydrothermal synthesis. A random forest model achieved a classification accuracy of 87.27%. The synthetic parameter space was explored to filter combinations with a synthetic probability above 90%. Random forest models were used to guide the experimental synthesis, and the obtained products were characterized using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and differential scanning calorimetry. The results showed that phase-pure VO 2 (B) and VO 2 (M) were successfully synthesized, demonstrating the effectiveness of machine learning in optimizing material synthesis, alleviating the stochasticity of material synthesis caused by the control of synthesis conditions, and promoting the application research of VO 2 materials. [ABSTRACT FROM AUTHOR]

The homogeneous and well crystallized rare earth ions RE3+ (RE = Eu, Tb) doped YPO 4 and YPO 4 ·0.8H 2 O nanocrystals (NCs) are synthesized by a simple hydrothermal route. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The results indicate that the pH value of precursor affects the phase composition and surface morphology of the final product. The results of XPS indicate that both Eu2+ and Eu3+ co-exist in YPO 4 NCs, implying that the self-reduction from Eu3+ to Eu2+ takes place with the absence of reducing agents, charge compensation reagents and charge carrier trapping processes. In addition, YPO 4 :Eu and YPO 4 ·0.8H 2 O:Eu samples exhibit strong and bright blue and red emission. According to PL spectroscopy, the blue emission is originated from host lattice and Eu2+ ion luminescence and red emission from Eu3+. YPO 4 :Tb, Eu samples can be effectively excited at 355 nm. An energy transfer phenomenon appears between Tb3+ and Eu3+. It is interesting that by changing the concentration of Tb3+, white phosphor from Y 0.90 PO 4 :0.04 Tb, 0.06Eu NCs are successfully obtained. Moreover, the Y 0.90 PO 4 :0.04 Tb, 0.06Eu has excellent thermal stability. These results indicate that the combination of defect and rare earth luminescence in YPO 4 :Tb, Eu NCs can produce tunable luminescence color, which may have potential applications in fields such as solid-state lighting and field emission displays. [ABSTRACT FROM AUTHOR]

Rare-earth-doped NaYF 4 nanoparticles are considered crucial upconversion luminescent materials with many applications, including anti-counterfeiting printing, biological imaging, and optical information storage. This work presents progress in obtaining hydrophilic pigments based on NaYF 4 :Er,Yb@SiO 2 nanoparticles, and their utilization in water-based ink printing for anti-counterfeiting applications. Coating NaYF 4 :Yb/Er microparticles with SiO 2 shells can provide several benefits for printing purposes, such as improved stability, dispersion, and ease of printing. The hydrophilic core-shell structured β-NaYF 4 :Er, Yb@SiO 2 microparticles were successfully prepared using the hydrothermal synthesis and sol-gel Stober method. The obtained microparticles were characterized by Scanning Electron Microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy. Such characterizations confirm that the Er3+ and Yb3+ ions are incorporated in NaYF 4 cores, the NaYF 4 :Er, Yb cores are in hundreds of nanometer sizes, and the NaYF 4 :Er, Yb microparticles are coated by a silica layer of 50 nm thick. Both NaYF 4 :Er, Yb and NaYF 4 :Er, Yb@SiO 2 behave as up-conversion luminescent microparticles for both green and red emissions. The CIE chromaticity coordinates indicate that both the nanoparticles have their greenish color under excitation at 980 nm. Although decorating the NaYF 4 :Er, Yb nanoparticles with the SiO 2 shell decreases luminescent intensity (by a factor of 2), this step is still necessary to achieve hydrophilic surfaces for preparing water-based printing inks. Using the synthesized NaYF 4 :Er, Yb@SiO 2 as a pigment, a new water-based ink formula was created based on Polyamide as a polymer matrix. The obtained ink is printable on paper and on transparent and flexible Polyethylene substrate. The printed patterns with a height of 2 cm and a width of 2.5 cm were observed clearly under the irradiation of a 980 nm LED. Their durability in terms of sharpness and color was also assessed after six months. [ABSTRACT FROM AUTHOR]

Bismuthate glasses have garnered increasing attention in the fields of optics, packaging, and electronic pastes due to their remarkable stability and high visible light transmission. Nevertheless, high sealing temperature, high expansion coefficient, and poor wettability remain significant challenges in their application. Herein, we report a carefully designed approach that begins with bismuthate glasses of well-defined composition and coats them with various carbon materials to form different C@aminated glass composites by hydrothermal synthesis. This work investigates the effects of different carbon materials on the glass structure and properties, such as melting temperature, crystallinity, wettability, and expansion coefficient, and establishes the redox reaction mechanism involved in glass crystallization formation. Graphene oxide, with its different number of functional distributions and oxygen content, exhibits the largest decrease in softening point and softening-to-melting point temperature difference, the highest increase in wettability, and the greatest reduction in expansion coefficient compared to other carbon materials. In addition, different carbon materials promote a greater variety and strength of crystallization. GO@glass exhibits the most moderate reactivity and generates a significant amount of crystallization at the interface when co-sintered with Si substrates, indicating that the inclusion of crystalline phases can improve the bond strength of the glass. This work provides new insights into designing high-performance bismuthate glasses and promoting their applications. [ABSTRACT FROM AUTHOR]

We investigated the hydrothermal fabrication of n-ZnSnO 3 nanorod array films decorated with various ratios of p-SnO nanoparticles on fluorine-doped tin oxide substrates and their synergistic piezoelectricity-induced applications. We used Mott–Schottky measurements and an energy band diagram to determine the materials' conductivity type. The associated current–voltage characteristics and charge transport behavior were elucidated by investigating Schottky barriers, Schottky emissions, tunneling, depletion regions, and piezopotential-induced energy band bending. The piezoelectric coefficients (d 33) of the ZnSnO 3 nanorod array and the Composite II film were measured to be approximately 15.4 and 17.3 p.m.·V−1, respectively. Theoretical simulation of piezopotential distributions revealed that compressive deformation was predominant for samples under stress. The Composite II film exhibited reliable piezophotodegradation activity for rhodamine B (RhB) solutions, with a degradation rate constant of approximately 1.2 × 10−2 min−1 under visible-light irradiation, approximately 2.5 times that of the individual ZnSnO 3 film, partially due to intimate contact between the two constitutive components, high electrochemical surface areas, and facilitated charge carrier transport resulting from piezopotential-induced energy band bending. This study revealed the positive effect of piezoelectricity on photodegradation and established a paradigm to allow wide-bandgap materials to function in the visible-light range through a p–n junction. [ABSTRACT FROM AUTHOR]

In this work, BaZr 0.85 Y 0.15 O 3-δ was elaborated by a continuous hydrothermal process in supercritical conditions (410 °C/30.0 MPa). X-Ray diffraction, Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy analysis allowed to propose a description of the formation mechanism for this oxide in supercritical water. This mechanism consists in the precipitation of core-shell nanoparticles in which, the core is a Ba-deficient perovskite and the shell an oxyhydroxide species of Y and Zr. Then, Ba2+, Zr4+ and Y3+ are incorporated in the perovskite from the solution and from the shell. After an annealing treatment at 1000 °C for 1 h to homogenize the composition, the powder was pressed into a pellet and sintered at 1550 °C for 5 h to analyze its electrochemical properties. The total conductivity of this oxide is 2.5 × 10-3 S cm-1 at 600 °C in wet H 2 (3% H 2 O). Furthermore, electrochemical impedance spectroscopy measurements showed that its conduction is mainly protonic at a temperature lower than 575 °C. [ABSTRACT FROM AUTHOR]

The ZnSe/ZnO heterostructures were synthesized with the microwave-assisted hydrothermal method, using zinc acetate and zinc nitrate as a source of Zn2+ ions. Materials were characterized by X-ray diffraction (XRD), X-ray photoemitted electron spectroscopy (XPS), Raman spectroscopy, and scanning electron microscopy (SEM). The incorporation of ZnSe into the ZnO matrix produced changes both in the size of the ZnO crystallites and in the lattice parameters. Optical and texture analyses revealed that ZnSe particles cause a decrease in gap energy and a greater than 90% increase in the specific surface area of ZnSe/ZnO heterostructures compared to bare ZnO particles. ZnSe/ZnO heterostructures synthesized using zinc acetate as a Zn ion source exhibited better photocatalytic performance in visible light compared to pure ZnO. [ABSTRACT FROM AUTHOR]

The Ce 2 Sn 2 O 7 nanoparticles were successfully synthesized using a simple hydrothermal method. The crystal structure, morphology, and optical property of Ce 2 Sn 2 O 7 nanoparticles were analyzed by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy and UV–visible diffuse reflectance spectroscopy. The nanomaterial was first applied to ultrasonic catalytic degradation. The sonocatalytic activity of Ce 2 Sn 2 O 7 nanoparticles was evaluated at room temperature and in the dark by using the Methyl Orange (MO) as the simulated contaminant. The effects of ultrasonic output power, Ce 2 Sn 2 O 7 addition amount, initial concentration of pollutants, pH of solution, types of organic dyes and other factors on the catalytic degradation efficiency were investigated. The experiment results show that the ultrasonic catalytic degradation reaction of MO by the Ce 2 Sn 2 O 7 nanoparticles basically follows the pseudo first-order kinetic model. Under the best conditions, the ultrasonic catalytic degradation rate of Methyl Orange reaches 97.8%, and the degradation rate can still reach 82.6% after four cycles of experiments. These results indicate that Ce 2 Sn 2 O 7 nanoparticles can be used as acoustic catalyst for the purification of organic wastewater, which has a good application prospect. [ABSTRACT FROM AUTHOR]

Layered-structure V 2 O 5 has attracted extensive research attention as an ideal electrode material for lithium batteries and gas sensors, among others. In this study, we investigated the effects of Li+ and Eu3+ single- and co-doping on the electronic structure, optical properties, and pollutant-photodegradation efficiency of V 2 O 5. All the samples were fabricated by a simple one-step hydrothermal method using NH 4 VO 3 and phthalic acid as precursors. Pure and Eu3+-doped V 2 O 5 developed into short, thick nanorods, while, Li+/Eu3+-co-doped V 2 O 5 crystallized into ultralong nanowires. Furthermore, Li+ and Eu3+ doping significantly increased the ability of V 2 O 5 to photodegrade Rhodamine B in solution. In order to elucidate the mechanism of this photochemical enhancement, the multivalence of V, charge dispersion characteristics, luminescence, and carrier lifetime were measured. The improved photocatalysis of Li+/Eu3+-co-doped V 2 O 5 was found to be related to its increased specific surface area, multivalent V4+/5+ ions, prolonged charge lifetime, and accelerated charge dispersion. Experimental results showed that Eu3+ and Li + ions are present in the interlayers of V 4 O 5 as pillars. Thus, co-doping represents a viable strategy to improve the photochemical properties of layered V 2 O 5. [ABSTRACT FROM AUTHOR]

By twice pre-milling γ-Al 2 O 3 in absolute ethyl alcohol plus in glucose aqueous solution, γ-Al 2 O 3 was first coated by carbon via hydrothermal treatment technique. Then, at a fast heating speed of 50 °C/min, nano-sized pure AlN powders were synthesized through carbothermal reduction and nitridation (CRN) at 1550–1600 °C for 60–120 min in N 2. The pre-milling in absolute ethyl alcohol effectively broke the initial aggregation of γ-Al 2 O 3 , and the subsequent milling in glucose aqueous solution led to well contact between γ-Al 2 O 3 and glucose, which contributed to the formation of intact carbon coating on the surface of γ-Al 2 O 3 during hydrothermal treatment. The coated carbon served as one reactant and inhibitor of particle aggregation for CRN, which also led to retention of γ-Al 2 O 3 and its morphology during heating with the help of high heating speed. As a result, fine AlN of ∼100 nm was directly formed by nitridation of γ-Al 2 O 3. The synthesis mechanism of nano-sized AlN powder by the carbon coated Al 2 O 3 /C precursor was discussed. [ABSTRACT FROM AUTHOR]

Multilayer ceramic capacitor (MLCC) is a key passive component that maintains stable current flow and controls electromagnetic interference between components in the safety and protective electronics in automobiles. Defects that exist in BaTiO 3 manufactured by hydrothermal synthesis make it unsuitable for use as raw material for the production of MLCCs for the automotive industry, where reliability is important. In this study, a solid-state synthetic seed process for the development of solid-state BaTiO 3 powder with high crystallinity is demonstrated. In this process, before initiation of the solid-state synthesis of BaCO 3 and TiO 2 , a fine nucleation site to synthesize BaTiO 3 dielectric ceramic powder with uniform composition, high crystallinity, and fine size was formed. The addition of 25 wt% of 50 nm-sized BaTiO 3 seeds to induce homogeneous synthesis between precursors facilitated low-temperature solid-state synthesis and BaTiO 3 synthesis with improved crystallinity. Particularly, the homogeneous nucleation was effective in facilitating the atomization of grains after sintering, and thus the dielectric properties were greatly improved. The results of this study establish the effectiveness of the solid-state synthesis process in improving the properties of BaTiO 3 dielectric powder for use in the manufacture of MLCCs. [ABSTRACT FROM AUTHOR]

Orthorhombic Sc 2 Mo 3 O 12 samples have been synthesized using ethylene glycol (EG)-assisted hydrothermal reaction. The influences of hydrothermal temperature, hydrothermal time and additive content of EG on the preparation and negative thermal expansion (NTE) behavior of Sc 2 Mo 3 O 12 samples were characterized using XRD, SEM, HRTEM, EDX, TMA and HTXRD. Results indicate that flower-like Sc 2 Mo 3 O 12 with a uniform particle size of 1–2 μm can be synthesized at 120 °C for 2 h by adding 60 ml EG. Hydrothermal temperature, time and additive content of EG have strong influences on the growth and morphology of the Sc 2 Mo 3 O 12. The average coefficients of thermal expansion (CTEs) of the Sc 2 Mo 3 O 12 prepared at 120 °C for 2 h and 200 °C for 24 h are tested to be −6.94 × 10−6 °C−1 and -7.18 × 10−6 °C−1 in 25–700 °C using TMA. HTXRD results indicate that the flower-like Sc 2 Mo 3 O 12 exhibits anisotropic NTE, and the corresponding CTEs along the a , b and c axes are −6.73 × 10−6 °C−1, 4.98 × 10−6 °C−1 and -4.78 × 10−6 °C−1 in 25–700 °C, respectively, and the corresponding linear CTE is −2.21 × 10−6 °C−1. [ABSTRACT FROM AUTHOR]

We have studied the enhanced light harvesting capacity and reduced recombination rate of TiO 2 thin film by composite with Carbon Quantum Dots (CQDs). The CQD/TiO 2 film was synthesized using facile, and low-temperature hydrothermal synthesis approach using CQD derived from sugarcane juice and ethanol. The prepared TiO 2 and CQD/TiO 2 composite thin films were characterized for structural, functional, optical, morphological and elemental compositions analysis using, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, UV–Vis Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and X-ray Photoelectron Spectroscopy (XPS). The optical band gap of CQD/TiO 2 was calculated to be 2.87 eV fall under the visible region favorable for photocatalytic activity under sunlight. The Methylene Blue (MB) dye degradation studies of TiO 2 and CQD/TiO 2 thin films were carried out under the noon sunlight radiation which showed 78% and 82.6% degradation with good reusability. Therefore, this CQD/TiO 2 composite thin film can be a promising candidate for industrial dye effluent treatment. [Display omitted] [ABSTRACT FROM AUTHOR]