Low-temperature Synthesis Method Research Articles

High-Entropy Alloy Al0.2Co1.5CrFeNi1.5Ti0.5 Prepared from High-Entropy Oxide (Al0.2Co1.5CrFeNi1.5Ti0.5)3O4 by a Deoxidation Process via a CaH2-Assisted Molten Salt Method

High-entropy alloys (HEAs) have attracted a great deal of research interest these days because of their attractive properties. Low-temperature chemical synthesis methods are being developed to obtain nanoscale HEAs with low energy consumption. In this study, we prepared HEA Al0.2Co1.5CrFeNi1.5Ti0.5 nanoparticles from high-entropy oxide (HEO) (Al0.2Co1.5CrFeNi1.5Ti0.5)3O4 by a deoxidation process via a CaH2-assisted molten salt method at 600 °C. X-ray diffraction measurements demonstrated that the oxide precursor and the reduced product have single-phases of spinel structure and face-centered cubic structures, indicating the formation of HEO and HEA, respectively. The HEA nanoparticles exhibited superior catalytic performance in the liquid-phase hydrogenation of p-nitrophenol at room temperature with little leaching of the component elements. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDX) exhibited a good distribution of constituent elements over the HEA nanoparticles in a micro-sized range. However, transmission electron microscopy (TEM) with EDX revealed a slight deviation of elemental distributions of Al and Ti from those of Co, Cr, Fe, and Ni in a nano-sized range, probably due to the incomplete reduction of aluminum and titanium oxides. The elemental homogeneity in the HEA nanoparticles could be improved by taking advantage of the HEO precursor with homogeneous elemental distributions, but the experimental results suggested the importance of the total reduction of oxide precursors to prepare homogeneous HEAs from HEOs.

Scorodite synthesis process using solid iron oxides

The immobilization of arsenic in the form of scorodite (FeAsO4·2H2O), which has excellent chemical stability, is attracting attention as a method for treating wastewater containing high concentrations of arsenic generated at nonferrous metal smelting plants. Scorodite, with its low solubility and high arsenic content per volume, is expected to be an environmentally friendly arsenic fixation method suitable for final disposal. Various scorodite synthesis methods have been studied. The first synthesis method proposed is the hydrothermal method using an autoclave to synthesize highly crystalline scorodite. Although the hydrothermal method is capable of synthesizing scorodite with good crystallinity, from an economic point of view, scorodite synthesis under ambient pressure and at low temperatures is more attractive. As a low-temperature scorodite synthesis method under atmospheric pressure, the oxidation of Fe(II) process by O2 bubbling was proposed. In this method, ferrous sulfate is added to an arsenic-containing solution as a Fe ion source, and in situ oxidation of Fe(II) by O2 or air bubbling to form scorodite with good crystallinity. In addition to temperature, other conditions, pH, Fe/As ratio, and reaction time have been reported to affect scorodite crystallization. Recently, scorodite synthesis using solid iron oxide as the Fe source for scorodite synthesis, instead of aqueous Fe salt solutions, has attracted much attention. In this presentation, we will report on the investigation of reaction parameters, such as the type of iron oxide and reaction temperature, for the scorodite synthesis using solid iron oxide.

Atomic layer deposition of SnS2 film on a precursor pre-treated substrate

Two-dimensional (2D) materials are attracting attention because of their outstanding physical, chemical, and electrical properties for applications of various future devices such as back-end-of-line field effect transistor (BEOL FET). Among many 2D materials, tin disulfide (SnS2) material is advantageous for low temperature process due to low melting point that can be used for flexible devices and back-end-of-line (BEOL) devices that require low processing temperature. However, low temperature synthesis method has a poor crystallinity for applying to various semiconductor industries. Hence, many studies of improving crystallinity of tin disulfide film are studied for enhancing the quality of film. In this work, we propose a precursor multi-dosing method before deposition of SnS2. This precursor pre-treatment was conducted by atomic layer deposition cycles for more adsorption of precursors to the substrate before deposition. The film quality was analyzed by x-ray diffraction, Raman, transmission electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. As a result, more adsorbates by precursor pre-treatment induce higher growth rate and better crystallinity of film.

Novel synthetic approaches and morphological design of perovskite-type oxynitrides in powder and ceramic form

Perovskite-type oxynitrides are a new class of inorganic materials that have potential applications as photocatalysts, inorganic pigments and dielectrics. Design of the morphology in conjunction with new synthesis methods is essential for their practical use. In this review, we present the formation of fine particles via a low temperature and ammonia-free synthesis method, the morphology of the oxynitride perovskites obtained using metal carbodiimide, and the toughness of the sintered ceramics in relation to their microstructure.

Synergistic electronic structure modulation in single-atomic Ni sites dispersed on Ni nanoparticles encapsulated in N-rich carbon nanotubes synthesized at low temperature for efficient CO2 electrolysis

Ni, N-doped carbon materials (Ni–N–C) are prosperous candidates for the electrochemical CO2 reduction reaction (CO2RR) due to their outstanding activity and selectivity. However, the role of the coexisting uncoordinated N-doped sites and Ni nanoparticles (Ni-NPs) in overall CO2RR has been overlooked in prior studies. To address this gap, a low temperature synthesis method developed for Ni-NP-encapsulated Ni–N–C nanotube (Ni-NCNT) catalysts with atomically dispersed Ni–N4 and abundant uncoordinated N-doped sites, where Ni-NPs increase the electron density on Ni–N–C nanotube through carbon network and synergistically enhances the CO2RR activity. The systematic analysis reveals the cooperative role of Ni-NPs and uncoordinated N-doped sites in altering the electronic structure of Ni–N4 sites. The results of control experimental studies confirm the synergistic interaction of uncoordinated N-doped sites boost the CO2RR activity of Ni–N4 sites. Additionally, density functional theory calculations show that the strong interaction between the Ni-NPs and Ni–N–C did not affect the electronic structures of the Ni–N4 centers, but rather alter the electronic structure of uncoordinated pyridinic-N sites. This variation led to decreased the energy barriers of rate-limiting steps of COOH* formation on Ni–N4 and N-doped sites, resulting in excellent CO2RR performance.

Nanoengineered parallelogram-NiFe2O4/rGO nanocomposite-based biosensing interface for highly efficient electrochemical detection of neurodegenerative disorders via dopamine monitoring

A low-temperature hydrothermal method for synthesis of unique parallelogram morphology based NiFe2O4 and NiFe2O4/reduced graphene oxide nanocomposite for fabricating biosensors for dopamine monitoring.

Low-temperature synthesis of Nb-doped and Mn-doped SrTiO3 with easily controllable particle size

Heterovalently doped perovskite-type oxides are used in various electronic applications. Herein, we propose a low-temperature synthesis method for Nb- and Mn-doped SrTiO3 particles with a wide range of particle sizes that is conducted at temperatures close to room temperature (RT). The cation-doped SrTiO3 particles were synthesized under diverse solution conditions by varying the aging temperature, aging period, viscosity of solvents, and OH− concentration using facile and low-cost methods. The particle sizes were simply controlled by changing the ratio of H2O/ethanol solvents owing to their difference in viscosity at low temperatures. The uniformity of the particle sizes was significantly improved via a two-step aging process, that is, heating at a low temperature followed by RT aging. Additionally, the OH− concentration in aqueous solution had considerable impact on the rate of crystal growth, affecting particle size as well as morphology. This study demonstrates the feasibility for the low-temperature synthesis of cation-doped perovskite-type materials.

Black Phosphorus-Based ZnO-Ag Nanocomposite for Antibacterial Activity against Tigecycline-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a critically hard-to-treat gram-negative pathogen responsible for a range of infectious diseases. Tigecycline is a last-resort antibiotic for A. baumannii infection; however, tigecycline-resistant (TIG-R) A. baumannii has been increasingly reported. Therefore, new strategies must be developed to treat these detrimental infections. Nanoantibiotics composed of two-dimensional (2D) black phosphorus (BP) and its derived nanocomposites have emerged as excellent alternatives to current antibiotics. However, the development of unique materials to target specific pathogens is challenging. Here, we report the preparation of a BP-based ZnO-Ag (ZPBA) nanocomposite. A low-temperature solution synthesis method was used to prepare ZnO and Ag nanoparticles immobilized on BP nanosheets. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to characterize the ZPBA nanocomposite. The antibacterial activity of ZPBA nanocomposite was assessed by determining its minimum inhibitory concentration against type (ATCC 19606, ATCC 15150) and TIG-R (ATCC 19606-R) A. baumannii strains. From the assays, ZPBA showed superior activity against TIG-R A. baumannii strain with MIC of 12.5 µg·mL−1 compared to all other prepared samples. Finally, the combination of bacterial membrane disruption and ROS generation was demonstrated to be a potential antibacterial mechanism of ZPBA. Our results show that ZPBA could be a potential nanoantibiotic platform for eradicating TIG-R A. baumannii.

Porous Mn-doped Fe3O4 as lithium-ion battery anode via low-temperature combustion synthesis

The preparation of Mn-doped Fe3O4 was carried out using the low-temperature combustion synthesis (LCS) method through the addition of Mn2+ to the ferric nitrate-glycine system. Here, we investigate the mechanism of the redox reaction involving Fe3+ and Mn2+ ions, and the results reveal that for the synthesis of porous Mn-doped Fe3O4, the presence of Mn2+ in the raw material is necessary. The carbon source, such as ethylene glycol, glucose, and polyethylene glycol-4000, serves as both reducing and complexing agent, leading to the formation of more pores during the combustion reaction. Increased specific surface area of combustion products. By conducting a LCS reaction in a solution with added ethylene glycol, Mn-doped Fe3O4 was obtained for lithium ions batteries as anode material, at current density of 5 A g−1, it demonstrates an impressive capacity retention rate of 90% with a high capacity of 452.5 mA h g−1 after 650 cycles. Similarly, Mn-doped Fe3O4 obtained with the addition of polyethylene glycol shows a capacity retention rate of 89.7% after 1500 cycles. Our findings provide a new and innovative method for the preparation of manganese ferrites with a porous structure and a new research approach for developing metal oxide anode materials.

Synthesis of water-stable and highly luminescent graphite quantum dots

Highly stable and environmentally friendly nitrogen-doped graphite quantum dots consisting of ∼12 layers of graphene, average diameter of ∼7.3 nm, prepared by atmospheric pressure microplasma are reported to have blue emission due to surface states created by nitrogen doping (9 atomic%) and reaction with oxygen. The low-temperature synthesis method requires simple precursors in water, with no annealing or filtration, producing crystalline disc-shaped quantum dots with ∼68% photoluminescence emission quantum yield at 420 nm excitation and that have shown stability for more than one month after the synthesis. The nitrogen doping in the quantum dots mainly occurs in graphitic core as substituted type of doping (63–67 atomic%) and the amount of doping is sufficient to create emissive states without impacting the core structure. The optical and chemical properties do not undergo serious retardation even with re-dispersion suggesting easy applicability for cellular imaging or optoelectronics.

Structural, morphological, dielectric properties, impedance spectroscopy and electrical modulus of sintered Al6Si2O13–Mg2Al4Si5O18 composite for electronic applications

In this study, the sol-gel method of low-temperature synthesis was utilized to create mullite/cordierite precursor powder. The materials (TEOS) Si(C2H5O)4, Al(NO3)3.9H2O and Mg(NO3)2 were utilized as source of SiO2, Al2O3, and MgO oxides respectively in order to create mullite/cordierite precursor gel with various concentrations and designations (MC00, MC10, MC20, MC30, MC40, and MC50). Crystalline phases were seen and described using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). After the powder was formed at 1600 °C for an hour, its sintering was looked at. For all mixes, as the cordierite concentration rises, the bulk density rises and the open porosity decreases. The existence of a vitreous phase may be the cause of the rise in bulk density and reduction in open porosity seen with rising temperatures.The dielectric characteristics of the samples have been examined at room temperature; the relative dielectric constant (εr), loss tangent (tanδ), and dielectric characteristics were assessed at frequencies of 0.1 Hz, 1, 10, 100, and 1000 kHz. At 1 kHz, the relative dielectric constant values are closest to those of mullite (εr = ∼5 to ∼ 6), and c at 1 kHz. On the other hand, the lowest dielectric losses were observed (tanδ from ∼0.06 to ∼ 0.04). The Electrical properties, electrical resistivity, AC conductivity, impedance spectroscopy, electrical modulus, and the relative quality factor (QF) of pure mullite and mullite/cordierite composite sintered at 1600 °C for 1 h (MCyy) samples were investigated as a function of cordierite content at varied frequencies (0.01 Hz, 1 kHz, 100 kHz, and 1000 kHz). The hardness (HV) and coefficient of thermal expansion (CTE) of the composite material that underwent sintering at a temperature of 1600 °C were determined by the use of a hardness tester and a dilatometer, respectively. The rise in temperature, coupled with an equal quantity of cordierite, resulted in an elevation of the apparent density and a reduction in the open porosity. In the case of the specimen subjected to sintering at a temperature of 1600 °C, the introduction of cordierite content in the range of 0–40% resulted in an observed rise in HV value from 9.15 to 12.99 GPa. However, a further increase in cordierite content to 50% led to a decrease in HV value to 10.99 GPa. Nevertheless, the CTE value throughout the temperature range of 50–1200 °C exhibited a consistent decline, ranging from 5.37 × 10−6 to 2.32 × 10−6 K−1. Notably, the composite material consisting of 50 wt% cordierite had elevated HV and the most minimal CTE value.

Pd-Enriched-Core/Pt-Enriched-Shell High-Entropy Alloys Nanoparticles with a Face-Centred Cubic Structure for C1 and C2 Alcohol Oxidation.

Recently, high-entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi-step reactions. Herein, a facile low-temperature synthesis method at atmospheric pressure is employed to synthesize Pd-enriched-HEA-core and Pt-enriched-HEA-shell NPs with a single phase of face-centred cubic structure for promoting the oxidation of C1 and C2 alcohols. Interestingly, the lattice of both Pd-enriched-HEA-core and Pt-enriched-HEA-shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. Strikingly, the as-made PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Especially, the specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA/cm2 (2874 mA mg(Pd+Pt)-1), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Combined with high-entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi-step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.

Sol-Gel Synthesis of Translucent and Persistent Luminescent SiO2@ SrAl2O4 Eu, Dy, B Materials.

This publication offers an economically promising method of persistent luminescent silicate glass synthesis that does not involve high temperatures or ready-made (separately synthesized) PeL particles. In this study, we demonstrate the formation of SrAl2O4 doped with Eu, Dy, and B in a SiO2 glass structure using the one-pot low-temperature sol-gel synthesis method. By varying the synthesis conditions, we can use water-soluble precursors (e.g., nitrates) and a dilute aqueous solution of rare-earth (RE) nitrates as starting materials for SrAl2O4 synthesis, which can be formed during the sol-gel process at relatively low sintering temperatures (600 °C). As a result, translucent, persistently luminescent glass is obtained. The glass shows the typical Eu2+ luminescence and the characteristic afterglow. The afterglow duration is about 20 s. It is concluded that the slow drying procedure (2 weeks) is optimal for these samples to sufficiently get rid of the excess water (mainlyOH groups) and solvent molecules that can influence the strontium aluminate luminescence properties and have a pernicious effect on the afterglow. It can also be concluded that boron is playing a crucial role in the formation of trapping centers needed for PeL processes in the PeL silicate glass.

Seed-mediated Generation of Epsilon Iron Oxide Nanocrystals at 300 °C

Epsilon iron oxide (ε-Fe2O3) is a material with a high coercive field. Herein we report seed-mediated generation of ε-Fe2O3. The generation of ε-Fe2O3 can be accelerated with the calcination of Prussian blue (PB) by a proliferative reaction, using ε-Fe2O3 nanoparticles as a seed. The present synthetic reaction occurs at a temperature below 300 °C, suggesting this is a promising method for low-temperature synthesis of ε-Fe2O3.

Enhanced thermoelectric properties of n-type CoSb3-based composites by incorporating In particles

Thermoelectric devices that consist of N-and P-type TE legs in series have been well known and applied owing to the ability that could convert waste heat into electric energy. Among them, skutterudite materials have been frequently studied as the main object because they are environmentally friendly and inexpensive. In this study, N-type CoSb3-based materials were synthesized using a low-temperature synthesis method and spark plasma sintering. Those thermoelectric matrix that incorporated Indium (In) particles were prepared via manual grinding method. The thermoelectric properties, microstructures, and morphologies of the pure and In-doped Co0.91Ni0.09Sb3 samples were systematically evaluated. A maximum power factor value of 3642.3 μW/mK2 was obtained at 723 K for a Co0.91Ni0.09Sb3/1 wt%In sample and the highest figure of merit value of 1.01 was attained for a Co0.91Ni0.09Sb3/2 wt%In sample. These results indicate that Indium particles as secondary phase can improve the thermoelectric performance of N-type CoSb3-based materials.

Amorphous MnO2-Modified FeOOH Ternary Composite with High Pseudocapacitance As Anode for Lithium-Ion Batteries

The development of high-capacity anodes that are stable at high rates is of immediate interest as a potential alternative to the commercial graphite anode in lithium-ion batteries (LIBs). Conversion-based transition metal oxides, known for their high theoretical capacities, have been extensively studied in this regard. In this work, a ternary FeOOH-rGO-MnO2 composite has been suitably designed to address the limitations of the bare FeOOH anode arising from poor conductivity and volume expansion. A simple low-temperature synthesis method was employed to obtain a uniform distribution of FeOOH nanorods over the rGO matrix, which was further modified with a buffer layer of amorphous MnO2 nanosheets. While cycling at high rates, the modified composite anode delivered capacities of 956, 842, and 688 mAh g–1 at 1, 2, and 5 A g–1, respectively, for 200 cycles along with a cycling stability of 900 mAh g–1 at 1 A g–1 for 100 cycles. Various electrochemical techniques were used to analyze the superior performance of the ternary composite anode. The carbon matrix effectively provides favorable pathways for electron conduction and aids in the stable SEI formation, while the amorphous MnO2 sustains the structural integrity of the electrode by controlling volume expansion. Further, the exceptional stability of the anode at high rates was attributed to the marked increase in capacitive contribution in the FeOOH-rGO-MnO2 ternary composite anode, paving the way for faster electrode kinetics.

A monolithic gold nanoparticle@metal-organic framework composite as CO2 photoreduction catalyst

The application of metal-organic frameworks (MOFs), especially MOF composites, has been hindered by a lack of method to process powders into useable forms. To address this challenge, we report here a low temperature synthesis method that enables direct formation of a densified monolithic MOF composite, i.e. Au@ZIF-67. The monolithic composite contains Au nanoparticles (Au NPs) that are well-dispersed and encapsulated within ZIF-67 particles. It exhibits high surface area, bulk density, and mechanical robustness as observed in monolithic ZIF-67, while retaining the localized surface plasmonic resonance (LSPR) characteristic of Au NPs. Benefiting from this unique combination, the monolithic Au@ZIF-67 samples display an enhanced CO2 photoreduction performance under visible light—with the best-performing Au@ZIF-67 sample showing a volumetric CO production rate 1.5 and 3 times higher compared to the pristine monolithic ZIF-67 and ZIF-67 powder, respectively.

Enhanced dual-wavelength up-conversion luminescence and temperature sensitivity of NaYF4:Yb3+, Er3+ phosphors by Bi3+ introducing

The up-conversion composite fluoride phosphor BixNayYzF3x + y+3z +3z+3m+3n: Er3+m, Yb3+n were synthesized using the optimized low-temperature combustion synthesis (LCS) method. The optimal formula was determined by step-by-step orthogonal experiments. The effects of the introduction of Bi3+ ions on phase formation and fluorescence intensity were systematically studied. The results indicate that introducing 10 mol% Bi3+ ions can substantially strengthen the dual-wavelength up-conversion fluorescence intensity of the sample. Then the temperature sensitivity of the sample is calculated, indicating that the sample has good temperature sensitivity and can be used as an effective material for temperature sensors. X-ray diffraction and scanning electron microscopy (SEM) were used to analyze the phase composition and morphology of the phosphor. The product exhibits characteristic emission of Er3+ ions under the excitation of 1550 nm ＆ 980 nm dual-wavelength, and its luminescence mechanism was studied. This work provides new ideas for studying photothermal dual response up-conversion fluoride phosphors under excitation at 1550 nm & 980 nm.

Black phosphorus-based CuS nanoplatform: Near-infrared-responsive and reactive oxygen species-generating agent against environmental bacterial pathogens

Over the last few years, the two-dimensional (2D) material black phosphorus (BP) has been highlighted for its potential in various biomedical applications, owing to its excellent physical and chemical properties. Nevertheless, the synergistic photothermal–antibacterial effects of BP when combined with other semiconducting materials against pathogenic bacteria have rarely been explored. In this study, the synergistic photothermal–antibacterial activity of a BP-based CuS (CB) nanoplatform against environmental bacterial pathogens was evaluated. A low-temperature solution synthesis method was utilized to prepare CuS nanoparticles that were immobilized onto BP nanosheets. The resulting CB nanocomposite was characterized using X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The antibacterial activity of the samples was evaluated by determining their minimum inhibitory concentration and bactericidal activity following near-infrared irradiation. The results revealed that CB nanocomposites showed higher antibacterial activity than other samples owing to the high photothermal conversion efficiency. In addition, the plausible antibacterial mechanisms, such as the formation of reactive oxygen species and bacterial membrane disruption, were evaluated. The prepared 2D semiconductor exhibiting synergistic photothermal–antibacterial activity will serve as a good nanoplatform against multidrug-resistant pathogens shed in the environment.

High surface area ZnO/rGO aerogel for sensitive and selective NO2 detection at room temperature

Accurate and convenient detection of nitrogen dioxide (NO2) in the air, which is harmful to human health, is vital. However, it is difficult for many NO2 detection devices to achieve high sensitivity at room temperature. In this work, we synthesized zeolite-imidazolate-frameworks-8 (ZIF-8) nanoparticles and zinc oxide/reduced graphene oxide (ZnO/rGO) aerogel by low-temperature synthesis and sol-gel method. The aerogel composite materials were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM), Brunaue-Emmette-Teller (BET), and Raman spectroscopy. The gas-sensitive element prepared by the material with the mass ratio ZIF-8 to rGO is 5:1 possesses excellent selectivity and higher sensitivity (3.21) to 100 ppm NO2 at room temperature. Reduced graphene oxide (rGO) provides more gas transmission and diffusion channels for improving sensitivity because of a three-dimensional porous structure. When NO2 is exposed, electrons transfer into p-n heterostructure formed by rGO and ZnO composite to achieve the purpose of sense. In this study, the material preparation method is relatively simple and efficient, which is of profound significance to accurately detect the variation of NO2 concentration in air at room temperature.