Hydrothermal Method Research Articles

Eco-friendly preparation of nickel cobaltite as an electrode material in sustainable energy storage devices

In this study, urchin and tremella-like NiCo2O4 was synthesised by adopting a facile hydrothermal method using green solvents (water and ethanol). Using different ratios and pure forms of green solvents has a direct impact on materials synthesised. Ethanol based NiCo2O4 (NCO-E) illustrated tremella like microspheres with a specific surface area of 260.8 m2 g−1. The electrochemical performance confirmed that the NCO-E has a maximum specific capacitance of 2271 F g−1 at a current density of 1 A g−1. Further, as-fabricated NCO-E//AC-ASC device delivers a Cs value of 96.6 F g−1 at 1 A g−1 and a cyclic stability of 99.68 % over 5000 cycles. The device exhibited a high energy density of 30.19 Wh kg−1 at a power density of 749.48 W kg−1 and a high power density of 7542.61 W kg−1 at energy density 18.43 Wh kg−1 owing to the working electrode's effective electrochemical usage and excellent ion transfer mechanism.

A triple-benefit strategy of microstructure, electronic property and active site modulation on ZnIn2S4 photocatalyst by Sn atom doping

To overcome the high cost and complex preparation of cocatalysts in photocatalytic H₂ production, this study pioneers a triple-benefit strategy in visible-light-absorbing semiconductors through microstructure optimization, electronic property modulation, and active site modification in two-dimensional (2D) hexagonal ZnIn₂S₄ (ZIS) via Sn atom doping. Facilely synthesized through a one-step hydrothermal method without surfactants, 4–6 nm thick Sn-doped ZIS nanosheets exhibit reduced charge recombination by preventing excessive self-assembly and aggregation. Density Functional Theory (DFT) and X-ray Absorption Fine Structure (XAFS) confirm Sn’s substitution for Zn on (001) surface, shifting the Fermi level into the conduction band to facilitate electron migration and charge separation. This adjustment also modulates the electronic properties of adjacent S atoms, triggering the inert basal plane for an enhanced H₂ evolution reaction kinetics. Consequently, Sn-ZIS achieves a H₂ evolution rate of 62.18 μmol h−1 under visible light, significantly outperforming pure ZIS and Pt@ZIS by 6.7 and 3.5 times, respectively.

BiVO4-Driven photocatalytic degradation of pharmaceutical in Slurry Bubble Column Reactor: Influencing factors and toxicological profiling

As the pursuit for sustainable and effective solutions to address environmental pollution intensifies, a comprehensive approach in photocatalysis has become a subject of increasing interest. In this study, BiVO4 photocatalyst synthesized through a pH-controlled hydrothermal method was used for the degradation of tetracycline (TET), a prevalent pharmaceutical pollutant. Optimal conditions, particularly a pH of 9 and enriched dissolved oxygen (DO), significantly improve TET removal, achieving a 96 % degradation efficiency with a rate constant of k = 0.1069 min−1. The investigation revealed that the degradation predominantly involves the generation of reactive oxygen species (ROS), notably O2•−, which play a crucial role in the degradation of TET. Using the “ecological structure–activity relationships” (ECOSAR) program, the toxicity of the intermediates was assessed, highlighting the environmental implications of the photocatalytic process. In addressing the scalability for industrial applications, a Slurry Bubble Column Reactor (SBCR) was employed, and separation-stability tests of the photocatalyst were conducted. These tests confirmed the photocatalyst’s long-term effectiveness and stability, underscoring its potential for repeated use in large-scale applications. This comprehensive research not only underscores the potential of BiVO4 in removing environmental contaminants but also provides vital insights into ecological safety.

Rare earth induced lattice distortion of Bi2WO6 to effectively improve photocatalytic performance: experimental and DFT calculations

The excellent visible light photocatalytic activity of bismuth-based photocatalysts has attracted the interest of many scholars at home and abroad. In this paper, rare earth (Sm, La, Ce, Eu) doped Bi2WO6 photocatalysts were prepared by a one-step hydrothermal method using bismuth nitrate and sodium tungstate as precursors. The microstructures and spectroscopic performances of prepared materials were investigated utilizing characterization methods, such as XRD, XPS, UV-vis, TEM, and N2 adsorption-desorption, etc., and the effluent removal performances were studied by using rhodamine B as a simulated degradation dye and the photodegradation mechanism was investigated in combination with DFT calculations. XRD indicates that the rare earth doping leads to the lattice distortion of the (131) crystal surface of Bi2WO6, and the relative amount of distortion is directly proportional to the photocatalytic activity; UV-vis spectra show that the absorption edge of Bi2WO6 is obviously red-shifted with the rare earth doping, and N2 adsorption-desorption curve show that the doped rare earths make the specific surface area of the sample effectively increased. Moreover, XPS spectrum suggest that the doped rare earth Ce and Eu often exist in the form of metastable oxidation states, and the transformation between Ce3+/Ce4+ and Eu2+/Eu3+ oxidation states is easy to form impurity energy levels between Bi2WO6, which make the energy level significantly enriched to broaden the absorption range and reduce band gap width of the material. DFT calculations further indicate that the rare earths successfully replace Bi sites. One of the main reasons for the improvement of photocatalytic activity is that rare earth doping is easier to replace Bi sites, leading to increased relative aberration; another one is that the arrangement of EVB and ECB in the photocatalytic mechanism is type-II, which contributes to red-shift of absorption edge and effective separation of electron-hole pairs in the photocatalytic process, thus improving the photocatalytic activity.

Preparation and Characterization of CuFeS2 Nanoparticles Synthesized via Hydrothermal Method

Abstract: This research involved the successful synthesis of CuFeS2 nanoparticles using a hydrothermal method. The CuFeS2 nanoparticles were characterized using various analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV-Visible spectroscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. The tetragonal crystalline structure was determined using X-ray diffraction (XRD) examination, indicating a particle size of 14 nm. The existence of chalcopyrite CuFeS2 nanoparticles was established by the analysis of Raman spectra. The amorphous morphology was observed by FESEM imaging. The existence of Cu, Fe,and S elements was verified using EDX analysis, with no significant impurities observed. The UV-Visible investigation revealed a significant capacity for absorption within the wavelength region of 500-600 nm, accompanied by an energy band gap of 2.35 eV. The examination of BETsurface area revealed a surface area of 62 m²/g and a pore size of 10 nm. The obtained findings suggest that the CuFeS2 nanoparticles possess favorable properties that render them appropriate for use in photocatalytic applications.

Cs-Doped WO3 with Enhanced Conduction Band for Efficient Photocatalytic Oxygen Evolution Reaction Driven by Long-Wavelength Visible Light.

Cesium doped WO3 (Cs-WO3) photocatalyst with high and stable oxidation activity was successfully synthesized by a one-step hydrothermal method using Cs2CO3 as the doped metal ion source and tungstic acid (H2WO4) as the tungsten source. A series of analytical characterization tools and oxygen precipitation activity tests were used to compare the effects of different additions of Cs2CO3 on the crystal structure and microscopic morphologies. The UV-visible diffuse reflectance spectra (DRS) of Cs-doped material exhibited a significant red shift in the absorption edge with new shoulders appearing at 440-520 nm. The formation of an oxygen vacancy was confirmed in Cs-WO3 by the EPR signal, which can effectively regulate the electronic structure of the catalyst surface and contribute to improving the activity of the oxygen evolution reaction (OER). The photocatalytic OER results showed that the Cs-WO3-0.1 exhibited the optimal oxygen precipitation activity, reaching 58.28 µmol at 6 h, which was greater than six times higher than that of WO3-0 (9.76 μmol). It can be attributed to the synergistic effect of the increase in the conduction band position of Cs-WO3-0.1 (0.11 V) and oxygen vacancies compared to WO3-0, which accelerate the electron conduction rate and slow down the rapid compounding of photogenerated electrons-holes, improving the water-catalytic oxygen precipitation activity of WO3.

Synthesis and application of gadolinium-doped ZnO/silica mesoporous nanocomposite for methylene blue removal

In this study, a silica mesoporous nanomaterial was synthesized using a hydrothermal method and then surface-modified with Gadolinium-doped ZnO nanoparticles. The synthesized samples were characterized using FTIR, XRD, BET, XPS, FESEM, and EDS techniques for surface and structural morphology analysis. Structural analysis revealed that the synthesized SBA-15 mesoporous silica possessed a crystalline structure. Conversely, the mesoporous material modified with zinc oxide and gadolinium oxide nanoparticles became amorphous. The activity of this nanocomposite for the removal of methylene blue, a colored pollutant, was evaluated. Five factors affecting methylene blue removal efficiency, including initial dye concentration, adsorbent amount, contact time, pH, and temperature, were investigated. The optimal values identified for efficient methylene blue removal were: initial concentration 10 mg/L (ppm), adsorbent amount 0.015 g, time 15 min, pH 7, and temperature 25 °C. The reusability of the adsorbent was also investigated, and it was found to exhibit good reusability for up to 8 cycles without a significant decrease in its methylene blue removal efficiency.

Highly dispersed BiVO4 nanoparticles supported by pseudoboehmite for effective removal of antibiotics

BiVO4/pseudoboehmite (PB) composite catalysts were innovatively prepared using the cost-effective PB as support by a facile hydrothermal method. BiVO4 nanoparticles with an average size of 12 nm are highly dispersed on the surface of PB. Compared to pure BiVO4, the composite BiVO4/6 %PB exhibits high specific surface area (32.9 m2/g) about double that of pure BiVO4 (15.1 m2/g) which can provide more adsorption and photocatalytic reaction sites. Meanwhile, the composite has enhanced photogenerated electron-hole separation and transfer efficiency. As a result, it has a superior performance of antibiotics removal in water than pure BiVO4. The tetracycline hydrochloride (TCH) removal efficiency of BiVO4/6 %PB can reach 87 % within 2 h with high stability (<7 % decay after four cycles) under LED lamp (380–780 nm) irradiation as well as high selectivity. Specifically, the adsorption efficiency and photocatalytic rate constant are respectively triple and double that of pure BiVO4. Simultaneously, the BiVO4/6 %PB also possesses high removal efficiency of amoxicillin (76 %). Our results indicate that the selection of cost-effective PB as catalyst support offers a new solution to solve the aggregation problem of BiVO4 nanoparticles and the composite obtained contributes to an economic and efficient BiVO4-based photocatalyst for antibiotics removal in sewage treatment.

Research Progress in the Preparation of Transition Metal Sulfide Materials and Their Supercapacitor Performance

Transition metal sulfides are widely used in supercapacitor electrode materials and exhibit excellent performance because of their rich variety, low price, and high theoretical specific capacity. At present, the main methods to prepare transition metal sulfides include the hydrothermal method and the electrochemical method. In order to further improve their electrochemical performance, two aspects can be addressed. Firstly, by controllable synthesis of nanomaterials, porous structures and large surface areas can be achieved, thereby improving ion transport efficiency. Secondly, by combining transition metal sulfides with other energy storage materials, such as carbon materials and metal oxides, the synergy between different materials can be fully utilized. However, future research still needs to address some challenges. In order to guide further in-depth research, it is necessary to combine the current research-derived knowledge and propose a direction for future development of transition metal sulfide electrode materials.

Fabrication of ZnO-carbon dots composite via microcrystalline cellulose for enhanced photocatalytic hydrogen production under simulated sunlight irradiation

The composite ZnO@CDs was prepared via the hydrothermal method. Microcrystalline cellulose (MCC) was used as the source of carbon dots (CDs). X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy, and transmission electron microscopy analyses were used to characterize the structure and morphology of ZnO@CDs. The prepared ZnO showed a flake morphology with the exposed plane of (001). The X-ray photoelectron spectroscopy and photoluminescence spectroscopy (PL) characterization showed that CDs can be produced by decomposition of MCC and then attached on the surface of ZnO. The photocatalytic properties of ZnO@CDs were investigated under simulated sunlight irradiation. The hydrogen production reached 1240 µmol·g-1 in 30 min, which was much higher than the bare ZnO. The mechanism for the enhanced catalytic property of ZnO@CDs was studied. A high hydrogen production rate (2480 µmol·g-1·h-1) in the short term would enable ZnO@CDs to work as an emergency power supply by hydrogen production and use for restoring electricity and wireless communication in complicated situations.

Electric field emission in GdNiO3 microflower

GdNiO3 microflowers were synthesized by hydrothermal method with unit sizes of about 2.2–3.5 μm and petal sizes of ∼75–100 nm. The X-ray diffraction pattern (XRD) and Raman spectra reveal an orthorhombic crystal structure with the space group Pbnm and various Raman active vibrational modes i.e., Ag, B1 g, B2 g associated with rare earth nickelates. The total density of states (TDOS) was calculated by density functional theory (DFT) study using a hybrid functional (HSE06) and the volume of TDOS near the Fermi level confirms the semiconducting nature of GdNiO3 with band gap ∼0.688 eV. The local bulk work function (φ) was estimated theoretically at ∼5.35 eV from DFT calculations which is one of the essential parameters for the field enhancement factor (β). Field emission current density (J) vs. applied electric field (E) divulges a low turn-on field (Eto)∼4.6 V/μm@1 μA/cm2 and a threshold field (Eth)∼5.2 V/μm@10 μA/cm2 respectively. The Fowler-Nordheim (F-N) model was introduced to calculate β ∼1637 and long-term field emission current stability was observed experimentally > 4 h at the preset values of current 2 μA and 10 μA, respectively. The easy preparedness, low turn-on field, and long-term current stability without significant decay suggest this material to be an efficient electron field emitting material in the rare-earth nickelates series.

Manipulation of non-isothermal crystallization kinetics of poly(lactic acid) composite film by a novel nucleating agent

As a type of renewable and biodegradable polymer, poly(lactic acid) (PLA) has been widely used in various fields. However, its weak crystallization ability deteriorates the properties of the final product. In this work, a novel nucleating agent (MWCNTs@CeO2), multi-walled carbon nanotubes (MWCNTs) decorated with ceria (CeO2), was synthesized using the hydrothermal method and subsequently used to manipulate the non-isothermal crystallization kinetics and nucleation behavior of PLA. The results show that MWCNTs@CeO2 can act as an effective nucleating agent to accelerate the crystallization rate of PLA by reducing the half-crystallization time. In non-isothermal crystallization kinetics, the Avrami equation modified by Jeziorny cannot accurately describe the non-isothermal crystallization behavior of PLA and PLA/MWCNTs@CeO2 composite films, whereas the Mo method can. Furthermore, it is found that the addition of MWCNTs@CeO2 does not change the crystal structure of PLA, but increases the nucleation and growth rate of PLA, thereby promoting its crystallization.

Heavy atom effect boosts the achievement of ultra-efficient long afterglow room temperature phosphorescent carbon point composites: An enhanced approach

In recent years, room temperature phosphorescent (RTP) materials have experienced rapid growth due to their enduring luminescence, high resolution, and other distinctive characteristics. Simultaneously, carbon dots (CDs) have gained popularity across various disciplines for their efficient luminescence, straightforward synthesis, and environmental friendliness. In this study, we successfully synthesized a range of high-performance carbon dot materials using a simple one-step hydrothermal method. Through detailed morphological and photophysical characterizations, we discovered that these materials exhibited a remarkable phosphorescence quantum yield of up to 53.15 %, an impressive feat for both metal and non-metal carbon dot materials. Furthermore, we explored the enhancing effect of the heavy atom on ultra-efficient long afterglow RTP carbon dot composites and experimentally validated its effectiveness. Finally, we applied these materials to information encryption technology, offering novel ideas and methods for RTP material applications. This research not only opens new avenues for the development of carbon dot materials but also provides a promising direction and outlook for their future use.

Construction of MoS2/NiS2 heterostructure with fast interfacial reaction kinetics for ultrafast sodium storage

Constructing heterostructure is a valid method to reinforcing sodium storage performance of transition metal chalcogenides materials. Herein, a simple, safe and controllable one step hydrothermal method is proposed to synthesize MoS2/NiS2 heterostructure. Due to the difference in band gaps and work functions of MoS2 and NiS2, the charges are redistributed at the MoS2/NiS2 heterointerfaces, thereby accelerating the migration of electrons and Na+. The heterointerfaces provide extra active sites for storing Na+, thus increasing the sodium storage capacity of the heterostructure. Furthermore, the distinct redox potentials of NiS2 and MoS2 promote the structural stability of MoS2/NiS2 heterostructure during the electrochemical reaction processes. Consequently, the obtained MoS2/NiS2 heterostructure exhibits superior rate properties (339.4 mAh g−1 at 10 A g−1) and ultra-stable cycling stability (480.5 mAh g−1 after 350 cycles at 1 A g−1). This paper presents a valid strategy for creating heterostructure anodes with excellent sodium storage properties.

Exploring calcite Coprecipitation: Synthesis, Crystal Growth, and pH effect

In this study, the synthesis and crystal growth of calcite (CaCO3) was examined with a focus on the coprecipitation and hydrothermal methods; additionally, crystal nucleation and growth was monitored under acidic and alkaline conditions. In the experiments, different Ca2+ solutions (pH 1.4 and 8.1) were mixed with Na2CO3 (pH 11.6), and the rates for the addition of the reactants were adjusted. Using an acidic Ca2+ solution as the calcium source and the rapid addition of carbonate, larger crystals were precipitated and grown in a single-step coprecipitation process. The fast addition of carbonate in an initially alkaline calcium solution produced intermediate crystal sizes. However, the slow dropwise addition of carbonate led to smaller crystals due to localized supersaturation and rapid nucleation. Coprecipitation followed by hydrothermal treatment produced larger crystals with the best-defined morphology. Structural and compositional analyses were conducted using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed the formation of calcite with different crystal sizes and provided insight into the controlled synthesis of CaCO3 crystals; our study has relevance for various industrial applications and for the investigation of natural sources.

Synthesis and photocatalytic mechanism study of visible light-driven Z-type Ag/AgBr/Bi2MoO6 composite materials for efficient degradation of organic dyes

The synthesis of the Ag/AgBr/Bi2MoO6 nanocomposite was achieved through a facile hydrothermal method combined with in situ photodeposition. Subsequently, its efficacy in catalyzing the degradation of Rhodamine B (RhB) under visible light irradiation was systematically investigated. The Bi2MoO6 samples and the Ag/AgBr/Bi2MoO6 nanocomposites underwent comprehensive characterization using a suite of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The analyses unveiled a homogeneous distribution of Ag nanoparticles on the surface of AgBr/Bi2MoO6, indicative of the successful formation of the composite. To assess the photocatalytic efficiency, the degradation of RhB under visible light irradiation was employed as a benchmark. Notably, the incorporation of Ag nanosheets, serving as electron mediators and Schottky barriers, facilitated efficient electron transfer between Bi2MoO6 and AgBr. Consequently, the photocatalytic activity of the ternary Z-type heterogeneous Ag/AgBr/Bi2MoO6 nanocomposites surpassed that of the pure Bi2MoO6 and AgBr samples. Remarkably, under 12 min of visible light irradiation, the photocatalytic activity of the Ag/AgBr/Bi2MoO6 nanocomposites reached an impressive 99.99 %.

Controlled synthesis of chiral carbon dots with high asymmetric catalytic properties and reproducibility for direct aldol reactions: The impact of functional groups of carbon sources

The controlled synthesis of carbon dots (CDs) has been a key scientific problem in the field of catalysis. In this study, chiral CDs from different carbon sources were prepared using the hydrothermal method with d-proline as the chiral source. The effects of the carbon source skeleton (conjugated and unconjugated) and functional groups (hydroxyl, carboxyl, and amino) on its structure, reproducibility, and asymmetric catalytic performance in Aldol condensation were investigated. It was observed that hydroxyl groups in the carbon source are more favorable for enhancing the asymmetric catalytic activity and reproducibility of CDs compared to amino and carboxyl groups. The mechanism for the difference in reproducibility and asymmetric catalytic properties is investigated, which is ascribed to the effect of bonding (Directional factor or Random factor) between active sites and carbon cores, as well as the effect of carbonization (Random factor). The directional factor contributes to high reproducibility and asymmetric catalytic activity.

Selective and Sensitive Detection of Cu+ in Living Cells Based on Chelator Modified Carbon Dots

AbstractCuprous ions (Cu+) are essential for various biological activities. However, it is still a great challenge to detect Cu+ efficiently in cells in situ. As emerging 0‐D carbon photoluminescence nanomaterials, carbon dots (CDs) exhibit non‐toxicity and ultra stability, which shows great advantages in biosensing and bioimaging. In this work, CDs are prepared by a one‐step microwave‐assisted hydrothermal method. To enhance the selectivity and efficiency of the CDs‐based sensor, the NS4‐CDs are synthesized by surface modification of CDs using Cu+ chelating molecules. The NS4‐CDs, that carry specific detection molecules, exhibit remarkable selectivity and high sensitivity with an extraordinarily low detection limit (26 nmol L−1). It is noteworthy that the detection response is extremely fast, which only takes 20 s. The PL response mechanism of NS4‐CDs is also thoroughly investigated. In addition, the NS4‐CDs possess great biocompatibility and non‐cytotoxicity, which is vital for advanced cellular imaging applications. Finally, the NS4‐CDs are successfully applied to Cu+ detection in cells in situ. This work paves a new path for the design and efficient construction of CDs‐based biosensors for ion detection in cells, which expands the application area of carbon nanomaterials.

The mechanistic pathway of paracetamol degradation using UV/H2O2 with PVP functionalized ZnO Nanorods

In the present investigation the mechanistic pathway of photocatalytic degrdation of paracetamol using Polyvinylpyrrolidone (PVP) functionalized ZnO nanorods (NRs) as a photocatalyst and catalysts' photostability have been studied. Pristine ZnO NRs and PVP functionalized ZnO NRs have been successfully synthesized by hydrothermal method. The XRD spectra reveal the polycrystalline nature of the synthesized ZnO NRs and PVP functionalized ZnO NRs. The peaks observed at 457 cm−1 and 446.5 cm−1 in the FT-IR spectra indicate the presence of bonding between Zn metal and oxygen atom in Pristine and PVP functionalized ZnO, respectively. The peaks absorption observed at 376, 373 nm for ZnO NRs and ZnONRs-PVP, respectively. After functionalization with carbonaceous material, a blue shift has been observed, which is due to increase in the crystallite size from ̴ 31 nm to ̴ 59 nm along the (100), (002) and (101) planes. The band gap values for pristine ZnO NRs and ZnONRs-PVP are found to be 3.10 eV, 2.95 eV, respectively, which is found less as compared to that of the bulk ZnO (3.37 eV). The surface morphology shows rod like structure of ZnO with flat edges and flower like structure with pointed edges for the ZnONRs-PVP. The degradation of paracetamol is effective upto 40 ppm concentration with the 200 mg/L of catalyst dose. Nearly 100 % paracetamol (20 ppm) has been successfully removed in 180 min, with the 50 mg/L catalyst dose of ZnONRs-PVP. The resulting quantum efficiencies in the degradation of paracetamol are found to be ̴ 0.10 % for ZnO NRs and 0.13 % for ZnONRs-PVP, respectively. The obtained results demonstrate the synergistic role of surface PVP (carbon) material in the degradation capability of ZnONRs-PVP in efficient removal of paracetamol from water. Therefore, ZnONRs-PVP can be a novel and promising material in wastewater treatment for sustainable future of environmental issues.

The optical properties of ZnO/ZnS:Mn core–shell nanorods prepared on GaN substrates

ZnO/ZnS:Mn/GaN core–shell nanorods device was obtained by depositing ZnO/ZnS:Mn core–shell nanorods on GaN substrate using pulsed laser deposition and hydrothermal method. The optical properties of the device were studied. The PL spectrum of ZnO/ZnS:Mn/GaN consists of four emission bands located at 375, 450, 530 and 590 nm. The forward opening voltage is about 6 V. Under forward bias, there are two luminescence bands located at 415 and 610 nm, and the intensity increases with the increase of forward voltage. The color coordinates of EL spectra are very close to standard white light, indicating that the device has potential application in white light LED. Compared to ZnO/GaN nanorods device, the white light quality of ZnO/ZnS:Mn/GaN core–shell nanorods device is better, and it is more suitable as a long-term light source.