Hydrothermal Synthesis Research Articles

Synthesis, Functionalization, and Biomedical Applications of Iron Oxide Nanoparticles (IONPs)

Iron oxide nanoparticles (IONPs) have garnered significant attention in biomedical applications due to their unique magnetic properties, biocompatibility, and versatility. This review comprehensively examines the synthesis methods, surface functionalization techniques, and diverse biomedical applications of IONPs. Various chemical and physical synthesis techniques, including coprecipitation, sol–gel processes, thermal decomposition, hydrothermal synthesis, and sonochemical routes, are discussed in detail, highlighting their advantages and limitations. Surface functionalization strategies, such as ligand exchange, encapsulation, and silanization, are explored to enhance the biocompatibility and functionality of IONPs. Special emphasis is placed on the role of IONPs in biosensing technologies, where their magnetic and optical properties enable significant advancements, including in surface-enhanced Raman scattering (SERS)-based biosensors, fluorescence biosensors, and field-effect transistor (FET) biosensors. The review explores how IONPs enhance sensitivity and selectivity in detecting biomolecules, demonstrating their potential for point-of-care diagnostics. Additionally, biomedical applications such as magnetic resonance imaging (MRI), targeted drug delivery, tissue engineering, and stem cell tracking are discussed. The challenges and future perspectives in the clinical translation of IONPs are also addressed, emphasizing the need for further research to optimize their properties and ensure safety and efficacy in medical applications. This review aims to provide a comprehensive understanding of the current state and future potential of IONPs in both biosensing and broader biomedical fields.

Nickel Vanadate Cathode Induced In Situ Phase Transition for Improved Zinc Storage by Low Migration Barrier and Zn2+/H+ Co‐Insertion Mechanism

AbstractDesigning cathode materials that exhibit excellent rate performance and extended cycle life is crucial for the commercial viability of aqueous zinc (Zn)‐ion batteries (ZIBs). This report presents a hydrothermal synthesis of stable Ni0.22V2O5·1.22H2O (NVOH) cathode material, demonstrating high‐rate performance and extended cycle life. A successful in situ phase transformation yields Zn3(OH)2V2O7·nH2O (ZVO), which undergoes an irreversible phase transition and exhibits exceptional energy storage properties. The procedure maintains the lattice structure of ZVO and ensures high structural stability throughout the phase transformation. The NVOH cathode material exhibits the discharge capacities of 399 mA h g−1 at a rate of 1 A g−1 after 400 cycles and 303 mA h g−1 at 10 A g−1 after 2000 cycles. Density functional theory calculations indicate that the material is protected by electrostatic forces and exhibits structural stability, with a Zn‐ion migration barrier of 0.32 eV across the host lattice and the electrode–electrolyte interface. Due to these properties, NVOH also exhibits high energy/power densities of 395 Wh kg−1/406 W kg−1 at 0.5 A g−1 and 288 Wh kg−1/8830 W kg−1 at 10 A g−1. Ex situ characterizations indicate structural modifications and irreversible phase changes of NVOH, highlighting the potential of H+ intercalation and in situ phase transitions for high‐performance aqueous ZIBs.

Green Hydrothermal Synthesis of Gallic Acid Carbon Dots: Characterization and Cytotoxic Effects on Colorectal Cancer Cell Line

Abstract Colorectal cancer remains a leading cause of cancer-related deaths worldwide, necessitating the development of novel therapeutic approaches. Carbon dots (CDs) have emerged as promising nanoparticles for biomedical applications due to their unique properties. Gallic acid (GA), a known anticancer agent, is effective against various tumor types. This study explores the potential of gallic acid-derived carbon dots (GA-CDs) as an innovative anticancer agent against HCT-116 colorectal cancer cells, focusing on apoptosis signaling pathways. GA-CDs were synthesized using a one-pot hydrothermal method. Characterization was conducted using transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet-visible (UV-Vis) absorption spectroscopy. The cytotoxicity of GA and GA-CDs on HCT-116 cells was evaluated using the MTT assay at various concentrations over 24 and 48 hours. Cellular uptake was assessed via fluorescence microscopy, and apoptosis was analyzed using acridine orange/propidium iodide (AO/PI) staining. Total RNA extraction followed by complementary DNA (cDNA) synthesis via RT-PCR was performed, and real time-PCR (Q-PCR) was conducted to examine the expression of apoptosis-related genes Caspase-3, Bax, and Bcl-2. Characterization confirmed the successful synthesis of spherical GA-CDs. GA-CDs exhibited dose- and time-dependent cytotoxicity, with IC50 values of 88.55 µg/mL for GA-CDs and 192.2 µg/mL for GA after 24 hours. Fluorescence microscopy confirmed the efficient uptake of GA-CDs by HCT-116 cells. AO/PI staining showed a significant increase in apoptotic cell numbers after treatment with GA-CDs. Q-PCR analysis revealed overexpression of Caspase-3 and Bax genes in GA-CD-treated cells, though no significant changes were observed in the expression of Bcl-2 or the Bax/Bcl-2 ratio. GA-CDs demonstrated potent anticancer properties by inducing apoptosis and reducing cell viability in HCT-116 cells. These findings suggest the potential of GA-CDs as a novel therapeutic agent for colorectal cancer treatment, warranting further investigation into their mechanism of action and in vivo efficacy.

Influence of the variation in hydrothermal reaction time on the structural, optical and electrical properties of NiTiO3 perovskite and its application for gas sensing

Influence of the variation in hydrothermal reaction time on the structural, optical and electrical properties of NiTiO3 perovskite and its application for gas sensing

Hydrothermal Synthesis of Zinc Cobaltite (ZnCo2O4) Nano Particles for Green Hydrogen Production via Water Splitting by Photocatalysis

Hydrothermal Synthesis of Zinc Cobaltite (ZnCo2O4) Nano Particles for Green Hydrogen Production via Water Splitting by Photocatalysis

3D Ternary Hybrid of VSe2/e‐MXene/CNT with a Promising Energy Storage Performance for High Performance Asymmetric Supercapacitor

AbstractMXene and TMDs are two of the emerging electrode materials for supercapacitors owing to their unique physicochemical properties such as high conductivity, large surface area, and rich redox active sites. However, sheet restacking, volume expansion and oxidation hinder these materials from being used in practical applications. In this work, a 3D ternary hybrid structure of metallic VSe2, Ti3C2Tx MXene and carbon nanotube was designed to address some of the challenges in 2D materials‐based electrodes for supercapacitor application. The exfoliated MXene and CNT decorated VSe2 3D structure showed excellent synergy between each component to deliver promising energy storage and cycling performance. The ternary hybrid structure also can suppress the surface oxidation of MXene sheets during the hydrothermal reaction. Furthermore, an asymmetric supercapacitor fabricated with VSe2/e‐MXene/CNT and MoS2/MXene delivered the highest energy density of 35.91 Wh/kg at a power density of 1280 W/kg and a remarkable cycle life.

Dodecylamine‐assisted hydrothermal synthesis of carbon‐supported ultrafine IrRu Nanoparticles for oxygen evolution electrocatalysis and overall water splitting

Ruthenium (Ru)‐ and iridium (Ir)‐based nanomaterials have always been regarded as efficient electrocatalysts for oxygen evolution reaction (OER) in acidic electrolytes. Herein, we develop a facile dodecylamine‐assisted hydrothermal synthesis for producing carbon‐supported IrRu alloy nanoparticles with controllable Ir/Ru ratios and ultrafine sizes towards high‐efficiency OER and overall water electrolysis. In this strategy, the dodecylamine that serves as a capping and reducing agent enables the final IrRu alloy nanoparticles to possess average sizes < 3 nm and high degree of dispersion on carbon substrate. By combining high OER activity of Ru with high acidic robustness of Ir, the as‐prepared IrRu/C nanoparticles at a suitable Ir/Ru ratio of 1/3 show good activity and durability for the OER electrocatalysis and overall water splitting. In specific, the Ir1Ru3/C catalyst exhibits the lowest overpotential of 302 mV at the current density of 10 mA cm‐2 and the highest mass activity of 120.5 mA mg‐1 at 1.532 V for OER in 0.5 M H2SO4 electrolyte. In addition, a two‐electrode acidic electrolyzer assembled with Ir1Ru3/C at anode and commercial Pt/C at cathode (Pt/C|| Ir1Ru3/C) exhibits a low cell voltage of 1.44 V for achieving the current density of 10 mA cm‐2, along with a satisfied 20‐h durability.

Preparation of Vanadium (3.5+) Electrolyte by Hydrothermal Reduction Process Using Citric Acid for Vanadium Redox Flow Battery

In this study, vanadium (3.5+) electrolyte was prepared for vanadium redox flow batteries (VRFBs) through a reduction reaction using a batch-type hydrothermal reactor, differing from conventional production methods that utilize VOSO4 and V2O5. The starting material, V2O5, was mixed with various concentrations (0.8 M, 1.2 M, 1.6 M, 2.0 M) of citric acid (CA) as the reducing agent and stirred for 60 min at 90 °C using a hot plate to ensure complete dispersion in the solution. The resulting solution was subsequently subjected to a hydrothermal reduction reaction (HRR) furnace at 150 °C for 24 h to generate vanadium (3.5+). The mixed states of the produced vanadium (3+) and vanadium (4+) were confirmed using UV-vis spectroscopy. The electrochemical properties of the electrolyte were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealing that the optimal concentration of the CA was 1.6 M. The current efficiency, energy efficiency, and voltage efficiency of the electrolyte produced via the HRR process was compared with that prepared using VOSO4 in charge and discharge experiments. The results demonstrate that the HRR process yields an enhanced electrolyte across all efficiency metrics produced through the given improved performance in all efficiencies. These findings indicate that the HRR process using citric acid can facilitate the straightforward preparation of vanadium (3.5+) electrolyte, making it suitable for large-scale production.

In Situ Synthesis of NPC-Cu2O/CuO/rGO Composite via Dealloying and Microwave-Assisted Hydrothermal Technique

The nanoporous copper (NPC)-copper oxides (Cu2O/CuO)/reduced graphene oxide (rGO) composite structure was synthesized by combining the dealloying process of Cu48Zr47Al5 amorphous ribbons with a microwave-assisted hydrothermal technique at a temperature of 200 °C. The main advantage of the microwave-assisted hydrothermal process is the oxidation of nanoporous copper together with the in situ reduction of graphene oxide to form rGO. The integration of rGO with NPC improves electrical conductivity and streamlines the process of electron transfer. This composite exhibit considerable potential in electrochemical catalysis application, due to the combined catalytic activity of NPC and the chemical reactivity of rGO. Our study relates the transition to n-type rGO in microwave-assisted hydrothermal reactions, and also the development of an electrode material suitable for electrochemical applications based on the p-p-n junction NPC-Cu2O/CuO/rGO heterostructure. To confirm the formation of the composite structure, structural, morphological, and optical techniques as XRD, SEM/EDX, UV-Vis and Raman spectroscopy were used. The composite’s electrochemical properties were measured by EIS and Mott-Schottky analyses, showing a charge transfer resistance (Rp) of 250 Ω and indicating the type of the semiconductor properties. The calculated carrier densities of 4.2 × 1018 cm−3 confirms n-type semiconductor characteristic for rGO, and 7.22 × 1018 cm−3 for Cu2O/CuO indicating p-type characteristic.

Synthesis of SrTiO3 nanoparticles for photocatalytic applications

Due to the heightened emphasis on environmental protection and the escalating demand for renewable energy sources, the potential applications of strontium titanate (SrTiO3) nanoparticles in photocatalysis have shown remarkable promise. With rapid advancements in technological capabilities, the standards for SrTiO3 photocatalytic materials have soared. Researchers have relentlessly delved into and innovated techniques for preparing strontium titanate powders, striving to yield nanocrystalline SrTiO3 that exhibits specific morphologies, high purity, superior dispersibility, and exceptional photocatalytic efficiency, while continually refining the properties of these powders. The paper encapsulates the advancements in preparation methodologies and photocatalytic attributes of perovskite SrTiO3 nanoparticles, encompassing diverse synthetic routes such as hydrothermal synthesis, sol-gel process, chemical precipitation, solid-state reaction, sonochemical technique, and composite modification strategies. The characteristics, merits, demerits, and prevailing challenges associated with each synthesis technique are thoroughly and analyzed. Ultimately, this review serves as a valuable reference and foundation for the synthesis, modification, and application of SrTiO3 nanoparticle photocatalysts, fostering their development and practical implementation in environmental remediation and renewable energy technologies.

Research on the Basic Properties and Preparation Methods of Heat Conversion Materials

The purpose of this literature review is to discuss the research progress and application prospects of high-efficiency thermoelectric conversion materials. In recent years, high-efficiency thermoelectric materials have garnered extensive attention due to their significant applications in waste heat recovery and energy conversion. This paper reviews various types of thermoelectric materials, including metal chalcogenides, silicides, and skutterudite materials, and analyzes their synthesis methods, properties, and advantages and disadvantages. The findings indicate that chemical vapor deposition (CVD), hydrothermal synthesis, and hot pressing are the primary methods for preparing thermoelectric materials, each with distinct advantages and limitations. Nevertheless, by optimizing the preparation processes and material compositions, high-efficiency thermoelectric materials are poised to play a crucial role in the field of sustainable energy in the future. This review summarizes the key findings of current research and suggests potential directions and challenges for future studies.

Hydrothermal Synthesis of Hierarchical Cage-like Co9S8 Microspheres Composed of Nanosheets as High-Capacity Anode Materials

Hydrothermal Synthesis of Hierarchical Cage-like Co9S8 Microspheres Composed of Nanosheets as High-Capacity Anode Materials

Facile microwave hydrothermal synthesis of citric acid-derived carbon dots for photothermal therapy of cancers under NIR irradiation

Facile microwave hydrothermal synthesis of citric acid-derived carbon dots for photothermal therapy of cancers under NIR irradiation

Breathing effect in a Tetrapodal Lanthanide‐Phosphonate Organic Framework

The highly flexible organic linker hexamethylenediamine‐N,N,N’,N’‐tetrakis(methylphosphonic acid) (H8htp) was used in the preparation of a new 3D MOF formulated as [La2(SO4)2(H6htp)(H2O)4]∙2H2O (UAV‐15) by using hydrothermal synthesis. The flexibility of the organic linker posed a serious challenge in the preparation of crystalline materials: for this, the judicious selection of sulfuric acid to act as a mineralizing agent proved to be instrumental, acting in the retardation of the coordination of the phosphonic acid groups, as well as being an integral part the UAV‐15 by coordinating to the metal center. The material is a 3D network having channels filled with crystallization water molecules that can be easily removed by increasing of temperature (120ºC for 24h), leading to a single‐crystal‐to‐single‐crystal transformation originating [La2(SO4)2(H6htp)(H2O)3] (UAV‐15d). This transformation maintains the overall topology of UAV‐15 with only a small distortion of the framework. The reversibility of this transformation was studied, with the material reverting naturally to its original structure at ambient conditions for a period of 3 months or, in a faster way, when immersed in water at 120 ºC for 24h.

Effect of synthesis temperature on the properties and photocatalytic performance of peroxo-titanate nanotubes prepared by bottom-up synthesis method

The alkaline treatment synthesis of titania/titanate nanotubes (TNTs) requires highly concentrated alkaline solutions (≥ 10 mol/L), which pose environmental and productivity limitations. In contrast, a bottom-up synthesis method for peroxo-titanate nanotubes (PTNTs) has been developed. This method offers two advantages: it can synthesize materials using low-concentration alkaline solutions (1.5 mol/L) and produce photocatalytic materials that are responsive to visible light. In general, the higher the crystallinity of a catalyst, the better its properties. However, PTNTs synthesized at temperatures close to their boiling point (around 100 °C) exhibit low crystallinity. This study hypothesizes a hydrothermal synthesis method at higher temperatures will enhance the crystallinity and photocatalytic performance of PTNTs, synthesizing them at temperatures ranging from 120 to 200 °C using a method capable of exceeding the boiling point. Higher synthesis temperatures resulted in improved morphological and crystallographic properties of the PTNTs. However, the formation of peroxo-bonding, crucial for visible light responsiveness, decreased. Nevertheless, peroxo-bonding formation was still achievable at the highest temperature of 200 °C, and the sample exhibited the best Rhodamine B (Rh B) photodegradation performance under visible light due to its enhanced specific surface area and crystallinity. This study highlights the novelty and environmental significance of hydrothermally synthesized PTNTs as superior photocatalysts by optimizing the synthesis temperature while using lower concentration alkaline solutions.

Controllable Synthesis of BixOyBrz/TiO2 Heterojunctions with Excellent Visible‐Light‐Driven Photocatalytic Activities for Phenol

AbstractBixOyBrz/TiO2 composites have been synthesized by hydrothermal method, with TiO2 nanoparticles being employed as substrate. During the process of hydrothermal reaction, both temperature and pH have been utilized to effectively regulate the Bi/Br atomic ratio of BixOyBrz/TiO2 composites. In essence, the competitive reaction between OH− and Br− in the solution is the key factor to form BixOyBrz with different Bi/Br atomic ratios. Under visible light, the prepared Bi4O5Br2/TiO2 heterojunction demonstrates higher photocatalytic activity than other BixOyBrz/TiO2 composites for phenol and Rh B. The removal rate of phenol with Bi4O5Br2/TiO2 heterojunction is up to 92.1% after irradiation for 75 min. The excellent photocatalytic activities of Bi4O5Br2/TiO2 heterojunction are mainly attributed to its optimized microstructure and the matching band energy structure, whereby TiO2 nanoparticles with ≈10 nm diameter uniformly arranged on ≈10.2 nm thick Bi4O5Br2 nanosheets. Moreover, the heterojunction structure promotes the separation of photo‐generated electrons and holes in Bi4O5Br2/TiO2, while and h+ are the main active species during its photocatalytic processes.

Depolymerization of Lignosulfonate Catalyzed by Different Solid Base Oxides to Prepare Phenolic Compounds

Lignin is the most abundant aromatic renewable polymer in nature. However, its very stable structure limits its widespread application. To achieve high-value utilization of lignin, this study used solid base oxides to depolymerize calcium lignosulfonate (CLS) for the synthesis of phenolic compounds. The catalyst precursors were prepared by hydrothermal synthesis, and the corresponding mesoporous metal oxides NiO, MgCoOx, and NiMgCoOx were obtained after calcination. MgCoOx and NiMgCoOx had similar but stronger basicity compared to NiO. While all oxides promoted the depolymerization of CLS, NiMgCoOx was identified as the best catalyst, achieving a maximum liquid product yield of 74.3 wt.% and a selectivity of phenolic compounds of 74.52% in the liquid product. In addition, NiMgCoOx showed satisfactory structural and catalytic stability. The experimental results indicated that solid base oxides can capture the active hydrogen in CLS, causing the hydrolysis reaction of ether bonds, and the resulting products continuously depolymerize or polymerize; Co present in the catalyst promotes the adsorption of hydrogen by Ni, while NiO in NiMgCoOx facilitates the adsorption of both reactants and hydrogen. The combination of Ni and Co improves hydrogenation performance.

Single-step hydrothermal synthesis of zinc oxide nanorods for potential use as nano-antibiotics without seeding or bases.

The alarming global rise in antibiotic resistance, driven by the widespread overuse of traditional antibiotics, has created an urgent demand for new antimicrobial solutions. This study presents zinc oxide (ZnO) nanorods as a potential nano-antibiotic agent. ZnO nanorods, with a 2:3 aspect ratio, were synthesized using an efficient one-step hydrothermal method at a low temperature of 100°C, reducing the synthesis time to just 5 hours. The synthesized ZnO nanorods' morphology, structure, and composition were characterized using scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy. The potent antimicrobial activity of these nanorods against common bacterial strains such as Escherichia coli, Bacillus subtilis, and Vibrio parahaemolyticus was examined through optical density at 600 nm (OD600) measurements and inhibition zone analysis, demonstrating substantial inhibition of bacterial growth. In particular, at a concentration of 5 mg/mL, ZnO nanorods achieved a 96% reduction of B. subtilis bacteria in OD600 and an impressive 99.87% reduction in culturing assays within one day, showcasing bactericidal efficiency on par with tetracycline at 0.003 mg/mL. Furthermore, a predictive model of bacterial growth was developed and validated, providing insights into the time-dependent bactericidal efficiency of the synthesized nanorods. These results highlight the potential of ZnO-based composites as a promising solution to combat antibiotic resistance, paving the way for next-generation antimicrobial materials.

The change of phase composition and the morphology of particles of hydrothermal titanosilicate precipitates during their aging

During the study of phase formation under conditions of hydrothermal synthesis of alkaline titanosilicate systems (NH₄)₂TiO(SO₄)₂⋅H₂O или TiOSO₄⋅H₂O-Na₂SiO₃-NaOH-H₂O it was found that the formed titanosilicate solid phases differ both in composition and structure. The process of their aging under conditions of long-term exposure without forced heating is accompanied mainly by the loss of free water without noticeable structural and morphological changes. The exposure to the temperature of 70–100°С significantly accelerates the process of solid phase transformation. In these conditions, a porous system of particles is formed, which is confirmed by an increase in their specific surface area and total pore volume, as well as by an increase in the activity of the powders to absorb single- and double-charged cations. The effectiveness of hydrochloric acid treatment of fresh and especially aged precipitates on the ordering of the structure with the formation of crystals of a clear frame shape, inherent in the minerals zorite and ivanyukite, which contributes to increasing the sorption capacity of the final product is shown. The obtained results are used to adjust the technological regulations, which are used to test the technology of titanosilicate sorbent on the pilot plant.

Corrosion of nickel foam electrodes during hydrothermal reactions: The influence of a simple protective carbon black coating

Nickel foam (NF) substrates are widely used to support electrocatalysts, and this is frequently achieved using hydrothermal reactions, where the NF is immersed in the hydrothermal reactor together with the electrocatalyst precursors. However, other reactions including the corrosion of the NF and changes to the pH occur simultaneously, and these can affect the quality of the final electrocatalyst. Herein, a simple approach is devised to minimise these unwanted reactions. Carbon black (CB) was non-covalently functionalised at room temperature using tannic acid to give very stable and good dispersions of fCB in deionised water. Using a simple sonication step, the NF was coated with a uniform layer of the dispersed fCB. This layer served to minimise the corrosion of the underlying NF during the hydrothermal reactions with very good protection observed up to a temperature of 160 °C in deionised water at a pH of 2.0. The corrosion currents of the NF and fCB@NF were estimated at 8.7 µA and 3.9 µA, respectively, at room temperature in this acidic solution. Using a model reaction, the successful nucleation and growth of MnCo2O4 cubes was observed at fCB@NF, but not at the corroding NF.