Hydrothermal Method Research Articles

Controlled reaction dynamics of cellulose: Revealing the dual morphology nanocrystals

Cellulose nanocrystals exhibit diverse morphology with embedded crystallinity derived from the ordered crystalline regimes of cellulose fibers. Acid hydrolysis parameters controls the morphology of nanocrystals and is the primary efficient route for the synthesis of cellulose nanocrystals. In this study, we explored the impact of temperature on the morphology engineering of cellulose nanocrystals derived from banana pseudostem by oxalic acid hydrolysis, an underexplored method. Confirmation of successful cellulose extraction was achieved through fibrous morphology observed in FESEM and TEM analyses. X-ray diffraction and Raman spectroscopy affirmed the presence of type II cellulose. Notably, for the first time, we report the derivation of toroidal and spherulitic sheet-like morphologies in cellulose nanocrystals synthesized by hydrothermal method from banana psuedostem. Our investigation revealed that cellulose hydrolysis at 120 °C yields nanocrystals characterized by toroidal and spherulitic sheet-like morphologies with excellent crystallinity, as confirmed by FESEM and TEM analyses, with average thicknesses of 13.70 nm and 18.05 nm, respectively. Interestingly, elevating the hydrolysis temperature to 180 °C led to the collapse of these structures into carbon dots, exhibiting notable cyan emission.

Fabrication of Flower-Shaped Sb2S3/Fe2O3 Heterostructures for Enhanced Photoelectrochemical Performance.

Antimony sulfide (Sb2S3) has been recognized as a catalytic material for splitting water by solar energy because of its suitable narrow band gap, high absorption coefficient, and abundance of elements. However, many deep-level defects in Sb2S3 result in a significant recombination of photoexcited electron-hole pairs, weakening its photoelectrochemical performance. Here, by using a simple hydrothermal and spin-coating method, we fabricated a step-scheme heterojunction of Sb2S3/α-Fe2O3 to improve the photoelectrochemical performance of pure Sb2S3. Our Sb2S3/α-Fe2O3 photoanode has a photocurrent density of 1.18 mA/cm2 at 1.23 V vs reversible hydrogen electrode, 1.39 times higher than that of Sb2S3 (0.84 mA/cm2). In addition, our heterojunction has a lower onset potential, a higher absorbance intensity, a higher incident photon-to-current conversion efficiency, a higher applied bias photon-to-current efficiency, and a lower charge transfer resistance compared to pure Sb2S3. Based on ultraviolet photoelectron spectroscopy, we constructed a step-scheme band structure of Sb2S3/α-Fe2O3 to explain its photoelectrochemical enhancement. This work offers a promising strategy to optimize the performance of Sb2S3 photoelectrodes for solar-driven photoelectrochemical water splitting.

An investigation on the photocatalytic and antibacterial response of green fluorescent carbon dots synthesized from corn flour

Abstract The present work elucidates on a facile hydrothermal synthesis method for producing highly fluorescent carbon dots using corn flour as a natural carbon source. The structural confirmation was validated through XRD (X-ray Diffraction), HR-TEM (High-Resolution Transmission Electron Microscope), and FTIR (Fourier Transform Infra-Red) studies. The synthesized carbon dots exhibited an excitation-dependent photoluminescence (PL) emission. The optical band gap of as-synthesized carbon dots was estimated using UV-absorption spectral analysis. The variation in optical and luminescent response of the carbon dot suspension with the rate of centrifugation was also monitored. Furthermore, investigations on the photocatalytic response of as-synthesized carbon dots towards degradation of methylene blue and its activity as a potential antimicrobial agent against Escherichia coli are also presented.

Tuning the D-Band Center of Bi2S3─MoS2 Heterostructure Towards Superior Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage devices due to their environmental friendliness, low cost, and high specific capacity. However, the slow electrochemical kinetics and the "shuttle effect" have seriously hindered their commercialization. Herein, the nanoflower Bi2S3─MoS2 (BMS) heterostructure is synthesized by a two-step hydrothermal method, and then the Bi2S3─MoS2-Polypropylene (BMS-PP) interlayer is constructed. The heterostructure is rich in active sites, in which BMS has strong adsorption to lithium polysulfides (LiPSs) and can effectively anchor LiPSs while catalyzing LiPSs and promote the redox of Li2S at the same time, which can improve the utilization of active substances. More importantly, the d-band center can be tuned by the formation of Bi2S3─MoS2 heterostructure. Thus, Li-S batteries containing the BMS-PP interlayer show excellent rate performance (841.6 mAh g-1 at 5 C) and cycling performance (70.3% capacity retention after 500 cycles at 3 C). This work provides a new route for high-performance lithium-sulfur batteries.

Enhanced visible light-driven hydrogen evolution in non-precious metal Ni2P/CdIn2S4 S-type heterojunction via rapid interfacial charge transfer

Strong light absorption capacity and effective separation of photogenerated charge are the keys to photocatalytic water decomposition, which is usually solved by constructing heterojunction methods. In this work, a novel n-n interwoven Ni2P/CdIn2S4 S-type heterojunction photocatalyst was prepared by hydrothermal method for efficient photocatalytic hydrogen evolution. After a series of characterization and performance tests, under simulated sunlight irradiation at 6 °C (λ > 420 nm), the hydrogen production of Ni2P/CdIn2S4 composite with the best performance can reach 6 mmol/g/h, which is not only 48 times that of pure CdIn2S4, but also 17.2 times that of the expensive metal Pt (CIS–1Pt). By changing the temperature, the hydrogen production of Ni2P/CdIn2S4 reached 8.7 mmol/g/h at 27.5 °C, while its AQY reached 7.7 % and 6.6 % at 420 nm and 475 nm, respectively. In addition, the possible photocatalytic mechanism was analyzed by band structure and XPS diagram, and it was confirmed that the internal electric field of the S-type heterojunction accelerated the photogenerated charge transition and enhanced the hydrogen evolution ability. This effectively compensated for the limitations of severe carrier recombination and low active sites in CdIn2S4 photocatalysts. Therefore, this work provides some help for the construction of non-precious metal S-type heterojunctions for photocatalytic hydrogen production.

Augmented electrochemical capacities of microporous MoS2@NiO heterostructures

In this investigation, MoS2@NiO heterostructures are competently synthesized through a straightforward hydrothermal method to serve as an electrode material with augmented electrochemical capabilities. Variations in the concentration of MoS2 in the composite material are explored to optimize its performance. Extensive analyses are conducted to evaluate the structural, morphological, and electrochemical attributes of the synthesized material. The most refined MoS2@NiO heterostructure-based electrode showcases a notable specific capacity of 419.5 C/g (1048.75 F/g) at 1 A/g, transcending MoS2 and NiO-based electrodes by 60 % and 45 %, respectively. It is revealed that Faradic or diffusion phenomena predominate in the charge storage mechanisms. Capitalizing on the synergistic interplay between MoS2 and NiO within the composite material, the supercapacitor with asymmetric configuration i.e. MoS2@NiO//graphite-activated carbon (GAC), achieves a commendable energy density of 47.43 Wh/kg at 0.825 kW/kg. Furthermore, the developed device retains approximately 80 % of its specific capacitance and around 85 % of Coulombic efficiency after 5000 cycles at 2 A/g, underscoring its robust cyclic stability.

Unraveling the Structure-Activity-Stability Relationship over Gallium-Promoted HZSM-5 Nanocrystalline Aggregates for Propane Aromatization.

The aromatization of light alkane is an important process for increasing the aromatic production and utilization efficiency of light alkane resources simultaneously. Herein, Ga-modified HZSM-5 catalysts were prepared and investigated by a series of characterization techniques such as X-ray diffraction, nuclear magnetic resonance spectroscopy, transmission electron microscopy, N2 adsorption-desorption, and NH3 temperature-programmed desorption to study their physicochemical properties. The catalytic performance in propane aromatization was also tested. Importantly, the structure-activity relationship, reaction pathway, and coke formation mechanism in propane aromatization were systematically explored. It was found that different Ga introduction methods would affect the amounts of Brønsted and Lewis acid sites, and Ga-HZSM-5 prepared by the hydrothermal method exhibited higher amounts of Brønsted and Lewis acid sites but a lower B/L ratio. As a result, Ga-HZSM-5 showed higher propane conversion and benzene, toluene, and xylene yield compared with that of Ga2O3/HZSM-5. The propane aromatization reaction pathway indicated that propane dehydrogenation to propene was a crucial step for aromatic formation. The increase of the Lewis acid density in Ga-HZSM-5 can effectively improve the dehydrogenation rate and promote the aromatization reaction. Furthermore, the formation of coke species was studied by thermogravimetry-mass spectrometry and Raman approaches, the results of which indicated that the graphitization degree of coke formed over spent Ga-HZSM-5 is lower, resulting in enhanced anticoking stability.

Manganese Oxides with Different Morphologies In Situ Anchored onto Ti3C2Tx Nanosheets: Highly Effective Decontamination toward Sulfur Mustard Simulants.

Manganese oxides with porous structure and abundant active sites show potential in degrading sulfur mustard (HD). However, there is an interface effect between the oily liquid HD and nano oxides, and the powder is prone to agglomeration, which leads to incomplete contact and limited degradation ability. Here, we demonstrate a simple hydrothermal method for preparing MnO2/Ti3C2 composites to address this problem. The influence of morphology and crystal structure on performance are examined. Herein, flower-like MnO2 is loaded onto the surface or interlayer of Ti3C2-MXene nanosheets during in situ formation, significantly expanding the specific surface area. It also provides abundant acid-base sites and oxygen vacancies for the degradation of simulants 2-chloro-ethyl-ethyl thioether (2-CEES) without external energy, resulting in a reaction half-life as fast as 12.5 min. The relationship between structure and performance is clearly elaborated through temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS) analyses. Based on in situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis, gas chromatography-mass spectrometry (GC-MS) analysis, and density functional theory (DFT) calculation, the proposed degradation pathway of the 2-CEES molecule is a synergistic effect of hydrolysis, elimination, and oxidation. Furthermore, the products are nontoxic or low toxic. Metal oxide/MXene composites are first illustrated for their potential use in degrading sulfur mustard, suggesting new insights into these materials as novel decontamination for decomposing chemical warfare agents.

MAA Encapsulated MoS2 Quantum Dots as a Fluorescent Probe for the Sensing of Flavonoid

Transition metal dichalcogenide (TMDs) quantum dots (QDs) have attracted widespread attention among scientific community as fluorescent nanomaterial. Among TMDs, MoS2 has received particular interest due to its novel and intriguing optical properties. In this work hydrothermal method is used to prepare aqueous soluble MoS2 QDs using Molybdenyl acetylacetonate and thiourea as Mo and S precursors, respectively. The solubility of unfunctionalized MoS2 is poor in water and organic solvent, therefore thioglycolic acid is used as surfactant for surface functionalization and to enhance the aqueous solubility & stability. These functionalized QDs have been synthesized at pH 11 using hydrothermal method and explored their structural and optical properties. The as synthesized QDs are characterized using TEM, XRD, FTIR, UV-Vis and PL spectroscopy. The morphological shape of as prepared QDs is spherical with size 4-6.5 nm. The MAA encapsulated MoS2 QDs are further explored as fluorescent probe for the sensitive sensing of flavonoid Quercetin.

Hydrothermal synthesis of αILiVOPO4 as a cathode material for Li-ion batteries

This paper presents the synthesis of a novel cathode material, αI-LiVOPO4, featuring a porous multilayered lamellar structure, achieved through the hydrothermal method. Initially, αI-LiVOPO4·2 H2O was synthesized by maintaining a reaction kettle at 160 °C for 40 h. Subsequently, the parent compound underwent dehydration at various temperatures for 2 h to yield αI-LiVOPO4. The dehydration process was investigated through thermogravimetric analysis. Analysis via powder X-ray diffraction confirmed the crystallization of the product into the αI-LiVOPO4 phase. TEM and EDS analyses revealed an irregular porous structure with uniform distribution of elements. The electrochemical performance of αI-LiVOPO4 was evaluated through constant current charge-discharge tests within a voltage range of 3–4.5 V. Results demonstrated an initial capacity of 106.9 mAh·g–1 at 0.05 C, with a capacity retention of 100.9 mAh·g–1 after the 50th cycle. Additionally, cyclic voltammetry indicated favorable cycling performance and minimal polarization at elevated voltages.

Carbon coated iron pyrite (C–FeS2) photo-electrode for photo-electrochemical water splitting

In this paper, we present fabrication of ‘FeS2’ and carbon coated FeS2 (C–FeS2) photo-electrodes and demonstrated that coating of carbon on FeS2 significantly enhanced photo-electrochemical properties. The hydrothermal method has been adopted for the synthesis of FeS2 and carbon coating on FeS2 was achieved by CVD technique. The materials are subsequently characterized using X-ray diffraction, Raman spectroscopy and Field enhanced scanning electron microscope (FESEM) techniques for phase identification and morphological studies, respectively. The photo-electrochemical measurements revealed significant enhancement in the current density from ∼2 to 3.7 mA/cm2 (∼1.8 times higher) for C–FeS2 in comparison to the FeS2 photo-electrode under visible light. The enhancement in FeS2 after carbon coating has been attributed to reduction in recombination of photo generated charge carriers, enhancement in the band bending and lowering the charge transfer resistance at the semiconductor/electrolyte interface. To date, very few studies have been reported on FeS2 based composites for water splitting applications and use of carbon coating can be a novel approach for developing efficient solar to hydrogen conversion devices. The mechanism for the photocurrent enhancement was supported by Mott-Schottky and electrochemical impedance spectroscopy measurements.

Porous Chitosan/Hydroxyapatite Composite Microspheres for Vancomycin Loading and Releasing.

Porous chitosan/hydroxyapatite (Chi-HAp) composite microspheres were prepared in an aqueous solution containing chitosan, calcium nitrate, and ammonium dihydrogen phosphate by using a hydrothermal method at various temperatures. The investigation indicated that temperature significantly impacted the final product's appearance. Hydroxyapatite (HAp) coupled with dicalcium phosphate dihydrate (DCPD) flakes were obviously found at 65 and 70 °C, while the latter gradually disappeared at higher temperatures. Conversely, synthesis at 90 °C led to smaller particle sizes due to the broken chitosan chains. The microspheres synthesized at 75 °C were selected for further analysis, revealing porous structures with specific surface areas of 36.66 m2/g, pores ranging from 3 to 100 nm, and pore volumes of 0.58 cm3/g. Vancomycin (VCM), an antibiotic, was then absorbed on and released from the microspheres derived at 75 °C, with a drug entrapment efficiency of 20% and a release duration exceeding 20 days. The bacteriostatic activity of the VCM/composite microspheres against Staphylococcus aureus increased with the VCM concentration and immersion time, revealing a stable inhibition zone diameter of approximately 4.3 mm from 24 to 96 h, and this indicated the retained stability and efficacy of the VCM during the encapsulating process.

2D/2D interfacial coupling of NiFe-LDH and Ti3C2Tx for oxygen evolution reaction

Designing electrocatalysts for electrochemical water splitting to generate renewable energy has been a prospective interest throughout the previous decade. The efficiency of electrochemical water splitting, however, is impeded by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, the heterostructure of layered double hydroxides (NiFe-LDH) and MXene (Ti3C2Tx) were synthesized via hydrothermal (NiFe-LDH/Ti3C2Tx-H) and physical mixing (NiFe-LDH/Ti3C2Tx-P) methods. The NiFe-LDH/Ti3C2Tx-H exhibited an overpotential of 269 mV at 10 mA cm−2, indicating superior performance as compared to NiFe-LDH/Ti3C2Tx-P (353 mV) and RuO2 (313 mV). The double layer capacitance (Cdl) of NiFe-LDH/Ti3C2Tx-H was higher (2.05 mF cm−2) as compared to NiFe-LDH/Ti3C2Tx-P (1.63 mF cm−2), thus indicating more active sites for improving reaction kinetics. Additionally, the NiFe-LDH/Ti3C2Tx-H electrocatalyst retained stable performance (96.1%) after 10 h of chronopotentiometry at a constant current density of 10 mA cm−2.

Preparation and characterization of hollow spherical indium tin oxide with micro size by template assisted hydrothermal method

Preparation and characterization of hollow spherical indium tin oxide with micro size by template assisted hydrothermal method

Degradation of clofibric acid by ozonation assisted by Co-Ce-SBA-15: Role of interfacial electron migration

Restrained by the sluggish Ce redox cycle, Ce-SBA-15 exhibited the low electron transfer toward O3 activation. To this end, cobalt‑cerium co-doped SBA-15 with three-dimensional pore structure was designed using urea-assisted hydrothermal method and its activity was evaluated using Clofibric acid (CA) as target pollutant. XRD and N2 adsorption-desorption characterizations suggested that Co-Ce-SBA-15 possessed a three-dimensional pore structure with high order degree. py-FTIR, O2-TPD, H2-TPR, and in situ electrochemical characterizations indicated that compared with Ce-SBA-15 and Co-SBA-15, Co-Ce-SBA-15 had greater Lewis acid strength, electron transfer ability and oxygen reducibility. Co-Ce-SBA-15/O3 achieved the greater CA removal and mineralization rate, with 98.7 % CA removal and 58.3 % TOC removal were obtained in 90 min. Co-Ce-SBA-15/O3 process would be inhibited by the coexisting Cl−, NO3− and SO42−. Co-Ce-SBA-15 demonstrated the greater ozone utilization rate than those of monometallic SBA-15. Lewis acidic sites of Co and Ce were the main sites for activating O3. DFT results suggested that the obvious electron transfer existed among O3, Co and Ce Lewis acid sites. The conversion of Co3+/Co2+ and Ce4+/Ce3+ accelerated the interfacial electron transfer, which favored for conveying O3 into •OH. •OH was the primary reactive oxygen species involved in degrading CA. 8 kinds of intermediates were found during CA degradation and the possible degradation route was proposed. This study deepened the understanding of the cooperative effect of Co and Ce in catalytic ozonation process.

Preparation of biomass carbon dots/carboxymethyl cellulose-based fluorescent hydrogel: Combines selective detection and visual adsorption for Copper(II)

Abstract In this study, we used nitrogen-doped carbon dots (NCDs), which were synthesized via the hydrothermal method of corn-stover biomass as raw material and polyethyleneimine (PEI) as the nitrogen source, introduced them into the carboxymethyl cellulose-based hydrogel to prepare an environmentally friendly fluorescent cellulose-based hydrogel (NCDs/CMC-PAM). NCDs/CMC-PAM was also used for simultaneous fluorescence monitoring and removal of Cu (II) in aqueous solution. The chemical and physical structures, adsorption behaviors and fluorescent properties of NCDs/CMC-PAM were investigated. The results showed that NCDs/CMC-PAM exhibited a well-linear response range of fluorescence response for Cu (II) (0∼100 μM, detection limit of 3.42 μM). NCDs/CMC-PAM showed maximum adsorption capacities of 237.71 mg/g for Cu (II), the adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetic model, which is an exothermic spontaneous reaction with an increase in entropy. It can still maintain 79.03% of the original adsorption capacity after six cycles (pH=6). The adsorption mechanisms of NCDs/CMC-PAM for Cu (II) are intraparticle diffusion, electrostatic attraction, ion exchange, and ligand interaction. Hence, the present study provides a new green way to synthesize an adsorbent that can be applied for the adsorption and detection of heavy metal ions.

Hydrothermal synthesis of Zingiber/ZnO for enhanced photodegradation of ofloxacin antibiotic and reactive red azo dye (RR141).

The examination of photocatalyst powders for the total removal of pollutants from aqueous solutions is a vital research subject within the realm of environmental preservation. The objective of this study is to develop a photocatalyst heterojunction consisting of Zingiber/ZnO-H for the degradation of both the reactive red dye (RR 141) and ofloxacin antibiotic in wastewater. The current investigation outlines the process of synthesising a composite material by combining Zingiber montanum extract with zinc oxide (ZnO) by a hydrothermal method. The synthesis was conducted at a temperature of 180°C for a period of 4 hours. Consequently. The photocatalyst with a constructed heterojunction shown a notable enhancement in its photocatalytic activity as a result of the improved efficiency in charge separation at the interface. The application of economically viable solar energy facilitated the complete eradication of harmful pollutants through the process of detoxification. The removal of impurities occurs by a process that follows a first-order kinetics. Among the pollutants, RR141 demonstrates the greatest rate constant at 0.02 min-1, while ofloxacin has a rate constant of 0.01 min-1. The assessment of the stability of the produced photocatalyst was conducted after undergoing five cycles. This study additionally investigated the influence of sunshine on degradation, uncovering degradation rates of 97% for RR141 and 99% for ofloxacin when exposed to UV Lamp, and degradation rates of 97% for RR141 and 95% for ofloxacin when exposed to Solar Light.

Synthesis and characterization of faujasite zeolite membrane for selective enrichment of Arthrobacter sp. in synthetic wastewater.

This paper centers on the preparation and characterization of both a clay support and a faujasite zeolite membrane. Additionally, the study explores the development of bacterial media to assess the performance of these prepared membranes. The faujasite zeolite membrane was created using the hydrothermal method, involving the deposition of a faujasite layer to fine-tune the pore sizes of the clay support. The clay supports were crafted from clay which was sieved to particle size Φ ≤ 63 μm, and compacted with 3.0 wt.% activated carbon, then sintered at 1,000 °C. Distilled water fluxes revealed a decrease from 1,500 L m-2 h-1 to a minimum of 412 L m-2 h-1 after 180 min of filtration. Both membranes were characterized by XRF, XRD, FTIR, adsorption-desorption of nitrogen (N2), and SEM-EDS. PCR technique was used for the identification of the isolated Arthrobacter sp., and the retention of the bacteria on the clay support and the faujasite zeolite membrane were found to be 96 and 99%, respectively. The results showed that the faujasite zeolite membrane passed the clay support due to a narrow pore size of the faujasite zeolite membrane of 2.28 nm compared to 3.55 nm for the clay supports.

Development of Ti3C2Tx‐based novel immunosensor for cancer biomarker detection

In this study, an ultrasensitive label‐free electrochemical immunosensor based on Ti3C2Tx (Mxene) with a 2D‐layered morphology has been proposed for the detection of EpCAM antigen. A hydrothermal method is employed for the synthesis of Ti3C2Tx by using a less toxic exfoliating reagent, NaBF4. The bioelectrode, BSA/anti‐EpCAM/Ti3C2Tx@ITO, has been fabricated by electrophoretic deposition of Ti3C2Tx onto the ITO electrode, followed by an immobilization of EpCAM antibody. Electrochemical response studies reveal that the immunosensor shows a high sensitivity of 29.22 μA fg−1 ml cm−2 and a wide linear range from 0.1 fg/ml to 100 ng/ml, for EpCAM antigen detection. Further, the good stability of this fabricated immunosensor is an additional advantage for EpCAM antigen detection in serum samples.

Sustainable carbon dots from Borreria hispida: enhanced colorimetric sensing of Fe3+ ions and biological applications in live cell imaging.

This study presents the synthesis of advanced nanomaterials derived from the hedge-grown herbal plant, Borreria hispida, and explores their environmental and biological applications. Using a one-step hydrothermal synthesis method, carbon dots derived from Borreria hispida (BHCD) were fabricated and thoroughly characterized through XRD, TEM, FTIR, CHNS, UV-visible, and PL spectroscopy analyses. Under UV illumination, these plant-based carbon dots demonstrated exceptional water solubility, notable photo stability, and a high quantum yield of 40.8%. The average particle size of BHCD was absorbed around 0.5 to 3.5 nm, contributing to superior selectivity and sensitivity in detecting Fe3+ ions, with a limit of detection of 1.2 × 10-6 M. Investigation into the sensing mechanism revealed a binding model wherein two carbon atom molecules bind to one Fe3+ atom in a 2 : 1 ratio for BHCDs and Fe3+ interactions. Additionally, the effectiveness of the developed fluorescent probe for Fe3+ detection was validated using real water samples from ponds and lakes, highlighting its potential for environmental monitoring applications. Furthermore, the biological effects of BHCD were evaluated through cytotoxic assays, demonstrating significant inhibitory effects on MCF7 breast cancer cell lines, with a maximum cell viability of 60%. This research underscores the multifaceted potential of BHCD in environmental monitoring and biomedical applications.