Hydrothermal Synthesis Process Research Articles

Effect of Adding Phosphorus on Crystal Structure of W-V-Nb Complex Oxide and Catalytic Selective Oxidation of Acrolein.

The changes in the crystal structure of the W-V-Nb complex oxide with phosphorus addition to the hydrothermal synthesis process are investigated. The effect of the constituent units and crystal structure of phosphorus-added W-V-Nb complex oxide catalysts on the activity and selectivity for selective oxidation of acrolein is discussed. Phosphorus addition to the hydrothermal synthesis process promotes the formation of orthorhombic and trigonal W-V-Nb complex oxides. Orthorhombic and trigonal W-V-Nb complex oxide catalysts give higher acrylic acid selectivity in acrolein oxidation compared to poorly crystalline catalysts that only have {M6O21} pentagonal units and 7-membered rings.

Stratified nanoflower bimetallic cobalt/iron alloy derived from CoFe-MOFs as efficient peroxymonosulfate activator for antibiotics degradation: Performance, mechanism, and toxicity

Co-based metal-organic framework (Co-MOFs) derivative has gained wide attention in the field of advanced oxidative processes (AOPs). However, the degradation efficiency of single cobalt element remains suboptimal and its activation mechanism still needs to be further explored. In this study, stratified nanoflower bimetallic cobalt/iron alloys (CoFe-NC), derived from cobalt/iron bimetallic-organic frameworks (CoFe-MOFs), was synthesized via self-assembly at room temperature, hydrothermal synthesis and high-temperature carbonization processes and their performance as efficient activators of peroxymonosulfate (PMS) for the degradation of antibiotics was evaluated (removal efficiency of 100 % within 40 min, k=0.0951 min−1). The excellent degradation property benefit by specific nano-flowers structure with high specific surface area (424.67 m2/g), the cycle between Co0→Co2+↔ Co3+ and Fe0→Fe2+↔Fe3+, synergistic effect of Co and Fe bimetals. Furthermore, the CoFe-NC/PMS system exhibits exceptionally high cyclic stability (over 85 % degradation efficiency after four times degradation), a wide range of pH (3−11) and resistance to background ion interference (Cl–, H2PO4–, NO3–, HCO3– and HA), and reduced toxicity of the degradation products. Degradation mechanistic studies demonstrated that the activation of PMS by CoFe-NC generated amounts of reactive oxygen species (ROS) (SO4•−, •OH, •O2− and 1O2). Additionally, high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis identified fifteen intermediate degradation products and three possible degradation pathways were proposed. The results highlight the potential of CoFe-NC as a catalyst for antibiotic removal, providing insights into the optimization of bimetallic-organic framework for environmental applications.

Ionic liquids-assisted integration of biobased materials for sustainable elaboration of nanocomposites using hydroxyethyl cellulose and interlayered clay for efficient separation of Co(II) from multi-component mixtures

This study focuses on the development of eco-friendly biobased adsorbents through a sustainable hydrothermal and freeze-drying synthesis process, utilizing cost-effective bio-sourced materials to minimize energy consumption and waste. The biobased adsorbents were elaborated using hydroxyethyl cellulose-ionic liquids and bentonite clay. The elaborated biocomposites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy/attenuated total reflection (FTIR/ATR), thermogravimetric analysis (TGA), and electron microscopy-energy dispersive X-ray (SEM–EDX), Brunauer–Emmett–Teller (BET) and zeta potential (ZP). Structural analysis confirms the intercalation and incorporation of HEC-ILs polymeric chains into Be-Na matrix and the formation of biocomposites. The [HEC-ILs/Be-Na] composite was subsequently employed for solid-phase extraction of Co(II) by investigating the effect of pH, initial Co(II) concentrations, time, temperature, and the presence of co-existing ions (Na(I), Li(I), Mn(II), Ni(II), and Al(III)). The adsorption kinetics of Co(II) metal ions were suitably characterized using the pseudo-second-order model (with R2 > 0.99). Furthermore, the adsorption isotherms conformed to the Langmuir model (with R2 > 0.97), suggesting a chemisorption process with an adsorption capacity of 69.8 mg/g. The thermodynamic study reveals that the adsorption process exhibits characteristics of spontaneity and endothermicity (ΔH° = 74.197 kJ mol−1, ΔG° < 0 kJ mol−1). The proposed mechanism for Co(II) adsorption on the developed biocomposite involves electrostatic interactions, ion exchange, and anion-π interactions. The biobased composite exhibited remarkable selectivity for Co(II) and demonstrated great potential as an adsorbent for industrial applications.Graphical abstract

Optimized energy storage with hydrothermally synthesized metal sulfide nanocomposite electrodes

Supercapacitors exhibit impressive energy storage capabilities, providing high power density and quick charge/discharge cycles across various applications, including electronics and renewable energy systems. Molybdenum disulfide (MoS2) plays a crucial role in enhancing supercapacitor performance through its high surface area, conductivity, and electrochemical stability. Recent reports have shown that manipulating phase transitions and incorporating dopants or substitutions can significantly enhance the performance of 2D materials. The present study investigated the influence of tungsten substitution on the phase changes and electrochemical properties of MoS2. The hydrothermal synthesis process involved the substitution of tungsten with different concentration, leading to a notable phase change from 2 H to 1 T, as confirmed by X-ray diffraction (XRD) analysis. Morphological studies using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) revealed modifications in the morphological structure. The electrochemical performance of pristine MoS2 and MoS2/WS2 composites were evaluated using cyclic voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS). The determined specific capacitances of MoS2/WS2 composites exhibited higher values compared to pristine MoS2. Specifically, the sample with 15 mol% tungsten addition demonstrated a maximum specific capacitance of 333 F g−1, surpassing that of pristine MoS2 and other samples at a current density of 1 A g−1. This research provides valuable insights into the phase-dependent electrochemical behaviour of MoS2 with tungsten substitution, offering a better understanding of its potential for applications in high-performance energy storage devices.

The excellent anti-wear and friction-reducing performance of magnesium silicate hydroxide/graphite nanocomposite (MSH-C) as a lubricant additive

Abstract In this paper, MSH-C and MSH-GO composites were prepared by doping MSH with micron-sized few-layer graphene oxide (∼10 um) and nanoscale graphite (∼300 nm), respectively, during the hydrothermal synthesis process. Octadecyltrimethoxysilane (ODTMS) was used as a surfactant to disperse these two types of additives into the fully formulated oil. Tribological tests demonstrated that MSH-C exhibits much more superior tribological properties when compared to MSH-GO. The findings reveal that the oil sample containing 0.5 wt% MSH-C can effectively reduce wear volume (by approximately 26.4%) as compared to fully formulated oil and that the friction coefficient is decreased to ∼0.02. SEM, Raman, FIB-TEM, and TOF-SIMS characterizations and molecular dynamics simulation were used to investigate the tribological mechanism. A tribo-film composed of two layers of different compositions was formed on the worn surface of MSH-C, indicating the synergistic effect of MSH and graphite.

Porous Structure Fibers Based on Multi-Element Heterogeneous Components for Optimized Electromagnetic Wave Absorption and Self-Anticorrosion Performance.

The excellent performance of electromagnetic wave absorbers primarily depends on the coordination among components and the rational design of the structure. In this study, a series of porous fibers with carbon nanotubes uniformly distributed in the shape of pine leaves are prepared through electrospinning technique, one-pot hydrothermal synthesis, and high-temperature catalysis method. The impedance matching of the nanofibers with a porous structure is optimized by incorporating melamine into the spinning solution, as it undergoes gas decomposition during high-temperature calcination. Moreover, the electronic structure can be modulated by controlling the NH4F content in the hydrothermal synthesis process. Ultimately, the Ni/Co/CrN/CNTs-CF specimen (P3C NiCrN12) exhibited superior performance, while achieving a minimum reflection loss (RLmin) of -56.18dB at a thickness of 2.2mm and a maximum absorption bandwidth (EABmax) of 5.76GHz at a thickness of 2.1mm. This study presents an innovative approach to fabricating lightweight, thin materials with exceptional absorption properties and wide bandwidth by optimizing the three key factors influencing electromagnetic wave absorption performance.

Exploring B‐site Doping in LaFeO3 Perovskites for Superior ORR Performance in Acidic and Alkaline Conditions

AbstractIn recent times, perovskite oxides have recognized to be an ideal alternative to platinum‐based oxygen reduction reaction (ORR) electrocatalysts due to their excellent stability, cost‐effectiveness, and tailorable properties. Herein, an ABO3 type LaFeO3 perovskite was doped at its B‐site to form electrochemically active LaFeB′O6 (B′=Cr, Zn, Co) by one‐pot hydrothermal synthesis process. Due to the synergistic effects of increased surface area and electrochemically active sites, Cr‐doped LaFeO3 largely improves the mass transfer kinetics for ORR in both conditions, alkaline (0.1 M KOH) and acidic (0.5 M H2SO4) with a positive onset Eon of 0.80 and 0.81 V (vs Ag/AgCl). Similarly, a half‐wave (E1/2) potential of 0.68 and 0.63 V (vs Ag/AgCl), which was comparable to the commercial 20 % Pt/C. Moreover, the La‐based perovskites were able to catalyze ORR with an electron transfer number (n)&gt;3.6 signifying the superior 4‐electron pathway. Doped and undoped LaFeO3 exhibited remarkable stability in the chronoamperometry studies with a relative current of 92–95 % sustained over 8 h. Additionally, the La‐based electrocatalysts was unaffected by the crossover effect of methanol in both acidic and basic conditions, contrary to the commercial 20 % Pt/C. The present work serves as a useful strategy to maximize the efficiency and reliability in perovskites for energy‐related electrocatalytic applications and for alternative fuel generation.

Facile synthesis of NH2-MIL-53(Al)@BiOBr@CQDs ternary heterostructure photocatalyst for degradation of ciprofloxacin in water

The construction of ternary heterojunction photocatalysts can achieve multi-gradient transfer of charges and accurate control the position of photogenerated electrons which has received increasing attention. In this paper, NH2-MIL-53(Al)@BiOBr@CQDs-10 % (ABCQDs-10 %) was prepared via a facile hydrothermal and chemical synthesis processes. Three-dimensional serration of NH2-MIL-53(Al) as a platform for irregular BiOBr nanosheets, CQDs promote interfacial contact and act as electron transport channels between BiOBr and NH2-MIL-53(Al) and constitute Z-type heterojunctions with high redox properties. ABCQDs-10 % shows the best photocatalytic removal efficiency (94.24 %) of CIP, the reaction rate constants (0.045 min−1) were 1.2 and 64 times higher than BiOBr and NH2-MIL-53(Al), respectively. The excellent degradation performance is attributed to the construction of Z-type heterojunction of NH2-MIL-53(Al)@BiOBr@CQDs which improve electron-hole separation and transfer efficiency. The main active species was •O2-. The photocatalytic activity of ABCQDs-10 % had not obvious loss after cycle experiments and the crystal structure had no significant changes, means high stable photocatalytic activity.

Continuous flow hydrothermal synthesis of MoVNbTeOx in micro-coil tubular reactor for oxidative dehydrogenation of ethane

MoVNbTeOx is the most promising catalyst for the oxidative dehydrogenation of ethane (ODHE) process, which is usually prepared by hydrothermal methods. However, the synthesis of MoVNbTeOx is time-consuming and sensitive to the homogeneity of the synthesis environment, which limits its preparation reproducibility and large-scale accessibility. In this work, a continuous flow hydrothermal synthesis (CFHTS) process for the preparation of MoVNbTeOx catalysts was developed and the synthesis parameters were screened using a tubular reactor. Using a micro coil tube as a reactor, MoVNbTeOx catalysts can be synthesized rapidly at 300 °C and 10 MPa. Meanwhile, the catalytic performance of MoVNbTeOx synthesized by CFHTS method was also significantly improved, with the activity nearly doubled compared to the samples prepared by the conventional method. Compared with the conventional method, the preparation time of CFHTS method can be shortened from 48 h in the batch mode to 10 min in the continuous mode, and the capacity per unit volume of the reactor has been increased by orders of magnitude, which provides the possibility of industrial scale-up of MoVNbTeOx catalysts.

Synthesis of Al-enriched beta zeolite nanocrystals by using DABCO di-cationic quaternary ammonium as organic structure directing agent

Al-enriched Beta zeolite nanocrystals with densely populated acid sites and enhanced mass transfer efficiency have been demonstrated to show promising catalytic performance. In this work, low Si/Al ratio (8–9) Beta nanocrystals (about 20 nm) was synthesized by using DABCO based di-cationic quaternary ammonium salts as organic structure directing agent with high solid yield (＞95 %). The hydrothermal synthesis process was followed by monitoring the intermediate products at different time intervals, through which the key role of the di-cationic quaternary ammonium for the formation of Beta nuclei was identified. The promising catalytic performance of the Al-rich Beta nanocrystals in 1,3,5-triisopropylbenzene transalkylation with benzene was attributed to the high density and enhanced accessibility of acid sites.

Hydrothermally Synthesized Bi-Doped CdTe Nanoparticles with Tunable Optical and Photoresponse Properties for Visible Photodetectors.

The remarkable applicability and unique properties of CdTe nanoparticles make them vital in various applications such as optoelectronics and photovoltaics. It has been demonstrated that adding a metal dopant to a nanomaterial matrix significantly improves its characteristics, increasing its potential for a variety of applications. In this work, a simple hydrothermal synthesis process for bidoped CdTe nanoparticles is reported, wherein four distinct samples are generated by adjusting the concentration of Bi doping. Structural analysis using X-ray diffraction (XRD) confirmed the presence of the CdTe cubic phase in the material with observable phase shifts due to Bi incorporation. Rietveld refinement of the XRD results further enabled a detailed structural analysis. Raman spectroscopy provided insights into the different vibrational modes of CdTe, while transmission electron microscopy analysis further elucidated the CdTe phase and determined interplanar spacing values. Morphological examination via field emission scanning electron microscopy revealed a consistent nanoparticle-like morphology, unaffected even by increased Bi concentration. Elemental analysis conducted through inductively coupled plasma mass spectrometry offered valuable insights into the composition of the material. Furthermore, UV-vis analysis revealed a decrease in the bandgap, indicating potential shifts in the material's optical properties. Notably, the photoresponse study demonstrated an increase in current value, as well as alterations in the rise and decay times of the material. These properties highlight its potential for various optical and electrical applications. Overall, these findings underscore the promising prospects of bidoped CdTe nanoparticles in various advancements.

Structure-modulation of flower-like VS2 via ammonium ion intercalation for high performance potassium-ion batteries

Transition vanadium sulfide is a promising anode material for potassium-ion batteries (PIBs), but the volume variation during charge-discharge cycling and low electric conductivity seriously hinder its applications. Herein, we designed a multilayer lamellar self-assembled flower-like vanadium sulfide with ammonium ion intercalation (VS2–NF) by a facile and inexpensive hydrothermal method to improve its electrochemical potassium ion storage performance. By introducing ammonia during the hydrothermal synthesis process, the structures of vanadium sulfide transformed to nanoflowers composed by ultrathin nanosheets from the initial nanosphere structures. The intercalation of ammonium ion enlarges the lattice fringes and induces anisotropic growth of vanadium sulfide, resulting in a large number of mesopores and increased specific surface area as well as the reactive sites of vanadium sulfide, which contribute to the enhanced potassium ion storage performance. Consequently, the structure-modulated VS2–NF exhibits a high specific capacity of 507 mAh g−1 after 50 cycles at a current density of 100 mA g−1. This approach provides a new routine for the modification of other transition metal disulfides as anode materials for PIBs.

Morphology and Microstructural Optimization of Zeolite Crystals Utilizing Polymer Growth Modifiers for Enhanced Catalytic Application

Rationally controlling the morphology and microstructure of the zeolite crystals could play a significant role in optimizing their physicochemical properties and catalytic performances for application in various zeolite-based heterogeneous catalysis processes. Among different controlling strategies, the utilization of zeolite growth modifiers (ZGMs), which are molecules capable of altering the anisotropic rates of crystal growth, is becoming a promising approach to modulate the morphology and microstructural characteristics of zeolite crystals. In this mini-review, we attempt to provide an organized overview of the recent progress in the usage of several easily available polymer-based growth modifiers in the synthesis of some commonly used microporous zeolites and to reveal their roles in controlling the morphology and various physicochemical properties of zeolite crystals during hydrothermal synthesis processes. This review is expected to provide some guidance for deeply understanding the modulation mechanisms of polymer-based zeolite growth modifiers and for appropriately utilizing such a modulation strategy to achieve precise control of the morphology and microstructure of zeolite crystals that display optimal performance in the target catalytic reactions.

Fabrication of methylated carbon quantum dot-based fluorescent films for highly sensitive and stable temperature probes

Due to their distinct physicochemical characteristics and outstanding biocompatibility, carbon quantum dots have shown to offer enormous potential in the field of temperature sensing. However, there is still much to learn about the mechanism underlying carbon quantum dots' thermal sensing capabilities, and developing incredibly precise thermometers based on it is still an enormous obstacle. Herein, we successfully fabricated carbon quantum dots with variable luminescence wavelength and temperature-sensitive properties by adjusting the ingredients to modify the composition of functional groups (-NH2, -OH, -COOH and -CH2OH) on the surface of quantum dots in a simple hydrothermal synthesis process, followed by encapsulation with polyvinyl alcohol (PVA). Subsequently, structural/optical characterisation and temperature-dependent studies were utilized for investigations into the quantum dot fluorescence mechanisms as well as the thermal sensing characteristics connected to surface functional groups, respectively. Notably, the designed red-emitting methylenated carbon quantum dot film probe displayed more linear segmented temperature sensing properties (R2>0.99), a wider temperature applicability range (20–160 °C), and high temperature reversibility (20–80 °C, at least 4 cycles). Finally, the mechanism by which functional groups affect the thermal characteristics of carbon quantum dots was addressed, and we hypothesized that intramolecular and intermolecular hydrogen bonding interactions are important factors affecting the thermal properties of carbon dots. This work presents great promise and theoretical guidance for the development of highly reliable carbon quantum dot temperature sensing systems.

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

Fabricating waxberry-shaped N–C–TiO2 composite with excellent visible light catalytic activity

Herein, a nitrogen, carbon co-doped anatase and rutile double-phase waxberry-shaped [Formula: see text] composite photocatalyst is prepared with the one-step simple hydrothermal synthesis process, in which P25 was used as the precursor, and urea as the source of nitrogen and carbon. A suitable valence band position (2.52 eV) is provided by [Formula: see text], with more active species (e.g. [Formula: see text], [Formula: see text], •[Formula: see text] and •[Formula: see text]) being formed on the active catalysis surface, which is helpful to the redox reaction. Further comparison of experimental results ([Formula: see text] = 3.01 eV) proved that the novel [Formula: see text] has preferable photocatalytic activity. In this study, an ingenious nitrogen- carbon co-doping structure was designed for the improvement of [Formula: see text] photocatalytic performance, which is much for reference of this method to other photocatalyst designs.

A novel approach for the facile synthesis of zinc oxide/carbon hybrid systems from corn distillers soluble: Surface modification and characterization for sustainable remediation

Sustainable, efficient, and environmentally friendly ways to tailor the carbonaceous materials from bio sources with desired functionalities remain a challenge around the world. In this study, we represent a novel approach to synthesize carbon hybrid material based on Zinc Oxide/carbon (ZnO/C) hybrid systems by catalytic hydrothermal process via crosslinking reaction through nucleation and growth of ZnO particles at the functional groups of oxidized carbon material. This research explored the volarization of Condensed Corn Distillers Soluble (CDS) as a carbon precursor to synthesize biobased carbon spheres. Surface modification of the produced carbon spheres took place using zinc chloride (ZnCl2) during hydrothermal carbonization (HTC). Zinc chloride (ZnCl2) was used to function as a catalyst during HTC and functioned as a ZnO source to synthesize (ZnO/C) hybrid systems. Design Expert software v13 was used to design the hydrothermal carbonization (HTC) experiments and response surface methodology was used to find the optimized conditions for the preparation of carbon hybrid systems. The hydrothermal synthesis process introduced 3D stone like zinc oxide particles onto the carbon matrix. These particles were self-assembled onto the carbon framework to produce carbon hybrid systems with unique physical, chemical, structural and functional properties. Herein, the obtained carbon hybrid systems (ZnO/C) were investigated and discussed in detail. ZnO/C hybrid systems were analyzed for surface morphology using scanning electron microscopy (SEM) that presented a 3D spherical interconnected phase and XRD analyses were used for phase crystallinity that showed new crystalline phases such as hopeite and zincite after the ZnCl2 incorporation. Surface functional groups were also analyzed by FTIR and results confirmed the presence of hydrophilic groups such as –OH, CC, and COOH on the surface of ZnO/C hybrid carbon systems. This study provided the insightful guidance for tailoring novel design of multifunctional carbon material as an adsorbent/catalyst for various applications of sustainable remediation.

Hybrid-Mechanism Synergistic Flexible Nb2O5@WS2@C Carbon Nanofiber Anode for Superior Sodium Storage.

Sodium-ion batteries (SIBs) have demonstrated remarkable development potential and commercial prospects. However, in the current state of research, the development of high-energy-density, long-cycle-life, high-rate-performance anode materials for SIBs remains a huge challenge. Free-standing flexible electrodes, owing to their ability to achieve higher energy density without the need for current collectors, binders, and conductive additives, have garnered significant attention across various fields. In this work, we designed and fabricated a free-standing three-dimensional flexible Nb2O5@WS2@C carbon nanofiber (CNF) anode based on a hybrid adsorption-intercalation-conversion mechanism of sodium storage, using electrospinning and hydrothermal synthesis processes. The hybrid structure, aided by synergistic effects, releases the advantages of all materials, demonstrating a superior rate performance (288, 248, 211, 158, 90, and 48 mA h g-1 at the current density of 0.2, 0.5, 1, 2, 5, and 10 A g-1, respectively) and good cycling stability (160 mA h g-1 after 200 cycles at 1 A g-1). This work provides certain guiding significance for future research on hybrid and flexible anodes of SIBs.

Electrical and structural engineering of nanoflower-like NiMn-layered double hydroxide by V modulation for high-performance hybrid supercapacitors

This work produced V-doped NiMn-layered double hydroxide(V-NiMnLDH) composite positive electrode material directly on nickel foam using a simple one-step hydrothermal synthesis process. The composite's 3D nanoflower-like design increased spatial utilization, surface area, and active sites for Faradaic redox reactions. The composite material has a specific capacitance of 1551 F g−1 at 1 A g−1 and 85.6 % capacitance retention at 10 A g−1, demonstrating exceptional cycle stability. In addition, we combined V-NiMnLDH with commercial activated carbon to create an asymmetric supercapacitor (ASC) with 63.5 Wh kg−1 energy density and 975 W kg−1 power density. After 5000 charge-discharge cycles, the gadget preserved 89.7 % of its specific capacitance. This material outperforms similar electrode materials in certain performance evaluations. We also used density functional theory (DFT) computations to analyze each element in the V-NiMnLDH composite and explain their electronic density of states contributions. This theoretical framework explains how V doping improves capacitance. Band structure simulations also showed V-NiMnLDH's higher charge transfer and conductivity compared to intermediate products, explaining its extraordinary capacitance performance. Our work combines theoretical and experimental data to advance catalyst design and high-performance energy storage materials.

A novel approach to Hg2+ determination in water samples using carbon dots based on paper and fluorescence digital image analysis

AbstractBACKGROUNDThis work proposes the use of a simple, inexpensive method for the hydrothermal synthesis of fluorescent carbon dot nanoparticles (CDs) from rice starch aimed at the determination of Hg2+ in water. The proposed method involved using a paper‐based analytical device coupled to a 3D plate, with a UV‐LED chamber and a smartphone for the acquisition and analysis of the fluorescence digital images of the CDs.RESULTSThe size of the carbon dots ranged from 0.5 to 3 nm, with an average particle size of ~1 nm. The functionalization of carbon dots with methimazole allowed a high selective for Hg2+ determination. The results obtained showed a linear response R2 of 0.997 and Hg2+ concentration in the range of 0.5–45.0 μmol L−1 with a limit of detection and limit of quantitation of 0.23 and 0.62 μmol L−1, respectively. The results of the study show that there were no significant differences, at 95% confidence level, between the data obtained from the application of the proposed method and the reference method.CONCLUSIONThe proposed method is in line with the principles of green chemistry, as it involves the use of renewable sources for starch extraction and a hydrothermal synthesis process that does not employ toxic reagents. In addition, the method employs only 15 μL reagent/sample. © 2024 Society of Chemical Industry (SCI).