Hydrothermal Decomposition Method Research Articles

Green synthesis of Zn-doped TIO2 nanoparticles from Zanthoxylum armatum

Green synthesis is an easy, safe, and environmentally beneficial nanoparticle creation method. It is a great challenge to simultaneously improve the capping and stabilizing agent carrier separation efficiency of photocatalysts. Herein, Zn-doped Titanium dioxide (TiO2) nanoparticles with high exposure of 360 nm using a UV/visible spectrophotometer were prepared via a one-step hydrothermal decomposition method. A detailed analysis reveals that the electronic structures were modulated by Zn doping; thus, the responsive wavelength was extended to 600 nm, which effectively improved the visible light absorption of TiO2. We have optimized the different parameters like concentration, time, and temperature. The peak for TiO2 is located at 600 cm-1 in FTIR. A scanning electron microscope revealed that TiO2 has a definite shape and morphology. The synthesized Zn-doped TiO2NPs were applied against various pathogens to study their anti-bacterial potentials. The anti-bacterial activity of Zn-doped TiO2 has shown robust against two gram-ve bacteria (Salmonella and Escherichia coli) and two gram + ve bacteria (Staphylococcus epidermidis and Staphylococcus aureus). Synthesized Zn-doped TiO2 has demonstrated strong antifungal efficacy against a variety of fungi. Moreover, doping TiO2 nanoparticles with metal oxide greatly improves their characteristics; as a result, doped metal oxide nanoparticles perform better than doped and un-doped metal oxide nanoparticles. Compared to pure TiO2, Zn-doped TiO2 nanoparticles exhibit considerable applications including antimicrobial treatment and water purification.

Technical Approaches to the Recycling of Reclaimed Asphalt Pavement into Aggregate and Binder

Approximately 99% of reclaimed asphalt pavement (RAP) has been recycled in Japan in recent years. However, the deterioration in quality of repeatedly recycled RAP cannot be prevented through existing methods, nor can sustainability be guaranteed. In addition, it is challenging to procure virgin aggregate and binder. Therefore, to ensure the quality and supply of future recycled hot-mix asphalt, it is necessary to explore sustainable recycling technologies. This study examined the advantages and disadvantages of the technical approaches to the recycling of RAP into aggregate and binder. We develop a recycling technology (separate recycling technologies) that uses hot water to separate and restore aggregate and binders to their initial condition from RAPs. The quality of the aggregate, recovered by the hot water rubbing method at 80 °C and 90 °C, fully satisfies the standard values for virgin aggregate at all temperatures. The aged binders, reacting through a hydrothermal decomposition method (hydropyrolysis), with a reaction temperature of 300–350 °C and a reaction time of 0–15 min, tend to have a significantly improved effect. These results confirm that both the hydrothermal rubbing and hydropyrolysis methods could be beneficial options for establishing separate recycling technologies for RAP.

Ultra-stable oxygen species in Ag nanoparticles anchored on g-C3N4 for enhanced electrochemical reduction of CO2

Oxide-derived silver catalysts containing stable oxygen species have been proved to be efficient for the electrochemical reduction reaction of CO2 (CO2RR) due to their enhanced binding energy to *COOH intermediate. Here we developed a hydrothermal decomposition method to synthesize silver nanoparticles (NPs) supported on carbon nitride (Ag/g-C3N4) from silver oxide (Ag2O) precursor. The obtained Ag/g-C3N4 electrocatalyst is capable of producing CO at a low onset overpotential (190 mV), and exhibits a high Faraday efficiency (FE) up to 94.0% at –0.7 V vs RHE along with a mass activity of 45.7 mA/mg. The improved electrochemical performance is attributed to the ultra-stable oxygen species derived from the incomplete decomposition of Ag2O and coexisted with Ag NPs in the final Ag/g-C3N4 composite. The presence and durability of oxygen species were verified from transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Ag MNN Auger spectra, and temperature-programmed reduction (TPR) measurements. The strong interaction between Ag NPs and g-C3N4 substrate via the Ag-N bonding alters the rate-determining step (RDS) of CO2RR from the electron transfer (CO2 to*CO2•− ) to the proton transfer (*CO2•− to *COOH) process.

Study on Denitration Performance of Solid Waste Blast Furnace Slag Catalysts under Different Preparation Processes.

In this article, blast furnace slag, a high-yield industrial solid waste, was taken as the research object and it was used as the main material. Bentonite was used as the binder, and water was added to shape the blast furnace slag into a small column. The denitration catalyst was prepared using different methods, its denitration performances were compared and analyzed, and the best preparation method and process parameters were screened. Results showed that bentonite will clearly improve denitration performance, and 4:1 blast furnace slag and bentonite was selected as the molding ratio to reduce the effect of bentonite on its performance, combined with the hardness and surface adhesion of the prepared carrier. Separately, the catalysts were prepared using citric acid impregnation, hydrothermal decomposition, and mixing method, and active Mn was loaded. Among them, the hydrothermal decomposition method cannot completely decompose in a closed kettle, resulting in a lower denitration performance. The catalyst prepared using the mixing method is superior to that prepared using the impregnation method because the active component prepared by the former was more uniformly dispersed, and simple and easy to operate, which can meet the needs of the excess denitration catalysts of small enterprises.

Well-dispersed Pt nanodots interfaced with Ni(OH)2 on anodized nickel foam for efficient hydrogen evolution reaction

Hindered by price and scarcity, the exploitation of supported Pt-based electrocatalysts with Pt single atoms or Pt nanoclusters is an alternative way to decrease the dosage of Pt and improve the electrocatalytic performance for hydrogen evolution reaction (HER) of water splitting. The anodization technology is used to modify the surface of nickel foam (NF) to form the porous NiF2 network structure. Then Pt nanodots interfaced with Ni(OH)2 (Pt/Ni(OH)2) hybrid on the anodized NF has been in-situ synthesized by a simple hydrothermal decomposition method. Results show that Pt nanodots on the substrate have good dispersion with the average size of 3 nm, and the Pt loading is only 0.229 mg cm−2. The prepared electrode exhibits the low overpotentials of 25.9 mV and 211 mV at the current densities of 10 and 100 mA cm−2, respectively, a small Tafel slope of 37.6 mV dec−1, and the excellent durability for HER. The porous network nanostructure of Pt/Ni(OH)2 hybrid, the large electrochemical surface area, the fast facilitated electron transport capability, and the firm adhesion of Pt nanodots with the anodized NF substrate contribute to the remarkable performance towards HER.

High performance plasmonic activation of Ag on β-Ag2WO4/BiVO4 as nanophotocatalyst for oxidation of alcohols by incident visible light

A new and high efficient ternary Ag on β-Ag2WO4/BiVO4 as a visible light driven nanophotocatalyst toward oxidation of alcohols was synthesized by the ultrasonic irradiation in combination with hydrothermal decomposition method. This photosensitive catalyst was characterized using FT-IR, FE-SEM imaging, TEM, EDS, XRD, XPS, UV–vis, PEC and PL techniques. The photocatalytic performance of this nanocomposite is more than 90% conversion that significantly is higher than either pure Ag/β-Ag2WO4 or BiVO4 nanoparticles. This such high activity is related to efficient charge separation that could be contributed to the fast charge transfer on the Ag/β-Ag2WO4. This surface plasmon resonance effect is due to the creation of Ag(0) on the surface of Ag2WO4, which causes narrow band gap which accelerates effective energy transfer. Also, the mechanistic study reveals that positive holes and hydroxyl radicals have the most influence on the oxidation reaction progress. Upon reusing of this heterogeneous photocatalyst for seven times no significant loss of activity was detected. In addition, this reusable and robust photocatalyst has high activity and selectivity under visible light using mild oxidant H2O2 at ambient temperature.

A fluorescence probe based on the nitrogen-doped carbon dots prepared from orange juice for detecting Hg2+ in water

An excellent biocompatible nitrogen-doped carbon dots (N-CDs) was successfully synthesized from orange juice and ethylenediamine by hydrothermal decomposition method. The as-prepared N-CDs were mono-dispersed spherical nanoparticles with a narrow size distribution of 0.5–3.0nm and showed a good dispersion and stability in aqueous solution with the pH value ranging from 3.0 to 13.0. Photoluminescence spectra of as-prepared N-CDs demonstrated that the fluorescence intensity of N-CDs was increased with the doped nitrogen atoms and the FL-QY (fluorescence quantum yield) of N-CDs was up to 31.7%. Compared with Gly-CQDs(CQDs synthesied by Gly), which were prepared from chemical carbon source via hydrothermal decomposition method, the as-prepared N-CDs showed much lower cytotoxicity for Human THP-1 macrophage cells. These results indicated N-CDs prepared by our proposed method have excellent compatibility and more suitable for the application in biolabeling and bioimage. Due to the fluorescence quenching of N-CDs by mercury (II) ion (Hg2+), a sensitive and selective method was developed for detecting Hg2+. The results indicated that the fluorescence intensity ratio of N-CDs was proportional to the concentration of Hg2+ in the range from 4.0μg/mL to 32.0μg/mL and the recovery of spiked samples was ranged from 102.0% to 103.0%, which hinted our proposed method has a good sensitivity and accuracy and was suitable for detecting Hg2+ with satisfactory in tap water.

Superior photocatalytic, electrocatalytic, and self-cleaning applications of Fly ash supported ZnO nanorods

Ever growing research on modified semiconductor oxides made a significant progress in catalytic functional materials. In this article, we report the modification of ZnO photocatalyst by a simple hydrothermal decomposition method utilizing the cheaply available industrial waste fly ash. This modified Fly ash-ZnO photocatalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), Atomic force microscopy (AFM), photoluminescence spectroscopy (PL) and diffuse reflectance spectroscopy (DRS). The XRD pattern indicates the presence of fly ash components and the hexagonal wurtzite structured ZnO. TEM images reveal well defined nanorod like structure. Reduction of photoluminescence intensity of Fly ash-ZnO at 418 nm, when compared to, prepared ZnO, indicates the suppression of recombination of the photogenerated electron–hole pair by loaded Fly ash on ZnO. Fly ash-ZnO exhibits enhanced photocatalytic activity for the degradation of azo dyes Reactive Orange 4, Rhodamine-B and Trypan Blue. This catalyst shows higher electrocatalytic activity than ZnO in the oxidation of methanol. Significant hydrophobicity of Fly ash-ZnO reveals its self cleaning property.

Vanadium Pentoxide Nanobelt-Reduced Graphene Oxide Nanosheet Composites as High-Performance Pseudocapacitive Electrodes: ac Impedance Spectroscopy Data Modeling and Theoretical Calculations.

Graphene nanosheets and graphene nanoribbons, G combined with vanadium pentoxide (VO) nanobelts (VNBs) and VNBs forming GVNB composites with varying compositions were synthesized via a one-step low temperature facile hydrothermal decomposition method as high-performance electrochemical pseudocapacitive electrodes. VNBs from vanadium pentoxides (VO) are formed in the presence of graphene oxide (GO), a mild oxidant, which transforms into reduced GO (rGOHT), assisting in enhancing the electronic conductivity coupled with the mechanical robustness of VNBs. From electron microscopy, surface sensitive spectroscopy and other complementary structural characterization, hydrothermally-produced rGO nanosheets/nanoribbons are decorated with and inserted within the VNBs’ layered crystal structure, which further confirmed the enhanced electronic conductivity of VNBs. Following the electrochemical properties of GVNBs being investigated, the specific capacitance Csp is determined from cyclic voltammetry (CV) with a varying scan rate and galvanostatic charging-discharging (V–t) profiles with varying current density. The rGO-rich composite V1G3 (i.e., VO/GO = 1:3) showed superior specific capacitance followed by VO-rich composite V3G1 (VO/GO = 3:1), as compared to V1G1 (VO/GO = 1:1) composite, besides the constituents, i.e., rGO, rGOHT and VNBs. Composites V1G3 and V3G1 also showed excellent cyclic stability and a capacitance retention of >80% after 500 cycles at the highest specific current density. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters, including charge transfer and solution resistance, double layer and low frequency capacitance, Warburg impedance and the constant phase element. The detailed analyses provided greater insights into physical-chemical processes occurring at the electrode-electrolyte interface and highlighted the comparative performance of thin heterogeneous composite electrodes. We attribute the superior performance to the open graphene topological network being beneficial to available ion diffusion sites and the faster transport kinetics having a larger accessible geometric surface area and synergistic integration with optimal nanostructured VO loading. Computational simulations via periodic density functional theory (DFT) with and without V2O5 adatoms on graphene sheets are also performed. These calculations determine the total and partial electronic density of state (DOS) in the vicinity of the Fermi level (i.e., higher electroactive sites), in turn complementing the experimental results toward surface/interfacial charge transfer on heterogeneous electrodes.

ZnO nanoflower-based photoelectrochemical DNAzyme sensor for the detection of Pb2+

Lead contamination is now widespread, and exposure to lead may cause adverse effects on human beings. In this study, a photoelectrochemical sensor based on flower-like ZnO nanostructures was developed for Pb2+ detection, using a Pb2+-dependent DNAzyme as the recognition unit and a double-strand DNA intercalator, Ru(bpy)2(dppz)2+ (bpy=2,2'-bipyridine, dppz=dipyrido[3,2-a:2',3'-c] phenazine) as the photoelectrochemical signal reporter. The ZnO nanoflower was fabricated on an indium tin oxide (ITO) electrode by the convenient hydrothermal decomposition method. The morphology and photoelectrochemical property of the ZnO nanoflowers were characterized by SEM, XRD and photocurrent measurements. DNAzyme-substrate duplex was assembled on an ITO/ZnO electrode through electrostatic adsorption. In the presence of Pb2+, RNA-cleavage activity of the DNAzyme was activated and its substrate strand was cleaved, resulting in the release of Ru(bpy)2(dppz)2+ from the DNA film and the concomitant photocurrent decrease. The detection principle was verified by fluorescence measurements. Under the optimized conditions, a linear relationship between photocurrent and Pb2+ concentration was obtained over the range of 0.5–20nM, with a detection limit of 0.1nM. Interference from other common metal ions was found negligible. Applicability of the sensor was demonstrated by analyzing lead level in human serum and Pb2+ spiked water samples. This facile and economical sensor system showed high sensitivity and selectivity, thus can be potentially applied for on-site monitoring of lead contaminant.

Novel rose-type magnetic (Fe 3O 4, γ-Fe 2O 3 and α-Fe 2O 3) nanoplates synthesized by simple hydrothermal decomposition

Rose-type magnetic nanoplates (RTMNPs) were synthesized by a simple hydrothermal decomposition method where FeCl 2·4H 2O was solely used as a precursor. The synthesized nanoplates were characterized using XRD, FE-SEM, UV–vis absorption (reflectance) spectra and magnetic hysteresis loops. The resulting nanoplates were in the ranges of size 350–500 nm and width 60–70 nm with high crystallinity, purity (shown by XRD) and reproducibility. These iron oxide nanoplates have a great potential in magnetic nanodevices and biomagnetic applications.

A novel synthesis of rose type magnetic (Fe 3O 4, γ-Fe 2O 3 and α-Fe 2O 3) nanoplates by simple hydrothermal decomposition

Rose type magnetic nanoplates (RTMNPs) were synthesized by a simple hydrothermal decomposition method where FeCl 2·4H 2O was solely used as a precursor. Synthesized nanoplates were characterized using XRD, FE-SEM, TEM, UV–vis absorption (reflectance) spectra and magnetic hysteresis loops. The resulting nanoplates were in the range of size 350–500 nm and width 60–70 nm with high crystallinity and purity (shown by XRD). These iron oxide nanoplates and their dispersions in various media have great potential in magnetic nanodevices and biomagnetic applications.

Preparation and Characterization of Cu Nano-Powders by Hydrothermal Decomposition and Hydrogen Reduction Process

In this paper, Cu nano-powder was used to reduce CuO nano-powder by hydrogen reduction process, which was prepared by hydrothermal decomposition method taken CuSO4•5H2O and NaOH as raw materials. The reaction conditions of CuO nano-stick were that concentration of CuSO4 liquor was 0.1mol•L-1, concentration of NaOH liquor was 5mol•L-1, dropping speed was 50ml•min-1, pH value of reacting terminal was 12, stirring speed was 1200 r•min-1, reacting temperature was 60°C, reacting time was 30min. The CuO stick longness was 200nm, diameter was 30nm. The reaction conditions of CuO nano-boll were that dropping speed was 50ml•min-1, pH value of reacting terminal was 7, stirring speed 100 r•min-1, reacting temperature was 80°C, reacting time 30min. The diameter of CuO nano-ball was 50~100 nm. The Cu powder was prepared with materials CuO tick by hydrogen reduction in closed circular system. The higher the temperature, the reaction speed is faster. Hydrogen reduction time was 400s in reacting temperature 240°C. The Cu powder’ size was less than 100nm.

Synthesis of porous manganese oxides bars via a hydrothermal-decomposition method

Porous manganese oxides with regular bar shape were synthesized by a hydrothermal-decomposition method. Uniform bar-shaped precursor was first obtained via a hydrothermal route. After annealing, porous manganese oxides with maintained macroscopic shape were synthesized. X-ray diffractometer (XRD), scanning electron microscope (SEM) and TG-DTA analysis were used to characterize the composition, structure and morphology of the samples. The porous structure was assembled by crystallites with nanosize. It was demonstrated that the annealing temperature and the heating rate play the key function in the formation of the pores. N 2 physisorption results showed that the BET surface area of the manganese oxides annealed at 400 °C was 30.86 m 2 g −1 and the BJH pore size distribution showed a bimodal structure with porosity on the 10 and 100 nm length scales. Macroporous Mn 2O 3 was synthesized at 600 °C and 800 °C. The structure of manganese tartrate was also considered to understand the possible formation mechanism of the regular shape and the porous structure.

Growth mechanism of tubular ZnO formed in aqueous solution

Tubular ZnO microstructural arrays were fabricated by a hydrothermal decompositionmethod. The dependence of the morphologies on the growth time and temperature wasinvestigated in detail. An experiment was carried out to determine the mechanism oftubular ZnO formation. Our results showed that ZnO microtubes originated from an ageingprocess from ZnO microrods at a lower temperature (compared to the temperature whenhydrothermal deposition of ZnO microrods was dominant) due to the preferential chemicaldissolution of the metastable Zn-rich (0001) polar surfaces. A growth model was proposedbased on the coexistence of hydrothermal deposition and dissolution of ZnO in thefabrication process.

Study on a Water and Sludge Treatment Method Using Superconducting Magnetic Separation and Hydrothermal Decomposition

We studied a treatment method on beavy metal separation and sludge decomposition using a superconducting magnetic separation and a hydrothermal decomposition method. The experiment showed that the superconducting magnetic separation method to which a high gradient magnetic filter was applied proved to be practically used to remove 90% of heavy metal particles and that the hydrothermal decomposition method proved effective in dehydrating sludge and in minimizing the volume. The study also showed a well-posed hydrothermal condition on temperature and oxidation that matched the magnetic separation to remove heavy metal in sludge.

２１世紀の超臨界流体利用技術 水熱分解によるＰＣＢの無害化処理

Though PCB disposal lagged for fear of generating dioxin's by incineration since 1974, it has been permitted by means of chemical treatment with revision of the law in June 1998. By introducing technology from SRI of the US, we developed hydrothermal decomposition method for PCB so that it will be decomposed in hydrothermal water containing sodium carbonate. The result of fundamental test and pilot test demonstrated that PCB can be treated regardless of its concentration. We also demonstrated that paper, wood and organic solvent can be decomposed, and easily established the treatment system to make harmless perfectly the polluted vessels like a transformer or a capacitor.