Step Hydrothermal Method Research Articles

Unstable cell efficiency in CdS quantum dot sensitized solar cell using low cost lugols iodine aqueous electrolyte

We have designed and synthesis rutile TiO2 rod like nanoflower on the FTO glass by one step hydrothermal method operating at 150 °C for 15 h. The lower concentration of CdS Quantum dots was deposited on the surface of TiO2 through chemical bath deposition (CBD) method. The samples were characterized x-ray diffraction pattern (XRD), Scanning electron microscopy (SEM) and UV–Vis absorption studies. In this work lugols iodine was used as an aqueous electrolyte between FTO/TiO2/CdS photoanode and Cu2S as counter electrode respectively. The result of photo conversion efficiency (PCE) is decreased from 0.13 to 0.033%, this may be the reason photo degradation and corrosion were happened in CdS.

Effect of citric acid on the synthesis of ZnWO4/ZnO nanorods for photoelectrochemical water splitting

ZnO nanorods (NRs) and ZnWO4/ZnO heterostructure, using TiO2 seed layers, were synthesized by two steps hydrothermal method and annealed at 450 °C for 2 hr. The results showed that the ZnWO4 was grown on the hexagonal ZnO NRs and change to hierarchically structure when the citric acid content was increased. All samples were applied as photoanode for photoelectrochemical (PEC) water splitting cell. As the result, the 50ZnW/ZnO sample showed the best performance of the PEC water splitting process than others. From the Electrochemical Impedance Spectroscopy (EIS) study, the Nyquist plot of 25ZnW/ZnO and 50ZnW/ZnO samples showed smaller arc compared to ZnO NRs. This is signified that the ZnWO4/ZnO heterostructure has greater charge transfer between the photoanode and electrolyte than the pristine ZnO. Hence, the modified ZnWO4 on the ZnO surface enhances the performance of ZnO NRs based PEC water splitting cell for the UV light hydrogen fuel generation.

Ti/Cr incorporated mesoporous MCM-48 for oxidation of styrene to benzaldehyde

The present work emphasizes on synthesis of metal incorporated mesoporous MCM-48 materials and evaluates their catalytic activity towards styrene oxidation. Ti and Cr loaded MCM-48 materials with varying Si to Ti or Cr molar ratios have been synthesized by one step hydrothermal method. The prepared catalysts were characterized using various techniques such as XRD, FT-IR, UV–Vis DRS, N2 adsorption–desorption and SEM–EDX analysis. Catalytic activity of the synthesized materials towards the liquid phase oxidation of styrene was performed in presence of aqueous hydrogen peroxide as oxidant where benzaldehyde was obtained as major product. The effect of various reaction parameters viz. temperature, catalyst amount, styrene to H2O2 molar ratio etc. were studied to observe the change in styrene conversion as well as selectivity towards benzaldehyde.

Near-infrared reflectance and thermal insulating performance of Mo-doped Bi2WO6 with 3D hierarchical flower-like structure as novel ceramics pigment

The pigments with the formula of Bi2W1−xMoxO6 (x = 0.0, 0.1, 0.2, 0.3, 0.4) are synthesized by one step hydrothermal method. The pigments are characterized with XRD, FE-SEM, XPS, UV/VIS/NIR spectrometer, thermal conductivity and TG-DTA. The results reveal that the samples are of orthorhombic phase with no impurity phase existing and three-dimensional hierarchical flower-like architectures with diameter ranging from 2 to 3 μm. The color of the doped samples progressively transfers from pale yellow to yellow. The band gap decreases from 2.82 eV to 2.42 eV, which is attributed to the charge transfer excitation changes from Bi 6s → O 2p to the transition of Mo 3d → O 2p. As compared with the conventional pigments with similar color, the Mo-doped Bi2WO6 pigments perform better on the near-infrared solar reflectivity and the highest near-infrared solar reflectance is as high as 80.80%. The distinction of the NIR solar reflectance values among the pigments is majorly attributed to the different oxygen concentration induced by the reaction formula: Bi2Mo1-xWxO6 → Bi2Mo1-xW6+x-δ(W6+·2e) δO6-δ + δ2O2↑.The thermal conductivity of some Mo-doped Bi2WO6 pigments is apparently lower than its pigment counterpart owning to the 3D hierarchical flower-like structure. The pigments are also possessing eminent thermal and chemical stability. The Mo- doped Bi2WO6 samples not only have high near-infrared reflectance with beautiful color but also have comparatively benign thermal insulating performance, so that they are promising to be served as novel amiable ceramic pigments to manipulate the thermal property of ceramic materials.

Facile Hydrothermal Synthesis and Electrochemical Performance of NiCo2O4 Nanoneedles

NiCo2O4 nanoneedles on the surface of Ni foam were grown by a simple one step hydrothermal method, which is used as the working electrode for asymmetric supercapacitors. Its area specific capacitance is 981.64 C cm–2 at 1 mA cm–2, and the cycling stability can reach 100% after 10000 cycles at 4 mA cm–2. The spatial structure of the nanoneedle has important influence on the cyclic stability of NiCo2O4 electrode. The hybrid supercapacitors are prepared on the basis of the prepared NiCo2O4 nanoneedle electrodes. After 8000 cycles, its cycle life is stable and the capacitance retention rate reaches 100%.

Mesoporous Gd2O3/NiS2 microspheres: a novel electrode for energy storage applications

Development of novel Faradic electrode with excellent rate capability and long-lasting characteristics determines the performance of supercapacitor (SC) in current scenario. Rare-earth metal oxides have received considerable attention in SC domain with high volumetric energy density and capacitive performance. In this context, we have fabricated gadolinia/nickel sulphide nanocomposite via simple chemistry approach followed by two step hydrothermal method. Especially, the gadolinia/nickel sulphide nanocomposite synthesized in the current study offers high specific capacitance (354 F g−1 at a constant current density of 0.5 A g−1), low charge transfer resistance (6.37 Ω) and outstanding cycle life (1.3% loss capacitance loss even after 5000 continuous charge/discharge cycles). Such enduring energy characteristics of gadolinia based nanocomposite will create a huge impact in the future energy storage systems

Surfactant-free pH-assisted facile engineering of hierarchical rutile TiO2 nanostructures by a single step hydrothermal method for water splitting application

The structural appearance of TiO2 nanostructures can be easily engineered by means of pH of the solvent solution.

Modification of egg shell powder with in situ generated copper and cuprous oxide nanoparticles by hydrothermal method**Thailand Patent filed with Registration Number: 1903001590.

The poultry waste of egg shells was cleaned and finely powdered which was subsequently modified with in situ generated copper nanoparticles (CuNPs) and cuprous oxide nanoparticles (Cu2ONPs) by one step hydrothermal method. The modified egg shell powder (MESP) was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis and antibacterial tests. The MESP had in situ generated spherical CuNPs and Cu2ONPs in the size range of 50 nm to 120 nm. The spectral analysis indicated lowering of intensity of the peaks of MESP indicating the involvement of the functional groups of the protein component of ESP in the generation and stabilization of the nanoparticles. X-ray analysis indicated the generation of both CuNPs and Cu2ONPs in MSEP. The thermal analysis indicated lowering of the thermal stability for MESP. The MESP exhibited excellent antibacterial activity against both the Gram negative and Gram positive bacteria. Hence the low cost MESP with in situ generated CuNPs and Cu2ONPs can be used as antibacterial cleaning powder for houseware and also as antibacterial filler in the preparation of polymer composites.

Facile synthesis of FeS2/MoS2 composite intertwined on rGO nanosheets as a high-performance anode material for sodium-ion battery

In this work, we demonstrate the FeS2/MoS2 composite embedded in rGO nanosheets (FeS2/MoS2-rGO composite) as an anode material for sodium-ion battery. The FeS2/MoS2 composite material was synthesized by one step hydrothermal method, and the prepared particles were wrapped by reduced graphene oxide (rGO) nanosheets, which facilitated the electronic transport between the particles, and suppressed the volume expansion of active materials as well as the polysulfide dissolution into the electrolyte during cycling. The FeS2/MoS2-rGO composite electrode delivered a high initial discharge capacity of 468.0 mA h g−1 and exhibited good cycling stability at a current density of 100 mA g−1. Due to the pseudocapacitive behavior of FeS2/MoS2-rGO electrode, a high reversible capacity of 346.5 mA h g−1 was achieved at 3000 mA g−1, which was much higher than those of FeS2, MoS2 and FeS2/MoS2 composite electrodes. The sodium-ion full cell assembled with FeS2/MoS2-rGO composite anode and Na3V2(PO4)2F3 cathode exhibited a high reversible capacity with good cycling stability, which demonstrates that the prepared FeS2/MoS2-rGO composite can be used as a promising anode material for sodium-ion batteries.

Zn-ion batteries: ZnMn2O4 as cathode material

In this paper, we have successfully synthesized and characterized ZnMn2O4 nanocomposite as cathode material. ZnMn2O4 has been synthesized by one step hydrothermal method using Zinc acetate, potassium permanganate and Aniline as precursors. From XRD spectra, we have calculated the average crystallite size and residual tensile strain. The electrochemical behavior is studied by cyclic voltammetric technique, galvanostatic charge discharge and Impedance analyzer.

A highly enhanced electrochemiluminescence system based on a novel Cu-MOF and its application in the determination of ferrous ion

A novel copper (Ⅱ) metal-organic framework ([Cu(L)(H2O)2]nCu-MOF) has been successfully synthesized by facile one step hydrothermal method. Modified the glassy carbon electrode (GCE) with this kind of Cu-MOF, a strong cathode electrochemiluminescence (ECL) signal was produced under the potential scan from 0.2 to −1.6 V in the potassium persulfate solution, which was about 8 times higher than that on the bare GCE electrode. The possible enhancement mechanism was studied in detail. The results showed that Cu (Ⅱ) in Cu-MOF catalyzed the reduction of potassium persulfate promoting the conversion of S2O82− into SO4•− and enhancing ECL signal intensively. Based on the inhibition effect of ferrous ion on this ECL signal, a sensitive ECL method for the determination of ferrous ion was developed within the linear range from 1.0 × 10−10 M to 3.0 × 10−8 M and the detection limit of 4 × 10−11 M. The ECL method showed high sensitivity, good stability, and excellent reproducibility and had been applied for analysis of ferrous ion in environmental water samples successfully.

Dual responsive magnetic Fe3O4-TiO2/graphene nanocomposite as an artificial nanozyme for the colorimetric detection and photodegradation of pesticide in an aqueous medium

The Fe3O4-TiO2/reduced graphene oxide (Fe3O4-TiO2/rGO) nanocomposite was successfully prepared by one step hydrothermal method and exhibit intrinsic peroxidase mimic activity and photocatalytic efficiency. The as-prepared nanomaterials were characterized by several analytical tools including XRD, HRTEM, FESEM, XPS, VSM, FT-IR, AFM, TGA and zeta potential analysis. The average particle size of Fe3O4 and TiO2 NPs on the rGO nanosheets are found to be 9 ± 0.2 nm. The synthesized nanocomposite showed dual responsive including highly sensitive colorimetric detection of harmful atrazine pesticide in an aqueous medium as well as photocatalytic degradation of atrazine pesticide. The Fe3O4-TiO2/rGO nanocomposite showed the efficient peroxidase-like catalytic activity throughout the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) as a peroxidase substrate to the blue-colored oxidized product (ox-TMB) in presence of H2O2. Based on this observation, the colorimetric detection technique is applied for the sensing of atrazine as model pesticides using TMB as a peroxidase substrate molecule and 2.98 μg/L of the limit of detection (LOD) was obtained in the linear range of 2–20 μg/L. Thus the proposed colorimetric sensing technique is simple and low cost for the real-time monitoring of the pesticides in an aqueous medium. Further, the Fe3O4-TiO2/rGO nanocomposite was also successfully utilized towards efficient photocatalytic degradation of atrazine molecule (100 %) under irradiation of natural sunlight. Moreover, Fe3O4-TiO2/rGO nanocomposite was successfully recycled for 10 times without a significant loss of its photocatalytic efficiency. This work delivers a new insight for the dual responsive of the Fe3O4-TiO2/rGO nanocomposite as an artificial nanozyme for colorimetric sensing of the water pollutant and also removal of the water pollutant by simple photocatalytic degradation method under natural sunlight irradiation.

Fabrication of high surface area AgI incorporated porous BiVO4 heterojunction photocatalysts

The low surface area and photogenerated charge carrier recombination rate severely affects the usability of a photocatalysts. In this work, a visible light active AgI/BiVO4 photocatalyst was fabricated via a low temperature one step hydrothermal method. Low temperature preparation results in a porous and very high surface area (114 m2/g) BiVO4 photocatalysts. XRD, FTIR, Raman and BET surface area analysis revealed that AgI is bonded as well as embedded in the porous structure of BiVO4, which causes shrinking of the BiVO4 lattice. Compare to bare BiVO4, the AgI/BiVO4 photocatalyst shows nearly 1.7 times higher photocurrent response and 43% higher photocatalytic activity. The significantly high photocatalytic activity ascribed to the very high surface area, and the effective charge separation at the AgI/BiVO4 p-n heterojunction. Further, based on UV-DRS and Mott-Schottky measurements, a plausible charge transfer mechanism is proposed.

Platinum-free metal sulfide counter electrodes for DSSC applications: Structural, electrochemical and power conversion efficiency analyses

Micro/Nanoscale binary (CoS, NiS, and ZnS) and ternary (CoNi2S4 and Zn0.76Co0.24S) metal sulfides were directly grown on FTO substrates by a novel one step hydrothermal method for low-cost DSSC counter electrode applications. XRD study confirms phase pure formation of CoS, NiS, ZnS, CoNi2S4 and Zn0.76Co0.24S. HRSEM images of CoS, NiS and CoNi2S4 films exhibits hierarchical flower, hexagonal microcage and flake like particulates respectively. The ZnS and Zn0.76Co0.24S films show spherical micro-nanoparticles. The nanoflake morphological CoS and CoNi2S4 revealed high surface area measured by BET analysis. XPS result confirms the chemical states of CoNi2S4 and Zn0.76Co0.24S. A detailed electrochemical cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy (EIS) analyses reveals the ternary metal sulfide (CoNi2S4) possesses an excellent electrocatalytic activity and electrical conductivity than other counter electrodes for the reduction of tri-iodide to iodide. Photovoltaic performance of the devices was studied using standard solar simulator at 1 Sun intensity (AM 1.5 G) and dark conditions. The reduced dark current obtained in CoNi2S4 and Zn0.76Co0.24S confirms the less recombination of electrons in ternary metal sulfides based DSSCs. The power conversion efficiency of ~4.03% achieved in Pt-free CoNi2S4 counter electrode is comparable to standard Pt based DSSC (~4.59%). The CoNi2S4 exhibiting good device performance and high electrocatalytic activity can serve as efficient low-cost counter electrode for Pt-free DSSCs.

Effect of ethylenediamine on morphology of 2D Co-Mo-S@NG hybrids and their enhanced electrocatalytic activity for DSSCs application

Novel 2D Co-Mo-S anchored on nitrogen-doped graphene (NG) nanosheets was synthesized by simple and cost effective one step hydrothermal method. The effect of ethylenediamine (ETA) on morphology and catalytic activity of Co-Mo-S@NG was studied. Transmission electron microscopy image showed that morphology of Co-Mo-S nanorods and nanosheets changed into flower-like nanostructures composed of numerous sheets by ETA. Scanning transmission microscope showed the formation of Co-Mo-S nanoflower on the surface of NG. X-ray photoelectron spectra analysis confirmed the effective doping of nitrogen in graphene and Co-Mo-S. Counter electrode of dye sensitized solar cell was fabricated by simple spray pyrolysis method at 150 °C. Co-Mo-S@NG with ETA showed lower value of separation between anodic peak and cathodic peak (Epp), higher stability and higher current density compared with pure Cu-Mo-S@NG counter electrodes (CE). Co-Mo-S@NG with ETA showed 1.12% efficiency and current value (Jsc) of 7.22 ± 0.5 mA.

Growth and influence of Gd doping on ZnO nanostructures for enhanced optical, structural properties and gas sensing applications

Undoped and Gd-doped ZnO nanorods and nanoflowers were successfully prepared by one step hydrothermal method. The effect of Gd concentration on the formation of different morphology has been investigated. The X-Ray Diffraction analysis showed that the prepared ZnO nanostructures exhibits hexagonal wurtzite phase. The morphology of the nanostructures of ZnO was analyzed by FE-SEM and TEM. ZnO nanoparticles were transformed into nanorods and nanoflowers with increasing the wt% of Gd. UV-Visible spectroscopic studies showed that the presence of Gd in the ZnO matrix leads to tuning of bandgap. Where 6 wt% of Gd incorporation in ZnO matrix showed decrease in bandgap compared to undoped ZnO. The significant peak shift was observed in the electronic state of Zn at the higher concentration of Gd, which confirms the presence of Gd in ZnO matrix. Significant enhancement of xylene sensitivity was achieved by Gd doping in ZnO. These findings indicate that Gd-doped ZnO (GZ4) can be considered as good xylene sensing element at room temperature.

Hierarchical Iron/Nickel-Based Sulfide Supported on Ni Foam As a Bifunctional Electrocatalyst for Efficient Overall Water Splitting

Water splitting, consisting of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), has received great attention owing to the potential to provide future sustainable and renewing energy source. However, the kinetically sluggish process of OER at anode and HER at cathode requires highly active electrocatalysts to accelerate the both electrode reactions. Currently, nickel-based catalysts are widely regarded as an effective electrocatalyst for OER due to their low cost, high stability, good redox properties, and high electrocatalytic performance. Herein, iron/nickel-based sulfide supported on Ni foam were simply synthesized using two step hydrothermal method and was used as a bifunctional electrocatalyst for OER and HER. The iron/nickel-based sulfide only require the low overpotentials of as smaller as 281 and 222 mV for HER and OER, respectively, at current density of 50 mA cm−2 in 1 M KOH. Assembled as an electrolyzer for overall water splitting, this bifunctional catalyst also indicates excellent low onset potential of only 1.41 V and deliver a current density of 10 mA cm−2 at a very low cell voltage of 1.59 V. The outstanding electrochemical performance of iron/nickel-based sulfide on Ni foam is mainly attributed to the synergistic effect of the binary metal system, leading to increasing the electroconductivity, active surface area, and intrinsic catalytic activity. These iron/nickel-based sulfide materials can be widely applied to fabricating efficient energy conversion and storage.

Photothermal property in MoS2 nanoflakes: theoretical and experimental comparison

Recently, molybdenum disulfide (MoS2) nanoflakes, as one of the most stable layered transitional metal dichalcogenides, have attracted lots of attention because MoS2 nanoflakes offer unique thermal and optical properties which are different from their bulk counterparts. In this work, MoS2 nanoflakes were synthesized by one step hydrothermal method and their application was investigated as a photothermal agent for photothermal therapy and drug delivery. The sample structure and optical properties were characterized by x-ray diffraction, Transmission electron microscopy, Raman spectroscopy, Fourier transform infrared and Ultraviolet-Visible spectroscopy. These characterizations confirmed that synthesized MoS2 has been exfoliated very well. The photothermal results indicated that the temperature of MoS2 nanoflakes rise with irradiation of 808-nm continuous wave laser with 1 W cm−2 power density. Then numerical simulation was used to compare their thermal properties with gained results of photothermal experiment for MoS2 nanoflakes with different concentrations. Finally, the outcome indicated that there is attractive agreement between experimental and theoretical results.

Nitrogen doped fluorescent carbon quantum dots for on-off-on detection of Hg2+ and glutathione in aqueous medium: Live cell imaging and IMPLICATION logic gate operation

The present work describes the synthesis of N-CQDs via one step hydrothermal methods. The synthesized N-CQDs was fully characterized by TEM, P-XRD, FT-IR, XPS and Zeta sizer. It exhibited excitation independent emission behaviour with fluorescent quantum yield of 41% respect to quinine sulphate standard. The excellent optical properties of N-CQDs made it fluorescent probe for turn off detection of toxic heavy metal ion Hg2+ with good selectivity and sensitivity. The limit of detection was found to be 0.08 μM with correlation coefficient (R2 = 0.992). After addition of various reducing agent such as amino acid, EDTA and GSH in the quenched solution of N-CQDs + Hg2+, the fluorescence property was selectively recovered in the presence of GSH and hence the quenched solution further acts as selective turn on sensing of GSH up to lower limit of 2.0 μM with correlation coefficient (R2 = 0.996). The on-off-on sensing behaviour of N-CQDs was utilized for the implication of logic gate in absence and presence of Hg2+ and GSH to construct the molecular switches. The MTT assay of N-CQDs was performed on MCF-7 cancer cell line to check their applicability in biological system and the result showed negligible cytotoxicity and good permeability. The cell imaging on MCF-7 cells visualized in dichromic region (blue and green). Therefore, it could be smart material for sensing of heavy toxic metal as well as cell imaging application.

In-situ functionalization of GO sheets with AlOOH-FeOOH composite nanorods: An eco-friendly nanoadsorbent for removal of toxic arsenate ions from water

Water contaminated with arsenic (As) has become a worldwide problem due to its obligatory toxicity. Therefore, there is a great challenge for researchers to develop a cost-effective and highly efficient nanoadsorbent material for As removal. In this work, we have synthesized boehmite-lepidocrocite (AlOOH-FeOOH) composite nanorods mounted onto previously prepared graphene oxide (GO) surface (GO/AlOOH-FeOOH) by one step hydrothermal method. Then the prepared GO/AlOOH-FeOOH nanocomposite was sintered at 400 °C to form GO/Al2O3-Fe2O3 nanocomposite. Both the obtained GO functionalized nanocomposites were used as adsorbents for As(V) removal from water. The XRD, HRTEM confirmed the formation of γ (AlOOH-FeOOH) and γ (Al2O3-Fe2O3). TEM images revealed the formation of rod shape composite nanomaterials on GO surface. The GO/Al2O3-Fe2O3 showed magnetic properties with saturation magnetization value of 5.8emug−1. Among the two prepared nanoadsorbents the GO/AlOOH-FeOOH shows better adsorption properties with maximum uptake capacity of 24.6 mgg-1. The kinetics and isotherm experiments suggested that the adsorption process obeyed pseudo second order kinetic and Freundlich isotherm model. The presence of common coexisting anions including Cl-, SO42-, NO3- showed no significant effect on adsorption except PO43-. The mechanism of As(V) adsorption on GO/AlOOH-FeOOH includes electrostatic interaction and surface complexation reaction.