Step Hydrothermal Method Research Articles

Visible Active N-Doped TiO₂/WS₂ Heterojunction Nano Rods: Synthesis, Characterization and Photocatalytic Activity.

N-doped titania nano sheets and N-doped titania/tungsten dioxide nano rods were synthesized by two step hydrothermal method. The composition, structural, functional, morphological and optical properties of the as synthesized N-TiO₂/WS₂ hybrids were characterized by XRD, UV-DRS, PL, FE-SEM with EDAX, TEM, FT-IR and Raman spectroscopy. Surface area and thermal stability of the catalysts were analyzed by BET and TG/DTA techniques. The photocatalytic activity of the heterojunction catalyst was evaluated towards the decomposition of a harmful dye namely congo red in an aqueous solution under visible light irradiation. The results show superior photocatalytic activity for N-TiO₂/WS₂ nanocomposite. This unusual photocatalytic activity is attributed to the synergistic effect between WS₂ and N-TiO₂.

One step hydrothermal green approach of CuO/Ag nanocomposites: analysis of structural, biological activities

In this present investigation, CuO/Ag Nanocomposites (NCs) were prepared by one step hydrothermal green method. The Jatropha curcas leaf extract was act as the reducing as well ascapping agent for synthesis of CuO/Ag NCs. The powder x-ray diffraction (PXRD) studies were investigated the crystal phase structure of CuO and Ag nanomaterials. The presence of oxygen vacancies and Cu interstitial defects in the synthesized material was determined by photo luminescence and Raman analysis. The CuO/Ag NCs was evidenced by TEM analysis and elemental composition of the prepared material was identified by EDAX analysis. The green synthesized CuO/Ag NCs exhibited excellent antimicrobial activity and better antioxidant DPPH free radical scavenging activity. The cytotoxicity of CuO/Ag NCs was assayed against osteoblast MC3t3-E1 and able to inhibit the cell growth by dose-dependent manner.

N–doped graphene quantum dots embedded in BiOBr nanosheets as hybrid thin film electrode for quantitative photoelectrochemical detection paracetamol

A facile strategy of electrophoretic deposition has been employed to fabricate a thin film photoelectrochemical (PEC) sensor of functionalized N–doped graphene quantum dots (F–NGQDs) embedded in BiOBr nanosheets, which were prepared by a two–step hydrothermal method, loaded onto indium–tin–oxide coated glass substrate (F–NGQDs/BiOBr/ITO). Electrophoretic deposition provides a mild and environmentally friendly method for PEC film formation. Multiple techniques were applied to investigate the electronic, optical properties and structure of F–NGQDs/BiOBr thin films photoelectrodes. It was found that F–NGQDs/BiOBr thin films with NGQDs/BiOBr heterojunction possess an enhanced charge transfer and absorption wavelengths under visible light, particularly when compared to pristine F–BiOBr films, thus producing an increase in the observed photocurrent. Sensing performance measurements showed the F–NGQDs/BiOBr/ITO photoelectrode has a higher photoelectric response current to paracetamol, it was used to detect trace paracetamol under visible light irradiation. The sensor exhibited a wide linear range, low detection limit and good sensitivity, given the photoactivity of NGQDs/BiOBr heterojunction. The developed PEC sensor displayed an acute response to paracetamol in a linear range of 0.01 μM–20.0 μM with a detection limit of 3.33 nM, under optimal conditions. Here we present evidence that F–NGQDs/BiOBr/ITO photoelectrode is a promising candidate for PEC analysis.

Synthesis of Ni12P5 on Co3S4 material for effectively improved photocatalytic hydrogen production from water splitting under visible light

Building a good catalyst with high efficiency and low cost is a key step in photocatalytic hydrogen production. In this study, catalyst Ni12P5 is successfully modified on Co3S4 by two step hydrothermal methods. The catalyst Ni12P5 has a good promoting effect on the photocatalytic hydrogen production of Co3S4. Composite samples 8% Ni12P5/Co3S4 had the highest photocatalytic hydrogen production activity, and the hydrogen yield reach 4922.4 μmol g−1 h−1, which is 4.8 times higher than that of the original Co3S4 under visible light. The composite sample Ni12P5/Co3S4 maintains good stability of photocatalytic hydrogen production in three cycles. Ni12P5/Co3S4 samples are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), X-ray photoelectron spectroscopy (XPS), electrochemistry and fluorescence (PL), and their physical and chemical properties was analyzed. Electrochemical measurements show that the enhancement of photocatalytic activity is attributed to the high separation and migration of photoinduced electrons and holes, which is consistent with the photocatalytic hydrogen production activity. The results provide a novel idea for the synthesis of other non-noble metal composite photocatalyst, and have important inspiration significance.

One-pot synthesis of aqueous soluble and organic soluble carbon dots and their multi-functional applications

Two kinds of carbon dots (CDs) with different solubility, aqueous soluble CDs (ACDs) and organic soluble CDs (OCDs), were produced at the same time by one step hydrothermal synthesis method using sorbic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by means of UV, fluorescence, TEM, elemental analysis, IR and XPS et al. Based on the effective and proportional fluorescence quenching by Cr(VI), ACDs were successfully used as a high sensitive and selective probe for Cr(VI) detection. Internal filtration effect (IFE) played an important role in the quenching process. Under the optimal conditions, linear response for Cr(Ⅵ) was observed in the range of 0.5–100 μmol/L, and the calculated detection limit was 34 nmol/L. The method has been satisfactorily applied to detect Cr(VI) ions in real water samples of our campus. Then, the ACDs were further applied for cell imaging in B16F10 cells. Furthermore, OCDs were well dispersed into PMMA to fabricate OCDs/PMMA composites as fluorescent films.

Ultra-Sensitive Electrochemical Determination of Rifampicin Using the TiO2nanoparticles Decorated Reduced Graphene Oxide Nanocomposite

We report a facile one step hydrothermal method to synthesize TiO2 nanoparticles decorated by reduced graphene oxide (rGO) sheets. The morphology and chemical composition of the prepared TiO2/rGO nanocomposite were examined by using suitable characterization techniques. The TiO2/rGO nanocomposite was used to modify the glassy carbon electrode (GCE), which showed an effective electrochemical sensing platform for the detection of RIF, when compared to bare GCE. The differential pulse voltammetric studies, as prepared TiO2/rGO nanocomposite exhibited an extraordinary performance in quantifying the RIF. The fabricated sensor showed a low electrochemical detection limit of 0.03 µM over the linear dynamic range 0.01- 1 µM. The proposed electrochemical sensor was successfully employed for the determination of RIF in pharmaceuticals and biological fluids with good recoveries.

Role of point defects in hybrid phase TiO2 for resistive random-access memory (RRAM)

TiO2 thin films based resistive random-access memory was examined for resistive switching behavior. TiO2 thin films were deposited on FTO glass substrate using single step hydro-thermal method with different synthesis parameters. The x-ray Diffraction results confirmed the existence of both anatase and rutile phases (hybrid) in one film and only rutile phase in other film. Morphological studies of prepared TiO2 thin film were carried out using scanning electron microscope. The photo-luminescence results revealed the presence of Ti interstitial defects (Ti+4 & Ti+3) and oxygen vacancies in hybrid phase film. Whereas, Ti interstitial defects were absent in rutile phase film. Current voltage characteristics showed the presence of resistive switching in the hybrid phase film only. The switching characteristics have been attributed to originate from the presence of Ti interstitial defects, facilitating Ag+ ion migration in TiO2 dielectric layer. The observed resistive switching has been explained on the electrochemical metallization (ECM) model.

“Vigna radiata” based green C-dots: Photo-triggered theranostics, fluorescent sensor for extracellular and intracellular iron (III) and multicolor live cell imaging probe

Fluorescent C-dots have drawn increasing attention due to their superior properties such as high aqueous solubility, optical absorptivity, favorable biocompatibility and appreciable photoluminescence. Nature offers various precursors for the synthesis of green C-dots like fruits, vegetables, flowers, animal derivatives and many more. Herein, nitrogen doped C-dots (N@VRCD) were developed by economical, one step hydrothermal method using “Vigna radiata” sprouts as sole carbon precursor and ethylenediamine as the nitrogen source, which was optimized for enhanced optical properties. To the best of our knowledge, N@VRCD shows excellent quantum yield ∼58%. Importantly, N@VRCD also exhibits significant light induced phototoxicity to cancerous cells which enable the possibility of using it as a potential theranostics agent. Further, the N@VRCD displays highly sensitive and selective sensing behaviour towards Fe3+ ions by getting fluorescence “turn-off” with the limit of detection as low as 140 nM. Moreover, N@VRCD shows biocompatible and hemocompatible nature with a potential of multicolor live cell imaging and intracellular Fe3+ detection which was validated by confocal microscopy and flow cytometry.

Investigations on the photo catalytic activity of calcium doped TiO2 photo electrode for enhanced efficiency of anthocyanins based dye sensitized solar cells

The rich photo catalytic activity (PCA) of TiO2 deteriorates the photovoltaic performance of natural dye sensitized solar cells (DSSC) on irradiation. To improve the stability of natural dye in DSSC, the PCA of TiO2 must be passivated or reduced, without affecting the electron transfer kinetics. UV filters can be employed to avoid the direct band gap excitation in TiO2. But the blocking of photons in UV region decreases the Incident Photon to current Conversion Efficiency (IPCE) of the solar cell. Taking this factor into consideration, virgin and calcium (1%, 2%, 3%, 4% and 5%) doped TiO2 photo electrodes were grown by one step hydrothermal method on Fluorine doped Tin Oxide (FTO) substrates. The structural, morphological and optical properties of Ca doped nanorods passivate the free electrons on the TiO2 surface, thereby minimizing the PCA in the film. The 3% Ca doped TiO2 nanorods exhibited higher resistance to PCA when compared undoped TiO2 photo electrode. This increased the photovoltaic conversion efficiency of rose dye sensitized DSSC to 2.32%.

Improvement of photoelectric properties of TiO2/Bi2S3 composite film by annealing treatment

The one-dimensional structure TiO2/Bi2S3 composite films can be used as the photo-anode in the thin film solar cells. Due to its advantages of wide optical absorption range and relatively simpler fabrication progress, the composite film TiO2/Bi2S3 show important value in the photovoltaic field. The composite films were prepared with the simple two step hydrothermal method. The composite film TiO2/Bi2S3 was treated under different annealing temperatures (200 °C, 300 °C, 350 °C and 400 °C). The effect of the annealing temperature on morphology, microstructure, crystallite size, band gap, optical and electrical properties of the resultant material have been investigated. After annealing treatment, the photocurrent density of the composite film was significantly increased. With the increase of annealing temperature, the change tendency of optical absorption and photocurrent density show the same trend, both of them first increase and then decrease. The TiO2/Bi2S3 composite film annealed at 350 °C showed the best photoelectric properties. The Bode-Phase plots indicated the electron lifetime in TiO2/Bi2S3 composite film with 350 °C annealing treatment is about four times than that in as-deposited TiO2/Bi2S3 film. The annealing treatment can promote the secondary growth of Bi2S3 crystals in the composite film TiO2/Bi2S3, increase the light absorption, improve the utilization of sunlight, and thus increase the photocurrent density.

Investigation on Trimethylamine Sensing Performance of PdO‐Decorated ZnO Flower‐Like Structures Synthesized by One‐ Step Hydrothermal Method

AbstractZnO and PdO‐decorated ZnO flower‐like structures have been synthesized using a facile one‐step hydrothermal method followed by subsequent calcination. Then, their structural information and trimethylamine (TMA) sensing performance were investigated. The results exhibited that the diameter of these ZnO flower‐like structures was in the range of 3–7 μm. Its morphology was maintained after introducing PdO nanoparticales. By comparing the sensing properties, it is found that sensors based on PdO‐decorated ZnO flower‐like structures showed higher TMA response than that of pure one. Especially, the sensor fabricated by 1 mol% PdO‐decorated ZnO flower‐like structures displayed superior gas sensing performances including high response, rapid response/recover characteristics, good stability, and high selectivity. Such a superior sensing performance is mainly due to the chemical and electrical sensitization of PdO nanoparticles. This simple synthesis strategy and a desirable TMA sensing performance could be broadly developed other metallic doped metal oxide flower‐like structures as high performance sensing materials.

Tunable bandgap and blue emission of ZnS nanoparticles induced by controlled S vacancies

Poly(vinylpyrrolidone) capped ZnS semiconductor nanoparticles with a controlled amount of S vacancies have been synthesized through the one step hydrothermal method at low temperatures by varying the concentration of thiourea, the sulfur reagent. The hexagonal wurtzite structure of ZnS with particle like morphology has been identified from powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The formation of compound ZnS and elemental purity has been studied from energy dispersive spectra. The role of S vacancy, the influence of lattice strain and surface defect on the emission, as well as the variation of emission intensity with different excitation wavelengths have been studied using a photoluminescence spectrometer. With an increase in the excitation wavelength, a variation intensity and a red shift in the peak position due to different contributions of free excitonic emissions and its phonon replicas have been noticed and discussed in detail. Raman spectroscopy confirms the formation of ZnS nanoparticles; the shift and broadening in Raman spectra have been studied in detail. The spectral shift and the tunable bandgap of ZnS with S vacancy have been explained on the basis of crystallinity, crystallite size, particle size, lattice strain, and defects on the surface.

Nanostructured CeO2/FeO3/Mn-rGO composite as anode material in Li-ion battery

Based on the idea of exploring the possibility of designing anode material for high-capacity lithium-ion (Li-ion) battery, we have successfully synthesized Mn-doped CeO2/Fe2O3 (CFM) nanocomposite with and without reduced graphene oxide (rGO) via two steps hydrothermal method. The microscopy result revealed that morphology orientation of the nanocomposites strongly depends on the temperature. Thermogravimetric analysis (TGA) was used to identify phase transition and stability. X-ray diffraction, surface area analysis (BET) and atomic force microscopy (AFM) provided information about the structural, specific surface area and morphology of the samples. Elemental compositions and oxidation states of the samples were confirmed by EDX and XPS. When the prepared nanocomposites were used as anode materials in lithium-ion batteries, both CFM and CFM@rGO composites exhibited high capacity and good cycling stability. However, the CFM@rGO composite gives more lithiation sites and accommodate large volume changes during the lithiation/delithiation process than pure CFM composite. Thus, an average reversible capacity of over ∼420 mAhg−1 was obtained at a current of 0.1 C even after 50 cycles. The obtained result demonstrated that hydrothermal method could be more suitable for the preparation of large-scale CFM@rGO anode materials for Li-ion battery application.

Effect of Zr Doping on the Magnetic and Phase Transition Properties of VO2 Powder

In this work, V1−xZrxO2 powder (x = 0, 0.01, 0.02, 0.04) was synthesized by two step hydrothermal method. The micro-topography, magnetic and phase transition properties have been investigated using various measurement techniques. All prepared V1−xZrxO2 powder samples exhibit monoclinic structure at room temperature. With the Zr4+ ions doping concentration increased, the shapes of VO2 particles change from spherical to rectangular slice. Besides, the saturation magnetic moment of the samples decrease with the increase of doped Zr4+ ions concentration, while their phase transition temperature increase gradually with Zr ions doping at a rate of around 2 °C/at% on average. We investigated the Zr doping effects on V-V dimers and confirmed the role of V-V dimers in phase transition. We speculate that more V-V dimers form with Zr doping by magnetic measurements, which result in the monoclinic phase of Zr-doped VO2 sample is more stable than rutile phase. Therefore the phase transition temperature is elevated by Zr doping in our experiment. We further consider that the VO2 phase transition should be ascribed to Peierls transition caused by the changing of V-V dimers.

Influence of cations on the dielectric properties of spinel structured nanoferrites

MFe2O4 (M: Fe, Zn, Ni and Sn) nanoparticles were prepared using single step hydrothermal method. Their structural, compositional and dielectric properties have been studied to investigate the effect of cations on spinel ferrites. XRD confirms the spinel structure of the samples with substitution of Zn, Ni and Sn in the lattice sites of Fe. FTIR spectra of all samples have characteristic υ1 and υ2 bands. SEM and EDS mapping show uniform distribution of cations throughout the samples. ZnFe2O4 and SnFe2O4 have higher ac conductivity and dielectric constant than that of Fe3O4 and NiFe2O4, which can be attributed to the different cationic distribution in the spinel structure.

Novel hydrothermal growth of ZnO/NiO hybrids nanostructures on 3D graphene

Abstract The 3D graphene possesses fast electron transport mobility and high mechanical strengths owing to the combination of both intrinsic properties of 2D graphene and 3D microstructure. The microporous structure of 3D graphene provides excellent platform for combination with other nanostructures to form hybrid nanomaterials. These hybrid nanostructures have attracted a tremendous amount of interest in recent years due to their excellent surface-area-to-volume ratio, improved catalytic activity, high electron mobility and several functionalities that are superior to those of pure nanomaterials. In this study, hybrid zinc oxide (ZnO) nanorods with nickel oxide (NiO) nanosheets were grown on 3D graphene substrate via two step hydrothermal method and their structural characteristics analysed for application as biological sensing material. ZnO and NiO exhibited crystal lattice in preferred c-axis orientation with higher purities. Observations under field emission scanning electron microscopy revealed the growth of ZnO nanorods followed by the NiO nanosheets formation upon the second hydrothermal process. The obtained results showed significant growth of ZnO nanowire and NiO nanosheets via two step hydrothermal route. The created hybrid nanostructures of ZnO/NiO on 3D graphene demonstrate the optimized processing technique needed to generate novel advanced materials, which opens a new avenue for medical diagnostics.

One-step synthesis of bifunctional iron-doped manganese oxide nanorods for rechargeable zinc–air batteries

Iron doped MnO2 nanorods are successfully synthesized via one step hydrothermal method. The nanorods shows remarkable high bifunctional electrocatalytic activity for oxygen reduction as well as oxygen evolution reaction. For practical applications, a solid-state zinc–air battery was made for powering a light emitting diode.

Synthesis of Ge4Se9 nano plates and a reduced graphene oxide composite of Ge4Se9 for electrochemical energy storage application.

In this study, we introduced a facile and single-step synthetic protocol for the scalable synthesis of tetra germanium nonaselenide (Ge4Se9) and it's composite with reduced graphene oxide (RG). The physicochemical properties of the samples were studied systematically, and their electrochemical performances for energy storage in supercapacitors were explored. Herein, the weight percentage of graphene oxide in the composite played a vital role in the enhancement of charge storage. Among other composites, the Ge4Se9/RG1 composite showed an enhanced specific capacitance (220 F g-1) with a higher specific energy (12 W h kg-1) as well as power (4.6 kW kg-1). Moreover, the composite showed excellent cycling stability (with 91% of capacitance retention after 10 000 repeated cycles) and reversibility (∼98% coulombic efficiency). Furthermore, the robustness of the composite was accessed via the post-stability analysis.

A novel design and synthesis of ruthenium sulfide decorated activated graphite nanocomposite for the electrochemical determination of antipsychotic drug chlorpromazine

A novel electrochemical sensor based on ruthenium sulfide nanoparticles decorated activated graphite sheets (RuS2/AG) was designed and fabricated for the determination of antipsychotic drug chlorpromazine hydrochloride (CPZ). Activated graphite sheets (AG) were prepared by non-explosive, non-hazardous and simple chemical activation technique. Then, the AG sheets were used for the synthesis of RuS2/AG nanocomposite by single step hydrothermal synthesis method. The synthesized materials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The synergistic effect of the RuS2/AG nanocomposite was applied for the determination of CPZ by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fascinatingly, the RuS2/AG nanocomposite exhibited the excellent electrocatalytic activity and detects the CPZ at very lowest oxidation potential about 0.60 V vs Ag/AgCl in pH-7 PB solution. Moreover, the lowest LOD 8 nM and wider linear ranges from 0.05 to 79.75 and 79.75–1249 μM was obtained towards the CPZ determination. Besides, the proposed sensor shows the good selectivity, satisfactory repeatability, reproducibility and stability. Furthermore, the real time application was evaluated in pharmaceutical tablets and human urine samples.

MoS2/ZnO nanocomposites for efficient photocatalytic degradation of industrial pollutants

In the present work, molybdenum disulphide-zinc oxide (MoS2/ZnO) nanocomposites were synthesized via a simple dual step hydrothermal reduction method using hydrazine hydrate as a reducing agent. The as prepared nanocomposites have been characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman and photoluminescence (PL) spectroscopy. The structural and morphological analysis showed that particles are crystalline in nature and cubical in shape with an average size of ∼22.5 nm.The nanocomposites were evaluated for photocatalytic property. The degradation analysis of industrial pollutants such as Novacron red Hunts- man (NRH) and methylene blue (MB) dye reveals that MoS2/ZnO nanocomposite is an efficient catalyst.