One-step Hydrothermal Procedure Research Articles

Increased Active Sites on Irregular Morphological α-Fe2O3 Nanorods for Enhanced Photoelectrochemical Performance.

Uniform rectangular α-Fe2O3 nanorods (R-Fe2O3) and irregular α-Fe2O3 nanorods (D-Fe2O3) with a random size vertically aligned on fluorine-doped tin oxide were prepared with a facile one-step hydrothermal procedure. X-ray diffraction (XRD) measurements and Raman spectra confirm that the obtained samples are α-Fe2O3, and XRD patterns show that D-Fe2O3 has two extra (012) and (104) planes of hematite in addition to the identical peaks to R-Fe2O3. The carrier density of the D-Fe2O3 sample is four times larger than that of R-Fe2O3. Finally, the D-Fe2O3 photoelectrode exhibited a better photoelectrochemical (PEC) performance under visible illumination than that of R-Fe2O3, achieving the photocurrent density of 0.15 mA cm–2 at 1.23 V versus reversible hydrogen electrode. In addition, incident photo-to-current conversion efficiency of D-Fe2O3 is nearly three times larger than that of R-Fe2O3. Hence, the improved PEC performance of D-Fe2O3 can be ascribed to higher carrier density resulting from the amount of oxygen vacancies and more activated exposed surface facets.

In-situ growth of 3D rosette-like copper nanoparticles on carbon cloth for enhanced sensing of ammonia based on copper electrodissolution

Copper is an attractive candidate for sensing ammonia. Here, an electrodissolution mechanism for measuring liquid-phase ammonia was developed via a novel three-dimensional rosette-like structure of copper nanoparticles (CuNPs) integrated onto carbon cloth (CuNPs/CC). A one-step hydrothermal synthetic procedure was employed to construct the metallic CuNPs with a stereo rosette-like pattern on flexible CC substrate. The morphology, composition and sensing performance of the as-prepared composite were characterised in detail. The CuNPs/CC composite showed excellent sensing performance to ammonia, which is attributed to the electrodissolution of CuNPs being promoted by ammonia to form a stabilised copper-ammonia complex. This electrochemical response occurs without the electro-oxidation of ammonia, thus avoiding the energy barrier of the N–N bond and the toxicity of N-adsorbates, which is advantageous for ammonia detection. In addition, the sensor also shows very high sensitivity to ammonia with a low detection limit, as well as good anti-interference performance, repeatability and stability. The high accuracy and precision for the quantification of ammonia concentration in a variety of real samples indicate that the CuNPs/CC composition has potential in the development of high-performance ammonia sensors.

Phase modulation in nanocrystalline vanadium di-oxide (VO2) nanostructures using citric acid via one pot hydrothermal method

Abstract Herein, we report the successful synthesis of different phases of VO2 nanomaterials via a facile hydrothermal method by simply varying the molar ratio of the reducing agent (citric acid monohydrate) to vanadium precursor (vanadium (V) oxide). Six samples were synthesized with corresponding variation in molar ratio of vanadium (V) oxide to citric acid monohydrate as 1:1, 1:1.5, 1:2, 1:3, 1:4 and 1:5, respectively. The synthesized nanomaterials were characterized by phase identification, morphologies, compositional, optical, thermal, and electrical properties. The detailed characterizations confirmed the formation of single phase VO2 (B), VO2 (M) and amorphous VO2 by the mere variation of relative concentrations of reducing agent. Even though the synthesis of single phase VO2 is challenging and interestingly, a simple, one-step hydrothermal process procedure was used to produce pure phaseVO2 without the use of inert environment or post-synthesis heat treatments.

Covalent bonding of ZnO nanostructures with dispersible carbon nanotubes for self-assembly photocatalytic heterostructures

Abstract This work demonstrates the fabrication of zinc oxide‑carbon nanotube (ZnO/CNT) heterostructures with tunable photocatalytic activity via microstructure modulation. The ZnO/CNT heterostructures are constructed in one-step hydrothermal procedure consisting of in situ anchoring of ZnO nanostructures with dispersible CNTs in an aqueous alkali solution containing bile salts as a dispersant. Observation via scanning (SEM) and transmission (TEM) electron microscopy reveals self-assembled heterostructures of monodispersible CNTs tightly surrounding ZnO nanostructures with multimorphology. The XRD, FT-IR, Raman and XPS analysis confirm that the CNTs were successfully incorporated into the ZnO nanostructures with strong interfacial contact of covalent bonding rather than simple mixing. A series of ZnO/CNT heterostructures, which varies according to their degree of doping with dispersible CNTs, exhibit distinct sunlight-induced photocatalytic activity onto the degradation of Rhodamine B (RhB). The superior photocatalytic performance of ZnO/CNT heterostructures originates from synergistic effects of sufficient interfacial bonding, self-assembly microstructures, and continuous conducting pathways between ZnO nanostructures and CNTs, which acquires better sunlight utilization and more efficient separation of electron-hole pair, confirmed by UV–Visible diffuse reflectance spectra as well as photocurrent and photovoltage analysis. This study also proposes a photocatalytic degradation mechanism of RhB dyes through detection of active species confirmed by electron-spin-resonance analysis.

Impacts of graphene sheets on photoelectric and photocatalytic activities of SnS2 nanoparticles

Abstract Hybrid materials of SnS2 nanoparticles on graphene sheets (GS) were prepared by a facile one-step hydrothermal procedure. The as-obtained samples were characterized by X-ray diffraction (XRD), Raman spectra, UV–vis diffuse reflectance spectra (DRS), Transmission electron microscopy (TEM), photoluminescence spectra (PL) and electrochemical equipment. The effects of GS on photoabsorption range, the apparent band gap, the separation efficiency of photogenerated electron-hole pairs, and concentration of hydroxyl radicals of SnS2 were researched. The as-samples exhibited an enhanced absorption in the visible region (λ > 600 nm) with increasing the amount of graphene and the band gap was about to 2.11 eV. The photocatalytic activity of GS/SnS2 is consistent with the results of photocurrents and concentration of hydroxyl radicals and the best ratio of graphene to SnS2 is 1%. The graphene can effectively promote the separation of photo-induced carriers and thus strengthen the photocatalytic ability. Furthermore, excess graphenes will not favor the enhancement of photocatalytic activity.

High sensitivity label-free detection of Fe3+ ion in aqueous solution using fluorescent MoS2 quantum dots

MoS2 quantum dots were successfully prepared by a one-step hydrothermal exfoliation procedure. The prepared MoS2 quantum dots are monodispersed and have a circular shape, with an average diameter of 4.67 nm. Excited by UV-light, MoS2 quantum dots emit blue-purple fluorescence, and the fluorescence intensity is suppressed with the addition of Fe3+ ions. On this basis a novel fluorescent MoS2 quantum dots–Fe3+ label-free detection system is proposed. The decay curves of fluorescence show that the fluorescence quenching follows a static process. The binding stoichiometry ratio of Fe3+ ions toward MoS2 quantum dots is recognized as 1:1, based on the Benesi-Hildebrand and Job’s plot methods. For the concentration range of 0–50 μmol/L, the Fe3+ and fluorescence intensity are linearly related to 99.39%. The detection limit reaches 1 μmol/L. Several common ions were also examined that have little cross-influence on the fluorescence intensity of the MoS2 quantum dots. The fluorescent MoS2 quantum dots–Fe3+ probe has good performances and provides a novel, convenient and effective approach for the detection of Fe3+ of extremely low concentrations.

Preparation of CeO₂-Quantum Dots/Cu₂O Nanocomposites with Enhanced Photocatalytic Properties.

To improve the efficiency of photocatalysts, a composite of CeO2-quantum dots/Cu2O (CeO2-QDs/Cu2O) was prepared through a one-step hydrothermal procedure in alkaline carbonate solution with Cu2(OH)2CO3 and Ce(NO3)3. 6H2O as precursors and glucose as reducing agent. The morphologies and structures of the prepared photocatalysts were well characterized utilizing Transmission Electron Microscopy (TEM), X-ray Diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS) and UV-Vis Diffuse Reflectance Spectrophotometer (DRS). The results indicated that the CeO2-QDs with 5 to 10 nm diameters were well dispersed and had a good contact with Cu2O. As observed in the photocatalytic experiments, Rhodamine B could be degraded more effectively under simulated sunlight using CeO2-QDs/Cu2O as the photocatalysts. Also, the obtained photocatalytic kinetics constant was higher than that in the experiments using CeO2 or Cu2O nano particles as photocatalysts. The enhanced photocatalytic activities might be attributed to the efficient separation of photo-generated charge carriers with the help of the p-n heterojunction and the morphology of quantum dots.

Hydrothermal synthesis of mesoporous TiO2–ZnO nanocomposite for photocatalytic degradation of methylene blue under UV and visible light

Mesoporous ZnO–TiO2 was synthesized successfully by a one-step hydrothermal procedure using titanium sulfate and Zinc nitrate hexahydrate as precursors, and Pluronic P123 as a template. The prepared ZnO–TiO2 materials were heat treated at 400, 600, 800 and 1000 °C to remove the template and increase the degree of crystallization. Field emission scanning electron microscopy, wide angle X-ray diffraction, Fourier transformed infrared spectroscopy, transmission electron microscopy and N2 adsorption–desorption experiments were used to characterize the synthesized powders. Comparison photocatalytic investigations for the prepared materials and commercially available P25 were carried out under identical UV and visible light to understand the effect of the achieved phases and surface area on photocatalytic rate constant and percentage degradation. Results show that the sample which was heat treated at 800 °C (S-800) presents a very high performance under visible light and around 60% of the methylene blue (MB) solution can be degraded by this catalyst in spite of its low surface area. The high efficiency of this sample under visible light can be related to its high degree of crystallinity, formation of anatase and titanium–zinc oxide phases and interfacial coupling between ZnO and TiO2 nanoparticles.

Preparation, evaluations and operating conditions optimization of nano TiO2 over graphene based materials as the photocatalyst for degradation of phenol

The preparation of the TiO2@graphene nanocomposites is significant due to its applications in the various industries such as sensor and catalytic purposes. In this study, the TiO2 and graphene-based nanocomposites have been synthesized via a simple one-step hydrothermal procedure by use of two precursors for graphene in water and ethanol as the solvents. Our fabricated photocatalysts are eco-friendly and can be recovered easily. Besides, a comparative study between graphene (GR) and graphene oxide (GO) as the graphene precursors for the photocatalytic degradation of phenol was performed. The obtained TiO2 and graphene-based nanocomposites were characterized by XRD, FESEM, EDX, FTIR, BET, NH3-TPD, PL, Raman, EDS and TGA techniques. In addition, the central composite design coupled with the response surface methodology by the Design Expert software was employed to design the experiments, optimization, and modeling of phenol decomposition. The influences of the process variables including the; solution pH, initial phenol concentration and photocatalyst amount on phenol degradation were investigated by the response surface method. In order to examine the provided model, an analysis of variance was performed for linear and quadratic equations for GO and GR-based photocatalysts in which satisfy the statistical criteria. The titanium-graphene nanocomposites has been demonstrated more photocatalytic performance than bare TiO2. It was found that a strong coupling between TiO2 nanoparticles and graphene sheets was formed. As compared with the pristine TiO2, the photocatalytic performance of the selected GO-based catalyst improved about 28% and GR-based photocatalyst increased about 15% for degradation of phenol. The empirical model and optimum conditions for the phenol degradation were obtained. Moreover, the as-synthesized photocatalysts can be recovered easily and reuse several times through the phenol degradation.

Direct growth of CuCo2S4 nanosheets on carbon fiber textile with enhanced electrochemical pseudocapacitive properties and electrocatalytic properties towards glucose oxidation

Flexible and wearable electronic devices with excellent performance have been desired for making the next generation of electronic products. Herein, the synthesis of CuCo2S4 nanosheets on flexible carbon fiber textile (CFT) by a facile one-step and scalable hydrothermal procedure is reported, which is free from the sulphurization process used in the conventional synthesis of mixed metal sulphospinels. The as-prepared CuCo2S4 nanostructures on CFT can provide rich reaction sites and short ion diffusion paths. The CuCo2S4 nanosheets are employed as the free-standing electrodes for two different applications: high-performance supercapacitors and non-enzymatic glucose sensors. When employed as a flexible electrode material for supercapacitors, the electrode presents ultrahigh performance in energy storage with a specific capacitance of 3321.6 F g-1 at 5 A g-1, which is attributed to the suitable mass loading and special morphology of the as-prepared nanosheets. Remarkably, a specific capacitance of 2931.4 F g-1 is still retained at the high current density of 30 A g-1, suggesting its excellent rate capability. The specific capacitance retains 87.1% after 3000 cycles, reflecting excellent cycling performance. For real applications, a flexible symmetric supercapacitor is assembled based on CuCo2S4 nanosheets, which achieves a high energy density of 64.6 W h kg-1 at 499.7 W kg-1 and a maximum power density of 2081.5 W kg-1 at 45.1 W h kg-1. Besides serving as a free-standing electrode for non-enzymatic glucose sensors, CuCo2S4 nanosheets have remarkable electrocatalytic activity towards glucose oxidation with a high sensitivity of 3852.7 μA mM-1 cm-2 and an extraordinary linear range up to 3.67 mM. The experimental results suggest that CuCo2S4 nanosheets are more suitable for non-enzymatic glucose sensors than the related single/binary transition metal oxides/sulfides. Such a superior performance demonstrates that CuCo2S4 nanosheets hold great potential for use as flexible multifunctional electronic devices including supercapacitors and non-enzymatic glucose sensors.

Hyaluronic-Acid-Assisted Facile Synthesis of MnWO4 Single-Nanoparticle for Efficient Trimodal Imaging and Liver–Renal Structure Display

Multimodal imaging nanoparticles that integrate different imaging modalities into one system could provide complementary and detailed imaging information to satisfy the request of precision medicine. However, most multimodal nanoparticles suffer from multistep synthesis and complicated compositions, which hinder their practical application in biomedical research. Therefore, development of a facile method to prepare a single-nanoparticle contrast agent to achieve multimodal imaging is of significance. In this paper, hyaluronic-acid-modified manganese tungstate nanoparticles (HA-MnWO4 NPs) were successfully synthesized via a facile one-step hydrothermal procedure for efficient T1/T2-weighted MR and CT trimodal imaging in vivo. In the single-nanoparticle, manganese (Mn) with five unpaired electrons offers strong relaxation for MR imaging, while tungsten (W) with high atomic number provides high X-ray attenuation coefficient for CT imaging. Furthermore, HA-template synthesis endows the HA-MnWO4 nanoparticle w...

Facile one-step extraction and oxidative carboxylation of cellulose nanocrystals through hydrothermal reaction by using mixed inorganic acids

A facile and efficient approach to prepare carboxylated cellulose nanocrystals (CCNCs) is presented through a novel one-step hydrothermal procedure by using a mixed acid system of hydrochloric acid and nitric acid (HCl/HNO3). The as-prepared cellulose nanoparticles were characterized by scanning electron microscopy, wide angle X-ray diffraction, conductometric titrations, Fourier transform infrared spectrometry and thermal gravimetric analysis. The results showed that the combination of the mixed acid and hydrothermal reaction can speed up the process of CCNC preparation, and then high quality of the product could be obtained at relatively low acid concentration. It is found that the addition of nitric acid could not only promote the conversion of surface groups on the cellulose nanocrystals (CNCs), but also have significant influences on the yield, particle size and microstructure of CNCs. For the volume ratio of HCl/HNO3 of 7:3, the as-prepared CCNCs exhibited the largest length to diameter ratio and narrowest dimension distributions as well as maximum degree of oxidation of 0.12. In addition, high dispersion stability for the CCNCs could be observed due to the existence of negative carboxyl groups. This approach based on one-step oxidative carboxylation greatly simplified the preparation of CCNCs with high yield and high crystallinity under mild hydrothermal condition.

High rate and high capacity lithiation of rGO-coated Co2(OH)2CO3 nanosheet arrays for lithium-ion batteries through the involvement of CO32−

RGO-coated Co2(OH)2CO3 nanosheet arrays, mixed with a few CoO nanowires, were synthesized and deposited on copper foil directly via a simple one-step hydrothermal procedure. Benefited from its unique chemical composition and spatial structure, the obtained samples exhibited high performance as anode material for Lithium ion batteries, which delivered a very high reversible capacity of 2,100mAhg−1 at 100mAg−1 after activation and even as high as 1,240mAhg−1 at a much higher charge/discharge current of 5000mAg−1. Additionally, the composite electrode exhibited a high cycling stability, 85% of the initial capacity was remained after 100 cycles test at 1,000mAhg−1. HRTEM analysis indicated that CO32− was involved into the energy storage process, which should be the key factor of such high capacity, while the covered layer of rGO and the synthesis route of directly deposition were suspected to play very important roles on the high stability and high power density.

Sensitive fluorescence and chemiluminescence procedures for methamphetamine detection based on CdS quantum dots

Two novel, simple and sensitive fluorescence (FL) and chemiluminescence (CL) procedures were established for methamphetamine (MA) determination. l-Cysteine capped CdS quantum dots (QDs) were synthesized by a simple one-step hydrothermal procedure and characterized by their specific absorption and emission spectra. The structure and morphology of QDs were investigated using X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM) and scanning electron microscope (SEM). It is found that the prepared CdS QDs have a remarkable promoting effect on rhodamine B (RhoB)-cetyltrimethylammonium bromide (CTAB)-KMnO4 CL reaction. Based on this influence, a new efficient CL system was introduced. On the other hand, the FL and CL emission intensities of QDs undergo a remarkable alteration in the presence of low quantities of MA. The optimization of the effective parameters was performed and the high sensitivity was obtained in 0.013molL−1 Tris buffer at pH=6.5 with 0.2mmolL−1 CdS QDs. In this condition, MA had a notable linear quenching effect on the FL emission of QDs which formed the basis of simple FL probe for sensitive determination of MA in the range of 6.7–400ngmL−1. Also, MA can remarkably enhance the intensity of developed CL system. Under the optimized conditions (0.15molL−1 H2SO4, 0.15mmolL−1 RhoB, 0.13mmolL−1 QDs, 0.3mmolL−1 CTAB and 0.4mmolL−1 KMnO4), the improved CL intensity was proportional to the concentration of MA in the range of 0.25–125ngmL−1 with limit of detection (3s) of 0.086ngmL−1, which is over 20 times better than the introduced FL method. The developed FL and CL methods were exploited for accurate determination of MA in human urine samples.

Synthesis of cross-linked graphene aerogel/Fe2O3 nanocomposite with enhanced supercapacitive performance

In this work, cross-linked graphene aerogel (CL-GA) and its composite with Fe2O3 nanoparticles (NPs) were synthesized through a one-step hydrothermal procedure by using p-phenylenediamine (PPD). Structural characterizations revealed that in the preparation of the composite PPD acts as a cross-liker and provides high surface area by decreasing restacking of graphene sheets and functions as nitrogen source simultaneously. The electrochemical characteristics of the nanocomposite were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS) and Fast Fourier transform continues cyclic voltammetry (FFTCCV). The results show that cross-linked graphene aerogel/Fe2O3 (CL-GA/Fe2O3) nanocomposite displays enhanced supercapacitive performance, where it has capacitance of 445 at 1Ag−1, high energy density of 63WhKg−1, and 89% capacitance retention after 5000 cycles in 3M KOH. Presence of PPD considerably improved supercapacitive performance of nanocomposite as a result it could be promising material in synthesis of efficient graphene/metal oxide-based electrode material for high performance supercapacitors.

Enhanced visible-light-driven photocatalytic performance of mesoporous W-Ti-SBA-15 prepared through a facile hydrothermal route

A facile and one-step hydrothermal procedure was adopted to fabricate a series of W-Ti-SBA15 composites (WTS). These as-prepared composites were systematically characterized by a collection of analytic and spectroscopic techniques. It was found that dual phases of titanium and tungsten species coexisted in mesoporous structures of p6 mm hexagonal symmetry. In addition, these composites were visible-light responsive and exhibited enhanced photocatalytic capability toward degradation of Rhodamine B (RhB) and 2,4-dichlorophenol (2,4-DCP) upon visible-light irradiation in comparison to samples containing single component of titanium or tungsten species. Specifically, the best candidate, sample 8%WTS0.7, had the largest apparent reaction rate constant that was nearly 1.2, 2.1, 2.2, and 5.7 times as high as those of 8%WS, TS0.7, WO3/TiO2, and N-TiO2, respectively. The enhancement of photocatalytic performance was mainly attributed to the well-matched band structures of both components and strengthened visible light adsorption ability, originating from the combination of titania with highly acidic WO3 in SBA15 matrix with large specific surface areas. Active radical species were detected by trapping experiments and a possible photocatalytic mechanism was thus proposed. (C) 2016 Elsevier B.V. All rights reserved.

One-step hydrothermal synthesis of ZnS-CoS microcomposite as low cost counter electrode for dye-sensitized solar cells

Herein, we report a one-step hydrothermal procedure to prepare ZnS-CoS microcomposite which was employed as counter electrode (CE) for dye-sensitized solar cells (DSSCs). The microcomposite exhibits a morphology with ZnS microspheres decorated with CoS nanoparticles, and the decoration effect on electrocatalytic activity of prinstine ZnS toward I−/I3− redox couple was investigated with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. Experimental results show that ZnS-CoS microcomposite exhibits remarkably enhanced electrocatalytic activity compared with that of pristine ZnS in catalyzing the reduction of I3−, and the electrocatalytic activity enhancement closely depends on Co/Zn molar ratio. As a result, the optimized DSSC using ZnS-CoS with a Co/Zn molar ratio of 3: 7 as CE exhibits a highest power conversion efficiency of 6.11%, in comparison with the reference device using Pt CE which shows an efficiency of 7.27%. The enhanced performance compared with DSSC using pristine ZnS CE which has an efficiency of 0.59% can be attributed to the introduction of more electrocatalytic active sites in ZnS-CoS microcomposite. Our study thus provides an effective approach to improve electrocatalytic activity of ZnS and proves its potential suitability as CE for the fabrication of DSSCs.

One-step synthesis of fluorescent silicon quantum dots (Si-QDs) and their application for cell imaging

Novel fluorescent silicon quantum dots (Si-QDs) were synthesized by a one-step hydrothermal procedure using (3-aminopropyl)trimethoxysilane (APTES) as a silicon source and sodium ascorbate (SA) as a reducing agent.

Photocatalytic activity, surface area and phase modification of mesoporous SiO2–TiO2 prepared by a one-step hydrothermal procedure

A one-step hydrothermal synthesis process was developed to prepare ordered mesoporous titania–silica materials by using TEOS and TTIP as silica and titania sources, respectively, as well as P123 as a structure-directing agent in acidic conditions. The synthesized materials were hydrothermally treated at various temperatures (70, 100 and 130°C) and subsequently calcined at 600, 800 and 1000°C. Small-angle X-ray scattering (SAXS), Field Emission Scanning Electron Microscopy (FESEM), Wide angle X-ray diffraction (WAXRD), Fourier transformed infrared spectroscopy (FTIR) and N2 adsorption–desorption experiments have been used to characterize the mesoporous materials, which were subsequently evaluated in terms of photocatalytic efficiency. The results show that hydrothermal and calcination temperatures can change surface area, phase composition as well as degree of crystallinity dramatically resulting in varying photocatalytic performance. Although higher hydrothermal and calcination temperatures will result in lower surface area, a higher degree of crystallinity can be achieved which lead to improved photocatalytic properties. Very high calcination temperatures (1000°C) sharply reduce surface areas in the systems resulting in inhibiting photocatalytic efficiency.

Zn2SiO4urchin-like microspheres: controlled synthesis and application in lithium-ion batteries

Three-dimensional Zn2SiO4urchin-like microspheres have been fabricated by a one-step hydrothermal procedure.