Sol-gel Hydrothermal Process Research Articles

Silver nanoparticles-promoted bismuth titanate perovskite nanosheets photocatalyst for water purification

Photocatalysis is a recognized approach in the detoxification of pollutants and in water splitting. Such process is more appealing when it is driven by visible or solar light. In this context, we synthesized bismuth titanate perovskite oxide (Bi4Ti3O12, BTO) photocatalyst by sol–gel hydrothermal process. The resulting BTO materials was affected by the titania source and by the synthesis medium pH parameter. Titanium butoxide [Ti(n-BuO)4] was much better than titanium isopropoxide [Ti(i-PrO)4] in producing regular nanosheets with higher surface area, while 75 ml of 5.0 M sodium hydroxide was the optimum concentration for the synthesis of regular, thin, porous, almost equal size nanosheets. The photocatalytic activity of BTO was improved by loading silver nanoparticles (AgNPs) by photo-assisted reduction. The optimum weight percent of loading AgNPs was found to be 1.5 % because it led to the highest light absorbance, the smallest band gap energy, the minimum rate of electron-hole recombination. The photocatalytic degradation efficiency of 1.5 wt% Ag/BTO reached as high as 99.0 % of rhodamine B (RhB, 100 ml, 6 ppm of initial concentration) under 70 min of irradiating visible light (>420 nm). Moreover, pH had a strong influence on the photocatalytic activity of 1.5 wt% Ag/BTO, with pH = 3.0 was the optimum, owing to its impact on the interaction between the positively-charged photocatalyst surface and the negatively-charged RhB molecules. It was found that superoxide radicals played key role in the photocatalytic activity.

Ag Doping and rGO Coupling of TiO<sub>2</sub> within Polysiloxane Matrix for the Ecofriendly Development of High-Performance Cotton Fabric

In this work, TiO2 was applied to cotton fabric by a sol–gel-hydrothermal process. A combination of 3-(trihydroxysilyl) propyl methylphosphonate monosodium salt solution (TPMP) and (3-aminopropyl)triethoxysilane (APTES) was used as a matrix to enhance the interfacial interaction between TiO2 and surface of the cotton fibres. During the hydrothermal treatment, silver nitrate (AgNO3) or reduced graphene oxide (rGO) were added to produce Ag-doped TiO2- or rGO-coupled TiO2-coated textiles. The successful application of all investigated components on cotton fabric was confirmed by the analysis of SEM and EDS. The results of UPF determination and self-cleaning activity showed excellent performance of both studied nanocomposite coatings, whereas the use of rGO proved to be better than Ag.

Preparation of aerogel Mg(OH)2 nanosheets by a combined sol–gel-hydrothermal process and its calcined MgO towards enhanced degradation of paraoxon pollutants

Preparation of aerogel Mg(OH)2 nanosheets by a combined sol–gel-hydrothermal process and its calcined MgO towards enhanced degradation of paraoxon pollutants

Structure and electrical properties of BCZT ceramics derived from microwave-assisted sol\u2013gel-hydrothermal synthesized powders

A novel microwave-assisted sol–gel-hydrothermal method was employed to rapidly synthesize Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powders. The effects of reaction time on the structure, crystallinity, purity and morphology of the products were investigated. The results of XRD, FTIR, SEM and TEM indicated that BCZT powders could be obtained in even 60 min at a low synthesis temperature of 180 °C, which were well-crystallized with stoichiometric composition and uniform grain size (~ 85 nm). BCZT ceramic derived from the rapidly-synthesized powders had a dense microstructure and good electrical properties (εm = 9579, d33 = 496 pC/N, 2Pr = 25.22 µC/cm2, 2Ec = 7.52 kV/cm). The significant electrical properties were closely related to the high activity of the BCZT powders, resulting from the rapid microwave-assisted sol–gel-hydrothermal process.

Preparation of Rutile TiO<sub>2</sub> Film by Low Temperature Hydrothermal

In this paper, a simple and pollution-free low temperature hydrothermal method for preparing rutile phase TiO2 film was proposed. When TiCl4 solution hydrolyzed in ice-water mixed DI water, rutile TiO2 can be prepared at a low temperature 70 °C, which is much lower than those of conventional Sol-Gel methods and hydrothermal process. XRD was carried out to analyze the crystal structure and confirmed the TiO2 film we prepared was pure rutile phase. The surface morphology was characterized using AFM. And XPS was also carried out to illustrate the chemical state of the elements.

Preparation and characterization of porous (Si$$_{1-x}$$Ti$$_{{x}}$$)$$\hbox {O}_{\mathrm {{2}}}$$ (x $$\le $$ 0.25) prepared by sol–gel hydrothermal process

An experimental strategy was developed to obtain ( $$\hbox {Si}_{1-x}\hbox {Ti}_{x})\hbox {O}_{\mathrm {2}}$$ ( $$x \le 0.25$$ ) porous materials via the sol–gel hydrothermal process. The sol was prepared from Si(OEt) $$_{\mathrm {4}}$$ (TEOS), Ti(OBu) $$_{\mathrm {4}}$$ (OBu: $$\hbox {OCH}_{\mathrm {2}}\hbox {CH}_{\mathrm {2}}\hbox {CH}_{\mathrm {2}}\hbox {CH}_{\mathrm {3}})$$ , anhydrous ethanol, deionized water and nitric acid. The reagents were mixed at room temperature (293 K) to obtain a homogeneous colourless liquid which was subjected to a hydrothermal process at 473 K using a stainless steel container. Finally, the material obtained was treated at 873 K in air. The surface area of the treated solids was determined by $$\hbox {N}_{\mathrm {2}}$$ adsorption/desorption isotherms. The corresponding average pore diameter was evaluated using the Barret, Joiner and Halenda and Horvath-Kawazoe methods. Porous structures were obtained, in which the average pore diameter of the microporous ones was 1.4 nm. The characterization techniques employed were Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, Raman spectroscopy, scanning electron microscopy, thermal gravimetric analysis, differential scanning calorimetry and UV–Vis diffuse reflectance spectroscopy. The Si–O–Ti bonds were detected by FTIR.

Low temperature crystal growth of lead-free complex perovskite nano-structure by using sol-gel hydrothermal process

The fabrication of lead-free oxide perovskite materials ensures no toxic or harmful waste being spread into the environment but usually calls for a high-temperature synthesis process. These materials have emerged to be one of the most promising materials and are currently of great technological interest due to their extraordinary potential in various energy harvesting applications. They are able to form a stable structure but the method of synthesis of nanoparticles is of paramount importance in order to determine its properties. However, the development of an environmentally benign chemical process to synthesize perovskite material in the laboratory at low-temperature is a huge challenge. The low-temperature synthesis route not only yields high purity, pure phase, less wastage of the sample, less agglomeration of the nano-particles but most importantly is highly energy efficient and ecologically innocuous. Oxide Perovskite like Barium Titanate (BT) is known for its remarkable piezoelectric and ferroelectric properties although the method of synthesis of BT with different dopants has a significant influence on the structural properties of these materials.

Structural and electrical properties of BCZT ceramics synthesized by sol–gel-hydrothermal process at low temperature

A novel method, sol–gel-hydrothermal process, was employed to prepare Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powders at a rather lower temperature of 180 °C. The effects of synthesis time on the structure, morphology and size distribution of the powders were studied by the means of XRD, SEM and FTIR. BCZT powders could be obtained at a suitable synthesis time of 12 h, which were well-crystallized and compositional uniform with an average particle size of 93 nm. BCZT ceramics sintered from the synthesized powders had a dense microstructure with a density of 5.59 g/cm3 (> 95%) and excellent properties (2Pr = 25.12 μC/cm2, 2Ec = 4.31 kV/cm, d33 = 492pC/N, er = 9173), indicating the high activity of the BCZT powders by sol–gel-hydrothermal process.

ZnO Q-dots as a potent therapeutic nanomedicine for in vitro cytotoxicity evaluation of mouth KB44, breast MCF7, colon HT29 and HeLa cancer cell lines, mouse ear swelling tests in vivo and its side effects using the animal model

Nanoformulations derived from fine porous ZnO quantum dot nanoparticles (QD NPs) can offer strong potential medical applications; especially in cancer therapy. ZnO QD NPs was synthesized by sol–gel hydrothermal process, fast cold quenching and further smart surface functionalization methods to obtain ultrasmall size (1–4 nm) NPs. ZnO nanopolymer, a wetting agent, PEG co-solvent and water/oil emulsion stabilizer were considered in our nanofluid formulation. The resulting nanofluid was characterized by SEM, FTIR, photoluminescence, band gap energy, zeta potential and UV–Vis spectroscopy. The cytotoxic effects on the growth of four cancer cell lines were evaluated by MTT assay. The IC50 (µg/ml) values of 30, 41, 40 and 35 for KB44, MCF-7, HT29 and HeLa cells, respectively, after 48 h of nanoformulation treatment suggested the cytotoxic effect of this nanoformulation on these cell lines in a concentration-dependent manner (p < .05). ZnO nanofluid destroyed cancer cell lines more efficiently than the normal HFF-2 (IC50 = 105 µg/ml). The reduction in cell viability in response to ZnO nanofluid treatment induced apoptosis in the cultured cells. Skin sensitization test plus antibacterial activity were also measured. Side effect tests on 70 white mice in vivo resulted in only 3–4 abnormal situations in hepatic tissue section possibly due to the idiosyncratic drug reactions.

A double-layered photoanode made of ZnO/TiO2 composite nanoflowers and TiO2 nanorods for high efficiency dye-sensitized solar cells

We present a simple sol-gel hydrothermal process for the fabrication of a double-layered structure composed of a TiO2 nanorod overlayer and TiO2 nanoparticle-embedded ZnO nanoflower (ZNFs@TNPs-TNRs) underlayer. The ZNFs@TNPs-TNRs was used as a photoanode in dye-sensitized solar cells (DSSCs) and their photovoltaic performance was analyzed. The ZNFs@TNPs-TNRs can enhance the adsorption of N719 dyes, charge transport, and light scattering. The cell performances can be maximized by optimizing thickness ratio and total thickness of the double-layered photoanode, and the preliminary results demonstrate that a promising power conversion efficiency (PCE) of 8.01% is determined on the DSSC with ZNFs@TNPs-TNRs anode, yielding a 28.9% enhancement in the PCE in comparison to pristine TiO2–P25 nanoparticle-based DSSC.

Application of new ZnO nanoformulation and Ag/Fe/ZnO nanocomposites as water-based nanofluids to consider in vitro cytotoxic effects against MCF-7 breast cancer cells

Novel formulations of nanocomposites derived from ZnO nanoparticles have provided potential biomedical applications as a new strategy for treatment of breast cancer. In this research, two types of ZnO nanomaterials were synthesized by sol–gel hydrothermal process and co-precipitation containing fast quenching and also surface modification methods. The cytotoxic effects on growth of the breast cancer cell lines MCF-7 were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell viability of the breast cancer cell line MCF-7 was reduced with increasing ZnO nanofluid concentrations at 48 and 72 h of treatment. The IC50 value of MCF-7 cells after 72 h of treatment with the first product ZnO (a) and second one ZnO (c) were measured as 51.02 and 48.63 μg/ml, respectively (P < 0.05).

ZnO-Decorated Carbon Nanotube Hybrids as Fillers Leading to Reversible Nonlinear I-V Behavior of Polymer Composites for Device Protection.

Overvoltage protection is becoming increasingly important because of miniaturization and multifunctionality of electronic devices. Flexible, easily processable materials with nonlinear and reversible I-V behavior are highly desired. In this study, hybrid nanoparticles of ZnO-decorated carbon nanotubes (CNT-ZnO) were synthesized via a sol-gel hydrothermal process employed in an epoxy matrix to prepare composites. Microstructure analysis demonstrated that ZnO nanoparticles were well-bonded to the surface of CNT. The CNT-ZnO/epoxy composites exhibited nonlinear I-V behavior under increasingly applied voltage with a nonlinear coefficient of 5.01 (10 wt % filler loading). More importantly, the composites possessed excellent reversibility from dielectric to conductor and vise versa in the recycling of increase and decrease of applied electric field, in contrast to the poor recoverability of pure CNT-filled epoxy. The mechanism of the nonlinear I-V behavior and reversibility was investigated and discussed. A simple circuit was fabricated, which verified well the protection function of the CNT-ZnO/polymer composites.

Chromium-modified Bi4Ti3O12 photocatalyst: Application for hydrogen evolution and pollutant degradation

Novel chromium-modified Bi4Ti3O12 photocatalyst (Bi4Ti3−xCrxO12, x=0–0.5) was developed by a facile sol-gel hydrothermal process with low reaction temperature. The XRD, SEM, TEM, and XPS analyses indicated the formation of the single-crystalline, rectangular, and {001} facet-exposed Bi4Ti3−xCrxO12 nanosheets. Their average side lengths and thickness progressively decreased with increase in the Cr content, and the minimal side length and thickness for Bi4Ti2.6Cr0.4O12 are 95 and 15nm, respectively. With more addition of Cr content, sample showed significant particle agglomeration even though some of small nanosheets were observed. The UV–vis study revealed a reduction in the band gap of Bi4Ti3−xCrxO12 and enhanced photoabsorption in the visible light region, compared to the calcined Bi4Ti3O12. The photoluminescence and electrochemical impedance spectroscopy results displayed a decreased recombination of photogenerated charges in the Cr-modified Bi4Ti3O12 compared to Cr-free one. The photocatalysts were optimized for both maximum hydrogen generation from alcohol-water mixture and methyl orange (MO) degradation in an aqueous solution under visible light irradiation. As a result, addition of Cr effectively improves photocatalytic performance of Bi4Ti3O12. Bi4Ti2.6Cr0.4O12, the optimal photocatalyst, showed highly stable reusability as a hydrogen generator. The photocatalyst reached as much as 117μmolg−1h−1 hydrogen evolution rate under 240min of irradiation, which was ∼2.85 times that of the Bi4Ti3O12 nanosheet. The hydrogen yields of the Bi4Ti2.6Cr0.4O12 using various alcohol-water mixtures decreased in the order: isopropanol>ethanol>methanol. The optimal photocatalyst also showed up to 0.01003min−1 of average apparent rate constant in the MO degradation, about 3 times that of the Cr-free nanosheet. The improved photocatalytic performance of the Cr-modified Bi4Ti3O12 is attributed to its strong absorption in visible light region, small nanosheet size, exposed {001} facets as well as the low recombination rate or the high separation efficiency for photogenerated electron-hole pairs.

One-step synthesis of flower-like carbon-doped ZrO2 for visible-light-responsive photocatalyst

Carbon-doped ZrO2 photocatalysts with three-dimensional (3D) flower-like architecture were successfully prepared by one-step sol–gel-hydrothermal process using zirconatrane precursor for use as a high-performance material for the methylene blue (MB) degradation and the enhanced photoelectrochemical (PEC) properties compared with zero-dimensional ZrO2 nanoparticles and commercial TiO2 nanoparticles (P25). These mesoporous microflower structures consisted of ZrO2 nanopetals, implying good intercrystalline connections and effective light absorption. The synergy of carbon doping and flower-like hierarchical 3D architecture greatly promoted the photocatalytic efficiency for MB degradation under visible light. In view of these advantageous features inherited from the carbon-doped ZrO2 with flower-like structure can be used as photoanode materials. A high photoconversion efficiency of 3.17% was achieved from flower-like carbon-doped ZrO2, which increased by 575% and 1168% compared with those of the PEC devices based on ZrO2 nanoparticles and P25, respectively.

Enhanced photocatalytic performance over Bi4Ti3O12 nanosheets with controllable size and exposed {0 0 1} facets for Rhodamine B degradation

Single-crystalline Bi4Ti3O12 nanosheets with rectangular shape and exposed {001} facets were successfully synthesized via a sol–gel hydrothermal process for the first time. Their average side lengths were around 100 and 150nm, respectively, and thickness ∼20nm. As a result, the Bi4Ti3O12 nanosheets reached as high as 79.2% of photodegradation efficiency of Rhodamine B (6ppm of initial contentration) under 90min of sunlight irradiation, which was ∼3 times that of conventionally calcined Bi4Ti3O12. The synthesized nanosheet catalyst also exhibited high reusability for the photodegradation reaction due to the chemical stability of its single crystalline structure. Moreover, photodegradation efficiency of the Bi4Ti3O12 nanosheets increased as decreasing Rhodamine B concentrations in the range of 6–20ppm or pH values in the range of 3.1–11.2. Addition of 0.1M SO42− to reaction solution increased almost 6% of photodegradation efficiency of Bi4Ti3O12 nanosheets under 90min of illumination. These results demonstrate the superiority of the novel synthetsis technique for preparing bismuth titanate photocatalyst. The much-enhanced photocatalytic performance of Bi4Ti3O12 nanosheets is attributed to their increased active surface sites, efficient separation and transfer of photogenerated charge carriers and greatly suppressed recombination rate of e−/h+ pairs, arising from their large specific surface area, small particle size, single crystallinity, and specific exposed facets.

Scandium and gadolinium co-doped BaTiO3 nanoparticles and ceramics prepared by sol–gel–hydrothermal method: Facile synthesis, structural characterization and enhancement of electrical properties

A facile sol–gel–hydrothermal process was used to synthesize Scandium and Gadolinium co-doped BaTiO3 nanocrystals in this paper. Similar to the previous studies, a single-phase solid-solution structure is hard to achieve for BaTiO3 materials doped with rare-earth ions like Sc- and Gd- via solid-state method. Here, uniform Ba1−xTi1−xGdxScxO3 (0≤x≤0.04) nanoparticles (NPs) with single-phase solid-solution cubic structure and average particle size of 30–40nm were obtained and Ba1−xTi1−xGdxScxO3 pellets prepared from as-synthesized nanopowders can be sintered at a lower temperature of 1150°C. The internal structures, chemical constitution and morphology were characterized by FT-IR spectra, XRD, TEM, HRTEM, Raman spectra and SEM analysis. The results clearly demonstrated that Sc3+ and Gd3+ have entered into the BaTiO3 lattice and led to structural distortion in a short range and all samples were single-phase tetragonal structure at room temperature. Additionally, the dielectric temperature stability was enhanced with Sc3+ and Gd3+ as dopants, since the single-phase BaTiO3 ceramics exhibited broadened dielectric peaks, decline of Curie temperature as well as low dielectric loss below 0.02. Ceramics containing 3mol% Sc3+ and Gd3+ can exhibit the best dielectric behaviour of εr ~1700 and Tc=32°C in this work.

Structural characterisation of slightly Fe-doped SrTiO3 grown via a sol–gel hydrothermal synthesis

A detailed structural study of the incorporation of Fe into SrTiO3 nanoparticles is reported. Slightly iron-doped strontium titanate nanoparticles with 0, 1, 3 and 5 mol% concentration of iron were grown using a sol–gel hydrothermal process and characterised using Raman scattering, X-ray photoelectron and X-ray diffraction spectroscopy. The amorphisation of the nanostructures was observed as the iron content increased, which was confirmed by the TEM images. The XPS results indicated that the oxidation states of the Sr atoms were maintained in 2+. However, a mixture of Fe3+ and Fe4+ atoms was observed as the Fe content increased, resulting in a significant number of oxygen vacancies in the perovskite structure. The analysis of Raman spectra indicated that the intensity, linewidth and frequency shift of the TO4 phonon can be used as an indicator of the Fe content as well as a local temperature probe for future thermal analysis. Temperature evolution of the Raman spectra of STO:Fe 1 mol%. The peaks with star correspond to the second-order processes. (b) Temperature dependence of the TO4 phonon mode. Blue dots denote measured Raman spectra, and the red solid lines are the Lorentzian fits to respective spectra.

Enhanced efficiency and improved photocatalytic activity of 1 : 1 composite mixture of TiO2 nanoparticles and nanotubes in dye-sensitized solar cell

TiO2-based nanotubes (NTs), nanoparticles (NPs) and composite structural film (50% NP + 50% NT film) were synthesized by sol-gel hydrothermal process. Synthetic indigo dye was used as a sensitizer with the unique combination of electrolyte (EMII + BMII + PMII) and with cobalt sulphide as counter electrode. The structure and morphology of the three films, namely, NP, NT and NPNT is studied through X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorption spectra and incident photon-to-current conversion efficiency (IPCE) of the three films were compared and found to be higher for NPNT film. The efficiency and photocatalytic activity of three films were evaluated. The composite structure showed improved efficiency (1.72%) than NP (1%) and NT films (0.78%). The photocatalytic activity of the three films were measured using organic dye, methylene blue under UV light radiation. The composite structure showed higher dye absorption and higher rate of reaction with time. This paper certainly proves that there are many rooms to focus on the photoanode configuration, which plays a key role to improve the efficiency of dye-sensitized solar cell (DSSC).

Properties of Barium Titanate Thin Films Grown by Sol–Gel-Hydrothermal Process

Properties of Barium Titanate Thin Films Grown by Sol–Gel-Hydrothermal Process

Iron Oxide-based Supercapacitor from Ferratrane Precursor via Sol–gel-Hydrothermal Process

In this study, ferratrane was used as a precursor to prepare iron oxide material via a sol–gel-hydrothermal process for supercapacitor applications. The mixed solution of ferratrane precursor and de-ionized water was transferred into a Teflon-lined stainless steel autoclave and kept at a constant temperature of 200°C for 6h. The as-prepared powder was annealed at 500°C for 2h under an ambient atmosphere. The as-prepared and annealed samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques. The as-prepared powder has a single phase of cubic magnetite (Fe3O4) and then can be transformed into rhombohedral hematite (α-Fe2O3) by annealing at 500°C for 2h. The electrochemical properties of the resultant α-Fe2O3 nanoparticles were evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge in a three-electrode cell. The α-Fe2O3 nanoparticles showed the highest specific capacitance of 532.80 F/g at the current density of 1 A/g and the highest energy density of 74.00 Wh/kg at the power density of 0.50kW/kg.