Non-aqueous Sol-gel Method Research Articles

Size control of C@ZrSiO4 pigments via soft mechano-chemistry assisted non-aqueous sol-gel method and their application in ceramic glaze

The zircon-based encapsulation carbon black (C@ZrSiO4) inorganic pigments with controllable size were successfully prepared by non-aqueous sol-gel method with the assistance of soft mechano-chemistry (SMC) activation precursors. The XRD and FT-IR results showed that the SMC activation enhanced the reactivity of precursors and facilitated the formation of ZrSiO4 phase with the calcination temperature at 900–1050 °C, indicating the successfully synthesis of pure ZrSiO4 phase. The average size of C@ZrSiO4 inorganic pigments significantly declined from 45.20 to 4.50 μm with the increase of SMC activation time of precursors, however, the L* values of pigments increased from 24.11 to 46.35. It was mainly because of the decreased amounts of protected carbon in ZrSiO4 matrix and the enhanced light reflectance, which lead to the slight color change from deep black to gray black tone. The colored glaze samples presented a black hue after applied in the ceramic glaze at 1200 °C. Moreover, the black hue intensity of glazed samples was higher than that of the corresponding C@ZrSiO4 inorganic pigments, indicating the prepared pigments have excellent tinctorial strength and hiding power. These results ensure that the obtained C@ZrSiO4 inorganic pigments possess the outstanding chromatic performance, excellent high-temperature stability, high chemical stability and suitable particle size, and exhibit great potential in the application of the industrial ceramic decoration.

Strong covalent interaction Fe2O3/nitrogen-doped porous carbon fiber hybrids as free-standing anodes for lithium-ion batteries

A simple and novel method that combines the electrospinning technology with nonaqueous sol–gel method is developed to incorporate Fe2O3 nanoparticles into ZIF-8-derived nitrogen-doped highly porous carbon fibers (NPCFs). The size of Fe2O3 nanoparticles is about 5 nm. The interfacial interaction between Fe2O3 and NPCFs is investigated by thermogravimetric analysis, Raman spectrum and X-ray photoelectron energy spectrum. We found that Fe2O3 nanoparticles are anchored strongly in the NPCFs through the Fe–O–C covalent bond. The impact of the Fe2O3 content in the composites on electrochemical performance is also studied. When served as the flexible and free-standing anode of lithium-ion batteries (LIBs), the Fe2O3/NPCFs-66.9% exhibits superior electrochemical performance with the high discharge capacity of 1351 mA h g−1 at 50 mA g−1, remarkable rate capability (337 mA h g−1 even at 5000 mA g−1), and stable cycling performance (1106 mA h g−1 after 100 cycles at 100 mA g−1). The excellent anodic property can be ascribed to the ultra-small size of Fe2O3 nanoparticles, and the one-dimensional (1D) structure combined with the excellent electrical conductivity of NPCFs matrix. Moreover, the robust interfacial interaction Fe–O–C bond can restrain the aggregation of Fe2O3 nanoparticles and accommodate the volume change. This can effectively maintain the integrity of the whole electrode during the long-term cycles. The results show that the composite may be considered as a promising anode material for advanced LIBs.

Synthesis and Photocatalytic Properties of Nitrogen Modified Titanium Dioxide

Summary Pure and nitrogen-doped titanium dioxide (N-doped TiO2) photocatalysts were prepared by non-aqueous sol-gel method by means of the reaction between titanium (IV) chloride (TiCl4) and C6H5CH2 OH (benzyl alcohol), used as precursors and urea serving as a nitrogen source. The phase formation and short-range order of the resulting particles were characterized by X-ray powder diffraction (XRD) and infrared (IR) spectroscopy. The crystallite size of as-prepared composite powders was in the range 12-35 nm. The aim of this work was to investigate the efficiency of N-doped TiO2 as a photocatalyst in degradation of model organic pollutants - dyes Reactive Black 5 (RB5) and Malachite Green (MG), under ultraviolet (UV) and visible (Vis) irradiation. 0ur results indicated that synthesized N-TiO2 nanocomposites slightly improved the photocatalytic activity under UV irradiation, compared to the pure titanium dioxide (TiO2), and had no effect under Vis light illumination.

Synthesis and Characterization of Advanced Nanomaterials: Tin-Doped Indium Oxide (ITO) and Platinium Deposited on Tin-Doped Indium Oxide (Pt/ITO).

This article describes the synthesis and characterization of tin-doped indium oxide (ITO) and platinum nanoparticles deposited on ITO. For different calcination temperatures, the tin-doped indium oxide nanoparticles (ITO NPs) were synthesized successfully by a nonaqueous sol-gel method with indium acetylacetonate and tin bis(acetylacetonate) dichloride in oleylamine as the precursors. The ITO sample that calcinated at 500 °C exhibited a spherical morphology with a narrow range of the particle size distribution (15-20 nm). Moreover, the electrical conductivity of the sample (1.242 S/cm) was higher than many different non-carbon supports. In addition, 20% platinum nanoparticles (Pt NPs) were also deposited uniformly on the ITO supports via chemical reduction process using NaBH4 as the reducing agent. The size of Pt NPs was about 5 nm and the crystalline structure of ITO supports remained unchanged.

Facile preparation of four SnOx-C hybrids with superior electrochemical performance for lithium-ion batteries

SnOx is considered as a promising anode candidate for lithium-ion batteries, but suffers from the low electrical conductivity and severe volume expansion during cycling. To solve these issues, we develop a simple and facile process of incipient wetness impregnation followed by pyrolysis gel molecules to prepare SnOx/mesoporous carbon nanofiber arrays, SnOx/graphene, SnOx/carbon nanotubes and SnOx/three-dimensionally ordered macroporous carbon materials. Notably, SnOx nanoparticles about 5 nm are prepared by a nonaqueous sol-gel method. We also explore the effect of different morphologies and pore structures of four carbon substrates on the electrochemical performance of the composites. Benefiting from the small size of SnOx nanoparticles and the synergistic effect between SnOx and the different carbon matrix materials, SnOx-Carbon electrode materials display excellent rate capability and cycle stability. SnOx/mesoporous carbon nanofiber arrays exhibits the best rate (522 mA h g−1 at 2000 mA g−1) and cycling performances (1327 mA h g−1 after 200 cycles at 100 mA g−1). The superior electrochemical performance, facile synthesized method and low cost of the Sn-based materials exhibit promising application for SnOx/mesoporous carbon nanofiber arrays as anode materials for next-generation lithium-ion batteries. Furthermore, the ex situ X-ray photoelectron spectroscopy studies on this electrode material under different states suggest that the Sn and Li2O could reversibly react to form SnOx during the charging process.

Effect of dopant (Co, Ni) concentration and hydroxyapatite compositing on photocatalytic activity of titania towards dye degradation

In this study, different concentrations of cobalt- and nickel-doped titania nanopowders were synthesized via non-aqueous sol-gel method and comprehensively characterized by several techniques. The photocatalytic activity of samples was evaluated by the photodegradation test of 10 mg L−1 of methylene blue solution under UV irradiation. The photocatalytic efficiency was enhanced by the presence of Co and Ni as dopants in TiO2 lattice compared to undoped titania (97.7%, 98.9%, and 88.0% for 0.05 mol% cobalt-doped, nickel-doped, and undoped titania, respectively). FE-SEM images explained that samples had a uniform spherical shape, with the exception of 2 mol% dopant concentration, which were agglomerated. Furthermore, to suppress agglomeration problem, biphasic composite photocatalysts consisting 2 mol% doped titania and hydroxyapatite (HAp) were prepared by the precipitation of HAp in the presence of doped TiO2. FE-SEM, TEM images and BET results revealed that the composite samples suppressed TiO2 nanoparticles from agglomeration and increased specific surface area. The average size of nanoparticles was 20 nm. Also, higher photocatalytic activity and reaction rate constant were observed for 2 mol% cobalt- (91.0%) and 2 mol% nickel- (67.0%) doped titania/HAp nanocomposites compared to corresponding non-composited samples (58.5% and 49.9% for 2 mol% cobalt and nickel doped titania, respectively) as a result of better adsorption of dye molecules via HAp. The composite samples show photostability even after 4 cycles.

Synthesis and Formation Mechanism of Multicomponent Sb–Nb:TiO2 Mesocrystals

The synthesis of multicomponent mesocrystals represents an emerging strategy for obtaining nanomaterials with unique functionalities as a result of combining porosity and crystallographic order. This study presents the first synthesis of multicomponent Sb–Nb:TiO2 mesocrystals (Sb-mesoNb/TO) by using a microwave-assisted nonaqueous sol–gel method. Structural and chemical analyses, carried out using various transmission electron microscopy techniques, show that Sb-mesoNb/TO are 25–35 nm in size and composed of crystallographically aligned Nb:TiO2 subunits, embedded in a porous amorphous Sb-rich scaffold (Sb-scaffold). On the basis of the characterization of the intermediate products, the formation mechanism is proposed, involving a kinetically controlled particle-based assembly process. The latter is triggered by the occurrence of the Sb-scaffold in the early reaction stages, acting as a support for heterogeneous nucleation of Nb:TiO2 subunits. Subsequently, Nb:TiO2 subunits grow and assemble in a mutual cr...

Microscopic Characterization and Analysis of Electrospun TiO<sub>2</sub>-PVP and TiO<sub>2</sub>-PVDF Fibers

Titanium dioxide (TiO2) is a suitable material to be used in the field of photocatalytic water treatment. In this research, TiO2 membrane fibers were synthesized using a combination of non-aqueous sol gel method and electrospinning technique. Titanium isopropoxide (TTIP) was used as the precursor for the TiO2 filler of the fibers. Both polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were used as the polymer base to obtain the respective membrane fibers. The effects of weight concentration of TTIP as well as the type and molecular weight of the polymer on the morphology of the fibers were studied. Microscopic characterization using field-emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray (EDX) analysis was performed to obtain the morphology and elemental composition of the fibers. Sub-micron range fibers with a continuous network were generally obtained. Fibers that are subjected to post-electrospinning calcination have a lower fiber diameter. Polymer decomposition is shown to occur during calcination which yielded higher purity TiO2 fibers. The use of higher molecular weight polymers can produce a stronger fibre network for membranes.

Upconversion Nanophosphor-Involved Molecularly Imprinted Fluorescent Polymers for Sensitive and Specific Recognition of Sterigmatocystin.

Originated from the bottom-up synthetic strategy, molecularly imprinted polymers (MIPs) possess the inherent ability of selective and specific recognition and binding of the target analytes, with their structural cavities that can match the target molecules in respect to size, shape, and functional groups. Herein, based on the high selectivity of MIPs and the fluorescence properties of the β-NaYF4:Yb3+, Er3+ upconversion nanoparticles, MIPs with both specificity and fluorescent signals are fabricated to recognize trace sterigmatocystin (ST) with high selectivity and sensitivity. The structure analogue of ST, 1,8-dihydroxyanthraquinone (DT), was employed as the template molecule, acrylamide as the functional monomer, 3-methacryloyloxypropyltrimethoxysilane as the crosslinking agent, and a new molecular imprinting technique of non-aqueous sol-gel method is used to synthesize a molecularly imprinted material with high selectivity to ST. Under optimal conditions, the fluorescence enhancement of fluorescent MIPs increased as the concentration of ST increased. In the range of 0.05–1.0 mg L−1, fluorescence enhancement and the concentration showed a good linear relationship with a detection limit of 0.013 mg L−1. Real sample analysis achieved the recoveries of 83.8–88.8% (RSD 5.1%) for rice, 82.1–87.5% (RSD 4.6%) for maize, and 80.6–89.2% (RSD 3.0%) for soybeans, respectively, revealing the feasibility of the developed method.

A general nonaqueous sol-gel route to g-C3N4-coupling photocatalysts: the case of Z-scheme g-C3N4/TiO2 with enhanced photodegradation toward RhB under visible-light.

The g-C3N4-coupling TiO2 photocatalysts with controllable particle size as well as the interface contact were prepared by a general nonaqueous sol-gel method. The structural and morphological features of g-C3N4/TiO2 were investigated through the X-ray diffraction, Fourier transformed infrared spectra, scanning electron microscopy and transmission electron microscopy, respectively. It is found the TiO2 nanoparticles with a size of 7.3 ± 1.6 nm are uniformly anchored on the surface of the g-C3N4 nanosheets in isolation. The photocatalytic properties of as-prepared g-C3N4/TiO2 were tested by degradation of Rhodamine B (RhB) under visible light, and an enhanced activity is observed. The mechanism of the enhanced activity was further investigated through N2 adsorption-desorption isotherms, UV-vis spectra, photoluminescence spectra, photoelectrochemical measurements, radical trapping experiments and X-ray photoelectron spectroscopy. Furthermore, the photocatalytic performances of obtained g-C3N4/TiO2 under sunlight were also evaluated in aspects of degradation efficiency and stability. The results indicate that the obtained g-C3N4/TiO2 is one promising photocatalyst for practical applications. The study of as-prepared g-C3N4/TiO2 also implies that the present method could be a general route of g-C3N4-coupling photocatalysts.

USPIO size control through microwave nonaqueous sol-gel method for neoangiogenesis T2 MRI contrast agent.

Tunable size ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles from 3 to 9 nm coated with polyethylene glycol phosphonate moieties have been designed for neovascularization MRI. USPIO were synthesized using a nonaqueous sol-gel method. An ischemia-reperfusion rat model has been chosen for neo-angiogenesis and scanned on MRI after injection of different sized USPIO. Histological studies have been performed for USPIO localization within the tissue. The magnetic properties and consequently their MRI relaxivities are drastically dependent on the crystalline core size. In vivo MRI spots were observed specifically in the ischemic area. The best MRI contrast within neovascularization is generated by 6 nm nanoparticles proving that compromise between T2 relaxivity and physico-chemical properties is essential for the design of effective MRI contrast agent.

Hierarchical porous photoanode based on acid boric catalyzed sol for dye sensitized solar cells

The hierarchical porous photoanode of the dye sensitized solar cell (DSSC) is synthesized through non-aqueous sol-gel method based on H3BO3 as an acid catalyst and the efficiencies of the fabricated DSSC based on these photoanodes are compared. The sol parameters of 0.17M, water mole ratio of 4.5, acid mole ratio of 0.45, and solvent type of ethanol are introduced as optimum parameters for photoanode formation without any detectable cracks. The optimized hierarchical photoanode mainly contains anatase phase with slight shift toward higher angles, confirming the doping of boron into titania structure. Moreover, the porous structure involves two ranges of average pore sizes of 20 and 635nm. The diffuse reflectance spectroscopy (DRS) shows the proper scattering and blueshift in band gap. The paste parameters of solid:liquid, TiO2:ethyl cellulose, and terpineol:ethanol equal to 11:89, 3.5:7.5, and 25:64, respectively, are assigned as optimized parameters for this novel paste. The photovoltaic properties of short circuit current density, open circuit voltage, fill factor, and efficiency of 5.89mA/cm2, 703mV, 0.7, and 2.91% are obtained for the optimized sample, respectively. The relatively higher short circuit current of the main sample compared to other samples is mainly due to higher dye adsorption in this sample corresponding to its higher surface area and presumably higher charge transfer confirmed by low RS and Rct in electrochemical impedance spectroscopy data. Boric acid as a catalyst in titania sol not only forms hierarchical porous structure, but also dopes the titania lattice, which results in appreciated performance in this device.

Study of the growth of hydrophilic iron oxide nanoparticles obtained via the non-aqueous sol–gel method

The growth process of hydrophilic iron oxide nanoparticles synthesized via the non-aqueous sol–gel method using TEG as high-boiling solvent has been characterized. A model of the growth process is presented, based on a combination of analytical methods, especially XRD, SAXS and TGA. In contrast to previously studied particles synthesized in benzyl alcohol, which grow via nucleation, particles synthesized in TEG grow via a sol–gel-like process. In a first step, an amorphous network is formed, and subsequently, during the compaction of the network, crystalline particles are obtained. The influence of the structural properties on the magnetic behavior was identified by combining various spectroscopic methods.

Relief of Oxidative Stress Using Curcumin and Glutathione Functionalized ZnO Nanoparticles in HEK-293 Cell Line.

To elucidate the effect of zinc oxide nanoparticles (ZnO-NPs) with different surface modifications in relieving the oxidative stress in cultured human embryonic kidney cells (HEK-293) following investigation was performed. Oxidative stress was artificially induced by hydrogen peroxide in HEK-293 cell culture and its management was studied. Alkyl amines modified ZnO-NPs with curcumin and reduced glutathione (GSH) functionalization was used in managing oxidative stress and had shown promising results. ZnO-NPs used in this study were synthesized via non-aqueous sol-gel method and FESEM characterisation showed them of spherical shape of about 20-50 nm size with amine, curcumin and GSH functionalization. UV-visible and FTIR spectroscopic characterizations confirmed functionalization of ZnO-NPs. Decrease in oxidative stress was found with the dose-dependent culture of HEK-293 cells with these functionalized ZnO-NPs. Cell viability and morphology, as observed using AFM and inverted microscope, was retained with the prescribed dosages of the functionalized nanoparticles while at higher dosages they caused cytotoxicity and death. Diethylamine (DEA) modified ZnO-NPs and their functionalization with GSH and curcumin were found more effective in managing oxidative stress in cells. Present study could help in designing economical and bio-compatible functionalized non-toxic nanoparticles designed for managing oxidative stress leading to possible therapeutical and medicinal uses.

Non-aqueous sol-gel synthesis of ultra small persistent luminescence nanoparticles for near-infrared in vivo imaging.

Ultra-small ZnGa2 O4 :Cr(3+) nanoparticles (6 nm) that exhibit near-infrared (NIR) persistent luminescence properties are synthesized by using a non-aqueous sol-gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra-small ZnGa2 O4 :Cr(3+) nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues.

The Effect of Tween® Surfactants in Sol-Gel Processing for the Production of TiO2 Thin Films

Titanium dioxide thin films were deposited using a Tween® surfactant modified non-aqueous sol-gel method onto fluorine doped tin oxide glass substrates. The surfactant concentration and type in the sols was varied as well as the number of deposited layers. The as deposited thin films were annealed at 500 °C for 15 min before characterisation and photocatalytic testing with resazurin intelligent ink. The films were characterised using scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy and UV-Vis spectroscopy. Photocatalytic activity of the films was evaluated using a resazurin dye-ink test and the hydrophilicity of the films was analysed by water-contact angles measurements. Characterisation and photocatalytic testing has shown that the addition of surfactant in varying types and concentrations had a significant effect on the resulting thin film microstructure, such as changing the average particle size from 130 to 25 nm, and increasing the average root mean square roughness from 11 to 350 nm. Such structural changes have resulted in an enhanced photocatalytic performance for the thin films, with an observed reduction in dye half-life from 16.5 to three minutes.

The effect of Brij® surfactants in sol–gel processing for the production of TiO2 thin films

Titanium dioxide thin films were deposited via a Brij® surfactant modified non-aqueous sol–gel method onto fluorine doped tin oxide glass substrates. The number of layers and surfactant concentration and type in the sols was varied. The as deposited films were annealed at a range of temperatures (500–600°C) and times (15–60min) before characterisation and photocatalytic testing. The annealed films were characterised using scanning electron microscope, X-ray diffraction, Raman spectroscopy and UV–Vis spectroscopy. The photocatalytic activity of the films was evaluated using an intelligent dye-ink test and the hydrophilicity of the films was analysed by water-contact angles measurements. The characterisation revealed that the changing surfactant type and concentration had a significant effect on the film microstructure, such as changing the average particle size from 130 to 325nm and increasing the surface roughness of the thin film. Such structural changes led to an increase in the photocatalytic activity with an observed reduction in dye half-life from 16.5 to 3min.

Microwave assisted non-aqueous sol–gel synthesis of LiNiPO4 and its copper doped analogues

A series of single phase LiNi(1−x)CuxPO4 (0 < x < 0.99) was successfully synthesized by non-aqueous sol–gel method followed by microwave (MW) annealing. The advantage of MW short span annealing is obvious from the nanometer sized particles compared to reported microparticles. XRD, IR and SEM studies were conducted to investigate the phase purity, crystal structure, lattice parameters and morphology respectively. It was found that 10 min of microwave annealing is a time and cost effective approach to produce single phase compositions at low temperature. X-ray studies confirmed the single phase formation of pure and the doped analogues which were found to be iso-structural with the parent LiNiPO4 compound. The cell parameters with the addition of copper content were in accord with the Vegards law. Impedance studies pointed toward enhanced electrical properties of doped samples as compared to the undoped one.

Study of the growth process of magnetic nanoparticles obtained via the non-aqueous sol–gel method

The growth process of iron oxide nanoparticles during synthesis via the non-aqueous sol–gel method has been analyzed. Samples obtained after reaching reaction temperature TR = 200 °C and during the following 23 h of synthesis were characterized in detail by X-ray diffraction measurements, transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Mossbauer spectroscopy, and magnetization measurements. The results show that the iron oxide nanocrystals are majorly composed of maghemite and grow in a faceted shape. The particle size increases gradually during the synthesis, and the structural and magnetic properties improve primarily during the first 6 h of reaction.

Hydrodechlorination of Carbon Tetrachloride and 1,2-Dichloroethane on Palladium Nanoparticles Supported on Metal Fluorides

Catalytic activity of palladium supported on strongly acidic aluminum fluoride or on much less acidic magnesium fluoride has been the subject of current research. Both catalysts were synthesized by non-aqueous sol-gel method with subsequent two-stage activation: post-fluorination and reduction. The catalytic behavior of prepared Pd/HS-AlF3 and Pd/HS-MgF2 in the hydrodechlorination reactions of chlorinated hydrocarbons was investigated. It was found that differences in support acidity and catalyst’s activation protocol strongly effect the catalytic performance.