One-step Sol-gel Process Research Articles

Preparation and analytical application of novel thiol-functionalized solid extraction matrices: From mesoporous silica to hybrid monolithic capillary column

A comprehensively comparative study of thiol-functionalized mesoporous silica and organic-inorganic hybrid monolithic column was reported, aiming at the separation and enrichment of inorganic arsenic. Thiol-functionalized mesoporous silica was synthesized based on the one-step co-condensation method. At the same time, a novel thiol-functionalized organic-inorganic hybrid monolithic column was synthesized using an unconventional ternary weak basic solvent system via one-step sol-gel process. The approach to prepare monolithic column through mild condition remarkably improved delamination phenomenon of thiol-functionalized hybrid monolithic column easily caused by conventional methods. As(III) can be selectively uptaken by the hybrid monolithic column and homemade syringe-based solid phase extraction device containing mesoporous silica through chelation in a wide range of pH, while As(V) cannot, and then the captured As(III) was eluted by 3% HNO3 (v/v) with 0.01 mol L−1 KIO3. Under the optimized conditions, the extraction recoveries were 91–102% and 93–103% for mesoporous silica and monolithic column, respectively. Although both two materials were ideal solid matrices for the removal and speciation analysis of As(III) in environmental waters, the monolith-based solid phase microextration protocol was more fast and reagent-saving than the other, which endued monolithic columns with more application prospects for trace elemental analysis and speciation. Even so, the exploration of mesoporous silica could efficiently pilot the synthesis of monolithic columns.

Fabrication of superhydrophobic cotton fabric with fluorinated TiO2 sol by a green and one-step sol-gel process

The purpose of this paper is to propose a facile, green and low-cost approach of the preparation of superhydrophobic cotton textiles, which can be fabricated with fluorinated TiO2 sols via a sol-gel method. The coating was prepared with TiO2 sols catalyzed with acetic acid, then modified by poly(Hexafluorobutyl methacrylate) (PHFBMA) which was synthesized by free radical polymerization. The wettability, surface morphology and chemical composition of pristine and modified cotton fabrics were investigated. The modified fabric presents a high contact angle reached up to 152.5°. The successful incorporation of fluorinated TiO2 nanoparticles into cotton fabric was verified by the above measurements results. Additionally, the chemical stability of the coated fabric has been tested by immersing in different pH solutions and organic solvents, demonstrating the outstanding water repellency of the fabric. Furthermore, the treated cotton fabric shows excellent self-cleaning properties, which makes it an ideal material for large-scaled industrial applications in various conditions.

Enhanced catalytic efficiency of FeMnTiOx SCR catalysts through adding tourmaline nanopowders during the one-step sol-gel process

In this work, the FeMnTiOx catalysts were modified firstly by tourmaline nanopowders via one-step sol-gel method, aiming at improving the catalytic efficiency. The effects of tourmaline nanopowders on the growth, micro morphology and surface elements valence distribution of the catalysts were systematically analyzed, which showed the tourmaline nanopowders had obvious influence on the growth mechanism of FeMnTiOx. The nano size solid solution catalyst was formed and loaded a 28.52 nm thickness shell on the surface of tourmaline nanopowders, and the contents of surface chemical oxygen, Mn3+ and Mn4+ were enhanced obviously due to the unique structure formed by tourmaline nanopowders. Accordingly, both the operation temperature window and catalytic efficiency of the modified FeMnTiOx catalysts as prepared were improved significantly, which was demonstrated to be an economical and efficient method in the field of low temperature SCR technology.

UV-Induced Photocatalytic Cashmere Fibers.

Cashmere with UV-induced photocatalytic properties is developed for the first time by applying nanocrystalline anatase TiO2 colloid that is free of inorganic acids and organic solvents via a facile low-temperature one-step sol-gel process. The coated cashmere exhibits remarkable UV-induced photodegradation of methyl orange. Furthermore, the photocatalytic nano-coating on cashmere exhibits significant stability after repetitive washing cycles without the need for chemical or physical pretreatment, where the photocatalytic activities remain almost unchanged after three washing cycles while maintaining a water contact angle above 150°. The one-step functionalization process also minimizes the impact on the peculiar intrinsic properties of cashmere. These findings indicate that cashmere combining reproducible UV-induced photocatalytic activity with stable superhydrophobicity has potential in practical applications.

One-step synthesis of monolithic micro-nano yttria stabilized ZrO2-Al2O3 composite aerogel

Monolithic micro-nano yttria-stabilized ZrO2 (YSZ)-Al2O3 composite aerogel composed of Al2O3 hollow microspheres which was filled with YSZ nanoparticles was prepared by one-step sol-gel process. Such aerogel-like microstructure combined the advantages of good high temperature tolerant property of Al2O3 hollow microspheres and favorable thermal insulation property of porous YSZ aerogel, while the mechanical strength of the structure also significantly increased. The micro size voids in the Al2O3 hollow microspheres were filled by YSZ aerogels thus resulted in more mesopores which contributed to block heat transfer up to 1200 °C. By optimizing the ratio of YSZ in the composite, the obtained composite aerogel showed good thermal stability (linear shrinkage = 9.7%), low room temperature thermal conductivity (0.032 W/mK) and high elastic moduli (3.47 MPa) after 1200 °C heat treatment.

Aptamer entrapment in microfluidic channel using one-step sol-gel process, in view of the integration of a new selective extraction phase for lab-on-a-chip.

There is a great demand for integrating sample treatment into μTASs. In this context, we developed a new sol-gel phase for extraction of trace compounds in complex matrices. For this purpose, the incorporation of aptamers in silica-based gel within PDMS/glass microfluidic channels was performed for the first time by a one-step sol-gel process. The effective gel attachment onto microchannel walls and aptamer incorporation in the polymerized gel were evaluated using fluorescence microscopy. A good gel stability and aptamer incorporation inside the microchannel was demonstrated upon rinsing and over storage time. The ability of gel-encapsulated aptamers to interact with its specific target (either sulforhodamine B as model fluorescent target, or diclofenac, a pain killer drug) was assessed too. The binding capacity of entrapped aptamers was quantified (in the micromolar range) and the selectivity of the interaction was evidenced. Preservation of aptamers binding affinity to target molecules was therefore demonstrated. Dissociation constant of the aptamer-target complex and interaction selectivity were evaluated similar to those in bulk solution. This opens the way to new selective on-chip SPE techniques for sample pretreatment.

Assembly of methylated hollow silica nanospheres toward humidity-resistant antireflective porous films with ultralow refractive indices

Humidity-resistant antireflective (AR) porous films with ultralow refractive indices were prepared via an one-step sol–gel process by assembly of methylated hollow silica nanospheres (HSNs). The hydrophobicity and refractive indices of silica-based AR porous films could be varied between 66.0° and 115.0°, and between 1.08 and 1.14, respectively, by tuning the MTES/TEOS molar ratios. A possible assembly mechanism was proposed according to the microstructure of methylated HSNs and porous films. The various properties of silica-based AR porous films were investigated and the AR porous film could demonstrate a good AR capability of 97.6% and excellent humidity resistance.

Sol-gel synthesis of Cu2ZnSnS4 thin films under mild conditions

To produce the absorber layer material for thin-film solar cells, copper–zinc–tin sulfide Cu2ZnSnS4 (CZTS) thin films were prepared from a sol-gel four-component solution in a simple, inexpensive, and environmentally friendly manner by directly applying it onto a glass substrate in multiple spin-coated layers. Afterwards, the resulting films were thermally processed in a drying oven under circulating air atmosphere without sulfur vapor. The obtained X-ray diffraction peaks exactly matched the CZTS (JCPDS 26−0575) diffraction pattern, indicating that the produced coatings were characterized by the kesterite structure. The calculated optical band gap energy of the obtained films was 1.45 eV, which was in good agreement with the literature values, thus suggesting their possible use as alternative candidate absorber materials. The obtained SEM images showed that the synthesized densely packed CZTS films with large sphere-like particles were compact and uniform. Therefore, we have shown for the first time in this study that nearly pure CZTS thin films can be obtained from solution through a one-step sol-gel process, which corresponds to non-toxic sulfurization at a relatively low heating temperature and non-vacuum conditions.

Growth of ZnO nanorod arrays by one-step sol–gel process

ZnO nanorods are usually formed by two-step method. In the first step, a seed layer is coated on substrate and then the second treatment by hydrothermal method is employed for formation of nanorods. Here, we report that ZnO nanorods can be directly coated on glass substrates by sol–gel dip coating technique without the second treatment. The effect of coating layers on morphological, structural, electrical, and optical properties was studied. According to the cross-sectional SEM images of the produced ZnO nanorods, a seed layer was spontaneously observed. The diameter of the ZnO nanorods was varied between 200 nm and 1 µm with coating thickness. The effect of the zinc nitrate tetrahydrate and zinc chloride precursors on the preparation of the ZnO nanorods was also investigated. And, it was found that the zinc chloride precursor exhibited formation of nanorods on the glass substrates. According to the Hall effect measurements, the ZnO nanorods exhibited mobility as high as 95 cm2 (Vs)−1. The X-ray diffraction and electrical studies indicated that highly pure crystalline ZnO nanorods could be obtained by the one-step solution method.

Carbon aerogels through organo-inorganic co-assembly and their application in water desalination by capacitive deionization

We report the preparation of a carbon aerogel (CA) material utilizing the simultaneous co-assembly of organic and inorganic precursors, having a high Brunauer–Emmet–Teller surface area of 2600 m2/g, through a one-step sol–gel process. This CA was characterized using different spectroscopic and microscopic techniques. The as-synthesized CA with its tunable porosity, high mechanical strength, transport property and electrical conductivity was found to be a suitable candidate for water desalination via capacitive deionization (CDI). The optimum working potential for CDI was in the range of 1.2–1.4 V. The material was tested for the removal of different ions of varying charges and the experiment was performed for multiple cycles. The result showed high adsorption capacity of 10.54 mg/g for Cl− in laboratory batch experiments compared to 3–4 mg/g reported for most of the CDI materials. The materials were also characterized after adsorption/desorption cycles. Adsorption was physical in nature and the ions desorbed completely after reversing the polarity. The result showed that the material can be used for multiple cycles without any change in its spectroscopic and adsorption properties.

Screen-printed electrodes made of a bismuth nanoparticle porous carbon nanocomposite applied to the determination of heavy metal ions

This work reports on the simplified fabrication and on the characterization of bismuth-based screen-printed electrodes (SPEs) for use in heavy metal detection. A nanocomposite consisting of bismuth nanoparticles and amorphous carbon was synthesized by a combined one-step sol-gel and pyrolysis process and milled down to a specific particle size distribution as required for the preparation of an ink formulation to be used in screen printing. The resulting electrochemical devices were applied to the detection of Pb(II) and Cd(II) ions in water samples. The porous structure of carbon and the high surface area of the bismuth nanoparticles allow for the detection of Pb(II) and Cd(II) at concentration levels below 4 ppb. The application of the SPEs was demonstrated by quantifying these ions in tap drinking water and wastewater collected from an influent of an urban wastewater treatment plant.

Preparation of hollow submicrospheres with ordered porous SiO2 shell and multiple AuPt nanoalloy cores and their high catalytic activity

Noble metal nanocrystals (Au, Pt or AuPt) with controlled compositions and nanostructures were embedded into hollow silica submicrospheres with highly ordered radial mesopores through a one-step sol–gel process. 2,4-Dihydroxybenzoic acid–formaldehyde (RF-COOH) resin submicrospheres were utilized simultaneously as a hard template to create hollow interiors inside the silica submicrospheres and as carriers to transport pregrown metal nanocrystals, including Au nanoparticle (NP), Pt NP, and AuPt nanoalloy, into the submicrospheres. Calcination removes the resin submicrospheres and causes metal nanocrystals embedded into the RF-COOH submicrospheres break into multiple smaller nanoparticles (2–6nm) that are randomly dispersed in the hollow space of SiO2 submicrospheres M@SiO2 (M=Au, Pt or AuPt). The AuPt@SiO2 submicrospheres showed good catalytic performance for epoxidation of styrene with the conversion and selectivity of 74% and 85%, respectively. The approach reported in this study could potentially be used to simplify the fabrication process of noble metal nanoalloys, which usually entails multiple steps and a previously synthesized hard metal template, and thus guide the design and creation of high-performance catalysts.

The influence of the hydrophobic agent, catalyst, solvent and water content on the wetting properties of the silica films prepared by one-step sol–gel method

In this paper, we used one-step sol–gel process to prepare the hydrophobic silica films on the glass substrate from the ethyltriethoxysilane (ETES) as a precursor and iso-octyltrimethoxysilane (Iso-OTMS) as a hydrophobic agent. In order to study the effect of the hydrophobic agent on the water repellent properties of the silica films, the alcosol was prepared by keeping constant the molar ratio of ETES:EtOH:H2O at 1:36.2:6.3, with 6M ammonium hydroxide and Iso-OTMS/ETES molar ratio varied from 0.2 to 1.4. Also, we investigated the influence of the other sol–gel reaction parameters, such as catalyst, solvent and water content and their effect on the morphology and hydrophobic properties of the silica films. The results revealed that by altering the molar ratio of NH4OH, EtOH and H2O, different sizes of silica nanoparticles from 41.24 to 86.16nm were obtained. The silica films were characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) images, contact angle measurement (CA) and percentage of optical transmission.

Effect of Mn loading onto MnFeO nanocomposites for the CO2 hydrogenation reaction

This work describes the preparation of mesoporous xMnFe oxide (x=0, 0.05, 0.1, 0.2, 0.3 and 0.5 molar ratios) nanocomposites through a one-step sol–gel process in the presence of a triblock copolymer as a structure-directing agent. The prepared oxides were used as catalysts in the CO2 hydrogenation via Fischer–Tropsch reactions for the production of valuable hydrocarbons. Among the catalysts, the 0.05MnFe catalyst performed best under the selected reaction conditions: a reaction temperature of 340°C, overall pressure of 20bar, reactant mixture of 23% CO2/69% H2/8% N2 and flow rate of 20mLmin−1. This catalyst provided a much higher conversion of CO2 to hydrocarbons (63.2%C2–C5, 3.9% to C6+ and 3.6% to oxygenates) and the lowest levels of CO and methane formation among the xMnFe series. Moreover, 0.05MnFe was the only catalyst with a mesoporous structure, and it had a substantially lower reduction temperature than did the other members of the series. The enhanced catalytic activity of the 0.05MnFe catalyst, which contains only a small amount of Mn, appears to result primarily from its high specific area and relatively easy reduction.

A new aerogel based CO2 adsorbent developed using a simple sol-gel method along with supercritical drying.

A new, highly capable and dynamic aerogel adsorbent for CO2 capture was developed using a one-step sol-gel process along with solvent exchange and supercritical drying. The highest CO2 adsorption capacity in a 1% CO2 flow stream (5.55 mmol g(-1)) is much higher than other aerogel adsorbents obtained using a 10% or even higher CO2 gas mixture.

Effect of synthesis conditions on the structural characteristics and luminescence properties of Y0.9Eu0.1V1−xCrxO4 (0 ≤ x ≤ 0.5) nanopowders

Y0.9Eu0.1V1−xCrxO4 (0 ≤ x ≤ 0.5) nanophosphors were synthesized under acid conditions (pH = 2) by a one-step sol–gel process followed by a thermal treatment at 843 K in oxygen flow. The obtained nanopowders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and by Raman and photoluminescence (PL) spectroscopies in a confocal microscope. The influence of pH on the structural characteristics and luminescence properties of the nanophospors was also assessed. XRD measurements reveal a progressive loss of crystallinity as chromium substitutes for vanadium in the samples. Such replacement induces a progressive broadening of the Raman peaks as the Cr content increases, evidencing a certain structural distortion involving different (VO4)3− groups due to the insertion of Cr5+ ions into the host. TEM images of the obtained nanopowders show changes in the particle shape and size of samples grown a different pH values. The addition of chromium hampers an effective energy transfer from the vanadate groups to the Eu3+ ions. This results in a strong decrease of the PL emission intensity corresponding to the intraionic transitions of this rare earth, irrespective of the synthesis conditions of the nanopowders.

Direct synthesis of anatase TiO2 aerogel resistant to high temperature under supercritical ethanol

TiO2 aerogel (TA) was directly prepared by supercritical ethanol drying of TiO2 gel which was synthesized by a simple one-step sol–gel process. High temperature of the supercritical ethanol drying led to the decomposition of most of the organic groups in the TiO2 gel and formation of anatase TiO2. Thermogravimetric (TG) revealed that the resulting TA was anatase TiO2 with a small amount of organic groups. X-ray diffraction (XRD), scanning electron microscope (SEM) and N2 isothermal adsorption/desorption tests indicated that the crystalline structure (crystalline size and phase) and pore structure of TA were very stable after thermal treatment below 700°C.

High permittivity ofBa(Ti1-xZrx)O3-basedY5V-type nanopowders and ceramics synthesized using a one-step sol–gel method

We synthesized Ba ( Ti1-xZrx) O3-based (BTZ) nanopowders modified with Cu and Nb , and sintered ceramics using a one-step sol–gel process. Characterization using TG-DTG, XRD, SEM, and TEM analysis methods revealed that the powders formed at a nanometer scale. The process was controlled by the composition and calcining temperature. BaZrO3formed earlier than BaTiO3during the calcining, then a Ba ( Ti1-xZrx) O3solid solution formed incompletely, resulting in ceramics with huge permittivity and good temperature stability. Moreover, the maximum dielectric constant (εmax) first increased and then decreased as the Curie temperature (Tc) shifted to a lower temperature. When the Zr concentration was 5.4 mol%, εmaxwas greater than 24,000 and the dielectric loss (25°C) was only 0.005; this meets the Electronic Industries Alliance Y 5 V specifications. These nanopowders would permit a significant reduction in the thickness of multilayer ceramic capacitors and the huge permittivity of the ceramics will help meet the current demand for device miniaturization in the electronics industry.

One-step synthesis of unique silica particles for the fabrication of bionic and stably superhydrophobic coatings on wood surface

The silica particles with unique morphology and hydrophobicity have been synthesized via a drop-coating method. After this one-step sol–gel process, silica particles as well as polystyrene were employed in the bionic and stably superhydrophobic coatings on wood surface (with water contact angle of 153±1° and sliding angle less than 5±0.5°). Scanning electron microscopic (SEM) studies revealed that the composite coatings possess two dimensional hierarchical structures comprising of micron scale papilla and submicron scale granules. The synergistic effect of micron/submicron binary structure and low surface energy layer was responsible for the superhydrophobicity of wood surface. Moreover, the chemical and mechanical stabilities of treated wood have been investigated as well, and the results show that the product possesses superhydrophobic property in a wide extent, such as pure water, corrosive water under both acidic and basic conditions, and some common organic solvents. More importantly, it will offer an opportunity to extend the range of practical applications for wood resources.

Synthesis and characterization of sol–gel mesoporous organosilicas functionalized with amine groups

In this work we report on the synthesis of porous amine functionalized organosilica materials prepared by co-condensation of tetraethyl orthosilicate (TEOS) and bis-[3-(trimethoxyosilyl)propyl] amine (BTPA). The gels were prepared through a one-step sol–gel process catalyzed by the NH groups of BTPA. A block copolymer poly(ethylene glycol)–block-poly(propylene glycol)–block-poly(ethylene glycol) (P123) was employed as a porogen using the surfactant template method. The resultant materials have been characterized by nitrogen gas sorption, powder X-ray diffraction, FT-IR, SEM, 29Si MAS NMR, 13C CP MAS NMR and TG/DTA analysis. In order to examine the potential of these materials as adsorbents for heavy metals, Hg(II) adsorption experiments were also performed. The hybrids showed mesoporous disordered structure as evidenced by N2 adsorption–desorption isotherms and XRD patterns. Adsorption of Hg(II) ions from aqueous solutions showed high capacities suggesting that these materials could be used as adsorbents for Hg(II) ions in acid solutions.