Two-step Sol Gel Research Articles

Designing of Fe3O4 @rGO nanocomposite prepared by two-step sol–gel method as negative electrode for lithium-ion batteries

Designing of Fe3O4 @rGO nanocomposite prepared by two-step sol–gel method as negative electrode for lithium-ion batteries

Innovative Photocatalytic Reactor for Sustainable Industrial Water Decontamination: Utilizing 3D-Printed Components and Silica-Titania Trilayer Coatings

Industrial activities generate enormous quantities of polluted effluents, necessitating advanced methods of wastewater treatment to prevent potential environmental threats. Thus, the design of a novel photocatalytic reactor for industrial water decontamination, purification, and reuse is proposed as an efficient advanced oxidation technology. In this work, the development of the active reactor components is described, utilizing a two-step sol–gel technique to prepare a silica-titania trilayer coating on 3D-printed polymeric filters. The initial dip-coated SiO2 insulator further protects and enhances the stability of the polymer matrix, and the subsequent TiO2 layers endow the composite architecture with photocatalytic functionality. The structural and morphological characteristics of the modified photocatalytic filters are extensively investigated, and their performance is assessed by studying the photocatalytic degradation of the Triton X-100, a common and standard chemical surfactant, presented in the contaminated wastewater of the steel metal industry. The promising outcomes of the innovative versatile reactor pave the way for developing scalable, cost-effective reactors for efficient water treatment technologies.

Micron-Sized Thiol-Functional Polysilsesquioxane Microspheres with Open and Interconnected Macropores: Effects of the System Composition on the Porous Structure and Particle Size of the Microspheres.

Control of the porous structure and particle size is essential for improving the properties of polysilsesquioxane (PSQ) microspheres. Herein, using the strategy combining inverse suspension polymerization, two-step sol-gel- and polymerization-induced phase separation processes, micron-sized thiol-containing macroporous PSQ (TMPSQ) microspheres with controllable morphologies, adjustable particle diameters (4.9-17.3 μm), and pore sizes (40-3774 nm) were prepared. The morphology and size of the TMPSQ microspheres were characterized by SEM. The mercury intrusion method was employed to analyze the porous structure of the microspheres. The effects of the composition of the sol-gel disperse phase, the mass ratio of the sol-gel disperse phase to the oil continuous phase (WRW/O), and the Span 80 mass content in the oil continuous phase on the morphology, particle diameter and pore size of the TMPSQ microspheres were investigated. Results indicated that the composition of the sol-gel disperse phase determines the morphology and porous structure of the microspheres, and WRW/O and Span 80 content have remarkable impacts on the morphology and particle size of the microspheres. This study is beneficial to the design and fabrication of functional PSQ microspheres with desired properties and promising application prospects.

Magnetic Aerogels for Room-Temperature Catalytic Production of Bis(indolyl)methane Derivatives.

The potential of aerogels as catalysts for the synthesis of a relevant class of bis-heterocyclic compounds such as bis(indolyl)methanes was investigated. In particular, the studied catalyst was a nanocomposite aerogel based on nanocrystalline nickel ferrite (NiFe2O4) dispersed on amorphous porous silica aerogel obtained by two-step sol-gel synthesis followed by gel drying under supercritical conditions and calcination treatments. It was found that the NiFe2O4/SiO2 aerogel is an active catalyst for the selected reaction, enabling high conversions at room temperature, and it proved to be active for three repeated runs. The catalytic activity can be ascribed to both the textural and acidic features of the silica matrix and of the nanocrystalline ferrite. In addition, ferrite nanocrystals provide functionality for magnetic recovery of the catalyst from the crude mixture, enabling time-effective separation from the reaction environment. Evidence of the retention of species involved in the reaction into the catalyst is also pointed out, likely due to the porosity of the aerogel together with the affinity of some species towards the silica matrix. Our work contributes to the study of aerogels as catalysts for organic reactions by demonstrating their potential as well as limitations for the room-temperature synthesis of bis(indolyl)methanes.

Theoretical and experimental investigations of vanadium pentoxide–based electrocatalysts for the hydrogen evolution reaction in alkaline media

A key approach towards better realization of intermittent renewable energy resources, namely, solar and wind, is green electrochemical hydrogen production from water electrolysis. In recent years, there have been increasing efforts aimed at developing noble metal-free electrocatalysts that are earth-abundant and electroactive towards hydrogen evolution reaction (HER) in alkaline electrolytes, wherein an initial water dissociation step is followed by a two-electron transfer cathodic reaction. Although relatively earth-abundant, vanadium-based electrocatalysts have been sparsely reported due to subpar electroactivity and kinetics towards water electrolysis in general and alkaline electrolysis in specific. Herein, we investigate the fine-tuning of orthorhombic V2O5-based electrocatalysts as candidates for HER through a scalable two-step sol–gel calcination procedure. Briefly, surface-induced anionic oxygen deficiencies and cationic dopants are synergistically studied experimentally and theoretically. To that end, first-principle facet-dependent density function theory (DFT) calculations were conducted and revealed that the coupling of certain dopants on V2O5 and co-induction of oxygen vacancies can enhance the catalytic HER performance by the creation of new electronic states near the Fermi level (EF), enhancing conductivity, and modulating surface binding of adsorbed protons, respectively. This was reflected experimentally through kinetically non-ideal alkaline electrochemical HER using Zn0.4V1.6O5 whereby − 194 mV of overpotential was required to attain − 10 mA/cm2 of current density, as opposed to pristine V2O5 which required 32% higher overpotential requirement at the same conditions. The disclosed work can be extended to other intrinsically sluggish transition metal (TM)–based oxides via the presented systematic tuning of surface and bulk microenvironment modulation.Graphical

Facile Synthesis and Electrochemical Analysis of Zn-Doped V2O5 Anode Materials for High-Rate Li Storage

The surging demand for Li rechargeable batteries with high energy densities and rapid rate capability has propelled research on materials that can replace the conventional anode materials like graphite. Vanadium pentoxides (V2O5) have emerged as promising anode candidates owing to their excellent rate capability. Specifically, V2O5 allows the electrochemical prelithiation process, in which three Li-ions can be inserted to form Li3V2O5, followed by reversible insertion and extraction of two Li-ions. Nevertheless, the unsatisfactory Li-ion diffusion coefficients and electrical conductivities of these materials remain major drawbacks. Here, we propose a Zn-doped V2O5 anode, fabricated using a two-step sol–gel method, for high-rate Li-ion batteries. Zn was incorporated into V2O5 to enhance the Li-ion transport kinetics through the electrode. The crystal structure (orthorhombic) of Zn-doped V2O5 was identified by X-ray diffraction analysis, and the Zn doping was confirmed by X-ray photoelectron microscopy. The effect of Zn doping was thoroughly examined using various analytical methods, such as cyclic voltammetry and galvanostatic intermittent titration technique. The Zn-doped V2O5 electrode exhibited remarkable cycling durability, enduring for 1000 cycles, while retaining an enhanced capacity, even under a high rate of 2C.

Micron-Sized Thiol-Functional Polysilsesquioxane Microspheres with Open and Interconnected Macropores: Preparation, Characterization and Formation Mechanism.

Polysilsesquioxane (PSQ) microspheres have shown promise in many fields, but previous studies about porous PSQ microspheres are scarce. Herein, we fabricated novel micron-sized thiol-functional polysilsesquioxane (TMPSQ) microspheres with open and interconnected macropores by combining inverse suspension polymerization with two-step sol-gel and polymerization-induced phase separation processes, without using phase-separation-promoting additives or sacrificial templates. The chemical composition of the TMPSQ microspheres was confirmed using FTIR and Raman spectroscopy. The morphology of the TMPSQ microspheres was characterized using SEM and TEM. TGA was employed to test the thermal stability of the TMPSQ microspheres. Mercury intrusion porosimetry and nitrogen adsorption-desorption tests were performed to investigate the pore structure of the TMPSQ microspheres. The results showed that the TMPSQ microspheres had open and interconnected macropores with a pore size of 839 nm, and the total porosity and intraparticle porosity reached 70.54% and 43.21%, respectively. The mechanism of porous generation was proposed based on the morphological evolution observed using optical microscopy. The macropores were formed through the following four steps: phase separation (spinodal decomposition), coarsening, gelation, and evaporation of the solvent. The macropores can facilitate the rapid mass transfer between the outer and inner spaces of the TMPSQ microspheres. The TMPSQ microspheres are promising in various fields, such as catalyst supports and adsorbents.

Luminescence of Binary-Doped Silica Aerogel Powders: A Two-Step Sol-Gel Approach.

In this study, we report a novel synthesis of hydrophobic silica aerogel powder composites, functionalized and binary-doped with [Tb(phen)2](NO3)3 and [Eu(phen)2](NO3)3 nanocrystals, employing a two-step sol-gel methodology. The investigation delves into the structural elucidation, optical properties and thermal conductivity of these functionalized Tb(III)-Eu(III) composites. Our analysis includes diffuse reflectance spectra and excitation and luminescence spectra, highlighting the quantum yields of composites with varying chemical compositions. Remarkably, these samples exhibit a strong luminescence, with distinct hues of red or green based on the specific doping type and level. The detailed examination of excitation spectra and quantum yields establishes robust energy-transfer mechanisms from the 1,10-phenanthroline molecule to the lanthanide ions. Notably, our study uncovers a Tb3⁺→Eu3⁺ energy-transfer phenomenon within the binary functionalized samples, providing compelling evidence for a structural formation process occurring within the mesoporous framework of the aerogel powders.

Preparation of SiO2/Fe2O3 composite aerogels for thermal insulation enhancement

Silica aerogel, with a unique nano-network structure, serves as a high-performance thermal insulation material. However, silica aerogel possesses a high infrared wave transmission ratio above 300 °C, whose thermal conductivity increases and thermal insulation performance further decreases with the increasing temperature. Introducing opacifiers to silica aerogel is a crucial strategy for addressing this issue. In this work, the ferric oxide exerted as an opacifier was incorporated into the main-phase silica aerogel to improve its thermal insulation at high temperatures. The SiO2/Fe2O3 composite aerogels were created via the two-step sol-gel process followed by supercritical drying, which involved doping ferric nitrate nonahydrate as a Fe2O3 precursor into the silica sol generated with tetraethoxysilane. In this way, SiO2/Fe2O3 composite aerogels with low density (0.04 g/cm3), high specific surface area (705 cm2/g), and low thermal conductivity (0.026 W/(m K)) were obtained by structural adjustment. The incorporation of Fe2O3 improves the thermal insulating properties of silica aerogels. After heat treatment at 1100 °C, the thermal conductivity of the SiO2/Fe2O3 composite aerogel was 0.167 W/(m K), lower than that of the pure silica aerogel (0.249 W/(m K)). Furthermore, the SiO2/Fe2O3 composite aerogel maintained its amorphous structure and exhibited a specific surface area of approximately 94.56 cm2/g, which was three times that of the pure silica aerogel. When subjected to 5-min heating at 1000 °C, the maximum surface temperature of the heat delivery surface of the SiO2/Fe2O3 composite aerogel reached 280.8 °C, whereas the pure silica aerogel reached 353.8 °C.

Synthesis and Characterization of Erbium-Doped Silica Films Obtained by an Acid-Base-Catalyzed Sol-Gel Process.

Erbium-doped silica films were synthesized using a two-step sol-gel methodology that involved acid and base catalysts, with erbium concentration ranging from 0.2% to 6% and annealing temperatures varying from 500 °C to 900 °C. The photoluminescence spectra showed that the samples exhibiting efficient emission were annealed at 800 °C and 900 °C and doped with 3% and 6% erbium. The X-ray diffraction analysis revealed that the internal structure of the films was influenced by the different annealing temperatures and the doping concentrations. Samples with dominant 4f transitions were modelled. The results suggest that the proposed method is a promising approach for the synthesis of erbium-doped silica films with potential applications in optical devices.

Determining the influence mechanism of defects on remarkable room temperature ferromagnetic behavior for C-doped titanium dioxide aided by carboxymethyl cellulose as C source

C-doped titanium dioxide nanoparticles (C–TiO2) were synthesized through a two-step sol-gel process aided by carboxymethyl cellulose (CMC) as C source, following by annealed at different temperature under vacuum. Lattice defects and room temperature ferromagnetism (RTFM) influenced by C doping and annealing temperature are investigated in detail. Correlation between the variation tendency of defects and that of saturation magnetization (Ms) of C–TiO2 is determined, and influence mechanism of defects on RTFM is clarified. Results reveal that influenced by the increase of annealing temperature, C–TiO2 transforms from anatase to rutile phase, followed by some brookite phase and a small amount of elemental carbon precipitate. Three types of defects are introduced in C–TiO2 lattice, namely, substitutional C atoms at titanium sites (CTi), interstitial C defects (Ci) and oxygen vacancies (VOs). Content of CTi shows a gradual increase with increase in annealing temperature from 200 °C to 500 °C, after which a decrement is observed, and that of Ci shows an opposite tendency, while VOs content increases monotonically with increased annealing temperature. Influenced by annealing temperature, Ms shows a similar variation tendency to that of CTi. Joint effect of CTi and VOs promotes the formation of RTFM in C–TiO2, and CTi defects play a major role by inducing ferromagnetic coupling interaction between C 2p and O 2p states. CMC is a more suitable C source than citric acid to induce remarkable room temperature ferromagnetic behavior in C–TiO2 nanoparticles.

Adsorption properties of silica aerogel-based materials.

Silica aerogels have piqued the interest of both scientists and industry in recent decades due to their unusual properties such as low density, high porosity, low thermal and acoustic conductivity, high optical transparency, and strong sorption activity. Aerogels may be created via two-step sol-gel synthesis from different organosilicon compounds known as precursors. Various drying processes are employed to remove the solvent from the gel pores, the most common of which is the supracritical drying method. This paper highlights the potential of silica aerogels and their modifications as adsorbents for environmental cleanup based on recent researches. Following an introduction of the characteristics of aerogels, production techniques, and different categorization possibilities, the study is organized around their potential use as adsorbents.

Degradation of pollutants in solid and gas states using waterborne acrylic nanocomposite paints

In this study, TiO2/SiO2 nanoparticles were synthesized using titanium tetraisopropoxide and tetraethoxysilane in a two-step sol-gel route. FTIR, XRD, UV–Vis, and XPS techniques were used to characterize the synthesized nanoparticles. Fe-SEM was utilized to evaluate the particle size of the synthesized nanoparticles (30.35 ± 4.52 nm). Photo-degradation of rhodamine B (Rh.B) as a solid pollutant model and NO2 as a typical gaseous pollutant was assessed on the surface of the waterborne-acrylic coatings containing TiO2/SiO2 nanoparticles (TSC.La) under direct sunlight irradiation and accelerated weathering conditions and the results were compared with a P25–TiO2 nanoparticle (UT.La) embedded coating samples.To evaluate the degradation of Rh.B, color coordinates (L*a*b*) were measured, while the degradation of NO2 was determined in a batch-designed photocatalytic reactor by measuring the reduction in gas concentration. For the TSC.La-sample exposed to accelerated weathering conditions, the changes in a* parameter (Δa*) were about 60%, which was 44 times greater than the changes in this parameter for the sample exposed to sunlight. The surface morphology of the exposed samples to the accelerated weathering conditions was evaluated using AFM and BET measurements. The AFM results indicated that TiO2/SiO2 nanoparticles lead to less surface degradation of the paints compared to the commercial TiO2 nanoparticles. NO2 concentration decreased steadily in the reactor from 30 to 27 ppm, at an RH%<20 in the presence of UT.La or TSC.La-samples after 45 and 60 min of UV exposure. This reduction in gas concentration is equivalent to photocatalytic power of 6 and 8 mLm−2h−1, for the two samples, respectively.

Controllable preparation of thio-functionalized composite polysilsesquioxane microspheres in a microreaction system

Controllable preparation of monodispersed composite polysilsesquioxane microspheres (CPSQs) with scalability is required but difficult to realize in a conventional stirred batch reactor because of the reactors’ poor mixing performance and scaling-up effects. A new semi-continuous microreaction system integrating a microreactor with a stirred batch reactor was developed for the synthesis of monodispersed thio-functionalized CPSQs by employing a two-step sol–gel method. Methyltrimethoxysilane and (3-mercaptopropyl)trimethoxysilane were used as silicon sources. The effects of the synthesis variables were systematically studied. The particle size could be adjusted between several hundreds of nanometers and several micrometers with a narrow size distribution (the coefficient of variation was <10%), and the sulfhydryl group (SH) concentration reached 14.13 at.%. Compared with the batch reactor, the semi-continuous microreaction system showed higher synthesis reproducibility and higher potential for the large-scale production of CPSQs.

Non-fluorinated sol-gel processing of hydrophobic coating on cotton fabric

In this study, the importance of wash durability tests for providing efficient hydrophobic surfaces through non-fluorinated sol-gel processes has been investigated. Various concentrations of methyltriethoxysilane (MTEOS) and trimethylchlorosilane (TMCS) have been used to deposit SiO2 nanoparticles on a cotton fabric in a two-step sol-gel process. The effects of catalyst type on the hydrophobic properties of fabric are investigated by using ammonia or hydrochloric acid in the sol-gel procedure. Surface characteristics, such as morphology and wettability are evaluated by image processing techniques and contact angle measurements. Air permeability, mechanical strength and wash durability tests are also performed to investigate the physical/mechanical properties of the samples. The results show that SiO2 nanoparticles are well dispersed on cotton fabrics with a contact angle of 149o. It is revealed that the fabric coated with 1 mL of MTEOS and ammonia catalyst exhibits the highest breathability and strength. Moreover, the first stage of the sol-gel technique is sufficient to provide super hydrophobicity. However, the results of the durability test indicate that sol-gel technique does not provide suitable wash durability that should be considered in future investigations.

Microstructural properties and heat transfer characteristics of in-situ modified silica aerogels prepared with different organosilanes

• In-situ modified silica aerogels were synthesized in ambient pressure by a facile sol-gel method. • Various organosilanes MTMS, MTES, VTMS, MEMO and GLYMO were utilized as silica precursors. • Heat transfer mechanisms were investigated both theoretically and experimentally. • SA-MTMS had the lowest density (92 kg⁄m 3 ) and high thermal stability (up to 700 °C). • All samples exhibited similar insulation performances (λ in between 42 and 47 mW/mK). • The density was the most decisive parameter for different heat transfer modes in aerogels. • Coupling thermal conductivity term is the key contributor to the total thermal conductivity. Conducting an in-situ modification during the sol-gel reactions, without any post gelation-modification, offers a cost-effective and time-saving strategy in the production of silica aerogels. Therefore, in this study, in-situ modified silica aerogels were synthesized as potential thermal insulation materials via a two-step sol-gel process under ambient pressure. Different organosilanes having methyl (SA-MTMS), ethyl (SA-MTES), vinyl (SA-VTMS), epoxide (SA-GLYMO), and methacrylate functional (SA-MEMO) groups were used as silica sources. According to the selected precursor, the change in the heat transfer properties were investigated both by thermal conductivity measurements and by theoretical models. SA-MTMS possessed the lowest density (92 kg / m 3 ) and high thermal stability (up to 700 °C). Despite the existence of bulk organic groups in its structure, the SA-GLYMO had the highest specific surface area (531 m 2 / g ) . Regardless of their morphology, all samples have exhibited similar insulation performances (λ=42–47 mW/mK). However, the prominent heat transfer mechanisms were directly affected by the bulk density and the underlying microstructure. For low-density samples, gas-contributed thermal conductivities were the key contributor to the total thermal conductivity whereas solid thermal conduction was the dominant mechanism in high-density samples. The coupling thermal conductivity term was also crucial as the total conductivity would have been significantly underestimated without it.

Evaluation of the antibacterial properties and in-vitro cell compatibilities of doped copper oxide/hydroxyapatite composites

Mg, Zn and Ce-doped CuO/HA composites were prepared by a two-step sol-gel and hydrothermal process. SEM images showed a spherical appearance of HA and a needle-like morphology for doped CuO. XRD patterns revealed that all doped CuO/HA composites exhibited a hexagonal crystal structure of HA and a monoclinic crystal structure of CuO with no impurities. ICP analysis indicated that with the increase of loading amount of doped CuO, the concentrations of Cu2+ ions and doping ions released from composites increased. Moreover, CuO/HA composites exhibit improved antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as compared with HA. When the loading amount of doped CuO in composites increased to 15 wt%, the composites exhibited the best antibacterial activity and complete bacterial growth inhibition effect. Furthermore, the CCK-8 assay revealed that the doped CuO/HA composites are noncytotoxic and can promote the proliferation of osteosarcoma cells. This work highlights the potential of the doped CuO/HA composites with significant antibacterial activity, bioactivity and cell compatibility for potential biomedical applications in dental implants and bone regeneration.

Performance regulation of silica aerogel powder synthesized by a two-step Sol-gel process with a fast ambient pressure drying route

This paper proposed a timesaving route for preparing silica aerogel powder with TEOS as a precursor. Thermal insulating super hydrophobic silica aerogel powder was synthesized by combining two-step Sol-gel reaction with a fast ambient pressure drying process. Silica Sol-gel was formed after catalytic reaction by oxalic acid and NH4OH, and then turned to be hydrophobic aerogel through further surface modification (only three hours with no solvent exchange process) and drying process. By optimizing every tiny trace of synthetic component, the obtained silica aerogel powder exhibits excellent properties, such as low apparent density (0.212 g/cm3) and thermal conductivity (0.053 W/mK), as well as high BET surface area (769.86 m2/g) and water contact angle (149.0 °). This work presents a timesaving method for synthesizing thermal insulating hydrophobic silica aerogel powder.

Durable superhydrophilic and antireflective coating for high-performance anti-dust photovoltaic systems

Antireflection coatings have received extensive attention due to their unique ability to reduce the reflection losses of incident light in photovoltaic (PV) systems. In this study, we report a hybrid silica sol coating fabricated via a simple and cost-effective base/acid-catalyzed two-step sol–gel method. The prepared coating exhibits these main properties: high transmittance, superhydrophilic, and anti-dust effect. Experimental conditions to achieve high transmittance were systematically optimized, such as aging time of the base-catalyzed silica sol and dip-coating speed. A transmittance improvement of about 6.35% compared to the bare glass substrate was then obtained. The morphology and film structure were also characterized. The coatings have a closed and dense structure which, combined with their superhydrophilicity, endowed them with excellent anti-dust performance, as well as high mechanical properties, with a pencil hardness of 4H. Furthermore, the coating showed great resistance to high temperature and high humidity as well as high stability to long-time outdoor exposure. The results suggest the good reliability of the prepared coatings for PV solar glass application.

Core–Shell Structured NaYF4:Yb,Er Nanoparticles with Excellent Upconversion Luminescent for Targeted Drug Delivery

A core–shell-structured composite by combining mesoporous silica with upconversion luminescence (UCL) property had considerable application potentials in the fields of drug delivery, disease diagnosis, and therapy. In this paper, a monodisperse, core–shell-structured NaYF4:Yb,Er@nSiO2@mSiO2 nanoparticle (UCNP@MSNs-FA) with excellent UCL property was successfully fabricated by a facile two-step sol–gel strategy and by modifying the surface with folic acid (FA) to strengthen its tumor-targeting performance. The properties of the composite were studied extensively, which indicated that UCNP@MSNs-FA possessed good dispersion, typical core–shell-structured with high specific surface area (132.775 m2/g), and excellent UCL property that improve cell imaging and drug delivery. The viability of L929 cells and hemolysis assay demonstrated the good biocompatibility of the composite. By using doxorubicin hydrochloride (DOX) as a model drug, the drug loading content and encapsulation efficiency of UCNP@MSNs-FA could reach as high as 11.2% and 37.3%, respectively, which proved the effectiveness to load anticancer drugs. In addition, the DOX-UCNP@MSNs-FA system exhibited sustained drug release and strong pH-dependent performance, in which the drug release would be accelerated at the slightly acidic microenvironment in the tumor. Moreover, experimental results indicated that DOX-UCNP@MSNs-FA exhibited specific cytotoxicity to KB cells but weakened toxicity to FR-negative cells. Therefore, the as-prepared UCNP@MSNs-FA could be used potential for simultaneous targeted anti-cancer drug delivery and cell imaging and enhance the therapeutic efficacy against FR-positive tumor cells.