Gel Synthesis Research Articles

Synthesis of gel crosslinked composite material from spent cathode carbon blocks and its application in modified asphalt binders

The utilization of spent cathode carbon blocks (SCCB) from aluminum electrolysis has become challenging due to their content of highly toxic cyanides and environmentally harmful fluorides. To achieve reliable recovery and utilization of hazardous waste, targeted research has been conducted on the treatment of waste cathode carbon blocks and their potential application in asphalt pavement. Hydrogen peroxide (H2O2) is employed to remove cyanides from the waste cathode carbon blocks, meeting the construction requirements for transportation areas. Anhydrous calcium chloride is used as a calcium source to precipitate soluble fluorides in the solution. Finally, the waste cathode carbon blocks are gel-crosslinked using polyvinyl alcohol-polyvinyl pyrrolidone, addressing the release of fluorides beyond environmental tolerance. This results in the synthesis of a composite material consisting of calcium fluoride deposits and gel-encapsulated waste cathode carbon blocks (PSB), which exhibits good thermal stability in the temperature range of 0–217 °C. Through DSR and MSCR testing, it has been demonstrated that the gel-crosslinked waste cathode carbon block composite material improves the asphalt's sensitivity to temperature and enhances its resistance to rutting at high temperatures. The 1% PSB/SBS modified asphalt shows the best performance, compared to SBS, the complex modulus (G*) of the modified asphalt increased by 117.4% at 46 °C, and the recovery indices for creep at 64 °C improved by 39.28% (at 0.1 kPa) and 55.65% (at 3.2 kPa), and thermal gravimetric analysis of the asphalt confirms that the addition of PSB improves the asphalt's thermal stability. Fluorescence microscopy analysis reveals that the inclusion of PSB does not affect the morphological development of SBS swelling and plays a stabilizing and supporting role in the asphalt mixture.

Preparation of hexagonal boron nitride polymer systems with one-step sol–gel synthesis for pH-controlled drug delivery

Preparation of hexagonal boron nitride polymer systems with one-step sol–gel synthesis for pH-controlled drug delivery

Sol–Gel Synthesis of ZnO:Li Thin Films: Impact of Annealing on Structural and Optical Properties

A sol–gel deposition approach was applied for obtaining nanostructured Li-doped ZnO thin films. ZnO:Li films were successfully spin-coated on quartz and silicon substrates. The evolution of their structural, vibrational, and optical properties with annealing temperature (300–600 °C) was studied by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UV-VIS spectroscopic, and field emission scanning electron microscopic (FESEM) characterization techniques. It was found that lithium doping maintains the wurtzite arrangement of ZnO, with increasing crystallite sizes when increasing the annealing temperature. Analysis of the FTIR spectra revealed a broad main absorption band (around 404 cm−1) for Li-doped films, implying the inclusion of Li into the ZnO lattice. The ZnO:Li films were transparent, with slightly decreased transmittance after the use of higher annealing temperatures. The porous network of undoped ZnO films was transformed to a denser, grained, packed structure, induced by lithium doping.

Polymerizable sol–gel synthesis of dark-visible light antibacterial magnetically-recoverable AgBr-loaded iron oxide/alumina nanocomposite

The demand for a facile approach for synthesizing multifunctional nanocomposites is increasingly vital across diverse applications. In this study, a polymerizable sol–gel synthesis has been reported to obtain nanocomposites of magnetic iron oxide deposited over alumina nanopowder. The synthesis is mediated by the deposition of a calculated amount of iron(III) methacrylate, along with ethylene glycol dimethacrylate crosslinker, over alumina nanopowder, followed by thermally-inducing free radical polymerization at 125 °C for 30 min. The powder thus obtained has been subjected to calcination at 400 °C for 150 min and the resultant nanocomposites were characterized using wide-angle x-ray scattering, attenuated total reflectance—Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, field-emission scanning electron microscopy, ultraviolet-diffuse reflectance spectroscopy, vibrating sample magnetometer and Brunauer–Emmett–Teller surface area measurements. The nanocomposites containing 15 and 20 wt% of iron oxide have been found to exhibit a saturation magnetization (M s) value ranging from 12 to 14 emu g−1. To the nanocomposite containing 20 wt% of iron oxide, 5 wt% of AgBr was loaded through thoroughly mixing a surfactant-based precursor, silver-tetraoctyl ammonium bromide (Ag-TOAB), followed by thermolysis. All the nanocomposites have been studied for their antibacterial activity against a representative gram-negative bacterium, Escherichia coli, under dark and visible light conditions. While a 3 mg ml−1 loading of the AgBr-loaded nanocomposite has exhibited complete clearance of the bacterial growth by 90 min in the dark, a similar activity has been observed in 60 min under light. The study has revealed the multifunctionality and high potential of the AgBr-loaded iron oxide/alumina nanocomposite as a promising dual-mode antibacterial and magnetically recoverable photocatalyst material.

Kaolin-based stable colloidal nano-silica: Peptization factors and stability assessments via designed experiments

This study aims to synthesize stable colloidal silica via the peptization method as a green and low-cost route. It is crucial to adopt a proper synthesis procedure and choose an appropriate raw material. To achieve this purpose, kaolin was employed as a silica rich source that occurs abundantly in nature. The process involves synthesis of the wet gel through the succession of calcination, acid leaching, alkaline treatment, sodium silicate precipitation, and then peptization of the wet gel. Effect of the acid type on acid leaching was evaluated. Effective factors affecting the gel purity such ad acid concentration, pH of gelation, and temperature of alkaline treatment, were studied and optimized via a statistical design of the experiments. Subsequently, the influential parameters on stability and particle size of the obtained colloidal silica, including the temperature of the gel formation, pH of sol medium, concentration of silica gel, and type of stabilizing base, were investigated via one-facto-at-a-time. The samples were characterized by X-ray fluorescence analysis (XRF), dynamic laser light scattering analysis (DLS), X-ray Diffraction (XRD), Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET), and Field emission scanning electron microscopy (FESEM) analyses. Results showed that under optimum conditions, ultra-pure silica gel with a silica content of 99.34 % was obtained. The colloidal sample with the highest stability (zeta potential of −75.6 mV), had nanoparticles showing sizes in the range of 21–66 nm.

Preparation of Boron Carbide Biopolymer Systems with One Step Sol–Gel Synthesis for pH-Controlled Drug Delivery

Preparation of Boron Carbide Biopolymer Systems with One Step Sol–Gel Synthesis for pH-Controlled Drug Delivery

Phase transformation and heterojunction nanostructures of bismuth iron oxide

The construction of an efficient bismuth iron oxide shows great potential in excellent crystal structure properties and visible light photocatalysis. However, it is challenging to synthesize nanostructures with the desired morphologies. For the first time, the bismuth iron oxide is fabricated using sol–gel synthesis method, exhibiting the desired crystallite size and tuning the types of heterojunction nanostructures by regulating the concentration of Fe3+ and calcination temperature. As a result, the feeding ratios of bismuth ferrite materials Bi2Fe4O9, BiFeO3/Bi2Fe4O9, BiFeO3, BiFeO3/Bi25FeO40, and Bi25FeO40 are 2:1, 1.5:1, 1:1, 0.75:1, 0.5:1, and 0.04:1, respectively. Besides, the calcination temperature not only influences the granularity of bismuth iron oxide but also promotes the phase transformation from BiFeO3 to Bi2Fe4O9. Moreover, BiFeO3/Bi2Fe4O9 and BiFeO3/Bi25FeO40 heterojunction nanostructures display strong interactions between BiFeO3–Bi2Fe4O9 and Bi25FeO40. Besides, BiFeO3/Bi25FeO40 heterojunction nanostructures exhibit obvious grain boundary with the smallest bandgap. This study presents far-reaching implications and provides pathways to prepare BiFeO3/Bi2Fe4O9 and BiFeO3/Bi25FeO40 heterojunction nanostructures.

Polyacrylamide gel synthesis of Ni1-xCuxAl2O4 nano-pigments with photocatalytic properties

Ni1-xCuxAl2O4 (x = 0, 0.25, 0.50, 0.75, and 1) nanoparticles were prepared via a polyacrylamide gel method. The compounds were characterized by Fourier Transform infrared spectroscopy, thermal analysis, X-ray diffraction, UV–vis diffuse reflectance, and scanning electron microscopy. The produced powders were studied for dual applications of pigment and photocatalyst. The results showed that a spinal structure with an average particle size of 70 nm was obtained via this polymer-assisted synthesis method. The substitution of copper in the structure of nickel aluminate caused an increase in crystallite size growth, whereas it decreased the band gap energy of the samples. DRS results demonstrated that the band gap energy of Ni1-xCuxAl2O4 with x = 0 reduced from 3.4 eV to 2.51 eV for the sample with x = 0.75. The CIE colorimetric values of the samples showed that the color of the nanoparticles changed from cyan for x = 0 to brown for x = 0.75. The photocatalytic investigations revealed that all the produced powders can effectively remove methylene blue pollution from water.

Machine-Learning-Driven G-Quartet-Based Circularly Polarized Luminescence Materials.

Circularly polarized luminescence (CPL) materials have garnered significant interest due to their potential applications in chiral functional devices. Synthesizing CPL materials with a high dissymmetry factor (glum ) remains a significant challenge. Inspired by efficient machine learning (ML) applications in scientific research, this work demonstrates ML-based techniques for the first time to guide the synthesis of G-quartet-based CPL gels with high glum values and multiple chiral regulation strategies. Employing an "experiment-prediction-verification" approach, this work devises a ML classification and regression model for the solvothermal synthesis of G-quartet gels in deep eutectic solvents. This process illustrates the relationship between various synthesis parameters and the glum value. The decision tree algorithm demonstrates superior performance across six ML models, with model accuracy and determination coefficients amounting to 0.97 and 0.96, respectively. The screened CPL gels exhibiting a glum value up to 0.15 are obtained through combined ML guidance and experimental verification, among the highest ones reported till now for biomolecule-based CPL systems. These findings indicate that ML can streamline the rational design of chiral nanomaterials, thereby expediting their further development.

Design and Synthesis of a Water-Resistant Mesoporous Silica Gel for the VOC Adsorption–Desorption Treatment

Design and Synthesis of a Water-Resistant Mesoporous Silica Gel for the VOC Adsorption–Desorption Treatment

ZnO Precursor’s ability to catalyze formation of reactive oxygen species to degrade aqueous organic pollutants

Advanced oxidative processes (AOP) could mitigate emerging and persistent pollutants in drinking water. Yet there is a dearth of economical materials to generate the reactive oxygen species (ROS) that are responsible for pollutant degradation in AOPs. In this work, we design a zinc hydroxychloride monohydrate (ZHCM) silicon dioxide photocatalytic nanocomposite to generate ROS for non-selective degradation of drinking water contaminants. ZHCM is an intermediate phase in the sol–gel synthesis of ZnO-SiO2-Ag nanocomposites containing 63–100 % ZnO. Typically, ZHCM is calcinated around 500 °C to crystallize into ZnO, yet we find that this calcination step may decrease photocatalytic activity. ZHCM exhibited higher methylene blue degradation efficiency through both catalysis (31 % after 4 h) and photocatalysis (98 % after 4 h) compared to the ZnO composites (∼0% and 78 % after 4 h). ZHCM had the highest photodegradation efficiency for ciprofloxacin and caffeine. The increased catalytic and photocatalytic activity of these model pollutants is attributed to the generation of two ROS: superoxide anions in UV light and peroxide anions in the absence of light. These ROS were identified using a new modified biological assay measuring the chemiluminescence of luminol in the presence of horseradish peroxidase. Results are further verified via scavenger quenching tests. The ZHCM and ZnO-SiO2-Ag are characterized for their antimicrobial activity measured by E. coli growth inhibition zones, band gaps, crystalline domains, and surface areas. This work demonstrates the potential to synthesize, at lower temperatures, a photocatalyst with enhanced ROS generation and reduced UV dependency.

Study of the behavior of the 4-DASPI dye in samples of silicate hydrogel by fluorescence spectroscopy and quantum chemistry

The behavior of the 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (4-DASPI) dye in samples of silicate hydrogel obtained from tetrakis(2-hydroxyethyl) orthosilicate with the dye added at the synthesis stage or adsorbed on a previously synthesized hydrogel substrate is studied by luminescence spectroscopy and molecular dynamics and quantum chemistry calculations. Small hypsochromic shifts of the fluorescence spectra of the dye upon its interaction with silica are observed. Energies of adsorption of 4-DASPI in the ground and excited state on two types of amorphous silica are calculated and contributions of Coulomb and dispersion interactions are estimated. A transition of the 4-DASP+ cation to the TICT state upon its excitation in water and methanol solutions is proved by TD DFT calculations. Partial twisting of the 4-DASP+ cation on silica, both in the pore and on the surface, is proposed based on the results of calculations and experimental measurements. The main difference between the samples synthesized with the introduction of 4-DASPI into the reaction mixture and by the gel synthesis followed by the adsorption of 4-DASPI seems to be capturing of the dye molecule in a pore in hydrogel with freezing molecular vibrations and rotations and, consequently, the growth of fluorescence intensity in the first case and the adsorption of the dye on the silica surface with relatively easy molecular vibrations and hindered rotations in the second case. This explains a strong difference in the intensities of fluorescence bands in the spectra of the studied samples.

Controlled Synthesis of Proton-Conductive Porous Organic Polymer Gels via Electrostatically Stabilized Colloidal Formation

Controlled Synthesis of Proton-Conductive Porous Organic Polymer Gels via Electrostatically Stabilized Colloidal Formation

Sol–gel synthesis of strontium ferrate (SrFeO3) nanoparticles and evaluation of anti-leukemic effects against leukemic cell lines

Sol–gel synthesis of strontium ferrate (SrFeO3) nanoparticles and evaluation of anti-leukemic effects against leukemic cell lines

Investigations on structural, morphological, dielectric, and ferroelectric properties of BiFeO3/BiMnO3 composite ceramics prepared via sol–gel synthesis route

In this work, we report the preparation of BiFeO3/BiMnO3 (BFO/BMO) composite material, via the chemical substitution method, by adopting the sol–gel method. The X-ray diffraction studies confirmed the formation of two distinct phases in the prepared sample. Field emission scanning electron microscopic images revealed the two different morphologies, and the compositional studies verified the presence of the respective elements in these different grains. The dielectric constant value almost doubled in the composite sample than the single-phase BFO sample. The dielectric constant values at a frequency of 105 Hz were found to be 46 and 73 for the BFO and BFO/BMO samples, respectively. The remnant polarization value was found to reduce from 8.3 µC/cm2 (for BFO) to 0.3 µC/cm2 for biphasic BFO/BMO samples.

Zirconia nanoparticles unveiled: multifaceted insights into structural, mechanical, and optical properties

Abstract This work reports the sol–gel synthesis of zirconia (ZrO2) nanoparticles (NPs) in which the effect of varying molarities of zirconium oxychloride salt (such as 0.025 M, 0.050 M, 0.075 M, 0.100 M, and 0.125 M) has been investigated on the structural, mechanical, and optical characteristics by maintaining a basic pH at 9. All experimental conditions were conducted using basic media, with XRD, SEM, hardness, and optical analysis performed. Structural analysis, which was performed by using an X-ray diffractometer, reveals the formation of mixed phase zirconia (tetragonal and monoclinic) under as-synthesized conditions. Optical analysis shows that transmission increases as the molarity grows. The refractive index and extinction coefficient conform to the normal dispersion behavior, while the refractive index is observed to increase as the molarity becomes large. A high value of the refractive index of about 1.65 and lowest value of band gap 3.96 eV have been observed at a molarity of 0.075 M in the UV region. The hardness is observed to be continuously increased as the molarity grows, wherein the maximum hardness of 1167 HV is observed at a molarity of 0.075 M within the considered molarities (0.025 M, 0.050 M, 0.075 M, 0.100 M, and 0.125 M).

Synthesis of Silica Gel Chelated with Alizarin and 1-Nitroso-2-Naphthol for Solid Phase Extraction of Lead in Ground Water Samples

Silica gel chemically functionalized with alizarin (Si-AZ) and 1-nitroso-2-naphthol (Si-NN) was synthesized and characterized by FT-IR, N2 adsorption-desorption, SEM, and elemental analysis. The two chelators show adequate sorption properties for Pb (II) and are hence used as SPE sorbents prior to their determination with ICP-MS. Both chelators showed high sorption efficiency for the Pb (II) ion at pH 8. Batch experiments demonstrate that the synthesized resins could remove more than 95% Pb (II) out of solutions containing 100 μg/mL of the ion. At optimum conditions, the maximum adsorption capacities for S-TDI-AZ and S-TDI-NN for Pb (II) were 9.56 and 9.43 mg/g, respectively. Method development was performed to investigate the applicability of the chelating resins as packing materials for SPE using model solutions and real groundwater samples. The method detection limits of SPE were 0.0025 and 0.0026 μg/L with high precision (R.S.D. < 3%). The recoveries of spiked Pb (II) with ground water were 104.70 and 102.62%. The proposed method was successfully applied to the determination of Pb (II) in the groundwater by ICP-MS.

Correction: Sol–gel synthesis and physical properties of Ni–Cu based spinel ferrites nanoparticles

Correction: Sol–gel synthesis and physical properties of Ni–Cu based spinel ferrites nanoparticles

Synthesis and performance evaluation of multi-crosslinked preformed particle gels with ultra-high strength and high-temperature and high-salinity resistance for conformance control

Preformed particle gels (PPGs) have been identified as an effective method to control conformance and mitigate excessive water production. However, the weak strength of swollen PPGs makes them susceptible to shear failure during formation migration in harsh reservoir conditions. To address this issue, a novel type of multi-crosslinked preformed particle gels (MC-PPGs) with ultra-high strength, exceptional temperature and salinity resistance has been developed. Vinyl silica nanoparticles (VSNPs) were first prepared and used as nano crosslinking agents and enhancing agents in constructing multiple cross-linking structures with macromolecules, functional monomers, and crosslinking agents. MC-PPGs have an elastic modulus up to 110,000 Pa, which is significantly higher than other existing PPGs. Additionally, when exposed to high-salinity environments (e.g., 20 % NaCl and 10 % CaCl2 + 10 % MgCl2), MC-PPGs remain for an extended period at elevated temperatures (80 °C for 24 months, 120 °C for 13 months, and over one month at 160 °C). Furthermore, the degradation products of MC-PPGs have minimal impact to reservoir permeability, with a core damage rate below 5 %. MC-PPGs are pH-adaptable (1 < pH < 12), which makes them a promising candidate for reservoirs with supercritical CO2 flooding. Laboratory coreflooding tests have demonstrated that MC-PPGs provide excellent plugging efficiency (>99.9 %) for fractured cores and ultra-high breakthrough pressure gradients (>14 MPa/m) at varying test temperatures (20 °C, 80 °C, and 120 °C). Considering these unique features, MC-PPGs are ideally suited for oilfield applications.

Hybrid Sol–Gel and Spark Plasma Sintering to Produce Perovskite-like SrTiO3 Ceramics for Radioactive Waste Isolation

The paper presents a reliable technology combining sol–gel synthesis and spark plasma sintering (SPS) to obtain SrTiO3 perovskite-type ceramics with excellent physicomechanical properties and hydrolytic stability for the long-term retention of radioactive strontium radionuclides. The Pechini sol–gel method was used to synthesize SrTiO3 powder from Sr(NO3)2 and TiCl3 (15%) precursors. Ceramic matrix samples were fabricated by SPS in the temperature range of 900–1200 °C. The perovskite structure of the synthesized initial SrTiO3 powder was confirmed by X-ray diffraction and thermal analysis results. Scanning electron microscopy revealed agglomeration of the nanoparticles and a pronounced tendency for densification in the sintered compact with increasing sintering temperature. Chemical homogeneity of ceramics was confirmed by energy dispersive X-ray analysis. Physicochemical characteristic studies included density measurement results (3.11–4.80 g·cm−3), dilatometric dependencies, Vickers microhardness (20–900 HV), and hydrolytic stability (10−6–10−7 g·cm−2·day−2), exceeding GOST R 50926-96 and ISO 6961:1982 requirements for solid-state matrices. Ceramic sintered at 1200 °C demonstrated the lowest strontium leaching rate of 10−7 g/cm2·day, optimal for radioactive waste (RAW) isolation. The proposed approach can be used to fabricate mineral-like forms suitable for RAW handling.