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In order to fully realize room temperature multiferroicity, a release of remnant magnetization in the BiFeO 3 (BFO) system is still needed. Herein, we describe novel Re-substituted BiFe 1-x Re x O 3 compounds that were synthesized using an aqueous sol-gel procedure when ethylene glycol was used as a complexing agent. Rhenium substitution was used to disrupt the modulated magnetic structure due to its aliovalent nature and maintain electroneutrality in case of Bi evaporation. Obtained compounds were investigated using X-ray powder diffraction (XRD) analysis coupled with Rietveld refinement, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), as well as magnetometry measurements. The obtained data revealed that only tiny amounts of Re (≤0.75 %) can be introduced instead of Fe ions while maintaining a single-phase structure. Larger inclusions lead to the formation of two impurity phases with Pbam and I2 1 3 space groups. However, the typical R3c bismuth ferrite crystal structure remained dominant. SEM analysis indicated that the inclusion of Re ions into the crystal structure caused an increase in average particle size. XPS analysis confirmed the designed chemical compositions of the samples as well as the small amount of Fe2+, which is formed to compensate for the Re ions in the 6+ and 7+ states. Magnetometry measurements revealed that even sub 1 % of Re substitution led to a presence of non-zero remnant magnetization, which reaches 0.0449 Am2kg−1 at room temperature in the compound with x = 0.0075. [ABSTRACT FROM AUTHOR]

A porous anti-reflective coating (P-ARC) with average transmittance in the visible range of 97.9% was fabricated through the sol-gel method, followed by calcination at a relatively low temperature (220 °C) using the porogen of Laureth-5 carboxylic acid via a one-step approach. The results demonstrated the coating had an absolute value that was 7.5% higher than that of bare glass (92%). The prepared porous anti-reflective coating had a refractive index as low as 1.21. The coating remained undamaged during 3M tape stripping tests while maintaining excellent light transmittance. This work presents a film that has good thermal stability, chemical stability, and mechanical stability. [ABSTRACT FROM AUTHOR]

This comprehensive review examines the current state of self-cleaning nanocoatings for building surfaces. Nanocoatings are a form of nano-structured materials that contain active components, such as photocatalysts, that provide superior self-cleaning properties when exposed to light. This review discusses the various materials and methods used in the development of selfcleaning nanocoatings, including titanium dioxide, zinc oxide, and other metal oxide. The properties of these materials, such as photocatalytic activity, durability, and water repellency are described in detail. The review also provides a comprehensive overview of the preparation methods for nanocoatings, including physical vapor deposition, chemical vapor deposition, and sol-gel processing. Finally, the review concludes with a discussion of the potential applications of self-cleaning nanocoatings for building surfaces, such as reducing maintenance costs, improving aesthetics, and increasing energy efficiency. [ABSTRACT FROM AUTHOR]

Cloud seeding is a weather modification technique aimed at enhanced precipitation from clouds. Silver iodide, the material used in cloud seeding, is toxic to aquatic life. Therefore, precipitation from seeded clouds is harmful to the environment. In response to the concern, we report a novel approach of developing AgI loaded/encapsulated silica seed material for possible cloud seeding process. The traditional sol–gel alkoxide route is adopted to develop AgI/Silica composite. The obtained composite fulfils the requirement of seed material with high surface area (> 1000 m2/g), meso-porous structure, and low density (~ 0.2 g/cm3), which are the main requirements for cloud seeding programme. [ABSTRACT FROM AUTHOR]

The catalytic wet air oxidation (CWAO) of p-hydroxybenzoic acid (p-HBA) was conducted in a batch reactor at 140 °C, and at a total air pressure of 50 bar over Ru-based catalysts. Four materials were selected as supports – TiO2, CeO2–TiO2, ZrO2–TiO2, and La2O3–TiO2 – all of which had mesopores in their texture and pollutant adsorption capacities. The supports were prepared by the sol-gel method, and then impregnated with 3 wt% of Ru precursor. Such characterization techniques as N2-sorption, XRD, XPS, H2–TPR, NH3-TPD, TEM, and HAADF-STEM were used to analyze the different solids. The correlation between catalytic activities and physicochemical properties was discussed. A significant specific surface area (SBET), a large amount of surface-active oxygen, and Lewis acidity sites were observed on cerium-containing catalysts (Ru/CeTi). Fresh Ru catalysts containing cerium showed higher activity than Ru/TiO2, Ru/ZrTi, and Ru/LaTi catalysts. It is assumed that the acidic sites and surface oxygen trap the p-HBA molecule, thus increasing the catalytic properties of the Ru particles which interact with the surface oxygen through the cerium redox process (Ce3+/Ce4+). As the presence of cerium increases surface-active oxygen, it inhibits the deposition of carbon on the surface of the Ru catalyst. The pseudo-second order (PSO) model adequately described the kinetic data of the p-HBA oxidation reaction using Ru catalysts.

Channel waveguides with diffraction gratings at their input and output for light injection and extraction, respectively, constitute the key components for applications in integrated optics and photonics. Here, we report for the first time on such fluorescent micro-structured architecture entirely elaborated on glass by sol-gel processing. This architecture particularly takes advantage of a high-refractive index and transparent titanium oxide-based, sol-gel photoresist that can be imprinted through a single photolithography step. This resist enabled us to photo-imprint the input and output gratings on a photo-imprinted channel waveguide doped with a ruthenium complex fluorophore (Rudpp). In this paper, the elaboration conditions and optical characterizations of derived architectures are presented and discussed with respect to optical simulations. We firstly show how the optimization of a two-step deposition/insolation sol-gel procedure leads to reproducible and uniform grating/waveguide architectures elaborated on rather large dimensions. Then, we show how this reproducibility and uniformity govern the reliability of fluorescence measurements in waveguiding configuration. These measurements demonstrate that: (i) our sol-gel architecture is well adapted to the efficient channel–waveguide/diffraction grating coupling at the Rudpp excitation and emission wavelengths; (ii) it enables an efficient propagation of the emission signal in the core of the waveguide allowing its photo-detection after extraction through the output grating; and (iii) it is affected by very reduced parasitic mechanisms, such as propagation losses and photobleaching features. This work constitutes a promising preliminary step toward the integration of our architecture in a microfluidic platform for further fluorescence measurements in liquid medium and waveguiding configuration. [ABSTRACT FROM AUTHOR]

Single phase and highly transparent ZnO:Tb films with a Tb concentration from 0.41 at% up to 0.78 аt% were formed on glass and silicon substrates by sol-gel deposition. The influence of ultraviolet radiation on the structural and photoelectric characteristics of n-ZnO:Tb/n-Si structures has been studied. The appearance of a photoelectric effect under the influence of a bias voltage and UV radiation (405 and 278 nm) was established, with an increase in photo effect when irradiated with shorter wavelength UV radiation (278 nm). It was shown that the concentration of the Tb3+ dopant is the determining factor for increasing the UV photosensitivity of the structures. The experimentally established selective sensitivity of n-ZnO:Tb/n-Si structures to UV radiation with a wavelength of less than 405 nm demonstrates the possibility of their use in UV radiation detectors or sun-blind detectors. [ABSTRACT FROM AUTHOR]

Carbon nanostructure (CNS)-based glass composites are an emerging area of research owing to the ability of these structures to dramatically alter the properties of the host glass. Due to their impressive electrical, mechanical, optical, and thermal properties, the novel characteristics imparted to the glass system with their incorporation have opened up new horizons for the development of innovative nanocomposite materials that can be used in different fields such as energy storage devices, sensors, actuators, optics, laser technology. Although several studies have been conducted on the inclusion of CNSs in polymer matrices, inorganic systems have gained relatively less attention. This review provides an overview of two principal synthesis techniques employed by researchers for the fabrication of these composites, i.e., melt-quenching and sol–gel processing. It summarizes the results obtained by researchers highlighting the role of CNSs in enhancing the functional properties of the host matrices. [ABSTRACT FROM AUTHOR]

Modern material processing methods are revolutionizing the biomedical and health care sectors while offering previously unexplored possibilities for the development of cutting-edge biomaterials. The development of materials with distinctive optical, mechanical, and biological characteristics can be made feasible by innovative techniques such as chemical vapor deposition (CVD) & sol-gel processing. These developments have a wide range of applications such as biological sensing technologies, drugs delivery systems, as well as tissue engineering. The present investigation examines the application of chemical vapor deposition (CVD) and sol-gel techniques for producing biomaterials customized for certain biomedical applications. The development of nanomaterials, such as mesoporous silica nanoparticles, biologically active glass nanoparticles, and graphene-based coatings, will be discussed in particular. These materials were chosen for their adaptability and demonstrate promise in a number of medical domains, including the advancement of diagnostic imaging techniques, medication delivery systems, and wound healing processes.

Mesoporous phosphate bioactive glasses (MPBGs) are novel and attractive biomaterials for biomedical applications. Here we report the sol-gel processing of P2O5-CaO and P2O5-CaO-Li2O MPBGs using Pluronic P123 as the surfactant. Our results showed that P123 could act as a crystallization inhibitor, thus extending the composition range of MPBGs. The concentration of CaO from 40 to 55 mol% in P2O5-CaO MPBGs did not affect the phosphate chain structure and mesoporous morphology. However, the specific surface area and pore volume were slightly enhanced with the increased CaO concentration. In ternary P2O5-CaO-Li2O MPBGs, the increase in Li2O concentration (from 5 to 20 mol%) did not alter the phosphate chain structure and mesoporous morphology. However, 20 mol% Li2O incorporation induced crystallization. Binary and ternary MPBGs showed relatively low acellular bioactivity as indicated by the slow formation of hydroxyapatite in physiological fluids. Sol-gel processing is a feasible strategy for synthesizing P2O5-CaO and P2O5-CaO-Li2O MPBGs.

Hierarchical porous silicon carbide (SiC) attracts great attention due to its superior chemical resistance, high thermal shock resistance, and excellent thermal stability. The preparation of a porous SiC monolith via a simple sol–gel method is limited by either the high cost of the raw materials or the special time-consuming drying process. Herein, we report an ambient drying sol–gel approach for the synthesis of organic–inorganic hybrid monolithic gels which can be converted into hierarchical porous SiC monoliths upon pyrolysis at 1400 °C. The as-synthesized SiC monoliths possess hierarchical pores with macropores of 4.5 µm and mesopores of 2.0 nm. The porosities, specific surface areas and compressive strengths of the hierarchical porous SiC monoliths are 71.3%, 171.5 m2/g and 7.0 ± 0.8 MPa, respectively. [ABSTRACT FROM AUTHOR]

Porous MgF2 antireflective λ/4 films were prepared by sol–gel processing and coated with an additional top layer by electron beam evaporation. Scanning Electron Microscopy was applied to characterize the microstructure of the bilayer assembly. It can be shown that the top layer has a protective effect in terms of abrasion resistance and reduced solubility in water. In a second step the thickness of the two film systems has been matched to achieve optimum antireflection properties. Highlights: MgF2 was evaporated on sol–gel derived porous antireflective MgF2 coatings. The microstructure of the bilayer assemblies was characterized by scanning electron microscopy (SEM). The evaporated layer provides improved abrasion resistance and reduced water solubility. [ABSTRACT FROM AUTHOR]

MgF2 coating solutions were prepared by the fluorolytic processing of Mg(OEt)2 and MgCl2. Parts of these sols are solvothermally treated in an autoclave at 160 °C. The two respective precursors were used to prepare porous λ/4 antireflective films by dip-coating on soda-lime and borosilicate glass substrates. UV–Vis spectroscopy and X-Ray diffraction (XRD) were applied to characterize the films as a function of annealing temperature. Samples treated at 500 °C underwent testing of abrasion resistance and water solubility. Highlights: Parallel investigation of MgF2 antireflective coatings prepared from as-prepared sols and sols that have been solvothermally treated. Systematic comparison of results obtained on soda-lime and borosilicate glass substrates. Testing of abrasion resistance of porous films. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic nanocomposites combine the distinct properties of the organic polymer and the inorganic filler, resulting in overall improved system properties. Monodisperse porous hybrid beads consisting of tetraethylene pentamine functionalized poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) particles and silica nanoparticles (SNPs) were synthesized under Stoeber sol-gel process conditions. A wide range of hybrid organic/silica nanocomposite materials with different material properties was generated. The effects of n(H2O)/n(TEOS) and c(NH3) on the hybrid bead properties particle size, SiO2 content, median pore size, specific surface area, pore volume and size of the SNPs were studied. Quantitative models with a high robustness and predictive power were established using a statistical and systematic approach based on response surface methodology. It was shown that the material properties depend in a complex way on the process factor settings and exhibit non-linear behaviors as well as partly synergistic interactions between the process factors. Thus, the silica content, median pore size, specific surface area, pore volume and size of the SNPs are non-linearly dependent on the water-to-precursor ratio. This is attributed to the effect of the water-to-precursor ratio on the hydrolysis and condensation rates of TEOS. A possible mechanism of SNP incorporation into the porous polymer network is discussed. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy has been used to study structural evolution of zinc oxide synthesized by a sol–gel process adapted to flexible electronics. We assessed the effect of ultraviolet irradiation time on the atomic percentages of different Zn, O, and C species. Increasing the UV treatment time from 90 to 150 min has been shown to considerably reduce zinc concentration in the surface layer, which is accompanied by an increase in the percentage of carbon, predominantly in the form of highly oriented pyrolytic graphite. Photoactivation processes ensure completion of surface structure formation and lead to enrichment of the ZnO surface in oxygen with a binding energy of 531.5 eV, resulting in a zinc-deficient solid solution. [ABSTRACT FROM AUTHOR]

In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated sol–gel silica materials were placed on the glass surfaces in order to achieve the antireflective and hydrophobic fluorinated hybrid films. The structure and surface properties of the final samples were investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet/visible spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) determinations. FTIR spectra demonstrated the presence of a silica network modified with alkyl and fluoroalkyl groups. Thermal analysis showed that the fluorinated sol–gel silica materials prepared with HDTMES have a good thermostability in comparison with other samples. Ultraviolet/visible spectra indicated that the fluorinated hybrid films present a reflectance of ~9.5%, measured at 550 nm. The water contact angle analysis found that the wettability of fluorinated hybrid films was changed from hydrophilic (64°) to hydrophobic (~104°). These hybrid films based on fluorinated sol–gel silica materials can be useful in various electronics and optics fields. [ABSTRACT FROM AUTHOR]

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH2), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol–gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N2 sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH2 material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)6]3−. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s−1, indicating a fast direct electron transfer rate of [Fe(CN)6]3− to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb2+ ions on TalcNH2/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10−8 M (S/N = 3) and 24.84 × 10−8 M (S/N 10), for the determination of Pb2+ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb2+ ions by the grafted NH2 groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors. [ABSTRACT FROM AUTHOR]

Yttrium manganite, YMnO3, was doped with different concentrations of titanium (x = 0, 0.04, 0.08, 0.10, 0.15, 0.20) in order to improve the microstructural and multiferroic properties. The powders were prepared using sol-gel polymerization complex method from citrate precursors. Depending on the titanium concentration, the hexagonal structure and/or the rhombohedral superstructure are present in the sintered samples. The YMn1–xTixO3+δ (x = 0.10, 0.15, 0.20) ceramic samples showed significantly reduced density of microcracks, and of inter- and intragranular pores, and relative densities greater than 90%. The structural parameters for YMn1–xTixO3+δ (x = 0, 0.10, 0.15) were correlated with the results of magnetic and ferroelectric measurements. The most of titanium-doped samples showed a reduction of the leakage current density in comparison with undoped YMnO3, and their ferroelectric responses were slightly improved. The modifications in structural arrangement resulted in partial suppression of ideal antiferromagnetic ordering visible through decrease of the Néel temperature and Weiss parameter, as well as the appearance of weak ferromagnetism and increase of magnetization (especially, in samples x = 0.08, 0.10, 0.15). These changes in physical quantities most likely originated from incorporation of the uncompensated magnetic moments and possible spin canting induced by enhanced symmetry break of the superexchange bridges. Highlights: Synthesis of YMn1−xTixO3+δ (x = 0–0.20) powders using sol-gel polymerization complex method. Synthesis method and doping reduced microdefects and increased ceramics' relative density. The leakage currents decreased in YMn1−xTixO3+δ ceramics upon doping. Reduction in geometrical frustration of antiferromagnetic structure after Ti-doping. Enhanced weak ferromagnetic response in YMn1−xTixO3+δ (x = 0.10, 0.15, 0.08) samples. [ABSTRACT FROM AUTHOR]

Channel waveguides with diffraction gratings at their input and output for light injection and extraction, respectively, constitute the key components for applications in integrated optics and photonics. Here, we report for the first time on such fluorescent micro-structured architecture entirely elaborated on glass by sol-gel processing. This architecture particularly takes advantage of a high-refractive index and transparent titanium oxide-based, sol-gel photoresist that can be imprinted through a single photolithography step. This resist enabled us to photo-imprint the input and output gratings on a photo-imprinted channel waveguide doped with a ruthenium complex fluorophore (Rudpp). In this paper, the elaboration conditions and optical characterizations of derived architectures are presented and discussed with respect to optical simulations. We firstly show how the optimization of a two-step deposition/insolation sol-gel procedure leads to reproducible and uniform grating/waveguide architectures elaborated on rather large dimensions. Then, we show how this reproducibility and uniformity govern the reliability of fluorescence measurements in waveguiding configuration. These measurements demonstrate that: (i) our sol-gel architecture is well adapted to the efficient channel–waveguide/diffraction grating coupling at the Rudpp excitation and emission wavelengths; (ii) it enables an efficient propagation of the emission signal in the core of the waveguide allowing its photo-detection after extraction through the output grating; and (iii) it is affected by very reduced parasitic mechanisms, such as propagation losses and photobleaching features. This work constitutes a promising preliminary step toward the integration of our architecture in a microfluidic platform for further fluorescence measurements in liquid medium and waveguiding configuration.

The wet chemistry route has been developed to prepare calcium hydroxyapatite (Ca10(PO4)6(OH)2, (HA)) thin films on a silicon substrate using the novel low-temperature sol-gel and dissolution-precipitation approach. The calcium carbonate thin films on the silicon substrate were obtained by spin-coating technique when substrates were repeatedly coated with 10, 20 and 30 layers of sol-gel solution. The composites formed of crystalline and amorphous CaCO3 were obtained by calcination of the coatings for different time at 600°C. A dissolution-precipitation procedure was used for the preparation of calcium hydroxyapatite thin films on silicon substrate at 80°C. The obtained synthesis products were characterised by X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM) and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Hierarchical porous silicon carbide (SiC) attracts great attention due to its superior chemical resistance, high thermal shock resistance, and excellent thermal stability. The preparation of a porous SiC monolith via a simple sol–gel method is limited by either the high cost of the raw materials or the special time-consuming drying process. Herein, we report an ambient drying sol–gel approach for the synthesis of organic–inorganic hybrid monolithic gels which can be converted into hierarchical porous SiC monoliths upon pyrolysis at 1400 °C. The as-synthesized SiC monoliths possess hierarchical pores with macropores of 4.5 µm and mesopores of 2.0 nm. The porosities, specific surface areas and compressive strengths of the hierarchical porous SiC monoliths are 71.3%, 171.5 m2/g and 7.0 ± 0.8 MPa, respectively.

Hybrid organic/inorganic nanocomposites combine the distinct properties of the organic polymer and the inorganic filler, resulting in overall improved system properties. Monodisperse porous hybrid beads consisting of tetraethylene pentamine functionalized poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) particles and silica nanoparticles (SNPs) were synthesized under Stoeber sol-gel process conditions. A wide range of hybrid organic/silica nanocomposite materials with different material properties was generated. The effects of n(H2O)/n(TEOS) and c(NH3) on the hybrid bead properties particle size, SiO2 content, median pore size, specific surface area, pore volume and size of the SNPs were studied. Quantitative models with a high robustness and predictive power were established using a statistical and systematic approach based on response surface methodology. It was shown that the material properties depend in a complex way on the process factor settings and exhibit non-linear behaviors as well as partly synergistic interactions between the process factors. Thus, the silica content, median pore size, specific surface area, pore volume and size of the SNPs are non-linearly dependent on the water-to-precursor ratio. This is attributed to the effect of the water-to-precursor ratio on the hydrolysis and condensation rates of TEOS. A possible mechanism of SNP incorporation into the porous polymer network is discussed.

Microfluidic generation of emulsion microdroplets, combined with external gelation, is a promising method for the continuous production of high-quality ceramic microspheres. However, the external gelation mode is sensitive to the environmental concentration of sol-gel triggering agent, resulting in gel deformation due to uneven infiltration and reaction within the sol microdroplets. In this work, a polyacrylamide (PAM) gel network was used to prevent the microdroplets from undergoing apparent deformation throughout the gelation process, and dense ZrO 2 microspheres with high monodispersity and sphericity were fabricated successfully. Importantly, owing to the assistance of PAM network, the external gelation process becomes less sensitive and can be treated with a substantially higher triggering agent concentration, thus allowing a faster and more efficient sol-gel production of ZrO 2 ceramic microspheres. [ABSTRACT FROM AUTHOR]

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH2), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol–gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N2 sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH2 material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)6]3−. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s−1, indicating a fast direct electron transfer rate of [Fe(CN)6]3− to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb2+ ions on TalcNH2/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10−8 M (S/N = 3) and 24.84 × 10−8 M (S/N 10), for the determination of Pb2+ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb2+ ions by the grafted NH2 groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors.

The metal compound of nanosize tricalcium phosphate, which is based on lime mineral and phosphoric acid, prepared by the sol–gel method, is investigated. The functional group of tricalcium phosphate is confirmed from the FTIR spectrum results, in which a hydroxyl functional group (−OH) tends to disappear at the temperature of 800°C and 1000°C. With both deficiency optimum number of –OH (3564 cm−1 ) and increase of the functional groups of PO4 3− (567 cm−1 and 601 cm−1 ) as asymmetry bending and PO4 3− (1039 cm−1, 962 cm−1, and 900 cm−1 ) as asymmetry stretching vibration modes, the metal compound is formed as tricalcium phosphate (TCP). The crystallographic plane orientations for metastable α-TCP are (001), and for rhombohedral β-TCP, they are (002) and (200), that is found from the XRD results. However, the crystallographic plane orientation for hexagonal α'-TCP is still unformed due to its temperature unreached. Inhomogeneous crystallites of the metal-compound nanosize tricalcium phosphate are confirmed in the relating parameters of crystallite sizes, strains, and dislocations, whereas the crystallinity increases when their temperature increases and is occurred at 800°C and 1000°C with numbers of ≅ 72% and ≅ 77%, respectively. The thermal characterisation is obtained by the specific heat capacity, the fusion and crystallization enthalpies, and weight loss calculated from results of differential scanning calorimetry–thermogravimetric (DSC–TG) and differential thermogravimetric (DTG) analyses. [ABSTRACT FROM AUTHOR]

Integrated opto-chemical sensors present great advantages in comparison to the current lab equipment. They bring portability, reduced costs, facilitate in-situ measurements, as well as largely reduced sample volumes. In this quest, standard processing protocols over established materials, such as silicon nitride, silicon, silicon dioxide, titanium oxide, and even a wide variety of polymers have so far been the key toward on-chip devices. However, if very specific materials in terms of composition and tailored properties are required, the deposition via a solution represents a viable alternative. In this review, we highlight the role of sol-gel chemistry and top-down processing of sol-gel thin film layers in the design of waveguide-based optical sensors. In particular, we stress the advantages of porous sol-gel based materials as a new approach to increase sensitivity and selectivity, first when used as claddings, and, more recently, as waveguides with enhanced light–analyte interaction. We finally discuss the future perspectives of such devices to increase specificity in complex matrices, which is of utmost importance for bio-sensing.

UV protection and coatings for plastics are important in many applications. The cladding of low microwave (MW) absorption composite coatings on high MW transparent plastic substrates is a challenge due to their disparate dielectric properties. Moreover, an uneven heat energy conversion within the composite creates an additional hurdle in producing a coating with good surface integrity. In this study, a protocol was developed to overcome these difficulties based on a hybrid approach. The adverse effect of temperature mismatch between the coating and substrate was reduced through a two-way susceptor-aided heating mechanism. Low MW absorbing sol–gel derived composite coatings consisting of silicon dioxide (SiO2) and titanium dioxide (TiO2) were successfully cladded on the surface of MW and visual light transparent polycarbonate to produce a clear protective coating with UV-resistance. Nanoindentation tests were conducted to assess the effectiveness of the proposed protocol. Significant enhancement in the surface elastic modulus and hardness were achieved. Highlights: A hybrid microwave cladding process has been developed for the fabrication of composite coating systems with disparate dielectric properties. The difficulty of processing low microwave absorbing and microwave transparent materials has been overcome. Fabrication of crack-free silicon dioxide (SiO2)/titanium dioxide (TiO2) composite coatings on polycarbonate substrates with enhanced surface mechanical properties has been demonstrated. This process greatly reduces the processing time from hours to less than a minute when compared to conventional methods. [ABSTRACT FROM AUTHOR]

The role of polyethylene glycol (PEG) as pore modulating agent was studied in the preparation of monoliths formed by Nb2O5 nanoparticles dispersed in a silica matrix obtained by the sol–gel process. The obtained monoliths were characterized by gas adsorption, SEM and HRTEM (EELS coupled). The silica and nanocomposite monoliths showed high specific surface area and pore size varying between micro and macropores, depending on the amount of PEG used. The silica monoliths were transparent due to the micro and small mesopores, the nanocomposites with 1 and 5% of PEG were translucid and the nanocomposite with 3% of PEG were opaque due to spinodal decomposition induced by the interaction between the polymer and the niobium pentoxide precursor (ammonium niobate oxalate hydrate), which made it a promising candidate for flow catalysis or chromatographic columns. [ABSTRACT FROM AUTHOR]

Samarium doped BiFeO 3 compounds having nano-size crystallites were prepared by the ethylene glycol assisted sol-gel synthesis method. X-ray diffraction and SEM measurements as well as Raman spectroscopy and FTIR experiments were used to clarify an evolution of the crystal structure on microscopic and local scale levels in the compounds having formula Bi 1-x Sm x FeO 3 , where 0 = x ≤ 1. Magnetization measurements along with the structural data were used to determine a correlation between magnetic properties and crystal structure of the compounds. The compounds with 0.1 = x ≤ 0.2 are characterized by the sequence of the structural transitions driven by the dopant increase, viz. from the polar rhombohedral phase to the non-polar orthorhombic phase via two-phase regions characterized by the presence of the anti-polar orthorhombic phase. The concentration regions ascribed to a coexistence of the rhombohedral and the anti-polar orthorhombic phases as well as the anti-polar orthorhombic and the non-polar orthorhombic phases are observed in the ranges 0.12 = x ≤ 0.15 and 0.15 < x < 0.18 respectively. The compounds having single phase rhombohedral structure are characterized by a release of remnant magnetization as compared to ceramics with similar chemical compositions but synthesized by the solid-state reaction method and having microscopic size crystallites. A correlation between the type of structural distortion, morphology of crystallites and an onset of remnant magnetization is discussed highlighting a difference in the evolution of crystal structure and magnetization observed for the Sm-doped ceramics prepared by modified sol-gel method and conventional solid-state reaction technique. [ABSTRACT FROM AUTHOR]

The pure rutile and Ag‐rutile nanomaterials were synthesised using sol–gel route and the effect of Ag concentration on the composite photocatalyst activity was investigated. The results show that the Ag0 particles are deposited on the rutile surface, forming Ag‐rutile heterojunctions. The high concentration of Ag is beneficial to inhibit the recombination of electrons and holes, meanwhile, excessive Ag particles will hinder the absorption of light source and adsorption of RhB molecules. Therefore, 2% of Ag rutile exhibits the highest photocatalytic activity. [ABSTRACT FROM AUTHOR]

This Letter reports the synthesis of nanoceramic composite ZnAl2O4TiO2 by using a cost‐effective and straight forward sol–gel route. X‐ray diffraction (XRD) showed the ZnAl2O4 cubic structure along with the mixed anatase‐ and rutile‐phases of TiO2. Rietveld refinement is performed using XRD pattern to study the structural parameters. Raman investigation endorsed the corresponding vibration peaks of TiO2 and ZnO. Field‐emission scanning electron microscopy evidenced the agglomerated spherical nanoparticles. Energy‐dispersive spectroscopy analysis demonstrated the elementary peaks of Zn, Al, and Ti at 4.5, 1.5, and 1 eV, respectively. LCR measurement revealed the decreased dielectric permittivity with the rise in frequency and temperature. This dielectric characteristic is attributed to the dipole movement of the charge carriers. Furthermore, the authors present the investigation of the conductivity and impedance of the prepared dielectric ceramic material. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are anionic clays with unique physical and chemical properties. In this study, an indirect sol-gel synthesis method was applied to prepare alkaline earth metal–substituted layered double hydroxides of Mg2-xMx/Al1 (M = Ca, Sr, Ba). In the sol-gel processing, metal nitrates Mg(NO3)2·6H2O, Al(NO3)3·9H2O, Ca(NO3)2·4H2O, Sr(NO3)2 and Ba(NO3)2 dissolved in deionized water were used as starting materials; and citric acid monohydrate and 1,2-ethanediol were used as complexing agents. The mixed metal oxides (MMOs) were obtained after thermal treatment of precursor gels at 650 °C and subsequently reconstructed in water to the LDHs. The synthesis products were characterized using X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM). Nitrogen adsorption by the Brunauer, Emmet and Teller (BET) and the Barret method was used to determine the surface area and pore diameter of the synthesized alkaline earth metal–substituted MMO materials. It was demonstrated for the first time that the formation of Mg2-xMx/Al1 (M = Ca, Sr, Ba) LDH from the sol-gel–derived powders depends significantly on the nature and concentration on the alkaline earth metal. [ABSTRACT FROM AUTHOR]

Spherical gamma‐alumina (γ‐Al2O3) has a wide range of applications in the field of adsorption due to its low bulk density, larger pore size, higher strength and thermal stability. In this study, spherical γ‐Al2O3 with macro‐mesopores was prepared with isopropanol aluminium as the aluminium source via a sol–gel process. Spherical γ‐Al2O3 was characterised by means of nitrogen adsorption and desorption curve, scanning electron microscope, transmission electron microscope, X‐ray diffraction and so on. The adsorption performance of the prepared spherical γ‐Al2O3 was studied by probe experiment of adsorption of acid fuchsin (AF) solution. The results showed that the spherical γ‐Al2O3, which was prepared under the condition of hydrolysis time of 1 h, hydrolysis temperature of 85°C, ageing temperature of 95°C and ageing time of 7 h, had the strongest adsorption capacity for AF, and the adsorption efficiency could reach 96.24% in 40 mg/l AF solution. In addition, after six cycles of use, the spherical γ‐Al2O3 had no damage and the adsorption efficiency still could reach 88.40%. This work provides a feasible method for the preparation of spherical γ‐Al2O3, and could also help to understand the connection between its textural properties and adsorption performance. [ABSTRACT FROM AUTHOR]

Tuneful behaviours of nano sized materials have been considered as challenge among researchers to explore the possibility of engaging in diverse applications. In particular, the zinc oxide (ZnO) nanostructured materials offer effective metallic behaviours to enhance the applications in the fuel oxidation, pigments, nonlinear optics and solar energy conversion. In the presented research, ZnO nanoparticles are successfully synthesised by (sol–gel and sol–gel and precipitation) techniques, respectively. The physicochemical behaviours of ZnO nanocrystals were inspected by x‐ray diffraction, Fourier transform infrared, field‐emission scanning electron microscopy, thermo‐gravimetric analysis, N2 physisorption and NH3 temperature‐programmed desorption techniques. The results revealed that Sol–gel method at lower pH produced smaller particle sizes with larger surface area and well‐established morphology in shorter time at lower temperature conditions, in comparison to precipitation method with higher pH, time and temperature conditions, showed bigger particles with smaller surface area, respectively. [ABSTRACT FROM AUTHOR]

The undoped titanium dioxide (TiO2) and zinc‐doped TiO2 gels were prepared by sol–gel method. The nano‐TiO2 powders were prepared by controlling the sintering temperature. The phase compositions of the sintered samples were analysed by powder X‐ray diffraction; the microstructure was analysed by high‐resolution transmission electron microscope; the photocatalytic activity was analysed by photochemical reactions instrument. The combined action of Zn2+ doping and heat treatment on phase transformation and photocatalytic performance of TiO2 were analysed. The results show that, when the Zn ion doping amount is within 1–5 mol%, it promotes the conversion of anatase to rutile transition as the presence of ZnTiO3. The photocatalytic performance of TiO2 sintered at 700°C is better than sintered at 400°C. [ABSTRACT FROM AUTHOR]

This study evaluated the biochemical, molecular, and histopathological mechanisms involved in the hypoglycaemic effect of zinc oxide nanoparticles (ZnONPs) in experimental diabetic rats. ZnONPs were prepared by the sol–gel method and characterised by scanning and transmission electron microscopy (SEM and TEM). To explore the possible hypoglycaemic and antioxidant effect of ZnONPs, rats were grouped as follows: control group, ZnONPs treated group, diabetic group, and diabetic + ZnONPs group. Upon treatment with ZnONPs, a significant alteration in the activities of superoxide dismutase, glutathione peroxidase, and the levels of insulin, haemoglobin A1c, and the expression of cluster of differentiation 4+ (CD4+), CD8+ T cells, glucose transporter type‐4 (GLUT‐4), tumour necrosis factor, and interleukin‐6 when compared to diabetic and their control rats. ZnONPs administration to the diabetic group showed eminent blood glucose control and restoration of the biochemical profile. This raises their active role in controlling pancreas functions to improve glycaemic status as well as the inflammatory responses. Histopathological investigations showed the non‐toxic and therapeutic effect of ZnONPs on the pancreas. TEM of pancreatic tissues displayed restoration of islets of Langerhans and increased insulin‐secreting granules. This shows the therapeutic application of ZnONPs as a safe anti‐diabetic agent and to have a potential for the control of diabetes. [ABSTRACT FROM AUTHOR]

Photocatalysts have been widely applied in the degradation of organic compounds using visible and ultraviolet radiation. Different synthesis approaches have been developed and optimized to produce efficient, eco-friendly, and inexpensive materials to photo-treat water samples contaminated with dyes, pigments, pesticides, and other organic pollutants. Over the last two decades magnetic materials have emerged as a potential alternative to facilitate catalyst isolation in heterogeneously catalyzed liquid-phase reactions. In this review, we focus on the discussion of several studies including the main synthesis processes and new protocol modifications for the fabrication of magnetic photocatalysts, and their impact on the catalyst morphology, efficiency, and recycling. Emphasis is given on the discussion of the synthesis strategies over last decade to produce photoactive catalysts including single-phase catalysts, composites, Multifunctional metal–organic framework materials, binary and ternary core–shell materials, and yolk–shell photocatalysts. Highlights: A review on magnetic materials for photocatalysis is given. Emphasis is given on sol–gel preparation methods utilized for the fabrication of magnetic photocatalysts. Discussion on different material types of magnetic photocatalysts is presented. Magnetic separation properties and efficiency are discussed based on the material structures. [ABSTRACT FROM AUTHOR]

Silica‐encapsulated waterborne flaky aluminium (SEWFA) is widely used in industrial fields, but its corrosion hampers its long‐term use. Herein, a sol–gel method was used to prepare graphene oxide (GO)‐modified SEWFA (GO‐SEWFA). The oxygen‐containing functional groups of GO can react with tetraethyl orthosilicate to form a well‐dispersed silica/GO matrix on the surface of GO‐SEWFA. The hydrogen evolution results demonstrated that GO covalent bonding, combined with silica encapsulation on the surface of flaky aluminium, could effectively improve the anticorrosive performance. [ABSTRACT FROM AUTHOR]

Modifying the morphology of nanostructures and its influence on the features of the tailored nanoparticles (NPs) has attracted a great deal of interest. In this research, the morphological effect on magnetic properties of the bare or modified NPs was investigated. Bare NPs were fabricated by the sol–gel route and modified NPs were prepared using hydrophilic absorbent cotton (HAC) to architect morphology of the NPs. X‐ray diffraction, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and Fourier transform infrared analyses confirmed that pure SrAl1.3Fe10.7O19 NPs were synthesised based on the modified sol–gel method. Results indicated that HAC as a novel and affordable template modified the shape of the NPs. The obtained results by the diffuse reflection spectroscopy suggest that the optical performance of the NPs can be tuned by modifying the size of them. Additionally, the hysteresis loops of the vibrating sample magnetometer attested that the saturation magnetisation (Ms) of the modified NPs was elevated. [ABSTRACT FROM AUTHOR]

Glycerolates of biogenic elements, in particular, silicon, zinc, and boron, are promising biocompatible precursors in sol–gel processing. We successfully used them in the synthesis of pharmacologically active glycerohydrogels exhibiting wound healing, regenerating, and, in some cases, immunotropic and antimicrobial effects. In this paper, a comparative in vitro study of the antimicrobial (antibacterial and antimycotic) activity of four glycerohydrogels differing in biogenic elements (silicon-, silicon–boron-, silicon–zinc-, and silicon–zinc–boron-glycerol hydrogels) was carried out. Using the methods of agar diffusion and serial dilutions, it was shown that silicon–zinc–boron-glycerol hydrogel in general exhibited higher antimicrobial activity; silicon–boron- and silicon–zinc-glycerol hydrogels possessed lower activity; silicon-glycerol hydrogel demonstrated no antimicrobial properties. Differences in antimicrobial activity are associated with the structural features of hydrogels studied using advanced physicochemical methods, including electrospray ionization mass spectrometry, 11B NMR spectroscopy, and transmission electron microscope. It was found that a dispersion medium of silicon–zinc–boron-glycerol hydrogel, which was separated by exhaustive extraction with ethanol, contained bis(glycerol)borate anions [B(C3H6O3)2]–, along with Zn2+ cations. The simultaneous presence of these ions is not characteristic of other hydrogels under study and, in our opinion, provides improved antimicrobial activity of silicon–zinc–boron-glycerol hydrogel. Boron bisglycerolates and boric acid in a dispersion medium of silicon–boron-glycerol hydrogel provides its antimicrobial activity, whereas silicon–zinc-glycerol hydrogel containing only nanoscale particles of zinc monoglycerolate in cells of the 3D polymer network is less active. Silicon–zinc–boron-glycerol hydrogel can be an efficient and safer alternative to conventional topical antimicrobial agents for treatment of diseases of skin and mucous membrane. Highlights: Silicon, zinc, and boron glycerolates are promising biocompatible precursors in sol–gel processing. The precursors were successfully used for preparation of pharmacologically active hydrogels. Combined silicon–zinc–boron-glycerol hydrogel exhibited the highest antimicrobial activity. Silicon–zinc–boron-glycerol hydrogel can be used as antimicrobial agent for topical application. [ABSTRACT FROM AUTHOR]

CoMnCrO4 spinel nanoparticles were prepared using the green and efficient sol–gel method. The synthesised nanoparticles were fully characterised by Fourier‐transform infrared spectroscopy, X‐ray powder diffraction with Rietveld refinement, transmission electron microscopy, scanning electron microscopy, and diffuse reflectance spectroscopy analysis. The characterisation of the sample showed that the CoMnCrO4 NPs have a spinel cubic structure with a crystallite size of 14 nm, narrow bandgap (1.75 eV), and uniform spherical morphology with particle size about 25–30 nm. The CoMnCrO4 NPs demonstrated high photocatalysis capability towards the Congo red dye as a pollutant with a high and fast efficiency degradation of 90% after 30 min under the visible light irradiation. Also, the impacts of different parameters consisting of nanoparticle amount, initial dye concentration, irradiation time, light and dark on dye degradation efficiency were assessed. [ABSTRACT FROM AUTHOR]

Doping is an effective way to enhance photocatalytic activity. Herein, the authors have synthesised a series of BiFe1−xTixO3 (x = 0, 0.05, 0.10, 0.15, 0.20) nanocrystals through sol–gel methods. X‐ray diffraction, Raman spectra, high‐resolution transmission electron microscopy images and X‐ray photoelectron spectroscopy characterisations indicate doping could facilitate the formation of Bi2Fe4O9 phase at low content, while inhibiting this formation at high content. Interestingly, the appearance of Bi2Fe4O9 improved the photocatalytic activity, which may be attributed to the spontaneous formation of heterostructure between Bi2Fe4O9 and BiFeO3 phases. The staggered energy bands between these two phases could effectively separate electrons and holes, resulting in enhanced photocatalytic performance. [ABSTRACT FROM AUTHOR]

In this study, solid solutions of (1-x)BaTiO 3 -xBiMnO 3 have been synthesized by an aqueous sol-gel method. It was determined that single-phase compounds can be obtained up to x = 0.6 and with further increase in percentage of BiMnO 3 component additional crystal phases were detected. Perovskite crystal structure was determined for all synthesized compounds regardless of chemical composition. Raman spectra of synthesized solid solutions showed gradual change of the shape with an increase of BiMnO 3 fraction. It was demonstrated that partial substitution of BaTiO 3 by BiMnO 3 led to the drastic growth of grains of the end products. Magnetization measurements showed that all BiMnO 3 -containing samples are characterized by paramagnetic behavior. Clear correlation between magnetization values and composition of the materials was observed, magnetization values increased with increasing of BiMnO 3 content in solid solutions. [ABSTRACT FROM AUTHOR]