Gel Synthesis Route Research Articles

Lithium doping's effects on the microstructural, dielectric, energy storage, optical and electrical properties of BaTi0.89Sn0.11O3 ceramics

The present study discusses the synthesis of lithium-doped barium stannate titanate BaTi0.89Sn0.11O3 (BTS11) using sol–gel synthesis route and explores the influence of the lithium content on their structural, morphological, ferroelectric, optical, and electrical properties. The phase of the sol–gel prepared samples with different atomic composition BaLixTi0.89Sn0.11O3(BLxTS11), with x = 0 %, 2 %, 4 %, 6 %, 8 and 10 %, was investigated using X-ray diffraction (XRD) revealing the formation of pure perovskite exhibiting lattice strain. Structural characterization was additionally conducted using Raman spectroscopy to detect structural and the chemical environment modifications caused Li incorporation. The doping induced variation also in the morphology and grain size of BLxTS11 pellets studied using SEM micrographs, which revealed evident grain size changes inversely proportional to the BLxTS11 lattice strain. The samples were then inspected for their ferroelectric properties. The maximum dielectric constant of all samples was observed at a temperature of around 45–50 °C. In addition, correlations between the chemical, structural, and morphological properties of the BLxTS11 ceramics and their energy storage capabilities were established. According to the P-E hysteresis behavior, BL6TS11 ceramic (x = 6 %) ferroelectric demonstrated the highest energy-storage capabilities, with a recoverable energy-storage density of 225 mJ/cm3 and an energy-storage efficiency of 60 %. The optical and electrical properties of the material were also investigated revealing a decrease in the band gap values and a significant increase of resistivity by Li doping.

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.

Luminescent thermometry with YVO4:Er/Nd: Achieving high sensitivities within the 1st and 2nd biological windows

YVO4:Er3+, Nd3+ powders were prepared by the modified sol gel synthesis route using glucose as chelating agent and characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Under 660 nm excitation, four infrared emission bands located between 790 and 845 nm, 870 and 930 nm, 950 and 1030 nm, and between 1050 and 1100 nm were observed, and were assigned the transitions 4F5/2 – 4I9/2 (Nd) and 4I9/2 – 4I15/2 (Er), 4F3/2 – 4I9/2 (Nd), 4I11/2 – 4I15/2 (Er), and 4F3/2 – 4I11/2 (Nd), respectively. The performance of these powders as optical temperature sensors using the luminescence intensity ratio (LIR) technique between thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) was studied within the temperature range of 293–373 K. Using different combinations of the emission intensities at 809, 880, 914 and 1003 nm, three distinct (LIR) temperature sensors schemes were built, with both excitation and emission within the first and second biological window. These LIRs relative sensitivity (Sr) and temperature uncertainties (δT) were investigated for samples with different Er and Nd concentrations. Sr values up to 2.08 ± 0.03%. K−1 and δT smaller than 1 K, were obtained. Repeatability and reproducibility tests demonstrated the reliability of the proposed LIRs.

Geopolymer Composites-In Environmentally Friendly Aspects.

In the present work, a new, low energy consumption sol-gel synthesis route has been developed for geopolymer composites. Instead of the typically published 0.1-1.0 Al/Si molar ratios, the efforts of this study concentrated on the realization of >2.5 Al/Si molar ratios in the composite systems. The higher Al molar ratio significantly improves the mechanical properties. A very important aim was also the recycling of industrial waste materials with attention to environmentally friendly requirements. The very dangerous, toxic red mud as a waste product of aluminum industrial fabrication was selected for reclamation. The structural investigation was carried out by 27Al MAS NMR, XRD, and thermal analysis. The structural examination has unambiguously proven the composite phases in both gel and solid systems. The characterization of composites was performed with mechanical strength and water solubility measurements.

Enhanced stability and electrochemical properties of lanthanum and cerium co-modified LiVOPO4 cathode materials for Li-ion batteries

A facile and efficient ball-milling assisted sol–gel synthesis route was developed to prepare triclinic ε-LiVOPO4 (LVOP) material with lanthanum (La) and cerium (Ce) modification individually as well as simultaneously. An LVOP/LaPO4/CePO4 composite cathode material was successfully synthesized and results show that La and Ce co-modification noticeably improves the electrochemical performance by enhancing the high voltage capacity upon cycling, which indicates contributions from the good ionic conductors LaPO4 and CePO4. The simultaneous La and Ce modification improves the high voltage performance significantly with an increase of 50% in high voltage capacity after 20 cycles compared to pure LVOP. It also shows stabilized cycling performance with 91% capacity retention after 50 cycles at 0.1C rate, along with high-rate capability with a capacity of 83.1 mAh/g compared to the pristine sample showing the capacity of 51. 6 mAh/g at a high rate of 5C. This can be attributed to the good conductivity of LaPO4 and CePO4. In addition, the LVOP/LaPO4/CePO4 composite and the pristine LVOP give a charge transfer resistance of ∼105 and ∼212 Ω, respectively, showing much lower impedance due to a combination of La and Ce addition.

Synthesis and Fabrication of Co1−xNixCr2O4 Chromate Nanoparticles and the Effect of Ni Concentration on Their Bandgap, Structure, and Optical Properties

In the present work, cobalt-chromite-based pigment Co1-xNixCr2O4 chromate powder and nanoparticles with various transition metal concentrations (x = 0.2, 0.4, 0.6, and 0.8) were manufactured by applying aqueous synthesis approaches and sol–gel synthesis routes. XRD analysis of the powder shows that all samples formulated by the sol–gel method were crystalline with a spinel structure. Chromites show green color with a higher nickel concentration, while Co-substituent shows blackish pigments. Samples were annealed at distinct temperatures ranging from 600 °C to 750 °C. The nanoparticles obtained were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy (RS), photoluminescence (PL), and energy-dispersive X-ray spectroscopy (EDS). The particle size of the parent compound (CoCr2O4) ranges from 100 nm to 500 nm, as measured by SEM. The tendency of particles to form aggregates with increasing annealing temperature was observed. These compounds may be successfully used as an effective doped nickel-cobalt ceramic pigment.

Red-emission analysis, Judd–Ofelt intensity parameters and laser properties of CdMgZnO:xEu3+ nanocrystals: the effects of Eu3+ concentration

In this paper, we discuss a strong red Eu3+-concentration-dependent emission line associated with an electric dipole transition (5D0 → 7F2) at 616 nm in CdMgZnO:xEu3+ nanocrystals made via a sol–gel synthesis route. Oxygen interstitial defects created by the presence of a mixed-valence state of Eu 3+ and Eu2+ ions as rare-earth cations lead to a structural distortion which is confirmed by x-ray photon electron spectroscopy. The Judd–Ofelt intensity parameters, Ω2 and Ω4, obtained from the emission spectra, show a trend for Ω2 > Ω4 that translates to stronger covalence and a stable local structure surrounding the Eu3+ ions in CdMgZnO nanocrystals. The asymmetry ratio (R o), radiative lifetime (), branching ratio , stimulated emission cross-section, and the gain bandwidth (δ e× Δλ eff) for 5D0 are computed and analysed. A radiative lifetime ranging from 789 to 984 µs points to a suitable material for orange-red fluorescent phosphors for lighting and display technologies. The gain bandwidth (δ e× Δλ eff), which is dependent on the Eu3+ concentration, suggests the use of the CdMgZnO:xEu3+ nanocrystal material in fibre amplifiers, while the sample with x = 1.5%, which yields the largest emission cross-section (15.79 × 10−22 cm2), the highest gain bandwidth (28.8 × 10−28 cm3), and a high branching ratio (71%), is the best candidate for red laser applications.

Mesoporous zirconia surfaces with anti-biofilm properties for dental implants

Cytocompatible bioactive surface treatments conferring antibacterial properties to osseointegrated dental implants are highly requested to prevent bacteria-related peri-implantitis. Here we focus on a newly designed family of mesoporous coatings based on zirconia (ZrO2) microstructure doped with gallium (Ga), exploiting its antibacterial and pro-osseo-integrative properties. The ZrO2 films were obtained via sol–gel synthesis route using Pluronic F127 as templating agent, while Ga doping was gained by introducing gallium nitrate hydrate. Chemical characterization by means of x-ray photoelectron spectroscopy and glow discharge optical emission spectroscopy confirmed the effective incorporation of Ga. Then, coatings morphological and structural analysis were carried out by transmission electron microscopy and selected area electron diffraction unveiling an effective stabilization of both the mesoporous structure and the tetragonal ZrO2 phase. Specimens’ cytocompatibility was confirmed towards gingival fibroblast and osteoblasts progenitors cultivated directly onto the coatings showing comparable metabolic activity and morphology in respect to controls cultivated on polystyrene. The presence of Ga significantly reduced the metabolic activity of the adhered oral pathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans in comparison to untreated bulk zirconia (p < 0.05); on the opposite, Ga ions did not significantly reduce the metabolism of the oral commensal Streptococcus salivarius (p > 0.05) thus suggesting for a selective anti-pathogens activity. Finally, the coatings’ ability to preserve cells from bacterial infection was proved in a co-culture method where cells and bacteria were cultivated in the same environment: the presence of Ga determined a significant reduction of the bacteria viability while allowing at the same time for cells proliferation. In conclusion, the here developed coatings not only demonstrated to satisfy the requested antibacterial and cytocompatibility properties, but also being promising candidates for the improvement of implantable devices in the field of implant dentistry.

Facile synthesis of ZnO–CoMoO4 nanocomposite using bio-organic fuel for energy storage application

Supercapacitors are the highly investigated energy storage devices to solve the global energy storage problems. The metal oxide nanomaterials as electrode-active materials yield the desirable specific capacitance. However, the higher economic and environmental costs associated with the synthesis of nanomaterials limit their extensive implication in supercapacitors. In this work, the ternary metal oxides nanocomposite of zinc, cobalt, and molybdenum was synthesized by green, economic and simple sol–gel synthesis route using the extracted fuel of E. cognata and the precursors salts. The as-synthesized ZnO–CoMoO4 nanocomposite was investigated as supercapacitor electrode candidate. A notable capacitance of 294.7 F/g was obtained for ZnO–CoMoO4 electrode. The specific energy density of ~ 8 Wh/Kg was found from charge–discharge measurements. The ZnO–CoMoO4 nanocomposite displayed almost 100% Coulombic efficiency over 10,000 cycles of repeated charge–discharge testing indicating its excellent stability. The lower Ri of 0.8 Ω was observed in the current study demonstrating the lower resistance. Consequently, the nano-scaled and phyto-fueled ternary composites of ZnO–CoMoO4 exhibited enhanced electrochemical properties toward supercapacitor without stability.

Elaboration and characterization of new glasses with high chemical durability in the system (70-x)TiO2-xNiO-30P2O5

ABSTRACT The aim of the present paper is to develop of a new sol–gel synthesis route for production of phosphate-based glasses in TiO2-NiO-P2O5 systems. The structure of the prepared glasses was investigated by ICP-AES, density methods, FTIR and RAMAN spectroscopy, XRD, 31P MAS-NMR and DSC, that confirmed successful synthesis and production of phosphate-based glasses. Glasses in the TiO2- NiO- P2O5 system with a high TiO2 and NiO content of up to 12.5 mol% were synthesized in this study. XRD analysis confirms that all glass specimens with nickel are amorphous. Investigation of ternary glasses with the general formula of (70-x)TiO2-xNiO-30P2O5, whit x = 0, 2.5, 5, 7.5, 10 or 12.5 where revealed, substituting Nickel in place of titanium significantly extend the stability and prolongs the lifetime of these glasses, which opens else numerous of potential applications.

Fabrication of bismuth silicate Bi2SiO5 ceramics as a potential high-temperature dielectric material

Bismuth silicate Bi2SiO5 (BSO) is known as an interesting new type of ferroelectric oxide; however, bulk ceramics of BSO have never been obtained because it easily decomposes at high temperature. In this study, we fabricated BSO ceramics for the first time using a sol–gel technique and investigated their potential as a dielectric material for high-temperature capacitor applications. A precursor powder was prepared by a sol–gel synthesis route using tetraethyl orthosilicate and bismuth nitrate pentahydrate as raw materials and then sintered under a small uniaxial pressure of 5 MPa with an addition of CH3COOLi as a sintering aid. A BSO ceramic with the highest relative density of 88.5% was obtained at a very low sintering temperature of 620 °C with preventing significant thermal decomposition. A crystal structure analysis revealed that the obtained BSO ceramic belongs to the ferroelectric monoclinic phase. The dielectric permittivity of the ceramic showed a superior temperature stability (± 5%) at temperatures up to 200 °C, followed by a sharp peak attributed to the ferroelectric–paraelectric phase transition at around 390 °C. The BSO ceramic also showed slim and pinched polarization hysteresis loops due to the random grain orientation and domain wall clamping, leading to a high energy storage efficiency over 75% at temperatures up to 100 °C.

Sol-Gel Entrapped Lewis Acids as Catalysts for Biodiesel Production.

Replacing fossil fuels with biodiesel enables the emission of greenhouse gases to be decreased and reduces dependence on fossil fuels in countries with poor natural resources. Biodiesel can be produced by an esterification reaction between free fatty acids (FFAs) and methanol or by transesterification of triglycerides from oils. Both reactions require homogeneous or heterogeneous catalysis. Production of biodiesel catalyzed by heterogeneous catalysts seems to be the preferred route, enabling easy product separation. As we have previously shown, the Lewis acids AlCl3 and BF3 can serve as highly efficient catalysts under ultrasonic activation. The present study focused on the development of oleic acid (OA) esterification with methanol by the same catalysts immobilized in silica matrices using the sol–gel synthesis route. During the course of immobilization, AlCl3 converts to AlCl3 × 6H2O (aluminite) and BF3 is hydrolyzed with the production of B2O3. The immobilized catalysts can be reused or involved in a continuous process. The possibility of biodiesel production using immobilized catalysts under ultrasonic activation is shown for the conversion of FFAs into biodiesel in batch and continuous mode.

Investigation of the Inorganic Compounds NaMV2(PO4)3 (M = Fe, Co, Ni) as Anode Materials for Sodium-Ion Batteries.

The new compounds NaMV2(PO4)3 (M = Fe, Co, Ni) were synthesized via a sol–gel synthesis route, and their crystal structures were refined using the Rietveld method from X-ray powder diffraction data. NaCoV2(PO4)3 was also characterized by TGA, cyclic voltammetry, and galvanostatic cycling. The three phases crystallize with the orthorhombic symmetry and the space group Imma. The structures are isotypic to the stuffed α-CrPO4-type structure and contain two vacant sites in which two sodium atoms can be intercalated. When NaCoV2(PO4)3 is cycled at a 1C rate in the voltage ranges of 0.1–3 and 0.7–3 V vs Na+/Na, it delivers specific capacities of 190 and 75 mA h/g, respectively, with an average operation potential of ∼1.4 V. This attests to the electrochemical activity of this compound and indicates that the α-CrPO4-type compounds could be suitable for hosting other guest ions.

Synthesis and characterization of NiFe2O4 ferrite: Sol–gel and hydrothermal synthesis routes effect on magnetic, structural and dielectric characteristics

In the present study, hydrothermal and sol–gel routes were adopted to prepare NiFe2O4 (nickel ferrite) using nickel nitrate and ferric nitrate. The magnetic, structural and dielectric characteristics of NiFe2O4 were compared both for hydrothermal and sol–gel synthesis routes. The NiFe2O4 were characterized by Scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), X-ray Powder Diffraction (XRD), vibrating-sample magnetometer (VSM) and impedance analyzer techniques for the confirmation of morphology, crystallinity, magnetic behavior and dielectric properties of the NiFe2O4. Results revealed that the synthesis route affected the structural, magnetic and dielectric properties of NiFe2O4. The NiFe2O4 showed inverse spinel structure as confirmed from XRD data and crystalline size was 29.39 nm for hydrothermal method, whereas sol-gel route furnished 52.16 nm crystalline size. Prepared NiFe2O4 showed different responses of saturation magnetization (MS) and retentivity (Mr) and coercivity (HC) along with the dielectric properties.

Highly efficient and visible light–driven nickel–doped vanadium oxide photocatalyst for degradation of Rhodamine B Dye

Water pollution has become serious threat for environment and society. Due to failure of different methods, semiconductor photocatalyst based advance oxidation process has attracted a huge interest for wastewater treatment. In this work, Nickel-doped vanadium pentaoxide (Ni doped-V2O5) is synthesized using easy and facile sol–gel synthesis route and the synthesized material is characterized through various characterization tools. The orthorhombic phase was detected in which decrease in crystallite size is observed with addition of dopant. The SEM analysis revealed that layered structure is formed with sufficient surface area and Energy Dispersive X-ray spectroscopy (EDX) represented the purity of samples. UV–Vis and Photoluminescence spectroscopies provide the information about the absorption and band gap of material and confirm the visible light response of the prepared catalysts. The photodegradation of RhB was evaluated through employing Ni doped-V2O5 photocatalyst which exhibited the 100% dye removal and high photostability. The factors which can affect the performance of catalytic activity are also studied to optimize the parameters for maximum dye removal. The kinetic study was also performed which showed that the synthesized materials follows pseudo first order kinetics.

Photocatalytic Degradation of Organic Dye by Sol–Gel-Synthesized CaCu3Ti4O12 Powder

Ultraviolet light-activated calcium copper titanate (CaCu3Ti4O12—abbreviated as CCTO) powder was successfully synthesized by a sol–gel synthesis route and characterized by different measurement techniques. The cubic crystalline structure of CCTO powder was verified by x-ray diffraction. The average particle size of the CCTO was found to be 109.3 ± 2.3 nm by field emission scanning electron microscopy which is in agreement with transmission electron microscopy analysis. The bandgap energy was assessed by optical reflectance spectroscopy and found to be 3.01 eV. The photocatalytic degradation of the CCTO powder was investigated under ultraviolet (UV) light illumination using rhodamine B (RhB) as a model organic pollutant. The RhB dye was degraded 52% within 40 min of UV irradiation. This proved the high photocatalytic performance of CCTO powder. This study shows that CCTO is a promising photocatalyst for wastewater treatment applications.

Functionalization of MoO3NiMoO4 nanocomposite using organic template for energy storage application

Abstract Over the recent times, sustainable advances in the metal oxides nanomaterials to develop effective and efficient supercapacitor electrode is critically investigated. In this regard, we have tailored the surface chemistry and nano scaled morphology of MoO3 NiMoO4 nanocomposite via organic functional groups of E. cognata and scrutinized it as an electrode for supercapacitor. MoO3 NiMoO4 nanocomposite was synthesized by the sol gel synthesis route using bioactive compounds of E. cognata. The phase formation of nanocomposite was confirmed by X-ray diffraction and energy dispersive spectroscopy while the morphology was examined by field emission scanning electron microscopy. The organic functional groups were revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, Gas chromatography–mass Spectroscopy (GC–MS) affirmed the presences of organic compounds in the synthesized nanocomposite. The optical band gap energy of functionalized MoO3 NiMoO4 was 3.34 eV, demonstrated by Tauc plot. The organic framework derived MoO3 NiMoO4 revealed specific capacitance of 204 Fg−1 and maximum energy density of 9.4 Wh kg−1, calculated by galvanostatic charge-discharge measurements. Consequently, the nano-scale and organic species of E. cognata were found to enhance the electrochemical behavior of MoO3 NiMoO4 electrode towards supercapacitor.

Structural, optical and magnetic properties of Sm3+ doped yttrium orthoferrite (YFeO3) obtained by sol–gel synthesis route

Fine powders of Y1−xSmxFeO3 (x = 0, 0.05, 0.10, 0.15) were synthesized via citrate based sol–gel route. While the as synthesized powders were amorphous, the calcined (900 °C/8 h) powders were confirmed to be polycrystalline by x-ray powder diffraction (XRD) studies. The calcined powders were found to crystallize in an orthorhombic structure associated with the lattice parameters a = 5.59 Å, b = 7.60 Å, c = 5.28 Å. These lattice parameters increased with the increase in Sm3+ content at yttrium sites. The strain that was obtained by the Williamson–Hall method increased with the increase in dopant (Sm3+) concentration vis-à-vis a decrease in crystallite size. Diffuse reflectance spectroscopic studies suggest an increase in band gap as Sm doping level increased. Significant enhancement in magnetization associated with a decrease in coercive field accompanied by a transition from anti-ferromagnetic to soft ferromagnetic behaviour in Sm doped YFeO3 were encountered. It is hoped that these materials with the enhanced magnetic properties could be of potential use for multifarious applications.

Improved electrochemical properties of the Li3V2(PO4)3 cathode material synthesized from a V(III) precursor

The choice of precursors can significantly influence the properties of synthesized materials. Here, we describe the effect of two different valence states of vanadium precursors, i.e., V(III) and V(IV), on the electrochemical properties of the resulting Li3V2(PO4)3/C composite synthesized through a sol−gel route. To obtain a homogeneous V(III) solution compatible with the aqueous sol−gel synthesis route, we used a facile and straightfoward electrolysis method to reduce V(IV) into V(III) in the oxalate solution. After the sol−gel and sintering processes, the resulting Li3V2(PO4)3/C composite synthesized from V(III) presents higher specific capacity and better cycle performance at different charging/discharging rates, compared with the composite prepared from V(IV). The improved electrochemical performance of the former is likely due to the more straightforward phase formation process for V(III) than V(IV) precursor in the synthesis.

Chlorogenic acid/PEG-based organic-inorganic hybrids: A versatile sol-gel synthesis route for new bioactive materials

New organic-inorganic hybrid materials were synthesized by an acid catalysed sol-gel approach, using silicon alkoxide and low molecular weight polyethylene glycol (PEG400) as inorganic and organic precursor, respectively. Chlorogenic acid (CGA), an antioxidant natural phenol compound, enriched further the organic component. Hybrids synthesized, all identical in terms of their starting materials, but differing in terms of their relative proportions, were characterized by means of Fourier Transform InfraRed (FTIR) measurements, UV–Vis spectroscopy, and UHPLC-HRMS analysis. The preservation of the intrinsic chlorogenic acid ability to scavenge, in a dose-dependent manner, radical species was investigated by directly exposing the hybrids to DPPH radical and ABTS radical cation. The relative ratio of both the natural compound and PEG heavily affected the antiradical response, suggesting that chemical interactions in the established network were able, based on components' ratio, to differently mask and/or display the CGA moieties, commonly deemed relevant for antioxidant power exerting. Cell culture MTT assay was used to assess the biocompatibility of hybrid materials towards fibroblast NIH-3 T3 cells and neuroblastoma SH-SY5Y cells. Cells tested appeared differently responsive. In particular, a marked cell viability increase was observed when hybrids with low PEG amount (6%) and high CGA (15%) were directly exposed to fibroblast cells, whose mitochondrial redox activity was negatively affected by hybrid synthesized using the highest organic component rate (both PEG and CGA). Cell viability and morphology of human neuroblastoma SH-SY5Y cells were broadly compromised regardless of organic/inorganic starting materials ratio, suggesting the ability of hybrids to exert pro-oxidant effect towards tumour cells and to selectively interfere with their growth. The hybrids, able to elicit cleverly anti- or proliferative effects, were also shown to be bioactive. In fact, a biologically active hydroxyapatite layer was observed to be formed on the surface of the smart synthesized materials. This feature, which makes them a valuable bonding interface with tissues, opens new scenario aiming at further investigating the employment of natural phenol compounds in versatile sol–gel synthesis routes.